Model selection rewrite lifecycle transitions

src/features/selection-rewrite/model.ts

@@ -23,6 +23,60 @@ export interface SelectionRewriteRuntimeSettings {
   rewriteSelectionEffort: ReasoningEffort | null;
 }
 
+export type SelectionRewriteLifecycleEvent =
+  | { type: "generation-started"; instruction: string }
+  | { type: "preview-updated"; text: string }
+  | { type: "generation-succeeded"; replacementText: string }
+  | { type: "generation-failed"; debugText: string | null }
+  | { type: "cancelled" }
+  | { type: "applied" };
+
 export function canApplySelectionRewrite(currentText: string, originalText: string): boolean {
   return currentText === originalText;
 }
+
+export function transitionSelectionRewriteState(
+  state: SelectionRewriteState,
+  event: SelectionRewriteLifecycleEvent,
+): SelectionRewriteState {
+  switch (event.type) {
+    case "generation-started":
+      return {
+        ...state,
+        instruction: event.instruction,
+        status: "generating",
+        streamText: "",
+        replacementText: null,
+        debugText: null,
+      };
+    case "preview-updated":
+      if (state.status !== "generating") return state;
+      return { ...state, streamText: event.text };
+    case "generation-succeeded":
+      if (state.status !== "generating") return state;
+      return {
+        ...state,
+        status: "preview",
+        streamText: "",
+        replacementText: event.replacementText,
+      };
+    case "generation-failed":
+      if (state.status !== "generating") return state;
+      return {
+        ...state,
+        status: "failed",
+        streamText: "",
+        debugText: event.debugText,
+      };
+    case "cancelled":
+      return {
+        ...state,
+        status: "cancelled",
+      };
+    case "applied":
+      return {
+        ...state,
+        status: "applied",
+      };
+  }
+}

src/features/selection-rewrite/popover.tsx

@@ -8,7 +8,13 @@ import { renderReactRoot, unmountReactRoot } from "../../shared/ui/react-root";
 import { syncTextareaHeight } from "../../shared/ui/textarea-autogrow";
 import { buildSelectionUnifiedDiff } from "./diff";
 import { isSelectionRewriteActionKey, isSelectionRewriteGenerateKey } from "./keys";
-import { canApplySelectionRewrite, type SelectionRewriteRuntimeSettings, type SelectionRewriteState } from "./model";
+import {
+  canApplySelectionRewrite,
+  transitionSelectionRewriteState,
+  type SelectionRewriteLifecycleEvent,
+  type SelectionRewriteRuntimeSettings,
+  type SelectionRewriteState,
+} from "./model";
 import { SelectionRewriteOutputError } from "./output";
 import { positionSelectionRewritePopover } from "./position";
 import { buildSelectionRewritePrompt } from "./prompt";
@@ -126,7 +132,7 @@ export class SelectionRewritePopover {
       this.showSelectionRewritePreview(output.replacementText);
     } catch (error) {
       if (abortController.signal.aborted) {
-        this.options.state.status = "cancelled";
+        this.transitionState({ type: "cancelled" });
         return;
       }
       this.showGenerationFailure(error);
@@ -139,13 +145,13 @@ export class SelectionRewritePopover {
   }
 
   private cancel(): void {
-    this.options.state.status = "cancelled";
+    this.transitionState({ type: "cancelled" });
     this.abortController?.abort();
     this.close();
   }
 
   private updatePreview(text: string): void {
-    this.options.state.streamText = text;
+    this.transitionState({ type: "preview-updated", text });
     this.setStatus("Writing replacement", { active: true });
     this.position();
   }
@@ -164,25 +170,20 @@ export class SelectionRewritePopover {
   }
 
   private startGeneration(instruction: string): void {
-    this.options.state.instruction = instruction;
-    this.options.state.status = "generating";
-    this.options.state.streamText = "";
-    this.options.state.replacementText = null;
-    this.options.state.debugText = null;
+    this.transitionState({ type: "generation-started", instruction });
     this.renderView();
   }
 
