"""Alembic 迁移链冒烟测试（在真实 MySQL 临时库上执行）。

覆盖三件事：
1. 链完整性：只有一个头版本、头与最新迁移一致、每个修订的
   down_revision 都能回溯到根（无悬挂引用、无分叉链）。
2. 全部迁移脚本可编译：防止迁移文件被改坏后部署流程才暴露。
3. 空库整链执行：迁移脚本在真实 MySQL 临时库上执行 `upgrade head`，
   随后校验表/列/索引与 Base.metadata 模型元数据对齐（模型要求的不允许缺失），
   并确认迁移新增的复合查询索引确实落库。
"""

import secrets
from pathlib import Path
from urllib.parse import quote_plus

from alembic import command
from alembic.config import Config
from alembic.script import ScriptDirectory
from sqlalchemy import create_engine, inspect, text

import web.backend.database as database_module
from tests.support.db import get_mysql_credentials, get_test_engine
from web.backend.database import Base

TESTS_DIR = Path(__file__).resolve().parent
PROJECT_ROOT = TESTS_DIR.parent
VERSIONS_DIR = PROJECT_ROOT / "web" / "backend" / "migrations" / "versions"

HEAD_REVISION = "20261003_0042"

# 迁移新增、但不声明在模型里的复合查询索引。
EXTRA_INDEXES = (
    "ix_douyu_tasks_handbook_scope_id",
    "ix_douyu_tasks_handbook_scope_task_type_id",
    "ix_douyu_tasks_status_finished_at_id",
    "ix_login_tasks_status_finished_at_id",
    # 账号时间线按「账号 + 时间倒序」查，模型里不声明这个复合索引。
    "ix_account_events_account_occurred",
    # CK 搬到账号后，「在途尝试」只能留在登录记录上，巡检/重登每轮按
    # (account_id, attempt_status) 过滤 —— 模型里不声明这个索引。
    "ix_login_tasks_account_attempt_status",
)


def _migration_config() -> Config:
    config = Config(str(PROJECT_ROOT / "alembic.ini"))
    config.set_main_option(
        "script_location", str(PROJECT_ROOT / "web" / "backend" / "migrations")
    )
    return config


class TestMigrationSmoke:
    def test_chain_is_linear_and_head_matches_latest_file(self):
        directory = ScriptDirectory.from_config(_migration_config())

        heads = directory.get_heads()
        assert len(heads) == 1, f"迁移链出现多个头版本（存在分叉）: {heads}"
        assert heads[0] == HEAD_REVISION, f"头版本 {heads[0]} 与最新迁移不一致"

        version_files = sorted(path.name for path in VERSIONS_DIR.glob("*.py"))
        revisions = list(directory.walk_revisions())
        revision_ids = {revision.revision for revision in revisions}
        assert len(revision_ids) == len(version_files), (
            "迁移文件数量与已加载修订数量不一致（存在无法加载的脚本）"
        )
        for revision in revisions:
            if revision.down_revision is not None:
                assert revision.down_revision in revision_ids, (
                    f"{revision.revision} 引用了不存在的父版本 {revision.down_revision}"
                )

    def test_all_migration_scripts_compile(self):
        for path in sorted(VERSIONS_DIR.glob("*.py")):
            source = path.read_text(encoding="utf-8")
            compile(source, str(path), "exec")  # 语法/缩进等编译错误会在此抛出

    def test_full_chain_applies_on_fresh_mysql_and_matches_models(self):
        """空库执行整条迁移链，校验表/列/索引与模型元数据对齐。"""
        creds = get_mysql_credentials()
        mig_db = f"douyu_login_mig_{secrets.token_hex(4)}"
        mig_url = f"mysql+pymysql://{quote_plus(creds['user'])}:{quote_plus(creds['password'])}@{creds['host']}:{creds['port']}/{mig_db}?charset=utf8mb4"

        admin_engine = get_test_engine()
        with admin_engine.begin() as conn:
            conn.execute(
                text(
                    f"CREATE DATABASE `{mig_db}` CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci;"
                )
            )

        original_url = database_module.DATABASE_URL
        try:
            database_module.DATABASE_URL = mig_url
            cfg = _migration_config()
            cfg.set_main_option("sqlalchemy.url", mig_url)
            command.upgrade(cfg, "head")

            inspector = inspect(create_engine(mig_url))
            db_tables = set(inspector.get_table_names())
            assert db_tables

            model_tables = Base.metadata.tables
            missing_tables = set(model_tables) - db_tables
            assert not missing_tables

            all_db_indexes = set()
            for name, table in model_tables.items():
                db_columns = {column["name"] for column in inspector.get_columns(name)}
                model_columns = set(table.columns.keys())
                missing_columns = model_columns - db_columns
                assert not missing_columns

                db_indexes = set()
                for index in inspector.get_indexes(name):
                    index_name = index["name"]
                    if index_name:
                        db_indexes.add(index_name)
                all_db_indexes |= db_indexes
                model_indexes = {index.name for index in table.indexes if index.name}
                missing_indexes = model_indexes - db_indexes
                assert not missing_indexes

            # 迁移新增的复合查询索引（不入模型，但应存在）。
            for index_name in EXTRA_INDEXES:
                assert index_name in all_db_indexes, f"迁移链未创建索引 {index_name}"
        finally:
            database_module.DATABASE_URL = original_url
            with admin_engine.begin() as conn:
                conn.execute(text(f"DROP DATABASE IF EXISTS `{mig_db}`;"))