package main

import (
	"context"
	"database/sql"
	"encoding/json"
	"fmt"
	"os"
	"path/filepath"
	"strings"
	"time"
)

// LeaderboardIndex represents the leaderboard.json structure
type LeaderboardIndex struct {
	UpdatedAt string            `json:"updated_at"`
	Entries   []LeaderboardEntry `json:"entries"`
}

// LeaderboardEntry represents a single bot on the leaderboard
type LeaderboardEntry struct {
	Rank           int     `json:"rank"`
	BotID          string  `json:"bot_id"`
	Name           string  `json:"name"`
	OwnerID        string  `json:"owner_id"`
	Rating         int     `json:"rating"`
	RatingDeviation float64 `json:"rating_deviation"`
	MatchesPlayed  int     `json:"matches_played"`
	MatchesWon     int     `json:"matches_won"`
	WinRate        float64 `json:"win_rate"`
	HealthStatus   string  `json:"health_status"`
}

// BotDirectory represents bots/index.json
type BotDirectory struct {
	UpdatedAt string              `json:"updated_at"`
	Bots      []BotDirectoryEntry `json:"bots"`
}

// BotDirectoryEntry represents a bot in the directory
type BotDirectoryEntry struct {
	ID            string  `json:"id"`
	Name          string  `json:"name"`
	Rating        int     `json:"rating"`
	MatchesPlayed int     `json:"matches_played"`
	WinRate       float64 `json:"win_rate"`
}

// BotProfile represents data/bots/{bot_id}.json
type BotProfile struct {
	ID               string                 `json:"id"`
	Name             string                 `json:"name"`
	OwnerID          string                 `json:"owner_id"`
	Description      string                 `json:"description,omitempty"`
	Rating           int                    `json:"rating"`
	RatingDeviation  float64                `json:"rating_deviation"`
	RatingVolatility float64                `json:"rating_volatility"`
	MatchesPlayed    int                    `json:"matches_played"`
	MatchesWon       int                    `json:"matches_won"`
	WinRate          float64                `json:"win_rate"`
	HealthStatus     string                 `json:"health_status"`
	Evolved          bool                   `json:"evolved"`
	Island           string                 `json:"island,omitempty"`
	Generation       int                    `json:"generation,omitempty"`
	CreatedAt        string                 `json:"created_at"`
	RatingHistory    []RatingHistoryEntry   `json:"rating_history"`
	RecentMatches    []MatchSummary         `json:"recent_matches"`
}

// MatchSummary represents a match in listings
type MatchSummary struct {
	ID           string               `json:"id"`
	CompletedAt  string               `json:"completed_at"`
	Participants []MatchParticipantSummary `json:"participants"`
	WinnerID     string               `json:"winner_id,omitempty"`
	Turns        int                  `json:"turns"`
	EndReason    string               `json:"end_reason"`
}

// MatchParticipantSummary represents a bot in a match summary
type MatchParticipantSummary struct {
	BotID string `json:"bot_id"`
	Name  string `json:"name"`
	Score int    `json:"score"`
	Won   bool   `json:"won"`
}

// MatchIndex represents matches/index.json
type MatchIndex struct {
	UpdatedAt string         `json:"updated_at"`
	Matches   []MatchSummary `json:"matches"`
}

// generateAllIndexes creates all JSON index files
func generateAllIndexes(data *IndexData, outputDir string, db *sql.DB) error {
	botNameMap := make(map[string]string)
	for _, bot := range data.Bots {
		botNameMap[bot.ID] = bot.Name
	}

	// Generate leaderboard.json
	if err := generateLeaderboard(data, outputDir); err != nil {
		return fmt.Errorf("leaderboard: %w", err)
	}

	// Generate bots/index.json
	if err := generateBotDirectory(data, outputDir); err != nil {
		return fmt.Errorf("bot directory: %w", err)
	}

	// Generate individual bot profiles
	if err := generateBotProfiles(data, outputDir); err != nil {
		return fmt.Errorf("bot profiles: %w", err)
	}

	// Generate matches/index.json
	if err := generateMatchIndex(data, outputDir, botNameMap); err != nil {
		return fmt.Errorf("match index: %w", err)
	}

	// Generate series/index.json
	if err := generateSeriesIndex(data, outputDir); err != nil {
		return fmt.Errorf("series index: %w", err)
	}

	// Generate seasons/index.json
	if err := generateSeasonsIndex(data, outputDir); err != nil {
		return fmt.Errorf("seasons index: %w", err)
	}

	// Generate predictions/leaderboard.json
	if err := generatePredictionsIndex(data, outputDir); err != nil {
		return fmt.Errorf("predictions index: %w", err)
	}

	// Generate playlists
	if err := generatePlaylists(data, outputDir, botNameMap); err != nil {
		return fmt.Errorf("playlists: %w", err)
	}

