fix(app): prompt input quirks

packages/app/src/components/prompt-input/editor-dom.test.ts

@@ -2,17 +2,26 @@ import { describe, expect, test } from "bun:test"
 import { createTextFragment, getCursorPosition, getNodeLength, getTextLength, setCursorPosition } from "./editor-dom"
 
 describe("prompt-input editor dom", () => {
-  test("createTextFragment preserves newlines with br and zero-width placeholders", () => {
+  test("createTextFragment preserves newlines with consecutive br nodes", () => {
     const fragment = createTextFragment("foo\n\nbar")
     const container = document.createElement("div")
     container.appendChild(fragment)
 
-    expect(container.childNodes.length).toBe(5)
+    expect(container.childNodes.length).toBe(4)
+    expect(container.childNodes[0]?.textContent).toBe("foo")
+    expect((container.childNodes[1] as HTMLElement).tagName).toBe("BR")
+    expect((container.childNodes[2] as HTMLElement).tagName).toBe("BR")
+    expect(container.childNodes[3]?.textContent).toBe("bar")
+  })
+
+  test("createTextFragment keeps trailing newline as terminal break", () => {
+    const fragment = createTextFragment("foo\n")
+    const container = document.createElement("div")
+    container.appendChild(fragment)
+
+    expect(container.childNodes.length).toBe(2)
     expect(container.childNodes[0]?.textContent).toBe("foo")
     expect((container.childNodes[1] as HTMLElement).tagName).toBe("BR")
-    expect(container.childNodes[2]?.textContent).toBe("\u200B")
-    expect((container.childNodes[3] as HTMLElement).tagName).toBe("BR")
-    expect(container.childNodes[4]?.textContent).toBe("bar")
   })
 
   test("length helpers treat breaks as one char and ignore zero-width chars", () => {
@@ -48,4 +57,21 @@ describe("prompt-input editor dom", () => {
 
     container.remove()
   })
+
+  test("setCursorPosition and getCursorPosition round-trip across blank lines", () => {
+    const container = document.createElement("div")
+    container.appendChild(document.createTextNode("a"))
+    container.appendChild(document.createElement("br"))
+    container.appendChild(document.createElement("br"))
+    container.appendChild(document.createTextNode("b"))
+    document.body.appendChild(container)
+
+    setCursorPosition(container, 2)
+    expect(getCursorPosition(container)).toBe(2)
+
+    setCursorPosition(container, 3)
+    expect(getCursorPosition(container)).toBe(3)
+
+    container.remove()
+  })
 })

packages/app/src/components/prompt-input/editor-dom.ts

@@ -4,8 +4,6 @@ export function createTextFragment(content: string): DocumentFragment {
   segments.forEach((segment, index) => {
     if (segment) {
       fragment.appendChild(document.createTextNode(segment))
-    } else if (segments.length > 1) {
-      fragment.appendChild(document.createTextNode("\u200B"))
     }
     if (index < segments.length - 1) {
       fragment.appendChild(document.createElement("br"))

packages/app/src/components/prompt-input/history.test.ts

@@ -1,6 +1,12 @@
 import { describe, expect, test } from "bun:test"
 import type { Prompt } from "@/context/prompt"
-import { clonePromptParts, navigatePromptHistory, prependHistoryEntry, promptLength } from "./history"
+import {
+  canNavigateHistoryAtCursor,
+  clonePromptParts,
+  navigatePromptHistory,
+  prependHistoryEntry,
+  promptLength,
+} from "./history"
 
 const DEFAULT_PROMPT: Prompt = [{ type: "text", content: "", start: 0, end: 0 }]
 
@@ -66,4 +72,20 @@ describe("prompt-input history", () => {
     if (original[1]?.type !== "file") throw new Error("expected file")
     expect(original[1].selection?.startLine).toBe(1)
   })
+
+  test("canNavigateHistoryAtCursor only allows multiline boundaries", () => {
+    const value = "a\nb\nc"
+
+    expect(canNavigateHistoryAtCursor("up", value, 0)).toBe(true)
+    expect(canNavigateHistoryAtCursor("down", value, 0)).toBe(false)
+
+    expect(canNavigateHistoryAtCursor("up", value, 2)).toBe(false)
+    expect(canNavigateHistoryAtCursor("down", value, 2)).toBe(false)
+
+    expect(canNavigateHistoryAtCursor("up", value, 5)).toBe(false)
+    expect(canNavigateHistoryAtCursor("down", value, 5)).toBe(true)
+
+    expect(canNavigateHistoryAtCursor("up", "abc", 1)).toBe(true)
+    expect(canNavigateHistoryAtCursor("down", "abc", 1)).toBe(true)
+  })
 })

packages/app/src/components/prompt-input/history.ts

@@ -4,6 +4,13 @@ const DEFAULT_PROMPT: Prompt = [{ type: "text", content: "", start: 0, end: 0 }]
 
 export const MAX_HISTORY = 100
 
+export function canNavigateHistoryAtCursor(direction: "up" | "down", text: string, cursor: number) {
+  if (!text.includes("\n")) return true
+  const position = Math.max(0, Math.min(cursor, text.length))
+  if (direction === "up") return !text.slice(0, position).includes("\n")
+  return !text.slice(position).includes("\n")
+}
+
 export function clonePromptParts(prompt: Prompt): Prompt {
   return prompt.map((part) => {
     if (part.type === "text") return { ...part }