Add pane state parser with test coverage

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

src/features/tmux-subagent/pane-state-parser.ts

@@ -0,0 +1,125 @@
+import type { TmuxPaneInfo } from "./types"
+
+const MANDATORY_PANE_FIELD_COUNT = 8
+
+type ParsedPaneState = {
+  windowWidth: number
+  windowHeight: number
+  panes: TmuxPaneInfo[]
+}
+
+type ParsedPaneLine = {
+  pane: TmuxPaneInfo
+  windowWidth: number
+  windowHeight: number
+}
+
+type MandatoryPaneFields = [
+  paneId: string,
+  widthString: string,
+  heightString: string,
+  leftString: string,
+  topString: string,
+  activeString: string,
+  windowWidthString: string,
+  windowHeightString: string,
+]
+
+export function parsePaneStateOutput(stdout: string): ParsedPaneState | null {
+  const lines = stdout
+    .split("\n")
+    .map((line) => line.replace(/\r$/, ""))
+    .filter((line) => line.length > 0)
+
+  if (lines.length === 0) return null
+
+  const parsedPaneLines = lines
+    .map(parsePaneLine)
+    .filter((parsedPaneLine): parsedPaneLine is ParsedPaneLine => parsedPaneLine !== null)
+
+  if (parsedPaneLines.length === 0) return null
+
+  const latestPaneLine = parsedPaneLines[parsedPaneLines.length - 1]
+  if (!latestPaneLine) return null
+
+  return {
+    windowWidth: latestPaneLine.windowWidth,
+    windowHeight: latestPaneLine.windowHeight,
+    panes: parsedPaneLines.map(({ pane }) => pane),
+  }
+}
+
+function parsePaneLine(line: string): ParsedPaneLine | null {
+  const fields = line.split("\t")
+  const mandatoryFields = getMandatoryPaneFields(fields)
+  if (!mandatoryFields) return null
+
+  const [paneId, widthString, heightString, leftString, topString, activeString, windowWidthString, windowHeightString] = mandatoryFields
+
+  const width = parseInteger(widthString)
+  const height = parseInteger(heightString)
+  const left = parseInteger(leftString)
+  const top = parseInteger(topString)
+  const windowWidth = parseInteger(windowWidthString)
+  const windowHeight = parseInteger(windowHeightString)
+
+  if (
+    width === null ||
+    height === null ||
+    left === null ||
+    top === null ||
+    windowWidth === null ||
+    windowHeight === null
+  ) {
+    return null
+  }
+
+  return {
+    pane: {
+      paneId,
+      width,
+      height,
+      left,
+      top,
+      title: fields.slice(MANDATORY_PANE_FIELD_COUNT).join("\t"),
+      isActive: activeString === "1",
+    },
+    windowWidth,
+    windowHeight,
+  }
+}
+
+function getMandatoryPaneFields(fields: string[]): MandatoryPaneFields | null {
+  if (fields.length < MANDATORY_PANE_FIELD_COUNT) return null
+
+  const [paneId, widthString, heightString, leftString, topString, activeString, windowWidthString, windowHeightString] = fields
+
+  if (
+    paneId === undefined ||
+    widthString === undefined ||
+    heightString === undefined ||
+    leftString === undefined ||
+    topString === undefined ||
+    activeString === undefined ||
+    windowWidthString === undefined ||
+    windowHeightString === undefined
+  ) {
+    return null
+  }
+
+  return [
+    paneId,
+    widthString,
+    heightString,
+    leftString,
+    topString,
+    activeString,
+    windowWidthString,
+    windowHeightString,
+  ]
+}
+
+function parseInteger(value: string): number | null {
+  const parsedValue = Number.parseInt(value, 10)
+  return Number.isNaN(parsedValue) ? null : parsedValue
+}

src/features/tmux-subagent/pane-state-querier.test.ts

@@ -0,0 +1,75 @@
+/// <reference types="bun-types/test" />
+
+import { describe, expect, it } from "bun:test"
+import { parsePaneStateOutput } from "./pane-state-parser"
+
+describe("parsePaneStateOutput", () => {
+  it("accepts a single pane when tmux omits the empty trailing title field", () => {
+    // given
+    const stdout = "%0\t120\t40\t0\t0\t1\t120\t40\n"
+
+    // when
+    const result = parsePaneStateOutput(stdout)
+
+    // then
+    expect(result).not.toBe(null)
+    expect(result).toEqual({
+      windowWidth: 120,
+      windowHeight: 40,
+      panes: [
+        {
+          paneId: "%0",
+          width: 120,
+          height: 40,
+          left: 0,
+          top: 0,
+          title: "",
+          isActive: true,
+        },
+      ],
+    })
+  })
+
+  it("handles CRLF line endings without dropping panes", () => {
+    // given
+    const stdout = "%0\t120\t40\t0\t0\t1\t120\t40\r\n%1\t60\t40\t60\t0\t0\t120\t40\tagent\r\n"
+
+    // when
+    const result = parsePaneStateOutput(stdout)
+
+    // then
+    expect(result).not.toBe(null)
+    expect(result?.panes).toEqual([
+      {
+        paneId: "%0",
+        width: 120,
+        height: 40,
+        left: 0,
+        top: 0,
+        title: "",
+        isActive: true,
+      },
+      {
+        paneId: "%1",
+        width: 60,
+        height: 40,
+        left: 60,
+        top: 0,
+        title: "agent",
+        isActive: false,
+      },
+    ])
+  })
+
+  it("preserves tabs inside pane titles", () => {
+    // given
+    const stdout = "%0\t120\t40\t0\t0\t1\t120\t40\ttitle\twith\ttabs\n"
+
+    // when
+    const result = parsePaneStateOutput(stdout)
+
+    // then
+    expect(result).not.toBe(null)
+    expect(result?.panes[0]?.title).toBe("title\twith\ttabs")
+  })
+})