package handlers

import (
	"context"
	"fmt"
	"net/http"
	"strings"
	"time"

	"github.com/google/uuid"
	"github.com/jackc/pgx/v5"
	"github.com/jackc/pgx/v5/pgxpool"
)

type AttachmentDTO struct {
	ID           string  `json:"id"`
	Kind         string  `json:"kind"`
	URL          string  `json:"url"`
	Mime         string  `json:"mime"`
	Filename     string  `json:"filename"`
	SizeBytes    int64   `json:"sizeBytes"`
	Width        *int    `json:"width,omitempty"`
	Height       *int    `json:"height,omitempty"`
	DurationSec  *int    `json:"durationSec,omitempty"`
	PosterURL    string  `json:"posterUrl,omitempty"`
	ThumbnailURL string  `json:"thumbnailUrl,omitempty"`
}

type PostDTO struct {
	ID             string          `json:"id"`
	PostType       string          `json:"postType"`
	CategoryID     int             `json:"categoryId,omitempty"`
	CategorySlug   string          `json:"categorySlug,omitempty"`
	Language       string                       `json:"language"` // UI locale from ?lang= (matches text selection)
	SourceLanguage string                       `json:"sourceLanguage,omitempty"` // DB source metadata (admin input language)
	Text           string                       `json:"text,omitempty"`
	Localizations  map[string]postLocalePayload `json:"localizations"`
	Attachments    []AttachmentDTO              `json:"attachments"`
	IsRecommended  bool            `json:"isRecommended"`
	PublishedAt    string          `json:"publishedAt"`
	UpdatedAt      string          `json:"updatedAt"`
	CreatedAt      string          `json:"createdAt,omitempty"`
	Tags           []string        `json:"tags,omitempty"`
}

type PostListResponse struct {
	Items      []PostDTO `json:"items"`
	NextCursor string    `json:"nextCursor,omitempty"`
}

type attachmentInput struct {
	ID           string `json:"id"`
	Kind         string `json:"kind"`
	URL          string `json:"url"`
	Mime         string `json:"mime"`
	Filename     string `json:"filename"`
	SizeBytes    int64  `json:"sizeBytes"`
	Width        *int   `json:"width"`
	Height       *int   `json:"height"`
	DurationSec  *int   `json:"durationSec"`
	PosterURL    string `json:"posterUrl"`
	ThumbnailURL string `json:"thumbnailUrl"`
	SortOrder    int    `json:"sortOrder"`
}

type adminPost struct {
	ID             string                       `json:"id"`
	PostType       string                       `json:"postType"`
	CategoryID     int                          `json:"categoryId,omitempty"`
	CategorySlug   string                       `json:"categorySlug,omitempty"`
	Language       string                       `json:"language"`
	Text           string                       `json:"text"`
	Attachments    []attachmentInput            `json:"attachments"`
	IsPublic       bool                         `json:"isPublic"`
	IsRecommended  bool                         `json:"isRecommended"`
	SortOrder      int                          `json:"sortOrder"`
	Status         string                       `json:"status"`
	PublishedAt    *string                      `json:"publishedAt,omitempty"`
	CreatedAt      string                       `json:"createdAt,omitempty"`
	UpdatedAt      string                       `json:"updatedAt,omitempty"`
	Tags           []string                     `json:"tags,omitempty"`
	Localizations  map[string]postLocalePayload `json:"localizations,omitempty"`
	ViewCount      int                          `json:"viewCount,omitempty"`
	DownloadCount  int                          `json:"downloadCount,omitempty"`
}

const publicPostWhere = `p.status = 'published' AND p.is_public = TRUE AND (p.published_at IS NULL OR p.published_at <= NOW())`

func parsePublishedAtPtr(s *string) (*time.Time, error) {
	if s == nil || strings.TrimSpace(*s) == "" {
		return nil, nil
	}
	t, err := time.Parse(time.RFC3339, strings.TrimSpace(*s))
	if err != nil {
		t, err = time.Parse(time.RFC3339Nano, strings.TrimSpace(*s))
	}
	if err != nil {
		return nil, err
	}
	utc := t.UTC()
	return &utc, nil
}

func resolvePostPublishedAt(pubIn *string, status string, existing *time.Time, isCreate bool) (*time.Time, error) {
	if pubIn != nil && strings.TrimSpace(*pubIn) != "" {
		return parsePublishedAtPtr(pubIn)
	}
	if status == "published" {
		if isCreate || existing == nil {
			t := time.Now().UTC()
			return &t, nil
		}
		return existing, nil
	}
	return existing, nil
}

func formatTimePtr(t *time.Time) string {
	if t == nil {
		return ""
	}
	return t.UTC().Format(time.RFC3339)
}

