"""
progress.py — Student progress engine.

Handles:
  - recording attempts
  - updating mastery scores (decay + boost)
  - streak tracking
  - computing weak/strong topics
  - generating weekly report
  - generating personalised study plan
  - next difficulty recommendation (adaptive)
"""

from datetime import datetime, date, timedelta
from database import db
import math


# ─────────────────────────────────────────
# MASTERY FORMULA
# mastery = correct / total  (weighted)
# decay   = 0.95 per day inactive
# boost   = +0.05 per consecutive correct
# range   = [0.0, 1.0]
# ─────────────────────────────────────────

DECAY_PER_DAY   = 0.95
BOOST_ON_CORRECT = 0.05
MIN_MASTERY     = 0.0
MAX_MASTERY     = 1.0


def record_attempt(
    student_id: int,
    question: str,
    topic: str,
    error_type: str,
    response: str,
    difficulty: int,
    mode: str = "text",
    explain_level: str = "normal",
) -> int:
    """Insert attempt row, update mastery + error log + streak. Returns attempt id."""
    with db() as conn:
        cur = conn.execute(
            """INSERT INTO attempts
               (student_id, question, topic, error_type, response, difficulty, mode, explain_level)
               VALUES (?,?,?,?,?,?,?,?)""",
            (student_id, question, topic, error_type, response, difficulty, mode, explain_level),
        )
        attempt_id = cur.lastrowid

        # ── update mastery ──
        conn.execute(
            """INSERT INTO topic_mastery (student_id, topic, attempts, correct, mastery_score)
               VALUES (?,?,1,0,0.0)
               ON CONFLICT(student_id, topic) DO UPDATE SET
                 attempts = attempts + 1,
                 last_updated = datetime('now')""",
            (student_id, topic),
        )

        # treat "None detected" errors as correct
        is_correct = error_type in (None, "", "None detected")
        if is_correct:
            conn.execute(
                """UPDATE topic_mastery SET
                     correct = correct + 1,
                     mastery_score = MIN(1.0, mastery_score + ?),
                     last_updated = datetime('now')
                   WHERE student_id=? AND topic=?""",
                (BOOST_ON_CORRECT, student_id, topic),
            )
        else:
            # error: log it and slightly decrease mastery
            conn.execute(
                """INSERT INTO error_log (student_id, topic, error_type, count, last_seen)
                   VALUES (?,?,?,1,datetime('now'))
                   ON CONFLICT(student_id, topic, error_type) DO UPDATE SET
                     count = count + 1,
                     last_seen = datetime('now')""",
                (student_id, topic, error_type),
            )
            conn.execute(
                """UPDATE topic_mastery SET
                     mastery_score = MAX(0.0, mastery_score - 0.03),
                     last_updated = datetime('now')
                   WHERE student_id=? AND topic=?""",
                (student_id, topic),
            )

        # ── streak ──
        row = conn.execute(
            "SELECT last_active FROM students WHERE id=?", (student_id,)
        ).fetchone()
        today_str = date.today().isoformat()
        last = row["last_active"] if row else None
        new_streak_sql = "streak + 1" if last != today_str else "streak"
        conn.execute(
            f"UPDATE students SET last_active=?, streak={new_streak_sql} WHERE id=?",
            (today_str, student_id),
        )

    return attempt_id


def get_next_difficulty(student_id: int, topic: str, current: int = 5) -> int:
    """Adaptive difficulty: harder if mastery > 0.7, easier if < 0.35."""
    with db() as conn:
        row = conn.execute(
            "SELECT mastery_score, attempts FROM topic_mastery WHERE student_id=? AND topic=?",
            (student_id, topic),
        ).fetchone()

    if not row or row["attempts"] < 3:
        return current  # not enough data yet

    score = row["mastery_score"]
    if score >= 0.70:
        return min(10, current + 1)
    elif score <= 0.35:
        return max(1, current - 1)
    return current


def get_student_stats(student_id: int) -> dict:
    """Full stats object for dashboard."""
    with db() as conn:
        student = conn.execute(
            "SELECT * FROM students WHERE id=?", (student_id,)
        ).fetchone()
        if not student:
            return {}

        mastery_rows = conn.execute(
            "SELECT topic, attempts, correct, mastery_score FROM topic_mastery WHERE student_id=? ORDER BY mastery_score DESC",
            (student_id,),
        ).fetchall()

        error_rows = conn.execute(
            "SELECT topic, error_type, count FROM error_log WHERE student_id=? ORDER BY count DESC LIMIT 10",
            (student_id,),
        ).fetchall()

        total_attempts = conn.execute(
            "SELECT COUNT(*) as n FROM attempts WHERE student_id=?", (student_id,)
        ).fetchone()["n"]

