package api

import (
	"encoding/json"
	"fmt"
	"net/http"
	"strconv"
	"strings"
	"time"

	"github.com/ponzischeme89/memby/server/internal/notify"
	"github.com/ponzischeme89/memby/server/internal/sonarr"
	"github.com/ponzischeme89/memby/server/internal/store"
)

type myShowResponse struct {
	store.UserShow
	SonarrStatus string     `json:"sonarrStatus"`
	NextEpisode  *time.Time `json:"nextEpisode,omitempty"`
	Lifecycle    string     `json:"lifecycle"`
	Monitored    bool       `json:"monitored"`
}

type myShowsResponse struct {
	Shows []myShowResponse `json:"shows"`
}

type notificationsResponse struct {
	Notifications []store.UserNotification      `json:"notifications"`
	Preferences   store.NotificationPreferences `json:"preferences"`
}

func (s *Server) handleMyShows(w http.ResponseWriter, r *http.Request, sess store.Session) {
	switch r.Method {
	case http.MethodGet:
		s.listMyShows(w, r, sess)
	case http.MethodPost:
		var show store.UserShow
		if !decodeJSON(w, r, &show) {
			return
		}
		show.ItemID = strings.TrimSpace(show.ItemID)
		show.Title = strings.TrimSpace(show.Title)
		if show.ItemID == "" || show.Title == "" {
			writeError(w, http.StatusBadRequest, "itemId and title are required")
			return
		}
		if err := s.store.SaveUserShow(r.Context(), sess.EmbyUserID, show); err != nil {
			s.loggerFor(r.Context()).Error("save user show failed", "error", err)
			writeError(w, http.StatusInternalServerError, "could not save show")
			return
		}
		s.listMyShows(w, r, sess)
	default:
		w.WriteHeader(http.StatusMethodNotAllowed)
	}
}

func (s *Server) handleMyShow(w http.ResponseWriter, r *http.Request, sess store.Session) {
	itemID := strings.TrimSpace(r.PathValue("id"))
	if itemID == "" {
		writeError(w, http.StatusBadRequest, "show id is required")
		return
	}
	if err := s.store.DeleteUserShow(r.Context(), sess.EmbyUserID, itemID); err != nil {
		s.loggerFor(r.Context()).Error("delete user show failed", "error", err)
		writeError(w, http.StatusInternalServerError, "could not remove show")
		return
	}
	w.WriteHeader(http.StatusNoContent)
}

func (s *Server) listMyShows(w http.ResponseWriter, r *http.Request, sess store.Session) {
	saved, err := s.store.UserShows(r.Context(), sess.EmbyUserID)
	if err != nil {
		s.loggerFor(r.Context()).Error("list user shows failed", "error", err)
		writeError(w, http.StatusInternalServerError, "could not load shows")
		return
	}
	sonarrSeries := []sonarr.Series{}
	if s.sonarrEnabled(r.Context()) {
		if value, seriesErr := s.sonarrSeriesCatalogue(r.Context()); seriesErr == nil {
			sonarrSeries = value
		} else {
			s.loggerFor(r.Context()).Warn("Sonarr status unavailable for My Shows", "error", seriesErr)
		}
	}
	result := make([]myShowResponse, 0, len(saved))
	for _, show := range saved {
		matched := matchSonarrSeries(show, sonarrSeries)
		response := myShowResponse{
			UserShow:     show,
			SonarrStatus: "Not found",
			Lifecycle:    "Unknown",
		}
		if matched != nil {
			response.SonarrStatus = sonarrStatus(*matched)
			response.NextEpisode = matched.NextAiring
			response.Lifecycle = seriesLifecycle(matched.Status)
			response.Monitored = matched.Monitored
		}
		result = append(result, response)
	}
	writeJSON(w, http.StatusOK, myShowsResponse{Shows: result})
}

func matchSonarrSeries(show store.UserShow, all []sonarr.Series) *sonarr.Series {
	key := normalizedShowTitle(show.Title)
	for i := range all {
		candidate := &all[i]
		if normalizedShowTitle(candidate.Title) != key {
			continue
		}
		if show.Year == nil || candidate.Year == 0 || candidate.Year == *show.Year {
			return candidate
		}
	}
	return nil
}

