package handlers

import (
	"errors"
	"fmt"
	"net/http"
	"strconv"
	"strings"

	"github.com/go-chi/chi/v5"

	"task-dashboard/internal/models"
	"task-dashboard/internal/store"
)

// shoppingItemEditView is everything the edit sheet needs.
//
// Editable is the crux: only user-added items can be changed. PlanToEat items
// are scraped through a read-only client, so the sheet says so and offers
// removal rather than presenting fields that would silently not save.
type shoppingItemEditView struct {
	ID          string
	UserID      int64
	Name        string
	Store       string
	Section     string
	Source      string
	Editable    bool
	ReadOnlyWhy string
	Stores      []storeOptionView
}

type storeOptionView struct {
	Name     string
	Selected bool
	Sections []sectionOptionView
}

type sectionOptionView struct {
	Name     string
	Selected bool
}

// parseUserItemID pulls the numeric id out of a "user-123" composite id.
func parseUserItemID(id string) (int64, bool) {
	if !strings.HasPrefix(id, "user-") {
		return 0, false
	}
	n, err := strconv.ParseInt(strings.TrimPrefix(id, "user-"), 10, 64)
	if err != nil {
		return 0, false
	}
	return n, true
}

// HandleShoppingItemEdit renders the edit sheet for one item.
func (h *Handler) HandleShoppingItemEdit(w http.ResponseWriter, r *http.Request) {
	itemID := chi.URLParam(r, "id")
	source := r.URL.Query().Get("source")

	view := shoppingItemEditView{ID: itemID, Source: source}

	if userID, ok := parseUserItemID(itemID); ok {
		item, err := h.store.GetUserShoppingItem(userID)
		if err != nil {
			if errors.Is(err, store.ErrItemNotFound) {
				JSONError(w, http.StatusNotFound, "Item not found", err)
				return
			}
			JSONError(w, http.StatusInternalServerError, "Failed to load item", err)
			return
		}
		view.UserID = userID
		view.Name = item.Name
		view.Store = item.Store
		view.Section = item.Section
		view.Source = "user"
		view.Editable = true
	} else {
		// Everything else comes from PlanToEat, whose client is read-only.
		view.Name = r.URL.Query().Get("name")
		view.Store = r.URL.Query().Get("store")
		view.Editable = false
		view.ReadOnlyWhy = "This item is synced from PlanToEat. Edit it there, or remove it from this list."
	}

	view.Stores = h.storeOptions(view.Store, view.Section)

	HTMLResponse(w, h.renderer, "shopping-item-edit", view)
}

// storeOptions builds the store/section picker, marking the current selection.
func (h *Handler) storeOptions(currentStore, currentSection string) []storeOptionView {
	stores, err := h.store.GetShoppingStores()
	if err != nil {
		return nil
	}

	seen := map[string]bool{}
	out := make([]storeOptionView, 0, len(stores))
	for _, st := range stores {
		seen[st.Name] = true
		opt := storeOptionView{Name: st.Name, Selected: st.Name == currentStore}
		for _, sec := range st.Sections {
			opt.Sections = append(opt.Sections, sectionOptionView{
				Name:     sec.Name,
				Selected: st.Name == currentStore && sec.Name == currentSection,
			})
		}
		out = append(out, opt)
	}

	// An item can sit in a store that predates the registry (imported, or
	// named by PlanToEat). Offer it so the current value is selectable rather
	// than silently reset on save.
	if currentStore != "" && !seen[currentStore] {
		out = append(out, storeOptionView{Name: currentStore, Selected: true})
	}
	return out
}

// HandleShoppingItemUpdate saves an edit.
func (h *Handler) HandleShoppingItemUpdate(w http.ResponseWriter, r *http.Request) {
	itemID := chi.URLParam(r, "id")
	userID, ok := parseUserItemID(itemID)
	if !ok {
		JSONError(w, http.StatusBadRequest, "Only your own items can be edited", nil)
		return
	}
	if err := r.ParseForm(); err != nil {
		JSONError(w, http.StatusBadRequest, "Failed to parse form", err)
		return
	}

	name := r.FormValue("name")
	storeName := r.FormValue("store")
	section := r.FormValue("section")

	if err := h.store.UpdateUserShoppingItem(userID, name, storeName, section); err != nil {
		switch {
		case errors.Is(err, store.ErrItemNotFound):
			JSONError(w, http.StatusNotFound, "Item not found", err)
		default:
			JSONError(w, http.StatusBadRequest, err.Error(), err)
		}
		return
	}

	h.respondWithShoppingList(w, r)
}

// HandleShoppingItemDelete removes an item.
//
// A user item is deleted outright. A PlanToEat item cannot be deleted at
// source, so it is marked checked, which filters it out of the list — the same
// mechanism shopping mode already uses to complete one.
func (h *Handler) HandleShoppingItemDelete(w http.ResponseWriter, r *http.Request) {
	itemID := chi.URLParam(r, "id")

	if userID, ok := parseUserItemID(itemID); ok {
		if err := h.store.DeleteUserShoppingItem(userID); err != nil {
			JSONError(w, http.StatusInternalServerError, "Failed to delete item", err)
			return
		}
	} else {
		source := r.URL.Query().Get("source")
		if source == "" {
			source = "plantoeat"
		}
		if err := h.store.SetShoppingItemChecked(source, itemID, true); err != nil {
			JSONError(w, http.StatusInternalServerError, "Failed to remove item", err)
			return
		}
	}

	h.respondWithShoppingList(w, r)
}

// HandleShoppingStoreCreate registers a new store.
func (h *Handler) HandleShoppingStoreCreate(w http.ResponseWriter, r *http.Request) {
	if err := r.ParseForm(); err != nil {
		JSONError(w, http.StatusBadRequest, "Failed to parse form", err)
		return
	}
	if err := h.store.AddShoppingStore(r.FormValue("name")); err != nil {
		JSONError(w, http.StatusBadRequest, err.Error(), err)
		return
	}
	h.respondWithShoppingList(w, r)
}

// HandleShoppingSectionCreate adds a section to a store, addressed by name so
// the caller does not need to know the store's id.
func (h *Handler) HandleShoppingSectionCreate(w http.ResponseWriter, r *http.Request) {
	if err := r.ParseForm(); err != nil {
		JSONError(w, http.StatusBadRequest, "Failed to parse form", err)
		return
	}
	storeName := strings.TrimSpace(r.FormValue("store"))
	sectionName := strings.TrimSpace(r.FormValue("name"))

	stores, err := h.store.GetShoppingStores()
	if err != nil {
		JSONError(w, http.StatusInternalServerError, "Failed to load stores", err)
		return
	}
	for _, st := range stores {
		if strings.EqualFold(st.Name, storeName) {
			if err := h.store.AddShoppingSection(st.ID, sectionName); err != nil {
				JSONError(w, http.StatusBadRequest, err.Error(), err)
				return
			}
			h.respondWithShoppingList(w, r)
			return
		}
	}
	JSONError(w, http.StatusNotFound, fmt.Sprintf("No store named %q", storeName), nil)
}

// respondWithShoppingList re-renders the items list, which is what every edit
// action swaps into the page.
func (h *Handler) respondWithShoppingList(w http.ResponseWriter, r *http.Request) {
	allStores := h.aggregateShoppingLists(r.Context())
	grouped := r.FormValue("grouped") != "false"
	if v := r.URL.Query().Get("grouped"); v != "" {
		grouped = v != "false"
	}
	HTMLResponse(w, h.renderer, "shopping-items-content", struct {
		Stores  []models.ShoppingStore
		Grouped bool
	}{allStores, grouped})
}