From 3db747d5185875517109463e41aafe1791e8ebf4 Mon Sep 17 00:00:00 2001
From: liurenfeng94-ops <279598012+liurenfeng94-ops@users.noreply.github.com>
Date: Tue, 28 Jul 2026 19:17:49 +0800
Subject: [PATCH] Persist last save per project

---
 src/appState.ts               |  7 +++++-
 src/projectSettings.ts        | 40 +++++++++++++++++++++++++++++++++++
 test/project-settings.test.ts | 33 +++++++++++++++++++++++++++++
 3 files changed, 79 insertions(+), 1 deletion(-)
 create mode 100644 src/projectSettings.ts
 create mode 100644 test/project-settings.test.ts

diff --git a/src/appState.ts b/src/appState.ts
index b37c324..43967d8 100644
--- a/src/appState.ts
+++ b/src/appState.ts
@@ -8,6 +8,7 @@ import { getTracePanel, isTraceViewAlive, postMessage } from './webview'
 import { getProjectName, getWorkspacePath } from './storage'
 import { setStatusBarState } from './statusBar'
 import { sendTraceDir } from './commands'
+import { readProjectSettings, writeProjectSettings } from './projectSettings'
 
 export const afterWatches = nextTick
 
@@ -86,7 +87,10 @@ export async function initAppState(extensionContext: vscode.ExtensionContext) {
     }
 
     getSaves(projectPath.value)
-    saveName.value = 'default'
+    const projectSettings = readProjectSettings(projectPath.value)
+    saveName.value = projectSettings.lastSaveName && saveNames.value.includes(projectSettings.lastSaveName)
+      ? projectSettings.lastSaveName
+      : 'default'
   }, name => postMessage({ message: 'projectOpen', name }))
 
   watchT('savePath', (path) => {
@@ -116,6 +120,7 @@ export async function initAppState(extensionContext: vscode.ExtensionContext) {
 
     setStatusBarState('saveName', saveName.value)
     tracePath.value = join(projectPath.value, name, 'traces')
+    writeProjectSettings(projectPath.value, { lastSaveName: name })
 
     void sendTraceDir(tracePath.value)
   }, (name) => {
diff --git a/src/projectSettings.ts b/src/projectSettings.ts
new file mode 100644
index 0000000..0904b15
--- /dev/null
+++ b/src/projectSettings.ts
@@ -0,0 +1,40 @@
+import { existsSync, readFileSync, writeFileSync } from 'node:fs'
+import { join } from 'node:path'
+
+export interface ProjectSettings {
+  lastSaveName?: string
+}
+
+const projectSettingsFileName = 'tracer-project-settings.json'
+
+export function getProjectSettingsPath(projectPath: string) {
+  return join(projectPath, projectSettingsFileName)
+}
+
+function parseProjectSettings(value: unknown): ProjectSettings {
+  if (!value || typeof value !== 'object')
+    return {}
+
+  const settings = value as Record<string, unknown>
+
+  return {
+    lastSaveName: typeof settings.lastSaveName === 'string' ? settings.lastSaveName : undefined,
+  }
+}
+
+export function readProjectSettings(projectPath: string): ProjectSettings {
+  const settingsPath = getProjectSettingsPath(projectPath)
+  if (!existsSync(settingsPath))
+    return {}
+
+  try {
+    return parseProjectSettings(JSON.parse(readFileSync(settingsPath, 'utf8')))
+  }
+  catch {
+    return {}
+  }
+}
+
+export function writeProjectSettings(projectPath: string, settings: ProjectSettings) {
+  writeFileSync(getProjectSettingsPath(projectPath), `${JSON.stringify(settings, null, 2)}\n`)
+}
diff --git a/test/project-settings.test.ts b/test/project-settings.test.ts
new file mode 100644
index 0000000..830f3c1
--- /dev/null
+++ b/test/project-settings.test.ts
@@ -0,0 +1,33 @@
+import { mkdirSync, mkdtempSync, writeFileSync } from 'node:fs'
+import { join } from 'node:path'
+import { tmpdir } from 'node:os'
+import { describe, expect, it } from 'vitest'
+import { getProjectSettingsPath, readProjectSettings, writeProjectSettings } from '../src/projectSettings'
+
+function tempProjectPath() {
+  const path = mkdtempSync(join(tmpdir(), 'tracer-project-settings-'))
+  mkdirSync(path, { recursive: true })
+  return path
+}
+
+describe('project settings', () => {
+  it('persists the last selected save name per project', () => {
+    const projectPath = tempProjectPath()
+
+    writeProjectSettings(projectPath, { lastSaveName: 'feature/fast-path' })
+
+    expect(readProjectSettings(projectPath)).toEqual({ lastSaveName: 'feature/fast-path' })
+  })
+
+  it('falls back to empty settings when the file is missing or invalid', () => {
+    const projectPath = tempProjectPath()
+
+    expect(readProjectSettings(projectPath)).toEqual({})
+
+    writeFileSync(getProjectSettingsPath(projectPath), '{not-json')
+    expect(readProjectSettings(projectPath)).toEqual({})
+
+    writeFileSync(getProjectSettingsPath(projectPath), JSON.stringify({ lastSaveName: 123 }))
+    expect(readProjectSettings(projectPath)).toEqual({ lastSaveName: undefined })
+  })
+})