package handler

import (
	"encoding/json"
	"net/http"

	"github.com/go-chi/chi/v5"
	"github.com/prabhupadasays/spsays-bff/internal/middleware"
	"github.com/prabhupadasays/spsays-bff/internal/service"
	"github.com/prabhupadasays/spsays-bff/pkg/response"
)

// CommentHandler serves the post-comment endpoints: listing top-level comments
// + a thread's replies (public), and create / like / pin / delete / report
// (auth-required).
type CommentHandler struct {
	svc *service.CommentService
}

func NewCommentHandler(svc *service.CommentService) *CommentHandler {
	return &CommentHandler{svc: svc}
}

type createCommentReq struct {
	Body string `json:"body"`
	// ParentID nil → top-level comment; otherwise the comment being replied
	// to (the service flattens replies onto the thread root).
	ParentID *string `json:"parent_id"`
}

type commentLikeResp struct {
	LikesCount int `json:"likes_count"`
}

// List — GET /posts/{id}/comments?limit=&offset=. Top-level comments, pinned
// first then newest. Public (OptionalAuth populates viewer_has_liked).
func (h *CommentHandler) List(w http.ResponseWriter, r *http.Request) {
	postID := chi.URLParam(r, "id")
	viewerID := middleware.UserID(r.Context())
	limit, offset := parseLimitOffset(r)
	items, total, err := h.svc.List(r.Context(), postID, viewerID, limit, offset)
	if err != nil {
		mapSocialErr(w, err)
		return
	}
	response.JSONWithMeta(w, http.StatusOK, items, paginationMeta(total, limit, offset))
}

// Replies — GET /comments/{id}/replies?limit=&offset=. A thread's replies,
// oldest first. Public (OptionalAuth).
func (h *CommentHandler) Replies(w http.ResponseWriter, r *http.Request) {
	commentID := chi.URLParam(r, "id")
	viewerID := middleware.UserID(r.Context())
	limit, offset := parseLimitOffset(r)
	items, total, err := h.svc.Replies(r.Context(), commentID, viewerID, limit, offset)
	if err != nil {
		mapSocialErr(w, err)
		return
	}
	response.JSONWithMeta(w, http.StatusOK, items, paginationMeta(total, limit, offset))
}

// Create — POST /posts/{id}/comments. Body: {body, parent_id?}. RequireAuth.
func (h *CommentHandler) Create(w http.ResponseWriter, r *http.Request) {
	uid := middleware.UserID(r.Context())
	postID := chi.URLParam(r, "id")
	var req createCommentReq
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		response.Error(w, http.StatusBadRequest, "invalid request body")
		return
	}
	// Treat an empty parent_id as a top-level comment, not a (missing) reply.
	if req.ParentID != nil && *req.ParentID == "" {
		req.ParentID = nil
	}
	c, err := h.svc.Add(r.Context(), uid, postID, req.ParentID, req.Body)
	if err != nil {
		mapSocialErr(w, err)
		return
	}
	response.JSON(w, http.StatusCreated, c)
}

// Like — POST /comments/{id}/like. Idempotent. RequireAuth.
func (h *CommentHandler) Like(w http.ResponseWriter, r *http.Request) {
	uid := middleware.UserID(r.Context())
	id := chi.URLParam(r, "id")
	count, err := h.svc.Like(r.Context(), uid, id)
	if err != nil {
		mapSocialErr(w, err)
		return
	}
	response.JSON(w, http.StatusOK, commentLikeResp{LikesCount: count})
}

// Unlike — DELETE /comments/{id}/like. Idempotent. RequireAuth.
func (h *CommentHandler) Unlike(w http.ResponseWriter, r *http.Request) {
	uid := middleware.UserID(r.Context())
	id := chi.URLParam(r, "id")
	count, err := h.svc.Unlike(r.Context(), uid, id)
	if err != nil {
		mapSocialErr(w, err)
		return
	}
	response.JSON(w, http.StatusOK, commentLikeResp{LikesCount: count})
}

// Pin — POST /comments/{id}/pin. Post author only; top-level only. RequireAuth.
func (h *CommentHandler) Pin(w http.ResponseWriter, r *http.Request) {
	uid := middleware.UserID(r.Context())
	id := chi.URLParam(r, "id")
	if err := h.svc.Pin(r.Context(), uid, id); err != nil {
		mapSocialErr(w, err)
		return
	}
	response.NoContent(w)
}

// Unpin — DELETE /comments/{id}/pin. Post author only. RequireAuth.
func (h *CommentHandler) Unpin(w http.ResponseWriter, r *http.Request) {
	uid := middleware.UserID(r.Context())
	id := chi.URLParam(r, "id")
	if err := h.svc.Unpin(r.Context(), uid, id); err != nil {
		mapSocialErr(w, err)
		return
	}
	response.NoContent(w)
}

// Delete — DELETE /comments/{id}. Comment author or post author. RequireAuth.
// For a thread root this removes the whole thread.
func (h *CommentHandler) Delete(w http.ResponseWriter, r *http.Request) {
	uid := middleware.UserID(r.Context())
	id := chi.URLParam(r, "id")
	if err := h.svc.Delete(r.Context(), uid, id); err != nil {
		mapSocialErr(w, err)
		return
	}
	response.NoContent(w)
}

// Report — POST /comments/{id}/report. Body: {category, reason?}. RequireAuth.
func (h *CommentHandler) Report(w http.ResponseWriter, r *http.Request) {
	uid := middleware.UserID(r.Context())
	id := chi.URLParam(r, "id")
	var req reportPostReq
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		response.Error(w, http.StatusBadRequest, "invalid request body")
		return
	}
	if err := h.svc.Report(r.Context(), uid, id, req.Category, req.Reason); err != nil {
		mapSocialErr(w, err)
		return
	}
	response.NoContent(w)
}