| 1 | package calendar |
| 2 | |
| 3 | import ( |
| 4 | "context" |
| 5 | "crypto/rand" |
| 6 | "crypto/sha256" |
| 7 | "encoding/hex" |
| 8 | "errors" |
| 9 | "fmt" |
| 10 | "time" |
| 11 | |
| 12 | "gorm.io/gorm" |
| 13 | ) |
| 14 | |
| 15 | // FeedView is a feed with its poll counts, for the share page. |
| 16 | type FeedView struct { |
| 17 | Feed |
| 18 | CalendarName string |
| 19 | } |
| 20 | |
| 21 | // MintFeed creates a subscription capability and returns the token — |
| 22 | // once. |
| 23 | // |
| 24 | // Only the hash is stored. A plaintext token in this table would be a |
| 25 | // live, unauthenticated read capability for somebody's whole calendar, |
| 26 | // sitting in a file the platform replicates to object storage — which |
| 27 | // is exactly what the one rule exists to prevent. |
| 28 | // |
| 29 | // The consequence is that the URL cannot be shown again. The share page |
| 30 | // says so at the moment of minting, rather than letting somebody |
| 31 | // discover it by coming back for it. |
| 32 | func (s *Store) MintFeed(ctx context.Context, personID, calendarID int64) (string, error) { |
| 33 | if _, err := s.Calendar(ctx, personID, calendarID); err != nil { |
| 34 | return "", err |
| 35 | } |
| 36 | raw := make([]byte, 32) |
| 37 | if _, err := rand.Read(raw); err != nil { |
| 38 | return "", fmt.Errorf("calendar: no randomness for a feed token: %w", err) |
| 39 | } |
| 40 | token := hex.EncodeToString(raw) |
| 41 | |
| 42 | f := Feed{ |
| 43 | PersonID: personID, |
| 44 | CalendarID: calendarID, |
| 45 | TokenHash: HashFeedToken(token), |
| 46 | CreatedAt: time.Now().UTC(), |
| 47 | } |
| 48 | if err := s.g.WithContext(ctx).Create(&f).Error; err != nil { |
| 49 | return "", fmt.Errorf("calendar: mint feed: %w", err) |
| 50 | } |
| 51 | return token, nil |
| 52 | } |
| 53 | |
| 54 | // HashFeedToken is the stored form. SHA-256 with no salt, deliberately: |
| 55 | // the token is 32 bytes of entropy, so there is no dictionary to |
| 56 | // defend against, and an unsalted hash is what lets a lookup be a |
| 57 | // single indexed read rather than a scan of every row. |
| 58 | func HashFeedToken(token string) string { |
| 59 | sum := sha256.Sum256([]byte(token)) |
| 60 | return hex.EncodeToString(sum[:]) |
| 61 | } |
| 62 | |
| 63 | // FeedByToken resolves a subscription URL, and records the poll. |
| 64 | // |
| 65 | // The poll count is the honest part. A feed is not free: every poll |
| 66 | // wakes a hibernating instance, and Apple Calendar polls roughly every |
| 67 | // fifteen minutes forever. Recording it means the share page can show |
| 68 | // what a feed actually costs rather than implying it is free. |
| 69 | func (s *Store) FeedByToken(ctx context.Context, token string) (Feed, error) { |
| 70 | var f Feed |
| 71 | err := s.g.WithContext(ctx). |
| 72 | Where("token_hash = ? AND revoked_at IS NULL", HashFeedToken(token)). |
| 73 | First(&f).Error |
| 74 | if errors.Is(err, gorm.ErrRecordNotFound) { |
| 75 | return Feed{}, ErrNotFound |
| 76 | } |
| 77 | if err != nil { |
| 78 | return Feed{}, fmt.Errorf("calendar: read feed: %w", err) |
| 79 | } |
| 80 | now := time.Now().UTC() |
| 81 | // Best effort: a failed counter update must not fail the response. |
| 82 | // Somebody's calendar not loading is a real problem; a poll count |
| 83 | // being one short is not. |
| 84 | _ = s.g.WithContext(ctx).Model(&Feed{}).Where("id = ?", f.ID). |
| 85 | Updates(map[string]any{ |
| 86 | "last_polled_at": now, |
| 87 | "poll_count": gorm.Expr("poll_count + 1"), |
| 88 | }).Error |
| 89 | return f, nil |
| 90 | } |
| 91 | |
| 92 | // FeedsFor lists a person's own feeds on a calendar. |
| 93 | func (s *Store) FeedsFor(ctx context.Context, personID, calendarID int64) ([]Feed, error) { |
| 94 | var out []Feed |
| 95 | err := s.g.WithContext(ctx). |
| 96 | Where("person_id = ? AND calendar_id = ? AND revoked_at IS NULL", personID, calendarID). |
| 97 | Order("created_at DESC"). |