func encodePostCursor(pub time.Time, id uuid.UUID) string {
	return pub.UTC().Format(time.RFC3339Nano) + "|" + id.String()
}

func decodePostCursor(cursor string) (time.Time, uuid.UUID, error) {
	parts := strings.SplitN(cursor, "|", 2)
	if len(parts) != 2 {
		return time.Time{}, uuid.Nil, fmt.Errorf("bad cursor")
	}
	t, err := time.Parse(time.RFC3339Nano, parts[0])
	if err != nil {
		t, err = time.Parse(time.RFC3339, parts[0])
	}
	if err != nil {
		return time.Time{}, uuid.Nil, err
	}
	id, err := uuid.Parse(parts[1])
	if err != nil {
		return time.Time{}, uuid.Nil, err
	}
	return t.UTC(), id, nil
}

func postTypeFilterSQL(typ string, args *[]any) string {
	raw := strings.ToLower(strings.TrimSpace(typ))
	if raw == "" || raw == "all" {
		return ""
	}
	typ = normalizePostType(typ)
	*args = append(*args, typ)
	n := len(*args)
	// Primary: admin-selected post_type; legacy rows fall back via OR attachment heuristics.
	switch typ {
	case "image":
		return fmt.Sprintf(` AND (p.post_type = $%d OR (COALESCE(p.post_type,'') = 'text' AND EXISTS (
			SELECT 1 FROM post_attachments pa WHERE pa.post_id = p.id AND pa.kind = 'image')))`, n)
	case "video":
		return fmt.Sprintf(` AND (p.post_type = $%d OR (COALESCE(p.post_type,'') = 'text' AND EXISTS (
			SELECT 1 FROM post_attachments pa WHERE pa.post_id = p.id AND (pa.kind = 'video' OR pa.mime LIKE 'video/%%'))))`, n)
	case "music":
		return fmt.Sprintf(` AND (p.post_type = $%d OR (COALESCE(p.post_type,'') = 'text' AND EXISTS (
			SELECT 1 FROM post_attachments pa WHERE pa.post_id = p.id AND (pa.mime LIKE 'audio/%%' OR pa.filename ILIKE '%%.mp3' OR pa.filename ILIKE '%%.wav' OR pa.filename ILIKE '%%.m4a'))))`, n)
	case "pdf":
		return fmt.Sprintf(` AND (p.post_type = $%d OR EXISTS (
			SELECT 1 FROM post_attachments pa WHERE pa.post_id = p.id AND pa.kind = 'document' AND (pa.mime ILIKE '%%pdf%%' OR pa.filename ILIKE '%%.pdf')))`, n)
	case "ppt":
		return fmt.Sprintf(` AND (p.post_type = $%d OR EXISTS (
			SELECT 1 FROM post_attachments pa WHERE pa.post_id = p.id AND pa.kind = 'document' AND (pa.mime ILIKE '%%presentation%%' OR pa.filename ILIKE '%%.ppt%%' OR pa.filename ILIKE '%%.pptx%%')))`, n)
	case "archive":
		return fmt.Sprintf(` AND (p.post_type = $%d OR EXISTS (
			SELECT 1 FROM post_attachments pa WHERE pa.post_id = p.id AND pa.kind = 'document' AND (pa.filename ILIKE '%%.zip%%' OR pa.filename ILIKE '%%.rar%%' OR pa.filename ILIKE '%%.7z%%')))`, n)
	case "text":
		return fmt.Sprintf(` AND p.post_type = $%d`, n)
	case "link":
		return fmt.Sprintf(` AND (p.post_type = $%d OR (p.text_zh ~* 'https?://' OR p.text_en ~* 'https?://' OR p.text_ms ~* 'https?://'))`, n)
	default:
		return fmt.Sprintf(` AND p.post_type = $%d`, n)
	}
}

func normalizePostLangFilter(lang string) string {
	lang = strings.TrimSpace(lang)
	if lang == "" {
		return ""
	}
	return translateNormalizePostLang(lang)
}

func translateNormalizePostLang(lang string) string {
	lang = strings.ToLower(lang)
	switch {
	case strings.HasPrefix(lang, "zh"):
		return "zh"
	case strings.HasPrefix(lang, "en"):
		return "en"
	case strings.HasPrefix(lang, "ja"):
		return "ja"
	case strings.HasPrefix(lang, "ko"):
		return "ko"
	case strings.HasPrefix(lang, "vi"):
		return "vi"
	case lang == "id", strings.HasPrefix(lang, "in"):
		return "id"
	case strings.HasPrefix(lang, "ms"):
		return "ms"
	default:
		return lang
	}
}

