/**
 * PriorityAnalyzer - Calculates task priorities based on multiple factors
 * Updated to use GitContextAnalyzer for accurate task aging (Zero-Dependency)
 */

const GitContextAnalyzer = require('./git-context-analyzer');

class PriorityAnalyzer {
    constructor(projectRoot = process.cwd()) {
        this.weights = {
            severity: 0.30,        // Bug severity / security risk
            impact: 0.25,          // Lines of code affected / number of files
            complexity: 0.20,      // Implementation difficulty
            dependencies: 0.15,    // Number of dependent tasks
            age: 0.10             // How long issue has existed
        };

        this.severityScores = {
            CRITICAL: 100,
            HIGH: 75,
            MEDIUM: 50,
            LOW: 25,
            MINIMAL: 10
        };

        // Initialize Git context analyzer
        this.gitContext = new GitContextAnalyzer(projectRoot);
    }

    /**
     * Analyze and prioritize tasks with Git context enrichment
     */
    analyze(tasks) {
        const prioritizedTasks = tasks.map(task => {
            // Enrich task with Git context (actual age, author, commit history)
            const enrichedTask = this.enrichTaskWithGitContext(task);

            const scores = {
                severity: this.calculateSeverityScore(enrichedTask),
                impact: this.calculateImpactScore(enrichedTask),
                complexity: this.calculateComplexityScore(enrichedTask),
                dependencies: this.calculateDependencyScore(enrichedTask),
                age: this.calculateAgeScore(enrichedTask)
            };

            const priority = this.calculatePriority(scores);

            return {
                ...enrichedTask,
                scores,
                priority,
                priorityLevel: this.getPriorityLevel(priority),
                recommendation: this.generateRecommendation(enrichedTask, scores, priority)
            };
        });

        return this.sortByPriority(prioritizedTasks);
    }

    /**
     * Enrich task with Git context (actual age from git blame)
     */
    enrichTaskWithGitContext(task) {
        // Skip if no file/line info or Git not available
        if (!task.filePath || !task.line) {
            return task;
        }

        try {
            const gitAge = this.gitContext.getAnnotationAge(task.filePath, task.line);
            
            if (gitAge) {
                return {
                    ...task,
                    actualAge: gitAge.days,
                    author: gitAge.author,
                    lastModified: gitAge.date,
                    gitContext: true
                };
            }
        } catch (error) {
            // Git not available or file not in Git - continue with estimated age
        }

        return task;
    }

    /**
     * Calculate severity score (0-100)
     */
    calculateSeverityScore(task) {
        // For security issues
        if (task.type === 'security') {
            return this.severityScores[task.severity] || 50;
        }

        // For bugs
        if (task.type === 'bug') {
            if (task.severity === 'CRITICAL' || task.critical) return 100;
            if (task.severity === 'HIGH') return 75;
            if (task.severity === 'MEDIUM') return 50;
            return 25;
        }

        // For code quality issues
        if (task.type === 'code-smell' || task.type === 'quality') {
            return this.severityScores[task.severity] || 30;
        }

        // For features/improvements
        if (task.type === 'feature' || task.type === 'todo') {
            return 40; // Medium priority by default
        }

        return 25;
    }

    /**
     * Calculate impact score (0-100)
     */
    calculateImpactScore(task) {
        let score = 0;

        // Files affected
        if (task.filesAffected) {
            score += Math.min(task.filesAffected * 5, 40);
        }

        // Lines of code affected
        if (task.linesAffected) {
            score += Math.min(task.linesAffected / 10, 30);
        }

        // User-facing impact
        if (task.userFacing) {
            score += 30;
        }

        // Breaking change
        if (task.breaking) {
            score += 40;
        }

        // Module criticality
        if (task.module) {
            if (/(?:auth|security|payment|database)/i.test(task.module)) {
                score += 20;
            }
        }

        return Math.min(score, 100);
    }

    /**
     * Calculate complexity score (0-100)
     * Lower complexity = higher priority (easier to fix)
     */
    calculateComplexityScore(task) {
        let score = 50; // Default medium

        // Estimated effort
        if (task.effort) {
            const effortMap = {
                'XS': 90,  // Very quick fix
                'S': 75,
                'M': 50,
                'L': 30,
                'XL': 10   // Very complex
            };
            score = effortMap[task.effort] || 50;
        }

        // Cyclomatic complexity
        if (task.complexity) {
            if (task.complexity > 20) score -= 30;
            else if (task.complexity > 10) score -= 15;
        }

        // Dependencies on other tasks
        if (task.blockedBy && task.blockedBy.length > 0) {
            score -= (task.blockedBy.length * 10);
        }

        // Technical debt
        if (task.type === 'tech-debt') {
            score += 20; // Easier to tackle sooner
        }

        return Math.max(0, Math.min(100, score));
    }

    /**
     * Calculate dependency score (0-100)
     * More dependents = higher priority
     */
    calculateDependencyScore(task) {
        let score = 0;

        // Tasks blocked by this one
        if (task.blocks && task.blocks.length > 0) {
            score += task.blocks.length * 20;
        }

        // Number of files importing this module
        if (task.dependents) {
            score += Math.min(task.dependents * 5, 50);
        }

        // Critical path
        if (task.criticalPath) {
            score += 50;
        }

        return Math.min(score, 100);
    }

    /**
     * Calculate age score (0-100)
     * Uses actual Git blame data when available, falls back to estimates
     * Older issues get higher priority
     */
    calculateAgeScore(task) {
        // Use actual Git age if available (from enrichTaskWithGitContext)
        if (task.actualAge !== undefined) {
            const daysOld = task.actualAge;
            
            if (daysOld > 180) return 100;      // 6+ months
            if (daysOld > 90) return 75;        // 3-6 months
            if (daysOld > 30) return 50;        // 1-3 months
            if (daysOld > 7) return 25;         // 1-4 weeks
            return 10;                          // < 1 week
        }

