package service

import (
	"context"
	"encoding/json"
	"fmt"
	"regexp"
	"strings"
	"time"

	"github.com/gochat/gochat/internal/model"
	"github.com/gochat/gochat/internal/repository"
	applogger "github.com/gochat/gochat/pkg/logger"
)

// ArticleService implements business logic for Article CRUD.
type ArticleService struct {
	repo          *repository.ArticleRepo
	searchIndexer SearchIndexer
}

func NewArticleService(repo *repository.ArticleRepo) *ArticleService {
	return &ArticleService{repo: repo}
}

func (s *ArticleService) SetSearchIndexer(indexer SearchIndexer) {
	s.searchIndexer = indexer
}

func (s *ArticleService) indexArticle(ctx context.Context, article *model.Article) {
	if s.searchIndexer != nil {
		logSearchIndexError("article", article.ID, s.searchIndexer.IndexArticle(ctx, article))
	}
}

func (s *ArticleService) deleteArticleIndex(ctx context.Context, accountID uint, id uint) {
	if s.searchIndexer != nil {
		logSearchIndexError("article", id, s.searchIndexer.DeleteArticle(ctx, accountID, id))
	}
}

// CreateArticleRequest is the DTO for creating an article.
type CreateArticleRequest struct {
	Title               string              `json:"title" validate:"required,min=2"`
	Slug                string              `json:"slug"`
	Description         string              `json:"description"`
	Content             string              `json:"content"`
	Status              model.ArticleStatus `json:"status"`
	FolderID            *uint               `json:"folder_id"`
	CategoryID          *uint               `json:"category_id"`
	AuthorID            *uint               `json:"author_id"`
	Position            int                 `json:"position"`
	Locale              string              `json:"locale"`
	AssociatedArticleID *uint               `json:"associated_article_id"`
	Meta                json.RawMessage     `json:"meta"`
	CustomAttributes    json.RawMessage     `json:"custom_attributes"`
}

// UpdateArticleRequest is the DTO for updating an article.
type UpdateArticleRequest struct {
	Title               *string              `json:"title"`
	Slug                *string              `json:"slug"`
	Description         *string              `json:"description"`
	Content             *string              `json:"content"`
	Status              *model.ArticleStatus `json:"status"`
	FolderID            *uint                `json:"folder_id"`
	CategoryID          *uint                `json:"category_id"`
	AuthorID            *uint                `json:"author_id"`
	Position            *int                 `json:"position"`
	Locale              *string              `json:"locale"`
	AssociatedArticleID *uint                `json:"associated_article_id"`
	Meta                *json.RawMessage     `json:"meta"`
	CustomAttributes    *json.RawMessage     `json:"custom_attributes"`
}

func (s *ArticleService) Create(ctx context.Context, portalID uint, authorID uint, req *CreateArticleRequest) (*model.Article, error) {
	return s.CreateWithAccount(ctx, 0, portalID, authorID, req)
}

func (s *ArticleService) CreateWithAccount(ctx context.Context, accountID uint, portalID uint, authorID uint, req *CreateArticleRequest) (*model.Article, error) {
	// Default status is draft if not specified
	status := string(req.Status)
	if status == "" {
		status = string(model.ArticleStatusDraft)
	}
	if req.AuthorID != nil {
		authorID = *req.AuthorID
	}
	slug := req.Slug
	if slug == "" {
		slug = articleSlug(req.Title)
	}

	article := &model.Article{
		AccountID:           accountID,
		PortalID:            portalID,
		AuthorID:            &authorID,
		Title:               req.Title,
		Slug:                slug,
		Description:         req.Description,
		Content:             req.Content,
		Status:              status,
		FolderID:            req.FolderID,
		CategoryID:          req.CategoryID,
		Position:            req.Position,
		Locale:              req.Locale,
		AssociatedArticleID: req.AssociatedArticleID,
		Meta:                req.Meta,
		CustomAttributes:    req.CustomAttributes,
	}

	if err := s.repo.Create(ctx, article); err != nil {
		return nil, fmt.Errorf("create article: %w", err)
	}