func normalizedShowTitle(value string) string {
	return strings.Map(func(r rune) rune {
		if r >= 'A' && r <= 'Z' {
			return r + ('a' - 'A')
		}
		if (r >= 'a' && r <= 'z') || (r >= '0' && r <= '9') {
			return r
		}
		return -1
	}, value)
}

func seriesLifecycle(status string) string {
	switch strings.ToLower(status) {
	case "continuing", "upcoming":
		return "Continuing"
	case "ended", "deleted":
		return "Cancelled"
	default:
		if status == "" {
			return "Unknown"
		}
		return strings.ToUpper(status[:1]) + strings.ToLower(status[1:])
	}
}

func isContinuingSonarrStatus(status string) bool {
	return strings.EqualFold(status, "continuing") || strings.EqualFold(status, "upcoming")
}

func sonarrStatus(series sonarr.Series) string {
	if series.Monitored {
		return "Monitored"
	}
	return "Not monitored"
}

func (s *Server) handleNotifications(w http.ResponseWriter, r *http.Request, sess store.Session) {
	prefs, err := s.notificationPreferencesFor(r.Context(), sess.EmbyUserID)
	if err != nil {
		writeError(w, http.StatusInternalServerError, "could not load notification preferences")
		return
	}
	if r.Method == http.MethodPut {
		if !decodeJSON(w, r, &prefs) {
			return
		}
		if err := s.saveNotificationPreferences(r.Context(), sess.EmbyUserID, prefs); err != nil {
			writeError(w, http.StatusInternalServerError, "could not save notification preferences")
			return
		}
	}
	if prefs.Enabled && prefs.SonarrAlerts && prefs.ShowReturnAlerts {
		s.syncReturnNotifications(r, sess, prefs)
	}
	notifications, err := s.store.UserNotifications(r.Context(), sess.EmbyUserID)
	if err != nil {
		writeError(w, http.StatusInternalServerError, "could not load notifications")
		return
	}
	writeJSON(w, http.StatusOK, notificationsResponse{
		Notifications: filterStoredNotifications(notifications, prefs),
		Preferences:   prefs,
	})
}

func (s *Server) syncReturnNotifications(
	r *http.Request, sess store.Session, prefs store.NotificationPreferences,
) {
	if !s.sonarrEnabled(r.Context()) {
		return
	}
	shows, err := s.store.UserShows(r.Context(), sess.EmbyUserID)
	if err != nil {
		return
	}
	all, err := s.sonarrSeriesCatalogue(r.Context())
	if err != nil {
		return
	}
	now := time.Now()
	until := now.AddDate(0, 0, prefs.LeadDays)
	for _, show := range shows {
		series := matchSonarrSeries(show, all)
		if series == nil || series.NextAiring == nil ||
			series.NextAiring.Before(now) || series.NextAiring.After(until) {
			continue
		}
		days := int(series.NextAiring.Sub(now).Hours()/24) + 1
		message := fmt.Sprintf("%s returns in %d days.", show.Title, days)
		if days <= 1 {
			message = show.Title + " returns tomorrow."
		} else if days == 7 {
			message = show.Title + " returns next week."
		}
		sourceKey := "show-return:" + show.ItemID + ":" + series.NextAiring.UTC().Format("2006-01-02")
		s.notifyUser(r.Context(), notify.Notification{
			Kind:      "show-return",
			Source:    notifySourceShowReturn,
			UserID:    sess.EmbyUserID,
			Username:  sess.Username,
			Title:     "New episode coming",
			Body:      message,
			ItemID:    show.ItemID,
			SourceKey: sourceKey,
			EventAt:   series.NextAiring,
			Metadata:  map[string]any{"show": show.Title, "leadDays": prefs.LeadDays},
		})
	}
}

// clearNotificationsResponse says how many of this viewer's notifications the gateway
// actually cleared. The television prints the figure back as its confirmation, so it must be
// what happened rather than what was asked for.
type clearNotificationsResponse struct {
	Cleared int `json:"cleared"`
}