func validateAdminPost(ap *adminPost) error {
	ap.PostType = inferPostTypeFromContent(ap.Text, ap.Attachments)
	if !validPostTypes[ap.PostType] {
		ap.PostType = "text"
	}
	if len(ap.Attachments) > maxPostAttachments {
		return fmt.Errorf("too many attachments (max %d)", maxPostAttachments)
	}
	hasText := strings.TrimSpace(ap.Text) != ""
	hasAtt := len(ap.Attachments) > 0
	if ap.Status == "published" && !hasText && !hasAtt {
		return fmt.Errorf("published post requires text and/or at least one attachment")
	}
	if ap.Status == "published" && ap.CategoryID <= 0 {
		return fmt.Errorf("published post requires categoryId")
	}
	for i, a := range ap.Attachments {
		if strings.TrimSpace(a.URL) == "" {
			return fmt.Errorf("attachment %d: url required", i)
		}
		k := strings.TrimSpace(a.Kind)
		if k != "image" && k != "video" && k != "document" {
			return fmt.Errorf("attachment %d: invalid kind", i)
		}
	}
	if ap.Status == "" {
		ap.Status = "draft"
	}
	normalized, err := normalizeAdminPostTags(ap.Tags)
	if err != nil {
		return err
	}
	ap.Tags = normalized
	return nil
}

func loadAttachmentsByPostIDs(ctx context.Context, pool *pgxpool.Pool, ids []uuid.UUID) (map[uuid.UUID][]AttachmentDTO, error) {
	out := make(map[uuid.UUID][]AttachmentDTO)
	if len(ids) == 0 {
		return out, nil
	}
	rows, err := pool.Query(ctx, `
		SELECT id, post_id, kind, url, mime, filename, size_bytes, width, height, duration_sec,
			COALESCE(poster_url,''), COALESCE(thumbnail_url,''), sort_order
		FROM post_attachments WHERE post_id = ANY($1)
		ORDER BY post_id, sort_order ASC, id ASC`, ids)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	for rows.Next() {
		var aid, pid uuid.UUID
		var a AttachmentDTO
		var kind, url, mime, filename string
		var size int64
		var w, h, dur *int
		var poster, thumb string
		var sort int
		if err := rows.Scan(&aid, &pid, &kind, &url, &mime, &filename, &size, &w, &h, &dur, &poster, &thumb, &sort); err != nil {
			return nil, err
		}
		a.ID = aid.String()
		a.Kind = kind
		a.URL = url
		a.Mime = mime
		a.Filename = filename
		a.SizeBytes = size
		a.Width = w
		a.Height = h
		a.DurationSec = dur
		a.PosterURL = poster
		a.ThumbnailURL = thumb
		out[pid] = append(out[pid], a)
	}
	return out, rows.Err()
}

func loadPostTagNames(ctx context.Context, pool *pgxpool.Pool, postID uuid.UUID, lang string) ([]string, error) {
	rows, err := pool.Query(ctx, `
		SELECT t.name, COALESCE(t.name_en,''), COALESCE(t.name_ja,''), COALESCE(t.name_ko,''),
			COALESCE(t.name_vi,''), COALESCE(t.name_id,''), COALESCE(t.name_ms,''), t.slug
		FROM post_tags pt JOIN tags t ON t.id = pt.tag_id
		WHERE pt.post_id = $1 ORDER BY t.slug`, postID)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	var names []string
	for rows.Next() {
		var name, en, ja, ko, vi, id, ms, slug string
		if err := rows.Scan(&name, &en, &ja, &ko, &vi, &id, &ms, &slug); err != nil {
			return nil, err
		}
		names = append(names, tagDisplayName(name, en, ja, ko, vi, id, ms, lang))
	}
	return names, rows.Err()
}

func replacePostTags(ctx context.Context, pool *pgxpool.Pool, postID uuid.UUID, tagSlugs []string) error {
	_, err := pool.Exec(ctx, `DELETE FROM post_tags WHERE post_id = $1`, postID)
	if err != nil {
		return err
	}
	for _, slug := range tagSlugs {
		slug = strings.TrimSpace(slug)
		if slug == "" {
			continue
		}
		var tid int
		err := pool.QueryRow(ctx, `SELECT id FROM tags WHERE slug = $1`, slug).Scan(&tid)
		if err != nil {
			continue
		}
		_, _ = pool.Exec(ctx, `INSERT INTO post_tags (post_id, tag_id) VALUES ($1,$2) ON CONFLICT DO NOTHING`, postID, tid)
	}
	return nil
}

