type-level-parser.ts

type ok<value, rest> = [value, rest];
type fail = [];
type fix_intersection<a> = { [key in keyof a]: a[key] }

type parse_substring<sub extends string, s1> =
  s1 extends `${sub}${infer s2}` ?
  ok<null, s2> : fail;

type space = " " | "\n";
type parse_space<s1> =
  s1 extends `${space}${infer s2}` ? parse_space<s2> : ok<null, s1>;

type parse_name<s1> =
  s1 extends `${infer name}:${infer s2}` ?
  ok<name, `:${s2}`> : fail;

type prims = {
  number: number,
  string: string,
  boolean: boolean,
};

type parse_type<s1> =
  s1 extends `${keyof prims}${infer s2}` ?
  s1 extends `${infer type_}${s2}` ? ok<prims[type_ & keyof prims], s2> : fail :
  parse_record<s1>;

type parse_field<s1> =
  parse_name<s1> extends ok<infer name, infer s2> ?
  name extends string ?
  parse_substring<": ", s2> extends ok<null, infer s3> ?
  parse_type<s3> extends ok<infer type_, infer s4> ?
  ok<{[k in name]: type_}, s4> : fail : fail : fail : fail;

type parse_fields<s1> =
  parse_field<s1> extends ok<infer field, infer s2>
    ? parse_substring<",", s2> extends ok<null, infer s3> ?
      parse_space<s3> extends ok<null, infer s4> ?
      parse_fields<s4> extends ok<infer fields, infer s5> ?
      ok<fix_intersection<field & fields>, s5> : fail : fail : ok<field, s2>
    : ok<{}, s1>

type parse_record<s1> =
  parse_substring<"{", s1> extends ok<null, infer s2> ?
  parse_space<s2> extends ok<null, infer s3> ?
  parse_fields<s3> extends ok<infer fields, infer s4> ?
  parse_space<s4> extends ok<null, infer s5> ?
  parse_substring<"}", s5> extends ok<null, infer s6> ?
  ok<fields, s6> : fail : fail : fail : fail : fail;

type run<result> = result extends ok<infer value, ""> ? value : never;

const asrc = `{      
  a: number,  e: boolean,
    b: { c: string, d: string   } 
  }`;










type a = run<parse_record<typeof asrc>>;
const a: a = { e: true, a: 1, b: { c: "hello", d: "world" } };