# database/database_manager.py

from __future__ import annotations
import logging
import os
from datetime import date, timedelta
from typing import Optional

import bcrypt
import streamlit as st
from dotenv import load_dotenv
from sqlalchemy import create_engine, text
from sqlalchemy.pool import QueuePool

load_dotenv()

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

# ── SRS constants ──────────────────────────────────────────────────────────────
def _next_review(mastery: float) -> str:
    """Return next review date as ISO-8601 string (YYYY-MM-DD).
    Returned as str, not datetime.date, because the legacy {SQL Server}
    ODBC driver raises HYC00 when binding Python date objects directly."""
    mastery  = max(0.0, min(mastery, 0.99))
    interval = round((1 / (1 - mastery + 0.01)) ** 1.5)
    interval = max(1, min(interval, 60))
    return (date.today() + timedelta(days=interval)).isoformat()


def _new_mastery(old_mastery: float, passed: bool) -> float:
    delta = 0.20 if passed else -0.10
    return round(max(0.0, min(1.0, old_mastery + delta)), 4)


# ── SQLAlchemy Engine (singleton with QueuePool) ───────────────────────────────
_engine = None

def _get_engine():
    global _engine
    if _engine is not None:
        return _engine

    try:
       conn_url = st.secrets["DATABASE_URL"]
        
       if conn_url.startswith("postgres://"):
          conn_url = conn_url.replace("postgres://", "postgresql://", 1)
    except Exception:
        # رابط التجربة الذي زودتِني به
        conn_url = "postgresql://postgres.juyvtapnigpdavxaniqg:oklEE4CRY7VR3Jh2@aws-0-eu-west-1.pooler.supabase.com:6543/postgres"

    _engine = create_engine(
        conn_url,
        poolclass=QueuePool,
        pool_size=5,
        max_overflow=10,
        pool_pre_ping=True,
        pool_recycle=1800,
    )
    
    logger.info("SQLAlchemy engine initialised for Supabase (PostgreSQL).")
    return _engine

def _conn():
    """Context-managed connection from the pool."""
    return _get_engine().connect()


# ── Cache busting helper ────────────────────────────────────────────────────────
def _bust_cache() -> None:
    try:
        get_performance_stats.clear()
        get_top_errors.clear()
    except Exception:
        pass


# ── bcrypt helpers ─────────────────────────────────────────────────────────────
def _hash_password(plain: str) -> str:
    return bcrypt.hashpw(plain.encode("utf-8"), bcrypt.gensalt()).decode("utf-8")


def _verify_password(plain: str, hashed: str) -> bool:
    try:
        return bcrypt.checkpw(plain.encode("utf-8"), hashed.encode("utf-8"))
    except Exception:
        return False


# ── Input validation ───────────────────────────────────────────────────────────
def _validate_username(username: str) -> str:
    username = username.strip()
    if not username or len(username) < 3:
        raise ValueError("Username must be at least 3 characters.")
    if len(username) > 50:
        raise ValueError("Username must be at most 50 characters.")
    return username


def _validate_password(password: str) -> None:
    if not password or len(password) < 6:
        raise ValueError("Password must be at least 6 characters.")


# ══════════════════════════════════════════════════════════════════════════════
# AUTH
# ══════════════════════════════════════════════════════════════════════════════

def check_user(username: str, password: str) -> Optional[tuple]:
    """Return (Username, TotalXP, CurrentLevel, CurrentSentence, RegistrationDate) or None."""
    try:
        username = _validate_username(username)
    except ValueError:
        return None

    try:
        with _conn() as conn:
            row = conn.execute(
                text(
                    "SELECT Username, TotalXP, CurrentLevel, CurrentSentence, PasswordHash, "
                    "RegistrationDate "
                    "FROM Users WHERE Username = :u"
                ),
                {"u": username},
            ).fetchone()

        if row is None:
            return None
        if row[4] and _verify_password(password, row[4]):
            return (row[0], row[1], row[2], row[3], row[5])
        return None

    except Exception as exc:
        logger.error("check_user failed for '%s': %s", username, exc, exc_info=True)
        st.error("Database connection error. Please try again.")
        return None


def add_user(username: str, password: str) -> bool:
    try:
        username = _validate_username(username)
        _validate_password(password)
    except ValueError as ve:
        st.error(str(ve))
        return False

    try:
        hashed = _hash_password(password)
        with _conn() as conn:
            conn.execute(
                text(
                    "INSERT INTO Users (Username, PasswordHash, TotalXP, CurrentLevel, "
                    "CurrentSentence, UserLevel) VALUES (:u, :h, 0, 0, 0, 'Beginner')"
                ),
                {"u": username, "h": hashed},
            )
            conn.commit()
        _bust_cache()
        return True

    except Exception as exc:
        err_str = str(exc).lower()
        if "unique" in err_str or "duplicate" in err_str or "violation" in err_str:
            st.error("Username already taken.")
        else:
            logger.error("add_user failed for '%s': %s", username, exc, exc_info=True)
            st.error("Could not create account. Please try again.")
        return False


