"""
Backtesting Module.

This module provides functions to run backtesting on historical match data,
comparing predictions with actual results to calculate accuracy metrics.
"""

import json
import csv
from datetime import datetime
from typing import Dict, List, Any, Optional
from io import StringIO

from app.ml.prediction_calculator import calculate_prediction


# Validation thresholds
ACCURACY_VALIDATED_THRESHOLD = 60.0  # >= 60%: System validated
ACCURACY_ALERT_THRESHOLD = 55.0      # < 55%: Revision required


def validate_accuracy(accuracy: float) -> str:
    """
    Validate the accuracy of the prediction system.

    Args:
        accuracy: Accuracy percentage (0.0 - 100.0)

    Returns:
        'VALIDATED' if accuracy >= 60%,
        'REVISION_REQUIRED' if accuracy < 55%,
        'BELOW_TARGET' if 55% <= accuracy < 60%

    Examples:
        >>> validate_accuracy(70.0)
        'VALIDATED'
        >>> validate_accuracy(50.0)
        'REVISION_REQUIRED'
        >>> validate_accuracy(58.0)
        'BELOW_TARGET'
    """
    if accuracy >= ACCURACY_VALIDATED_THRESHOLD:
        return 'VALIDATED'
    elif accuracy < ACCURACY_ALERT_THRESHOLD:
        return 'REVISION_REQUIRED'
    else:
        return 'BELOW_TARGET'


def compare_prediction(predicted_winner: str, actual_winner: str) -> bool:
    """
    Compare predicted winner with actual match result.

    Args:
        predicted_winner: 'home', 'away', or 'draw'
        actual_winner: 'home', 'away', or 'draw'

    Returns:
        True if prediction was correct, False otherwise

    Examples:
        >>> compare_prediction('home', 'home')
        True
        >>> compare_prediction('home', 'away')
        False
    """
    return predicted_winner.lower() == actual_winner.lower()


def run_backtesting_single_match(
    match_id: int,
    home_team: str,
    away_team: str,
    home_energy: float,
    away_energy: float,
    actual_winner: str
) -> Dict[str, Any]:
    """
    Run backtesting for a single historical match.

    Calculates prediction and compares it with the actual result.

    Args:
        match_id: Unique match identifier
        home_team: Name of the home team
        away_team: Name of the away team
        home_energy: Energy score of the home team
        away_energy: Energy score of the away team
        actual_winner: Actual result ('home', 'away', or 'draw')

    Returns:
        Dictionary containing match details, prediction, and comparison result

    Examples:
        >>> result = run_backtesting_single_match(1, 'PSG', 'OM', 65.0, 45.0, 'home')
        >>> result['correct']
        True
    """
    # Calculate prediction
    prediction = calculate_prediction(home_energy, away_energy)

    # Compare with actual result
    is_correct = compare_prediction(prediction['predicted_winner'], actual_winner)

    return {
        'match_id': match_id,
        'home_team': home_team,
        'away_team': away_team,
        'home_energy': home_energy,
        'away_energy': away_energy,
        'prediction': prediction,
        'actual_winner': actual_winner,
        'correct': is_correct
    }


def run_backtesting_batch(matches: List[Dict[str, Any]]) -> Dict[str, Any]:
    """
    Run backtesting on a batch of historical matches.

    Processes multiple matches, calculates predictions, compares with actual
    results, and generates accuracy metrics and detailed report.

    Args:
        matches: List of match dictionaries with keys:
            - match_id (int)
            - home_team (str)
            - away_team (str)
            - home_energy (float)
            - away_energy (float)
            - actual_winner (str)
            - league (str, optional)
            - date (datetime, optional)

    Returns:
        Dictionary containing:
        - total_matches: Number of matches processed
        - correct_predictions: Number of correct predictions
        - incorrect_predictions: Number of incorrect predictions
        - accuracy: Accuracy percentage
        - status: Validation status (VALIDATED, REVISION_REQUIRED, BELOW_TARGET)
        - results: List of individual match results
        - metrics_by_league: Accuracy breakdown by league
        - timestamp: When the backtesting was run

