refactor(subagent): split extension into modules

src/prompts.ts

@@ -0,0 +1,73 @@
+import * as fs from "node:fs";
+import * as path from "node:path";
+import { parseFrontmatter } from "@mariozechner/pi-coding-agent";
+import { FINALIZE_TOOL_NAME, PROMPTS_DIR } from "./constants.ts";
+import type { PromptConfig } from "./types.ts";
+import { FinalizeStatus } from "./types.ts";
+
+// Parse Tool List - Frontmatter may use YAML arrays or comma-delimited strings.
+export function parseToolList(value: unknown): string[] {
+  if (!value) return [];
+  if (Array.isArray(value)) {
+    return value
+      .map(String)
+      .map((tool) => tool.trim())
+      .filter(Boolean);
+  }
+  if (typeof value === "string") {
+    return value
+      .split(",")
+      .map((tool) => tool.trim())
+      .filter(Boolean);
+  }
+  return [];
+}
+
+// Discover Prompts - Load prompt markdown files from this extension's prompts dir.
+export function discoverPrompts(): PromptConfig[] {
+  if (!fs.existsSync(PROMPTS_DIR)) return [];
+
+  const prompts: PromptConfig[] = [];
+  const entries = fs.readdirSync(PROMPTS_DIR, { withFileTypes: true });
+  for (const entry of entries) {
+    if (!entry.name.endsWith(".md")) continue;
+    if (!entry.isFile() && !entry.isSymbolicLink()) continue;
+
+    const filePath = path.join(PROMPTS_DIR, entry.name);
+    const content = fs.readFileSync(filePath, "utf-8");
+    const { frontmatter, body } =
+      parseFrontmatter<Record<string, unknown>>(content);
+
+    if (
+      typeof frontmatter.name !== "string" ||
+      typeof frontmatter.description !== "string"
+    ) {
+      continue;
+    }
+
+    prompts.push({
+      name: frontmatter.name,
+      description: frontmatter.description,
+      approvedTools: parseToolList(
+        frontmatter.approved_tools ?? frontmatter.allowed_tools,
+      ),
+      deniedTools: parseToolList(frontmatter.denied_tools),
+      systemPrompt: body.trim(),
+      filePath,
+    });
+  }
+
+  return prompts.sort((a, b) => a.name.localeCompare(b.name));
+}
+
+// Build Finalize Prompt - Child agents must terminate by calling this tool.
+export function buildSubagentPrompt(agent: PromptConfig): string {
+  const finalizePrompt = [
+    "You are running as a subagent.",
+    `When the task is complete, call ${FINALIZE_TOOL_NAME} as your final action.`,
+    "Do not provide the final answer as normal assistant text.",
+    `${FINALIZE_TOOL_NAME} requires status ${FinalizeStatus.SUCCESS} with result, or status ${FinalizeStatus.ERROR} with error and optional result.`,
+  ].join("\n");
+
+  return [agent.systemPrompt, finalizePrompt].filter(Boolean).join("\n\n");
+}