"""Abstract base class for Git hosting provider backends."""

import hashlib
from abc import ABC, abstractmethod

import httpx


class GitProviderBackend(ABC):
    """Abstract base for Git hosting provider API backends."""

    @staticmethod
    def _blob_sha(content_bytes: bytes) -> str:
        """Compute the git blob SHA for content_bytes (sha1("blob {len}\\0" + data))."""
        return hashlib.sha1(f"blob {len(content_bytes)}\0".encode() + content_bytes, usedforsecurity=False).hexdigest()

    @staticmethod
    def _truncated_response_text(response: httpx.Response, max_length: int = 200) -> str:
        """Return a bounded response body for errors surfaced to logs/UI."""
        text = response.text
        if len(text) <= max_length:
            return text
        return f"{text[: max_length - 3]}..."

    @staticmethod
    def _read_sha(response: httpx.Response, *path: str) -> tuple[str | None, str | None]:
        """Walk a JSON path to a string SHA value.

        Returns ``(sha, None)`` on success, ``(None, reason)`` if the body is
        not JSON, the path is missing, or the leaf is not a string. Callers
        use the reason to build a clear failure message instead of letting
        ``KeyError``/``JSONDecodeError`` bubble to the outer catch-all (which
        surfaces cryptic one-word strings like ``"'object'"`` to operators).
        """
        try:
            data = response.json()
        except ValueError:
            return None, "non-JSON response body"
        for key in path:
            if not isinstance(data, dict):
                return None, f"unexpected shape at key {key!r}"
            if key not in data:
                return None, f"missing key {key!r}"
            data = data[key]
        if not isinstance(data, str):
            return None, f"value at {'.'.join(path)} is not a string"
        return data, None

    def get_headers(self, token: str) -> dict:
        """Return HTTP headers for authenticated API requests."""
        return {
            "Authorization": f"token {token}",
            "Accept": "application/vnd.github.v3+json",
            "User-Agent": "Bambuddy-Backup",
        }

    @abstractmethod
    def parse_repo_url(self, url: str) -> tuple[str, str]:
        """Return (owner, repo) extracted from the repository URL."""

    @abstractmethod
    def get_api_base(self, repo_url: str) -> str:
        """Return the API base URL for this provider instance."""

    @abstractmethod
    async def test_connection(self, repo_url: str, token: str, client: httpx.AsyncClient) -> dict:
        """Test API connectivity and push permissions. Returns success/message/repo_name/permissions."""

    @abstractmethod
    async def push_files(
        self,
        repo_url: str,
        token: str,
        branch: str,
        files: dict,
        client: httpx.AsyncClient,
    ) -> dict:
        """Push files to the repository. Returns status/message/commit_sha/files_changed."""