app.py

"""
AI Study Helper — Professional Edition v5.0
B.Tech CSE AI Learning Assistant

Fixes applied vs previous versions:
  - Model: Only meta-llama/Llama-3.1-8B-Instruct is used (Mistral variants
    are NOT supported by the HF free-tier chat router for this token).
  - PDF: Rewrote using fpdf2 modern API (new_x/new_y instead of ln=True).
    All cell text is ASCII-safe to prevent "horizontal space" errors.
  - Quiz: Fully interactive — 5 pre-created Radio slots, Submit button,
    per-question correct/wrong feedback + score.
  - History: DataFrame display + Clear button that actually deletes the file.
  - Dropdowns: All use gr.Dropdown with interactive=True and allow_custom_value=False.

Security:
  - HF_TOKEN loaded from .env only.
  - Server bound to 127.0.0.1.
  - All dropdown inputs validated against allow-lists.
  - Free-text inputs length-capped.
  - File content truncated before LLM.
  - Generic error messages to users; full detail logged server-side.
  - TODO(security): Add auth gate before public deployment.
  - TODO(security): Rate-limit generation endpoints.
"""

import json
import logging
import os
import re
from datetime import datetime
from pathlib import Path

import gradio as gr
from dotenv import load_dotenv
from fpdf import FPDF
from fpdf.enums import XPos, YPos
from huggingface_hub import InferenceClient

try:
    from pypdf import PdfReader
    _PDF_OK = True
except ImportError:
    _PDF_OK = False

# ── Logging ───────────────────────────────────────────────────────────────────
logging.basicConfig(
    level=logging.INFO,
    format="%(asctime)s [%(levelname)s] %(message)s",
)
logger = logging.getLogger(__name__)

# ── Env & Client ──────────────────────────────────────────────────────────────
load_dotenv()
_hf_token = os.getenv("HF_TOKEN")
if not _hf_token:
    raise EnvironmentError(
        "HF_TOKEN not set.\n"
        "Add it to your .env file → https://huggingface.co/settings/tokens"
    )

client = InferenceClient(api_key=_hf_token)

# Model: Llama-3.1-8B-Instruct via HF chat.completions (confirmed working)
_MODEL_PRIMARY  = "meta-llama/Llama-3.1-8B-Instruct"


def _llm(prompt: str, max_tokens: int = 2048) -> str:
    """Call Llama-3.1-8B via HF chat.completions."""
    try:
        resp = client.chat.completions.create(
            model=_MODEL_PRIMARY,
            messages=[{"role": "user", "content": prompt}],
            max_tokens=max_tokens,
            temperature=0.7,
        )
        result = resp.choices[0].message.content
        if result and len(result.strip()) > 20:
            logger.info("Model used: %s", _MODEL_PRIMARY)
            return result.strip()
    except Exception as exc:
        logger.error("LLM call failed: %s", exc)

    return (
        "[ERROR] AI is temporarily unavailable.\n\n"
        "**Check:** HF_TOKEN has Read access at https://huggingface.co/settings/tokens"
    )


# ── History ───────────────────────────────────────────────────────────────────
_HIST_FILE = Path("study_history.json")
_MAX_HIST  = 50


def _load_hist() -> list[dict]:
    if _HIST_FILE.exists():
        try:
            return json.loads(_HIST_FILE.read_text(encoding="utf-8"))
        except Exception:
            return []
    return []


def _add_hist(entry: dict) -> None:
    hist = _load_hist()
    hist.insert(0, entry)
    try:
        _HIST_FILE.write_text(
            json.dumps(hist[:_MAX_HIST], indent=2, ensure_ascii=False),
            encoding="utf-8",
        )
    except Exception as exc:
        logger.error("History save: %s", exc)


# ── Topics catalogue ──────────────────────────────────────────────────────────
TOPICS: dict[str, list[str]] = {
    "Programming":          ["Python", "Java", "C", "C++", "OOP Concepts",
                             "Exception Handling", "Recursion"],
    "Data Structures":      ["Arrays", "Linked List", "Stack", "Queue",
                             "Trees", "Graphs", "Hash Tables", "Heaps"],
    "Algorithms":           ["Sorting Algorithms", "Searching Algorithms",
                             "Dynamic Programming", "Greedy Algorithms",
                             "Divide & Conquer", "Graph Algorithms",
                             "Complexity Analysis"],
    "Operating Systems":    ["Processes & Threads", "Memory Management",
                             "File Systems", "CPU Scheduling",
                             "Deadlocks", "Virtual Memory", "Synchronization"],
    "DBMS":                 ["Relational Model", "SQL Queries", "Normalization",
                             "Transactions & ACID", "Indexing & Hashing",
                             "ER Diagrams", "NoSQL Databases"],
    "Computer Networks":    ["OSI Model", "TCP/IP Protocol", "HTTP & HTTPS",
                             "DNS & DHCP", "Routing Algorithms",
                             "Socket Programming", "Network Security"],
    "Artificial Intelligence": ["Search Algorithms", "Knowledge Representation",
                                "Expert Systems", "Game Theory",
                                "Planning", "Uncertainty & Probability"],
    "Machine Learning":     ["Linear Regression", "Decision Trees", "SVM",
                             "Neural Networks", "Clustering Algorithms",
                             "Ensemble Methods", "Feature Engineering"],
    "Deep Learning":        ["Neural Networks Basics", "CNNs", "RNNs & LSTMs",
                             "Transformers", "GANs", "Transfer Learning",
                             "Backpropagation"],
    "Web Development":      ["HTML & CSS", "JavaScript", "React",
                             "Node.js & Express", "REST APIs",
                             "Database Integration", "Authentication & JWT"],
    "Cloud Computing":      ["AWS Core Services", "Azure Fundamentals",
                             "Docker & Containers", "Kubernetes",
                             "Serverless Architecture", "Microservices",
                             "Cloud Security"],
    "Cyber Security":       ["Cryptography", "Network Security",
                             "Web Security", "Ethical Hacking",
                             "Blockchain", "Firewalls & IDS",
                             "Penetration Testing"],
}

_VALID_CATS   = set(TOPICS.keys())
_VALID_TOPICS = {t for ts in TOPICS.values() for t in ts}
_VALID_LEVELS = {"Beginner", "Intermediate", "Advanced", "Easy"}
_LEVEL_CLEAN = {
    "Easy":         "Beginner",
    "Beginner":     "Beginner",
    "Intermediate": "Intermediate",
    "Advanced":     "Advanced",
}
_VALID_MODES  = {
    "Learn Concept",
    "Semester Exam Prep",
    "Interview Preparation",
    "Quick Revision",
}

_FIRST_CAT    = next(iter(TOPICS))
_FIRST_TOPICS = TOPICS[_FIRST_CAT]


def update_topics(category: str) -> gr.Dropdown:
    """Refresh topic dropdown when category changes."""
    if category not in _VALID_CATS:
        category = _FIRST_CAT
    choices = TOPICS[category]
    return gr.Dropdown(choices=choices, value=choices[0], interactive=True)


# ══════════════════════════════════════════════════════════════════════════════
# AI Generation Functions
# ══════════════════════════════════════════════════════════════════════════════

def generate_notes(category: str, topic: str, level: str, mode: str) -> str:
    """Tab 1 — structured study notes."""
    if category not in _VALID_CATS:   return "âš ï¸ Select a valid subject."
    if topic not in _VALID_TOPICS:    return "âš ï¸ Select a valid topic."
    if level not in _VALID_LEVELS:    return "âš ï¸ Select a valid difficulty."
    if mode not in _VALID_MODES:      return "âš ï¸ Select a valid study mode."
    clean_level = _LEVEL_CLEAN.get(level, level)

    prompt = f"""You are an expert B.Tech CSE professor.

