package handlers

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

	"github.com/go-chi/chi/v5"
	"github.com/google/uuid"
	"github.com/jackc/pgx/v5"
)

func ListPosts(w http.ResponseWriter, r *http.Request) {
	listPostsQuery(w, r, false)
}

func ListPostsRecommended(w http.ResponseWriter, r *http.Request) {
	pool := poolFrom(r)
	limit := postLimitDef(r, 12, 50)
	rows, err := pool.Query(r.Context(), postSelectBase()+`
		WHERE `+publicPostWhere+` AND p.is_recommended = TRUE
		ORDER BY p.sort_order ASC, p.published_at DESC NULLS LAST, p.id DESC
		LIMIT $1`, limit)
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
	items, err := collectPostRows(r, rows)
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
	writeJSON(w, map[string]any{"items": items})
}

func ListPostsLatest(w http.ResponseWriter, r *http.Request) {
	pool := poolFrom(r)
	limit := postLimitDef(r, 8, 50)
	rows, err := pool.Query(r.Context(), postSelectBase()+`
		WHERE `+publicPostWhere+`
		ORDER BY p.published_at DESC NULLS LAST, p.id DESC
		LIMIT $1`, limit)
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
	items, err := collectPostRows(r, rows)
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
	writeJSON(w, map[string]any{"items": items})
}

func SearchPosts(w http.ResponseWriter, r *http.Request) {
	q := strings.TrimSpace(r.URL.Query().Get("q"))
	if q == "" {
		writeJSON(w, PostListResponse{Items: []PostDTO{}})
		return
	}
	listPostsQuery(w, r, true)
}

func GetPost(w http.ResponseWriter, r *http.Request) {
	pool := poolFrom(r)
	id, err := uuid.Parse(chi.URLParam(r, "id"))
	if err != nil {
		http.Error(w, "bad id", http.StatusBadRequest)
		return
	}
	row := pool.QueryRow(r.Context(), postSelectBase()+`
		WHERE p.id = $1 AND `+publicPostWhere, id)
	dto, _, err := scanPostRow(r, row)
	if err != nil {
		if err == pgx.ErrNoRows {
			http.NotFound(w, r)
			return
		}
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
	atts, _ := loadAttachmentsByPostIDs(r.Context(), pool, []uuid.UUID{id})
	dto.Attachments = atts[id]
	if dto.Attachments == nil {
		dto.Attachments = []AttachmentDTO{}
	}
	tags, _ := loadPostTagNames(r.Context(), pool, id, requestLangCode(r))
	if tags == nil {
		tags = []string{}
	}
	dto.Tags = tags
	writeJSON(w, dto)
}

func PostAttachmentDownload(w http.ResponseWriter, r *http.Request) {
	pool := poolFrom(r)
	postID, err := uuid.Parse(chi.URLParam(r, "id"))
	if err != nil {
		http.Error(w, "bad id", http.StatusBadRequest)
		return
	}
	aid, err := uuid.Parse(chi.URLParam(r, "aid"))
	if err != nil {
		http.Error(w, "bad attachment id", http.StatusBadRequest)
		return
	}
	cmd, err := pool.Exec(r.Context(), `
		UPDATE posts SET download_count = download_count + 1, updated_at = NOW()
		WHERE id = $1 AND status = 'published' AND is_public = TRUE
			AND (published_at IS NULL OR published_at <= NOW())`, postID)
	if err != nil || cmd.RowsAffected() == 0 {
		http.NotFound(w, r)
		return
	}
	writeJSON(w, map[string]any{"ok": true})
	_ = aid
}

func listPostsQuery(w http.ResponseWriter, r *http.Request, searchMode bool) {
	pool := poolFrom(r)
	limit := postLimitDef(r, 20, 50)
	cursor := strings.TrimSpace(r.URL.Query().Get("cursor"))
	catSlug := strings.TrimSpace(r.URL.Query().Get("category"))
	typ := strings.TrimSpace(r.URL.Query().Get("type"))
	if typ == "" {
		typ = "all"
	}
	langFilter := strings.TrimSpace(r.URL.Query().Get("language"))

