package useCases

import (
	"RenewCMS/internal/domain/article"
	"RenewCMS/internal/domain/audit"
	"RenewCMS/internal/domain/contenttype"
	"RenewCMS/internal/domain/entry"
	"RenewCMS/internal/domain/image"
	"RenewCMS/internal/domain/transaction"
	"context"
	"errors"
	"log"
	"slices"
)

type MergeMediaResult struct {
	ArticlesUpdated   int
	Merged            int
	SitesUpdated      int
	AuthorsUpdated    int
	EntriesUpdated    int
	UpdatedArticleIDs []uint32
}

type MergeMediaUseCase struct {
	imageRepository   image.Repository
	articleRepository article.Repository
	remover           mediaRemover
	recorder          audit.Recorder
	entries           *entryMediaScanner
	transactor        transaction.Transactor
	logger            *log.Logger
}

func NewMergeMediaUseCase(imageRepository image.Repository, articleRepository article.Repository, storage image.Storage, variantFiles image.VariantFileRepository, recorder audit.Recorder, contentTypes contenttype.Repository, entries entry.Repository, transactor transaction.Transactor, logger *log.Logger) *MergeMediaUseCase {
	return &MergeMediaUseCase{imageRepository: imageRepository, articleRepository: articleRepository, remover: newMediaRemover(imageRepository, storage, variantFiles), recorder: recorder, entries: newEntryMediaScanner(contentTypes, entries), transactor: transactor, logger: logger}
}

func copyIdsOf(copies []image.Image) []uint32 {
	copyIds := make([]uint32, 0, len(copies))
	for _, duplicate := range copies {
		copyIds = append(copyIds, duplicate.ID)
	}
	return copyIds
}

func (u *MergeMediaUseCase) Merge(ctx context.Context, keepId uint32, mergeIds []uint32) (MergeMediaResult, error) {
	result, err := u.merge(ctx, keepId, mergeIds, nil)
	event := audit.NewEvent(audit.ActionMediaMerge, audit.CategoryMedia)
	if kept, found := u.keptImage(keepId); found {
		event.Target = imageTarget(kept)
	}
	if err != nil {
		recordFailure(ctx, u.recorder, event, err)
		return MergeMediaResult{}, err
	}
	event.Params = map[string]any{audit.ParamMerged: result.Merged, audit.ParamArticlesUpdated: result.ArticlesUpdated}
	u.recorder.Record(ctx, event)
	return result, nil
}

func (u *MergeMediaUseCase) keptImage(keepId uint32) (image.Image, bool) {
	if keepId == 0 {
		return image.Image{}, false
	}
	kept, err := u.imageRepository.Get(keepId)
	return kept, err == nil
}

func (u *MergeMediaUseCase) merge(ctx context.Context, keepId uint32, mergeIds []uint32, index *entryMediaIndex) (MergeMediaResult, error) {
	if err := validateMergeRequest(keepId, mergeIds); err != nil {
		return MergeMediaResult{}, err
	}

	kept, err := u.imageRepository.Get(keepId)
	if err != nil {
		return MergeMediaResult{}, err
	}
	copies, err := u.loadCopies(kept, mergeIds)
	if err != nil {
		return MergeMediaResult{}, err
	}

	planned, err := u.planRewrites(copies)
	if err != nil {
		return MergeMediaResult{}, err
	}
	if index == nil {
		if index, err = u.entries.index(); err != nil {
			return MergeMediaResult{}, err
		}
	}

	result, err := u.applyMerge(ctx, kept, copies, planned, index.referencing(copyIdsOf(copies)))
	if err != nil {
		return MergeMediaResult{}, err
	}
	u.discardCopies(copies)
	return result, nil
}