Create detailed study notes for: {category} - {topic}
Level: {clean_level} | Mode: {mode}

Structure your response with these headings:

## Explanation
Clear explanation suitable for {level} level.

## Key Concepts
6-8 essential concepts as bullet points.

## How It Works
Step-by-step mechanism.

## Real-Life Examples
2-3 practical, relatable examples.

## Code Example
Working code snippet with comments (if applicable).

## Exam Points
Most important facts for semester exams.

## Interview Q&A
5 interview questions with concise answers.

## Common Mistakes
3-5 errors students make and how to avoid them.

## Summary
4-5 line recap for quick revision."""

    result = _llm(prompt)
    _add_hist({"timestamp": datetime.now().strftime("%Y-%m-%d %H:%M"),
               "tab": "Learn", "topic": topic, "category": category,
               "mode": mode, "level": level})
    return result


def generate_revision(topic: str) -> str:
    """Tab 2 — last-minute revision notes."""
    topic = topic.strip()
    if not topic:        return "âš ï¸ Please enter a topic."
    if len(topic) > 300: return "âš ï¸ Topic is too long (max 300 chars)."

    prompt = f"""Create concise last-minute revision notes for B.Tech CSE exam on: {topic}

## Quick Revision: {topic}

### Must-Know Points
8-10 critical bullet points.

### Formulas / Syntax / Key Commands
Essential formulas or syntax to memorise.

### Memory Tricks
Mnemonics and shortcuts.

### Exam Checklist
Critical items to verify before the exam.

### 30-Second Summary
3-4 key lines — the absolute essence."""

    result = _llm(prompt, max_tokens=1024)
    _add_hist({"timestamp": datetime.now().strftime("%Y-%m-%d %H:%M"),
               "tab": "Revision", "topic": topic})
    return result


# ── Quiz helpers ──────────────────────────────────────────────────────────────

def _parse_quiz(text: str) -> list[dict]:
    """Extract quiz JSON from LLM output (handles various formats)."""
    # Remove markdown fences
    clean = re.sub(r"```(?:json)?", "", text).strip().rstrip("`").strip()

    # Attempt direct parse
    for candidate in (clean, text.strip()):
        try:
            data = json.loads(candidate)
            if isinstance(data, list) and len(data) >= 3:
                return data
            if isinstance(data, dict):
                for key in ("questions", "quiz", "mcqs", "items"):
                    if key in data and isinstance(data[key], list):
                        return data[key]
        except Exception:
            pass

    # Find embedded JSON array
    for m in re.finditer(r"\[\s*\{.*?\}\s*\]", text, re.DOTALL):
        try:
            data = json.loads(m.group())
            if isinstance(data, list) and len(data) >= 3:
                return data
        except Exception:
            pass

    return []


def _quiz_error(msg: str) -> list:
    """Return a consistent error state for all 19 quiz outputs."""
    empties = []
    for _ in range(5):
        empties += [
            gr.update(visible=False),
            gr.update(value=""),
            gr.update(choices=[], value=None, visible=False),
        ]
    return [[], msg] + empties + [gr.update(visible=False), gr.update(visible=False)]


def generate_quiz_fn(category: str, topic: str, level: str) -> list:
    """
    Tab 3 — generate 5 MCQ questions.

    Returns 19 updates:
      quiz_state, status_md,
      [group, question_md, radio] × 5,
      submit_btn, results_group
    """
    if (category not in _VALID_CATS
            or topic not in _VALID_TOPICS
            or level not in _VALID_LEVELS):
        return _quiz_error("âš ï¸ Please select valid options before generating.")

    clean_level = _LEVEL_CLEAN.get(level, level)

    prompt = f"""Generate exactly 5 multiple choice questions about "{topic}" ({category}) for {clean_level} B.Tech CSE students.

Reply with ONLY a valid JSON array — no introduction, no markdown, no text outside the array.

[
  {{
    "question": "Full question text?",
    "options": ["A) First option", "B) Second option", "C) Third option", "D) Fourth option"],
    "correct": "A",
    "explanation": "One or two sentences explaining why A is correct."
  }},
  {{...}},
  {{...}},
  {{...}},
  {{...}}
]

Rules:
- Exactly 5 questions
- Each has exactly 4 options labelled A), B), C), D)
- "correct" is a single letter: A, B, C, or D
- Return ONLY the JSON array"""

    raw = _llm(prompt, max_tokens=2000)
    questions = _parse_quiz(raw)

    if len(questions) < 3:
        return _quiz_error(
            "⌠Could not parse quiz from AI response. Please try again.\n\n"
            f"*Raw output (debug):*\n```\n{raw[:400]}\n```"
        )

    # Normalise to exactly 5 questions
    while len(questions) < 5:
        questions.append(questions[-1])
    questions = questions[:5]

    status = (
        f"✅ **Quiz ready!** Answer all 5 questions then click **Submit Quiz**."
    )
    updates = [questions, status]

    for i, q in enumerate(questions):
        opts = [str(o) for o in q.get("options", [])[:4]]
        while len(opts) < 4:
            opts.append(f"{'ABCD'[len(opts)]}) Option")
        updates += [
            gr.update(visible=True),
            gr.update(value=f"### Q{i + 1}. {q.get('question', '')}"),
            gr.update(choices=opts, value=None, visible=True, interactive=True),
        ]

    updates += [gr.update(visible=True), gr.update(visible=False)]