| 98 | Find(&out).Error |
| 99 | if err != nil { |
| 100 | return nil, fmt.Errorf("calendar: list feeds: %w", err) |
| 101 | } |
| 102 | return out, nil |
| 103 | } |
| 104 | |
| 105 | // RevokeFeed turns a subscription URL off. |
| 106 | // |
| 107 | // Revoked rather than deleted, so the share page can keep showing that |
| 108 | // it existed and how much it was polled — and so a URL that is still |
| 109 | // pasted into somebody's phone stops working rather than silently |
| 110 | // matching a later feed that happened to reuse the row. |
| 111 | func (s *Store) RevokeFeed(ctx context.Context, personID, feedID int64) error { |
| 112 | now := time.Now().UTC() |
| 113 | res := s.g.WithContext(ctx).Model(&Feed{}). |
| 114 | Where("id = ? AND person_id = ?", feedID, personID). |
| 115 | Update("revoked_at", now) |
| 116 | if res.Error != nil { |
| 117 | return fmt.Errorf("calendar: revoke feed: %w", res.Error) |
| 118 | } |
| 119 | if res.RowsAffected == 0 { |
| 120 | return ErrNotFound |
| 121 | } |
| 122 | return nil |
| 123 | } |
| 124 | |
| 125 | // EventsForFeed reads a calendar's events for export, opening the UID |
| 126 | // and attaching the feed owner's own reminder offsets. |
| 127 | func (s *Store) EventsForFeed(ctx context.Context, personID, calendarID, from, to int64) ([]EventView, error) { |
| 128 | all, err := s.feedEventRows(ctx, personID, calendarID, from, to) |
| 129 | if err != nil { |
| 130 | return nil, err |
| 131 | } |
| 132 | offsets, err := s.reminderOffsets(ctx, personID) |
| 133 | if err != nil { |
| 134 | return nil, err |
| 135 | } |
| 136 | out := make([]EventView, 0, len(all)) |
| 137 | for _, e := range all { |
| 138 | if e.CalendarID != calendarID { |
| 139 | continue |
| 140 | } |
| 141 | uid, err := s.openUID(e.Event) |
| 142 | if err != nil { |
| 143 | return nil, err |
| 144 | } |
| 145 | e.UIDSealedOpen = uid |
| 146 | e.ReminderOffsetMin = offsets[e.ID] |
| 147 | out = append(out, e) |
| 148 | } |
| 149 | return out, nil |
| 150 | } |
| 151 | |
| 152 | func (s *Store) openUID(e Event) (string, error) { |
| 153 | uid, err := s.seal.OpenString("event.uid", e.UIDSealed) |
| 154 | if err != nil { |
| 155 | return "", fmt.Errorf("calendar: open uid (event %d): %w", e.ID, err) |
| 156 | } |
| 157 | return uid, nil |
| 158 | } |
| 159 | |
| 160 | // reminderOffsets maps event id to the person's largest warning on it, |
| 161 | // for the alarms a feed can carry. |
| 162 | func (s *Store) reminderOffsets(ctx context.Context, personID int64) (map[int64]int, error) { |
| 163 | var rows []Reminder |
| 164 | if err := s.g.WithContext(ctx). |
| 165 | Where("person_id = ?", personID).Find(&rows).Error; err != nil { |
| 166 | return nil, fmt.Errorf("calendar: read reminder offsets: %w", err) |
| 167 | } |
| 168 | out := map[int64]int{} |
| 169 | for _, r := range rows { |
| 170 | if r.OffsetMin > out[r.EventID] { |
| 171 | out[r.EventID] = r.OffsetMin |
| 172 | } |
| 173 | } |
| 174 | return out, nil |
| 175 | } |
| 176 | |
| 177 | // SaveSettings updates a person's own display preferences. |
| 178 | func (s *Store) SaveSettings(ctx context.Context, personID int64, zone string, weekStart, reminderMin, allDayMin int) error { |
| 179 | if _, err := Zone(zone); err != nil { |
| 180 | return ValidationError{"zone", "That is not a time zone we know."} |
| 181 | } |
| 182 | switch weekStart { |
| 183 | case WeekStartMonday, WeekStartSaturday, WeekStartSunday: |
| 184 | default: |
| 185 | weekStart = WeekStartMonday |
| 186 | } |
| 187 | err := s.g.WithContext(ctx).Model(&Person{}).Where("id = ?", personID). |
| 188 | Updates(map[string]any{ |
| 189 | "zone": zone, |
| 190 | "week_start": weekStart, |
| 191 | "default_reminder_min": reminderMin, |
| 192 | "default_all_day_min": allDayMin, |
| 193 | "updated_at": time.Now().UTC(), |
| 194 | }).Error |
| 195 | if err != nil { |
| 196 | return fmt.Errorf("calendar: save settings: %w", err) |
| 197 | } |
| 198 | return nil |
| 199 | } |
| 200 | |
amadan