import fs from "node:fs";
import path from "node:path";

const TASK_ID = /^M\d+-GAP-\d{5}$/u;

function add(issues, code, detail) {
  issues.push({ code, detail });
}

/**
 * Validate the cheap, deterministic inputs before a generated-gap checker
 * loads the WASM module or starts Blender. This is intentionally independent
 * of the task-specific assertions in check-generated-gap.mjs.
 */
export function collectGeneratedGapPreflight({ root, task, entry }) {
  const issues = [];
  if (typeof task !== "string" || !TASK_ID.test(task)) {
    add(issues, "TASK_ARGUMENT_INVALID", "use --task Mxx-GAP-nnnnn");
    return issues;
  }
  if (!entry) {
    add(issues, "TASK_NOT_INDEXED", task);
    return issues;
  }
  if (!["active", "completed"].includes(entry.state)) {
    add(issues, "TASK_NOT_RUNNABLE", `${task} state=${entry.state}; expected active or completed`);
  }

  const required = [];
  if (entry.fixture?.path) required.push(["fixture", entry.fixture.path]);
  const generator = typeof entry.desktopCommand === "string"
    ? entry.desktopCommand.match(/\s--python\s+(\S+)/u)?.[1]
    : undefined;
  if (generator) required.push(["generator", generator]);
  for (const [role, relativePath] of required) {
    const resolved = path.resolve(root, relativePath);
    if (!fs.existsSync(resolved)) add(issues, "INPUT_MISSING", `${role}=${relativePath}`);
    else if (!fs.statSync(resolved).isFile()) add(issues, "INPUT_NOT_FILE", `${role}=${relativePath}`);
  }
  return issues;
}

export function formatGeneratedGapPreflight(task, issues) {
  return `generated-gap-preflight-failed task=${task ?? "MISSING"} issues=${issues.map((issue) => `${issue.code}:${issue.detail}`).join(",")}`;
}