"""数据字典服务 — 通过 DBConnector 连接数据源获取元数据。"""
import re
from typing import List, Dict, Any, Optional

from sqlalchemy import select
from sqlalchemy.ext.asyncio import AsyncSession

from app.models.instance import Instance
from app.services.db_connector import DBConnector
from app.core.crypto import decrypt_password


async def _get_instance(session: AsyncSession, instance_id: int) -> Instance:
    """根据 ID 查询实例，解密密码后返回。"""
    result = await session.execute(select(Instance).where(Instance.id == instance_id))
    instance = result.scalar_one_or_none()
    if not instance:
        return None
    instance.password = decrypt_password(instance.password)
    return instance


async def list_databases(session: AsyncSession, instance_id: int) -> Optional[List[str]]:
    """获取实例的数据库列表。"""
    instance = await _get_instance(session, instance_id)
    if not instance:
        return None

    if instance.db_type == "mysql":
        qr = await DBConnector.execute_query(
            instance, None, "SHOW DATABASES", user_id=0
        )
        system_dbs = {"information_schema", "mysql", "performance_schema", "sys"}
        return [r.get("Database", r.get("database", "")) for r in qr.rows
                if r.get("Database", r.get("database", "")) not in system_dbs]
    elif instance.db_type in ("postgres", "postgresql"):
        qr = await DBConnector.execute_query(
            instance, "postgres",
            "SELECT datname FROM pg_database WHERE datistemplate = false",
            user_id=0,
        )
        return [r.get("datname", "") for r in qr.rows]
    elif instance.db_type == "sqlite":
        return [instance.database or "main"]
    else:
        return []


async def list_tables(
    session: AsyncSession, instance_id: int, database: str
) -> List[str]:
    """获取指定数据库的表名列表。"""
    instance = await _get_instance(session, instance_id)
    if not instance:
        return []

    if instance.db_type == "mysql":
        sql = (
            "SELECT TABLE_NAME FROM information_schema.TABLES "
            "WHERE TABLE_SCHEMA = '" + database + "' AND TABLE_TYPE = 'BASE TABLE'"
        )
        qr = await DBConnector.execute_query(instance, database, sql, user_id=0)
        return [r.get("TABLE_NAME", "") for r in qr.rows]
    elif instance.db_type in ("postgres", "postgresql"):
        sql = "SELECT tablename FROM pg_tables WHERE schemaname = 'public'"
        qr = await DBConnector.execute_query(instance, database, sql, user_id=0)
        return [r.get("tablename", "") for r in qr.rows]
    elif instance.db_type == "sqlite":
        sql = "SELECT name FROM sqlite_master WHERE type='table'"
        qr = await DBConnector.execute_query(instance, None, sql, user_id=0)
        return [r.get("name", "") for r in qr.rows]
    else:
        return []


async def get_table_detail(
    session: AsyncSession, instance_id: int, database: str, table_name: str
) -> Dict[str, Any]:
    """获取表详情: columns / indexes / create_ddl / row_count。"""
    instance = await _get_instance(session, instance_id)
    if not instance:
        return {}

    columns = []
    indexes = []
    create_ddl = ""
    row_count = 0

    if instance.db_type == "mysql":
        # Columns
        col_sql = (
            "SELECT COLUMN_NAME as Field, COLUMN_TYPE as Type, "
            "IS_NULLABLE as `Null`, COLUMN_KEY as `Key`, "
            "COLUMN_DEFAULT as `Default`, EXTRA as Extra, "
            "COLUMN_COMMENT as Comment "
            "FROM information_schema.COLUMNS "
            "WHERE TABLE_SCHEMA = '" + database + "' "
            "AND TABLE_NAME = '" + table_name + "' "
            "ORDER BY ORDINAL_POSITION"
        )
        col_qr = await DBConnector.execute_query(instance, database, col_sql, user_id=0)
        columns = col_qr.rows

        # Indexes
        idx_sql = "SHOW INDEX FROM `" + table_name + "`"
        idx_qr = await DBConnector.execute_query(instance, database, idx_sql, user_id=0)
        # Group by index name
        idx_map = {}
        for r in idx_qr.rows:
            idx_name = r.get("Key_name", "")
            if idx_name not in idx_map:
                idx_map[idx_name] = {
                    "name": idx_name,
                    "columns": [],
                    "non_unique": r.get("Non_unique", 1),
                    "index_type": r.get("Index_type", "BTREE"),
                }
            idx_map[idx_name]["columns"].append(r.get("Column_name", ""))
        indexes = list(idx_map.values())