    _add_hist({"timestamp": datetime.now().strftime("%Y-%m-%d %H:%M"),
               "tab": "Quiz", "topic": topic,
               "category": category, "level": level})
    return updates


def check_quiz_fn(quiz_data: list, a1, a2, a3, a4, a5) -> tuple:
    """Tab 3 — check answers and show results."""
    if not quiz_data:
        return gr.update(visible=False), "âš ï¸ No quiz loaded. Generate a quiz first.", ""

    answers = [a1, a2, a3, a4, a5]
    score = 0
    blocks = []

    for i, q in enumerate(quiz_data):
        correct_letter = str(q.get("correct", "A")).strip().upper()
        user_ans = answers[i] if i < len(answers) else None
        opts = q.get("options", [])

        if user_ans is None:
            is_correct = False
            user_display = "*(not answered)*"
        else:
            user_letter = str(user_ans).strip()[0].upper()
            is_correct = user_letter == correct_letter
            user_display = str(user_ans)

        if is_correct:
            score += 1

        correct_text = next(
            (o for o in opts if str(o).startswith(correct_letter + ")")),
            f"{correct_letter}) (see study notes)",
        )
        verdict = "✅ Correct!" if is_correct else "⌠Wrong"

        blocks.append(
            f"---\n"
            f"**Q{i + 1}.** {q.get('question', '')}\n\n"
            f"Your answer: **{user_display}**\n\n"
            f"**{verdict}**\n\n"
            f"Correct answer: **{correct_text}**\n\n"
            f"*{q.get('explanation', '')}*\n"
        )

    pct = round(score / max(len(quiz_data), 1) * 100)
    grade = ("🆠Excellent!" if pct >= 80
             else "👠Good job!" if pct >= 60
             else "📚 Keep studying!")
    score_md = f"## Score: {score}/{len(quiz_data)} ({pct}%)  —  {grade}"
    results_md = "## Quiz Results\n\n" + "\n".join(blocks)

    return gr.update(visible=True), results_md, score_md


def generate_interview(category: str, topic: str) -> str:
    """Tab 4 — placement interview preparation."""
    if category not in _VALID_CATS or topic not in _VALID_TOPICS:
        return "âš ï¸ Please select valid options."

    prompt = f"""Prepare complete B.Tech CSE placement interview material for: {category} - {topic}

## Technical Interview Questions

### Basic Level — Q1 to Q5 with detailed answers

### Intermediate Level — Q6 to Q10 with detailed answers

### Advanced / Tricky — Q11 to Q13 with detailed answers

## Coding Problems
2-3 commonly asked problems with approach and hints.

## HR / Behavioral Questions
4-5 behavioral questions with sample answers.

## Interview Tips
Key things top interviewers look for on this topic."""

    result = _llm(prompt)
    _add_hist({"timestamp": datetime.now().strftime("%Y-%m-%d %H:%M"),
               "tab": "Interview", "topic": topic, "category": category})
    return result


def analyze_upload(file) -> str:
    """Tab 5 — summarise uploaded PDF/TXT notes."""
    if file is None:
        return "âš ï¸ Please upload a PDF or TXT file."
    fp = Path(file.name)
    text = ""
    try:
        if fp.suffix.lower() == ".txt":
            text = fp.read_text(encoding="utf-8", errors="replace")
        elif fp.suffix.lower() == ".pdf":
            if not _PDF_OK:
                return "âš ï¸ pypdf not installed. Run: pip install pypdf"
            reader = PdfReader(str(fp))
            for page in reader.pages:
                t = page.extract_text()
                if t:
                    text += t + "\n"
        else:
            return "âš ï¸ Unsupported format — upload a .pdf or .txt file."
    except Exception as exc:
        logger.error("File read: %s", exc)
        return "⌠Could not read the file."

    if not text.strip():
        return "âš ï¸ No text extracted. The PDF may be image/scanned-based."

    prompt = f"""A B.Tech CSE student uploaded their notes. Create a study guide.

---NOTES START---
{text.strip()[:4000]}
---NOTES END---

## Simple Summary
Student-friendly explanation of what these notes cover.

## Key Points
12-15 most important takeaways as bullets.

## Exam Notes
Most likely exam topics from this content.

## Practice Questions
6 questions with brief answers based on this material.

## Extra Insights
Additional context that aids understanding."""

    result = _llm(prompt)
    _add_hist({"timestamp": datetime.now().strftime("%Y-%m-%d %H:%M"),
               "tab": "Upload", "topic": fp.name})
    return result


# ── History functions ─────────────────────────────────────────────────────────

def get_history_data() -> list[list]:
    """Return history as a list of rows for gr.DataFrame."""
    entries = _load_hist()
    if not entries:
        return []
    rows = []
    for i, e in enumerate(entries, 1):
        topic  = e.get("topic") or e.get("filename", "—")
        extras = " . ".join(filter(None, [e.get("mode", ""), e.get("level", "")]))
        rows.append([i, e.get("timestamp", "—"), e.get("tab", "—"),
                     topic, extras or "—"])
    return rows


def clear_history_fn() -> tuple:
    """Delete history file and return empty table + status message."""
    try:
        if _HIST_FILE.exists():
            _HIST_FILE.unlink()
        logger.info("History cleared.")
        return [], "✅ History cleared successfully!"
    except Exception as exc:
        logger.error("History clear: %s", exc)
        return gr.update(), f"⌠Could not clear history: {exc}"


# ── PDF generation ────────────────────────────────────────────────────────────

def _safe(text: str) -> str:
    """Encode to latin-1 safely — replaces unsupported unicode chars."""
    return str(text).encode("latin-1", errors="replace").decode("latin-1")


def _strip_md(text: str) -> str:
    """Remove markdown symbols that confuse plain-text PDF rendering."""
    t = re.sub(r'\*{1,3}(.*?)\*{1,3}', r'\1', text)   # bold/italic
    t = re.sub(r'`{1,3}(.*?)`{1,3}', r'\1', t)         # code
    t = re.sub(r'^#{1,6}\s+', '', t, flags=re.M)        # headings
    t = re.sub(r'\[(.*?)\]\(.*?\)', r'\1', t)           # links
    t = t.replace('\x01', '')                           # remove stray control chars
    return t


def _build_pdf(title: str, content: str, out_file: str,
               topic: str = "", generated_by: str = "") -> str | None:
    """
    Professional PDF export with proper text alignment and formatting.
    Returns absolute path or None on failure.
    """
    if not content or not content.strip():
        logger.warning("PDF skipped: empty content for '%s'", title)
        return None
    try:
        out_path = os.path.abspath(out_file)

        MARGIN    = 18          # mm left/right margin
        LINE_H    = 6.5         # body line height mm
        H1_H      = 10          # h1 line height
        H2_H      = 9           # h2 line height
        H3_H      = 7           # h3 line height

        pdf = FPDF()
        pdf.set_margins(MARGIN, MARGIN, MARGIN)
        pdf.set_auto_page_break(auto=True, margin=18)
        pdf.add_page()
        body_w = pdf.w - 2 * MARGIN   # usable text width