// handleClearNotifications empties one viewer's list in a single request.
//
// It exists because clearing from the user picker is a shortcut for somebody who does not
// want to go into the page at all, and a television looping the per-alert dismiss route
// could neither report a trustworthy count nor leave one line in the log an operator could
// read. The two rules worth preserving:
//
//   - What it clears is what that viewer can *see*. filterStoredNotifications is what the
//     list route already applies, so a summary their preferences have withdrawn is not
//     quietly dismissed underneath them by a press aimed at the seven alerts on screen —
//     and the count agrees with the badge that was showing.
//   - Nothing to clear is a success, not an error. It answers 0 and says so, because the
//     television disables the action on an empty list and a race with another set finishing
//     the job first is not a failure anybody should be shown.
//
// clearableNotificationIDs is the rows a clear-all press may take: exactly the ones the
// list route would have shown this viewer, and nothing their preferences have withdrawn.
//
// Pure and separate from the handler so the one rule that matters here — a press aimed at
// what is on screen never reaches past it — is pinned by a test rather than by a database.
func clearableNotificationIDs(
	notifications []store.UserNotification, prefs store.NotificationPreferences,
) []int64 {
	visible := filterStoredNotifications(notifications, prefs)
	ids := make([]int64, 0, len(visible))
	for _, notification := range visible {
		ids = append(ids, notification.ID)
	}
	return ids
}

func (s *Server) handleClearNotifications(
	w http.ResponseWriter, r *http.Request, sess store.Session,
) {
	log := s.loggerFor(r.Context())
	prefs, err := s.notificationPreferencesFor(r.Context(), sess.EmbyUserID)
	if err != nil {
		log.Warn("notifications not cleared", "reason", "preferences unavailable", "error", err)
		writeError(w, http.StatusInternalServerError, "could not load notification preferences")
		return
	}
	notifications, err := s.store.UserNotifications(r.Context(), sess.EmbyUserID)
	if err != nil {
		log.Warn("notifications not cleared", "reason", "list unavailable", "error", err)
		writeError(w, http.StatusInternalServerError, "could not load notifications")
		return
	}
	ids := clearableNotificationIDs(notifications, prefs)
	cleared, err := s.store.DismissNotifications(r.Context(), sess.EmbyUserID, ids)
	if err != nil {
		log.Warn("notifications not cleared", "reason", "write failed",
			"requested", len(ids), "error", err)
		writeError(w, http.StatusInternalServerError, "could not clear notifications")
		return
	}
	log.Info("notifications cleared", "cleared", cleared, "source", "user-switcher")
	writeJSON(w, http.StatusOK, clearNotificationsResponse{Cleared: cleared})
}

func (s *Server) handleNotificationAction(
	w http.ResponseWriter, r *http.Request, sess store.Session,
) {
	id, err := strconv.ParseInt(r.PathValue("id"), 10, 64)
	if err != nil || id < 1 {
		writeError(w, http.StatusBadRequest, "invalid notification id")
		return
	}
	switch r.PathValue("action") {
	case "read":
		err = s.store.MarkNotificationRead(r.Context(), sess.EmbyUserID, id)
	// Marking a notification back to new is the viewer's own action, where "read" is set by
	// the page merely focusing a row. That is why the two are separate routes rather than one
	// carrying a boolean: an automatic mark and a deliberate one are different events, and only
	// this one is ever a decision somebody made with the remote.
	case "unread":
		err = s.store.MarkNotificationUnread(r.Context(), sess.EmbyUserID, id)
	case "dismiss":
		err = s.store.DismissNotification(r.Context(), sess.EmbyUserID, id)
	default:
		writeError(w, http.StatusNotFound, "unknown notification action")
		return
	}
	if err != nil {
		writeError(w, http.StatusInternalServerError, "could not update notification")
		return
	}
	w.WriteHeader(http.StatusNoContent)
}

func decodeJSON(w http.ResponseWriter, r *http.Request, out any) bool {
	decoder := json.NewDecoder(http.MaxBytesReader(w, r.Body, 64<<10))
	decoder.DisallowUnknownFields()
	if err := decoder.Decode(out); err != nil {
		writeError(w, http.StatusBadRequest, "invalid request")
		return false
	}
	return true
}