feat(memory): implement str_replace command

nanobot/agent/tools/anthropic/memory.py

@@ -367,10 +367,55 @@ class MemoryTool20250818(BaseAnthropicTool):
         )
 
     async def _str_replace(
-        self, path: str | None, old_str: str | None, new_str: str | None
+        self,
+        path: str | None,
+        old_str: str | None,
+        new_str: str | None,
     ) -> CLIResult:
-        """Placeholder for str_replace command."""
-        return CLIResult(exit_code=1, output="", error="Not implemented yet")
+        """Replace unique occurrence of old_str with new_str."""
+        if path is None or old_str is None or new_str is None:
+            return CLIResult(
+                exit_code=1,
+                output="",
+                error="Error: old_str and new_str are required for str_replace command"
+            )
+
+        path_str = path
+        validated_path = self._validate_memory_path(path)
+
+        if not validated_path.exists() or validated_path.is_dir():
+            return CLIResult(
+                exit_code=1,
+                output="",
+                error=f"Error: The path {path_str} does not exist. Please provide a valid path."
+            )
+
+        content = validated_path.read_text()
+        count = content.count(old_str)
+
+        if count == 0:
+            return CLIResult(
+                exit_code=1,
+                output="",
+                error=f"No replacement was performed, old_str `{old_str}` did not appear verbatim in {path_str}."
+            )
+        elif count > 1:
+            lines = content.splitlines()
+            line_nums = [i + 1 for i, line in enumerate(lines) if old_str in line]
+            return CLIResult(
+                exit_code=1,
+                output="",
+                error=f"No replacement was performed. Multiple occurrences of old_str `{old_str}` in lines: {line_nums}. Please ensure it is unique"
+            )
+
+        new_content = content.replace(old_str, new_str, 1)
+        validated_path.write_text(new_content)
+
+        return CLIResult(
+            exit_code=0,
+            output="The memory file has been edited.",
+            error=""
+        )
 
     async def _insert(
         self, path: str | None, insert_line: int | None, insert_text: str | None

tests/test_memory_tool.py

@@ -179,3 +179,61 @@ async def test_create_file_missing_text(memory_tool):
     assert result.exit_code == 1
     assert result.output == ""
     assert "Error: file_text is required for create command" in result.error
+
+
+@pytest.mark.asyncio
+async def test_str_replace_success(memory_tool, temp_workspace):
+    """Test replacing unique string in a file."""
+    test_file = temp_workspace / "memories" / "config.txt"
+    test_file.write_text("color: blue\nsize: large\n")
+
+    result = await memory_tool(
+        command="str_replace",
+        path="/memories/config.txt",
+        old_str="blue",
+        new_str="green"
+    )
+
+    assert result.exit_code == 0
+    assert result.error == ""
+    assert "The memory file has been edited." in result.output
+
+    # Verify file was modified
+    assert test_file.read_text() == "color: green\nsize: large\n"
+
+
+@pytest.mark.asyncio
+async def test_str_replace_not_found(memory_tool, temp_workspace):
+    """Test replacing string that doesn't exist."""
+    test_file = temp_workspace / "memories" / "config.txt"
+    test_file.write_text("color: blue\n")
+
+    result = await memory_tool(
+        command="str_replace",
+        path="/memories/config.txt",
+        old_str="red",
+        new_str="green"
+    )
+
+    assert result.exit_code == 1
+    assert result.output == ""
+    assert "No replacement was performed, old_str `red` did not appear verbatim" in result.error
+
+
+@pytest.mark.asyncio
+async def test_str_replace_duplicate(memory_tool, temp_workspace):
+    """Test replacing string that appears multiple times."""
+    test_file = temp_workspace / "memories" / "config.txt"
+    test_file.write_text("color: blue\nbackground: blue\n")
+
+    result = await memory_tool(
+        command="str_replace",
+        path="/memories/config.txt",
+        old_str="blue",
+        new_str="green"
+    )
+
+    assert result.exit_code == 1
+    assert result.output == ""
+    assert "Multiple occurrences of old_str `blue`" in result.error
+    assert "Please ensure it is unique" in result.error