        // Fallback to estimated age
        if (!task.createdAt && !task.age) return 25;

        let daysOld = 0;
        
        if (task.age) {
            daysOld = task.age;
        } else if (task.createdAt) {
            const created = new Date(task.createdAt);
            const now = new Date();
            daysOld = Math.floor((now - created) / (1000 * 60 * 60 * 24));
        }

        // Score increases with age
        if (daysOld > 180) return 100;      // 6+ months
        if (daysOld > 90) return 75;        // 3-6 months
        if (daysOld > 30) return 50;        // 1-3 months
        if (daysOld > 7) return 25;         // 1-4 weeks
        return 10;                          // < 1 week
    }

    /**
     * Calculate weighted priority score
     */
    calculatePriority(scores) {
        let priority = 0;

        priority += scores.severity * this.weights.severity;
        priority += scores.impact * this.weights.impact;
        priority += scores.complexity * this.weights.complexity;
        priority += scores.dependencies * this.weights.dependencies;
        priority += scores.age * this.weights.age;

        return Math.round(priority);
    }

    /**
     * Get priority level
     */
    getPriorityLevel(priority) {
        if (priority >= 80) return 'CRITICAL';
        if (priority >= 60) return 'HIGH';
        if (priority >= 40) return 'MEDIUM';
        if (priority >= 20) return 'LOW';
        return 'MINIMAL';
    }

    /**
     * Generate recommendation
     */
    generateRecommendation(task, scores, priority) {
        const recommendations = [];

        // Critical priority
        if (priority >= 80) {
            recommendations.push('Address immediately');
            
            if (scores.severity > 75) {
                recommendations.push('High severity - production risk');
            }
            if (scores.impact > 75) {
                recommendations.push('Wide impact - affects many users/files');
            }
            if (scores.dependencies > 75) {
                recommendations.push('Blocking other tasks');
            }
        }

        // High priority
        else if (priority >= 60) {
            recommendations.push('Schedule for current sprint');
            
            if (scores.complexity > 60) {
                recommendations.push('Relatively easy fix - quick win');
            }
            if (scores.age > 60) {
                recommendations.push('Long-standing issue - address soon');
            }
        }

        // Medium priority
        else if (priority >= 40) {
            recommendations.push('Plan for next sprint');
            
            if (scores.complexity < 40) {
                recommendations.push('Complex - may need team discussion');
            }
        }

        // Low priority
        else {
            recommendations.push('Backlog - address when capacity allows');
            
            if (task.type === 'tech-debt') {
                recommendations.push('Technical debt - consider during refactoring');
            }
        }

        // Effort estimation
        if (scores.complexity > 70) {
            recommendations.push('Estimated effort: Small (1-2 hours)');
        } else if (scores.complexity > 40) {
            recommendations.push('Estimated effort: Medium (3-8 hours)');
        } else {
            recommendations.push('Estimated effort: Large (1-3 days)');
        }

        return recommendations;
    }

    /**
     * Sort tasks by priority
     */
    sortByPriority(tasks) {
        return tasks.sort((a, b) => {
            // First by priority score
            if (b.priority !== a.priority) {
                return b.priority - a.priority;
            }

            // Then by severity
            const severityOrder = { CRITICAL: 5, HIGH: 4, MEDIUM: 3, LOW: 2, MINIMAL: 1 };
            return (severityOrder[b.priorityLevel] || 0) - (severityOrder[a.priorityLevel] || 0);
        });
    }

    /**
     * Generate priority report
     */
    generateReport(prioritizedTasks) {
        const summary = {
            totalTasks: prioritizedTasks.length,
            priorityDistribution: {
                CRITICAL: 0,
                HIGH: 0,
                MEDIUM: 0,
                LOW: 0,
                MINIMAL: 0
            },
            typeDistribution: {},
            topPriorities: [],
            quickWins: [],
            blockers: [],
            averageAge: 0
        };

        let totalAge = 0;

        prioritizedTasks.forEach(task => {
            // Count by priority
            summary.priorityDistribution[task.priorityLevel]++;

            // Count by type
            summary.typeDistribution[task.type] = (summary.typeDistribution[task.type] || 0) + 1;

            // Calculate average age
            if (task.scores.age) {
                totalAge += task.scores.age;
            }
        });

        summary.averageAge = prioritizedTasks.length > 0
            ? Math.round(totalAge / prioritizedTasks.length)
            : 0;

        // Top 10 priorities
        summary.topPriorities = prioritizedTasks
            .slice(0, 10)
            .map(t => ({
                title: t.title || t.message,
                priority: t.priority,
                priorityLevel: t.priorityLevel,
                type: t.type
            }));

        // Quick wins (high priority, low complexity)
        summary.quickWins = prioritizedTasks
            .filter(t => t.priority >= 60 && t.scores.complexity >= 70)
            .slice(0, 5)
            .map(t => ({
                title: t.title || t.message,
                priority: t.priority,
                effort: 'Small'
            }));

        // Blockers (high priority, blocking others)
        summary.blockers = prioritizedTasks
            .filter(t => t.scores.dependencies >= 50)
            .slice(0, 5)
            .map(t => ({
                title: t.title || t.message,
                priority: t.priority,
                blocks: t.blocks ? t.blocks.length : 0
            }));

        return summary;
    }
}

module.exports = PriorityAnalyzer;