package api

import (
	"context"
	"fmt"
	"strconv"
	"strings"
	"time"

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

// sonarrLifecycleResult is what one scan looked at and what moved.
//
// Counted rather than only logged because these are the figures the integrations console
// prints beside the run: "412 series checked, 3 changed" is an answer, where "the scan
// finished" is a line in a log an operator has to go and find.
type sonarrLifecycleResult struct {
	Series        int
	Changes       int
	Added         int
	Cancelled     int
	Notifications int
}

// scanSonarrLifecycle seeds the durable status history and records what changed since
// the last reading. History stores changes rather than identical daily snapshots: it still
// records the complete lifecycle while making an active-to-cancelled transition
// unambiguous.
func (s *Server) scanSonarrLifecycle(ctx context.Context) (sonarrLifecycleResult, error) {
	result := sonarrLifecycleResult{}
	series, err := s.sonarr.Series(ctx)
	if err != nil {
		return result, fmt.Errorf("read Sonarr series: %w", err)
	}
	now := time.Now().UTC()
	observations := make([]store.SonarrSeriesStatus, 0, len(series))
	for _, item := range series {
		key := sonarrSeriesStatusKey(item)
		if key == "" || strings.TrimSpace(item.Status) == "" {
			continue
		}
		observations = append(observations, store.SonarrSeriesStatus{
			SeriesKey: key, SonarrSeriesID: item.ID, TVDBID: item.TVDBID,
			Title: item.Title, Year: item.Year, Status: item.Status, ObservedAt: now,
		})
	}
	result.Series = len(observations)
	changes, err := s.store.RecordSonarrSeriesStatuses(ctx, observations)
	if err != nil {
		return result, err
	}
	result.Changes = len(changes)
	cancellations := make([]store.SonarrSeriesStatusChange, 0, len(changes))
	additions := make([]store.SonarrSeriesStatusChange, 0, len(changes))
	for _, change := range changes {
		switch sonarrLifecycleNotificationKind(change.PreviousStatus, change.Current.Status) {
		case "show-added":
			additions = append(additions, change)
		case "show-cancelled":
			cancellations = append(cancellations, change)
		}
	}
	result.Added, result.Cancelled = len(additions), len(cancellations)
	if len(cancellations) == 0 && len(additions) == 0 {
		s.log.Info("Sonarr lifecycle scan complete", "series", len(observations), "changes", len(changes))
		return result, nil
	}

	users, err := s.store.KnownUsers(ctx)
	if err != nil {
		return result, err
	}
	preferences := map[string]store.NotificationPreferences{}
	preferenceErrors := map[string]bool{}
	notifications := 0
	for _, change := range additions {
		for _, user := range users {
			prefs, ok := preferences[user.ID]
			if !ok && !preferenceErrors[user.ID] {
				prefs, err = s.store.NotificationPreferences(ctx, user.ID)
				if err != nil {
					preferenceErrors[user.ID] = true
					s.log.Warn("notification preferences unavailable during Sonarr lifecycle scan",
						"user", user.ID, "error", err)
					continue
				}
				preferences[user.ID] = prefs
			}
			eventAt := change.Current.ObservedAt
			sourceKey := fmt.Sprintf("show-added:%s:%d", change.Current.SeriesKey, change.HistoryID)
			notification := notify.Notification{
				Kind:      "show-added",
				Source:    notifySourceSonarrLifecycle,
				UserID:    user.ID,
				Username:  user.Username,
				Title:     "Show added",
				Body:      change.Current.Title + " was added to Sonarr.",
				SourceKey: sourceKey,
				EventAt:   &eventAt,
				Metadata:  map[string]any{"series": change.Current.Title, "status": change.Current.Status},
			}
			if preferenceErrors[user.ID] || !prefs.Enabled || !prefs.SonarrAlerts {
				s.declineUser(ctx, notification, sonarrDeclineReason(prefs, preferenceErrors[user.ID]))
				continue
			}
			if s.notifyUser(ctx, notification) {
				notifications++
			}
		}
	}
	for _, change := range cancellations {
		for _, user := range users {
			prefs, ok := preferences[user.ID]
			if !ok && !preferenceErrors[user.ID] {
				prefs, err = s.store.NotificationPreferences(ctx, user.ID)
				if err != nil {
					preferenceErrors[user.ID] = true
					s.log.Warn("notification preferences unavailable during Sonarr lifecycle scan",
						"user", user.ID, "error", err)
					continue
				}
				preferences[user.ID] = prefs
			}
			eventAt := change.Current.ObservedAt
			sourceKey := fmt.Sprintf("show-cancelled:%s:%d", change.Current.SeriesKey, change.HistoryID)
			notification := notify.Notification{
				Kind:      "show-cancelled",
				Source:    notifySourceSonarrLifecycle,
				UserID:    user.ID,
				Username:  user.Username,
				Title:     "Show cancelled",
				Body:      change.Current.Title + " has been cancelled.",
				SourceKey: sourceKey,
				EventAt:   &eventAt,
				Metadata:  map[string]any{"series": change.Current.Title, "status": change.Current.Status},
			}
			if preferenceErrors[user.ID] || !prefs.Enabled || !prefs.SonarrAlerts {
				s.declineUser(ctx, notification, sonarrDeclineReason(prefs, preferenceErrors[user.ID]))
				continue
			}
			if s.notifyUser(ctx, notification) {
				notifications++
			}
		}
	}
	result.Notifications = notifications
	s.log.Info("Sonarr lifecycle scan complete",
		"series", len(observations), "changes", len(changes),
		"added", len(additions), "cancelled", len(cancellations), "notifications", notifications)
	return result, nil
}

func sonarrLifecycleNotificationKind(previous, current string) string {
	if strings.TrimSpace(previous) == "" {
		return "show-added"
	}
	if sonarrBecameCancelled(previous, current) {
		return "show-cancelled"
	}
	return ""
}

func sonarrSeriesStatusKey(series sonarr.Series) string {
	if series.TVDBID > 0 {
		return "tvdb:" + strconv.Itoa(series.TVDBID)
	}
	if series.ID > 0 {
		return "sonarr:" + strconv.Itoa(series.ID)
	}
	return ""
}

func sonarrBecameCancelled(previous, current string) bool {
	previous = strings.ToLower(strings.TrimSpace(previous))
	current = strings.ToLower(strings.TrimSpace(current))
	active := previous == "continuing" || previous == "upcoming"
	cancelled := current == "ended" || current == "deleted" ||
		current == "cancelled" || current == "canceled"
	return active && cancelled
}

// sonarrDeclineReason is the sentence the console prints beside a skipped row.
//
// The three refusals are genuinely different answers to "why was I not told", and a page
// that collapsed them into "skipped" would send an operator to change a setting that was
// never the problem. A preference that would not load is its own case: it is read as "not
// now" rather than as consent, and that is a fact about the gateway rather than about the
// viewer.
func sonarrDeclineReason(prefs store.NotificationPreferences, unreadable bool) string {
	switch {
	case unreadable:
		return "this viewer's notification preferences could not be read"
	case !prefs.Enabled:
		return "this viewer has notifications switched off"
	default:
		return "this viewer has Sonarr alerts switched off"
	}
}