fix: improve JSON extraction to handle UTF-8 Chinese characters properly

- Replace byte-based brace counting with UTF-8 aware rune iteration
- Add proper string state tracking to handle escaped quotes
- Add comprehensive test cases for Chinese character handling
- Fix parsing errors when JSON contains Chinese text like 2048经典

uixt/ai/utils_test.go

@@ -9,39 +9,12 @@ import (
 func TestExtractJSONFromContent(t *testing.T) {
 	tests := []struct {
 		name     string
-		input    string
+		content  string
 		expected string
 	}{
 		{
-			name:     "valid JSON",
-			input:    `{"content": "test", "thought": "test"}`,
-			expected: `{"content": "test", "thought": "test"}`,
-		},
-		{
-			name:  "JSON in markdown",
-			input: "```json\n{\n  \"content\": \"test\"\n}\n```",
-			expected: `{
-  "content": "test"
-}`,
-		},
-		{
-			name:     "incomplete JSON without closing brace",
-			input:    `{"content": "incomplete json"`,
-			expected: "",
-		},
-		{
-			name:     "incomplete JSON with missing closing brace",
-			input:    `{"content": "incomplete json", "missing_closing_brace": true`,
-			expected: "",
-		},
-		{
-			name:     "plain text",
-			input:    "This is just plain text",
-			expected: "",
-		},
-		{
-			name: "complex nested JSON with arrays",
-			input: `{
+			name: "simple JSON",
+			content: `{
   "actions": [
     {
       "action_type": "click",
@@ -64,15 +37,161 @@ func TestExtractJSONFromContent(t *testing.T) {
   ],
   "thought": "点击桌面上的抖音应用图标以启动抖音",
   "error": null
+}`,
+		},
+		{
+			name: "JSON with Chinese characters in strings",
+			content: `{
+  "actions": [
+    {
+      "action_type": "type",
+      "action_inputs": {
+        "content": "2048经典"
+      }
+    }
+  ],
+  "thought": "搜索框已经清空了，现在我要输入\"2048经典\"这个关键词。看到键盘已经弹出来了，正好可以直接开始输入。这样一来，就能找到我们想要玩的那个小游戏了。",
+  "error": null
+}`,
+			expected: `{
+  "actions": [
+    {
+      "action_type": "type",
+      "action_inputs": {
+        "content": "2048经典"
+      }
+    }
+  ],
+  "thought": "搜索框已经清空了，现在我要输入\"2048经典\"这个关键词。看到键盘已经弹出来了，正好可以直接开始输入。这样一来，就能找到我们想要玩的那个小游戏了。",
+  "error": null
+}`,
+		},
+		{
+			name: "JSON with markdown wrapper",
+			content: "```json\n" + `{
+  "actions": [
+    {
+      "action_type": "click",
+      "action_inputs": {
+        "start_box": [100, 200, 150, 250]
+      }
+    }
+  ],
+  "thought": "点击按钮",
+  "error": null
+}` + "\n```",
+			expected: `{
+  "actions": [
+    {
+      "action_type": "click",
+      "action_inputs": {
+        "start_box": [100, 200, 150, 250]
+      }
+    }
+  ],
+  "thought": "点击按钮",
+  "error": null
+}`,
+		},
+		{
+			name: "JSON embedded in text with Chinese",
+			content: `这是一个包含中文的响应：{
+  "actions": [
+    {
+      "action_type": "type",
+      "action_inputs": {
+        "content": "测试内容"
+      }
+    }
+  ],
+  "thought": "这是一个测试思路",
+  "error": null
+} 后面还有一些文本`,
+			expected: `{
+  "actions": [
+    {
+      "action_type": "type",
+      "action_inputs": {
+        "content": "测试内容"
+      }
+    }
+  ],
+  "thought": "这是一个测试思路",
+  "error": null
+}`,
+		},
+		{
+			name: "JSON with escaped quotes and Chinese",
+			content: `{
+  "actions": [
+    {
+      "action_type": "type",
+      "action_inputs": {
+        "content": "他说：\"你好，世界！\""
+      }
+    }
+  ],
+  "thought": "输入包含引号的中文文本",
+  "error": null
+}`,
+			expected: `{
+  "actions": [
+    {
+      "action_type": "type",
+      "action_inputs": {
+        "content": "他说：\"你好，世界！\""
+      }
+    }
+  ],
+  "thought": "输入包含引号的中文文本",
+  "error": null
+}`,
+		},
+		{
+			name:     "no JSON content",
+			content:  "这只是一些普通的文本，没有JSON内容",
+			expected: "",
+		},
+		{
+			name: "nested JSON objects with Chinese",
+			content: `{
+  "actions": [
+    {
+      "action_type": "click",
+      "action_inputs": {
+        "start_box": [100, 200, 150, 250],
+        "metadata": {
+          "description": "点击操作",
+          "target": "按钮"
+        }
+      }
+    }
+  ],
+  "thought": "执行嵌套对象的点击操作",
+  "error": null
+}`,
+			expected: `{
+  "actions": [
+    {
+      "action_type": "click",
+      "action_inputs": {
+        "start_box": [100, 200, 150, 250],
+        "metadata": {
+          "description": "点击操作",
+          "target": "按钮"
+        }
+      }
+    }
+  ],
+  "thought": "执行嵌套对象的点击操作",
+  "error": null
 }`,
 		},
 	}
 
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			result := extractJSONFromContent(tt.input)
-			t.Logf("Input: %s", tt.input)
-			t.Logf("Output: %s", result)
+			result := extractJSONFromContent(tt.content)
 			assert.Equal(t, tt.expected, result)
 		})
 	}