from __future__ import annotations

from dataclasses import dataclass
from pathlib import Path
import re
import shlex
import subprocess
from urllib.parse import urlparse


class GitCommandError(RuntimeError):
    def __init__(self, args: list[str], returncode: int, stdout: str, stderr: str) -> None:
        cmd = " ".join(shlex.quote(x) for x in args)
        message = f"git command failed ({returncode}): {cmd}\nstdout:\n{stdout}\nstderr:\n{stderr}"
        super().__init__(message)
        self.args_list = args
        self.returncode = returncode
        self.stdout = stdout
        self.stderr = stderr


@dataclass(frozen=True)
class SyncResult:
    previous_commit: str | None
    commit_hash: str
    changed: bool


class GitManager:
    def __init__(self, remote_url: str, mirror_path: Path) -> None:
        self.remote_url = remote_url
        self.mirror_path = mirror_path

    def ensure_mirror(self) -> None:
        if not self.remote_url:
            raise ValueError("git_remote_url is required")

        self._allow_local_remote_if_needed()

        head_file = self.mirror_path / "HEAD"
        if not head_file.exists():
            self.mirror_path.parent.mkdir(parents=True, exist_ok=True)
            if self.mirror_path.exists() and any(self.mirror_path.iterdir()):
                raise ValueError(f"mirror path exists and is not empty: {self.mirror_path}")
            self._run(["git", "clone", "--mirror", self.remote_url, str(self.mirror_path)])
        else:
            self._run(
                [
                    "git",
                    f"--git-dir={self.mirror_path}",
                    "remote",
                    "set-url",
                    "origin",
                    self.remote_url,
                ]
            )

    def fetch_origin(self) -> None:
        self._run(["git", f"--git-dir={self.mirror_path}", "fetch", "--prune", "origin"])

    def get_branch_commit(self, branch: str) -> str:
        refs_to_try = [
            f"refs/heads/{branch}",
            f"refs/remotes/origin/{branch}",
        ]
        last_error: GitCommandError | None = None
        for ref in refs_to_try:
            try:
                return self._run(
                    ["git", f"--git-dir={self.mirror_path}", "rev-parse", "--verify", ref]
                ).strip()
            except GitCommandError as exc:
                last_error = exc
        if last_error is None:
            raise RuntimeError("unexpected branch lookup failure without error")
        raise last_error

    def get_workspace_head(self, workspace_path: Path) -> str | None:
        if not (workspace_path / ".git").exists():
            return None
        try:
            return self._run(["git", "-C", str(workspace_path), "rev-parse", "HEAD"]).strip()
        except GitCommandError:
            return None

    def sync_workspace(self, workspace_path: Path, branch: str, commit_hash: str) -> SyncResult:
        previous = self.get_workspace_head(workspace_path)
        self._ensure_workspace_repo(workspace_path)

        self._run(["git", "-C", str(workspace_path), "fetch", "--prune", "origin"])
        local_branch = self._local_branch_name(branch)
        self._run(
            [
                "git",
                "-C",
                str(workspace_path),
                "checkout",
                "-B",
                local_branch,
                commit_hash,
            ]
        )
        self._run(["git", "-C", str(workspace_path), "reset", "--hard", commit_hash])
        self._run(["git", "-C", str(workspace_path), "clean", "-fd"])

        current = self.get_workspace_head(workspace_path)
        if not current:
            raise RuntimeError(f"failed to read workspace HEAD after sync: {workspace_path}")

        return SyncResult(previous_commit=previous, commit_hash=current, changed=(previous != current))

    def _ensure_workspace_repo(self, workspace_path: Path) -> None:
        if not (workspace_path / ".git").exists():
            workspace_path.parent.mkdir(parents=True, exist_ok=True)
            if workspace_path.exists() and any(workspace_path.iterdir()):
                raise ValueError(f"workspace exists and is not a git repo: {workspace_path}")
            self._run(["git", "clone", str(self.mirror_path), str(workspace_path)])

        self._run(
            [
                "git",
                "-C",
                str(workspace_path),
                "remote",
                "set-url",
                "origin",
                str(self.mirror_path),
            ]
        )

    def _local_branch_name(self, branch: str) -> str:
        cleaned = re.sub(r"[^A-Za-z0-9_.-]+", "-", branch).strip("-")
        return f"gateway-{cleaned or 'default'}"

    def _run(self, args: list[str]) -> str:
        proc = subprocess.run(args, check=False, capture_output=True, text=True)
        if proc.returncode != 0:
            raise GitCommandError(args=args, returncode=proc.returncode, stdout=proc.stdout, stderr=proc.stderr)
        return proc.stdout

    def _allow_local_remote_if_needed(self) -> None:
        candidate: str | None = None
        if self.remote_url.startswith("/"):
            candidate = self.remote_url
        elif self.remote_url.startswith("file://"):
            parsed = urlparse(self.remote_url)
            candidate = parsed.path
        if not candidate:
            return
        if not Path(candidate).exists():
            return
        # Avoid git safety checks blocking local bind-mounted repositories.
        self._run(["git", "config", "--global", "--add", "safe.directory", candidate])