"""
Sync Service.

Handles Git operations for repository mirroring including:
- Cloning repositories with SSH authentication
- Fetching updates from mirrored repositories
- Counting commits in repositories
- Retrieving commit history
"""
import subprocess
import tempfile
import os
from pathlib import Path
from typing import List, Dict, Optional
from sqlalchemy.orm import Session
import time

from app.models.repo import Repo


class SyncService:
    """
    Service for managing Git repository synchronization.

    Handles clone and fetch operations with SSH key authentication.
    """

    def __init__(self, db: Session):
        """
        Initialize the service with a database session.

        Args:
            db: SQLAlchemy database session
        """
        self.db = db

    def sync_repo(self, repo: Repo, ssh_key_content: str) -> None:
        """
        Synchronize a repository by cloning or fetching.

        If the repository doesn't exist locally, clone it.
        If it exists, fetch all updates.

        Args:
            repo: Repo model instance
            ssh_key_content: SSH private key content for authentication

        Raises:
            Exception: If clone or fetch operation fails
        """
        local_path = Path(repo.local_path)

        # Update repo status to syncing
        repo.status = "syncing"
        repo.last_sync_at = int(time.time())
        self.db.commit()

        if local_path.exists():
            # Repository exists, fetch updates
            self._fetch_repo(str(local_path), ssh_key_content)
        else:
            # Repository doesn't exist, clone it
            self._clone_repo(repo.clone_url, str(local_path), ssh_key_content)

    def _clone_repo(self, clone_url: str, local_path: str, ssh_key: str) -> None:
        """
        Clone a repository using git clone --mirror.

        Creates a bare mirror clone of the repository.

        Args:
            clone_url: Git clone URL (SSH format)
            local_path: Local path where repo should be cloned
            ssh_key: SSH private key content for authentication

        Raises:
            subprocess.CalledProcessError: If git clone fails
            IOError: If unable to create temporary SSH key file
        """
        # Create a temporary file for SSH key
        with tempfile.NamedTemporaryFile(mode='w', delete=False, suffix='.key') as key_file:
            key_file.write(ssh_key)
            key_file_path = key_file.name

        try:
            # Set appropriate permissions for SSH key
            os.chmod(key_file_path, 0o600)

            # Create SSH command wrapper that uses our key
            ssh_cmd = f'ssh -i {key_file_path} -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null'

            # Git clone command with mirror option
            git_cmd = [
                'git',
                'clone',
                '--mirror',
                clone_url,
                local_path
            ]

            # Run git clone with SSH authentication
            env = os.environ.copy()
            env['GIT_SSH_COMMAND'] = ssh_cmd

            result = subprocess.run(
                git_cmd,
                env=env,
                capture_output=True,
                text=True,
                check=True
            )

            return result

        finally:
            # Clean up temporary SSH key file
            try:
                os.unlink(key_file_path)
            except OSError:
                pass

    def _fetch_repo(self, local_path: str, ssh_key: str) -> None:
        """
        Fetch all updates for an existing repository.

        Args:
            local_path: Local path to the repository
            ssh_key: SSH private key content for authentication

        Raises:
            subprocess.CalledProcessError: If git fetch fails
            IOError: If unable to create temporary SSH key file
        """
        # Create a temporary file for SSH key
        with tempfile.NamedTemporaryFile(mode='w', delete=False, suffix='.key') as key_file:
            key_file.write(ssh_key)
            key_file_path = key_file.name

        try:
            # Set appropriate permissions for SSH key
            os.chmod(key_file_path, 0o600)

            # Create SSH command wrapper that uses our key
            ssh_cmd = f'ssh -i {key_file_path} -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null'

            # Git fetch command to get all updates
            git_cmd = [
                'git',
                '--git-dir',
                local_path,
                'fetch',
                '--all'
            ]

            # Run git fetch with SSH authentication
            env = os.environ.copy()
            env['GIT_SSH_COMMAND'] = ssh_cmd

            result = subprocess.run(
                git_cmd,
                env=env,
                capture_output=True,
                text=True,
                check=True
            )

            return result

        finally:
            # Clean up temporary SSH key file
            try:
                os.unlink(key_file_path)
            except OSError:
                pass

    def _count_commits(self, repo_path: str) -> int:
        """
        Count the number of commits in a repository.

        Args:
            repo_path: Path to the repository

        Returns:
            Number of commits, or 0 if counting fails
        """
        try:
            git_cmd = [
                'git',
                '--git-dir',
                repo_path,
                'rev-list',
                '--all',
                '--count'
            ]

            result = subprocess.run(
                git_cmd,
                capture_output=True,
                text=True,
                check=True
            )

            return int(result.stdout.strip())

        except (subprocess.CalledProcessError, ValueError):
            return 0

    def get_repo_commits(self, repo: Repo, limit: int = 100) -> List[Dict[str, str]]:
        """
        Get commit history for a repository.

        Args:
            repo: Repo model instance
            limit: Maximum number of commits to return

        Returns:
            List of commit dictionaries containing:
            - hash: Commit SHA
            - message: Commit message
            - author: Author name
            - email: Author email
            - date: Commit timestamp (Unix timestamp)
        """
        repo_path = Path(repo.local_path)

        if not repo_path.exists():
            return []

        try:
            git_cmd = [
                'git',
                '--git-dir',
                str(repo_path),
                'log',
                '--all',
                f'--max-count={limit}',
                '--format=%H|%s|%an|%ae|%ct'
            ]

            result = subprocess.run(
                git_cmd,
                capture_output=True,
                text=True,
                check=True
            )

            commits = []
            for line in result.stdout.strip().split('\n'):
                if line:
                    parts = line.split('|')
                    if len(parts) == 5:
                        commits.append({
                            'hash': parts[0],
                            'message': parts[1],
                            'author': parts[2],
                            'email': parts[3],
                            'date': int(parts[4])
                        })

            return commits

        except subprocess.CalledProcessError:
            return []