"""Git 练习场：在临时目录里自动演示并验证常用操作。

覆盖：功能分支 + 合并、rebase 整理、revert 撤销已推送的提交、reset 后用 reflog 找回、cherry-pick 热修复。
运行：python lab.py（只需要本机安装 git，不会改动你的任何仓库）
"""
import subprocess
import tempfile
from pathlib import Path


def git(repo: Path, *args: str) -> str:
    out = subprocess.run(["git", *args], cwd=repo, capture_output=True, text=True,
                         env={"GIT_AUTHOR_NAME": "dev", "GIT_AUTHOR_EMAIL": "dev@example.com",
                              "GIT_COMMITTER_NAME": "dev", "GIT_COMMITTER_EMAIL": "dev@example.com",
                              "HOME": str(repo), "PATH": "/usr/bin:/bin:/usr/local/bin"})
    if out.returncode != 0:
        raise RuntimeError(f"git {' '.join(args)} 失败：{out.stderr}")
    return out.stdout.strip()


def commit(repo: Path, name: str, content: str, msg: str) -> str:
    (repo / name).write_text(content)
    git(repo, "add", name)
    git(repo, "commit", "-q", "-m", msg)
    return git(repo, "rev-parse", "--short", "HEAD")


def log(repo: Path, ref: str = "HEAD") -> list[str]:
    return git(repo, "log", "--format=%s", ref).splitlines()


def main() -> None:
    with tempfile.TemporaryDirectory() as tmp:
        repo = Path(tmp)
        git(repo, "init", "-q", "-b", "main")
        commit(repo, "app.txt", "v1\n", "feat: 初始化项目")

        # 1. 功能分支开发，期间 main 有新提交
        git(repo, "switch", "-q", "-c", "feat/login")
        commit(repo, "login.txt", "login\n", "feat(login): 登录表单")
        commit(repo, "login.txt", "login\nvalidate\n", "fix: 拼写")
        git(repo, "switch", "-q", "main")
        commit(repo, "readme.txt", "readme\n", "docs: 说明文档")

        # 2. 在功能分支上 rebase 到最新 main：历史变成一条直线，不产生合并提交
        git(repo, "switch", "-q", "feat/login")
        git(repo, "rebase", "-q", "main")
        assert log(repo)[:3] == ["fix: 拼写", "feat(login): 登录表单", "docs: 说明文档"]
        print("rebase 后：", log(repo))

        # 3. 合并回 main（--no-ff 保留一个合并提交，记录“这里合入了一个功能”）
        git(repo, "switch", "-q", "main")
        git(repo, "merge", "-q", "--no-ff", "feat/login", "-m", "merge: 登录功能")
        assert log(repo)[0] == "merge: 登录功能"

        # 4. 已推送的错误提交：用 revert 生成一个反向提交，不改写历史
        bad = commit(repo, "app.txt", "v2-bug\n", "feat: 有问题的改动")
        git(repo, "revert", "--no-edit", bad)
        assert (repo / "app.txt").read_text() == "v1\n"
        assert log(repo)[0].startswith('Revert "feat: 有问题的改动"')
        print("revert 后 app.txt =", (repo / "app.txt").read_text().strip())

        # 5. 误用 reset --hard 丢掉了提交，用 reflog 找回
        lost = commit(repo, "important.txt", "重要数据\n", "feat: 重要改动")
        git(repo, "reset", "-q", "--hard", "HEAD~1")
        assert not (repo / "important.txt").exists()
        reflog = git(repo, "reflog", "--format=%h %gs")
        found = next(line.split()[0] for line in reflog.splitlines() if "feat: 重要改动" in line)
        assert found == lost
        git(repo, "reset", "-q", "--hard", found)
        assert (repo / "important.txt").read_text() == "重要数据\n"
        print("reflog 找回提交", found)

        # 6. 热修复：在 release 分支修复后 cherry-pick 回 main
        git(repo, "switch", "-q", "-c", "release/1.0", "HEAD~1")
        fix = commit(repo, "hotfix.txt", "fix\n", "fix: 线上紧急修复")
        git(repo, "switch", "-q", "main")
        git(repo, "cherry-pick", fix)
        assert log(repo)[0] == "fix: 线上紧急修复" and (repo / "hotfix.txt").exists()
        print("cherry-pick 后 main：", log(repo)[:2])
    print("Git 练习全部通过")


if __name__ == "__main__":
    main()