docs: adds code agent tutorial

docs/introduction/overview.mdx

@@ -46,27 +46,16 @@ pip install codegen
 
 ## What can I do with Codegen?
 
-Codegen enables you to programmatically manipulate code with scale and precision.
-
-<Frame caption="Call graph visualization for modal/modal-client/_Client">
-<iframe
-  width="100%"
-  height="500px"
-  scrolling="no"
-  src={`https://codegen.sh/embedded/graph?id=66e2e195-ceec-4935-876a-ed4cfc1731c7&zoom=0.5&targetNodeName=_Client`}
-  className="rounded-xl"
-  style={{
-    backgroundColor: "#15141b",
-  }}
-></iframe>
-</Frame>
-<Info>
-View source code on [modal/modal-client](https://github.com/modal-labs/modal-client/blob/cbac0d80dfd98588027ecd21850152776be3ab82/modal/client.py#L70). View codemod on [codegen.sh](https://www.codegen.sh/codemod/66e2e195-ceec-4935-876a-ed4cfc1731c7/public/diff)
-</Info>
-
-Common use cases include:
+Codegen's simple yet powerful APIs enable a range of applications, including:
 
 <CardGroup cols={2}>
+  <Card
+    title="Build a Code Agent"
+    icon="robot"
+    href="/tutorials/build-code-agent"
+  >
+    Create an intelligent agent that can analyze and manipulate your codebase using natural language.
+  </Card>
   <Card
     title="Visualize Your Codebase"
     icon="diagram-project"
@@ -76,27 +65,37 @@ Common use cases include:
   </Card>
   <Card
     title="Mine Codebase Data"
-    icon="robot"
+    icon="database"
     href="/tutorials/training-data"
   >
     Create high-quality training data for fine-tuning LLMs on your codebase.
   </Card>
   <Card
-    title="Eliminate Feature Flags"
-    icon="flag"
-    href="/tutorials/manage-feature-flags"
+    title="Build Codemods"
+    icon="wand-magic-sparkles"
+    href="/tutorials/at-a-glance#api-migrations"
   >
-    Add, remove, and update feature flags across your application.
-  </Card>
-  <Card
-    title="Organize Your Codebase"
-    icon="folder-tree"
-    href="/tutorials/organize-your-codebase"
-  >
-    Restructure files, enforce naming conventions, and improve project layout.
+    Create powerful code transformations to automate large-scale changes.
   </Card>
 </CardGroup>
 
+See below for an example call graph visualization generated with Codegen.
+
+<Frame caption="Call graph visualization for modal/modal-client/_Client">
+<iframe
+  width="100%"
+  height="500px"
+  scrolling="no"
+  src={`https://codegen.sh/embedded/graph?id=66e2e195-ceec-4935-876a-ed4cfc1731c7&zoom=0.5&targetNodeName=_Client`}
+  className="rounded-xl"
+  style={{
+    backgroundColor: "#15141b",
+  }}
+></iframe>
+</Frame>
+<Info>
+View source code on [modal/modal-client](https://github.com/modal-labs/modal-client/blob/cbac0d80dfd98588027ecd21850152776be3ab82/modal/client.py#L70). View codemod on [codegen.sh](https://www.codegen.sh/codemod/66e2e195-ceec-4935-876a-ed4cfc1731c7/public/diff)
+</Info>
 
 ## Get Started
 

docs/mint.json

@@ -82,9 +82,10 @@
 			"group": "Tutorials",
 			"pages": [
 				"tutorials/at-a-glance",
-				"tutorials/migrating-apis",
-				"tutorials/codebase-visualization",
+				"tutorials/build-code-agent",
 				"tutorials/training-data",
+				"tutorials/codebase-visualization",
+				"tutorials/migrating-apis",
 				"tutorials/organize-your-codebase",
 				"tutorials/modularity",
 				"tutorials/manage-feature-flags",

docs/tutorials/at-a-glance.mdx

@@ -10,6 +10,13 @@ Explore our tutorials to learn how to use Codegen for various code transformatio
 ## Featured Tutorials
 