	// If associated_article_id is provided, link this article to the root article chain
	if req.AssociatedArticleID != nil {
		applogger.L().Debugf("Article %d linked to root article %d", article.ID, *req.AssociatedArticleID)
	}
	s.indexArticle(ctx, article)

	return s.repo.GetByPortalAndID(ctx, portalID, article.ID)
}

func (s *ArticleService) GetByID(ctx context.Context, id uint) (*model.Article, error) {
	article, err := s.repo.GetByID(ctx, id)
	if err != nil {
		return nil, fmt.Errorf("get article: %w", err)
	}
	return article, nil
}

func (s *ArticleService) GetByPortalAndID(ctx context.Context, portalID, id uint) (*model.Article, error) {
	article, err := s.repo.GetByPortalAndID(ctx, portalID, id)
	if err != nil {
		return nil, fmt.Errorf("get article: %w", err)
	}
	return article, nil
}

func (s *ArticleService) Update(ctx context.Context, id uint, req *UpdateArticleRequest) (*model.Article, error) {
	article, err := s.repo.GetByID(ctx, id)
	if err != nil {
		return nil, fmt.Errorf("find article: %w", err)
	}
	return s.UpdateExisting(ctx, article, req)
}

func (s *ArticleService) UpdateScoped(ctx context.Context, portalID, id uint, req *UpdateArticleRequest) (*model.Article, error) {
	article, err := s.repo.GetByPortalAndID(ctx, portalID, id)
	if err != nil {
		return nil, fmt.Errorf("find article: %w", err)
	}
	return s.UpdateExisting(ctx, article, req)
}

func (s *ArticleService) UpdateExisting(ctx context.Context, article *model.Article, req *UpdateArticleRequest) (*model.Article, error) {
	if article == nil {
		return nil, fmt.Errorf("find article: record not found")
	}
	// Update fields — only non-zero/non-nil values
	if req.Title != nil {
		article.Title = *req.Title
	}
	if req.Slug != nil {
		article.Slug = *req.Slug
	}
	if req.Description != nil {
		article.Description = *req.Description
	}
	if req.Content != nil {
		article.Content = *req.Content
	}
	if req.Status != nil {
		article.Status = string(*req.Status)
	}
	if req.FolderID != nil {
		article.FolderID = req.FolderID
	}
	if req.CategoryID != nil {
		article.CategoryID = req.CategoryID
	}
	if req.AuthorID != nil {
		article.AuthorID = req.AuthorID
	}
	if req.Position != nil {
		article.Position = *req.Position
	}
	if req.Locale != nil {
		article.Locale = *req.Locale
	}
	if req.AssociatedArticleID != nil {
		article.AssociatedArticleID = req.AssociatedArticleID
	}
	if req.Meta != nil {
		article.Meta = *req.Meta
	}
	if req.CustomAttributes != nil {
		article.CustomAttributes = *req.CustomAttributes
	}

	if err := s.repo.Update(ctx, article); err != nil {
		return nil, fmt.Errorf("update article: %w", err)
	}
	s.indexArticle(ctx, article)
	return s.repo.GetByPortalAndID(ctx, article.PortalID, article.ID)
}

func (s *ArticleService) Delete(ctx context.Context, id uint) error {
	// Check existence first — GORM Delete() returns nil even for non-existent IDs
	article, err := s.repo.GetByID(ctx, id)
	if err != nil {
		return fmt.Errorf("find article for delete: %w", err)
	}
	if err := s.repo.Delete(ctx, id); err != nil {
		return fmt.Errorf("delete article: %w", err)
	}
	s.deleteArticleIndex(ctx, article.AccountID, id)
	return nil
}

func (s *ArticleService) DeleteScoped(ctx context.Context, portalID, id uint) error {
	article, err := s.repo.GetByPortalAndID(ctx, portalID, id)
	if err != nil {
		return fmt.Errorf("find article for delete: %w", err)
	}
	if err := s.repo.Delete(ctx, id); err != nil {
		return fmt.Errorf("delete article: %w", err)
	}
	s.deleteArticleIndex(ctx, article.AccountID, id)
	return nil
}

// ListByPortalID returns articles for a portal with pagination.
func (s *ArticleService) ListByPortalID(ctx context.Context, portalID uint, page, perPage int) ([]model.Article, int64, error) {
	offset := (page - 1) * perPage
	articles, count, err := s.repo.FindByPortalID(ctx, portalID, offset, perPage)
	if err != nil {
		return nil, 0, fmt.Errorf("list articles: %w", err)
	}
	return articles, count, nil
}

// ListByCategoryID returns articles for a category with pagination.
func (s *ArticleService) ListByCategoryID(ctx context.Context, categoryID uint, page, perPage int) ([]model.Article, int64, error) {
	offset := (page - 1) * perPage
	articles, count, err := s.repo.FindByCategoryID(ctx, categoryID, offset, perPage)
	if err != nil {
		return nil, 0, fmt.Errorf("list articles by category: %w", err)
	}
	return articles, count, nil
}

// ListByStatus returns articles by status for a portal.
func (s *ArticleService) ListByStatus(ctx context.Context, portalID uint, status string, page, perPage int) ([]model.Article, int64, error) {
	offset := (page - 1) * perPage
	articles, count, err := s.repo.FindByStatus(ctx, portalID, model.ArticleStatus(status), offset, perPage)
	if err != nil {
		return nil, 0, fmt.Errorf("list articles by status: %w", err)
	}
	return articles, count, nil
}