        # ── HEADER BAND ──────────────────────────────────────────────
        pdf.set_fill_color(78, 34, 180)
        pdf.set_text_color(255, 255, 255)

        pdf.set_font("Helvetica", "B", 18)
        pdf.cell(body_w, 12, _safe("AI STUDY HELPER"),
                 fill=True, new_x=XPos.LMARGIN, new_y=YPos.NEXT, align="C")

        pdf.set_font("Helvetica", "B", 11)
        pdf.cell(body_w, 8, _safe(title),
                 fill=True, new_x=XPos.LMARGIN, new_y=YPos.NEXT, align="C")

        if topic:
            pdf.set_font("Helvetica", "", 9)
            pdf.cell(body_w, 6, _safe(f"Topic: {topic}"),
                     fill=True, new_x=XPos.LMARGIN, new_y=YPos.NEXT, align="C")

        pdf.set_font("Helvetica", "I", 8)
        pdf.set_text_color(220, 210, 255)
        pdf.cell(body_w, 6,
                 _safe(f"Generated: {datetime.now().strftime('%d %b %Y at %H:%M')}"),
                 fill=True, new_x=XPos.LMARGIN, new_y=YPos.NEXT, align="C")

        pdf.ln(8)

        # ── BODY ─────────────────────────────────────────────────────
        # Sanitise: encode to latin-1 (FPDF built-in encoding), replace unknowns
        safe_content = content.encode("latin-1", errors="replace").decode("latin-1")

        # Track list indent state
        in_code_block = False

        for raw_line in safe_content.splitlines():
            stripped = raw_line.strip()

            # Code fence toggle — render as mono grey block
            if stripped.startswith("```"):
                in_code_block = not in_code_block
                if in_code_block:
                    pdf.ln(2)
                    pdf.set_fill_color(240, 240, 248)
                else:
                    pdf.set_fill_color(255, 255, 255)
                    pdf.ln(2)
                continue

            if in_code_block:
                pdf.set_font("Courier", "", 9)
                pdf.set_text_color(60, 30, 100)
                pdf.set_fill_color(240, 240, 248)
                pdf.multi_cell(body_w, 5.5, raw_line.rstrip(), fill=True,
                               new_x=XPos.LMARGIN, new_y=YPos.NEXT, align="L")
                continue

            s = stripped

            if not s:
                pdf.ln(3)
                continue

            # ── H1  (# Title) ────────────────────────────────────────
            if s.startswith("# ") and not s.startswith("## "):
                text = s[2:].strip()
                pdf.ln(6)
                pdf.set_font("Helvetica", "B", 15)
                pdf.set_text_color(55, 20, 160)
                pdf.multi_cell(body_w, H1_H, _safe(text),
                               new_x=XPos.LMARGIN, new_y=YPos.NEXT, align="L")
                # Thin rule under H1
                y_now = pdf.get_y()
                pdf.set_draw_color(78, 34, 180)
                pdf.set_line_width(0.6)
                pdf.line(MARGIN, y_now + 1, MARGIN + body_w, y_now + 1)
                pdf.set_line_width(0.2)
                pdf.ln(5)
                pdf.set_text_color(35, 35, 50)

            # ── H2  (## Heading) ─────────────────────────────────────
            elif s.startswith("## ") and not s.startswith("### "):
                text = s[3:].strip()
                pdf.ln(5)
                # Left accent bar + coloured background
                pdf.set_fill_color(78, 34, 180)
                pdf.rect(MARGIN, pdf.get_y(), 3, H2_H, "F")   # left accent bar
                pdf.set_fill_color(235, 228, 255)
                pdf.rect(MARGIN + 3, pdf.get_y(), body_w - 3, H2_H, "F")
                pdf.set_font("Helvetica", "B", 12)
                pdf.set_text_color(55, 20, 140)
                # Position text after accent bar
                pdf.set_x(MARGIN + 6)
                pdf.cell(body_w - 6, H2_H, _safe(text),
                         new_x=XPos.LMARGIN, new_y=YPos.NEXT, align="L")
                pdf.ln(2)
                pdf.set_text_color(35, 35, 50)

            # ── H3  (### Sub-heading) ────────────────────────────────
            elif s.startswith("### "):
                text = s[4:].strip()
                pdf.ln(4)
                pdf.set_font("Helvetica", "B", 11)
                pdf.set_text_color(30, 110, 70)
                pdf.multi_cell(body_w, H3_H, _safe(text),
                               new_x=XPos.LMARGIN, new_y=YPos.NEXT, align="L")
                pdf.ln(1)
                pdf.set_text_color(35, 35, 50)

            # ── H4  (#### Sub-sub) ───────────────────────────────────
            elif s.startswith("#### "):
                text = s[5:].strip()
                pdf.ln(3)
                pdf.set_font("Helvetica", "B", 10)
                pdf.set_text_color(80, 40, 160)
                pdf.multi_cell(body_w, LINE_H, _safe(text),
                               new_x=XPos.LMARGIN, new_y=YPos.NEXT, align="L")
                pdf.set_text_color(35, 35, 50)

            # ── Bullet / numbered list ───────────────────────────────
            elif s.startswith(("- ", "* ", "+ ")) or re.match(r'^\d+\.\s', s):
                is_numbered = re.match(r'^(\d+)\.\s(.*)', s)
                if is_numbered:
                    bullet   = f"{is_numbered.group(1)}."
                    body_txt = is_numbered.group(2)
                else:
                    bullet   = "-"
                    body_txt = s[2:]

                bullet   = _safe(bullet.strip())
                body_txt = re.sub(r'\*{1,3}(.*?)\*{1,3}', r'\1', body_txt)
                body_txt = re.sub(r'`([^`]+)`', r'\1', body_txt)
                body_txt = _safe(body_txt)

                pdf.set_font("Helvetica", "B", 11)
                pdf.set_text_color(78, 34, 180)
                # Bullet symbol column (fixed 8 mm)
                pdf.set_x(MARGIN + 4)
                pdf.cell(8, LINE_H, bullet, new_x=XPos.RIGHT, new_y=YPos.TOP)

                # Body text — wraps within remaining width
                pdf.set_font("Helvetica", "", 11)
                pdf.set_text_color(35, 35, 50)
                text_w = body_w - 12
                pdf.multi_cell(text_w, LINE_H, body_txt,
                               new_x=XPos.LMARGIN, new_y=YPos.NEXT, align="L")

            # ── Horizontal rule ──────────────────────────────────────
            elif s.startswith("---") or s.startswith("***") or s.startswith("___"):
                pdf.ln(3)
                pdf.set_draw_color(180, 160, 220)
                pdf.set_line_width(0.4)
                pdf.line(MARGIN, pdf.get_y(), MARGIN + body_w, pdf.get_y())
                pdf.set_line_width(0.2)
                pdf.ln(4)

            # ── Normal paragraph text ────────────────────────────────
            else:
                pdf.set_font("Helvetica", "", 11)
                pdf.set_text_color(35, 35, 50)
                # Strip inline markdown formatting
                display = re.sub(r'\*{1,3}(.*?)\*{1,3}', r'\1', s)
                display = re.sub(r'`([^`]+)`', r'\1', display)
                display = _safe(display)
                pdf.multi_cell(body_w, LINE_H, display,
                               new_x=XPos.LMARGIN, new_y=YPos.NEXT, align="L")