    Examples:
        >>> matches = [
        ...     {'match_id': 1, 'home_team': 'PSG', 'away_team': 'OM',
        ...      'home_energy': 65.0, 'away_energy': 45.0, 'actual_winner': 'home'},
        ... ]
        >>> result = run_backtesting_batch(matches)
        >>> result['accuracy']
        100.0
    """
    results = []
    correct_predictions = 0
    incorrect_predictions = 0

    # Track metrics by league
    league_metrics: Dict[str, Dict[str, Any]] = {}

    for match in matches:
        # Validate required fields
        required_fields = ['match_id', 'home_team', 'away_team',
                          'home_energy', 'away_energy', 'actual_winner']
        if not all(field in match for field in required_fields):
            raise ValueError(f"Match missing required fields: {match}")

        # Extract league and date if available
        league = match.get('league', 'unknown')
        match_date = match.get('date')

        # Run backtesting for this match
        result = run_backtesting_single_match(
            match_id=match['match_id'],
            home_team=match['home_team'],
            away_team=match['away_team'],
            home_energy=match['home_energy'],
            away_energy=match['away_energy'],
            actual_winner=match['actual_winner']
        )

        # Add league and date to result
        result['league'] = league
        result['date'] = match_date.isoformat() if match_date else None

        # Track correctness
        if result['correct']:
            correct_predictions += 1
        else:
            incorrect_predictions += 1

        # Update league metrics
        if league not in league_metrics:
            league_metrics[league] = {
                'total': 0,
                'correct': 0,
                'accuracy': 0.0
            }
        league_metrics[league]['total'] += 1
        if result['correct']:
            league_metrics[league]['correct'] += 1

        results.append(result)

    # Calculate overall accuracy
    total_matches = len(matches)
    accuracy = (correct_predictions / total_matches * 100.0) if total_matches > 0 else 0.0

    # Calculate accuracy per league
    for league, metrics in league_metrics.items():
        if metrics['total'] > 0:
            metrics['accuracy'] = (metrics['correct'] / metrics['total'] * 100.0)

    # Get validation status
    status = validate_accuracy(accuracy)

    return {
        'total_matches': total_matches,
        'correct_predictions': correct_predictions,
        'incorrect_predictions': incorrect_predictions,
        'accuracy': round(accuracy, 2),
        'status': status,
        'results': results,
        'metrics_by_league': league_metrics,
        'timestamp': datetime.utcnow().isoformat(),
        'validation_thresholds': {
            'validated': ACCURACY_VALIDATED_THRESHOLD,
            'alert': ACCURACY_ALERT_THRESHOLD
        }
    }


def export_to_json(backtesting_result: Dict[str, Any]) -> str:
    """
    Export backtesting results to JSON format.

    Args:
        backtesting_result: Result from run_backtesting_batch

    Returns:
        JSON formatted string

    Examples:
        >>> result = run_backtesting_batch(matches)
        >>> json_output = export_to_json(result)
        >>> isinstance(json_output, str)
        True
    """
    return json.dumps(backtesting_result, indent=2, default=str)


def export_to_csv(backtesting_result: Dict[str, Any]) -> str:
    """
    Export backtesting results to CSV format.

    Args:
        backtesting_result: Result from run_backtesting_batch

    Returns:
        CSV formatted string

    Examples:
        >>> result = run_backtesting_batch(matches)
        >>> csv_output = export_to_csv(result)
        >>> isinstance(csv_output, str)
        True
    """
    output = StringIO()
    fieldnames = [
        'match_id', 'league', 'date', 'home_team', 'away_team',
        'home_energy', 'away_energy', 'predicted_winner',
        'confidence', 'actual_winner', 'correct'
    ]

    writer = csv.DictWriter(output, fieldnames=fieldnames)
    writer.writeheader()

    for result in backtesting_result.get('results', []):
        row = {
            'match_id': result['match_id'],
            'league': result.get('league', ''),
            'date': result.get('date', ''),
            'home_team': result['home_team'],
            'away_team': result['away_team'],
            'home_energy': result['home_energy'],
            'away_energy': result['away_energy'],
            'predicted_winner': result['prediction']['predicted_winner'],
            'confidence': result['prediction']['confidence'],
            'actual_winner': result['actual_winner'],
            'correct': result['correct']
        }
        writer.writerow(row)

    return output.getvalue()


def export_to_html(backtesting_result: Dict[str, Any]) -> str:
    """
    Export backtesting results to HTML format for publication.

