package useCases

import (
	"RenewCMS/internal/domain/image"
	"sort"
	"time"
)

type VariantCacheEntry struct {
	Name    string
	Enabled bool
	Files   int
	Bytes   int64
}

type VariantCacheImage struct {
	ID       uint32
	Filename string
	URL      string
	Files    int
	Bytes    int64
}

type VariantCacheStats struct {
	GeneratedFiles     int
	DiskUsed           int64
	VariantsDefined    int
	VariantsEnabled    int
	VariantsDisabled   int
	RejectedRequests   int
	RejectedWindowDays int
	Unused             image.VariantFileTotals
	UnusedDays         int
	ByVariant          []VariantCacheEntry
	TopImages          []VariantCacheImage
}

type GetVariantCacheStatsUseCase struct {
	variants image.VariantRepository
	files    image.VariantFileRepository
	cache    image.VariantCacheRepository
	images   image.Repository
	usage    image.VariantUsageRepository
	tracker  image.VariantUsageTracker
	now      func() time.Time
}

func NewGetVariantCacheStatsUseCase(variants image.VariantRepository, files image.VariantFileRepository, cache image.VariantCacheRepository, images image.Repository, usage image.VariantUsageRepository, tracker image.VariantUsageTracker, now func() time.Time) *GetVariantCacheStatsUseCase {
	return &GetVariantCacheStatsUseCase{variants, files, cache, images, usage, tracker, now}
}

func (u *GetVariantCacheStatsUseCase) Get() (VariantCacheStats, error) {
	_ = u.tracker.Flush()

	variants, err := u.variants.List()
	if err != nil {
		return VariantCacheStats{}, err
	}
	totals, err := u.files.Totals()
	if err != nil {
		return VariantCacheStats{}, err
	}
	now := u.now()
	unused, err := u.cache.UnusedTotals(image.UnusedFilter{VariantNames: enabledNames(variants), Cutoff: image.UnusedCutoff(now)})
	if err != nil {
		return VariantCacheStats{}, err
	}
	rejected, err := u.usage.RejectedSince(image.RejectionWindowStart(now))
	if err != nil {
		return VariantCacheStats{}, err
	}
	top, err := u.topImages()
	if err != nil {
		return VariantCacheStats{}, err
	}

	stats := VariantCacheStats{
		VariantsDefined:    len(variants),
		RejectedRequests:   rejected,
		RejectedWindowDays: image.RejectionWindowDays,
		Unused:             unused,
		UnusedDays:         image.UnusedVariantDays,
		ByVariant:          cacheEntries(variants, totals),
		TopImages:          top,
	}
	for _, entry := range stats.ByVariant {
		stats.GeneratedFiles += entry.Files
		stats.DiskUsed += entry.Bytes
		if entry.Enabled {
			stats.VariantsEnabled++
		}
	}
	stats.VariantsDisabled = stats.VariantsDefined - stats.VariantsEnabled
	return stats, nil
}

func enabledNames(variants []image.Variant) []string {
	names := []string{}
	for _, variant := range variants {
		if variant.Enabled {
			names = append(names, variant.Name)
		}
	}
	return names
}

func cacheEntries(variants []image.Variant, totals map[string]image.VariantFileTotals) []VariantCacheEntry {
	entries := make([]VariantCacheEntry, 0, len(variants))
	for _, variant := range variants {
		own := totals[variant.Name]
		entries = append(entries, VariantCacheEntry{Name: variant.Name, Enabled: variant.Enabled, Files: own.Files, Bytes: own.Bytes})
	}
	sort.Slice(entries, func(i, j int) bool {
		if entries[i].Bytes != entries[j].Bytes {
			return entries[i].Bytes > entries[j].Bytes
		}
		return entries[i].Name < entries[j].Name
	})
	return entries
}

func (u *GetVariantCacheStatsUseCase) topImages() ([]VariantCacheImage, error) {
	limit := image.TopImagesLimit + 1
	for {
		sources, err := u.cache.TopSources(limit)
		if err != nil {
			return nil, err
		}
		ranked, err := u.rank(sources)
		if err != nil {
			return nil, err
		}
		if len(sources) < limit || topIsSettled(ranked, sources) {
			return ranked[:min(len(ranked), image.TopImagesLimit)], nil
		}
		limit *= 2
	}
}

func topIsSettled(ranked []VariantCacheImage, sources []image.SourceTotals) bool {
	return len(ranked) >= image.TopImagesLimit && ranked[image.TopImagesLimit-1].Bytes > sources[len(sources)-1].Bytes
}

func (u *GetVariantCacheStatsUseCase) rank(sources []image.SourceTotals) ([]VariantCacheImage, error) {
	names := make([]string, 0, len(sources))
	for _, source := range sources {
		names = append(names, source.SourceName)
	}
	found, err := u.images.ListByStoredNames(names)
	if err != nil {
		return nil, err
	}
	byName := make(map[string]image.Image, len(found))
	for _, img := range found {
		byName[image.StoredName(img.Path)] = img
	}
	ranked := make([]VariantCacheImage, 0, len(sources))
	for _, source := range sources {
		if img, known := byName[source.SourceName]; known {
			ranked = append(ranked, VariantCacheImage{ID: img.ID, Filename: img.Filename, URL: image.PublicPath(source.SourceName), Files: source.Files, Bytes: source.Bytes})
		}
	}
	sort.SliceStable(ranked, func(i, j int) bool {
		if ranked[i].Bytes != ranked[j].Bytes {
			return ranked[i].Bytes > ranked[j].Bytes
		}
		return ranked[i].ID < ranked[j].ID
	})
	return ranked, nil
}