	// Persist playlists to DB for incremental queries and R2 pruning exemptions
	if db != nil {
		if err := persistGeneratedPlaylists(context.Background(), db, outputDir); err != nil {
			// Non-fatal: playlists are still written as JSON files
			fmt.Fprintf(os.Stderr, "persist playlists to DB: %v\n", err)
		}
	}

	return nil
}

func generateLeaderboard(data *IndexData, outputDir string) error {
	entries := make([]LeaderboardEntry, 0, len(data.Bots))
	for i, bot := range data.Bots {
		if bot.MatchesPlayed == 0 {
			continue
		}
		winRate := 0.0
		if bot.MatchesPlayed > 0 {
			winRate = float64(bot.MatchesWon) / float64(bot.MatchesPlayed) * 100
		}
		entries = append(entries, LeaderboardEntry{
			Rank:            i + 1,
			BotID:           bot.ID,
			Name:            bot.Name,
			OwnerID:         bot.OwnerID,
			Rating:          int(bot.Rating),
			RatingDeviation: bot.RatingDeviation,
			MatchesPlayed:   bot.MatchesPlayed,
			MatchesWon:      bot.MatchesWon,
			WinRate:         round1(winRate),
			HealthStatus:    bot.HealthStatus,
		})
	}

	leaderboard := LeaderboardIndex{
		UpdatedAt: data.GeneratedAt.Format(time.RFC3339),
		Entries:   entries,
	}

	return writeJSON(filepath.Join(outputDir, "data", "leaderboard.json"), leaderboard)
}

func generateBotDirectory(data *IndexData, outputDir string) error {
	entries := make([]BotDirectoryEntry, 0, len(data.Bots))
	for _, bot := range data.Bots {
		winRate := 0.0
		if bot.MatchesPlayed > 0 {
			winRate = float64(bot.MatchesWon) / float64(bot.MatchesPlayed) * 100
		}
		entries = append(entries, BotDirectoryEntry{
			ID:            bot.ID,
			Name:          bot.Name,
			Rating:        int(bot.Rating),
			MatchesPlayed: bot.MatchesPlayed,
			WinRate:       round1(winRate),
		})
	}

	dir := BotDirectory{
		UpdatedAt: data.GeneratedAt.Format(time.RFC3339),
		Bots:      entries,
	}

	return writeJSON(filepath.Join(outputDir, "data", "bots", "index.json"), dir)
}

func generateBotProfiles(data *IndexData, outputDir string) error {
	botsDir := filepath.Join(outputDir, "data", "bots")

	for _, bot := range data.Bots {
		winRate := 0.0
		if bot.MatchesPlayed > 0 {
			winRate = float64(bot.MatchesWon) / float64(bot.MatchesPlayed) * 100
		}

		// Get rating history for this bot
		history := make([]RatingHistoryEntry, 0)
		for _, h := range data.RatingHistory {
			if h.BotID == bot.ID {
				history = append(history, h)
			}
		}

		// Get recent matches for this bot (last 20)
		recentMatches := make([]MatchSummary, 0)
		for _, m := range data.Matches {
			participated := false
			for _, p := range m.Participants {
				if p.BotID == bot.ID {
					participated = true
					break
				}
			}
			if participated {
				summary := matchToSummary(m, data)
				recentMatches = append(recentMatches, summary)
				if len(recentMatches) >= 20 {
					break
				}
			}
		}

		profile := BotProfile{
			ID:               bot.ID,
			Name:             bot.Name,
			OwnerID:          bot.OwnerID,
			Description:      bot.Description,
			Rating:           int(bot.Rating),
			RatingDeviation:  bot.RatingDeviation,
			RatingVolatility: bot.RatingVolatility,
			MatchesPlayed:    bot.MatchesPlayed,
			MatchesWon:       bot.MatchesWon,
			WinRate:          round1(winRate),
			HealthStatus:     bot.HealthStatus,
			Evolved:          bot.Evolved,
			Island:           bot.Island,
			Generation:       bot.Generation,
			CreatedAt:        bot.CreatedAt.Format(time.RFC3339),
			RatingHistory:    history,
			RecentMatches:    recentMatches,
		}

		if err := writeJSON(filepath.Join(botsDir, bot.ID+".json"), profile); err != nil {
			return err
		}
	}

	return nil
}

func generateMatchIndex(data *IndexData, outputDir string, botNameMap map[string]string) error {
	summaries := make([]MatchSummary, 0, len(data.Matches))
	for _, m := range data.Matches {
		summaries = append(summaries, matchToSummary(m, data))
	}

	index := MatchIndex{
		UpdatedAt: data.GeneratedAt.Format(time.RFC3339),
		Matches:   summaries,
	}

	return writeJSON(filepath.Join(outputDir, "data", "matches", "index.json"), index)
}

func matchToSummary(m MatchData, data *IndexData) MatchSummary {
	participants := make([]MatchParticipantSummary, 0, len(m.Participants))
	for _, p := range m.Participants {
		name := "Unknown"
		for _, bot := range data.Bots {
			if bot.ID == p.BotID {
				name = bot.Name
				break
			}
		}
		participants = append(participants, MatchParticipantSummary{
			BotID: p.BotID,
			Name:  name,
			Score: p.Score,
			Won:   p.BotID == m.WinnerID,
		})
	}

