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");
}