import os
import glob
import json
import psutil
import asyncio
import re
import tempfile
import shutil
from pathlib import Path
from typing import Any, Dict, List, Optional
from datetime import datetime, timedelta

from fastapi import FastAPI, Request, HTTPException, UploadFile, File
from fastapi.responses import StreamingResponse
from fastapi.middleware.cors import CORSMiddleware
from llama_cpp import Llama

try:
    import aiohttp
except ImportError:
    aiohttp = None

app = FastAPI(title="Hannah Pilot Interface")

# --- CORS Permissions ---
app.add_middleware(
    CORSMiddleware,
    allow_origins=["*"],
    allow_credentials=True,
    allow_methods=["*"],
    allow_headers=["*"],
)

# --- Configuration ---
# Map filenames to "Hannah" names
MODEL_MAP: Dict[str, str] = {
    "qwen2.5-0.5b-instruct-q2_k.gguf": "Hannah-1.1 Light",
    "qwen2.5-0.5b-instruct-q4_k_m.gguf": "Hannah-1.1 Heavy",
}

current_model: Optional[Llama] = None
current_model_name: str = ""

# --- File Upload Configuration ---
UPLOAD_DIR = Path(tempfile.gettempdir()) / "hannah_uploads"


def _model_abs_path(model_name: str) -> Path:
    # Always resolve relative to the app directory to avoid cwd surprises.
    base_dir = Path(__file__).resolve().parent
    return (base_dir / model_name).resolve()


def _looks_like_pointer_file(path: Path) -> bool:
    # If the GGUF file is a Git LFS pointer (or similar), llama.cpp will fail to load it.
    try:
        if not path.exists() or path.is_dir():
            return False
        head = path.read_bytes()[:256]
        if b"git-lfs" in head and b"oid sha256" in head:
            return True
        # Some pointer files are plain text starting with "version".
        if head.startswith(b"version ") and b"sha256" in head:
            return True
        return False
    except Exception:
        return False


def _try_load_model(
    model_path: Path, *, n_ctx: int, n_threads: int, n_batch: int
) -> Llama:
    # Keep this tiny and explicit so we can retry with different params.
    return Llama(
        model_path=str(model_path),
        n_ctx=n_ctx,
        n_threads=n_threads,
        n_batch=n_batch,
        # mmap tends to be friendlier on low-memory CPU machines
        use_mmap=True,
        verbose=False,
    )


def get_model(model_name: str) -> Llama:
    global current_model, current_model_name

    if not model_name:
        raise HTTPException(status_code=400, detail="No model selected")

    model_path = _model_abs_path(model_name)
    if not model_path.exists():
        raise HTTPException(
            status_code=404,
            detail=f"Model file not found: {model_path.name}",
        )
    if _looks_like_pointer_file(model_path):
        raise HTTPException(
            status_code=500,
            detail=(
                "Model file looks like a pointer (not the real .gguf). "
                "Re-upload the GGUF to the Space (so it is stored as the full binary), "
                "then restart the Space."
            ),
        )
    try:
        size_mb = model_path.stat().st_size / (1024 * 1024)
    except Exception:
        size_mb = -1

    if current_model_name == model_name and current_model is not None:
        return current_model

    print(f"Loading {model_path.name} ({size_mb:.1f} MB)...")
    if current_model is not None:
        del current_model

    # --- PERFORMANCE TUNING (HF Free CPU) ---
    # Increased context for Hannah 1.1 with better memory management
    # 4096 ctx provides more context awareness; fallback to 2048 if needed
    threads = int(os.getenv("N_THREADS", "2"))
    n_ctx = int(os.getenv("N_CTX", "4096"))  # Increased from 2048
    n_batch = int(os.getenv("N_BATCH", "512"))  # Increased from 256

    try:
        current_model = _try_load_model(
            model_path, n_ctx=n_ctx, n_threads=threads, n_batch=n_batch
        )
    except Exception as e:
        # Retry with conservative settings in case of memory pressure
        print(f"Model load failed with N_CTX={n_ctx}, N_BATCH={n_batch}: {e}")
        try:
            current_model = _try_load_model(
                model_path, n_ctx=2048, n_threads=threads, n_batch=256
            )
        except Exception as e2:
            print(f"Model load retry failed: {e2}")
            raise HTTPException(
                status_code=500,
                detail=(
                    "Failed to load GGUF model. This is usually caused by: "
                    "(1) model file not fully present inside the container, "
                    "(2) not enough RAM for the chosen context size, or "
                    "(3) llama-cpp-python too old for this GGUF. "
                    f"Model: {model_path.name}"
                ),
            )

    current_model_name = model_name
    return current_model


@app.get("/")
async def root():
    return {"status": "ok", "name": "Hannah-1.1"}


