feat(#60): pure turn-progress reducer (INV-46)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/turnProgress.ts

@@ -0,0 +1,122 @@
+/**
+ * turnProgress.ts — pure reduction of @cline/sdk Agent runtime events into a
+ * small UI-facing progress snapshot (#60, spec coauthoring-live-progress.md §3.2).
+ *
+ * INV-43: vscode-free. INV-46: a pure function — no vscode, no SDK runtime
+ * dependency (`AgentRuntimeEvent` is imported TYPE-only, so it is erased at
+ * compile and never pulls the ESM SDK into the bundle). All event→state logic
+ * lives here so it is unit-tested in isolation; the UI call sites only format and
+ * relay snapshots.
+ */
+import type { AgentRuntimeEvent } from "@cline/shared";
+
+export type TurnPhase = "thinking" | "writing" | "tool";
+
+export interface TurnProgressSnapshot {
+  phase: TurnPhase;
+  /** present iff phase === "tool" — the running tool's name. */
+  tool?: string;
+  /** accumulated assistant-text length so far. */
+  chars: number;
+  /** running total tokens (input+output); undefined until the first usage event. */
+  tokens?: number;
+  /** the new assistant-text chunk since the last snapshot (for the OutputChannel). */
+  textDelta?: string;
+}
+
+export interface TurnProgressState {
+  phase: TurnPhase;
+  chars: number;
+  tokens?: number;
+  /** stack of tool names currently running (depth-tracked for overlap). */
+  activeTools: string[];
+  /** true once any assistant text has streamed (tool-finish then reverts to writing). */
+  sawText: boolean;
+}
+
+export function createTurnProgressState(): TurnProgressState {
+  return { phase: "thinking", chars: 0, tokens: undefined, activeTools: [], sawText: false };
+}
+
+function restingPhase(state: TurnProgressState): TurnPhase {
+  if (state.activeTools.length) return "tool";
+  return state.sawText ? "writing" : "thinking";
+}
+
+function toSnapshot(state: TurnProgressState, textDelta?: string): TurnProgressSnapshot {
+  return {
+    phase: state.phase,
+    tool: state.phase === "tool" ? state.activeTools[state.activeTools.length - 1] : undefined,
+    chars: state.chars,
+    tokens: state.tokens,
+    textDelta,
+  };
+}
+
+/**
+ * Fold one SDK event into the state, returning the next state and the snapshot to
+ * emit (snapshot undefined for events that don't change the surface).
+ */
+export function reduceTurnProgress(
+  state: TurnProgressState,
+  event: AgentRuntimeEvent,
+): { state: TurnProgressState; snapshot?: TurnProgressSnapshot } {
+  switch (event.type) {
+    case "run-started":
+    case "turn-started": {
+      const next: TurnProgressState = { ...state, phase: restingPhase(state) };
+      return { state: next, snapshot: toSnapshot(next) };
+    }
+    case "assistant-text-delta": {
+      const next: TurnProgressState = {
+        ...state,
+        phase: state.activeTools.length ? "tool" : "writing",
+        chars: event.accumulatedText.length,
+        sawText: true,
+      };
+      return { state: next, snapshot: toSnapshot(next, event.text) };
+    }
+    case "assistant-reasoning-delta": {
+      // Reasoning TEXT is not surfaced (operator fork); collapse to motion only.
+      const next: TurnProgressState = { ...state, phase: state.activeTools.length ? "tool" : "thinking" };
+      return { state: next, snapshot: toSnapshot(next) };
+    }
+    case "tool-started": {
+      const activeTools = [...state.activeTools, event.toolCall.toolName];
+      const next: TurnProgressState = { ...state, phase: "tool", activeTools };
+      return { state: next, snapshot: toSnapshot(next) };
+    }
+    case "tool-updated": {
+      const next: TurnProgressState = { ...state, phase: "tool" };
+      return { state: next, snapshot: toSnapshot(next) };
+    }
+    case "tool-finished": {
+      const name = event.toolCall.toolName;
+      const idx = state.activeTools.lastIndexOf(name);
+      const activeTools = idx >= 0 ? state.activeTools.filter((_, i) => i !== idx) : state.activeTools.slice(0, -1);
+      const next: TurnProgressState = { ...state, activeTools, phase: "thinking" };
+      next.phase = restingPhase(next);
+      return { state: next, snapshot: toSnapshot(next) };
+    }
+    case "usage-updated": {
+      const tokens = event.usage.inputTokens + event.usage.outputTokens || undefined;
+      const next: TurnProgressState = { ...state, tokens };
+      return { state: next, snapshot: toSnapshot(next) };
+    }
+    default:
+      return { state };
+  }
+}
+
+/** Render the notification activity line from a snapshot (pure; spec §2.1). */
+export function formatProgressLine(s: TurnProgressSnapshot): string {
+  let head: string;
+  if (s.phase === "tool") head = `running ${s.tool ?? "tool"}…`;
+  else if (s.phase === "writing") head = `writing… (${s.chars} chars)`;
+  else head = "thinking…";
+  return s.tokens ? `${head} · ${formatTokens(s.tokens)} tokens` : head;
+}
+
+export function formatTokens(n: number): string {
+  return n >= 1000 ? `${(n / 1000).toFixed(1)}k` : String(n);
+}