"""
Database Base Configuration
===========================
CTO-201: Async SQLAlchemy setup

Features:
- SQLAlchemy 2.0 async engine
- PostgreSQL (asyncpg) - 188 PostgreSQL
- Session dependency injection

統帥鐵律 2026-03-23:
- 絕對禁止 SQLite
- 所有 Episodic Memory 必須使用 PostgreSQL
"""

from collections.abc import AsyncGenerator
from contextlib import asynccontextmanager

from sqlalchemy import text
from sqlalchemy.ext.asyncio import (
    AsyncEngine,
    AsyncSession,
    async_sessionmaker,
    create_async_engine,
)
from sqlalchemy.orm import DeclarativeBase

from src.core.config import settings

# =============================================================================
# Base Model
# =============================================================================

class Base(DeclarativeBase):
    """SQLAlchemy declarative base"""
    pass


# =============================================================================
# Engine & Session Factory
# =============================================================================

_engine: AsyncEngine | None = None
_session_factory: async_sessionmaker[AsyncSession] | None = None


def get_engine() -> AsyncEngine:
    """
    Get or create async engine

    統帥鐵律 2026-03-23:
    - 使用 DATABASE_URL (PostgreSQL)
    - 絕對禁止 SQLite
    """
    global _engine
    if _engine is None:
        database_url = settings.DATABASE_URL

        # 統帥鐵律: 禁止 SQLite (AWOOOI 憲法)
        # 🔴 違反此規則必須立即報錯，禁止 fallback
        if "sqlite" in database_url.lower():
            import structlog
            logger = structlog.get_logger(__name__)
            logger.error("sqlite_forbidden", url=database_url)
            raise ValueError(
                "SQLite is FORBIDDEN by AWOOOI Constitution. "
                "Set DATABASE_URL to PostgreSQL: postgresql+asyncpg://user:pass@host:5432/db"
            )

        _engine = create_async_engine(
            database_url,
            echo=settings.DEBUG,
            pool_size=10,
            max_overflow=20,
            pool_pre_ping=True,
        )
    return _engine


def get_session_factory() -> async_sessionmaker[AsyncSession]:
    """Get or create session factory"""
    global _session_factory
    if _session_factory is None:
        _session_factory = async_sessionmaker(
            bind=get_engine(),
            class_=AsyncSession,
            expire_on_commit=False,
            autoflush=False,
        )
    return _session_factory


# =============================================================================
# Dependency Injection
# =============================================================================

async def get_db() -> AsyncGenerator[AsyncSession, None]:
    """
    FastAPI dependency for database session

    Usage:
        @router.get("/items")
        async def get_items(db: AsyncSession = Depends(get_db)):
            ...
    """
    factory = get_session_factory()
    async with factory() as session:
        try:
            yield session
            await session.commit()
        except Exception:
            await session.rollback()
            raise


@asynccontextmanager
async def get_db_context() -> AsyncGenerator[AsyncSession, None]:
    """
    Context manager for database session (non-FastAPI usage)

    Usage:
        async with get_db_context() as db:
            ...
    """
    factory = get_session_factory()
    async with factory() as session:
        try:
            yield session
            await session.commit()
        except Exception:
            await session.rollback()
            raise


# =============================================================================
# Initialization
# =============================================================================

async def init_db() -> None:
    """
    Initialize database tables

    Call this at application startup.
    """
    engine = get_engine()

    # 2026-04-15 ogt: 多 replica 並行啟動競爭修復
    # 問題：單一大 transaction 裡兩個 pod 同時建 table → 其中一個 CREATE INDEX 失敗
    #       PostgreSQL 中 transaction 內任何錯誤導致整個 transaction ROLLBACK
    #       → table + index 全消失 → 下次重啟同樣問題 → 無限 CrashLoop
    # 修法：每個 table 獨立 transaction；先 DROP INDEX IF EXISTS 清殘留孤兒 index；
    #       捕捉 "already exists" 讓並行 pod 優雅跳過
    async with engine.connect() as probe_conn:
        existing = set(await probe_conn.run_sync(
            lambda c: __import__('sqlalchemy', fromlist=['inspect']).inspect(c).get_table_names()
        ))