	return MatchSummary{
		ID:           m.ID,
		CompletedAt:  m.CompletedAt.Format(time.RFC3339),
		Participants: participants,
		WinnerID:     m.WinnerID,
		Turns:        m.TurnCount,
		EndReason:    m.EndCondition,
	}
}

func generateSeriesIndex(data *IndexData, outputDir string) error {
	seriesDir := filepath.Join(outputDir, "data", "series")

	for _, s := range data.Series {
		if err := writeJSON(filepath.Join(seriesDir, fmt.Sprintf("%d.json", s.ID)), s); err != nil {
			return err
		}
	}

	type SeriesIndex struct {
		UpdatedAt string       `json:"updated_at"`
		Series    []SeriesData `json:"series"`
	}

	index := SeriesIndex{
		UpdatedAt: data.GeneratedAt.Format(time.RFC3339),
		Series:    data.Series,
	}

	return writeJSON(filepath.Join(seriesDir, "index.json"), index)
}

func generateSeasonsIndex(data *IndexData, outputDir string) error {
	seasonsDir := filepath.Join(outputDir, "data", "seasons")

	for _, s := range data.Seasons {
		if err := writeJSON(filepath.Join(seasonsDir, fmt.Sprintf("%d.json", s.ID)), s); err != nil {
			return err
		}
	}

	var activeSeason *SeasonData
	for i := range data.Seasons {
		if data.Seasons[i].Status == "active" {
			activeSeason = &data.Seasons[i]
			break
		}
	}

	type SeasonsIndex struct {
		UpdatedAt    string       `json:"updated_at"`
		ActiveSeason *SeasonData  `json:"active_season"`
		Seasons      []SeasonData `json:"seasons"`
	}

	index := SeasonsIndex{
		UpdatedAt:    data.GeneratedAt.Format(time.RFC3339),
		ActiveSeason: activeSeason,
		Seasons:      data.Seasons,
	}

	return writeJSON(filepath.Join(seasonsDir, "index.json"), index)
}

func generatePredictionsIndex(data *IndexData, outputDir string) error {
	type PredictionsLeaderboard struct {
		UpdatedAt string           `json:"updated_at"`
		Entries   []PredictorStats `json:"entries"`
	}

	index := PredictionsLeaderboard{
		UpdatedAt: data.GeneratedAt.Format(time.RFC3339),
		Entries:   data.TopPredictors,
	}

	return writeJSON(filepath.Join(outputDir, "data", "predictions", "leaderboard.json"), index)
}

func generatePlaylists(data *IndexData, outputDir string, botNameMap map[string]string) error {
	playlistsDir := filepath.Join(outputDir, "data", "playlists")

	// Pre-build lookup maps for O(1) playlist curation instead of O(n^2) per match.
	firstMatchPerBot := buildFirstMatchPerBot(data.Matches)
	pairFrequency := buildPairFrequency(data.Matches)

	type playlistDef struct {
		slug        string
		title       string
		description string
		category    string
		filter      func(MatchData) bool
		sort        func([]MatchData)
	}

