deserialize.ts

// TODO: Make typescript happy here.
type JSONValue =
  | string
  | number
  | boolean
  | { [x: string]: JSONValue }
  | Array<JSONValue>;

interface JSONObject {
  [x: string]: JSONValue;
}

type JSONArray = Array<JSONValue>;

function update(
  data: JSONObject,
  keys: string[],
  value: JSONArray | JSONObject | JSONValue,
) {
  if (keys.length === 0) {
    // Leaf node
    return value;
  }

  let key = keys.shift();
  if (!key) {
    data = data || [];
    if (Array.isArray(data)) {
      key = data.length;
    }
  }

  // Try converting key to a numeric value
  const index = +key;
  if (!isNaN(index)) {
    // We have a numeric index, make data a numeric array
    // This will not work if this is a associative array
    // with numeric keys
    data = data || [];
    key = index;
  }

  // If none of the above matched, we have an associative array
  data = data || {};

  const val = update(data[key], keys, value);
  data[key] = val;

  return data;
}

export const deserialize = (formData: FormData) => {
  return Array.from(formData.entries()).reduce((data, [field, value]) => {
    console.log({ data });
    const matchResult: RegExpMatchArray = field.match(
      /^([^\[]+)((?:\[[^\]]*\])*)/,
    );
    let [_, prefix, keys] = matchResult;
    if (keys) {
      keys = Array.from(keys.matchAll(/\[([^\]]*)\]/g), (m) => m[1]);
      value = update(data[prefix], keys, value);
    }
    data[prefix] = value;
    return data;
  }, {});
};