 <CardGroup cols={2}>
+  <Card
+    title="Build a Code Agent"
+    icon="robot"
+    href="/tutorials/build-code-agent"
+  >
+    Create an intelligent code agent with Langchain and powerful, codegen-powered tools
+  </Card>
   <Card
     title="Visualize Your Codebase"
     icon="diagram-project"
@@ -19,18 +26,11 @@ Explore our tutorials to learn how to use Codegen for various code transformatio
   </Card>
   <Card
     title="Mine Training Data"
-    icon="robot"
+    icon="database"
     href="/tutorials/training-data"
   >
     Create high-quality training data for LLM pre-training similar to word2vec or node2vec
   </Card>
-  <Card
-    title="Manage Feature Flags"
-    icon="flag"
-    href="/tutorials/manage-feature-flags"
-  >
-    Add, remove, and update feature flags across your application.
-  </Card>
   <Card
     title="Delete Dead Code"
     icon="broom"

docs/tutorials/build-code-agent.mdx

@@ -0,0 +1,169 @@
+---
+title: "Building a Code Agent with LangChain"
+sidebarTitle: "Code Agent"
+icon: "robot"
+iconType: "solid"
+---
+
+This guide demonstrates how to build an intelligent code agent that can analyze and manipulate codebases using Codegen's LangChain integration. 
+
+This agent access to powerful code viewing and manipulation tools powered by Codegen, including:
+- `RevealSymbolTool`: reveal all N-th degree dependencies and usages of a function
+- `MoveSymbolTool`: move a symbol between files, updating all imports etc. (guaranteed correctness)
+- `SemanticEditTool`: implementation of Cursor-style smart file editing
+- `SemanticSearchTool`: search over an index of vector embeddings for files
+
+<Info>View the full code in our [examples repository](https://github.com/codegen-sh/codegen-sdk/tree/develop/src/codegen/extensions/langchain)</Info>
+
+## Step 1: Setting Up the Agent
+
+First, let's import the necessary components and create our agent:
+
+```python
+from langchain_openai import ChatOpenAI
+from codegen import Codebase
+from codegen.extensions.langchain import create_codebase_agent
+
+# Initialize codebase
+codebase = Codebase.from_repo("fastapi/fastapi")
+
+# Create the agent with GPT-4
+agent = create_codebase_agent(
+    codebase=codebase,
+    model_name="gpt-4",
+    temperature=0,
+    verbose=True
+)
+```
+
+The agent is initialized with:
+- A Codebase instance to operate on
+- An LLM (GPT-4 in this case)
+- Tools for code manipulation
+- A conversation memory to maintain context
+
+## Step 2: Available Tools
+
+The agent comes with several built-in tools for code operations:
+
+```python
+tools = [
+    ViewFileTool(codebase),      # View file contents
+    ListDirectoryTool(codebase),  # List directory contents
+    SearchTool(codebase),        # Search code
+    EditFileTool(codebase),      # Edit files
+    CreateFileTool(codebase),    # Create new files
+    DeleteFileTool(codebase),    # Delete files
+    RenameFileTool(codebase),    # Rename files
+    MoveSymbolTool(codebase),    # Move functions/classes
+    RevealSymbolTool(codebase),  # Analyze symbol relationships
+    SemanticEditTool(codebase),  # Make semantic edits
+    CommitTool(codebase),        # Commit changes
+]
+```
+
+Each tool provides specific capabilities to the agent, allowing it to perform complex code operations.
+
+## Step 3: Interacting with the Agent
+
+Let's see some examples of how to interact with the agent:
+
+```python
+# Analyze dependencies
+result = agent.invoke(
+    {
+        "input": "What are the dependencies of the FastAPI class?",
+        "config": {"configurable": {"session_id": "demo"}}
+    }
+)
+print(result["output"])
+
+# Find usage patterns
+result = agent.invoke(
+    {
+        "input": "Show me examples of dependency injection in the codebase",
+        "config": {"configurable": {"session_id": "demo"}}
+    }
+)
+print(result["output"])
+
+# Perform code analysis
+result = agent.invoke(
+    {
+        "input": "What's the most complex function in terms of dependencies?",
+        "config": {"configurable": {"session_id": "demo"}}
+    }
+)
+print(result["output"])
+```
+
+The agent maintains conversation history, so it can reference previous queries and build context over time.
+
+## Step 4: Code Manipulation
+
+The agent can also perform code changes:
+
+```python
+# Move a function to a new file
+result = agent.invoke(
+    {
+        "input": "Move the validate_email function to validation_utils.py",
+        "config": {"configurable": {"session_id": "demo"}}
+    }
+)
+
+# Rename a class and update all references
+result = agent.invoke(
+    {
+        "input": "Rename the UserModel class to User and update all imports",
+        "config": {"configurable": {"session_id": "demo"}}
+    }
+)
+
+# Add error handling
+result = agent.invoke(
+    {
+        "input": "Add proper error handling to the process_data function",
+        "config": {"configurable": {"session_id": "demo"}}
+    }
+)
+```
+
+The agent will:
+1. Analyze the current code state
+2. Plan the necessary changes
+3. Execute the changes while maintaining code correctness
+4. Update all related imports and references
+
+## Advanced Usage
+
+### Adding Custom Tools
+
+You can extend the agent with custom tools:
+
+```python
+from langchain.tools import BaseTool
+from pydantic import BaseModel, Field
+
+class CustomToolInput(BaseModel):
+    """Input schema for custom tool."""
+    param: str = Field(..., description="Parameter description")
+
+class CustomCodeTool(BaseTool):
+    """A custom tool for the code agent."""
+    name = "custom_tool"
+    description = "Description of what the tool does"
+    args_schema = CustomToolInput
+
+    def _run(self, param: str) -> str:
+        # Tool implementation
+        return f"Processed {param}"
+
+# Add custom tool to agent
+tools.append(CustomCodeTool())
+agent = create_codebase_agent(
+    codebase=codebase,
+    tools=tools,
+    model_name="gpt-4"
+)
+```

