[FEATURE]: Add support for embedding models in OpenRouter (#1359)

* Add support for embedding models in OpenRouter

* Update doc for OpenRouter embedding

* Run cargo fmt

Author: prrao87

docs/docs/ai/llm.mdx

@@ -26,7 +26,7 @@ We support the following types of LLM APIs:
 | [Anthropic](#anthropic) | `LlmApiType.ANTHROPIC` | ✅ | ❌ |
 | [Voyage](#voyage) | `LlmApiType.VOYAGE` | ❌ | ✅ |
 | [LiteLLM](#litellm) | `LlmApiType.LITE_LLM` | ✅ | ❌ |
-| [OpenRouter](#openrouter) | `LlmApiType.OPEN_ROUTER` | ✅ | ❌ |
+| [OpenRouter](#openrouter) | `LlmApiType.OPEN_ROUTER` | ✅ | ✅ |
 | [vLLM](#vllm) | `LlmApiType.VLLM` | ✅ | ❌ |
 | [Bedrock](#bedrock) | `LlmApiType.BEDROCK` | ✅ | ❌ |
 
@@ -400,7 +400,7 @@ You can find the full list of models supported by LiteLLM [here](https://docs.li
 To use the OpenRouter API, you need to set the environment variable `OPENROUTER_API_KEY`.
 You can generate the API key from [here](https://openrouter.ai/settings/keys).
 
-A spec for OpenRouter looks like this:
+A text generation spec for OpenRouter looks like this:
 
 <Tabs>
 <TabItem value="python" label="Python" default>
@@ -415,6 +415,27 @@ cocoindex.LlmSpec(
 </TabItem>
 </Tabs>
 
+OpenRouter also supports some text embedding models. Note that for OpenRouter embedding
+models, you need to explicitly provide the `output_dimension` parameter in the spec.
+Here's how you can define the spec to use an OpenRouter embedding model:
+
+<Tabs>
+<TabItem value="python" label="Python" default>
+
+```python
+cocoindex.functions.EmbedText(
+    api_type=cocoindex.LlmApiType.OPEN_ROUTER,
+    model="openai/text-embedding-3-small",
+    # Task type for embedding model
+    task_type="SEMANTICS_SIMILARITY",
+    # Required: the number of output dimensions for the embedding model
+    output_dimension=1536,
+)
+```
+
+</TabItem>
+</Tabs>
+
 You can find the full list of models supported by OpenRouter [here](https://openrouter.ai/models).
 
 ### vLLM

rust/cocoindex/src/llm/mod.rs

@@ -166,6 +166,10 @@ pub async fn new_llm_embedding_client(
         LlmApiType::Ollama => {
             Box::new(ollama::Client::new(address).await?) as Box<dyn LlmEmbeddingClient>
         }
+        LlmApiType::OpenRouter => {
+            Box::new(openrouter::Client::new_openrouter(address, api_key).await?)
+                as Box<dyn LlmEmbeddingClient>
+        }
         LlmApiType::Gemini => {
             Box::new(gemini::AiStudioClient::new(address, api_key)?) as Box<dyn LlmEmbeddingClient>
         }
@@ -178,11 +182,7 @@ pub async fn new_llm_embedding_client(
             Box::new(gemini::VertexAiClient::new(address, api_key, api_config).await?)
                 as Box<dyn LlmEmbeddingClient>
         }
-        LlmApiType::OpenRouter
-        | LlmApiType::LiteLlm
-        | LlmApiType::Vllm
-        | LlmApiType::Anthropic
-        | LlmApiType::Bedrock => {
+        LlmApiType::LiteLlm | LlmApiType::Vllm | LlmApiType::Anthropic | LlmApiType::Bedrock => {
             api_bail!("Embedding is not supported for API type {:?}", api_type)
         }
     };