        # ── PAGE FOOTER ───────────────────────────────────────────────
        pdf.set_y(-14)
        pdf.set_font("Helvetica", "I", 8)
        pdf.set_text_color(160, 155, 180)
        pdf.cell(body_w / 2, 6, "AI Study Helper  |  B.Tech CSE", align="L")
        pdf.cell(body_w / 2, 6, f"Page {pdf.page_no()}", align="R")

        pdf.output(out_path)
        logger.info("PDF saved: %s", out_path)
        return out_path

    except Exception as exc:
        logger.error("PDF build failed: %s", exc)
        return None


# One-liner PDF wrappers
def notes_pdf(c):     return _build_pdf("Study Notes",         c, "study_notes.pdf")
def revision_pdf(c):  return _build_pdf("Revision Notes",      c, "revision_notes.pdf")
def quiz_pdf(c):      return _build_pdf("Quiz Results",        c, "quiz_results.pdf")
def interview_pdf(c): return _build_pdf("Interview Prep Pack", c, "interview_prep.pdf")
def upload_pdf(c):    return _build_pdf("Notes AI Summary",    c, "notes_summary.pdf")


# ══════════════════════════════════════════════════════════════════════════════
# CSS — clean dark SaaS theme
# ══════════════════════════════════════════════════════════════════════════════

_CSS = """
@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700;800&display=swap');

/* ============================================================
   BASE RESET
   ============================================================ */
*, *::before, *::after { box-sizing: border-box; }

body, .gradio-container, .main {
    font-family: 'Inter', 'Segoe UI', system-ui, sans-serif !important;
    background: #0d0d1a !important;
    color: #d0d0e8 !important;
}

.gradio-container {
    background:
        radial-gradient(ellipse 65% 45% at 15% 8%, rgba(120,80,240,0.09) 0%, transparent 55%),
        radial-gradient(ellipse 55% 40% at 85% 88%, rgba(40,170,120,0.06) 0%, transparent 50%),
        #0d0d1a !important;
    max-width: 1200px !important;
    margin: 0 auto !important;
}

/* ============================================================
   TAB NAVIGATION
   ============================================================ */
.tabs > .tab-nav {
    background: rgba(255,255,255,0.022) !important;
    border-bottom: 1px solid rgba(120,80,240,0.18) !important;
    padding: 0 8px !important;
    display: flex !important;
    gap: 2px !important;
}

.tabs > .tab-nav > button {
    color: #6060a0 !important;
    font-weight: 600 !important;
    font-size: 13px !important;
    padding: 12px 18px !important;
    border: none !important;
    border-bottom: 3px solid transparent !important;
    background: transparent !important;
    border-radius: 0 !important;
    transition: color .2s, border-color .2s, background .2s !important;
    cursor: pointer !important;
    white-space: nowrap !important;
}

.tabs > .tab-nav > button:hover {
    color: #9070e0 !important;
    background: rgba(120,80,240,0.07) !important;
}

.tabs > .tab-nav > button.selected {
    color: #b090ff !important;
    border-bottom: 3px solid #7f5af0 !important;
    background: rgba(127,90,240,0.09) !important;
}

/* ============================================================
   PANELS
   ============================================================ */
.block, .gr-block, .gr-box, .panel, .gr-panel,
.form, .gr-form {
    background: rgba(255,255,255,0.025) !important;
    border: 1px solid rgba(255,255,255,0.06) !important;
    border-radius: 14px !important;
}

/* ============================================================
   LABELS
   ============================================================ */
label > span,
.label-wrap > span,
fieldset > legend,
.gr-form label > span {
    color: #8888bb !important;
    font-size: 11px !important;
    font-weight: 700 !important;
    letter-spacing: 0.8px !important;
    text-transform: uppercase !important;
}

/* ============================================================
   TEXT INPUTS
   ============================================================ */
input[type=text], textarea {
    background: rgba(8,8,22,0.90) !important;
    border: 1.5px solid rgba(120,80,240,0.25) !important;
    color: #e0e0f5 !important;
    border-radius: 10px !important;
    font-family: inherit !important;
    font-size: 14px !important;
    transition: border-color .2s, box-shadow .2s !important;
}

input[type=text]:focus, textarea:focus {
    border-color: rgba(127,90,240,0.65) !important;
    box-shadow: 0 0 0 3px rgba(127,90,240,0.12) !important;
    outline: none !important;
}

/* ============================================================
   RADIO BUTTONS — single-selection pill style
   Only ONE button highlighted at a time (browser-enforced by
   name= grouping; CSS :has() + .radio-selected JS class)
   ============================================================ */

.gr-radio fieldset,
.gr-radio legend {
    border: none !important;
    padding: 0 !important;
    margin: 0 !important;
    background: transparent !important;
}

/* Default pill */
.gr-radio label {
    display: inline-flex !important;
    align-items: center !important;
    gap: 8px !important;
    padding: 9px 20px !important;
    margin: 4px 5px 4px 0 !important;
    border: 2px solid rgba(120,80,240,0.28) !important;
    border-radius: 50px !important;
    background: rgba(15,10,35,0.80) !important;
    color: #a090cc !important;
    font-size: 14px !important;
    font-weight: 600 !important;
    cursor: pointer !important;
    transition: background .15s ease, border-color .15s ease,
                color .15s ease, transform .12s ease !important;
    user-select: none !important;
    white-space: nowrap !important;
}

/* Hover — never mistaken for selected */
.gr-radio label:hover {
    border-color: rgba(127,90,240,0.55) !important;
    background: rgba(60,30,120,0.22) !important;
    color: #d0c0f0 !important;
    transform: translateY(-1px) !important;
}

/* SELECTED — dark deep purple, clearly distinct, white text
   Strategy A: CSS :has() (Chrome 105+, Firefox 121+, Safari 15.4+) */
.gr-radio label:has(input[type="radio"]:checked) {
    background: #2d0a5c !important;
    border: 2px solid #9b6cf0 !important;
    color: #ffffff !important;
    font-weight: 700 !important;
    transform: none !important;
    box-shadow:
        inset 0 0 0 1px rgba(155,108,240,0.35),
        0 0 18px rgba(100,40,200,0.45) !important;
}

/* Strategy B: JS-injected class .radio-selected */
.gr-radio label.radio-selected {
    background: #2d0a5c !important;
    border: 2px solid #9b6cf0 !important;
    color: #ffffff !important;
    font-weight: 700 !important;
    transform: none !important;
    box-shadow:
        inset 0 0 0 1px rgba(155,108,240,0.35),
        0 0 18px rgba(100,40,200,0.45) !important;
}

/* Force all children of selected label to white */
.gr-radio label:has(input:checked) span,
.gr-radio label:has(input:checked) p,
.gr-radio label.radio-selected span,
.gr-radio label.radio-selected p {
    color: #ffffff !important;
}

/* Hide the native radio dot (the pill IS the selector) */
.gr-radio label input[type="radio"] {
    accent-color: #9b6cf0 !important;
    width: 14px !important;
    height: 14px !important;
    flex-shrink: 0 !important;
    cursor: pointer !important;
}

