from collections import defaultdict
from dataclasses import dataclass
from typing import Dict, Optional

from src.analyzers.git_repository import GitRepository
from src.models.data_structures import CodeChurnAnalysis


@dataclass
class CodeChurnAnalyzer:
    """Analyzes code churn."""

    repo: GitRepository
    days: int

    def analyze(self) -> Optional[CodeChurnAnalysis]:
        """Analyze code churn."""
        commits = self.repo.get_commits()

        if not commits:
            return None

        total_lines_added = sum(c.lines_added for c in commits)
        total_lines_deleted = sum(c.lines_deleted for c in commits)
        net_change = total_lines_added - total_lines_deleted

        churn_by_file: Dict[str, Dict[str, int]] = defaultdict(lambda: {"added": 0, "deleted": 0})
        churn_by_author: Dict[str, Dict[str, int]] = defaultdict(lambda: {"added": 0, "deleted": 0})

        high_churn_commits = []
        churn_threshold = 500

        for commit in commits:
            for filepath in commit.files_changed:
                churn_by_file[filepath]["added"] += commit.lines_added
                churn_by_file[filepath]["deleted"] += commit.lines_deleted

            churn_by_author[commit.author]["added"] += commit.lines_added
            churn_by_author[commit.author]["deleted"] += commit.lines_deleted

            if commit.lines_added + commit.lines_deleted > churn_threshold:
                high_churn_commits.append(commit)

        high_churn_commits.sort(key=lambda c: c.lines_added + c.lines_deleted, reverse=True)

        total_changes = sum(c.lines_added + c.lines_deleted for c in commits)
        avg_churn_per_commit = total_changes / max(1, len(commits))

        return CodeChurnAnalysis(
            total_lines_added=total_lines_added,
            total_lines_deleted=total_lines_deleted,
            net_change=net_change,
            churn_by_file=dict(churn_by_file),
            churn_by_author=dict(churn_by_author),
            high_churn_commits=high_churn_commits[:50],
            average_churn_per_commit=avg_churn_per_commit,
        )