package httpapi

import (
	"log/slog"
	"net/http"
	"strings"

	"github.com/google/uuid"

	"github.com/mitbringsl/backend/internal/store"
)

// ListHandler handles the /api/lists endpoints.
type ListHandler struct {
	lists *store.ListStore
	items *store.ItemStore
}

// NewListHandler creates a ListHandler with the given stores.
func NewListHandler(lists *store.ListStore, items *store.ItemStore) *ListHandler {
	return &ListHandler{lists: lists, items: items}
}

// --- request / response types -----------------------------------------------

type createListRequest struct {
	Name string `json:"name"`
}

type listDTO struct {
	ID        string `json:"id"`
	Name      string `json:"name"`
	UpdatedAt string `json:"updated_at"`
	HLCTS     int64  `json:"hlc_ts"`
}

type listDetailDTO struct {
	listDTO
	Items []store.Item `json:"items"`
}

type listListResponse struct {
	Lists []listDTO `json:"lists"`
}

// --- handlers ---------------------------------------------------------------

// List returns all non-deleted lists for the authenticated user.
// GET /api/lists
func (h *ListHandler) List(w http.ResponseWriter, r *http.Request) {
	userID, ok := userIDFromCtx(r)
	if !ok {
		renderError(w, http.StatusUnauthorized, "Unauthorized", "Missing user context.")
		return
	}

	ls, err := h.lists.GetLists(r.Context(), userID)
	if err != nil {
		slog.Error("list lists failed", "error", err, "user_id", userID)
		renderError(w, http.StatusInternalServerError, "Internal error", "Could not load lists.")
		return
	}

	dtos := make([]listDTO, len(ls))
	for i, l := range ls {
		dtos[i] = listDTO{
			ID:        l.ID.String(),
			Name:      l.Name,
			UpdatedAt: l.UpdatedAt.Format("2006-01-02T15:04:05Z07:00"),
			HLCTS:     l.HLCTS,
		}
	}
	renderJSON(w, http.StatusOK, listListResponse{Lists: dtos})
}

// Create creates a new list for the authenticated user.
// POST /api/lists
func (h *ListHandler) Create(w http.ResponseWriter, r *http.Request) {
	userID, ok := userIDFromCtx(r)
	if !ok {
		renderError(w, http.StatusUnauthorized, "Unauthorized", "Missing user context.")
		return
	}

	var req createListRequest
	if !decodeJSON(w, r, &req) {
		return
	}
	name := strings.TrimSpace(req.Name)
	if name == "" {
		renderError(w, http.StatusBadRequest, "Bad request", "List name must not be empty.")
		return
	}

	l, err := h.lists.CreateList(r.Context(), userID, name)
	if err != nil {
		slog.Error("create list failed", "error", err, "user_id", userID)
		renderError(w, http.StatusInternalServerError, "Internal error", "Could not create list.")
		return
	}
	renderJSON(w, http.StatusCreated, listDTO{
		ID:        l.ID.String(),
		Name:      l.Name,
		UpdatedAt: l.UpdatedAt.Format("2006-01-02T15:04:05Z07:00"),
		HLCTS:     l.HLCTS,
	})
}

// Get returns a single list with its items.
// GET /api/lists/{id}
func (h *ListHandler) Get(w http.ResponseWriter, r *http.Request) {
	userID, ok := userIDFromCtx(r)
	if !ok {
		renderError(w, http.StatusUnauthorized, "Unauthorized", "Missing user context.")
		return
	}

	listID, err := uuid.Parse(r.PathValue("id"))
	if err != nil {
		renderError(w, http.StatusBadRequest, "Bad request", "Invalid list ID.")
		return
	}

	l, err := h.lists.GetList(r.Context(), listID, userID)
	if err != nil {
		if !apiError(w, err) {
			slog.Error("get list failed", "error", err, "list_id", listID)
			renderError(w, http.StatusInternalServerError, "Internal error", "Could not load list.")
		}
		return
	}

	its, err := h.items.GetItems(r.Context(), listID)
	if err != nil {
		slog.Error("get items failed", "error", err, "list_id", listID)
		renderError(w, http.StatusInternalServerError, "Internal error", "Could not load items.")
		return
	}
	if its == nil {
		its = []store.Item{}
	}

	renderJSON(w, http.StatusOK, listDetailDTO{
		listDTO: listDTO{
			ID:        l.ID.String(),
			Name:      l.Name,
			UpdatedAt: l.UpdatedAt.Format("2006-01-02T15:04:05Z07:00"),
			HLCTS:     l.HLCTS,
		},
		Items: its,
	})
}

// userIDFromCtx extracts the user UUID from the request context (set by RequireAuth).
func userIDFromCtx(r *http.Request) (uuid.UUID, bool) {
	v := r.Context().Value(ctxKeyUserID)
	if v == nil {
		return uuid.Nil, false
	}
	id, ok := v.(uuid.UUID)
	return id, ok
}