| 1 | import { sameSessionIdentity, sessionIdentityStableKey, type SessionIdentity } from "./sessionIdentity"; |
| 2 | |
| 3 | /** Live-turn markers that a lagging history snapshot must not replace. */ |
| 4 | export type HydrateLiveState = { |
| 5 | running?: boolean; |
| 6 | turnActive?: boolean; |
| 7 | live?: unknown; |
| 8 | currentAssistant?: unknown; |
| 9 | pendingUser?: unknown; |
| 10 | historyTotalTurns?: number; |
| 11 | items: ReadonlyArray<{ kind: string; streaming?: boolean; status?: string }>; |
| 12 | historyRevision?: number; |
| 13 | historyDigest?: string; |
| 14 | }; |
| 15 | |
| 16 | export type HydratedHistoryApplyMode = "replace" | "prepend" | "skip"; |
| 17 | |
| 18 | export type HydrateProjection = { |
| 19 | items: ReadonlyArray<unknown>; |
| 20 | revision?: number; |
| 21 | digest?: string; |
| 22 | }; |
| 23 | |
| 24 | export type SessionHydrateIdentity = SessionIdentity; |
| 25 | |
| 26 | export type HydrateSurfacePolicy = "preserve-current" | "replace-surface"; |
| 27 | |
| 28 | type UnboundLiveSurfaceState = HydrateLiveState & { |
| 29 | hydrateHistoryLoaded?: boolean; |
| 30 | }; |
| 31 | |
| 32 | /** A surface may retain content only when the target session is provably the same. */ |
| 33 | export function sameSessionHydrateIdentity( |
| 34 | target: SessionHydrateIdentity | undefined, |
| 35 | current: SessionHydrateIdentity | undefined, |
| 36 | ): boolean { |
| 37 | return sameSessionIdentity(target, current); |
| 38 | } |
| 39 | |
| 40 | /** |
| 41 | * Adopt only a live runtime tail that has never been bound to persisted |
| 42 | * history. This is the compatibility bridge for background runtime events |
| 43 | * that predate the tab metadata snapshot: it must never retain a resident |
| 44 | * transcript merely because the tab id matches. |
| 45 | */ |
| 46 | export function canAdoptUnboundLiveSurface( |
| 47 | target: SessionHydrateIdentity | undefined, |
| 48 | current: SessionHydrateIdentity | undefined, |
| 49 | state: UnboundLiveSurfaceState | undefined, |
| 50 | backendRunning: boolean, |
| 51 | targetRuntimeEpoch?: string, |
| 52 | currentRuntimeEpoch?: string, |
| 53 | ): boolean { |
| 54 | if (!backendRunning || !state) return false; |
| 55 | if (!sessionIdentityStableKey(target) || sessionIdentityStableKey(current)) return false; |
| 56 | if (state.hydrateHistoryLoaded || (state.historyTotalTurns ?? 0) > 0) return false; |
| 57 | if (state.historyRevision !== undefined || (state.historyDigest ?? "").trim()) return false; |
| 58 | if (!state.running && !state.turnActive) return false; |
| 59 | if (targetRuntimeEpoch && currentRuntimeEpoch && targetRuntimeEpoch !== currentRuntimeEpoch) return false; |
| 60 | return Boolean( |
| 61 | state.live || |
| 62 | state.currentAssistant || |
| 63 | state.pendingUser !== undefined || |
| 64 | state.items.some((item) => |
| 65 | (item.kind === "assistant" && item.streaming) || |
| 66 | (item.kind === "tool" && item.status === "running"), |
| 67 | ), |
| 68 | ); |
| 69 | } |
| 70 | |
| 71 | export function shouldPreferResidentHistory(reset: boolean, preserveCachedHistory?: boolean): boolean { |
| 72 | return !reset && preserveCachedHistory !== false; |
| 73 | } |
| 74 | |
| 75 | function sameHydrateFingerprint(state: HydrateLiveState | undefined, projection: HydrateProjection | undefined): boolean { |
| 76 | if (!state || !projection) return false; |
| 77 | const revision = projection.revision ?? 0; |
| 78 | const digest = (projection.digest ?? "").trim(); |
| 79 | if (revision > 0 && state.historyRevision === revision) return true; |
| 80 | if (digest !== "" && (state.historyDigest ?? "") === digest) return true; |
| 81 | return false; |
| 82 | } |
| 83 | |
| 84 | export function isStaleResidentProjection( |
| 85 | state: HydrateLiveState | undefined, |
| 86 | projection: HydrateProjection | undefined, |
| 87 | ): boolean { |
| 88 | if (!state || !projection || state.items.length === 0) return false; |
| 89 | if (projection.items.length >= state.items.length) return false; |
| 90 | return sameHydrateFingerprint(state, projection); |
| 91 | } |
| 92 | |
| 93 | // A live turn is only "cached" once a history page has landed behind it. |
| 94 | // Without that, a session opened mid-stream reports a cached turn, skips the |
| 95 | // fetch, and streams over a blank transcript. |
| 96 | export function hasCachedLiveTurn(state: HydrateLiveState | undefined): boolean { |
| 97 | if (!state?.running && !state?.turnActive) return false; |
| 98 | if ((state.historyTotalTurns ?? 0) === 0) return false; |
| 99 | if (state.live || state.currentAssistant || state.pendingUser !== undefined) return true; |
| 100 | return state.items.some((item) => |
| 101 | (item.kind === "assistant" && item.streaming) || |
| 102 | (item.kind === "tool" && item.status === "running"), |
| 103 | ); |
| 104 | } |
| 105 | |
| 106 | export function hasReusableCachedTranscript( |