/* ============================================================
   DROPDOWNS
   ============================================================ */
.wrap,
[data-testid="dropdown"] > .wrap {
    background: rgba(10,8,28,0.92) !important;
    border: 1.5px solid rgba(120,80,240,0.28) !important;
    border-radius: 11px !important;
    min-height: 48px !important;
    display: flex !important;
    align-items: center !important;
    transition: border-color .2s, box-shadow .2s !important;
}

.wrap:focus-within {
    border-color: rgba(127,90,240,0.70) !important;
    box-shadow: 0 0 0 3px rgba(127,90,240,0.13) !important;
}

.wrap input {
    color: #ddd8ff !important;
    background: transparent !important;
    border: none !important;
    font-size: 14px !important;
    font-weight: 500 !important;
    padding: 13px 16px !important;
    cursor: pointer !important;
}

.wrap svg { color: #9b7ef8 !important; fill: #9b7ef8 !important; }

ul.options, .options {
    background: #0f0c24 !important;
    border: 1px solid rgba(127,90,240,0.40) !important;
    border-radius: 11px !important;
    box-shadow: 0 14px 44px rgba(0,0,0,0.65) !important;
    z-index: 9999 !important;
    padding: 6px !important;
    margin-top: 5px !important;
    max-height: 260px !important;
    overflow-y: auto !important;
}

ul.options li, .options li {
    color: #c4c0ee !important;
    background: transparent !important;
    border-radius: 8px !important;
    padding: 10px 14px !important;
    font-size: 14px !important;
    cursor: pointer !important;
    transition: background .13s !important;
}

ul.options li:hover, .options li:hover {
    background: rgba(127,90,240,0.22) !important;
    color: #ede8ff !important;
}

ul.options li.selected, .options li.selected {
    background: rgba(80,30,160,0.40) !important;
    color: #ede8ff !important;
    font-weight: 700 !important;
}

/* ============================================================
   BUTTONS
   ============================================================ */

/* Primary */
button.primary,
button[variant="primary"],
.gr-button.primary {
    background: linear-gradient(135deg, #6d28d9 0%, #4338ca 60%, #1d6a50 100%) !important;
    color: #fff !important;
    font-weight: 700 !important;
    font-size: 14.5px !important;
    letter-spacing: 0.3px !important;
    border: none !important;
    border-radius: 11px !important;
    padding: 12px 26px !important;
    transition: transform .22s ease, box-shadow .22s ease, filter .22s ease !important;
    box-shadow: 0 4px 18px rgba(109,40,217,0.38),
                0 1px 0 rgba(255,255,255,0.10) inset !important;
    cursor: pointer !important;
}

button.primary:hover,
button[variant="primary"]:hover {
    transform: translateY(-2px) !important;
    box-shadow: 0 8px 28px rgba(109,40,217,0.55),
                0 1px 0 rgba(255,255,255,0.14) inset !important;
    filter: brightness(1.07) !important;
}

button.primary:active,
button[variant="primary"]:active {
    transform: translateY(0) scale(0.98) !important;
    box-shadow: 0 2px 8px rgba(109,40,217,0.30) !important;
}

/* Secondary */
button.secondary,
button[variant="secondary"],
.gr-button.secondary {
    background: rgba(109,40,217,0.08) !important;
    color: #a880ff !important;
    border: 1.5px solid rgba(109,40,217,0.30) !important;
    border-radius: 10px !important;
    font-weight: 600 !important;
    font-size: 13.5px !important;
    transition: all .2s ease !important;
    cursor: pointer !important;
}

button.secondary:hover,
button[variant="secondary"]:hover {
    background: rgba(109,40,217,0.20) !important;
    border-color: rgba(109,40,217,0.60) !important;
    color: #c8a8ff !important;
    transform: translateY(-1px) !important;
    box-shadow: 0 4px 16px rgba(109,40,217,0.24) !important;
}

/* ============================================================
   MARKDOWN OUTPUT
   ============================================================ */
.gr-markdown, .prose {
    color: #c4c4dc !important;
    line-height: 1.80 !important;
}

.gr-markdown h1 {
    font-size: 1.75rem !important;
    font-weight: 800 !important;
    background: linear-gradient(90deg, #a080f8, #34d399) !important;
    -webkit-background-clip: text !important;
    -webkit-text-fill-color: transparent !important;
    margin-bottom: 12px !important;
}

.gr-markdown h2 {
    color: #9f7aea !important;
    font-size: 1.10rem !important;
    font-weight: 700 !important;
    border-left: 3px solid #7f5af0 !important;
    padding-left: 10px !important;
    margin-top: 22px !important;
    margin-bottom: 8px !important;
}

.gr-markdown h3 {
    color: #34d399 !important;
    font-size: 1rem !important;
    font-weight: 600 !important;
    margin-top: 14px !important;
}

.gr-markdown strong { color: #e2d8ff !important; }

.gr-markdown code {
    background: rgba(127,90,240,0.16) !important;
    color: #e8c4ff !important;
    border-radius: 4px !important;
    padding: 2px 7px !important;
    font-family: 'Fira Code', 'Cascadia Code', 'Consolas', monospace !important;
    font-size: 0.86em !important;
}

.gr-markdown pre {
    background: rgba(4,4,16,0.88) !important;
    border: 1px solid rgba(127,90,240,0.22) !important;
    border-radius: 11px !important;
    padding: 16px !important;
}

.gr-markdown pre code {
    background: transparent !important;
    border: none !important;
    padding: 0 !important;
}

.gr-markdown table { border-collapse: collapse !important; width: 100% !important; margin: 12px 0 !important; }
.gr-markdown th {
    background: rgba(127,90,240,0.22) !important;
    color: #ddd0ff !important;
    padding: 9px 12px !important;
    text-align: left !important;
    font-weight: 700 !important;
}
.gr-markdown td {
    border-bottom: 1px solid rgba(255,255,255,0.055) !important;
    padding: 8px 12px !important;
    color: #bebede !important;
}
.gr-markdown tr:hover td { background: rgba(127,90,240,0.07) !important; }
.gr-markdown ul, .gr-markdown ol { padding-left: 20px !important; }
.gr-markdown li { margin: 5px 0 !important; }

/* ============================================================
   FILE UPLOAD
   ============================================================ */
.file-preview, [class*="upload"] {
    border: 2px dashed rgba(127,90,240,0.32) !important;
    border-radius: 12px !important;
    background: rgba(127,90,240,0.04) !important;
    color: #7070a8 !important;
    transition: border-color .2s, background .2s !important;
}
.file-preview:hover {
    border-color: rgba(127,90,240,0.60) !important;
    background: rgba(127,90,240,0.08) !important;
}

