package main

import (
	"fmt"
	"sort"
	"time"
)

// AnalyzePRs processes a list of PRs and generates metrics for each reviewer.
func (a *Analyzer) AnalyzePRs(prs []PRData) ([]ReviewerMetrics, error) {
	reviewerPRs := make(map[string][]PRMetrics)

	for _, pr := range prs {
		metrics, err := a.analyzePR(pr)
		if err != nil {
			return nil, fmt.Errorf("analyzing PR %d: %w", pr.Number, err)
		}

		for _, reviewer := range metrics.Reviewers {
			reviewerPRs[reviewer] = append(reviewerPRs[reviewer], metrics)
		}
	}

	var results []ReviewerMetrics
	for reviewer, prs := range reviewerPRs {
		metrics := a.calculateReviewerMetrics(reviewer, prs)
		results = append(results, metrics)
	}

	sort.Slice(results, func(i, j int) bool {
		return results[i].PRsReviewed > results[j].PRsReviewed
	})

	return results, nil
}

func (a *Analyzer) analyzePR(pr PRData) (PRMetrics, error) {
	metrics := PRMetrics{
		Number:          pr.Number,
		CreatedAt:       pr.CreatedAt,
		CommentsPerFile: make(map[string]int),
		Reviewers:       make([]string, 0),
	}

	sort.Slice(pr.Reviews, func(i, j int) bool {
		return pr.Reviews[i].SubmittedAt.Before(pr.Reviews[j].SubmittedAt)
	})

	for _, review := range pr.Reviews {
		metrics.Reviewers = append(metrics.Reviewers, review.Reviewer)

		pattern := ReviewPattern{
			FirstReviewState:  review.State,
			TimeToFirstReview: review.SubmittedAt.Sub(pr.CreatedAt),
		}

		for _, comment := range review.Comments {
			metrics.CommentsPerFile[comment.Path]++
		}

		metrics.ReviewPatterns = append(metrics.ReviewPatterns, pattern)
	}

	if len(pr.Reviews) > 0 {
		metrics.TimeToFirstReview = pr.Reviews[0].SubmittedAt.Sub(pr.CreatedAt)
	}

	if len(metrics.ReviewPatterns) > 0 {
		lastReview := pr.Reviews[len(pr.Reviews)-1]
		metrics.ReviewPatterns[len(metrics.ReviewPatterns)-1].FinalReviewState = lastReview.State
		metrics.ReviewPatterns[len(metrics.ReviewPatterns)-1].TimeToFinalReview = lastReview.SubmittedAt.Sub(
			pr.CreatedAt,
		)
	}

	return metrics, nil
}

func (a *Analyzer) calculateReviewerMetrics(reviewer string, prs []PRMetrics) ReviewerMetrics {
	metrics := ReviewerMetrics{
		Username:    reviewer,
		PRsReviewed: len(prs),
	}

	var totalReviewSpeed time.Duration
	var totalComments int
	var immediateApprovals int

	for _, pr := range prs {
		var pattern ReviewPattern
		for _, p := range pr.ReviewPatterns {
			if p.FirstReviewState != "" {
				pattern = p
				break
			}
		}

		if pattern.TimeToFirstReview > 0 {
			totalReviewSpeed += pattern.TimeToFirstReview
		}

		for _, count := range pr.CommentsPerFile {
			totalComments += count
		}

		if pattern.FirstReviewState == "APPROVED" {
			immediateApprovals++
		}
	}

	if metrics.PRsReviewed > 0 {
		metrics.AverageReviewSpeed = totalReviewSpeed.Hours() / float64(metrics.PRsReviewed)
		metrics.AverageComments = float64(totalComments) / float64(metrics.PRsReviewed)
		metrics.ImmediateApprovals = float64(
			immediateApprovals,
		) / float64(
			metrics.PRsReviewed,
		) * 100
	}

	return metrics
}