package useCases

import (
	"RenewCMS/internal/domain/article"
	"RenewCMS/internal/domain/audit"
	"RenewCMS/internal/domain/builtintype"
	"RenewCMS/internal/domain/localization"
	"RenewCMS/internal/domain/role"
	"RenewCMS/internal/domain/site"
	"RenewCMS/internal/domain/transaction"
	"context"
	"errors"
	"slices"
)

const maxSiteLockRounds = 5

type MoveStoryUseCase struct {
	transactor transaction.Transactor
	articles   article.Repository
	recorder   audit.Recorder
}

type MoveStoryCommand struct {
	StoryID       uint32
	SiteKey       string
	Caller        ContentCaller
	SkipArticleID uint32
}

type StoryMover interface {
	MoveStoryThen(ctx context.Context, command MoveStoryCommand, then func(transaction.Repositories) error) (MoveStoryResult, error)
}

type MoveStoryResult struct {
	StoryID    uint32
	Site       site.Site
	ArticleIDs []uint32
}

type storyMove struct {
	result   MoveStoryResult
	moved    []article.Article
	origin   site.Site
	readable []article.Article
}

var _ StoryMover = &MoveStoryUseCase{}

func NewMoveStoryUseCase(transactor transaction.Transactor, articles article.Repository, recorder audit.Recorder) *MoveStoryUseCase {
	return &MoveStoryUseCase{transactor: transactor, articles: articles, recorder: recorder}
}

func (u *MoveStoryUseCase) MoveStory(ctx context.Context, command MoveStoryCommand) (MoveStoryResult, error) {
	return u.MoveStoryThen(ctx, command, nil)
}

func (u *MoveStoryUseCase) MoveStoryThen(ctx context.Context, command MoveStoryCommand, then func(transaction.Repositories) error) (MoveStoryResult, error) {
	if err := command.Caller.requireHolding(role.KeyContentUpdate, builtintype.KeyArticle); err != nil {
		return MoveStoryResult{}, err
	}
	var move storyMove
	var followUpErr error
	err := u.transactor.Run(ctx, func(tx transaction.Repositories) error {
		var err error
		if move, err = u.moveInTransaction(tx, command); err != nil {
			return err
		}
		if then != nil {
			followUpErr = then(tx)
		}
		return followUpErr
	})
	if followUpErr != nil {
		return MoveStoryResult{}, err
	}
	if errors.Is(err, article.ErrSlugTaken) {
		err = &article.SlugConflictError{}
	}
	if err != nil {
		u.recordRefusal(ctx, command, err)
		return MoveStoryResult{}, err
	}
	u.recordMoved(ctx, move)
	return move.result, nil
}

func (u *MoveStoryUseCase) moveInTransaction(tx transaction.Repositories, command MoveStoryCommand) (storyMove, error) {
	versions, readable, err := authorizedVersions(tx, command)
	if err != nil {
		return storyMove{}, err
	}
	destination, err := tx.Sites.GetByKey(command.SiteKey)
	if err != nil {
		return storyMove{}, err
	}
	if versions, readable, err = lockStorySites(tx, command, destination, versions, readable); err != nil {
		return storyMove{}, err
	}
	origin, err := tx.Sites.Get(readable[0].SiteID)
	if err != nil {
		return storyMove{}, err
	}
	move := storyMove{origin: origin, readable: readable, result: MoveStoryResult{StoryID: command.StoryID, Site: destination, ArticleIDs: idsOf(readable)}}
	if origin.ID == destination.ID {
		return move, nil
	}
	if err := checkDestination(tx, destination, versions, readable); err != nil {
		return storyMove{}, err
	}
	ordered := withoutArticle(sortByCreation(versions), command.SkipArticleID)
	if err := tx.Articles.MoveToSite(idsOf(ordered), destination.ID); err != nil {
		return storyMove{}, err
	}
	move.moved = ordered
	return move, nil
}

func withoutArticle(versions []article.Article, skipID uint32) []article.Article {
	return slices.DeleteFunc(slices.Clone(versions), func(version article.Article) bool { return version.ID == skipID })
}

