#!/usr/bin/env python3
"""
Generate mutation testing trend report from mutation_history.json
"""
import json
import sys
from datetime import datetime
from pathlib import Path


def load_history(history_file: Path) -> list:
    """Load mutation testing history from JSON file."""
    if not history_file.exists():
        print(f"❌ History file not found: {history_file}")
        sys.exit(1)

    with open(history_file) as f:
        return json.load(f)


def format_timestamp(ts: str) -> str:
    """Format ISO timestamp to readable date."""
    dt = datetime.fromisoformat(ts.replace('Z', '+00:00'))
    return dt.strftime('%Y-%m-%d %H:%M')


def print_summary(history: list) -> None:
    """Print summary statistics."""
    if not history:
        print("No mutation testing history found.")
        return

    latest = history[-1]
    stats = latest['stats']

    print("\n" + "=" * 70)
    print("                    MUTATION TESTING SUMMARY")
    print("=" * 70)
    print(f"\nLatest Run: {format_timestamp(latest['timestamp'])}")
    print(f"Git Branch: {latest['git_branch']}")
    print(f"Git Commit: {latest['git_commit'][:8]}")
    print(f"\nCurrent Score: {stats['score']}%")
    print(f"  Total Mutants: {stats['total_mutants']}")
    print(f"  Viable:        {stats['viable']}")
    print(f"  Caught:        {stats['caught']}")
    print(f"  Missed:        {stats['missed']}")
    print(f"  Timeout:       {stats['timeout']}")
    print(f"  Unviable:      {stats['unviable']}")


def print_trend(history: list, limit: int = 10) -> None:
    """Print mutation score trend."""
    if len(history) < 2:
        print("\n📊 Not enough history for trend analysis (need at least 2 runs)")
        return

    print(f"\n📈 TREND (last {min(limit, len(history))} runs):")
    print("-" * 70)
    print(f"{'Date':<17} {'Branch':<15} {'Score':<8} {'Caught/Viable':<15} {'Change'}")
    print("-" * 70)

    recent = history[-limit:] if len(history) > limit else history
    prev_score = None

    for entry in recent:
        stats = entry['stats']
        score = stats['score']
        date = format_timestamp(entry['timestamp'])
        branch = entry['git_branch'][:14]
        caught_viable = f"{stats['caught']}/{stats['viable']}"

        # Calculate change
        if prev_score is not None:
            change = score - prev_score
            if change > 0:
                change_str = f"+{change:.1f}% ⬆"
            elif change < 0:
                change_str = f"{change:.1f}% ⬇"
            else:
                change_str = "0.0% ➡"
        else:
            change_str = "-"

        print(f"{date:<17} {branch:<15} {score:>6.1f}% {caught_viable:<15} {change_str}")
        prev_score = score


def print_statistics(history: list) -> None:
    """Print overall statistics."""
    if not history:
        return

    scores = [entry['stats']['score'] for entry in history]
    avg_score = sum(scores) / len(scores)
    min_score = min(scores)
    max_score = max(scores)

    print("\n📊 STATISTICS:")
    print("-" * 70)
    print(f"Total Runs:     {len(history)}")
    print(f"Average Score:  {avg_score:.2f}%")
    print(f"Min Score:      {min_score:.2f}%")
    print(f"Max Score:      {max_score:.2f}%")
    print(f"Score Range:    {max_score - min_score:.2f}%")


def main():
    """Main entry point."""
    history_file = Path("mutation_history.json")

    if len(sys.argv) > 1:
        history_file = Path(sys.argv[1])

    history = load_history(history_file)

    print_summary(history)
    print_trend(history, limit=10)
    print_statistics(history)

    print("\n" + "=" * 70 + "\n")


if __name__ == "__main__":
    main()