// Search returns filtered + searched articles with pagination.
// Implements Article.search(params) from M9 spec.
func (s *ArticleService) Search(ctx context.Context, params repository.ArticleSearchParams) ([]model.Article, int64, error) {
	articles, count, err := s.repo.Search(ctx, params)
	if err != nil {
		return nil, 0, fmt.Errorf("search articles: %w", err)
	}
	return articles, count, nil
}

// StatusCounts returns article counts by status for a portal.
func (s *ArticleService) StatusCounts(ctx context.Context, portalID uint) (map[string]int64, error) {
	counts, err := s.repo.StatusCounts(ctx, portalID)
	if err != nil {
		return nil, fmt.Errorf("status counts: %w", err)
	}
	return counts, nil
}

type ArticleListMeta struct {
	AllArticlesCount      int64
	ArchivedArticlesCount int64
	ArticlesCount         int64
	DraftArticlesCount    int64
	MineArticlesCount     int64
	PublishedCount        int64
}

func (s *ArticleService) ListMeta(ctx context.Context, params repository.ArticleSearchParams, currentUserID uint) (*ArticleListMeta, error) {
	allCount, err := s.repo.CountSearch(ctx, repository.ArticleSearchParams{PortalID: params.PortalID})
	if err != nil {
		return nil, fmt.Errorf("count all articles: %w", err)
	}
	baseParams := params
	baseParams.Status = ""
	baseParams.AuthorID = nil
	articlesCount, err := s.repo.CountSearch(ctx, baseParams)
	if err != nil {
		return nil, fmt.Errorf("count articles: %w", err)
	}
	mineParams := baseParams
	if currentUserID != 0 {
		mineParams.AuthorID = &currentUserID
	}
	mineCount := int64(0)
	if currentUserID != 0 {
		mineCount, err = s.repo.CountSearch(ctx, mineParams)
		if err != nil {
			return nil, fmt.Errorf("count mine articles: %w", err)
		}
	}
	publishedParams := baseParams
	publishedParams.Status = string(model.ArticleStatusPublished)
	publishedCount, err := s.repo.CountSearch(ctx, publishedParams)
	if err != nil {
		return nil, fmt.Errorf("count published articles: %w", err)
	}
	draftParams := baseParams
	draftParams.Status = string(model.ArticleStatusDraft)
	draftCount, err := s.repo.CountSearch(ctx, draftParams)
	if err != nil {
		return nil, fmt.Errorf("count draft articles: %w", err)
	}
	archivedParams := baseParams
	archivedParams.Status = string(model.ArticleStatusArchived)
	archivedCount, err := s.repo.CountSearch(ctx, archivedParams)
	if err != nil {
		return nil, fmt.Errorf("count archived articles: %w", err)
	}
	return &ArticleListMeta{
		AllArticlesCount:      allCount,
		ArchivedArticlesCount: archivedCount,
		ArticlesCount:         articlesCount,
		DraftArticlesCount:    draftCount,
		MineArticlesCount:     mineCount,
		PublishedCount:        publishedCount,
	}, nil
}

// Reorder batch-updates article positions.
func (s *ArticleService) Reorder(ctx context.Context, positions map[uint]int) error {
	if err := s.repo.UpdatePositions(ctx, positions); err != nil {
		return fmt.Errorf("reorder articles: %w", err)
	}
	return nil
}

func (s *ArticleService) ReorderScoped(ctx context.Context, portalID uint, positions map[uint]int) error {
	if err := s.repo.UpdatePositionsForPortal(ctx, portalID, positions); err != nil {
		return fmt.Errorf("reorder articles: %w", err)
	}
	return nil
}

// BulkUpdateStatus updates status for multiple articles.
func (s *ArticleService) BulkUpdateStatus(ctx context.Context, ids []uint, status string) error {
	// Validate status
	validStatuses := map[model.ArticleStatus]bool{
		model.ArticleStatusDraft:     true,
		model.ArticleStatusPublished: true,
		model.ArticleStatusArchived:  true,
	}
	if !validStatuses[model.ArticleStatus(status)] {
		return fmt.Errorf("invalid status: %s", status)
	}
	if err := s.repo.BulkUpdateStatus(ctx, ids, status); err != nil {
		return fmt.Errorf("bulk update status: %w", err)
	}
	for _, id := range ids {
		article, err := s.repo.GetByID(ctx, id)
		if err == nil {
			s.indexArticle(ctx, article)
		}
	}
	return nil
}

