#!/usr/bin/env python3
"""Export the Python gateway SQLAlchemy schema as a reviewable Markdown dictionary.

This is an offline migration-development tool. It is not part of the Go runtime.
"""

from __future__ import annotations

import argparse
import importlib
import sys
from pathlib import Path


CURRENT_TARGETS = {
    "departments": "gateway.departments（已落地）",
    "providers": "gateway.providers + gateway.provider_models（已落地，models 拆表）",
    "users": "gateway.portal_users（已落地）",
    "virtual_keys": "gateway.api_keys（已落地，字段需转换）",
    "admin_accounts": "gateway.admin_accounts（已落地）",
    "audit_logs": "gateway.audit_events（已落地，不迁移无限长正文）",
}


def default_text(column) -> str:
    value = column.default
    if value is None:
        return "—"
    argument = value.arg
    if callable(argument):
        return getattr(argument, "__name__", "callable")
    return str(argument).replace("|", "\\|")


def render(legacy_root: Path) -> str:
    sys.path.insert(0, str(legacy_root))
    db = importlib.import_module("app.db")
    tables = [table for name, table in sorted(db.Base.metadata.tables.items()) if name != "audit_log_views"]

    lines = [
        "# 旧 Python 网关数据字典与 ID 迁移映射",
        "",
        "> 由 `scripts/export_legacy_dictionary.py` 从旧工程 SQLAlchemy metadata 生成。",
        "> `audit_log_views` 是兼容查询投影，不作为独立持久化实体，因此这里统计 38 个实体。",
        "",
        "## 映射约定",
        "",
        "- 旧整数主键统一通过 `gateway.legacy_id_mappings` 映射为 UUID，不在新业务表保留双主键。",
        "- UUID 使用固定 namespace 的 UUIDv5 生成，输入为 `source_system/entity_type/legacy_id`，重复导入保持幂等。",
        "- 外键迁移必须先查映射表；缺失映射时整批失败，不允许写入悬空引用。",
        "- 旧密文不能直接复用：Provider、TOTP、内部服务 Key 等敏感字段在导入时解密后用新用途标签重新加密。",
        "- `audit_logs` 的完整请求/响应正文不进入新库，只迁移受长度约束的预览与结构化元数据。",
        "",
        "## 实体去向",
        "",
        "| 旧表 | 新域/目标 | 状态 |",
        "|---|---|---|",
    ]
    for table in tables:
        target = CURRENT_TARGETS.get(table.name, "对应 M2–M4 领域表")
        status = "已建表，待批量导入器" if table.name in CURRENT_TARGETS else "已登记，随对应里程碑建表"
        lines.append(f"| `{table.name}` | {target} | {status} |")

    lines.extend(["", "## 字段字典", ""])
    for table in tables:
        lines.extend([
            f"### `{table.name}`",
            "",
            "| 字段 | 旧类型 | 可空 | 默认值 | 键/引用 |",
            "|---|---|---:|---|---|",
        ])
        for column in table.columns:
            flags = []
            if column.primary_key:
                flags.append("PK")
            if column.unique:
                flags.append("UNIQUE")
            flags.extend(f"FK → `{fk.target_fullname}`" for fk in column.foreign_keys)
            lines.append(
                f"| `{column.name}` | `{column.type}` | {'是' if column.nullable else '否'} | "
                f"`{default_text(column)}` | {'；'.join(flags) or '—'} |"
            )
        lines.append("")
    return "\n".join(lines).rstrip() + "\n"


def main() -> None:
    parser = argparse.ArgumentParser()
    parser.add_argument("--legacy-root", type=Path, required=True)
    parser.add_argument("--output", type=Path, required=True)
    args = parser.parse_args()
    args.output.parent.mkdir(parents=True, exist_ok=True)
    args.output.write_text(render(args.legacy_root.resolve()), encoding="utf-8")


if __name__ == "__main__":
    main()