feat: add Gemini-powered agent for policy-aware payment intent generation

- Implement off-chain agent using Gemini API
- Agent reasons over policy constraints and user intent
- Outputs structured PaymentIntent for on-chain execution
- Preserves model: AI proposes, contracts enforce

Author: tr-Kalyan

.gitignore

@@ -1,16 +1,23 @@
 # Compiler files
+node_modules/
+lib/
+cache/
+out/
+dist/
 cache/
 out/
 
 # Ignores development broadcast logs
-!/broadcast
-/broadcast/*/31337/
-/broadcast/**/dry-run/
+broadcast/
+deployments/
 
 # Docs
 docs/
 
 # Dotenv file
 .env
-broadcast/
-deployments.json
+.env.*
+!.env.example
+
+# Misc
+.DS_Store

agent/agent.ts

@@ -0,0 +1,45 @@
+// import { GoogleGenerativeAI } from "@google/generative-ai";
+import { GoogleGenAI } from "@google/genai";
+import { PaymentIntentSchema, AgentInput } from "./schema";
+import { buildPrompt } from "./prompt";
+import "dotenv/config";
+
+export async function proposePayment(input: AgentInput) {
+    const genAI = new GoogleGenAI({ 
+        apiKey: process.env.GEMINI_API_KEY!,
+        apiVersion: 'v1'
+    });
+    const modelName = "gemini-2.5-flash-lite"; // Use 2.0 or 2.5 for stability
+
+    const result = await genAI.models.generateContent({
+        model: modelName,
+        contents: [{ role: "user", parts: [{ text: buildPrompt(input) }] }],
+        config: {
+            // We use 'as any' to tell TypeScript to stay out of the way.
+            // This allows us to send the snake_case name the API actually requires.
+            ["response_mime_type" as any]: "application/json" 
+        } as any
+    });
+
+    // FIX: Access .text() directly on the result
+    const text = result?.text;
+
+    // Check if the response is actually there
+    if (!text) {
+        throw new Error("Gemini returned an empty response. This might be due to safety filters.");
+    }
+
+    let parsed;
+    try {
+        const cleanJson = text.replace(/```json/g, "").replace(/```/g, "").trim();
+        parsed = JSON.parse(cleanJson);
+    } catch (e) {
+        throw new Error(`Gemini returned invalid JSON: ${text}`);
+    }
+
+    if (parsed.reject) {
+        throw new Error(`Agent rejected request: ${parsed.reason}`);
+    }
+
+    return PaymentIntentSchema.parse(parsed);
+}