	defs := []playlistDef{
		{
			slug:        "closest-finishes",
			title:       "Closest Finishes",
			description: "Matches decided by the thinnest margins — nail-biters to the very end",
			category:    "close_games",
			filter: func(m MatchData) bool {
				if len(m.Participants) < 2 || m.WinnerID == "" {
					return false
				}
				return minScoreDiff(m) <= 2
			},
			sort: func(matches []MatchData) {
				sortByScoreDiff(matches)
			},
		},
		{
			slug:        "biggest-upsets",
			title:       "Biggest Upsets",
			description: "Lower-rated bots triumph against higher-rated opponents",
			category:    "upsets",
			filter: func(m MatchData) bool {
				if m.WinnerID == "" || len(m.Participants) < 2 {
					return false
				}
				return ratingUpsetMagnitude(m) >= 100
			},
			sort: func(matches []MatchData) {
				sortByUpsetMagnitude(matches)
			},
		},
		{
			slug:        "best-comebacks",
			title:       "Best Comebacks",
			description: "Bots that were down but never out — dramatic turnarounds and improbable victories",
			category:    "comebacks",
			filter: func(m MatchData) bool {
				return isComeback(m)
			},
			sort: func(matches []MatchData) {
				sortSlice(matches, func(i, j int) bool {
					return turnaroundMagnitude(matches[i]) > turnaroundMagnitude(matches[j])
				})
			},
		},
		{
			slug:        "marathon-matches",
			title:       "Marathon Matches",
			description: "The longest, most grueling matches — endurance-tested battles",
			category:    "long_games",
			filter: func(m MatchData) bool {
				return m.TurnCount >= 300
			},
			sort: func(matches []MatchData) {
				sortByTurnCount(matches)
			},
		},
		{
			slug:        "highest-rated",
			title:       "Clash of Titans",
			description: "Matches between the highest-rated opponents on the ladder",
			category:    "featured",
			filter: func(m MatchData) bool {
				if len(m.Participants) < 2 {
					return false
				}
				return combinedRating(m) >= 3200
			},
			sort: func(matches []MatchData) {
				sortByCombinedRating(matches)
			},
		},
		{
			slug:        "evolution-breakthroughs",
			title:       "Evolution Breakthroughs",
			description: "Evolved bots defeating top-rated opponents — AI strategy milestones",
			category:    "featured",
			filter: func(m MatchData) bool {
				return isEvolutionBreakthrough(m, data)
			},
			sort: func(matches []MatchData) {
				sortByUpsetMagnitude(matches)
			},
		},
		{
			slug:        "rivalry-classics",
			title:       "Rivalry Classics",
			description: "The most closely contested matchups between frequent opponents",
			category:    "rivalry",
			filter: func(m MatchData) bool {
				return isRivalryMatchFast(m, pairFrequency)
			},
			sort: func(matches []MatchData) {
				sortSlice(matches, func(i, j int) bool {
					return minScoreDiff(matches[i]) < minScoreDiff(matches[j])
				})
			},
		},
		{
			slug:        "domination",
			title:       "Total Domination",
			description: "One-sided victories where the winner crushed all opposition",
			category:    "domination",
			filter: func(m MatchData) bool {
				if m.WinnerID == "" || len(m.Participants) < 2 {
					return false
				}
				return maxScoreDiff(m) >= 5
			},
			sort: func(matches []MatchData) {
				sortSlice(matches, func(i, j int) bool {
					return maxScoreDiff(matches[i]) > maxScoreDiff(matches[j])
				})
			},
		},
		{
			slug:        "new-bot-debuts",
			title:       "New Bot Debuts",
			description: "First matches of newly registered bots — watch their opening games",
			category:    "tutorial",
			filter: func(m MatchData) bool {
				return isNewBotDebutFast(m, firstMatchPerBot)
			},
			sort: func(matches []MatchData) {
				// Newest debuts first
				sortSlice(matches, func(i, j int) bool {
					return matches[i].CompletedAt.After(matches[j].CompletedAt)
				})
			},
		},
		{
			slug:        "season-highlights",
			title:       "Season Highlights",
			description: "Top matches from the current season ranked by excitement",
			category:    "season",
			filter: func(m MatchData) bool {
				return isCurrentSeasonMatch(m, data)
			},
			sort: func(matches []MatchData) {
				sortByInterestScore(matches)
			},
		},
		{
			slug:        "featured",
			title:       "Featured Matches",
			description: "Recent highlights from the ladder",
			category:    "featured",
			filter: func(m MatchData) bool {
				return m.WinnerID != ""
			},
			sort: func(matches []MatchData) {
				// Most recent first (already sorted by completed_at DESC from DB)
			},
		},
		{
			slug:        "best-of-week",
			title:       "Best of the Week",
			description: "This week's top matches ranked by excitement: close finishes, upsets, marathon battles, and elite clashes",
			category:    "weekly",
			filter: func(m MatchData) bool {
				weekAgo := data.GeneratedAt.AddDate(0, 0, -7)
				return m.CompletedAt.After(weekAgo) && m.WinnerID != ""
			},
			sort: func(matches []MatchData) {
				sortByInterestScore(matches)
			},
		},
	}

	var summaries []PlaylistSummary

	for _, def := range defs {
		// Special handling for best-of-week: use curated selection with tags
		if def.slug == "best-of-week" {
			weekAgo := data.GeneratedAt.AddDate(0, 0, -7)
			curated := curateWeeklyHighlights(data.Matches, weekAgo)
			curatedMatches := make([]MatchData, 0, len(curated))
			tags := make(map[string]string, len(curated))
			for _, c := range curated {
				curatedMatches = append(curatedMatches, c.Match)
				tags[c.Match.ID] = c.Tag
			}

			if err := writePlaylistWithTags(playlistsDir, def.slug+".json", def.title, def.description, def.category, curatedMatches, tags, data); err != nil {
				return err
			}

			var thumbMatchID string
			if len(curatedMatches) > 0 {
				thumbMatchID = curatedMatches[0].ID
			}
			summaries = append(summaries, PlaylistSummary{
				Slug:            def.slug,
				Title:           def.title,
				Description:     def.description,
				Category:        def.category,
				MatchCount:      len(curatedMatches),
				UpdatedAt:       data.GeneratedAt.Format(time.RFC3339),
				ThumbnailMatchID: thumbMatchID,
			})
			continue
		}

		filtered := filterMatches(data.Matches, def.filter)
		if def.sort != nil {
			def.sort(filtered)
		}
		filtered = filtered[:min(20, len(filtered))]

		if err := writePlaylist(playlistsDir, def.slug+".json", def.title, def.description, def.category, filtered, data); err != nil {
			return err
		}

		var thumbMatchID string
		if len(filtered) > 0 {
			thumbMatchID = filtered[0].ID
		}
		summaries = append(summaries, PlaylistSummary{
			Slug:            def.slug,
			Title:           def.title,
			Description:     def.description,
			Category:        def.category,
			MatchCount:      len(filtered),
			UpdatedAt:       data.GeneratedAt.Format(time.RFC3339),
			ThumbnailMatchID: thumbMatchID,
		})
	}

