package persistence

import (
	domain "RenewCMS/internal/domain/author"
	"RenewCMS/internal/infrastructure/persistence/mappers"
	entity "RenewCMS/internal/infrastructure/persistence/models"
	"strings"

	"gorm.io/gorm"
	"gorm.io/gorm/clause"
)

type AuthorRepository struct {
	db *gorm.DB
}

func NewAuthorRepository(db *gorm.DB) *AuthorRepository {
	return &AuthorRepository{db}
}

type creditTotal struct {
	AuthorID uint32
	Total    int
}

func creditCounts(db *gorm.DB, authorIDs []uint32) (map[uint32]int, error) {
	counts := make(map[uint32]int, len(authorIDs))
	if len(authorIDs) == 0 {
		return counts, nil
	}
	var totals []creditTotal
	err := db.Table("article_authors").
		Select("article_authors.author_id AS author_id, COUNT(*) AS total").
		Joins("JOIN articles ON articles.id = article_authors.article_id").
		Where("articles.deleted_at IS NULL").
		Where("article_authors.author_id IN ?", authorIDs).
		Group("article_authors.author_id").
		Scan(&totals).Error
	if err != nil {
		return nil, err
	}
	for _, total := range totals {
		counts[total.AuthorID] = total.Total
	}
	return counts, nil
}

func (a *AuthorRepository) toDomain(db *gorm.DB, models []entity.Author) ([]domain.Author, error) {
	ids := make([]uint32, 0, len(models))
	for _, model := range models {
		ids = append(ids, model.ID)
	}
	counts, err := creditCounts(db, ids)
	if err != nil {
		return nil, err
	}
	authors := make([]domain.Author, 0, len(models))
	for _, model := range models {
		authors = append(authors, mappers.AuthorToDomain(model, counts[model.ID]))
	}
	return authors, nil
}

func (a *AuthorRepository) loadOne(db *gorm.DB, model entity.Author) (domain.Author, error) {
	authors, err := a.toDomain(db, []entity.Author{model})
	if err != nil {
		return domain.Author{}, err
	}
	return authors[0], nil
}

func (a *AuthorRepository) List(query domain.ListQuery) (domain.Page, error) {
	query.Page = max(query.Page, 1)
	query.Size = max(query.Size, 0)
	needle := strings.TrimSpace(query.Q)
	if needle != "" {
		return a.findMatching(query, foldForSearch(needle))
	}
	var total int64
	if err := a.db.Model(&entity.Author{}).Count(&total).Error; err != nil {
		return domain.Page{}, err
	}
	var found []entity.Author
	err := a.db.Order("id DESC").Limit(query.Size).Offset(pageStart(query.Page, query.Size, int(total))).Find(&found).Error
	if err != nil {
		return domain.Page{}, err
	}
	items, err := a.toDomain(a.db, found)
	if err != nil {
		return domain.Page{}, err
	}
	return domain.Page{Items: items, Total: int(total)}, nil
}

func pageStart(page int, size int, total int) int {
	if size <= 0 || page-1 > total/size {
		return total
	}
	return min((page-1)*size, total)
}

func (a *AuthorRepository) findMatching(query domain.ListQuery, needle string) (domain.Page, error) {
	var candidates []entity.Author
	if err := a.db.Select("id", "name", "slug").Order("id DESC").Find(&candidates).Error; err != nil {
		return domain.Page{}, err
	}
	matching := make([]uint32, 0)
	for _, candidate := range candidates {
		if strings.Contains(foldForSearch(candidate.Name), needle) || strings.Contains(foldForSearch(candidate.Slug), needle) {
			matching = append(matching, candidate.ID)
		}
	}
	start := pageStart(query.Page, query.Size, len(matching))
	end := min(start+query.Size, len(matching))
	page := domain.Page{Items: []domain.Author{}, Total: len(matching)}
	if start == end {
		return page, nil
	}
	var found []entity.Author
	if err := a.db.Where("id IN ?", matching[start:end]).Order("id DESC").Find(&found).Error; err != nil {
		return domain.Page{}, err
	}
	items, err := a.toDomain(a.db, found)
	if err != nil {
		return domain.Page{}, err
	}
	page.Items = items
	return page, nil
}