src/codegen/extensions/langchain/tools.py

@@ -33,9 +33,9 @@
 class ViewFileTool(BaseTool):
     """Tool for viewing file contents and metadata."""
 
     name: ClassVar[str] = "view_file"
     description: ClassVar[str] = "View the contents and metadata of a file in the codebase"
     args_schema: ClassVar[type[BaseModel]] = ViewFileInput
     codebase: Codebase = Field(exclude=True)
 
     def __init__(self, codebase: Codebase) -> None:
@@ -56,9 +56,9 @@
 class ListDirectoryTool(BaseTool):
     """Tool for listing directory contents."""
 
     name: ClassVar[str] = "list_directory"
     description: ClassVar[str] = "List contents of a directory in the codebase"
     args_schema: ClassVar[type[BaseModel]] = ListDirectoryInput
     codebase: Codebase = Field(exclude=True)
 
     def __init__(self, codebase: Codebase) -> None:
@@ -79,9 +79,9 @@
 class SearchTool(BaseTool):
     """Tool for searching the codebase."""
 
     name: ClassVar[str] = "search"
     description: ClassVar[str] = "Search the codebase using text search"
     args_schema: ClassVar[type[BaseModel]] = SearchInput
     codebase: Codebase = Field(exclude=True)
 
     def __init__(self, codebase: Codebase) -> None:
@@ -102,7 +102,7 @@
 class EditFileTool(BaseTool):
     """Tool for editing files."""
 
     name: ClassVar[str] = "edit_file"
     description: ClassVar[str] = "Edit a file by replacing its entire content"
     args_schema: ClassVar[type[BaseModel]] = EditFileInput
     codebase: Codebase = Field(exclude=True)
@@ -205,15 +205,7 @@
         collect_usages: bool = True,
     ) -> str:
         # Find the symbol first
-        found_symbol = None
-        for file in self.codebase.files:
-            for symbol in file.symbols:
-                if symbol.name == symbol_name:
-                    found_symbol = symbol
-                    break
-            if found_symbol:
-                break
-
+        found_symbol = self.codebase.get_symbol(symbol_name)
         result = reveal_symbol(
             found_symbol,
             degree,