func (s *ArticleService) BulkUpdateStatusScoped(ctx context.Context, portalID uint, ids []uint, status string) error {
	count, err := s.repo.CountByPortalAndIDs(ctx, portalID, ids)
	if err != nil {
		return fmt.Errorf("count articles: %w", err)
	}
	if count == 0 {
		return ErrArticleBulkNoArticles
	}
	if err := validateArticleBulkStatus(status); err != nil {
		return err
	}
	if err := s.repo.BulkUpdateStatusForPortal(ctx, portalID, ids, status); err != nil {
		return fmt.Errorf("bulk update status: %w", err)
	}
	return nil
}

func (s *ArticleService) BulkUpdateCategoryScoped(ctx context.Context, portalID uint, ids []uint, categoryID uint) error {
	count, err := s.repo.CountByPortalAndIDs(ctx, portalID, ids)
	if err != nil {
		return fmt.Errorf("count articles: %w", err)
	}
	if count == 0 {
		return ErrArticleBulkNoArticles
	}
	exists, err := s.repo.CategoryExistsForPortal(ctx, portalID, categoryID)
	if err != nil {
		return fmt.Errorf("find category: %w", err)
	}
	if !exists {
		return ErrArticleBulkCategoryNotFound
	}
	if err := s.repo.BulkUpdateCategoryForPortal(ctx, portalID, ids, categoryID); err != nil {
		return fmt.Errorf("bulk update category: %w", err)
	}
	return nil
}

// BulkDelete deletes multiple articles.
func (s *ArticleService) BulkDelete(ctx context.Context, ids []uint) error {
	articles := make([]*model.Article, 0, len(ids))
	for _, id := range ids {
		article, err := s.repo.GetByID(ctx, id)
		if err == nil {
			articles = append(articles, article)
		}
	}
	if err := s.repo.BulkDelete(ctx, ids); err != nil {
		return fmt.Errorf("bulk delete: %w", err)
	}
	for _, article := range articles {
		s.deleteArticleIndex(ctx, article.AccountID, article.ID)
	}
	return nil
}

func (s *ArticleService) BulkDeleteScoped(ctx context.Context, portalID uint, ids []uint) error {
	count, err := s.repo.CountByPortalAndIDs(ctx, portalID, ids)
	if err != nil {
		return fmt.Errorf("count articles: %w", err)
	}
	if count == 0 {
		return ErrArticleBulkNoArticles
	}
	if err := s.repo.BulkDeleteForPortal(ctx, portalID, ids); err != nil {
		return fmt.Errorf("bulk delete: %w", err)
	}
	return nil
}

// IncrementViews increments the view count for an article by 1.
func (s *ArticleService) IncrementViews(ctx context.Context, id uint) error {
	if err := s.repo.IncrementViews(ctx, id); err != nil {
		return fmt.Errorf("increment views: %w", err)
	}
	return nil
}

// BulkActionsRequest is the DTO for performing bulk operations on articles.
// Action can be "publish", "archive", or "delete".
type BulkActionsRequest struct {
	Action string `json:"action" validate:"required,oneof=publish archive delete"`
	IDs    []uint `json:"ids" validate:"required,min=1"`
}

// BulkActions dispatches a bulk operation (publish/archive/delete) on the given article IDs.
// Reference: Chatwoot articles_controller#bulk_actions
func (s *ArticleService) BulkActions(ctx context.Context, req *BulkActionsRequest) error {
	switch req.Action {
	case "publish":
		return s.BulkUpdateStatus(ctx, req.IDs, string(model.ArticleStatusPublished))
	case "archive":
		return s.BulkUpdateStatus(ctx, req.IDs, string(model.ArticleStatusArchived))
	case "delete":
		return s.BulkDelete(ctx, req.IDs)
	default:
		return fmt.Errorf("unsupported action: %s — must be publish, archive, or delete", req.Action)
	}
}

var (
	ErrArticleBulkNoArticles       = fmt.Errorf("no articles found")
	ErrArticleBulkInvalidStatus    = fmt.Errorf("invalid status")
	ErrArticleBulkCategoryNotFound = fmt.Errorf("category not found")
)

func validateArticleBulkStatus(status string) error {
	validStatuses := map[model.ArticleStatus]bool{
		model.ArticleStatusDraft:     true,
		model.ArticleStatusPublished: true,
		model.ArticleStatusArchived:  true,
	}
	if !validStatuses[model.ArticleStatus(status)] {
		return ErrArticleBulkInvalidStatus
	}
	return nil
}

func articleSlug(title string) string {
	slug := strings.ToLower(strings.TrimSpace(title))
	slug = regexp.MustCompile(`[^a-z0-9]+`).ReplaceAllString(slug, "-")
	slug = strings.Trim(slug, "-")
	if slug == "" {
		slug = "article"
	}
	return fmt.Sprintf("%d-%s", time.Now().UTC().Unix(), slug)
}