from __future__ import annotations

import sqlite3
from contextlib import suppress
from pathlib import Path
from typing import Iterable

SQLITE_BUSY_TIMEOUT_MS = 30000
RESOLVER_STATS_DB_FILENAME = "resolver_stats.db"


SCHEMA_STATEMENTS = [
    """
    CREATE TABLE IF NOT EXISTS resolver_source_stats (
        origin_source TEXT NOT NULL,
        candidate_source TEXT NOT NULL,
        attempt_count INTEGER NOT NULL DEFAULT 0,
        resolve_success_count INTEGER NOT NULL DEFAULT 0,
        created_at TEXT DEFAULT CURRENT_TIMESTAMP,
        updated_at TEXT DEFAULT CURRENT_TIMESTAMP,
        last_attempt_at TEXT,
        last_success_at TEXT,
        PRIMARY KEY(origin_source, candidate_source)
    )
    """,
    """
    CREATE INDEX IF NOT EXISTS idx_resolver_source_stats_origin_source
    ON resolver_source_stats (origin_source)
    """,
]


def default_resolver_stats_db_path(db_path: str | Path) -> Path:
    return Path(db_path).parent / RESOLVER_STATS_DB_FILENAME


def connect_resolver_stats_database(db_path: str | Path) -> sqlite3.Connection:
    path = Path(db_path)
    path.parent.mkdir(parents=True, exist_ok=True)
    conn = sqlite3.connect(path, timeout=SQLITE_BUSY_TIMEOUT_MS / 1000)
    conn.row_factory = sqlite3.Row
    conn.execute(f"PRAGMA busy_timeout = {SQLITE_BUSY_TIMEOUT_MS}")
    with suppress(sqlite3.OperationalError):
        conn.execute("PRAGMA journal_mode = WAL")
    with suppress(sqlite3.OperationalError):
        conn.execute("PRAGMA synchronous = NORMAL")
    return conn


def initialize_resolver_stats_database(db_path: str | Path) -> sqlite3.Connection:
    conn = connect_resolver_stats_database(db_path)
    for statement in SCHEMA_STATEMENTS:
        conn.execute(statement)
    conn.commit()
    return conn


class ResolverStatsRepository:
    def __init__(self, db_path: str | Path):
        self.db_path = Path(db_path)
        conn = initialize_resolver_stats_database(self.db_path)
        conn.close()

    def record_fallback_result(
        self,
        origin_source: str,
        candidate_source: str,
        *,
        succeeded: bool,
    ) -> None:
        conn = connect_resolver_stats_database(self.db_path)
        try:
            conn.execute(
                """
                INSERT INTO resolver_source_stats (
                    origin_source,
                    candidate_source,
                    attempt_count,
                    resolve_success_count,
                    created_at,
                    updated_at,
                    last_attempt_at,
                    last_success_at
                )
                VALUES (
                    ?, ?, 1, ?,
                    CURRENT_TIMESTAMP, CURRENT_TIMESTAMP, CURRENT_TIMESTAMP,
                    CASE WHEN ? THEN CURRENT_TIMESTAMP ELSE NULL END
                )
                ON CONFLICT(origin_source, candidate_source) DO UPDATE SET
                    attempt_count = attempt_count + 1,
                    resolve_success_count = (
                        resolve_success_count + excluded.resolve_success_count
                    ),
                    updated_at = CURRENT_TIMESTAMP,
                    last_attempt_at = CURRENT_TIMESTAMP,
                    last_success_at = CASE
                        WHEN excluded.resolve_success_count > 0
                        THEN CURRENT_TIMESTAMP
                        ELSE last_success_at
                    END
                """,
                (
                    origin_source,
                    candidate_source,
                    int(succeeded),
                    int(succeeded),
                ),
            )
            conn.commit()
        finally:
            conn.close()

    def rank_fallback_sources(
        self,
        origin_source: str,
        fallback_sources: Iterable[str],
        *,
        warmup_attempts: int = 1000,
    ) -> list[str]:
        sources = list(fallback_sources)
        if len(sources) <= 1:
            return sources

        conn = connect_resolver_stats_database(self.db_path)
        try:
            if warmup_attempts > 0:
                row = conn.execute(
                    """
                    SELECT COALESCE(SUM(attempt_count), 0) AS total_attempt_count
                    FROM resolver_source_stats
                    WHERE origin_source = ?
                    """,
                    (origin_source,),
                ).fetchone()
                total_attempt_count = int(row["total_attempt_count"] if row else 0)
                if total_attempt_count < warmup_attempts:
                    return sources

            placeholders = ", ".join("?" for _ in sources)
            rows = conn.execute(
                f"""
                SELECT candidate_source, attempt_count, resolve_success_count
                FROM resolver_source_stats
                WHERE origin_source = ? AND candidate_source IN ({placeholders})
                """,
                (origin_source, *sources),
            ).fetchall()
        finally:
            conn.close()

        stats_by_source = {
            str(row["candidate_source"]): (
                int(row["attempt_count"]),
                int(row["resolve_success_count"]),
            )
            for row in rows
        }
        order_index = {source: idx for idx, source in enumerate(sources)}

        def _sort_key(source: str) -> tuple[float, int]:
            attempts, successes = stats_by_source.get(source, (0, 0))
            smoothed_success_rate = (successes + 1) / (attempts + 2)
            return (-smoothed_success_rate, order_index[source])

        return sorted(sources, key=_sort_key)