func lockStorySites(tx transaction.Repositories, command MoveStoryCommand, destination site.Site, versions []article.Article, readable []article.Article) ([]article.Article, []article.Article, error) {
	locked := []uint32{}
	for attempt := 0; attempt < maxSiteLockRounds; attempt++ {
		needed := append(siteIDsOf(versions), destination.ID)
		if allLocked(locked, needed) {
			return versions, readable, nil
		}
		if err := lockSites(tx, needed); err != nil {
			return nil, nil, err
		}
		locked = needed
		var err error
		if versions, readable, err = authorizedVersions(tx, command); err != nil {
			return nil, nil, err
		}
	}
	return nil, nil, transaction.ErrLockContention
}

func allLocked(locked []uint32, needed []uint32) bool {
	for _, siteID := range needed {
		if !slices.Contains(locked, siteID) {
			return false
		}
	}
	return true
}

func authorizedVersions(tx transaction.Repositories, command MoveStoryCommand) ([]article.Article, []article.Article, error) {
	versions, err := tx.Articles.ListByStory(command.StoryID)
	if err != nil {
		return nil, nil, err
	}
	readable := sortByCreation(command.Caller.readableVersions(versions))
	if len(readable) == 0 {
		return nil, nil, article.ErrArticleNotFound
	}
	return versions, readable, requireUpdateOnAll(command.Caller, versions)
}

func siteIDsOf(versions []article.Article) []uint32 {
	siteIDs := []uint32{}
	for _, version := range versions {
		siteIDs = append(siteIDs, version.SiteID)
	}
	return siteIDs
}

func lockSites(tx transaction.Repositories, siteIDs []uint32) error {
	ordered := slices.Clone(siteIDs)
	slices.Sort(ordered)
	for _, siteID := range slices.Compact(ordered) {
		if err := tx.Sites.LockSite(siteID); err != nil {
			return err
		}
	}
	return nil
}

func requireUpdateOnAll(caller ContentCaller, versions []article.Article) error {
	for _, version := range versions {
		if err := caller.authorize(role.KeyContentUpdate, builtintype.KeyArticle, version.CreatedBy); err != nil {
			return err
		}
	}
	return nil
}

func checkDestination(tx transaction.Repositories, destination site.Site, versions []article.Article, readable []article.Article) error {
	rows, err := tx.Localization.Rows(destination.ID)
	if err != nil {
		return err
	}
	if missing := localization.MissingTags(rows, languagesOf(versions)); len(missing) > 0 {
		return &article.LanguageNotEnabledError{Missing: visibleTags(missing, readable)}
	}
	conflicting := []uint32{}
	taken := false
	for _, version := range sortByCreation(versions) {
		clash, err := tx.Articles.SlugTaken(destination.ID, version.Lang, version.Slug, 0)
		if err != nil {
			return err
		}
		taken = taken || clash
		if clash && slices.ContainsFunc(readable, func(candidate article.Article) bool { return candidate.ID == version.ID }) {
			conflicting = append(conflicting, version.ID)
		}
	}
	if taken {
		return &article.SlugConflictError{ArticleIDs: conflicting}
	}
	return nil
}

func visibleTags(missing []string, readable []article.Article) []string {
	visible := []string{}
	for _, tag := range missing {
		if slices.Contains(languagesOf(readable), tag) {
			visible = append(visible, tag)
		}
	}
	return visible
}

func idsOf(versions []article.Article) []uint32 {
	ids := make([]uint32, 0, len(versions))
	for _, version := range versions {
		ids = append(ids, version.ID)
	}
	return ids
}

func (u *MoveStoryUseCase) recordMoved(ctx context.Context, move storyMove) {
	for _, version := range move.moved {
		event := articleEvent(audit.ActionArticleEdit, version)
		event.Changes = []audit.Change{audit.TextChange(audit.FieldSite, move.origin.Name, move.result.Site.Name)}
		u.recorder.Record(ctx, event)
	}
}

func (u *MoveStoryUseCase) recordRefusal(ctx context.Context, command MoveStoryCommand, cause error) {
	if isNotFound(cause) || errors.Is(cause, role.ErrMissingPermission) {
		return
	}
	versions, err := u.articles.ListByStory(command.StoryID)
	readable := sortByCreation(command.Caller.readableVersions(versions))
	if err != nil || len(readable) == 0 {
		return
	}
	recordFailure(ctx, u.recorder, articleEvent(audit.ActionArticleEdit, readable[0]), cause)
}