| 1 | package agent |
| 2 | |
| 3 | import ( |
| 4 | "context" |
| 5 | "fmt" |
| 6 | "slices" |
| 7 | "time" |
| 8 | |
| 9 | "reasonix/internal/store" |
| 10 | ) |
| 11 | |
| 12 | // sessionHeadState is what a Session knows about its schema-2 log position; |
| 13 | // it stays zero for schema-1 sessions. state caches the replayed graph so a |
| 14 | // save only reads the bytes appended since the last observed tail. |
| 15 | type sessionHeadState struct { |
| 16 | ref HeadRef |
| 17 | dag bool |
| 18 | headCount int |
| 19 | state *sessionDAGState |
| 20 | events []HeadEvent |
| 21 | pending []sessionDAGEntry |
| 22 | openTurn *sessionDAGTurn |
| 23 | } |
| 24 | |
| 25 | // clone retains execution identity without sharing the mutable replay cache. |
| 26 | // Pending entries are turn markers containing only scalar fields. |
| 27 | func (h sessionHeadState) clone() sessionHeadState { |
| 28 | h.state = nil |
| 29 | h.events = slices.Clone(h.events) |
| 30 | h.pending = slices.Clone(h.pending) |
| 31 | if h.openTurn != nil { |
| 32 | turn := *h.openTurn |
| 33 | h.openTurn = &turn |
| 34 | } |
| 35 | return h |
| 36 | } |
| 37 | |
| 38 | // HeadEvent reports a head-level fact a save discovered; the controller turns |
| 39 | // it into a user-facing notice. |
| 40 | type HeadEvent struct { |
| 41 | Kind string |
| 42 | HeadID string |
| 43 | OtherWriter string |
| 44 | } |
| 45 | |
| 46 | const ( |
| 47 | // HeadEventForkedConcurrent: this writer's head diverged from another |
| 48 | // writer's appends and continued on a fresh head. |
| 49 | HeadEventForkedConcurrent = "forked_concurrent" |
| 50 | // HeadEventMultipleRecentHeads: the session opened on one of several heads |
| 51 | // that were active within recentHeadWindow; the others remain versions. |
| 52 | HeadEventMultipleRecentHeads = "multiple_recent_heads" |
| 53 | ) |
| 54 | |
| 55 | // recentHeadWindow bounds how old a competing head may be before opening a |
| 56 | // conversation stops mentioning it. |
| 57 | const recentHeadWindow = 24 * time.Hour |
| 58 | |
| 59 | // loadHeadEvents derives the events a fresh load should surface. |
| 60 | func loadHeadEvents(st *sessionDAGState, selected string) []HeadEvent { |
| 61 | if st == nil { |
| 62 | return nil |
| 63 | } |
| 64 | h := st.heads[selected] |
| 65 | if h == nil { |
| 66 | return nil |
| 67 | } |
| 68 | for _, id := range st.liveHeads() { |
| 69 | if id == selected { |
| 70 | continue |
| 71 | } |
| 72 | if other := st.heads[id]; other != nil && h.lastActivity.Sub(other.lastActivity) < recentHeadWindow { |
| 73 | return []HeadEvent{{Kind: HeadEventMultipleRecentHeads, HeadID: selected, OtherWriter: other.writer}} |
| 74 | } |
| 75 | } |
| 76 | return nil |
| 77 | } |
| 78 | |
| 79 | // Head reports the head this session was loaded from or last saved to. ok is |
| 80 | // false for sessions that still live in a schema-1 log or a bare .jsonl. |
| 81 | func (s *Session) Head() (HeadRef, bool) { |
| 82 | if s == nil { |
| 83 | return HeadRef{}, false |
| 84 | } |
| 85 | s.mu.RLock() |
| 86 | defer s.mu.RUnlock() |
| 87 | return s.head.ref, s.head.dag |
| 88 | } |
| 89 | |
| 90 | // DrainHeadEvents returns and clears the head events recorded by saves. |
| 91 | func (s *Session) DrainHeadEvents() []HeadEvent { |
| 92 | if s == nil { |
| 93 | return nil |
| 94 | } |
| 95 | s.mu.Lock() |
| 96 | defer s.mu.Unlock() |
| 97 | events := s.head.events |
| 98 | s.head.events = nil |
| 99 | return events |
| 100 | } |
| 101 | |
| 102 | // selectedHead picks the head a plain open lands on: the last explicit select |
| 103 | // while that head is alive, otherwise the most recently active live head, with |
| 104 | // the larger log offset breaking ties so every reader of the same bytes agrees. |
| 105 | func (st *sessionDAGState) selectedHead() string { |
| 106 | if h := st.heads[st.selected]; h != nil && !h.retired { |
| 107 | return h.id |
| 108 | } |
| 109 | pick := func(includeRetired bool) string { |
| 110 | best := "" |
| 111 | for _, id := range st.headOrder { |
| 112 | h := st.heads[id] |
| 113 | if h == nil || (h.retired && !includeRetired) { |
| 114 | continue |
| 115 | } |
| 116 | if best == "" { |
| 117 | best = id |
| 118 | continue |
| 119 | } |
| 120 | b := st.heads[best] |