	index := PlaylistIndex{
		UpdatedAt: data.GeneratedAt.Format(time.RFC3339),
		Playlists: summaries,
	}
	return writeJSON(filepath.Join(playlistsDir, "index.json"), index)
}

type PlaylistIndex struct {
	UpdatedAt string             `json:"updated_at"`
	Playlists []PlaylistSummary  `json:"playlists"`
}

type PlaylistSummary struct {
	Slug             string `json:"slug"`
	Title            string `json:"title"`
	Description      string `json:"description"`
	Category         string `json:"category"`
	MatchCount       int    `json:"match_count"`
	UpdatedAt        string `json:"updated_at"`
	ThumbnailMatchID string `json:"thumbnail_match_id,omitempty"`
}

type Playlist struct {
	Slug        string          `json:"slug"`
	Title       string          `json:"title"`
	Description string          `json:"description"`
	Category    string          `json:"category"`
	MatchCount  int             `json:"match_count"`
	CreatedAt   string          `json:"created_at"`
	UpdatedAt   string          `json:"updated_at"`
	Matches     []PlaylistMatch `json:"matches"`
}

type PlaylistMatch struct {
	MatchID      string                    `json:"match_id"`
	Order        int                       `json:"order"`
	Title        string                    `json:"title,omitempty"`
	ThumbnailURL string                    `json:"thumbnail_url,omitempty"`
	CurationTag  string                    `json:"curation_tag,omitempty"`
	Participants []MatchParticipantSummary `json:"participants,omitempty"`
	Score        string                    `json:"score,omitempty"`
	Turns        int                       `json:"turns,omitempty"`
	EndReason    string                    `json:"end_reason,omitempty"`
	CompletedAt  string                    `json:"completed_at,omitempty"`
}

// curatedWeeklyMatch is a match selected by the weekly curation algorithm
// with a tag explaining why it was selected.
type curatedWeeklyMatch struct {
	Match MatchData
	Tag   string
}

// curateWeeklyHighlights selects the best matches from the past 7 days
// using explicit criteria: upsets, elite clashes, marathon battles, closest finishes.
// It processes specific criteria first so distinctive matches aren't consumed
// by generic tags. It returns deduplicated matches tagged with their selection reason.
func curateWeeklyHighlights(matches []MatchData, cutoff time.Time) []curatedWeeklyMatch {
	seen := make(map[string]string) // match_id -> tag (first selection reason)
	maxPerCriterion := 7

	recent := filterMatches(matches, func(m MatchData) bool {
		return m.CompletedAt.After(cutoff) && m.WinnerID != "" && len(m.Participants) >= 2
	})

	// 1. Biggest upsets first (most distinctive — underdog victories)
	upsetMatches := make([]MatchData, len(recent))
	copy(upsetMatches, recent)
	sortByUpsetMagnitude(upsetMatches)
	for i, m := range upsetMatches {
		if i >= maxPerCriterion {
			break
		}
		mag := ratingUpsetMagnitude(m)
		if mag < 50 {
			continue
		}
		if _, exists := seen[m.ID]; !exists {
			seen[m.ID] = fmt.Sprintf("Upset victory (underdog by %d rating)", mag)
		}
	}

	// 2. Highest-rated opponents (elite clashes)
	ratedMatches := make([]MatchData, len(recent))
	copy(ratedMatches, recent)
	sortByCombinedRating(ratedMatches)
	for i, m := range ratedMatches {
		if i >= maxPerCriterion {
			break
		}
		cr := int(combinedRating(m))
		if cr < 3000 {
			continue
		}
		if _, exists := seen[m.ID]; !exists {
			seen[m.ID] = fmt.Sprintf("Elite clash (combined rating: %d)", cr)
		}
	}

	// 3. Most turns (longest endurance battles)
	longMatches := make([]MatchData, len(recent))
	copy(longMatches, recent)
	sortByTurnCount(longMatches)
	for i, m := range longMatches {
		if i >= maxPerCriterion {
			break
		}
		if m.TurnCount < 300 {
			continue
		}
		if _, exists := seen[m.ID]; !exists {
			seen[m.ID] = fmt.Sprintf("Marathon battle (%d turns)", m.TurnCount)
		}
	}

	// 4. Closest results last (most generic — fills remaining slots)
	closeMatches := make([]MatchData, len(recent))
	copy(closeMatches, recent)
	sortByScoreDiff(closeMatches)
	for i, m := range closeMatches {
		if i >= maxPerCriterion {
			break
		}
		diff := minScoreDiff(m)
		if _, exists := seen[m.ID]; !exists {
			seen[m.ID] = fmt.Sprintf("Closest finish (score diff: %d)", diff)
		}
	}

