import type { Context } from "@earendil-works/chord";
import { getOrThrow } from "@earendil-works/pi-durable/env";
import { posix, win32 } from "node:path";
import type { Environment } from "@berry/api/environment.ts";

export async function folders(
  env: Environment,
  prefix: string,
  context: Context,
): Promise<string[]> {
  if (prefix.includes("\0")) throw new Error("Invalid directory prefix");
  const paths = env.platform === "win32" ? win32 : posix;
  const expanded = prefix === "~" || /^~[/\\]/u.test(prefix) ? env.home + prefix.slice(1) : prefix;
  const trailing = expanded === "" ||
    (env.platform === "win32" ? /[/\\]$/u : /\/$/u).test(expanded);
  const parent = trailing ? expanded || "." : paths.dirname(expanded);
  const query = trailing ? "" : paths.basename(expanded);
  const absolute = getOrThrow(await env.absolutePath(parent, context));
  const entries = getOrThrow(await env.listDir(absolute, context));
  const matches = [];
  for (const entry of entries.sort((a, b) => a.name.localeCompare(b.name))) {
    const matchesPrefix = env.platform === "win32"
      ? entry.name.toLowerCase().startsWith(query.toLowerCase())
      : entry.name.startsWith(query);
    if (!matchesPrefix || (entry.kind !== "directory" && entry.kind !== "symlink")) continue;
    if (entry.kind === "symlink") {
      const canonical = await env.canonicalPath(entry.path, context);
      if (!canonical.ok) continue;
      const info = await env.fileInfo(canonical.value, context);
      if (!info.ok || info.value.kind !== "directory") continue;
    }
    matches.push(paths.join(parent === "." ? "" : parent, entry.name) + paths.sep);
    if (matches.length === 50) break;
  }
  return matches;
}