/**
 * Skills loader.
 *
 * Skills are filesystem-resident markdown files. The convention is:
 *
 *   <skillsDir>/
 *     paperclip-forecast/SKILL.md
 *     paperclip-routines/SKILL.md
 *     <anything>/SKILL.md
 *
 * Each SKILL.md starts with a YAML frontmatter:
 *
 *   ---
 *   name: Paperclip Forecasting
 *   description: How to run and interpret a forecast.
 *   ---
 *   # body in markdown...
 *
 * The model receives the parsed body as part of the system prompt.
 */
import fs from "node:fs";
import path from "node:path";
import type { SkillDoc } from "./types.js";

export function loadSkills(workspacePath: string | undefined, explicitDir?: string): SkillDoc[] {
  const dirs: string[] = [];
  if (explicitDir && explicitDir.trim().length > 0) {
    dirs.push(explicitDir);
  }
  if (workspacePath) {
    dirs.push(path.join(workspacePath, "skills"));
    dirs.push(path.join(workspacePath, ".paperclip", "skills"));
  }
  // Fall back to the adapter's bundled default skills.
  dirs.push(path.join(import.meta.dirname, "..", "skills"));

  const out: SkillDoc[] = [];
  for (const dir of dirs) {
    try {
      if (!fs.existsSync(dir) || !fs.statSync(dir).isDirectory()) continue;
      for (const entry of fs.readdirSync(dir, { withFileTypes: true })) {
        if (!entry.isDirectory()) continue;
        const skillFile = path.join(dir, entry.name, "SKILL.md");
        if (!fs.existsSync(skillFile)) continue;
        const raw = fs.readFileSync(skillFile, "utf8");
        const parsed = parseFrontmatter(raw);
        if (parsed) {
          out.push({
            name: parsed.name || entry.name,
            description: parsed.description || "",
            body: parsed.body,
            path: skillFile,
          });
        }
      }
    } catch {
      // Best effort — never let a bad skills dir kill the heartbeat.
    }
  }
  return out;
}

interface Frontmatter {
  name?: string;
  description?: string;
  body: string;
}

function parseFrontmatter(raw: string): Frontmatter | null {
  if (!raw.startsWith("---")) {
    return { body: raw };
  }
  const end = raw.indexOf("\n---", 3);
  if (end < 0) {
    return { body: raw };
  }
  const fm = raw.slice(3, end).trim();
  const body = raw.slice(end + 4).trim();
  const out: Frontmatter = { body };
  for (const line of fm.split(/\r?\n/)) {
    const m = line.match(/^([A-Za-z0-9_-]+):\s*(.*)$/);
    if (!m) continue;
    const [, key, valueRaw] = m;
    const value = valueRaw.replace(/^["']|["']$/g, "").trim();
    if (key === "name") out.name = value;
    if (key === "description") out.description = value;
  }
  return out;
}