| 121 | if h.lastActivity.After(b.lastActivity) || (h.lastActivity.Equal(b.lastActivity) && h.lastOffset > b.lastOffset) { |
| 122 | best = id |
| 123 | } |
| 124 | } |
| 125 | return best |
| 126 | } |
| 127 | if best := pick(false); best != "" { |
| 128 | return best |
| 129 | } |
| 130 | if best := pick(true); best != "" { |
| 131 | return best |
| 132 | } |
| 133 | return SessionMainHead |
| 134 | } |
| 135 | |
| 136 | func (st *sessionDAGState) headRecord(id string, selected string) SessionHead { |
| 137 | h := st.heads[id] |
| 138 | msgs, _ := st.materialize(id) |
| 139 | preview, turns := SessionPreviewFromMessages(msgs) |
| 140 | return SessionHead{ |
| 141 | ID: h.id, |
| 142 | Kind: h.kind, |
| 143 | Name: h.name, |
| 144 | ParentHead: h.parentHead, |
| 145 | ForkFrom: h.forkFrom, |
| 146 | Writer: h.writer, |
| 147 | LeafID: h.leaf, |
| 148 | CreatedAt: h.createdAt, |
| 149 | LastActivity: h.lastActivity, |
| 150 | Retired: h.retired, |
| 151 | Selected: h.id == selected, |
| 152 | MessageCount: len(msgs), |
| 153 | Turns: turns, |
| 154 | Preview: preview, |
| 155 | } |
| 156 | } |
| 157 | |
| 158 | // headList lists every head in declaration order with the selected one marked |
| 159 | // and covered heads flagged: retiring one of those loses no message. |
| 160 | func (st *sessionDAGState) headList() []SessionHead { |
| 161 | selected := st.selectedHead() |
| 162 | onChain := map[string]struct{}{} |
| 163 | for _, id := range st.chainIDs(selected) { |
| 164 | onChain[id] = struct{}{} |
| 165 | } |
| 166 | out := make([]SessionHead, 0, len(st.headOrder)) |
| 167 | for _, id := range st.headOrder { |
| 168 | h := st.heads[id] |
| 169 | if h == nil { |
| 170 | continue |
| 171 | } |
| 172 | rec := st.headRecord(id, selected) |
| 173 | if id != selected && !h.retired { |
| 174 | _, rec.Covered = onChain[h.leaf] |
| 175 | rec.Covered = rec.Covered || h.leaf == "" |
| 176 | } |
| 177 | out = append(out, rec) |
| 178 | } |
| 179 | return out |
| 180 | } |
| 181 | |
| 182 | // liveHeads returns the ids of heads that have not been retired. |
| 183 | func (st *sessionDAGState) liveHeads() []string { |
| 184 | out := make([]string, 0, len(st.headOrder)) |
| 185 | for _, id := range st.headOrder { |
| 186 | if h := st.heads[id]; h != nil && !h.retired { |
| 187 | out = append(out, id) |
| 188 | } |
| 189 | } |
| 190 | return out |
| 191 | } |
| 192 | |
| 193 | // reachable returns every node id on the chain of any live head. |
| 194 | func (st *sessionDAGState) reachable() map[string]struct{} { |
| 195 | keep := map[string]struct{}{} |
| 196 | for _, id := range st.liveHeads() { |
| 197 | for _, mid := range st.chainIDs(id) { |
| 198 | keep[mid] = struct{}{} |
| 199 | } |
| 200 | } |
| 201 | return keep |
| 202 | } |
| 203 | |
| 204 | // ListSessionHeads replays a schema-2 log and returns its heads. A schema-1 |
| 205 | // session has no heads and returns nil, nil. |
| 206 | func ListSessionHeads(path string) ([]SessionHead, error) { |
| 207 | return listSessionHeads(context.Background(), path, defaultSessionReplayLimits, false) |
| 208 | } |
| 209 | |
| 210 | // ListSessionHeadsForMigration enumerates a frozen source without the cumulative |
| 211 | // interactive replay budget. The migration owner must freeze the source first. |
| 212 | func ListSessionHeadsForMigration(ctx context.Context, path string) ([]SessionHead, error) { |
| 213 | return listSessionHeads(ctx, path, migrationSessionReplayLimits(), true) |
| 214 | } |
| 215 | |
| 216 | func listSessionHeads(ctx context.Context, path string, limits sessionReplayLimits, strict bool) ([]SessionHead, error) { |
| 217 | probe, err := probeSessionEventLogWithLimits(path, limits) |
| 218 | if err != nil { |
| 219 | return nil, err |
| 220 | } |
| 221 | if !probe.dag { |
| 222 | return nil, nil |
| 223 | } |
| 224 | st, err := replaySessionDAG(ctx, store.SessionEventLog(path), limits) |
| 225 | if err != nil { |
| 226 | return nil, fmt.Errorf("list session heads: %w", err) |
| 227 | } |
| 228 | if strict && st.damaged { |
| 229 | return nil, fmt.Errorf("list session heads: incomplete legacy DAG") |
| 230 | } |
| 231 | heads := st.headList() |
| 232 | slices.SortStableFunc(heads, func(a, b SessionHead) int { |
| 233 | return a.CreatedAt.Compare(b.CreatedAt) |
| 234 | }) |
| 235 | return heads, nil |
| 236 | } |
| 237 |