	// Build result in criterion order: upsets, elite, marathon, closest
	var result []curatedWeeklyMatch
	for _, m := range recent {
		if tag, ok := seen[m.ID]; ok {
			result = append(result, curatedWeeklyMatch{Match: m, Tag: tag})
		}
	}

	if len(result) > 20 {
		result = result[:20]
	}

	return result
}

func writePlaylist(dir, filename, title, description, category string, matches []MatchData, data *IndexData) error {
	slug := filename[:len(filename)-5]
	pm := make([]PlaylistMatch, 0, len(matches))
	for i, m := range matches {
		pm = append(pm, buildPlaylistMatch(m, i, data, ""))
	}

	playlist := Playlist{
		Slug:        slug,
		Title:       title,
		Description: description,
		Category:    category,
		MatchCount:  len(pm),
		CreatedAt:   data.GeneratedAt.Format(time.RFC3339),
		UpdatedAt:   data.GeneratedAt.Format(time.RFC3339),
		Matches:     pm,
	}

	return writeJSON(filepath.Join(dir, filename), playlist)
}

func writePlaylistWithTags(dir, filename, title, description, category string, matches []MatchData, tags map[string]string, data *IndexData) error {
	slug := filename[:len(filename)-5]
	pm := make([]PlaylistMatch, 0, len(matches))
	for i, m := range matches {
		pm = append(pm, buildPlaylistMatch(m, i, data, tags[m.ID]))
	}

	playlist := Playlist{
		Slug:        slug,
		Title:       title,
		Description: description,
		Category:    category,
		MatchCount:  len(pm),
		CreatedAt:   data.GeneratedAt.Format(time.RFC3339),
		UpdatedAt:   data.GeneratedAt.Format(time.RFC3339),
		Matches:     pm,
	}

	return writeJSON(filepath.Join(dir, filename), playlist)
}

func formatMatchTitle(m MatchData, data *IndexData) string {
	names := make([]string, 0, len(m.Participants))
	scores := make([]int, 0, len(m.Participants))
	for _, p := range m.Participants {
		name := "Unknown"
		for _, bot := range data.Bots {
			if bot.ID == p.BotID {
				name = bot.Name
				break
			}
		}
		names = append(names, name)
		scores = append(scores, p.Score)
	}
	if len(names) == 2 {
		return fmt.Sprintf("%s %d – %d %s", names[0], scores[0], scores[1], names[1])
	}
	return fmt.Sprintf("%s (%d players)", m.ID[:min(8, len(m.ID))], len(names))
}

func buildPlaylistMatch(m MatchData, order int, data *IndexData, curationTag string) PlaylistMatch {
	participants := make([]MatchParticipantSummary, 0, len(m.Participants))
	scoreParts := make([]string, 0, len(m.Participants))
	for _, p := range m.Participants {
		name := "Unknown"
		for _, bot := range data.Bots {
			if bot.ID == p.BotID {
				name = bot.Name
				break
			}
		}
		participants = append(participants, MatchParticipantSummary{
			BotID: p.BotID,
			Name:  name,
			Score: p.Score,
			Won:   p.BotID == m.WinnerID,
		})
		scoreParts = append(scoreParts, fmt.Sprintf("%d", p.Score))
	}
	title := formatMatchTitle(m, data)
	completedAt := ""
	if !m.CompletedAt.IsZero() {
		completedAt = m.CompletedAt.Format(time.RFC3339)
	}
	return PlaylistMatch{
		MatchID:      m.ID,
		Order:        order,
		Title:        title,
		CurationTag:  curationTag,
		Participants: participants,
		Score:        strings.Join(scoreParts, "-"),
		Turns:        m.TurnCount,
		EndReason:    m.EndCondition,
		CompletedAt:  completedAt,
	}
}

func ratingUpsetMagnitude(m MatchData) int {
	if m.WinnerID == "" || len(m.Participants) < 2 {
		return 0
	}
	var winnerRating, bestLoserRating float64
	found := false
	for _, p := range m.Participants {
		if p.BotID == m.WinnerID {
			winnerRating = p.PreMatchRating
			found = true
		}
	}
	if !found || winnerRating == 0 {
		return 0
	}
	for _, p := range m.Participants {
		if p.BotID != m.WinnerID && p.PreMatchRating > bestLoserRating {
			bestLoserRating = p.PreMatchRating
		}
	}
	if bestLoserRating == 0 {
		return 0
	}
	return int(bestLoserRating - winnerRating)
}

func combinedRating(m MatchData) float64 {
	total := 0.0
	for _, p := range m.Participants {
		total += p.PreMatchRating
	}
	return total
}

func interestScore(m MatchData) float64 {
	score := 0.0
	// Close finishes are interesting
	if len(m.Participants) >= 2 {
		minDiff := 999
		for i, p1 := range m.Participants {
			for _, p2 := range m.Participants[i+1:] {
				diff := abs(p1.Score - p2.Score)
				if diff < minDiff {
					minDiff = diff
				}
			}
		}
		if minDiff <= 1 {
			score += 3.0
		} else if minDiff <= 2 {
			score += 2.0
		}
	}
	// Upsets are interesting
	upset := ratingUpsetMagnitude(m)
	if upset >= 200 {
		score += 4.0
	} else if upset >= 100 {
		score += 2.0
	}
	// Long matches are interesting
	if m.TurnCount >= 400 {
		score += 2.0
	} else if m.TurnCount >= 300 {
		score += 1.0
	}
	// High-rated opponents
	cr := combinedRating(m)
	if cr >= 3400 {
		score += 2.0
	} else if cr >= 3200 {
		score += 1.0
	}
	return score
}