    Args:
        backtesting_result: Result from run_backtesting_batch

    Returns:
        HTML formatted string with styling and charts

    Examples:
        >>> result = run_backtesting_batch(matches)
        >>> html_output = export_to_html(result)
        >>> '<html>' in html_output
        True
    """
    status_colors = {
        'VALIDATED': '#10B981',  # Green
        'BELOW_TARGET': '#F59E0B',  # Orange
        'REVISION_REQUIRED': '#EF4444'  # Red
    }

    status = backtesting_result['status']
    accuracy = backtesting_result['accuracy']
    total_matches = backtesting_result['total_matches']
    correct_predictions = backtesting_result['correct_predictions']
    incorrect_predictions = backtesting_result['incorrect_predictions']

    # Build HTML
    html = f"""
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Backtesting Report - ChartBastan</title>
    <style>
        * {{ margin: 0; padding: 0; box-sizing: border-box; }}
        body {{
            font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
            background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
            padding: 20px;
            min-height: 100vh;
        }}
        .container {{
            max-width: 1200px;
            margin: 0 auto;
            background: white;
            border-radius: 20px;
            box-shadow: 0 20px 60px rgba(0,0,0,0.3);
            padding: 40px;
        }}
        .header {{
            text-align: center;
            margin-bottom: 40px;
        }}
        .header h1 {{
            font-size: 2.5em;
            color: #667eea;
            margin-bottom: 10px;
        }}
        .header p {{
            color: #666;
            font-size: 1.1em;
        }}
        .summary {{
            display: grid;
            grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
            gap: 20px;
            margin-bottom: 40px;
        }}
        .card {{
            background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
            color: white;
            padding: 25px;
            border-radius: 15px;
            text-align: center;
        }}
        .card h3 {{
            font-size: 0.9em;
            opacity: 0.9;
            margin-bottom: 10px;
            text-transform: uppercase;
            letter-spacing: 1px;
        }}
        .card .value {{
            font-size: 2.5em;
            font-weight: bold;
            margin-bottom: 5px;
        }}
        .card .sub {{
            font-size: 0.9em;
            opacity: 0.9;
        }}
        .status-badge {{
            display: inline-block;
            padding: 10px 25px;
            border-radius: 25px;
            color: white;
            font-weight: bold;
            font-size: 1.2em;
            margin: 20px 0;
        }}
        .section {{
            margin-bottom: 40px;
        }}
        .section h2 {{
            font-size: 1.8em;
            color: #333;
            margin-bottom: 20px;
            padding-bottom: 10px;
            border-bottom: 3px solid #667eea;
        }}
        table {{
            width: 100%;
            border-collapse: collapse;
            margin-top: 20px;
        }}
        th, td {{
            padding: 15px;
            text-align: left;
            border-bottom: 1px solid #ddd;
        }}
        th {{
            background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
            color: white;
            font-weight: 600;
            text-transform: uppercase;
            font-size: 0.85em;
            letter-spacing: 0.5px;
        }}
        tr:hover {{
            background: #f5f5f5;
        }}
        .correct {{
            color: #10B981;
            font-weight: bold;
        }}
        .incorrect {{
            color: #EF4444;
            font-weight: bold;
        }}
        .footer {{
            text-align: center;
            margin-top: 40px;
            padding-top: 20px;
            border-top: 2px solid #ddd;
            color: #666;
        }}
    </style>
</head>
<body>
    <div class="container">
        <div class="header">
            <h1>📊 Backtesting Report</h1>
            <p>ChartBastan Prediction System Performance Analysis</p>
            <p style="margin-top: 10px; font-size: 0.9em;">
                Generated: {backtesting_result.get('timestamp', 'N/A')}
            </p>
        </div>