# ══════════════════════════════════════════════════════════════════════════════
# PROGRESS
# ══════════════════════════════════════════════════════════════════════════════

def update_user_progress(
    username: str, xp: int, level: int, sentence: int
) -> None:
    try:
        with _conn() as conn:
            conn.execute(
                text(
                    "UPDATE Users SET TotalXP=:xp, CurrentLevel=:lv, "
                    "CurrentSentence=:sn WHERE Username=:u"
                ),
                {"xp": xp, "lv": level, "sn": sentence, "u": username},
            )
            conn.commit()
    except Exception as exc:
        logger.warning("update_user_progress failed: %s", exc)


# ══════════════════════════════════════════════════════════════════════════════
# PERFORMANCE LOGGING
# ══════════════════════════════════════════════════════════════════════════════

def log_performance(
    username: str,
    target: str,
    transcript: str,
    accuracy: float,
    status: str,
) -> None:
    try:
        with _conn() as conn:
            conn.execute(
                text(
                    "INSERT INTO PerformanceLog "
                    "(Username, TargetSentence, UserTranscript, AccuracyPercentage, FeedbackStatus) "
                    "VALUES (:u, :t, :tr, :a, :s)"
                ),
                {
                    "u":  username,
                    "t":  target,
                    "tr": transcript,
                    "a":  round(accuracy, 2),
                    "s":  status,
                },
            )
            conn.commit()
        _bust_cache()
    except Exception as exc:
        logger.warning("log_performance failed: %s", exc)

@st.cache_data(ttl=30)
def get_performance_stats(username: str) -> list[tuple]:
    try:
        with _conn() as conn:
            rows = conn.execute(
                text(
                    "SELECT AccuracyPercentage, FeedbackStatus, TargetSentence, "
                    "UserTranscript, SessionTimestamp FROM PerformanceLog "
                    "WHERE Username=:u ORDER BY SessionTimestamp DESC LIMIT 10"
                ),
                {"u": username},
            ).fetchall()
        return [tuple(r) for r in rows]
    except Exception as exc:
        logger.warning("get_performance_stats failed: %s", exc)
        st.warning("Stats fetch failed.")
        return []

def get_all_performance_stats(username: str) -> list[tuple]:
    try:
        with _conn() as conn:
            rows = conn.execute(
                text(
                    "SELECT AccuracyPercentage, SessionTimestamp, TargetSentence "
                    "FROM PerformanceLog WHERE Username=:u ORDER BY SessionTimestamp ASC"
                ),
                {"u": username},
            ).fetchall()
        return [tuple(r) for r in rows]
    except Exception as exc:
        logger.warning("get_all_performance_stats failed: %s", exc)
        st.warning("Full stats fetch failed.")
        return []


# ══════════════════════════════════════════════════════════════════════════════
# WORD-ERROR TRACKING  — SRS-enhanced
# ══════════════════════════════════════════════════════════════════════════════
def log_word_error(
    username: str,
    expected_word: str,
    user_said: str,
    phoneme_target: str = "",
) -> None:
    
    try:
        expected_word  = expected_word.lower().strip()[:90]
        user_said      = user_said.lower().strip()[:90]
        phoneme_target = phoneme_target[:254] if phoneme_target else ""

        with _conn() as conn:
           
            row = conn.execute(
                text(
                    "SELECT ErrorID, ErrorCount, mastery_score FROM UserErrors "
                                        "WHERE Username=:u AND ExpectedWord=:e AND UserSaid=:s"
                ),
                {"u": username, "e": expected_word, "s": user_said},
            ).fetchone()

            if row:

                new_count   = row[1] + 1
                new_mastery = _new_mastery(float(row[2] or 0.0), passed=False)
                new_review  = _next_review(new_mastery)
                conn.execute(
                    text(
                        "UPDATE UserErrors SET ErrorCount=:c, mastery_score=:m, "
                        "next_review_date=:r, LastSeen=CURRENT_TIMESTAMP, phoneme_target=:p "
                        "WHERE ErrorID=:id"
                    ),
                    {
                        "c":  new_count,
                        "m":  new_mastery,
                        "r":  new_review,
                        "p":  phoneme_target,
                        "id": row[0],
                    },
                )
            else:

