package handlers

import (
	"encoding/json"
	"errors"
	"net/http"
	"strings"
	"time"

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

// WidgetAuthMiddleware validates the static bearer token for widget API endpoints.
func WidgetAuthMiddleware(token string, next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if token == "" {
			http.Error(w, "unauthorized", http.StatusUnauthorized)
			return
		}
		auth := r.Header.Get("Authorization")
		if !strings.HasPrefix(auth, "Bearer ") || strings.TrimPrefix(auth, "Bearer ") != token {
			http.Error(w, "unauthorized", http.StatusUnauthorized)
			return
		}
		next.ServeHTTP(w, r)
	})
}

// TimelineItemToWidgetItem converts a TimelineItem to a WidgetItem for the widget API.
// Exported for testability.
func TimelineItemToWidgetItem(item models.TimelineItem) models.WidgetItem {
	wi := models.WidgetItem{
		ID:               item.ID,
		Title:            item.Title,
		Source:           item.Source,
		IsAllDay:         item.IsAllDay,
		IsOverdue:        item.IsOverdue,
		URL:              item.URL,
		RecurringEventID: item.RecurringEventID,
	}

	switch item.Type {
	case models.TimelineItemTypeEvent:
		wi.Type = "event"
	case models.TimelineItemTypeMeal:
		wi.Type = "event"
	case models.TimelineItemTypeCard, models.TimelineItemTypeGTask:
		wi.Type = "task"
		// not completable via widget API
	default:
		wi.Type = "task"
		wi.Completable = item.Source == "doot"
	}

	// Only populate Start/End for items with a real time. All-day CALENDAR
	// EVENTS (not undated doot/gtask tasks, which are also flagged IsAllDay
	// as a "no specific time" fallback -- see TimelineItem.ComputeDaySection)
	// get Start populated too, using their real event date, so the widget
	// client can pin them to the top of the correct day's section instead of
	// losing them in the floating-task hourly-slot packer, which has no
	// concept of "all day" and can push a slot past the visible grid range
	// entirely. Tasks keep the existing nil-Start "floating" treatment
	// regardless of IsAllDay -- only Start is set for them (never End), and
	// only when they have a real time.
	if !item.Time.IsZero() && (!item.IsAllDay || item.Type == models.TimelineItemTypeEvent) {
		t := item.Time
		wi.Start = &t
		if !item.IsAllDay {
			if item.EndTime != nil {
				wi.End = item.EndTime
			} else {
				end := item.Time.Add(time.Hour)
				wi.End = &end
			}
		}
	}

	// DueDate is independent of Start/IsAllDay -- doot tasks deliberately
	// keep Start nil (see the "floating task" doc comment above) so the
	// client's SlotPacker positions them, but the Android detail popup
	// still needs to know the real due date to display and reschedule it.
	if item.Type == models.TimelineItemTypeTask && item.Source == "doot" && !item.Time.IsZero() {
		due := item.Time
		wi.DueDate = &due
	}

	return wi
}

// HandleWidgetGet returns today's timeline items as JSON for the Android widget.
func (h *Handler) HandleWidgetGet(w http.ResponseWriter, r *http.Request) {
	now := config.Now()
	tz := config.GetDisplayTimezone()
	start := time.Date(now.Year(), now.Month(), now.Day(), 0, 0, 0, 0, tz)
	end := start.Add(48 * time.Hour)

	items, err := BuildTimeline(r.Context(), h.store, start, end)
	if err != nil {
		http.Error(w, "internal error", http.StatusInternalServerError)
		return
	}

	widgetItems := make([]models.WidgetItem, 0, len(items))
	for _, item := range items {
		if item.DaySection == models.DaySectionToday ||
			item.DaySection == models.DaySectionTomorrow ||
			item.IsOverdue {
			widgetItems = append(widgetItems, TimelineItemToWidgetItem(item))
		}
	}

	resp := models.WidgetResponse{
		Now:   now,
		Items: widgetItems,
	}

	w.Header().Set("Content-Type", "application/json")
	_ = json.NewEncoder(w).Encode(resp)
}

type widgetCompleteRequest struct {
	ID     string `json:"id"`
	Source string `json:"source"`
}

type widgetAddRequest struct {
	Title string `json:"title"`
}

type widgetRescheduleRequest struct {
	ID     string `json:"id"`
	Source string `json:"source"`
	Date   string `json:"date"` // YYYY-MM-DD
}

