Add /v1/models endpoint to mlx_lm.server (#984)

* Add 'models' endpoint to server

* Add test for new 'models' server endpoint

* Check hf_cache for mlx models

* update tests to check hf_cache for models

* simplify test

* doc

---------

Co-authored-by: Awni Hannun <awni@apple.com>

llms/mlx_lm/SERVER.md

@@ -85,3 +85,17 @@ curl localhost:8080/v1/chat/completions \
 
 - `adapters`: (Optional) A string path to low-rank adapters. The path must be
   rlative to the directory the server was started in.
+
+### List Models
+
+Use the `v1/models` endpoint to list available models:
+
+```shell
+curl localhost:8080/v1/models -H "Content-Type: application/json"
+```
+
+This will return a list of locally available models where each model in the
+list contains the following fields:
+
+- `"id"`: The Hugging Face repo id.
+- `"created"`: A timestamp representing the model creation time.

llms/mlx_lm/server.py

@@ -11,6 +11,7 @@ from pathlib import Path
 from typing import Dict, List, Literal, NamedTuple, Optional, Sequence, Union
 
 import mlx.core as mx
+from huggingface_hub import scan_cache_dir
 
 from .utils import generate_step, load
 
@@ -618,6 +619,46 @@ class APIHandler(BaseHTTPRequestHandler):
         prompt = self.tokenizer.encode(prompt_text)
         return mx.array(prompt)
 
+    def do_GET(self):
+        """
+        Respond to a GET request from a client.
+        """
+        if self.path == "/v1/models":
+            self.handle_models_request()
+        else:
+            self._set_completion_headers(404)
+            self.end_headers()
+            self.wfile.write(b"Not Found")
+
+    def handle_models_request(self):
+        """
+        Handle a GET request for the /v1/models endpoint.
+        """
+        self._set_completion_headers(200)
+        self.end_headers()
+
+        # Scan the cache directory for downloaded mlx models
+        hf_cache_info = scan_cache_dir()
+        downloaded_models = [
+            repo for repo in hf_cache_info.repos if "mlx" in repo.repo_id
+        ]
+
+        # Create a list of available models
+        models = [
+            {
+                "id": repo.repo_id,
+                "object": "model",
+                "created": self.created,
+            }
+            for repo in downloaded_models
+        ]
+
+        response = {"object": "list", "data": models}
+
+        response_json = json.dumps(response).encode()
+        self.wfile.write(response_json)
+        self.wfile.flush()
+
 
 def run(
     host: str,