        # attempts last 7 days grouped by day
        daily = conn.execute(
            """SELECT date(created_at) as day, COUNT(*) as n
               FROM attempts WHERE student_id=? AND created_at >= date('now','-6 days')
               GROUP BY day ORDER BY day""",
            (student_id,),
        ).fetchall()

        # topic distribution
        topic_dist = conn.execute(
            """SELECT topic, COUNT(*) as n FROM attempts
               WHERE student_id=? GROUP BY topic ORDER BY n DESC""",
            (student_id,),
        ).fetchall()

    mastery = [dict(r) for r in mastery_rows]
    errors  = [dict(r) for r in error_rows]

    weak   = [m for m in mastery if m["mastery_score"] < 0.4 and m["attempts"] >= 2]
    strong = [m for m in mastery if m["mastery_score"] >= 0.7]

    overall_accuracy = (
        sum(m["correct"] for m in mastery) / max(1, sum(m["attempts"] for m in mastery))
    ) * 100

    return {
        "student":          dict(student),
        "total_attempts":   total_attempts,
        "overall_accuracy": round(overall_accuracy, 1),
        "mastery":          mastery,
        "weak_topics":      weak,
        "strong_topics":    strong,
        "top_errors":       errors,
        "daily_activity":   [dict(r) for r in daily],
        "topic_distribution": [dict(r) for r in topic_dist],
    }


def get_weekly_report(student_id: int) -> dict:
    """Generate human-readable weekly progress report."""
    with db() as conn:
        rows = conn.execute(
            """SELECT topic, error_type, created_at FROM attempts
               WHERE student_id=? AND created_at >= date('now','-7 days')
               ORDER BY created_at""",
            (student_id,),
        ).fetchall()

        prev_rows = conn.execute(
            """SELECT COUNT(*) as n FROM attempts
               WHERE student_id=? AND created_at >= date('now','-14 days')
                 AND created_at < date('now','-7 days')""",
            (student_id,),
        ).fetchone()

    this_week  = len(rows)
    last_week  = prev_rows["n"] if prev_rows else 0
    growth_pct = round(((this_week - last_week) / max(1, last_week)) * 100)

    topic_counts: dict[str, int] = {}
    for r in rows:
        topic_counts[r["topic"]] = topic_counts.get(r["topic"], 0) + 1

    most_practiced = max(topic_counts, key=topic_counts.get) if topic_counts else "—"

    stats = get_student_stats(student_id)

    insights = []
    if stats.get("weak_topics"):
        wt = stats["weak_topics"][0]["topic"]
        insights.append(f"Focus area this week: {wt} needs more practice.")
    if stats.get("strong_topics"):
        st = stats["strong_topics"][0]["topic"]
        insights.append(f"Great progress in {st} — keep it up!")
    if growth_pct > 0:
        insights.append(f"You solved {growth_pct}% more questions than last week!")
    elif growth_pct < 0:
        insights.append("Try to solve a few more questions this week to maintain momentum.")

    return {
        "questions_this_week": this_week,
        "questions_last_week": last_week,
        "growth_pct":          growth_pct,
        "most_practiced":      most_practiced,
        "insights":            insights,
        "accuracy":            stats.get("overall_accuracy", 0),
        "streak":              stats.get("student", {}).get("streak", 0),
    }


def generate_study_plan(student_id: int) -> list[dict]:
    """Return ordered list of recommended topics + question counts."""
    stats = get_student_stats(student_id)
    plan  = []

    for w in stats.get("weak_topics", [])[:3]:
        plan.append({
            "topic":        w["topic"],
            "priority":     "high",
            "reason":       f"Mastery only {round(w['mastery_score']*100)}% — needs work",
            "questions":    5,
        })

    for m in stats.get("mastery", []):
        if 0.4 <= m["mastery_score"] < 0.7 and len(plan) < 5:
            plan.append({
                "topic":    m["topic"],
                "priority": "medium",
                "reason":   f"Mastery at {round(m['mastery_score']*100)}% — almost there",
                "questions": 3,
            })

    if not plan:
        plan.append({
            "topic":    "General STEM",
            "priority": "normal",
            "reason":   "Start solving questions to unlock your personalised plan",
            "questions": 5,
        })

    return plan