   private showSelectionRewritePreview(replacementText: string): void {
-    this.options.state.replacementText = replacementText;
-    this.options.state.status = "preview";
-    this.options.state.streamText = "";
+    this.transitionState({ type: "generation-succeeded", replacementText });
     this.setStatus("");
   }
 
   private showGenerationFailure(error: unknown): void {
-    this.options.state.status = "failed";
-    this.options.state.debugText = error instanceof SelectionRewriteOutputError ? error.rawText : null;
-    this.options.state.streamText = "";
+    this.transitionState({
+      type: "generation-failed",
+      debugText: error instanceof SelectionRewriteOutputError ? error.rawText : null,
+    });
     this.setStatus(error instanceof Error ? error.message : String(error));
   }
 
@@ -199,10 +200,14 @@ export class SelectionRewritePopover {
     }
 
     editor.replaceRange(replacement, state.targetRange.from, state.targetRange.to, "codex-panel-rewrite");
-    state.status = "applied";
+    this.transitionState({ type: "applied" });
     this.close();
   }
 
+  private transitionState(event: SelectionRewriteLifecycleEvent): void {
+    this.options.state = transitionSelectionRewriteState(this.options.state, event);
+  }
+
   private focusApplyButton(): void {
     if (!this.elements?.applyButton || this.elements.applyButton.disabled) return;
     this.elements.applyButton.focus({ preventScroll: true });

tests/features/selection-rewrite/selection-rewrite.test.ts

@@ -9,7 +9,11 @@ import {
   isSelectionRewriteGenerateKey,
   type SelectionRewriteGenerateKeyEvent,
 } from "../../../src/features/selection-rewrite/keys";
-import { canApplySelectionRewrite, type SelectionRewriteState } from "../../../src/features/selection-rewrite/model";
+import {
+  canApplySelectionRewrite,
+  transitionSelectionRewriteState,
+  type SelectionRewriteState,
+} from "../../../src/features/selection-rewrite/model";
 import {
   parseSelectionRewriteOutput,
   selectionRewriteOutputFromTurn,
@@ -135,6 +139,46 @@ describe("selection rewrite apply guard", () => {
   });
 });
 
+describe("selection rewrite lifecycle", () => {
+  it("transitions through generation and preview states", () => {
+    const generating = transitionSelectionRewriteState(rewriteState({ replacementText: "old", debugText: "old debug" }), {
+      type: "generation-started",
+      instruction: "Shorten it.",
+    });
+
+    expect(generating).toMatchObject({
+      instruction: "Shorten it.",
+      status: "generating",
+      streamText: "",
+      replacementText: null,
+      debugText: null,
+    });
+
+    const streaming = transitionSelectionRewriteState(generating, { type: "preview-updated", text: "New" });
+    expect(streaming.streamText).toBe("New");
+
+    const preview = transitionSelectionRewriteState(streaming, { type: "generation-succeeded", replacementText: "New text." });
+    expect(preview).toMatchObject({
+      status: "preview",
+      streamText: "",
+      replacementText: "New text.",
+    });
+  });
+
+  it("ignores stale generation callbacks after generation is no longer active", () => {
+    const state = rewriteState({ status: "cancelled", streamText: "" });
+
+    expect(transitionSelectionRewriteState(state, { type: "preview-updated", text: "late" })).toBe(state);
+    expect(transitionSelectionRewriteState(state, { type: "generation-succeeded", replacementText: "late" })).toBe(state);
+    expect(transitionSelectionRewriteState(state, { type: "generation-failed", debugText: "late" })).toBe(state);
+  });
+
+  it("marks terminal user actions explicitly", () => {
+    expect(transitionSelectionRewriteState(rewriteState(), { type: "cancelled" }).status).toBe("cancelled");
+    expect(transitionSelectionRewriteState(rewriteState({ replacementText: "New text." }), { type: "applied" }).status).toBe("applied");
+  });
+});
+
 describe("selection rewrite popover", () => {
   it("enables Generate only after the instruction has content", () => {
     const popover = new SelectionRewritePopover(popoverOptions({ state: rewriteState({ instruction: "" }) }));