feat: add support for custom embedding providers

Add flexible embedding provider configuration to support both OpenAI
and custom embedding endpoints (e.g., LiteLLM, local models). This
enables users to use alternative embedding services while maintaining
backward compatibility with OpenAI.

Author: alpha-er

README.md

@@ -68,9 +68,21 @@ Configuration is managed through two files:
     ```dotenv
     # .env
 
-    # Required: Your OpenAI API Key
+    # Required: Your OpenAI API Key (used for both OpenAI and custom providers)
     OPENAI_API_KEY="sk-..."
 
+    # Optional: Embedding provider (defaults to "openai")
+    PROVIDER="openai"  # or "custom"
+
+    # Optional: Custom embedding model (defaults based on provider)
+    EMBEDDING_MODEL="text-embedding-3-large"  # or your preferred model
+
+    # Required if using custom provider: Custom endpoint URL
+    CUSTOM_ENDPOINT="http://localhost:8000/v1/embeddings"
+
+    # Optional: Vector size of custom embedding model
+    EMBEDDING_VECTOR_SIZE=1024
+
     # Required for GitHub sources
     GITHUB_PERSONAL_ACCESS_TOKEN="ghp_..."
 
@@ -84,27 +96,32 @@ Configuration is managed through two files:
 2.  **`config.yaml` file:**
     This file defines the sources to process and how to handle them. Create a `config.yaml` file (or use a different name and pass it as an argument).
 
+    **Embedding Provider Configuration:**
+
+    Embedding providers are now configured via environment variables:
+    - `OPENAI_API_KEY`: API key used for both providers
+    - `PROVIDER`: Set to "openai" (default) or "custom"
+    - `EMBEDDING_MODEL`: Model to use (default: "text-embedding-3-large")
+    - `EMBEDDING_VECTOR_SIZE`: Vector size of the custom embedding model (default: 3072)
+    - `CUSTOM_ENDPOINT`: Required when using custom provider (e.g., "http://localhost:8000/v1/embeddings")
+
     **Structure:**
 
     *   `sources`: An array of source configurations.
         *   `type`: Either `'website'`, `'github'`, `'local_directory'`, or `'zendesk'`
-        
         For websites (`type: 'website'`):
         *   `url`: The starting URL for crawling the documentation site.
         *   `sitemap_url`: (Optional) URL to the site's XML sitemap for discovering additional pages not linked in navigation.
-        
         For GitHub repositories (`type: 'github'`):
         *   `repo`: Repository name in the format `'owner/repo'` (e.g., `'istio/istio'`).
         *   `start_date`: (Optional) Starting date to fetch issues from (e.g., `'2025-01-01'`).
-        
         For local directories (`type: 'local_directory'`):
         *   `path`: Path to the local directory to process.
         *   `include_extensions`: (Optional) Array of file extensions to include (e.g., `['.md', '.txt', '.pdf']`). Defaults to `['.md', '.txt', '.html', '.htm', '.pdf']`.
         *   `exclude_extensions`: (Optional) Array of file extensions to exclude.
         *   `recursive`: (Optional) Whether to traverse subdirectories (defaults to `true`).
         *   `url_rewrite_prefix` (Optional) URL prefix to rewrite `file://` URLs (e.g., `https://mydomain.com`)
         *   `encoding`: (Optional) File encoding to use (defaults to `'utf8'`). Note: PDF files are processed as binary and this setting doesn't apply to them.
-        
         For Zendesk (`type: 'zendesk'`):
         *   `zendesk_subdomain`: Your Zendesk subdomain (e.g., `'mycompany'` for mycompany.zendesk.com).
         *   `email`: Your Zendesk admin email address.
@@ -131,6 +148,21 @@ Configuration is managed through two files:
 
     **Example (`config.yaml`):**
     ```yaml
+    # Example with OpenAI embedding provider (default)
+    embedding_config:
+      provider: "openai"
+      openai:
+        api_key_env: "OPENAI_API_KEY"
+
+    # Example with custom embedding provider (LiteLLM)
+    # embedding_config:
+    #   provider: "custom"
+    #   custom:
+    #     endpoint: "http://localhost:8000/v1/embeddings"
+    #     model: "text-embedding-ada-002"
+    #     api_key_env: "LITELLM_API_KEY"
+    #     timeout: 30000
+
     sources:
       # Website source example
       - type: 'website'
@@ -155,7 +187,6 @@ Configuration is managed through two files:
           type: 'sqlite'
           params:
             db_path: './istio-issues.db'
-      
       # Local directory source example
       - type: 'local_directory'
         product_name: 'project-docs'
@@ -168,7 +199,6 @@ Configuration is managed through two files:
           type: 'sqlite'
           params:
             db_path: './project-docs.db'
-      
       # Zendesk example
       - type: 'zendesk'
         product_name: 'MyCompany'
@@ -186,7 +216,6 @@ Configuration is managed through two files:
           type: 'sqlite'
           params:
             db_path: './zendesk-kb.db'
-      
       # Qdrant example
       - type: 'website'
         product_name: 'Istio'