        # Create DDL
        ddl_sql = "SHOW CREATE TABLE `" + table_name + "`"
        ddl_qr = await DBConnector.execute_query(instance, database, ddl_sql, user_id=0)
        if ddl_qr.rows:
            create_ddl = ddl_qr.rows[0].get("Create Table", "")

        # Row count
        cnt_sql = (
            "SELECT TABLE_ROWS FROM information_schema.TABLES "
            "WHERE TABLE_SCHEMA = '" + database + "' "
            "AND TABLE_NAME = '" + table_name + "'"
        )
        cnt_qr = await DBConnector.execute_query(instance, database, cnt_sql, user_id=0)
        if cnt_qr.rows:
            row_count = cnt_qr.rows[0].get("TABLE_ROWS", 0)

    elif instance.db_type in ("postgres", "postgresql"):
        # Columns
        col_sql = (
            "SELECT column_name as Field, data_type as Type, "
            "is_nullable as \"Null\", column_default as \"Default\", "
            "'' as \"Key\", '' as Extra "
            "FROM information_schema.columns "
            "WHERE table_schema = 'public' "
            "AND table_name = '" + table_name + "' "
            "ORDER BY ordinal_position"
        )
        col_qr = await DBConnector.execute_query(instance, database, col_sql, user_id=0)
        columns = col_qr.rows

        # Indexes
        idx_sql = (
            "SELECT indexname as name, indexdef as definition "
            "FROM pg_indexes "
            "WHERE schemaname = 'public' AND tablename = '" + table_name + "'"
        )
        idx_qr = await DBConnector.execute_query(instance, database, idx_sql, user_id=0)
        indexes = idx_qr.rows

        # Create DDL — best effort via pg_dump not available; use a placeholder
        create_ddl = "-- PostgreSQL DDL via pg_indexes:\n"
        for idx in idx_qr.rows:
            create_ddl += idx.get("definition", "") + ";\n"

        # Row count
        cnt_sql = "SELECT count(*) as cnt FROM \"" + table_name + "\""
        try:
            cnt_qr = await DBConnector.execute_query(instance, database, cnt_sql, user_id=0)
            if cnt_qr.rows:
                row_count = cnt_qr.rows[0].get("cnt", 0)
        except Exception:
            row_count = -1

    elif instance.db_type == "sqlite":
        # Columns
        col_sql = "PRAGMA table_info('" + table_name + "')"
        col_qr = await DBConnector.execute_query(instance, None, col_sql, user_id=0)
        columns = []
        for r in col_qr.rows:
            columns.append({
                "Field": r.get("name", ""),
                "Type": r.get("type", ""),
                "Null": "YES" if r.get("notnull", 0) == 0 else "NO",
                "Key": "PRI" if r.get("pk", 0) == 1 else "",
                "Default": r.get("dflt_value", ""),
                "Extra": "",
            })

        # Indexes
        idx_sql = "PRAGMA index_list('" + table_name + "')"
        idx_qr = await DBConnector.execute_query(instance, None, idx_sql, user_id=0)
        indexes = []
        for r in idx_qr.rows:
            indexes.append({
                "name": r.get("name", ""),
                "unique": r.get("unique", 0),
            })

        # Create DDL
        ddl_sql = (
            "SELECT sql FROM sqlite_master WHERE type='table' AND name='"
            + table_name + "'"
        )
        ddl_qr = await DBConnector.execute_query(instance, None, ddl_sql, user_id=0)
        if ddl_qr.rows:
            create_ddl = ddl_qr.rows[0].get("sql", "")

        # Row count
        cnt_sql = "SELECT count(*) as cnt FROM '" + table_name + "'"
        try:
            cnt_qr = await DBConnector.execute_query(instance, None, cnt_sql, user_id=0)
            if cnt_qr.rows:
                row_count = cnt_qr.rows[0].get("cnt", 0)
        except Exception:
            row_count = -1

    return {
        "columns": columns,
        "indexes": indexes,
        "create_ddl": create_ddl,
        "row_count": row_count,
    }


async def export_dictionary(
    session: AsyncSession, instance_id: int, database: str
) -> List[Dict[str, Any]]:
    """导出整个数据库的表结构信息。"""
    tables = await list_tables(session, instance_id, database)
    result = []
    for tbl in tables:
        detail = await get_table_detail(session, instance_id, database, tbl)
        result.append({
            "table_name": tbl,
            "columns": detail.get("columns", []),
            "indexes": detail.get("indexes", []),
            "create_ddl": detail.get("create_ddl", ""),
            "row_count": detail.get("row_count", 0),
        })
    return result