// util.parseEnv: a .env-file parser matching Node's src/node_dotenv.cc ParseContent
// (reimplemented from its documented behavior). No variable interpolation: `${FOO}`
// is kept literally, as Node's own parser does.
function trimSpaces(s: string): string {
  const start = s.search(/[^ \t\n]/);
  if (start === -1) return "";
  let end = s.length - 1;
  while (end >= 0 && " \t\n".includes(s[end]!)) end--;
  return s.slice(start, end + 1);
}

export function parseEnv(content: unknown): Record<string, string> {
  if (typeof content !== "string") {
    const got = content === null || content === undefined ? ` Received ${content}`
      : typeof content === "function" ? ` Received function ${(content as { name?: string }).name || "anonymous"}`
      : typeof content === "object" ? ` Received an instance of ${(content as object).constructor?.name ?? "Object"}`
      : ` Received type ${typeof content} (${String(content)})`;
    throw Object.assign(new TypeError(`The "content" argument must be of type string.${got}`), { code: "ERR_INVALID_ARG_TYPE" });
  }
  const store: Record<string, string> = Object.create(null);
  const text = content.replace(/\r/g, "");
  let rest = trimSpaces(text);

  while (rest.length > 0) {
    if (rest[0] === "\n" || rest[0] === "#") {
      const nl = rest.indexOf("\n");
      rest = nl === -1 ? "" : rest.slice(nl + 1);
      continue;
    }

    const stop = (() => {
      for (let i = 0; i < rest.length; i++) {
        if (rest[i] === "=" || rest[i] === "\n") return i;
      }
      return -1;
    })();
    if (stop === -1 || rest[stop] === "\n") {
      if (stop !== -1) {
        rest = trimSpaces(rest.slice(stop + 1));
        continue;
      }
      break;
    }

    let key = trimSpaces(rest.slice(0, stop));
    rest = rest.slice(stop + 1);

    if (rest.length === 0 || rest[0] === "\n") {
      if (key) store[key] = "";
      rest = rest.length === 0 ? "" : rest.slice(1);
      continue;
    }

    rest = trimSpaces(rest);
    if (key === "") continue;
    if (key.startsWith("export ")) key = trimSpaces(key.slice(7));

    if (rest.length === 0) {
      store[key] = "";
      break;
    }

    // A double-quoted value may span lines; \n inside it becomes a real newline.
    if (rest[0] === '"') {
      const closing = rest.indexOf('"', 1);
      if (closing !== -1) {
        const value = rest.slice(1, closing).replace(/\\n/g, "\n");
        store[key] = value;
        const nl = rest.indexOf("\n", closing + 1);
        rest = nl === -1 ? "" : rest.slice(nl + 1);
        continue;
      }
    }

    if (rest[0] === "'" || rest[0] === '"' || rest[0] === "`") {
      const quote = rest[0];
      const closing = rest.indexOf(quote, 1);
      if (closing === -1) {
        const nl = rest.indexOf("\n");
        if (nl !== -1) {
          store[key] = rest.slice(0, nl);
          rest = rest.slice(nl + 1);
        } else {
          store[key] = rest;
          break;
        }
      } else {
        store[key] = rest.slice(1, closing);
        const nl = rest.indexOf("\n", closing + 1);
        rest = nl === -1 ? "" : rest.slice(nl + 1);
        continue;
      }
    } else {
      const nl = rest.indexOf("\n");
      let value = nl === -1 ? rest : rest.slice(0, nl);
      const hash = value.indexOf("#");
      if (hash !== -1) value = value.slice(0, hash);
      store[key] = trimSpaces(value);
      rest = nl === -1 ? "" : rest.slice(nl + 1);
    }

    rest = trimSpaces(rest);
  }

  return store;
}