#!/usr/bin/env python3
"""
数据库迁移 v5：多租户版本字段 + resource 图片

本次变更：
1. 给 6 张实体表加 version 列（VARCHAR(32) DEFAULT 'v0'）：
   knowledge, resource, requirement, capability, tool, strategy
2. 给 resource 表加 images 列（JSONB DEFAULT '[]'）

注意：经 v4 踩坑后的做法——
- 合并 `NOT NULL DEFAULT` 会挂；拆两步：先 ADD COLUMN DEFAULT，再 SET NOT NULL
- SET NOT NULL 可能因 idle-in-tx 锁冲突失败；失败不致命，DEFAULT 对新行已生效
- 跑 DDL 前先 kill idle-in-tx，防止 ALTER 被 AccessShareLock 阻塞

幂等：反复执行不破坏已有数据。
"""

import os
import time
import psycopg2
from psycopg2.extras import RealDictCursor
from dotenv import load_dotenv

_script_dir = os.path.dirname(os.path.abspath(__file__))
_project_root = os.path.normpath(os.path.join(_script_dir, '..', '..', '..'))
load_dotenv(os.path.join(_project_root, '.env'))


def log(msg):
    print(f"[{time.strftime('%H:%M:%S')}] {msg}", flush=True)


def get_connection():
    conn = psycopg2.connect(
        host=os.getenv('KNOWHUB_DB'),
        port=int(os.getenv('KNOWHUB_PORT', 5432)),
        user=os.getenv('KNOWHUB_USER'),
        password=os.getenv('KNOWHUB_PASSWORD'),
        database=os.getenv('KNOWHUB_DB_NAME'),
        connect_timeout=10
    )
    conn.autocommit = True
    return conn


def column_exists(cursor, table, column):
    cursor.execute(
        "SELECT 1 FROM information_schema.columns WHERE table_name = %s AND column_name = %s",
        (table, column))
    return cursor.fetchone() is not None


def is_not_null(cursor, table, column):
    cursor.execute(
        "SELECT is_nullable FROM information_schema.columns WHERE table_name=%s AND column_name=%s",
        (table, column))
    row = cursor.fetchone()
    return row and row['is_nullable'] == 'NO'


def kill_idle_in_tx(cursor):
    """跑 DDL 前清掉所有 idle in transaction 会话（会阻塞 DDL 等锁）"""
    cursor.execute("""SELECT pid FROM pg_stat_activity
                      WHERE state='idle in transaction' AND pid != pg_backend_pid()
                        AND datname=current_database()""")
    pids = [r['pid'] for r in cursor.fetchall()]
    if pids:
        log(f"  killing {len(pids)} idle-in-tx: {pids}")
        for p in pids:
            cursor.execute("SELECT pg_terminate_backend(%s)", (p,))
        time.sleep(1)
    return len(pids)


# ─── 主流程 ───────────────────────────────────────────────────────────────────

ENTITIES = ['knowledge', 'resource', 'requirement', 'capability', 'tool', 'strategy']


def main():
    log("=" * 60)
    log("KnowHub 迁移 v5: version + resource.images")
    log("=" * 60)

    conn = get_connection()
    cursor = conn.cursor(cursor_factory=RealDictCursor)
    cursor.execute("SET statement_timeout = '30s'")

    # Step 0: 清理可能阻塞 DDL 的会话
    log("\n[0/3] 清理 idle-in-transaction 会话...")
    kill_idle_in_tx(cursor)

    # Step 1: 给每个实体表加 version 列
    log("\n[1/3] 添加 version 列（DEFAULT 'v0'）...")
    for t in ENTITIES:
        if column_exists(cursor, t, 'version'):
            log(f"  {t}.version 已存在，跳过")
            continue
        try:
            cursor.execute(f"ALTER TABLE {t} ADD COLUMN version VARCHAR(32) DEFAULT 'v0'")
            log(f"  ✓ {t}.version 已添加")
        except Exception as e:
            log(f"  ✗ {t}.version 失败: {type(e).__name__}: {str(e)[:150]}")

    # Step 2: 给 resource 加 images 列
    log("\n[2/3] resource.images（JSONB DEFAULT '[]'）...")
    if column_exists(cursor, 'resource', 'images'):
        log("  resource.images 已存在，跳过")
    else:
        try:
            cursor.execute("ALTER TABLE resource ADD COLUMN images JSONB DEFAULT '[]'")
            log("  ✓ resource.images 已添加")
        except Exception as e:
            log(f"  ✗ resource.images 失败: {type(e).__name__}: {str(e)[:150]}")

    # Step 3: 尝试给 version 列设 NOT NULL（非关键，失败可接受）
    log("\n[3/3] 尝试给 version 列加 NOT NULL（失败不致命）...")
    kill_idle_in_tx(cursor)
    for t in ENTITIES:
        if is_not_null(cursor, t, 'version'):
            log(f"  {t}.version 已 NOT NULL")
            continue
        try:
            cursor.execute(f"ALTER TABLE {t} ALTER COLUMN version SET NOT NULL")
            log(f"  ✓ {t}.version SET NOT NULL")
        except Exception as e:
            log(f"  ⚠️ {t}.version SET NOT NULL 未完成: {type(e).__name__}: {str(e)[:120]}")

    # 最终验证
    log("\n" + "=" * 60)
    log("最终状态：")
    log("=" * 60)
    for t in ENTITIES:
        cursor.execute("""SELECT column_default, is_nullable FROM information_schema.columns
                          WHERE table_name=%s AND column_name='version'""", (t,))
        row = cursor.fetchone()
        cursor.execute(f"SELECT COUNT(*) AS c FROM {t}")
        total = cursor.fetchone()['c']
        if row:
            log(f"  {t}: version default={row['column_default']!r}, nullable={row['is_nullable']}, rows={total}")
        else:
            log(f"  {t}: version MISSING, rows={total}")
    cursor.execute("""SELECT column_default FROM information_schema.columns
                      WHERE table_name='resource' AND column_name='images'""")
    row = cursor.fetchone()
    log(f"  resource.images: {'default=' + repr(row['column_default']) if row else 'MISSING'}")

    log("\n迁移完成")
    cursor.close()
    conn.close()


if __name__ == '__main__':
    main()