        <div class="summary">
            <div class="card">
                <h3>Total Matches</h3>
                <div class="value">{total_matches}</div>
                <div class="sub">matches analyzed</div>
            </div>
            <div class="card">
                <h3>Accuracy</h3>
                <div class="value">{accuracy}%</div>
                <div class="sub">prediction accuracy</div>
            </div>
            <div class="card">
                <h3>Correct</h3>
                <div class="value">{correct_predictions}</div>
                <div class="sub">predictions</div>
            </div>
            <div class="card">
                <h3>Incorrect</h3>
                <div class="value">{incorrect_predictions}</div>
                <div class="sub">predictions</div>
            </div>
        </div>

        <div style="text-align: center;">
            <div class="status-badge" style="background-color: {status_colors.get(status, '#666')};">
                Status: {status}
            </div>
        </div>

        <div class="section">
            <h2>📈 Metrics by League</h2>
            <table>
                <thead>
                    <tr>
                        <th>League</th>
                        <th>Matches</th>
                        <th>Correct</th>
                        <th>Accuracy</th>
                    </tr>
                </thead>
                <tbody>
"""

    # Add league metrics
    for league, metrics in backtesting_result.get('metrics_by_league', {}).items():
        html += f"""
                    <tr>
                        <td>{league}</td>
                        <td>{metrics['total']}</td>
                        <td>{metrics['correct']}</td>
                        <td>{metrics['accuracy']:.2f}%</td>
                    </tr>
"""

    html += """
                </tbody>
            </table>
        </div>

        <div class="section">
            <h2>📋 Detailed Results</h2>
            <table>
                <thead>
                    <tr>
                        <th>Match ID</th>
                        <th>League</th>
                        <th>Home vs Away</th>
                        <th>Prediction</th>
                        <th>Confidence</th>
                        <th>Actual</th>
                        <th>Result</th>
                    </tr>
                </thead>
                <tbody>
"""

    # Add detailed results
    for result in backtesting_result.get('results', []):
        result_class = 'correct' if result['correct'] else 'incorrect'
        html += f"""
                    <tr>
                        <td>{result['match_id']}</td>
                        <td>{result.get('league', 'N/A')}</td>
                        <td>{result['home_team']} vs {result['away_team']}</td>
                        <td>{result['prediction']['predicted_winner']}</td>
                        <td>{result['prediction']['confidence']:.1f}%</td>
                        <td>{result['actual_winner']}</td>
                        <td class="{result_class}">{'✓ Correct' if result['correct'] else '✗ Incorrect'}</td>
                    </tr>
"""

    html += """
                </tbody>
            </table>
        </div>

        <div class="footer">
            <p>🎯 ChartBastan - Football Match Prediction System</p>
            <p>© 2026 All rights reserved</p>
        </div>
    </div>
</body>
</html>
"""

    return html


def filter_matches_by_league(matches: List[Dict[str, Any]], leagues: List[str]) -> List[Dict[str, Any]]:
    """
    Filter matches by league(s).

    Args:
        matches: List of match dictionaries
        leagues: List of league names to include

    Returns:
        Filtered list of matches

    Examples:
        >>> matches = [{'league': 'Ligue 1', 'home_team': 'PSG', ...}]
        >>> filtered = filter_matches_by_league(matches, ['Ligue 1'])
        >>> len(filtered)
        1
    """
    if not leagues:
        return matches

    return [m for m in matches if m.get('league') in leagues]


def filter_matches_by_period(
    matches: List[Dict[str, Any]],
    start_date: Optional[datetime] = None,
    end_date: Optional[datetime] = None
) -> List[Dict[str, Any]]:
    """
    Filter matches by date period.

    Args:
        matches: List of match dictionaries
        start_date: Start date (inclusive), or None for no lower bound
        end_date: End date (inclusive), or None for no upper bound

    Returns:
        Filtered list of matches

    Examples:
        >>> from datetime import datetime
        >>> matches = [{'date': datetime(2026, 1, 1), ...}]
        >>> filtered = filter_matches_by_period(matches, datetime(2025, 1, 1))
    """
    filtered = matches

    if start_date:
        filtered = [m for m in filtered if m.get('date') and m['date'] >= start_date]

    if end_date:
        filtered = [m for m in filtered if m.get('date') and m['date'] <= end_date]

    return filtered