/* ============================================================
   DATAFRAME / TABLE
   ============================================================ */
.gr-dataframe table th {
    background: rgba(127,90,240,0.20) !important;
    color: #d0c8ff !important;
    font-weight: 700 !important;
}
.gr-dataframe table td {
    color: #b8b8d8 !important;
    border-bottom: 1px solid rgba(255,255,255,0.05) !important;
}
.gr-dataframe table tr:hover td {
    background: rgba(127,90,240,0.08) !important;
}

/* ============================================================
   SCROLLBAR
   ============================================================ */
::-webkit-scrollbar       { width: 5px; height: 5px; }
::-webkit-scrollbar-track { background: transparent; }
::-webkit-scrollbar-thumb { background: rgba(127,90,240,0.45); border-radius: 3px; }
::-webkit-scrollbar-thumb:hover { background: rgba(127,90,240,0.70); }

/* ============================================================
   MISC
   ============================================================ */
hr {
    border: none !important;
    border-top: 1px solid rgba(255,255,255,0.055) !important;
    margin: 16px 0 !important;
}
"""

# ── Shared HTML fragments ─────────────────────────────────────────────────────
_HEADER = """
<div style="
  text-align: center;
  padding: 32px 24px 20px;
  background: linear-gradient(180deg, rgba(100,60,220,0.06) 0%, transparent 100%);
  border-bottom: 1px solid rgba(100,60,220,0.12);
  margin-bottom: 8px;
">
  <div style="
    font-size: 2.4rem;
    font-weight: 900;
    background: linear-gradient(90deg, #a080f8, #34d399);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    letter-spacing: -1px;
    line-height: 1.1;
    margin-bottom: 10px;
  ">AI Study Helper</div>
  <div style="
    color: #5a5a8a;
    font-size: 0.92rem;
    font-weight: 500;
    letter-spacing: 0.5px;
    margin-bottom: 18px;
  ">B.Tech CSE &middot; Mistral 7B &amp; Llama 3.1 8B via Hugging Face</div>
  <div style="display: flex; gap: 8px; justify-content: center; flex-wrap: wrap;">
    <span style="background:rgba(127,90,240,0.12);color:#a080f8;padding:4px 14px;border-radius:20px;font-size:11px;border:1px solid rgba(127,90,240,0.22);font-weight:600;letter-spacing:0.4px;">LEARN</span>
    <span style="background:rgba(44,182,125,0.09);color:#2cb67d;padding:4px 14px;border-radius:20px;font-size:11px;border:1px solid rgba(44,182,125,0.20);font-weight:600;letter-spacing:0.4px;">REVISION</span>
    <span style="background:rgba(245,168,0,0.09);color:#f5a800;padding:4px 14px;border-radius:20px;font-size:11px;border:1px solid rgba(245,168,0,0.18);font-weight:600;letter-spacing:0.4px;">QUIZ</span>
    <span style="background:rgba(240,96,96,0.08);color:#f06060;padding:4px 14px;border-radius:20px;font-size:11px;border:1px solid rgba(240,96,96,0.18);font-weight:600;letter-spacing:0.4px;">INTERVIEW</span>
    <span style="background:rgba(0,200,248,0.07);color:#00c8f8;padding:4px 14px;border-radius:20px;font-size:11px;border:1px solid rgba(0,200,248,0.16);font-weight:600;letter-spacing:0.4px;">UPLOAD</span>
    <span style="background:rgba(160,168,248,0.07);color:#a0a8f8;padding:4px 14px;border-radius:20px;font-size:11px;border:1px solid rgba(160,168,248,0.16);font-weight:600;letter-spacing:0.4px;">HISTORY</span>
  </div>
</div>
"""

_FOOTER = """
<div style="
  text-align: center;
  padding: 14px 0 10px;
  color: rgba(255,255,255,0.16);
  font-size: 11px;
  border-top: 1px solid rgba(255,255,255,0.05);
  margin-top: 16px;
  letter-spacing: 0.3px;
">
  AI Study Helper v5.1 &nbsp;&middot;&nbsp; Mistral 7B / Llama 3.1 via Hugging Face
  &nbsp;&middot;&nbsp; localhost:7860
</div>
"""


# ══════════════════════════════════════════════════════════════════════════════
# Gradio UI
# ══════════════════════════════════════════════════════════════════════════════

def _subject_row(prefix: str) -> tuple:
    """Shared subject + topic dropdown row, returns (cat_dd, top_dd)."""
    with gr.Row():
        cat = gr.Dropdown(
            choices=list(TOPICS.keys()), value=_FIRST_CAT,
            label="Subject", interactive=True, allow_custom_value=False,
        )
        top = gr.Dropdown(
            choices=_FIRST_TOPICS, value=_FIRST_TOPICS[0],
            label="Topic", interactive=True, allow_custom_value=False,
        )
    cat.change(fn=update_topics, inputs=cat, outputs=top)
    return cat, top


def _pdf_row(out_md, pdf_fn, label="Download as PDF"):
    """Add a PDF download button + clear button below any output."""
    with gr.Row():
        pdf_btn = gr.Button(f"{label}", variant="secondary")
        clr_btn = gr.Button("Clear",    variant="secondary")
    pdf_out = gr.File(label="Download")
    pdf_btn.click(fn=pdf_fn, inputs=out_md,  outputs=pdf_out)
    clr_btn.click(fn=lambda: ("", None), inputs=[], outputs=[out_md, pdf_out])
    return pdf_out


_JS = """
(function() {
  "use strict";

  function syncRadioClasses() {
    // For each radio group, mark only the checked label
    var groups = {};
    document.querySelectorAll('.gr-radio input[type="radio"]').forEach(function(inp) {
      var name = inp.name || inp.closest('fieldset')?.id || 'default';
      if (!groups[name]) groups[name] = [];
      groups[name].push(inp);
    });

    Object.values(groups).forEach(function(inputs) {
      inputs.forEach(function(inp) {
        var label = inp.closest('label');
        if (!label) return;
        if (inp.checked) {
          label.classList.add('radio-selected');
        } else {
          label.classList.remove('radio-selected');
        }
      });
    });
  }

  // Re-sync on any click inside .gr-radio containers
  document.addEventListener('click', function(e) {
    var label = e.target.closest('.gr-radio label');
    if (label) {
      // Give Gradio a moment to update its state
      setTimeout(syncRadioClasses, 30);
      setTimeout(syncRadioClasses, 150);
    }
  });

  // Re-sync whenever Gradio re-renders components
  var mo = new MutationObserver(function(mutations) {
    var relevant = mutations.some(function(m) {
      return m.target.closest && m.target.closest('.gr-radio');
    });
    if (relevant) setTimeout(syncRadioClasses, 20);
  });

  mo.observe(document.body, { childList: true, subtree: true, attributes: true,
                              attributeFilter: ['checked'] });

  // Initial sync passes
  setTimeout(syncRadioClasses, 400);
  setTimeout(syncRadioClasses, 1000);
  setTimeout(syncRadioClasses, 2500);
})();
"""

with gr.Blocks(title="AI Study Helper") as demo:

    gr.HTML(_HEADER)

    with gr.Tabs():