// HandleWidgetReschedule updates the due date of a native task.
func (h *Handler) HandleWidgetReschedule(w http.ResponseWriter, r *http.Request) {
	var req widgetRescheduleRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		http.Error(w, "bad request", http.StatusBadRequest)
		return
	}
	if req.Source != "doot" {
		http.Error(w, "only doot tasks can be rescheduled via widget", http.StatusBadRequest)
		return
	}
	parsed, err := time.Parse("2006-01-02", req.Date)
	if err != nil {
		http.Error(w, "invalid date", http.StatusBadRequest)
		return
	}
	tz := config.GetDisplayTimezone()
	dueDate := time.Date(parsed.Year(), parsed.Month(), parsed.Day(), 0, 0, 0, 0, tz)
	if err := h.store.RescheduleNativeTask(req.ID, dueDate); err != nil {
		if errors.Is(err, store.ErrNativeTaskNotFound) {
			http.Error(w, "task not found", http.StatusNotFound)
			return
		}
		http.Error(w, "failed to reschedule", http.StatusInternalServerError)
		return
	}
	w.WriteHeader(http.StatusOK)
}

// HandleWidgetComplete proxies a task completion to the source API or native store.
func (h *Handler) HandleWidgetComplete(w http.ResponseWriter, r *http.Request) {
	var req widgetCompleteRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		http.Error(w, "bad request", http.StatusBadRequest)
		return
	}

	switch req.Source {
	case "doot":
		if err := h.store.CompleteNativeTask(req.ID); err != nil {
			if errors.Is(err, store.ErrNativeTaskNotFound) {
				// Surfaced as 404 (not a silent 200) so the caller -- the
				// Android widget -- can tell "nothing changed" apart from
				// "it worked", instead of the previous behavior where a
				// stale/wrong id looked identical to a real completion.
				http.Error(w, "task not found", http.StatusNotFound)
				return
			}
			http.Error(w, "failed to complete task", http.StatusInternalServerError)
			return
		}
		_ = h.store.SaveCompletedTask("doot", req.ID, "", nil)
	default:
		http.Error(w, "source not completable", http.StatusBadRequest)
		return
	}

	w.WriteHeader(http.StatusOK)
}

// HandleWidgetRecurrence looks up and formats a recurring calendar event's schedule.
func (h *Handler) HandleWidgetRecurrence(w http.ResponseWriter, r *http.Request) {
	recurringEventID := r.URL.Query().Get("recurring_event_id")
	if recurringEventID == "" {
		http.Error(w, "recurring_event_id is required", http.StatusBadRequest)
		return
	}

	recurrence, err := h.googleCalendarClient.GetRecurrenceRule(r.Context(), recurringEventID)
	if err != nil {
		http.Error(w, "recurring event not found", http.StatusNotFound)
		return
	}

	resp := struct {
		Recurrence string `json:"recurrence"`
	}{Recurrence: recurrence}

	w.Header().Set("Content-Type", "application/json")
	_ = json.NewEncoder(w).Encode(resp)
}

// HandleWidgetAdd creates a new undated native task from the widget's quick-add sheet.
func (h *Handler) HandleWidgetAdd(w http.ResponseWriter, r *http.Request) {
	var req widgetAddRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		http.Error(w, "bad request", http.StatusBadRequest)
		return
	}

	title := strings.TrimSpace(req.Title)
	if title == "" {
		http.Error(w, "title is required", http.StatusBadRequest)
		return
	}

	task := models.Task{
		ID:       newID(),
		Content:  title,
		Priority: 1,
	}
	if err := h.store.CreateNativeTask(task); err != nil {
		http.Error(w, "failed to create task", http.StatusInternalServerError)
		return
	}

	w.WriteHeader(http.StatusOK)
}