func (a *AuthorRepository) Get(id uint32) (domain.Author, error) {
	var model entity.Author
	if err := a.db.First(&model, id).Error; err != nil {
		return domain.Author{}, mapNotFoundErr(err, domain.ErrAuthorNotFound)
	}
	return a.loadOne(a.db, model)
}

func (a *AuthorRepository) GetBySlug(slug string) (domain.Author, error) {
	var model entity.Author
	if err := a.db.Where("slug = ?", slug).First(&model).Error; err != nil {
		return domain.Author{}, mapNotFoundErr(err, domain.ErrAuthorNotFound)
	}
	return a.loadOne(a.db, model)
}

func (a *AuthorRepository) GetByUserID(userID uint32) (domain.Author, error) {
	var model entity.Author
	if err := a.db.Where("user_id = ?", userID).First(&model).Error; err != nil {
		return domain.Author{}, mapNotFoundErr(err, domain.ErrAuthorNotFound)
	}
	return a.loadOne(a.db, model)
}

func slugInUse(tx *gorm.DB, slug string, exceptID uint32) (bool, error) {
	var total int64
	err := tx.Model(&entity.Author{}).Where("slug = ? AND id <> ?", slug, exceptID).Count(&total).Error
	return total > 0, err
}

func userInUse(tx *gorm.DB, userID *uint32, exceptID uint32) (bool, error) {
	if userID == nil {
		return false, nil
	}
	var total int64
	err := tx.Model(&entity.Author{}).Where("user_id = ? AND id <> ?", *userID, exceptID).Count(&total).Error
	return total > 0, err
}

func ensureUnique(tx *gorm.DB, author domain.Author) error {
	taken, err := slugInUse(tx, author.Slug, author.ID)
	if err != nil {
		return err
	}
	if taken {
		return domain.ErrSlugTaken
	}
	linked, err := userInUse(tx, author.UserID, author.ID)
	if err != nil {
		return err
	}
	if linked {
		return domain.ErrUserAlreadyLinked
	}
	return nil
}

func (a *AuthorRepository) explainWriteFailure(author domain.Author, cause error) error {
	if err := ensureUnique(a.db, author); err != nil {
		return err
	}
	return cause
}

func (a *AuthorRepository) Create(author domain.Author) (domain.Author, error) {
	model := mappers.AuthorToModel(author)
	model.ID = 0
	author.ID = 0
	err := a.db.Transaction(func(tx *gorm.DB) error {
		if err := ensureUnique(tx, author); err != nil {
			return err
		}
		return tx.Create(&model).Error
	})
	if err != nil {
		return domain.Author{}, a.explainWriteFailure(author, err)
	}
	return mappers.AuthorToDomain(model, 0), nil
}

func (a *AuthorRepository) Update(author domain.Author) (domain.Author, error) {
	changes := map[string]any{
		"name":         author.Name,
		"slug":         author.Slug,
		"bio":          author.Bio,
		"avatar_id":    author.AvatarID,
		"website":      author.Website,
		"social_links": mappers.AuthorToModel(author).SocialLinks,
		"user_id":      author.UserID,
	}
	err := a.db.Transaction(func(tx *gorm.DB) error {
		if _, err := lockAuthor(tx, author.ID); err != nil {
			return err
		}
		if err := ensureUnique(tx, author); err != nil {
			return err
		}
		return tx.Model(&entity.Author{}).Where("id = ?", author.ID).Updates(changes).Error
	})
	if err != nil {
		return domain.Author{}, a.explainWriteFailure(author, err)
	}
	return a.Get(author.ID)
}

func lockAuthor(tx *gorm.DB, id uint32) (entity.Author, error) {
	var locked entity.Author
	if err := tx.Clauses(clause.Locking{Strength: "UPDATE"}).First(&locked, id).Error; err != nil {
		return entity.Author{}, mapNotFoundErr(err, domain.ErrAuthorNotFound)
	}
	return locked, nil
}