@app.get("/api/models")
async def list_models():
    models_info: List[Dict[str, Any]] = []
    for f in glob.glob("*.gguf"):
        display_name = MODEL_MAP.get(f, f)
        size_mb = os.path.getsize(f) / (1024 * 1024)
        models_info.append(
            {
                "filename": f,
                "display_name": display_name,
                "size": f"{size_mb:.1f} MB",
            }
        )

    # Stable ordering (Heavy first if present)
    models_info.sort(
        key=lambda x: (
            "Heavy" not in x.get("display_name", ""),
            x.get("display_name", ""),
        )
    )
    return {"models": models_info}


@app.get("/api/status")
async def system_status():
    ram = psutil.virtual_memory()
    return {
        "ram_used": f"{ram.used / (1024 * 1024):.0f} MB",
        "cpu": f"{psutil.cpu_percent()}%",
    }


@app.post("/api/gen_title")
async def gen_title(request: Request):
    try:
        data = await request.json()
        message = (data.get("message") or "").strip()
        words = message.split()[:4]
        title = " ".join(words).capitalize() + ("..." if words else "")
        return {"title": title or "New Chat"}
    except Exception:
        return {"title": "New Chat"}


def cleanup_old_files(max_age_hours: int = 24):
    """Remove files older than max_age_hours from upload directory."""
    if not UPLOAD_DIR.exists():
        return

    now = datetime.now()
    for file_path in UPLOAD_DIR.glob("*"):
        if file_path.is_file():
            file_age = now - datetime.fromtimestamp(file_path.stat().st_mtime)
            if file_age.total_seconds() > max_age_hours * 3600:
                try:
                    file_path.unlink()
                except Exception:
                    pass


@app.post("/api/upload")
async def upload_file(file: UploadFile = File(...)):
    """Upload a file and store it temporarily. Returns preview and file path."""
    try:
        # Create upload directory if it doesn't exist
        UPLOAD_DIR.mkdir(parents=True, exist_ok=True)

        # Check file size (50MB limit)
        content = await file.read()
        if len(content) > 50 * 1024 * 1024:
            raise HTTPException(status_code=413, detail="File too large (max 50MB)")

        # Save file with timestamp
        timestamp = datetime.now().timestamp()
        file_path = UPLOAD_DIR / f"{timestamp}_{file.filename}"

        with open(file_path, "wb") as f:
            f.write(content)

        # Try to extract text preview
        preview = None
        try:
            text_content = content.decode("utf-8", errors="ignore")
            preview = text_content[:1000]  # First 1000 chars
        except Exception:
            pass

        # Run cleanup in background
        cleanup_old_files()

        return {
            "success": True,
            "filename": file.filename,
            "file_url": str(file_path),
            "size_kb": len(content) / 1024,
            "preview": preview,
        }
    except HTTPException:
        raise
    except Exception as e:
        raise HTTPException(status_code=500, detail=str(e))


def extract_file_urls(message: str) -> List[str]:
    """Extract file URLs from message (Google Drive URLs and uploaded file paths)."""
    urls = []

    # Extract Google Drive URLs
    drive_pattern = r"https://drive\.google\.com/[^\s\)\"<>]*"
    urls.extend(re.findall(drive_pattern, message))

    # Extract uploaded file references: [File uploaded: path]
    upload_pattern = r"\[File uploaded: ([^\]]+)\]"
    urls.extend(re.findall(upload_pattern, message))

    return urls


async def fetch_file_from_url(file_url: str, max_size: int = 10 * 1024 * 1024) -> str:
    """
    Fetch a file from URL or local path and return its content as text.
    Works with:
    - Local file paths (uploaded files)
    - Google Drive URLs
    - Text files via HTTP
    """
    try:
        # Check if it's a local file path first
        local_path = Path(file_url)
        if local_path.exists() and local_path.is_file():
            try:
                with open(local_path, "rb") as f:
                    content = f.read()

                if len(content) > max_size:
                    return f"[File too large to process: {len(content) / 1024 / 1024:.1f}MB, max 10MB]"

                try:
                    text = content.decode("utf-8", errors="ignore")
                    return text[:3000]
                except Exception:
                    return f"[Binary file detected. Size: {len(content) / 1024:.1f}KB.]"
            except Exception as e:
                return f"[Could not read local file: {str(e)[:100]}]"

