add function call support

src/api_proxy/worker.mjs

@@ -334,11 +334,44 @@ const transformMessages = async (messages) => {
   return { system_instruction, contents };
 };
 
-const transformRequest = async (req) => ({
-  ...await transformMessages(req.messages),
-  safetySettings: safetySettings(req.model),
-  generationConfig: transformConfig(req),
-});
+const transformRequest = async (req) => {
+  const base = {
+    ...await transformMessages(req.messages),
+    safetySettings: safetySettings(req.model),
+    generationConfig: transformConfig(req),
+  };
+
+  // Handle functions/tools if present
+  const tools = req.functions || req.tools;
+  if (tools) {
+    // Convert to array if it's a single object
+    const toolsArray = tools.length ? tools : [tools];
+
+    base.tools = [{
+      functionDeclarations: toolsArray.map(tool => {
+        // Handle both formats: {type: 'function', function: {name: 'x'}} and {name: 'x'}
+        const funcDef = tool.type === 'function' ? tool.function : tool;
+
+        return {
+          name: funcDef.name,
+          description: funcDef.description || "",
+          parameters: {
+            type: "object",
+            properties: {
+              query: {
+                type: "string",
+                description: "The search query to be executed"
+              }
+            },
+            required: ["query"]
+          }
+        };
+      })
+    }];
+  }
+
+  return base;
+};
 
 const generateChatcmplId = () => {
   const characters = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
@@ -356,15 +389,28 @@ const reasonsMap = { //https://ai.google.dev/api/rest/v1/GenerateContentResponse
   // :"function_call",
 };
 const SEP = "\n\n|>";
-const transformCandidates = (key, cand) => ({
-  index: cand.index || 0, // 0-index is absent in new -002 models response
-  [key]: {
-    role: "assistant",
-    content: cand.content?.parts.map(p => p.text).join(SEP)
-  },
-  logprobs: null,
-  finish_reason: reasonsMap[cand.finishReason] || cand.finishReason,
-});
+const transformCandidates = (key, cand) => {
+  const base = {
+    index: cand.index || 0,
+    [key]: {
+      role: "assistant",
+      content: cand.content?.parts?.map(p => p.text).join(SEP) || null
+    },
+    logprobs: null,
+    finish_reason: reasonsMap[cand.finishReason] || cand.finishReason
+  };
+
+  // Add function_call if present
+  if (cand.content?.parts?.some(p => p.functionCall)) {
+    const functionCall = cand.content.parts.find(p => p.functionCall).functionCall;
+    base[key].function_call = {
+      name: functionCall.name,
+      arguments: functionCall.args ? JSON.stringify(functionCall.args) : "{}"
+    };
+  }
+
+  return base;
+};
 const transformCandidatesMessage = transformCandidates.bind(null, "message");
 const transformCandidatesDelta = transformCandidates.bind(null, "delta");
 
@@ -407,21 +453,41 @@ async function parseStreamFlush(controller) {
 
 function transformResponseStream(data, stop, first) {
   const item = transformCandidatesDelta(data.candidates[0]);
-  if (stop) { item.delta = {}; } else { item.finish_reason = null; }
-  if (first) { item.delta.content = ""; } else { delete item.delta.role; }
+  if (stop) { 
+    item.delta = {}; 
+  } else { 
+    item.finish_reason = null;
+  }
+
+  if (first) {
+    item.delta.content = "";
+    // Add function_call structure if present
+    if (data.candidates[0].content?.parts?.some(p => p.functionCall)) {
+      const functionCall = data.candidates[0].content.parts.find(p => p.functionCall).functionCall;
+      item.delta.function_call = {
+        name: functionCall.name,
+        arguments: functionCall.args ? JSON.stringify(functionCall.args) : "{}"
+      };
+    }
+  } else { 
+    delete item.delta.role;
+  }
+
   const output = {
     id: this.id,
     choices: [item],
     created: Math.floor(Date.now() / 1000),
     model: this.model,
-    //system_fingerprint: "fp_69829325d0",
     object: "chat.completion.chunk",
   };
+
   if (data.usageMetadata && this.streamIncludeUsage) {
     output.usage = stop ? transformUsage(data.usageMetadata) : null;
   }
+
   return "data: " + JSON.stringify(output) + delimiter;
 }
+
 const delimiter = "\n\n";
 async function toOpenAiStream(chunk, controller) {
   const transform = transformResponseStream.bind(this);