	base := postSelectBase() + ` WHERE ` + publicPostWhere
	args := []any{}
	cond := postTypeFilterSQL(typ, &args)
	cond += postLanguageFilterSQL(langFilter, &args)
	if catSlug != "" {
		args = append(args, catSlug)
		cond += fmt.Sprintf(` AND c.slug = $%d`, len(args))
	}
	if searchMode {
		q := strings.TrimSpace(r.URL.Query().Get("q"))
		if q != "" {
			pat := "%" + q + "%"
			args = append(args, pat)
			n := len(args)
			cond += fmt.Sprintf(` AND (
				p.text_zh ILIKE $%d OR p.text_en ILIKE $%d OR p.text_ja ILIKE $%d OR p.text_ko ILIKE $%d OR
				p.text_vi ILIKE $%d OR p.text_id ILIKE $%d OR p.text_ms ILIKE $%d OR
				EXISTS (SELECT 1 FROM post_attachments pa WHERE pa.post_id = p.id AND pa.filename ILIKE $%d) OR
				EXISTS (SELECT 1 FROM post_tags pt JOIN tags t ON t.id = pt.tag_id WHERE pt.post_id = p.id AND (
					t.name ILIKE $%d OR t.name_en ILIKE $%d OR t.name_ja ILIKE $%d OR t.name_ko ILIKE $%d OR
					t.name_vi ILIKE $%d OR t.name_id ILIKE $%d OR t.name_ms ILIKE $%d)))`,
				n, n, n, n, n, n, n, n, n, n, n, n, n, n, n)
		}
	}
	order := ` ORDER BY p.published_at DESC NULLS LAST, p.id DESC`
	if cursor != "" {
		pubT, cid, err := decodePostCursor(cursor)
		if err != nil {
			http.Error(w, "bad cursor", http.StatusBadRequest)
			return
		}
		args = append(args, pubT, cid)
		n := len(args)
		cond += fmt.Sprintf(` AND (p.published_at, p.id) < ($%d::timestamptz, $%d::uuid)`, n-1, n)
	}
	args = append(args, limit+1)
	limitArg := len(args)
	q := base + cond + order + fmt.Sprintf(` LIMIT $%d`, limitArg)

	rows, err := pool.Query(r.Context(), q, args...)
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
	items, err := collectPostRows(r, rows)
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
	var nextCursor string
	if len(items) > limit {
		last := items[limit]
		items = items[:limit]
		if t, err := time.Parse(time.RFC3339, last.PublishedAt); err == nil {
			uid, _ := uuid.Parse(last.ID)
			nextCursor = encodePostCursor(t, uid)
		}
	}
	writeJSON(w, PostListResponse{Items: items, NextCursor: nextCursor})
}

func collectPostRows(r *http.Request, rows pgx.Rows) ([]PostDTO, error) {
	defer rows.Close()
	var ids []uuid.UUID
	list := make([]PostDTO, 0)
	for rows.Next() {
		dto, _, err := scanPostRow(r, rows)
		if err != nil {
			return nil, err
		}
		uid, _ := uuid.Parse(dto.ID)
		ids = append(ids, uid)
		dto.Attachments = []AttachmentDTO{}
		dto.Tags = []string{}
		list = append(list, dto)
	}
	if err := rows.Err(); err != nil {
		return nil, err
	}
	atts, err := loadAttachmentsByPostIDs(r.Context(), poolFrom(r), ids)
	if err != nil {
		return nil, err
	}
	lang := requestLangCode(r)
	tagsByPost, err := loadPostTagNamesByPostIDs(r.Context(), poolFrom(r), ids, lang)
	if err != nil {
		return nil, err
	}
	for i := range list {
		uid, _ := uuid.Parse(list[i].ID)
		if a, ok := atts[uid]; ok {
			list[i].Attachments = a
		}
		if t, ok := tagsByPost[uid]; ok {
			list[i].Tags = t
		} else {
			list[i].Tags = []string{}
		}
	}
	return list, nil
}