        # Handle remote URLs (Google Drive, HTTP, etc.)
        if not aiohttp:
            return "[File fetching requires aiohttp - install via pip install aiohttp]"

        # Convert Google Drive sharing link to direct download link if needed
        if "drive.google.com" in file_url:
            # Extract file ID from Google Drive URL
            import re

            file_id_match = re.search(r"/d/([a-zA-Z0-9-_]+)", file_url)
            if not file_id_match:
                file_id_match = re.search(r"id=([a-zA-Z0-9-_]+)", file_url)

            if file_id_match:
                file_id = file_id_match.group(1)
                # Use export=download for Google Drive files
                file_url = f"https://drive.google.com/uc?id={file_id}&export=download"

        async with aiohttp.ClientSession() as session:
            async with session.get(
                file_url, timeout=aiohttp.ClientTimeout(total=15), allow_redirects=True
            ) as resp:
                if resp.status != 200:
                    return f"[Could not fetch file: HTTP {resp.status}]"

                content = await resp.read()

                if len(content) > max_size:
                    return f"[File too large to process: {len(content) / 1024 / 1024:.1f}MB, max 10MB]"

                # Try to decode as text
                try:
                    text = content.decode("utf-8")
                    # Limit preview to first 3000 chars
                    return text[:3000]
                except UnicodeDecodeError:
                    # For binary files, return a note
                    return f"[Binary file detected. Size: {len(content) / 1024:.1f}KB. Please describe what you see in it.]"
    except asyncio.TimeoutError:
        return "[File fetch timed out - file may be too large or URL invalid]"
    except Exception as e:
        return f"[Could not fetch file: {str(e)[:100]}]"


def build_prompt(
    user_input: str, history: List[Dict[str, str]], has_web_context: bool = False
) -> str:
    # Qwen 2.5 chat format with optional web context awareness
    system = (
        "You are Hannah 1.0, an intelligent, fast, and helpful AI assistant. "
        "Answer clearly and accurately. "
    )

    # If web context is available, instruct the model to use it
    if has_web_context:
        system += (
            "You have been provided with fresh web search context in the user's message. "
            "Use this context to provide current, accurate information about recent events and dates. "
            "Reference the sources when relevant. "
        )

    system += (
        "Keep responses concise but helpful. "
        "If asked about your model or training details, simply say: 'I'm Hannah - a helpful AI assistant.' "
        "Do not discuss GGUF files or internal implementation details."
    )

    parts: List[str] = ["<|im_start|>system\n" + system + "<|im_end|>\n"]

    # Keep a small window of history for speed
    for msg in history[-12:]:
        role = msg.get("role")
        content = msg.get("content") or ""
        if role not in ("user", "assistant"):
            continue
        parts.append(f"<|im_start|>{role}\n{content}<|im_end|>\n")

    parts.append(f"<|im_start|>user\n{user_input}<|im_end|>\n<|im_start|>assistant\n")
    return "".join(parts)


@app.post("/api/chat")
async def chat(request: Request):
    data = await request.json()
    user_input = (data.get("message") or "").strip()
    model_file = data.get("model")
    history = data.get("history") or []
    has_web = data.get("internet", False)  # Check if web search was enabled

    if not user_input:
        raise HTTPException(status_code=400, detail="Empty message")

    # Extract and fetch file URLs from the message
    file_urls = extract_file_urls(user_input)
    file_content_parts = []

    if file_urls:
        for url in file_urls:
            print(f"[File Processing] Fetching: {url[:80]}...")
            content = await fetch_file_from_url(url)
            if content:
                file_content_parts.append(content)

        # Append file contents to user input so the model can process them
        if file_content_parts:
            file_section = "\n\n[File Contents Retrieved]:\n" + "\n---\n".join(
                file_content_parts
            )
            user_input = user_input + file_section

    llm = get_model(model_file)

    # Detect if the message includes web context
    has_web_context = has_web and "[Web context retrieved on" in user_input

    def iter_response():
        prompt = build_prompt(user_input, history, has_web_context=has_web_context)

        stream = llm(
            prompt,
            max_tokens=4096,  # Increased from 2048 for better responses
            stop=["<|im_end|>", "User:", "System:"],
            stream=True,
        )

        for output in stream:
            token_text = output["choices"][0]["text"]
            yield json.dumps({"text": token_text}) + "\n"

    # NDJSON stream (frontend splits by newlines)
    return StreamingResponse(iter_response(), media_type="application/x-ndjson")