Agents: add pluggable CLIs

Co-authored-by: RealSid08 <RealSid08@users.noreply.github.com>

src/agents/pi.ts

@@ -0,0 +1,65 @@
+import path from "node:path";
+
+import type { AgentMeta, AgentParseResult, AgentSpec, BuildArgsContext } from "./types.js";
+
+type PiAssistantMessage = {
+  role?: string;
+  content?: Array<{ type?: string; text?: string }>;
+  usage?: { input?: number; output?: number };
+  model?: string;
+  provider?: string;
+  stopReason?: string;
+};
+
+function parsePiJson(raw: string): AgentParseResult {
+  const lines = raw.split(/\n+/).filter((l) => l.trim().startsWith("{"));
+  let lastMessage: PiAssistantMessage | undefined;
+  for (const line of lines) {
+    try {
+      const ev = JSON.parse(line) as { type?: string; message?: PiAssistantMessage };
+      if (ev.type === "message_end" && ev.message?.role === "assistant") {
+        lastMessage = ev.message;
+      }
+    } catch {
+      // ignore
+    }
+  }
+  const text =
+    lastMessage?.content
+      ?.filter((c) => c?.type === "text" && typeof c.text === "string")
+      .map((c) => c.text)
+      .join("\n")
+      ?.trim() ?? undefined;
+  const meta: AgentMeta | undefined = lastMessage
+    ? {
+        model: lastMessage.model,
+        provider: lastMessage.provider,
+        stopReason: lastMessage.stopReason,
+        usage: lastMessage.usage,
+      }
+    : undefined;
+  return { text, meta };
+}
+
+export const piSpec: AgentSpec = {
+  kind: "pi",
+  isInvocation: (argv) => argv.length > 0 && path.basename(argv[0]) === "pi",
+  buildArgs: (ctx) => {
+    const argv = [...ctx.argv];
+    // Non-interactive print + JSON
+    if (!argv.includes("-p") && !argv.includes("--print")) {
+      argv.splice(argv.length - 1, 0, "-p");
+    }
+    if (ctx.format === "json" && !argv.includes("--mode") && !argv.some((a) => a === "--mode")) {
+      argv.splice(argv.length - 1, 0, "--mode", "json");
+    }
+    // Session defaults
+    // Identity prefix optional; Pi usually doesn't need, but allow
+    if (!(ctx.sendSystemOnce && ctx.systemSent) && argv[ctx.bodyIndex]) {
+      const existingBody = argv[ctx.bodyIndex];
+      argv[ctx.bodyIndex] = [ctx.identityPrefix, existingBody].filter(Boolean).join("\n\n");
+    }
+    return argv;
+  },
+  parseOutput: parsePiJson,
+};