| 107 | state: (HydrateLiveState & { meta?: SessionHydrateIdentity }) | undefined, |
| 108 | target: SessionHydrateIdentity, |
| 109 | revision?: number, |
| 110 | digest?: string, |
| 111 | ): boolean { |
| 112 | if (!state || state.items.length === 0 || state.historyTotalTurns === 0) return false; |
| 113 | if (sessionIdentityStableKey(target) && !sameSessionHydrateIdentity(target, state.meta)) return false; |
| 114 | if (typeof revision === "number" && revision > 0) { |
| 115 | return state.historyRevision === revision && (digest ?? "") === (state.historyDigest ?? ""); |
| 116 | } |
| 117 | if ((digest ?? "").trim() !== "") return state.historyDigest === digest; |
| 118 | // Missing backend fingerprints must not bless a resident page that already |
| 119 | // has one; the sidecar may be between atomic replacements. |
| 120 | return state.historyRevision === undefined && !state.historyDigest; |
| 121 | } |
| 122 | |
| 123 | // An empty surface has to apply history or switch-back shows Welcome. A turn |
| 124 | // that has already streamed rows keeps them — but a tab with no history page |
| 125 | // behind it still gets one, prepended, instead of a blank transcript above the |
| 126 | // live turn. Only an already-hydrated live turn is left alone. An idle |
| 127 | // same-fingerprint resident page that is shorter than the visible transcript |
| 128 | // is skipped so Retry/clear cannot roll the chat back. |
| 129 | export function hydratedHistoryApplyMode( |
| 130 | skipHistory: boolean, |
| 131 | hasProjection: boolean, |
| 132 | foregroundTurnActive: boolean, |
| 133 | state: HydrateLiveState | undefined, |
| 134 | projection?: HydrateProjection, |
| 135 | ): HydratedHistoryApplyMode { |
| 136 | if (skipHistory || !hasProjection) return "skip"; |
| 137 | if (!foregroundTurnActive) return isStaleResidentProjection(state, projection) ? "skip" : "replace"; |
| 138 | if ((state?.items.length ?? 0) === 0 && !hasCachedLiveTurn(state)) return "replace"; |
| 139 | return (state?.historyTotalTurns ?? 0) === 0 ? "prepend" : "skip"; |
| 140 | } |
| 141 | |
| 142 | type SignatureItem = { |
| 143 | kind: string; |
| 144 | id: string; |
| 145 | messageId?: string; |
| 146 | text?: string; |
| 147 | reasoning?: string; |
| 148 | name?: string; |
| 149 | level?: string; |
| 150 | trigger?: string; |
| 151 | messages?: number; |
| 152 | surfaceKey?: string; |
| 153 | generation?: number; |
| 154 | }; |
| 155 | |
| 156 | function itemSignature(item: SignatureItem): string { |
| 157 | switch (item.kind) { |
| 158 | case "tool": return `tool|${item.id}|${item.name ?? ""}`; |
| 159 | case "extension": return `extension|${item.surfaceKey ?? ""}|${item.generation ?? 0}`; |
| 160 | case "compaction": return `compaction|${item.trigger ?? ""}|${item.messages ?? 0}`; |
| 161 | default: return `${item.kind}|${item.level ?? ""}|${item.text ?? ""}|${item.reasoning ?? ""}`; |
| 162 | } |
| 163 | } |
| 164 | |
| 165 | // A page read while its turn is live can already carry rows the live stream |
| 166 | // rendered. Only a suffix of the page can overlap a prefix of the live rows, so |
| 167 | // the longest such match is the duplicate set. |
| 168 | export function duplicateLiveItemIds( |
| 169 | pageItems: readonly SignatureItem[], |
| 170 | liveItems: readonly SignatureItem[], |
| 171 | ): string[] { |
| 172 | // Stable backend identities are independent of where a page cuts the live |
| 173 | // turn. In particular page [A,B,C] already covers live [A,B]. Content equality |
| 174 | // cannot establish this relation: two messages may intentionally be equal. |
| 175 | const identity = (item: SignatureItem) => item.messageId ? `m:${item.messageId}` : item.id; |
| 176 | const isIdentified = (item: SignatureItem) => !!item.messageId || item.id.startsWith("m:"); |
| 177 | const canonicalIds = new Set(pageItems.filter((item) => isIdentified(item) || item.kind === "tool").map(identity)); |
| 178 | const identified = liveItems.filter((item) => canonicalIds.has(identity(item))).map((item) => item.id); |
| 179 | if (pageItems.some(isIdentified) || liveItems.some(isIdentified)) return identified; |
| 180 | for (let k = Math.min(pageItems.length, liveItems.length); k > 0; k -= 1) { |
| 181 | let same = true; |
| 182 | for (let i = 0; i < k && same; i += 1) { |
| 183 | same = itemSignature(pageItems[pageItems.length - k + i]) === itemSignature(liveItems[i]); |
| 184 | } |
| 185 | if (same) return liveItems.slice(0, k).map((item) => item.id); |
| 186 | } |
| 187 | return []; |
| 188 | } |
| 189 | |
| 190 | export function sameSessionPlaceholderItems<T>( |
| 191 | target: SessionHydrateIdentity | undefined, |
| 192 | prev: { meta?: SessionHydrateIdentity; items?: T[] } | undefined, |
| 193 | ): T[] | undefined { |
| 194 | return sameSessionHydrateIdentity(target, prev?.meta) ? prev?.items : undefined; |
| 195 | } |
| 196 |