func sortByScoreDiff(matches []MatchData) {
	sortSlice(matches, func(i, j int) bool {
		return minScoreDiff(matches[i]) < minScoreDiff(matches[j])
	})
}

func sortByUpsetMagnitude(matches []MatchData) {
	sortSlice(matches, func(i, j int) bool {
		return ratingUpsetMagnitude(matches[i]) > ratingUpsetMagnitude(matches[j])
	})
}

func sortByTurnCount(matches []MatchData) {
	sortSlice(matches, func(i, j int) bool {
		return matches[i].TurnCount > matches[j].TurnCount
	})
}

func sortByCombinedRating(matches []MatchData) {
	sortSlice(matches, func(i, j int) bool {
		return combinedRating(matches[i]) > combinedRating(matches[j])
	})
}

func sortByInterestScore(matches []MatchData) {
	sortSlice(matches, func(i, j int) bool {
		return interestScore(matches[i]) > interestScore(matches[j])
	})
}

func minScoreDiff(m MatchData) int {
	minDiff := 999
	for i, p1 := range m.Participants {
		for _, p2 := range m.Participants[i+1:] {
			diff := abs(p1.Score - p2.Score)
			if diff < minDiff {
				minDiff = diff
			}
		}
	}
	return minDiff
}

func sortSlice(s []MatchData, less func(i, j int) bool) {
	for i := 0; i < len(s)-1; i++ {
		for j := i + 1; j < len(s); j++ {
			if less(j, i) {
				s[i], s[j] = s[j], s[i]
			}
		}
	}
}

func filterMatches(matches []MatchData, pred func(MatchData) bool) []MatchData {
	result := make([]MatchData, 0)
	for _, m := range matches {
		if pred(m) {
			result = append(result, m)
		}
	}
	return result
}

// maxScoreDiff returns the maximum score difference between winner and any loser
func maxScoreDiff(m MatchData) int {
	if m.WinnerID == "" || len(m.Participants) < 2 {
		return 0
	}
	var winnerScore int
	for _, p := range m.Participants {
		if p.BotID == m.WinnerID {
			winnerScore = p.Score
			break
		}
	}
	maxDiff := 0
	for _, p := range m.Participants {
		if p.BotID != m.WinnerID {
			diff := winnerScore - p.Score
			if diff > maxDiff {
				maxDiff = diff
			}
		}
	}
	return maxDiff
}

// isNewBotDebut detects the first match of each bot by finding the earliest
// completed match for each bot.
func isNewBotDebut(m MatchData, data *IndexData) bool {
	if m.WinnerID == "" {
		return false
	}
	for _, p := range m.Participants {
		earliest := true
		for _, other := range data.Matches {
			if other.ID == m.ID || other.CompletedAt.IsZero() {
				continue
			}
			for _, op := range other.Participants {
				if op.BotID == p.BotID {
					if other.CompletedAt.Before(m.CompletedAt) {
						earliest = false
					}
				}
			}
		}
		if earliest {
			return true
		}
	}
	return false
}

// isCurrentSeasonMatch checks if a match belongs to the current active season.
func isCurrentSeasonMatch(m MatchData, data *IndexData) bool {
	for _, s := range data.Seasons {
		if s.Status != "active" {
			continue
		}
		// Check if match falls within season date range
		if m.CompletedAt.After(s.StartsAt) || m.CompletedAt.Equal(s.StartsAt) {
			if s.EndsAt.IsZero() || m.CompletedAt.Before(s.EndsAt) {
				return m.WinnerID != ""
			}
		}
	}
	return false
}

// isComeback detects matches where the winner was behind on score at some point
// but rallied to win. Uses a heuristic: winner scored more than loser despite
// having a lower pre-match rating (unlikely comeback) or the match had many turns
// (late-game rally) with a close final score.
func isComeback(m MatchData) bool {
	if m.WinnerID == "" || len(m.Participants) < 2 {
		return false
	}
	// An upset with a close score is a comeback
	upset := ratingUpsetMagnitude(m)
	scoreDiff := minScoreDiff(m)
	return upset >= 80 && scoreDiff <= 3
}

// turnaroundMagnitude measures how dramatic a comeback was.
// Higher = more surprising turnaround.
func turnaroundMagnitude(m MatchData) float64 {
	upset := float64(ratingUpsetMagnitude(m))
	closeFactor := 1.0 / float64(max(minScoreDiff(m), 1))
	turnFactor := float64(m.TurnCount) / 500.0
	return upset*closeFactor + turnFactor*50
}

// isEvolutionBreakthrough detects matches where an evolved bot beat a high-rated opponent.
func isEvolutionBreakthrough(m MatchData, data *IndexData) bool {
	if m.WinnerID == "" || len(m.Participants) < 2 {
		return false
	}
	winnerEvolved := false
	for _, bot := range data.Bots {
		if bot.ID == m.WinnerID && bot.Evolved {
			winnerEvolved = true
		}
	}
	if !winnerEvolved {
		return false
	}
	// Winner must have beaten someone rated >= 1600
	for _, p := range m.Participants {
		if p.BotID != m.WinnerID && p.PreMatchRating >= 1600 && !p.Won {
			return true
		}
	}
	return false
}