    for table in Base.metadata.sorted_tables:
        if table.name not in existing:
            try:
                async with engine.begin() as conn:
                    # 先清殘留孤兒 index（前次 CrashLoop 留下的部分狀態）
                    for index in table.indexes:
                        await conn.execute(text(f'DROP INDEX IF EXISTS "{index.name}"'))
                    await conn.run_sync(table.create)
            except Exception as exc:
                if "already exists" in str(exc).lower():
                    pass  # 並行 pod 已建好，忽略
                else:
                    raise

    async with engine.begin() as conn:
        # 2026-04-02 Claude Code: 確保 risklevel enum 包含 'high' 值
        # Phase 23 新增，避免舊 DB 缺少此值導致 InvalidTextRepresentation
        await conn.execute(
            text("""
            DO $$
            BEGIN
                IF NOT EXISTS (
                    SELECT 1 FROM pg_enum
                    WHERE enumtypid = 'risklevel'::regtype
                      AND enumlabel = 'high'
                ) THEN
                    ALTER TYPE risklevel ADD VALUE 'high';
                END IF;
            END
            $$;
            """)
        )

        # 2026-04-09 Claude Sonnet 4.6: Sprint 5R C1 修復 — 批准執行閉環 Telegram 訊息持久化欄位
        # create_all 不做 ALTER，需手動補欄位
        await conn.execute(
            text("""
            ALTER TABLE approval_records
                ADD COLUMN IF NOT EXISTS telegram_message_id INTEGER,
                ADD COLUMN IF NOT EXISTS telegram_chat_id INTEGER;
            """)
        )

        # 2026-04-15 ogt + Claude Sonnet 4.6（亞太）: Phase 3.5 Playbook PostgreSQL 持久化
        # ADR-085: AI 學習成果不可存 Cache — trust_score、EWMA 必須永久保存
        # playbooks 表已存在（15 筆舊資料），補加新欄位
        await conn.execute(
            text("""
            ALTER TABLE playbooks
                ADD COLUMN IF NOT EXISTS trust_score FLOAT NOT NULL DEFAULT 0.3,
                ADD COLUMN IF NOT EXISTS requires_approval_level VARCHAR(20) NOT NULL DEFAULT 'auto',
                ADD COLUMN IF NOT EXISTS stateful_targets JSONB NOT NULL DEFAULT '[]',
                ADD COLUMN IF NOT EXISTS requires_pre_backup BOOLEAN NOT NULL DEFAULT FALSE;
            """)
        )

        # 2026-04-15 ogt + Claude Sonnet 4.6（亞太）: Phase 4 8D 感官升級
        # ADR-084: EvidenceSnapshot 加入 Phase 4 動態異常上下文（anomaly_context）
        await conn.execute(
            text("""
            ALTER TABLE incident_evidence
                ADD COLUMN IF NOT EXISTS anomaly_context JSONB;
            """)
        )

        # 2026-04-15 ogt + Claude Sonnet 4.6（亞太）: Phase 6 自我治理閉環
        # ADR-087: ai_governance_events 不可變 Event Sourcing 表
        # asyncpg 不允許 prepared statement 內多條指令，必須分開 execute
        await conn.execute(text(
            "CREATE INDEX IF NOT EXISTS ix_ai_governance_event_type "
            "ON ai_governance_events (event_type);"
        ))
        await conn.execute(text(
            "CREATE INDEX IF NOT EXISTS ix_ai_governance_triggered_at "
            "ON ai_governance_events (triggered_at);"
        ))
        await conn.execute(text(
            "CREATE INDEX IF NOT EXISTS ix_ai_governance_resolved "
            "ON ai_governance_events (resolved);"
        ))


async def close_db() -> None:
    """
    Close database connections

    Call this at application shutdown.
    """
    global _engine, _session_factory
    if _engine is not None:
        await _engine.dispose()
        _engine = None
        _session_factory = None