func replacePostAttachments(ctx context.Context, pool *pgxpool.Pool, postID uuid.UUID, inputs []attachmentInput) error {
	_, err := pool.Exec(ctx, `DELETE FROM post_attachments WHERE post_id = $1`, postID)
	if err != nil {
		return err
	}
	for i, in := range inputs {
		kind := strings.TrimSpace(in.Kind)
		if kind == "" {
			kind = classifyAttachmentKind(in.Mime, in.Filename)
		}
		sort := in.SortOrder
		if sort == 0 {
			sort = i
		}
		_, err := pool.Exec(ctx, `
			INSERT INTO post_attachments (post_id, kind, url, mime, filename, size_bytes, width, height, duration_sec, poster_url, thumbnail_url, sort_order)
			VALUES ($1,$2,$3,$4,$5,$6,$7,$8,$9,$10,$11,$12)`,
			postID, kind, strings.TrimSpace(in.URL), nullIfEmptyStr(in.Mime, "application/octet-stream"),
			nullIfEmptyStr(in.Filename, "file"), in.SizeBytes,
			in.Width, in.Height, in.DurationSec,
			nullIfEmpty(in.PosterURL), nullIfEmpty(in.ThumbnailURL), sort)
		if err != nil {
			return err
		}
	}
	return nil
}

func classifyAttachmentKind(mime, filename string) string {
	m := strings.ToLower(mime)
	if strings.HasPrefix(m, "image/") {
		return "image"
	}
	if strings.HasPrefix(m, "video/") {
		return "video"
	}
	fn := strings.ToLower(filename)
	if strings.HasSuffix(fn, ".jpg") || strings.HasSuffix(fn, ".jpeg") || strings.HasSuffix(fn, ".png") || strings.HasSuffix(fn, ".gif") || strings.HasSuffix(fn, ".webp") {
		return "image"
	}
	if strings.HasSuffix(fn, ".mp4") || strings.HasSuffix(fn, ".mov") || strings.HasSuffix(fn, ".webm") {
		return "video"
	}
	return "document"
}

func postCategoryIDArg(id int) any {
	if id <= 0 {
		return nil
	}
	return id
}

func nullIfEmptyStr(s, def string) string {
	if strings.TrimSpace(s) == "" {
		return def
	}
	return s
}

func scanPostRow(r *http.Request, row pgx.Row) (PostDTO, postTextI18n, error) {
	var dto PostDTO
	var texts postTextI18n
	var id uuid.UUID
	var catID *int
	var slug *string
	var sourceLang, postType string
	var pub, updated, created *time.Time
	err := row.Scan(
		&id, &texts.TextZh, &texts.TextEn, &texts.TextJa, &texts.TextKo, &texts.TextVi, &texts.TextId, &texts.TextMs,
		&sourceLang, &postType, &catID, &slug, &dto.IsRecommended, &pub, &updated, &created,
	)
	if err != nil {
		return dto, texts, err
	}
	dto.ID = id.String()
	dto.PostType = normalizePostType(postType)
	if catID != nil {
		dto.CategoryID = *catID
	}
	if slug != nil {
		dto.CategorySlug = *slug
	}
	dto.SourceLanguage = sourceLang
	dto.Language = requestLangCode(r)
	dto.Text = texts.pick(r)
	dto.Localizations = texts.toLocalizations()
	if pub != nil {
		dto.PublishedAt = pub.UTC().Format(time.RFC3339)
	} else if created != nil {
		dto.PublishedAt = created.UTC().Format(time.RFC3339)
	}
	if updated != nil {
		dto.UpdatedAt = updated.UTC().Format(time.RFC3339)
	}
	if created != nil {
		dto.CreatedAt = created.UTC().Format(time.RFC3339)
	}
	return dto, texts, nil
}

func postSelectBase() string {
	return `
		SELECT p.id, ` + postI18nColsSQL + `, COALESCE(p.language,'zh'), COALESCE(p.post_type,'text'),
			p.category_id, c.slug,
			p.is_recommended, p.published_at, p.updated_at, p.created_at
		FROM posts p
		LEFT JOIN categories c ON c.id = p.category_id`
}

func postsFromClause() string {
	return `FROM posts p LEFT JOIN categories c ON c.id = p.category_id WHERE 1=1`
}

func postLimitDef(r *http.Request, def, max int) int {
	limit := atoiDef(r.URL.Query().Get("limit"), def)
	if limit > max {
		limit = max
	}
	return limit
}

func postLanguageFilterSQL(lang string, args *[]any) string {
	norm := normalizePostLangFilter(lang)
	if norm == "" {
		return ""
	}
	*args = append(*args, norm)
	return fmt.Sprintf(` AND p.language = $%d`, len(*args))
}