func (u *MergeMediaUseCase) applyMerge(ctx context.Context, kept image.Image, copies []image.Image, planned []uint32, candidates []mediaEntry) (MergeMediaResult, error) {
	var result MergeMediaResult
	copyIds := copyIdsOf(copies)
	err := u.transactor.Run(ctx, func(tx transaction.Repositories) error {
		rewritten, err := rewriteBodies(tx.Articles, planned, copies, kept)
		if err != nil {
			return err
		}
		repointedArticles, err := tx.Articles.RepointImage(copyIds, kept.ID)
		if err != nil {
			return err
		}
		if result.SitesUpdated, err = tx.Sites.RepointImage(copyIds, kept.ID); err != nil {
			return err
		}
		if result.AuthorsUpdated, err = tx.Authors.RepointAvatar(copyIds, kept.ID); err != nil {
			return err
		}
		if result.EntriesUpdated, err = repointEntries(tx.Entries, candidates, copyIds, kept.ID); err != nil {
			return err
		}
		for _, duplicate := range copies {
			if err := tx.Images.Delete(duplicate.ID); err != nil {
				return err
			}
		}
		result.UpdatedArticleIDs = updatedArticleIds(rewritten, repointedArticles)
		result.ArticlesUpdated = len(result.UpdatedArticleIDs)
		result.Merged = len(copies)
		return nil
	})
	return result, err
}

func (u *MergeMediaUseCase) discardCopies(copies []image.Image) {
	for _, duplicate := range copies {
		if err := u.remover.discardFiles(duplicate); err != nil {
			u.logger.Printf("media merge: could not remove the files of %s: %v", image.StoredName(duplicate.Path), err)
		}
	}
}

func rewriteBodies(articles article.Repository, planned []uint32, copies []image.Image, kept image.Image) ([]uint32, error) {
	keptName := image.StoredName(kept.Path)
	var rewritten []uint32
	for _, id := range planned {
		current, err := articles.Get(id)
		if errors.Is(err, article.ErrArticleNotFound) {
			continue
		}
		if err != nil {
			return nil, err
		}
		body := current.Body
		for _, duplicate := range copies {
			body = image.ReplaceStoredName(body, image.StoredName(duplicate.Path), keptName)
		}
		if body == current.Body {
			continue
		}
		if _, err := articles.UpdateBody(id, body); err != nil {
			return nil, err
		}
		rewritten = append(rewritten, id)
	}
	return rewritten, nil
}

func updatedArticleIds(rewritten []uint32, repointed []uint32) []uint32 {
	ids := append(slices.Clone(repointed), rewritten...)
	slices.Sort(ids)
	return slices.Compact(ids)
}

func validateMergeRequest(keepId uint32, mergeIds []uint32) error {
	if keepId == 0 || len(mergeIds) == 0 {
		return image.ErrInvalidMergeRequest
	}
	seen := map[uint32]bool{keepId: true}
	for _, id := range mergeIds {
		if id == 0 || seen[id] {
			return image.ErrInvalidMergeRequest
		}
		seen[id] = true
	}
	return nil
}

func (u *MergeMediaUseCase) loadCopies(kept image.Image, mergeIds []uint32) ([]image.Image, error) {
	copies := make([]image.Image, 0, len(mergeIds))
	for _, id := range mergeIds {
		duplicate, err := u.imageRepository.Get(id)
		if errors.Is(err, image.ErrImageNotFound) {
			return nil, image.ErrMergeCopyMissing
		}
		if err != nil {
			return nil, err
		}
		if duplicate.SHA256 == "" || duplicate.SHA256 != kept.SHA256 {
			return nil, image.ErrMergeHashMismatch
		}
		copies = append(copies, duplicate)
	}
	return copies, nil
}

func (u *MergeMediaUseCase) planRewrites(copies []image.Image) ([]uint32, error) {
	seen := map[uint32]bool{}
	for _, duplicate := range copies {
		copyName := image.StoredName(duplicate.Path)
		articles, err := u.articleRepository.FindByBodyContaining(copyName)
		if err != nil {
			return nil, err
		}
		for _, a := range articles {
			if image.ContainsStoredName(a.Body, copyName) {
				seen[a.ID] = true
			}
		}
	}
	planned := make([]uint32, 0, len(seen))
	for id := range seen {
		planned = append(planned, id)
	}
	slices.Sort(planned)
	return planned, nil
}