"""Persistent chat message store backed by SQLite.

Provides the same API as the original in-memory MessageLog so all callers
(dashboard routes, chat_api, thinking, briefing) work without changes.

Data lives in ``data/chat.db`` — survives server restarts.
A configurable retention policy (default 500 messages) keeps the DB lean.
"""

import sqlite3
import threading
from collections.abc import Generator
from contextlib import closing, contextmanager
from dataclasses import dataclass
from pathlib import Path

# ── Data dir — resolved relative to repo root (three levels up from this file) ──
_REPO_ROOT = Path(__file__).resolve().parents[3]
DB_PATH: Path = _REPO_ROOT / "data" / "chat.db"

# Maximum messages to retain (oldest pruned on append)
MAX_MESSAGES: int = 500


@dataclass
class Message:
    role: str  # "user" | "agent" | "error"
    content: str
    timestamp: str
    source: str = "browser"  # "browser" | "api" | "telegram" | "discord" | "system"


@contextmanager
def _get_conn(db_path: Path | None = None) -> Generator[sqlite3.Connection, None, None]:
    """Open (or create) the chat database and ensure schema exists."""
    path = db_path or DB_PATH
    path.parent.mkdir(parents=True, exist_ok=True)
    with closing(sqlite3.connect(str(path), check_same_thread=False)) as conn:
        conn.row_factory = sqlite3.Row
        conn.execute("PRAGMA journal_mode=WAL")
        conn.execute("""
            CREATE TABLE IF NOT EXISTS chat_messages (
                id        INTEGER PRIMARY KEY AUTOINCREMENT,
                role      TEXT NOT NULL,
                content   TEXT NOT NULL,
                timestamp TEXT NOT NULL,
                source    TEXT NOT NULL DEFAULT 'browser'
            )
        """)
        conn.commit()
        yield conn


class MessageLog:
    """SQLite-backed chat history — drop-in replacement for the old in-memory list."""

    def __init__(self, db_path: Path | None = None) -> None:
        self._db_path = db_path or DB_PATH
        self._lock = threading.Lock()
        self._conn: sqlite3.Connection | None = None

    # Lazy connection — opened on first use, not at import time.
    @contextmanager
    def _get_conn(self) -> Generator[sqlite3.Connection, None, None]:
        path = self._db_path or DB_PATH
        with closing(sqlite3.connect(str(path), check_same_thread=False)) as conn:
            conn.row_factory = sqlite3.Row
            yield conn
        if self._conn is None:
            # Open a persistent connection for the class instance
            path = self._db_path or DB_PATH
            path.parent.mkdir(parents=True, exist_ok=True)
            conn = sqlite3.connect(str(path), check_same_thread=False)
            conn.row_factory = sqlite3.Row
            conn.execute("PRAGMA journal_mode=WAL")
            conn.execute("""
                CREATE TABLE IF NOT EXISTS chat_messages (
                    id        INTEGER PRIMARY KEY AUTOINCREMENT,
                    role      TEXT NOT NULL,
                    content   TEXT NOT NULL,
                    timestamp TEXT NOT NULL,
                    source    TEXT NOT NULL DEFAULT 'browser'
                )
            """)
            conn.commit()
            self._conn = conn
        return self._conn

    def append(self, role: str, content: str, timestamp: str, source: str = "browser") -> None:
        with self._lock:
            conn = self._ensure_conn()
            conn.execute(
                "INSERT INTO chat_messages (role, content, timestamp, source) VALUES (?, ?, ?, ?)",
                (role, content, timestamp, source),
            )
            conn.commit()
            self._prune(conn)

    def all(self) -> list[Message]:
        with self._lock:
            conn = self._ensure_conn()
            rows = conn.execute(
                "SELECT role, content, timestamp, source FROM chat_messages ORDER BY id"
            ).fetchall()
        return [
            Message(
                role=r["role"], content=r["content"], timestamp=r["timestamp"], source=r["source"]
            )
            for r in rows
        ]

    def recent(self, limit: int = 50) -> list[Message]:
        """Return the *limit* most recent messages (oldest-first)."""
        with self._lock:
            conn = self._ensure_conn()
            rows = conn.execute(
                "SELECT role, content, timestamp, source FROM chat_messages "
                "ORDER BY id DESC LIMIT ?",
                (limit,),
            ).fetchall()
        return [
            Message(
                role=r["role"], content=r["content"], timestamp=r["timestamp"], source=r["source"]
            )
            for r in reversed(rows)
        ]

    def clear(self) -> None:
        with self._lock:
            conn = self._ensure_conn()
            conn.execute("DELETE FROM chat_messages")
            conn.commit()

    def _prune(self, conn: sqlite3.Connection) -> None:
        """Keep at most MAX_MESSAGES rows, deleting the oldest."""
        count = conn.execute("SELECT COUNT(*) FROM chat_messages").fetchone()[0]
        if count > MAX_MESSAGES:
            excess = count - MAX_MESSAGES
            conn.execute(
                "DELETE FROM chat_messages WHERE id IN "
                "(SELECT id FROM chat_messages ORDER BY id LIMIT ?)",
                (excess,),
            )
            conn.commit()

    def close(self) -> None:
        if self._conn is not None:
            self._conn.close()
            self._conn = None

    def __len__(self) -> int:
        with self._lock:
            conn = self._ensure_conn()
            return conn.execute("SELECT COUNT(*) FROM chat_messages").fetchone()[0]


# Module-level singleton shared across the app
message_log = MessageLog()