"""Alembic 迁移链冒烟测试（不依赖真实 MySQL）。

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：迁移脚本自带方言防护（MySQL 专属 DDL 有 _is_mysql()
   之类分支），整条链可在 SQLite 上真实执行 `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 tempfile
from pathlib import Path

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

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

HEAD_REVISION = "20260830_0031"

# 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",
)


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_sqlite_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。"""
        from web.backend.database import Base
        import web.backend.database as database_module

        original_url = database_module.DATABASE_URL
        with tempfile.TemporaryDirectory() as tmp:
            db_path = Path(tmp) / "migrate.db"
            try:
                # env.py 会用模块级 DATABASE_URL 覆盖配置里的 sqlalchemy.url。
                database_module.DATABASE_URL = f"sqlite:///{db_path}"
                command.upgrade(_migration_config(), "head")

                inspector = inspect(create_engine(f"sqlite:///{db_path}"))
                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 = {
                        index["name"]
                        for index in inspector.get_indexes(name)
                        if not index["name"].startswith("sqlite_autoindex")
                    }
                    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