package useCases

import (
	"RenewCMS/internal/domain/contenttype"
	"RenewCMS/internal/domain/entry"
	"RenewCMS/internal/domain/image"
	"cmp"
	"errors"
	"maps"
	"slices"
)

type EntryMedia struct {
	ID           uint32
	Missing      bool
	Filename     string
	Width        *int
	Height       *int
	Size         int64
	ThumbnailURL string
}

type mediaResolver struct {
	images image.Repository
	cache  map[uint32]EntryMedia
}

func newMediaResolver(images image.Repository) *mediaResolver {
	return &mediaResolver{images: images, cache: map[uint32]EntryMedia{}}
}

func (r *mediaResolver) resolve(owner contenttype.ContentType, record entry.Entry) (map[string]EntryMedia, error) {
	resolved := map[string]EntryMedia{}
	for _, ref := range contenttype.MediaRefs(owner.Fields, record.Data) {
		media, err := r.lookup(ref.ID)
		if err != nil {
			return nil, err
		}
		resolved[ref.Field.Key] = media
	}
	return resolved, nil
}

func (r *mediaResolver) lookup(id uint32) (EntryMedia, error) {
	if cached, found := r.cache[id]; found {
		return cached, nil
	}
	found, err := r.images.Get(id)
	if errors.Is(err, image.ErrImageNotFound) {
		r.cache[id] = EntryMedia{ID: id, Missing: true}
		return r.cache[id], nil
	}
	if err != nil {
		return EntryMedia{}, err
	}
	media := EntryMedia{ID: found.ID, Filename: found.Filename, Width: knownDimension(found.Width), Height: knownDimension(found.Height), Size: found.Size, ThumbnailURL: found.Path}
	r.cache[id] = media
	return media, nil
}

func knownDimension(value int) *int {
	if value <= 0 {
		return nil
	}
	return &value
}

type mediaEntry struct {
	owner  contenttype.ContentType
	record entry.Entry
}

func (m mediaEntry) keysPointingAt(ids map[uint32]bool) []string {
	keys := []string{}
	for _, ref := range contenttype.MediaRefs(m.owner.Fields, m.record.Data) {
		if ids[ref.ID] {
			keys = append(keys, ref.Field.Key)
		}
	}
	return keys
}

func compareMediaEntries(a, b mediaEntry) int {
	return cmp.Or(cmp.Compare(a.owner.Name, b.owner.Name), cmp.Compare(a.owner.ID, b.owner.ID), cmp.Compare(a.record.ID, b.record.ID))
}

type entryMediaIndex struct {
	byImage map[uint32][]mediaEntry
}

func newEntryMediaIndex(found []mediaEntry) *entryMediaIndex {
	index := &entryMediaIndex{byImage: map[uint32][]mediaEntry{}}
	for _, candidate := range found {
		distinct := map[uint32]bool{}
		for _, ref := range contenttype.MediaRefs(candidate.owner.Fields, candidate.record.Data) {
			distinct[ref.ID] = true
		}
		for id := range distinct {
			index.byImage[id] = append(index.byImage[id], candidate)
		}
	}
	return index
}

func (i *entryMediaIndex) usageCounts() map[uint32]int {
	counts := make(map[uint32]int, len(i.byImage))
	for id, found := range i.byImage {
		counts[id] = len(found)
	}
	return counts
}

func (i *entryMediaIndex) referencing(imageIDs []uint32) []mediaEntry {
	type entryKey struct{ typeID, entryID uint32 }
	seen := map[entryKey]bool{}
	var found []mediaEntry
	for _, id := range imageIDs {
		for _, candidate := range i.byImage[id] {
			key := entryKey{candidate.owner.ID, candidate.record.ID}
			if !seen[key] {
				seen[key] = true
				found = append(found, candidate)
			}
		}
	}
	slices.SortFunc(found, compareMediaEntries)
	return found
}

type entryMediaScanner struct {
	contentTypes contenttype.Repository
	entries      entry.Repository
}

func newEntryMediaScanner(contentTypes contenttype.Repository, entries entry.Repository) *entryMediaScanner {
	return &entryMediaScanner{contentTypes: contentTypes, entries: entries}
}

func (s *entryMediaScanner) index() (*entryMediaIndex, error) {
	types, err := s.contentTypes.List()
	if err != nil {
		return nil, err
	}
	var found []mediaEntry
	for _, owner := range types {
		if len(contenttype.MediaFields(owner.Fields)) == 0 {
			continue
		}
		page, err := s.entries.ListPage(entry.Filters{ContentTypeID: owner.ID, Unpaged: true, Sort: entry.DefaultSort()})
		if err != nil {
			return nil, err
		}
		for _, record := range page.Items {
			found = append(found, mediaEntry{owner: owner, record: record})
		}
	}
	return newEntryMediaIndex(found), nil
}

func (s *entryMediaScanner) usageCounts() (map[uint32]int, error) {
	index, err := s.index()
	if err != nil {
		return nil, err
	}
	return index.usageCounts(), nil
}

func (s *entryMediaScanner) referencing(imageID uint32) ([]mediaEntry, error) {
	index, err := s.index()
	if err != nil {
		return nil, err
	}
	return index.referencing([]uint32{imageID}), nil
}

func repointEntries(entries entry.Repository, candidates []mediaEntry, copyIDs []uint32, keptID uint32) (int, error) {
	copies := map[uint32]bool{}
	for _, id := range copyIDs {
		copies[id] = true
	}
	updated := 0
	for _, candidate := range candidates {
		current, err := entries.Get(candidate.owner.ID, candidate.record.ID)
		if errors.Is(err, entry.ErrEntryNotFound) {
			continue
		}
		if err != nil {
			return updated, err
		}
		keys := mediaEntry{owner: candidate.owner, record: current}.keysPointingAt(copies)
		if len(keys) == 0 {
			continue
		}
		current.Data = maps.Clone(current.Data)
		for _, key := range keys {
			current.Data[key] = float64(keptID)
		}
		if _, err := entries.Update(current); err != nil {
			return updated, err
		}
		updated++
	}
	return updated, nil
}