func (a *AuthorRepository) DeleteMovingCredits(id uint32, reassignTo *uint32) error {
	return a.db.Transaction(func(tx *gorm.DB) error {
		if _, err := lockAuthor(tx, id); err != nil {
			return err
		}
		if reassignTo == nil {
			credited, err := hasCredits(tx, id)
			if err != nil {
				return err
			}
			if credited {
				return domain.ErrAuthorHasArticles
			}
			return removeAuthor(tx, id)
		}
		if _, err := lockAuthor(tx, *reassignTo); err != nil {
			return err
		}
		if err := moveCredits(tx, id, *reassignTo); err != nil {
			return err
		}
		return removeAuthor(tx, id)
	})
}

func (a *AuthorRepository) DeleteUncrediting(id uint32) error {
	return a.db.Transaction(func(tx *gorm.DB) error {
		if _, err := lockAuthor(tx, id); err != nil {
			return err
		}
		return removeAuthor(tx, id)
	})
}

func hasCredits(tx *gorm.DB, id uint32) (bool, error) {
	var total int64
	err := tx.Model(&entity.ArticleAuthor{}).Where("author_id = ?", id).Count(&total).Error
	return total > 0, err
}

func removeAuthor(tx *gorm.DB, id uint32) error {
	if err := tx.Where("author_id = ?", id).Delete(&entity.ArticleAuthor{}).Error; err != nil {
		return err
	}
	return deleteOrNotFound(tx.Delete(&entity.Author{}, id), domain.ErrAuthorNotFound)
}

func moveCredits(tx *gorm.DB, from uint32, to uint32) error {
	var alreadyCredited []uint32
	if err := tx.Model(&entity.ArticleAuthor{}).Where("author_id = ?", to).Pluck("article_id", &alreadyCredited).Error; err != nil {
		return err
	}
	if len(alreadyCredited) > 0 {
		if err := tx.Where("author_id = ? AND article_id IN ?", from, alreadyCredited).Delete(&entity.ArticleAuthor{}).Error; err != nil {
			return err
		}
	}
	return tx.Model(&entity.ArticleAuthor{}).Where("author_id = ?", from).UpdateColumn("author_id", to).Error
}

type avatarTotal struct {
	AvatarID uint32
	Total    int
}

func (a *AuthorRepository) AvatarUsage() (map[uint32]int, error) {
	var totals []avatarTotal
	err := a.db.Model(&entity.Author{}).Select("avatar_id, COUNT(*) AS total").Where("avatar_id IS NOT NULL").Group("avatar_id").Scan(&totals).Error
	if err != nil {
		return nil, err
	}
	usage := make(map[uint32]int, len(totals))
	for _, total := range totals {
		usage[total.AvatarID] = total.Total
	}
	return usage, nil
}

func (a *AuthorRepository) ClearAvatar(imageID uint32) ([]uint32, error) {
	ids := []uint32{}
	err := a.db.Transaction(func(tx *gorm.DB) error {
		if err := tx.Model(&entity.Author{}).Where("avatar_id = ?", imageID).Order("id ASC").Pluck("id", &ids).Error; err != nil {
			return err
		}
		if len(ids) == 0 {
			return nil
		}
		return tx.Model(&entity.Author{}).Where("id IN ?", ids).UpdateColumn("avatar_id", nil).Error
	})
	if err != nil {
		return nil, err
	}
	return ids, nil
}

func (a *AuthorRepository) AssignAvatar(authorIDs []uint32, imageID uint32) error {
	if len(authorIDs) == 0 {
		return nil
	}
	return a.db.Model(&entity.Author{}).Where("id IN ?", authorIDs).UpdateColumn("avatar_id", imageID).Error
}

func (a *AuthorRepository) RepointAvatar(fromImageIDs []uint32, toImageID uint32) (int, error) {
	if len(fromImageIDs) == 0 {
		return 0, nil
	}
	result := a.db.Model(&entity.Author{}).Where("avatar_id IN ?", fromImageIDs).UpdateColumn("avatar_id", toImageID)
	if result.Error != nil {
		return 0, result.Error
	}
	return int(result.RowsAffected), nil
}

var _ domain.Repository = &AuthorRepository{}