// buildFirstMatchPerBot returns a map from botID to the matchID of their earliest
// completed match. O(n*p) where n=matches, p=avg participants.
func buildFirstMatchPerBot(matches []MatchData) map[string]string {
	first := make(map[string]string)
	firstTime := make(map[string]time.Time)
	for _, m := range matches {
		if m.CompletedAt.IsZero() || m.WinnerID == "" {
			continue
		}
		for _, p := range m.Participants {
			if t, ok := firstTime[p.BotID]; !ok || m.CompletedAt.Before(t) {
				firstTime[p.BotID] = m.CompletedAt
				first[p.BotID] = m.ID
			}
		}
	}
	return first
}

// isNewBotDebutFast checks if any participant's earliest completed match is this one,
// using a pre-built lookup map.
func isNewBotDebutFast(m MatchData, firstMatchPerBot map[string]string) bool {
	if m.WinnerID == "" {
		return false
	}
	for _, p := range m.Participants {
		if firstMatchPerBot[p.BotID] == m.ID {
			return true
		}
	}
	return false
}

// buildPairFrequency returns a map from "botA:botB" (sorted) to the count of
// 2-player matches between them. O(n) where n=matches.
func buildPairFrequency(matches []MatchData) map[string]int {
	freq := make(map[string]int)
	for _, m := range matches {
		if len(m.Participants) != 2 {
			continue
		}
		a, b := m.Participants[0].BotID, m.Participants[1].BotID
		if a > b {
			a, b = b, a
		}
		freq[a+":"+b]++
	}
	return freq
}

// isRivalryMatchFast checks if a 2-player match is between frequent opponents,
// using a pre-built pair frequency map.
func isRivalryMatchFast(m MatchData, pairFrequency map[string]int) bool {
	if len(m.Participants) != 2 || m.WinnerID == "" {
		return false
	}
	a, b := m.Participants[0].BotID, m.Participants[1].BotID
	if a > b {
		a, b = b, a
	}
	return pairFrequency[a+":"+b] >= 3
}

// isRivalryMatch detects matches between bots that have played each other frequently.
// Builds a frequency map from all matches and checks if this pair qualifies.
func isRivalryMatch(m MatchData, data *IndexData) bool {
	if len(m.Participants) != 2 || m.WinnerID == "" {
		return false
	}
	a, b := m.Participants[0].BotID, m.Participants[1].BotID
	if a > b {
		a, b = b, a
	}
	pairKey := a + ":" + b

	// Count occurrences of this pair across all matches
	count := 0
	for _, other := range data.Matches {
		if len(other.Participants) != 2 {
			continue
		}
		oa, ob := other.Participants[0].BotID, other.Participants[1].BotID
		if oa > ob {
			oa, ob = ob, oa
		}
		if oa+":"+ob == pairKey {
			count++
		}
	}
	return count >= 3
}

func writeJSON(path string, data interface{}) error {
	f, err := os.Create(path)
	if err != nil {
		return err
	}
	defer f.Close()

	enc := json.NewEncoder(f)
	enc.SetEscapeHTML(false)
	enc.SetIndent("", "  ")
	return enc.Encode(data)
}

// persistGeneratedPlaylists reads the generated playlist JSON files from the output
// directory and writes them to the playlists and playlist_matches DB tables.
func persistGeneratedPlaylists(ctx context.Context, db *sql.DB, outputDir string) error {
	playlistsDir := filepath.Join(outputDir, "data", "playlists")

	indexContent, err := os.ReadFile(filepath.Join(playlistsDir, "index.json"))
	if err != nil {
		return fmt.Errorf("read playlist index: %w", err)
	}
	var index PlaylistIndex
	if err := json.Unmarshal(indexContent, &index); err != nil {
		return fmt.Errorf("parse playlist index: %w", err)
	}

	var persisted []persistedPlaylist
	for _, summary := range index.Playlists {
		plContent, err := os.ReadFile(filepath.Join(playlistsDir, summary.Slug+".json"))
		if err != nil {
			continue // skip playlists without files
		}
		var pl Playlist
		if err := json.Unmarshal(plContent, &pl); err != nil {
			continue
		}

		matches := make([]persistedPlaylistMatch, 0, len(pl.Matches))
		for _, m := range pl.Matches {
			matches = append(matches, persistedPlaylistMatch{
				MatchID:     m.MatchID,
				SortOrder:   m.Order,
				CurationTag: m.CurationTag,
			})
		}

		persisted = append(persisted, persistedPlaylist{
			Slug:        pl.Slug,
			Title:       pl.Title,
			Description: pl.Description,
			Category:    pl.Category,
			Matches:     matches,
		})
	}

	return persistPlaylists(ctx, db, persisted)
}

func round1(v float64) float64 {
	return float64(int(v*10+0.5)) / 10
}

func abs(x int) int {
	if x < 0 {
		return -x
	}
	return x
}

func min(a, b int) int {
	if a < b {
		return a
	}
	return b
}