Define Tool protocol and LLM provider abstraction

The implementation is complete. Here's a summary of the changes made:

1. **Updated LLM type** to include `llmExtraHeaders` field for
OpenRoute 2. **Changed `defaultLLM`** to use:
   - OpenRouter base URL: `https://openrouter.ai/api/v1` - Default
   model: `anthropic/claude-sonnet-4-20250514` - OpenRouter headers:
   `HTTP-Referer` and `X-Title`
3. **Updated `chatWithUsage`** to apply extra headers to HTTP requests
4. **Added `case-insensitive` dependency** for proper header handling
5. **Added tests** for OpenRouter configuration 6. **Fixed hlint
suggestions** (Use `</` instead of `<$>`, eta reduce)

Task-Id: t-141.1

1 files changed, 32 insertions, 8 deletions

diff --git a/Omni/Agent/Engine.hs b/Omni/Agent/Engine.hs
index 10b36b2..69edd36 100644
--- a/Omni/Agent/Engine.hs
+++ b/Omni/Agent/Engine.hs
@@ -12,6 +12,7 @@
 -- : out omni-agent-engine
 -- : dep http-conduit
 -- : dep aeson
+-- : dep case-insensitive
 module Omni.Agent.Engine
   ( Tool (..),
     LLM (..),
@@ -41,6 +42,7 @@ import Alpha
 import Data.Aeson ((.!=), (.:), (.:?), (.=))
 import qualified Data.Aeson as Aeson
 import qualified Data.ByteString.Lazy as BL
+import qualified Data.CaseInsensitive as CI
 import qualified Data.Map.Strict as Map
 import qualified Data.Text as Text
 import qualified Data.Text.Encoding as TE
@@ -72,7 +74,10 @@ test =
           Nothing -> Test.assertFailure "Failed to decode message"
           Just decoded -> msgContent msg Test.@=? msgContent decoded,
       Test.unit "defaultLLM has correct endpoint" <| do
-        llmBaseUrl defaultLLM Test.@=? "https://api.openai.com",
+        llmBaseUrl defaultLLM Test.@=? "https://openrouter.ai/api/v1",
+      Test.unit "defaultLLM has OpenRouter headers" <| do
+        length (llmExtraHeaders defaultLLM) Test.@=? 2
+        llmModel defaultLLM Test.@=? "anthropic/claude-sonnet-4-20250514",
       Test.unit "defaultAgentConfig has sensible defaults" <| do
         agentMaxIterations defaultAgentConfig Test.@=? 10,
       Test.unit "defaultEngineConfig has no-op callbacks" <| do
@@ -173,20 +178,37 @@ encodeToolForApi t =
 data LLM = LLM
   { llmBaseUrl :: Text,
     llmApiKey :: Text,
-    llmModel :: Text
+    llmModel :: Text,
+    llmExtraHeaders :: [(ByteString, ByteString)]
   }
   deriving (Show, Eq, Generic)
 
-instance Aeson.ToJSON LLM
+instance Aeson.ToJSON LLM where
+  toJSON l =
+    Aeson.object
+      [ "llmBaseUrl" .= llmBaseUrl l,
+        "llmApiKey" .= llmApiKey l,
+        "llmModel" .= llmModel l
+      ]
 
-instance Aeson.FromJSON LLM
+instance Aeson.FromJSON LLM where
+  parseJSON =
+    Aeson.withObject "LLM" <| \v ->
+      (LLM </ (v .: "llmBaseUrl"))
+        <*> (v .: "llmApiKey")
+        <*> (v .: "llmModel")
+        <*> pure []
 
 defaultLLM :: LLM
 defaultLLM =
   LLM
-    { llmBaseUrl = "https://api.openai.com",
+    { llmBaseUrl = "https://openrouter.ai/api/v1",
       llmApiKey = "",
-      llmModel = "gpt-4"
+      llmModel = "anthropic/claude-sonnet-4-20250514",
+      llmExtraHeaders =
+        [ ("HTTP-Referer", "https://omni.dev"),
+          ("X-Title", "Omni Agent")
+        ]
     }
 
 data AgentConfig = AgentConfig
@@ -397,7 +419,7 @@ data ChatResult = ChatResult
 
 chatWithUsage :: LLM -> [Tool] -> [Message] -> IO (Either Text ChatResult)
 chatWithUsage llm tools messages = do
-  let url = Text.unpack (llmBaseUrl llm) <> "/v1/chat/completions"
+  let url = Text.unpack (llmBaseUrl llm) <> "/chat/completions"
   req0 <- HTTP.parseRequest url
   let toolApis = [encodeToolForApi t | not (null tools), t <- tools]
       body =
@@ -406,12 +428,14 @@ chatWithUsage llm tools messages = do
             reqMessages = messages,
             reqTools = if null toolApis then Nothing else Just toolApis
           }
-      req =
+      baseReq =
         HTTP.setRequestMethod "POST"
           <| HTTP.setRequestHeader "Content-Type" ["application/json"]
           <| HTTP.setRequestHeader "Authorization" ["Bearer " <> TE.encodeUtf8 (llmApiKey llm)]
           <| HTTP.setRequestBodyLBS (Aeson.encode body)
           <| req0
+      req = foldr addHeader baseReq (llmExtraHeaders llm)
+      addHeader (name, value) = HTTP.addRequestHeader (CI.mk name) value
 
   response <- HTTP.httpLBS req
   let status = HTTP.getResponseStatusCode response