"""Esquema y gestión de la base de datos SQLite."""

import sqlite3
import threading
from pathlib import Path
from typing import Optional
from datetime import datetime
from ..constants import DB_PATH

# Espera máxima (s) por un lock de SQLite antes de fallar. Con WAL + busy_timeout los
# lectores (UI cada 5s) y escritores (workers + file_watcher) dejan de chocar con
# "database is locked": esperan en vez de fallar de inmediato.
_SQLITE_TIMEOUT_SECONDS = 30.0
_SQLITE_BUSY_TIMEOUT_MS = 5000


class DatabaseManager:
    """Gestor de la base de datos SQLite."""

    def __init__(self, db_path: Optional[Path] = None):
        """
        Inicializa el gestor de base de datos.

        Args:
            db_path: Ruta a la base de datos (usa DB_PATH por defecto)
        """
        self.db_path = db_path or DB_PATH
        self.db_path.parent.mkdir(parents=True, exist_ok=True)
        # Serializa las escrituras del propio proceso (varios workers + file_watcher) para
        # eliminar las colisiones write-write; WAL cubre la concurrencia lectura/escritura.
        self._write_lock = threading.Lock()
        self._initialize_schema()

    def get_connection(self) -> sqlite3.Connection:
        """Obtiene una conexión a SQLite con protecciones de concurrencia (WAL + timeouts)."""
        conn = sqlite3.connect(
            str(self.db_path), check_same_thread=False, timeout=_SQLITE_TIMEOUT_SECONDS
        )
        conn.row_factory = sqlite3.Row
        # WAL: lectores concurrentes con un escritor (persistente en el archivo, idempotente).
        conn.execute("PRAGMA journal_mode=WAL")
        conn.execute(f"PRAGMA busy_timeout={_SQLITE_BUSY_TIMEOUT_MS}")
        conn.execute("PRAGMA synchronous=NORMAL")
        return conn
    
    def _initialize_schema(self):
        """Crea las tablas si no existen."""
        conn = self.get_connection()
        try:
            cursor = conn.cursor()

            # Tabla de jobs
            cursor.execute("""
                CREATE TABLE IF NOT EXISTS jobs (
                    job_id TEXT PRIMARY KEY,
                    created_at TEXT NOT NULL,
                    updated_at TEXT NOT NULL,
                    source_path TEXT NOT NULL,
                    source_name TEXT NOT NULL,
                    source_hash TEXT,
                    node_name TEXT,
                    db_name TEXT,
                    status TEXT NOT NULL,
                    attempts INTEGER DEFAULT 0,
                    last_error TEXT,
                    started_at TEXT,
                    finished_at TEXT,
                    total_ms INTEGER,
                    extract_ms INTEGER,
                    restore_ms INTEGER,
                    filelist_ms INTEGER,
                    purged_at TEXT
                )
            """)
            
            # Tabla de pasos de jobs
            cursor.execute("""
                CREATE TABLE IF NOT EXISTS job_steps (
                    id INTEGER PRIMARY KEY AUTOINCREMENT,
                    job_id TEXT NOT NULL,
                    step TEXT NOT NULL,
                    started_at TEXT NOT NULL,
                    finished_at TEXT,
                    duration_ms INTEGER,
                    exit_code INTEGER,
                    stdout TEXT,
                    stderr TEXT,
                    error TEXT,
                    FOREIGN KEY (job_id) REFERENCES jobs(job_id)
                )
            """)
            
            # Tabla de nodos (mapeo node_name -> db_name)
            cursor.execute("""
                CREATE TABLE IF NOT EXISTS nodes (
                    node_name TEXT PRIMARY KEY,
                    db_name TEXT NOT NULL,
                    active INTEGER DEFAULT 1,
                    notes TEXT,
                    updated_at TEXT NOT NULL
                )
            """)
            
            # Tabla de eventos
            cursor.execute("""
                CREATE TABLE IF NOT EXISTS events (
                    id INTEGER PRIMARY KEY AUTOINCREMENT,
                    created_at TEXT NOT NULL,
                    level TEXT NOT NULL,
                    job_id TEXT,
                    message TEXT NOT NULL,
                    FOREIGN KEY (job_id) REFERENCES jobs(job_id)
                )
            """)
            
            # Tabla de configuración
            cursor.execute("""
                CREATE TABLE IF NOT EXISTS config (
                    key TEXT PRIMARY KEY,
                    value TEXT NOT NULL,
                    updated_at TEXT NOT NULL
                )
            """)
            
            # Migración idempotente: columna purged_at para marcar los respaldos que la
            # retención ya borró del disco. Se conserva la fila (historial/stats/UI) y solo
            # se anota que su archivo físico dejó de existir. Backward-compatible: columna
            # nullable que las versiones anteriores de la app simplemente ignoran.
            cursor.execute("PRAGMA table_info(jobs)")
            job_columns = {row[1] for row in cursor.fetchall()}
            if "purged_at" not in job_columns:
                cursor.execute("ALTER TABLE jobs ADD COLUMN purged_at TEXT")

            # Índices
            cursor.execute("CREATE INDEX IF NOT EXISTS idx_jobs_status ON jobs(status)")
            cursor.execute("CREATE INDEX IF NOT EXISTS idx_jobs_created ON jobs(created_at)")
            # Soporta la retención por nodo (GROUP BY node_name + filtro por finished_at).
            cursor.execute(
                "CREATE INDEX IF NOT EXISTS idx_jobs_node_finished "
                "ON jobs(node_name, finished_at)"
            )
            cursor.execute("CREATE INDEX IF NOT EXISTS idx_events_created ON events(created_at)")
            cursor.execute("CREATE INDEX IF NOT EXISTS idx_events_job ON events(job_id)")
            cursor.execute("CREATE INDEX IF NOT EXISTS idx_job_steps_job ON job_steps(job_id)")

            conn.commit()
        finally:
            conn.close()

    def execute(self, query: str, params: tuple = ()) -> sqlite3.Cursor:
        """Ejecuta una escritura, serializada por lock de proceso y con conexión cerrada."""
        with self._write_lock:
            conn = self.get_connection()
            try:
                cursor = conn.cursor()
                cursor.execute(query, params)
                conn.commit()
                return cursor
            finally:
                conn.close()

    def fetchone(self, query: str, params: tuple = ()) -> Optional[sqlite3.Row]:
        """Ejecuta una consulta y devuelve una fila."""
        conn = self.get_connection()
        try:
            cursor = conn.cursor()
            cursor.execute(query, params)
            return cursor.fetchone()
        finally:
            conn.close()

    def fetchall(self, query: str, params: tuple = ()) -> list[sqlite3.Row]:
        """Ejecuta una consulta y devuelve todas las filas."""
        conn = self.get_connection()
        try:
            cursor = conn.cursor()
            cursor.execute(query, params)
            return cursor.fetchall()
        finally:
            conn.close()


# Instancia global
db = DatabaseManager()