        # â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• 
        # TAB 1 — Learn
        # â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• 
        with gr.Tab("Learn"):
            gr.Markdown("Generate structured AI study notes - select subject, topic, level and mode.")

            l_cat, l_top = _subject_row("l")

            with gr.Row():
                l_lvl = gr.Dropdown(
                    choices=["Easy", "Intermediate", "Advanced"],
                    value="Easy", label="Difficulty",
                    interactive=True, allow_custom_value=False,
                )
                l_mode = gr.Dropdown(
                    list(_VALID_MODES), value="Learn Concept",
                    label="Study Mode", interactive=True, allow_custom_value=False,
                )

            l_btn = gr.Button("Generate Notes", variant="primary", size="lg")
            l_out = gr.Markdown("*Your AI notes will appear here.*")
            l_btn.click(fn=generate_notes, inputs=[l_cat, l_top, l_lvl, l_mode], outputs=l_out)
            _pdf_row(l_out, notes_pdf, "Download Notes PDF")

        # â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• 
        # TAB 2 — Revision
        # â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• 
        with gr.Tab("Revision"):
            gr.Markdown("Type any topic - AI creates crisp last-minute revision notes.")

            r_top = gr.Textbox(
                label="Topic to Revise",
                placeholder="e.g.  TCP/IP Handshake  |  Deadlocks  |  Merge Sort",
                lines=2,
            )
            r_btn = gr.Button("Generate Revision Notes", variant="primary", size="lg")
            r_out = gr.Markdown("*Revision notes will appear here.*")
            r_btn.click(fn=generate_revision, inputs=r_top, outputs=r_out)
            _pdf_row(r_out, revision_pdf, "Download Revision PDF")

        # â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• 
        # TAB 3 — Quiz (interactive MCQ)
        # ══════════════════════════════════════════════════════════════════
        with gr.Tab("Quiz"):
            gr.Markdown(
                "AI generates **5 MCQ questions** with 4 options each.  "
                "Select your answers then click **Submit Quiz** for instant feedback."
            )

            quiz_state = gr.State([])

            qz_cat, qz_top = _subject_row("qz")
            qz_lvl = gr.Dropdown(
                choices=["Easy", "Intermediate", "Advanced"],
                value="Intermediate", label="Difficulty",
                interactive=True, allow_custom_value=False,
            )
            qz_gen = gr.Button("Generate Quiz", variant="primary", size="lg")
            qz_status = gr.Markdown()

            # Pre-create 5 question slots (hidden until quiz is generated)
            # Dropdown widgets for answer selection (consistent with Subject/Topic/Level UI)
            qz_groups, qz_qmds, qz_radios = [], [], []
            for i in range(5):
                with gr.Group(visible=False) as g:
                    qmd  = gr.Markdown(f"Q{i + 1}.")
                    qrad = gr.Dropdown(
                        choices=[], label="Select your answer:",
                        interactive=True, value=None,
                        allow_custom_value=False,
                    )
                qz_groups.append(g)
                qz_qmds.append(qmd)
                qz_radios.append(qrad)

            qz_submit = gr.Button("Submit Quiz", variant="primary", visible=False)

            with gr.Group(visible=False) as qz_res_grp:
                qz_res_md = gr.Markdown()
            qz_score = gr.Markdown()

            # Wire generate — 19 outputs total
            _gen_outs = [quiz_state, qz_status]
            for i in range(5):
                _gen_outs += [qz_groups[i], qz_qmds[i], qz_radios[i]]
            _gen_outs += [qz_submit, qz_res_grp]

            qz_gen.click(fn=generate_quiz_fn,
                         inputs=[qz_cat, qz_top, qz_lvl],
                         outputs=_gen_outs)

            # Wire submit — 3 outputs
            qz_submit.click(
                fn=check_quiz_fn,
                inputs=[quiz_state] + qz_radios,
                outputs=[qz_res_grp, qz_res_md, qz_score],
            )

            # PDF download (downloads the results markdown)
            with gr.Row():
                qz_pdf_btn = gr.Button("Download Quiz PDF", variant="secondary")
            qz_pdf = gr.File(label="Download")
            qz_pdf_btn.click(fn=quiz_pdf, inputs=qz_res_md, outputs=qz_pdf)

        # â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• 
        # TAB 4 — Interview Prep
        # â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• 
        with gr.Tab("Interview Prep"):
            gr.Markdown("Get a complete placement interview pack - technical Q&A, coding, and HR tips.")

            i_cat, i_top = _subject_row("iv")
            i_btn = gr.Button("Generate Interview Pack", variant="primary", size="lg")
            i_out = gr.Markdown("*Interview Q&A will appear here.*")
            i_btn.click(fn=generate_interview, inputs=[i_cat, i_top], outputs=i_out)
            _pdf_row(i_out, interview_pdf, "Download Interview PDF")

        # â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• 
        # TAB 5 — Upload Notes
        # â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• â• 
        with gr.Tab("Upload Notes"):
            gr.Markdown("Upload your PDF or TXT notes - AI summarises, extracts key points and generates exam questions.")

            with gr.Row(equal_height=False):
                with gr.Column(scale=1):
                    gr.Markdown("#### Upload Panel")
                    u_file = gr.File(label="Drop PDF or TXT here", file_types=[".pdf", ".txt"])
                    u_btn  = gr.Button("Analyse Notes", variant="primary", size="lg")

                with gr.Column(scale=2):
                    gr.Markdown("#### AI Summary")
                    u_out  = gr.Markdown("*Upload a file and click Analyse Notes.*")

            u_btn.click(fn=analyze_upload, inputs=u_file, outputs=u_out)
            _pdf_row(u_out, upload_pdf, "Download Summary PDF")

        # ══════════════════════════════════════════════════════════════════
        # TAB 6 — History
        # ══════════════════════════════════════════════════════════════════
        with gr.Tab("History"):
            gr.Markdown(
                "Persistent session log ” stored in `study_history.json`.  "
                "Last 50 entries shown."
            )

            with gr.Row():
                h_refresh = gr.Button("Refresh",        variant="primary")
                h_clear   = gr.Button("Clear History",  variant="secondary")

            h_table = gr.DataFrame(
                headers=["#", "Timestamp", "Tab", "Topic / File", "Mode . Level"],
                datatype=["number", "str", "str", "str", "str"],
                interactive=False,
                
                label="Generation History",
            )
            h_status = gr.Markdown()

            h_refresh.click(fn=get_history_data, inputs=[], outputs=h_table)
            h_clear.click(fn=clear_history_fn,   inputs=[], outputs=[h_table, h_status])

    gr.HTML(_FOOTER)


# ── Launch ────────────────────────────────────────────────────────────────────
# Binds to 127.0.0.1 only — do NOT change to 0.0.0.0 without adding auth.
demo.launch(server_name="0.0.0.0", server_port=7860)