                first_review = date.today().isoformat()
                conn.execute(
                    text(
                        "INSERT INTO UserErrors "
                        "(Username, ExpectedWord, UserSaid, ErrorCount, mastery_score, "
                        "next_review_date, phoneme_target, LastSeen) "
                        "VALUES (:u, :e, :s, 1, 0.0, :r, :p, CURRENT_TIMESTAMP)"
                    ),
                    {
                        "u": username,
                        "e": expected_word,
                        "s": user_said,
                        "r": first_review,
                        "p": phoneme_target,
                    },
                )
            conn.commit()

    except Exception as exc:
        logger.error("log_word_error فشل: %s", exc, exc_info=True)
        st.error(f"SQL INSERT FAILED (log_word_error): {exc}")


def update_word_mastery(username: str, expected_word: str, passed: bool) -> None:
    try:
        expected_word = expected_word.lower().strip()[:90]
        with _conn() as conn:
            rows = conn.execute(
                text(
                    "SELECT ErrorID, mastery_score FROM UserErrors "
                    "WHERE Username=:u AND ExpectedWord=:e"
                ),
                {"u": username, "e": expected_word},
            ).fetchall()
            for row in rows:
                new_mastery = _new_mastery(float(row[1] or 0.0), passed=passed)
                new_review  = _next_review(new_mastery)
                conn.execute(
                    text(
                        "UPDATE UserErrors SET mastery_score=:m, next_review_date=:r "
                        "WHERE ErrorID=:id"
                    ),
                    {"m": new_mastery, "r": new_review, "id": row[0]},
                )
            conn.commit()
    except Exception as exc:
        logger.error("update_word_mastery failed: %s", exc, exc_info=True)
def get_recent_errors(username: str, limit: int = 10) -> list[dict]:
    try:
        with _conn() as conn:
            rows = conn.execute(
                text(
                    "SELECT ExpectedWord, UserSaid, ErrorCount, "
                    "COALESCE(mastery_score, 0.0), COALESCE(phoneme_target, '') "
                    "FROM UserErrors WHERE Username=:u "
                    "ORDER BY ErrorCount DESC, LastSeen DESC "
                    "LIMIT :lim OFFSET 0"
                ),
                {"lim": limit, "u": username},
            ).fetchall()
        return [
            {
                "expected": r[0],
                "said":     r[1],
                "count":    r[2],
                "mastery":  float(r[3]),
                "phoneme":  r[4],
            }
            for r in rows
        ]
    except Exception as exc:
        logger.error("get_recent_errors failed: %s", exc, exc_info=True)
        return []
def get_srs_due_errors(username: str, limit: int = 10) -> list[dict]:
    try:
        with _conn() as conn:
            rows = conn.execute(
                text(
                    "SELECT ExpectedWord, UserSaid, ErrorCount, "
                    "COALESCE(mastery_score, 0.0), COALESCE(phoneme_target, '') "
                    "FROM UserErrors "
                    "WHERE Username=:u "
                    "  AND COALESCE(mastery_score, 0.0) < 0.90 "
                    "  AND (next_review_date IS NULL "
                    "       OR next_review_date <= CURRENT_DATE) "
                    "ORDER BY COALESCE(mastery_score, 0.0) ASC, ErrorCount DESC "
                    "LIMIT :lim OFFSET 0"
                ),
                {"lim": limit, "u": username},
            ).fetchall()
        return [
            {
                "expected": r[0],
                "said":     r[1],
                "count":    r[2],
                "mastery":  float(r[3]),
                "phoneme":  r[4],
            }
            for r in rows
        ]
    except Exception as exc:
        logger.error("get_srs_due_errors failed: %s", exc, exc_info=True)
        return []
@st.cache_data(ttl=30)
def get_top_errors(username: str, limit: int = 5) -> list[dict]:
    try:
        with _conn() as conn:
            rows = conn.execute(
                text(
                    "SELECT ExpectedWord, UserSaid, ErrorCount "
                    "FROM UserErrors WHERE Username=:u "
                    "ORDER BY ErrorCount DESC "
                    "LIMIT :lim OFFSET 0"
                ),
                {"u": username, "lim": limit},
            ).fetchall()
        return [{"expected": r[0], "said": r[1], "count": r[2]} for r in rows]
    except Exception as exc:
        logger.error("get_top_errors failed: %s", exc, exc_info=True)
        return []

def backfill_null_dates() -> int:
    try:
        with _conn() as conn:
            result = conn.execute(
                text(
                    "UPDATE UserErrors SET LastSeen = CURRENT_TIMESTAMP "
                    "WHERE LastSeen IS NULL"
                )
            )
            conn.commit()
            count = result.rowcount
        logger.info("backfill_null_dates: updated %d rows.", count)
        return count
    except Exception as exc:
        logger.error("backfill_null_dates failed: %s", exc, exc_info=True)
        return -1