3 files changed, 170 insertions, 0 deletions
diff --git a/src/utils/adt.ts b/src/utils/adt.ts
new file mode 100644
index 0000000..45d9e50
--- /dev/null
+++ b/src/utils/adt.ts
@@ -0,0 +1,32 @@
+type TagValue<T, N> = T extends Tag<N, infer V> ? V : never
+
+export const match = <R, T extends Tag<string, any>>(
+  tag: T,
+  pattern: {
+    [key in T['tag'] | '_']?: (v: TagValue<T, key>) => R
+  },
+): R => ((pattern as any)[tag.tag] || (pattern._ as any))(tag.value)
+
+export const matchString = <R, T extends string = string>(
+  key: T,
+  pattern: {
+    [key in T | '_']?: (key: key) => R
+  },
+): R => ((pattern as any)[key] || (pattern._ as any))(key)
+
+type Tag<N, V> = { tag: N; value: V }
+export type Enum<T> = { [N in keyof T]: Tag<N, T[N]> }[keyof T]
+
+export const constructors = <T extends Tag<string, any>>(): {
+  [N in T['tag']]: TagValue<T, N> extends null | never
+    ? (value?: null | never) => T
+    : (value: TagValue<T, N>) => T
+} =>
+  new Proxy(
+    {},
+    {
+      get(_, k) {
+        return (value: any) => ({ tag: k, value })
+      },
+    },
+  ) as any
diff --git a/src/utils/parser-comb.ts b/src/utils/parser-comb.ts
new file mode 100644
index 0000000..3f171b8
--- /dev/null
+++ b/src/utils/parser-comb.ts
@@ -0,0 +1,120 @@
+import { match } from './adt'
+import { Result, mapResult, chainResult } from './result'
+
+export type ParseResult<T> = Result<
+  { value: T; input: string },
+  { error: string; input: string }
+>
+
+export type Parser<T> = (input: string) => ParseResult<T>
+
+export const regex =
+  (re: RegExp): Parser<string> =>
+  input => {
+    if (input.length === 0) return Result.Err({ error: 'fuckedinput', input })
+    const res = input.match(re)
+    if (!res) return Result.Err({ error: 'fucked', input })
+    return Result.Ok({ value: res[0], input: input.replace(re, '') })
+  }
+
+export const string =
+  (str: string): Parser<string> =>
+  input => {
+    if (input.length === 0) return Result.Err({ error: 'fuckedinput', input })
+    if (!input.startsWith(str))
+      return Result.Err({ error: 'fuckedstring', input })
+    return Result.Ok({ value: str, input: input.slice(str.length) })
+  }
+
+export const or =
+  <T>([parser, ...rest]: Array<Parser<T>>): Parser<T> =>
+  input => {
+    if (rest.length === 0) return parser(input)
+    const result = parser(input)
+    return match(result, {
+      Ok: () => result,
+      Err: _ => or(rest)(input),
+    })
+  }
+
+export const mapParseResult =
+  <T, R>(
+    parser: Parser<T>,
+    fn: (_: { value: T; input: string }) => { value: R; input: string },
+  ): Parser<R> =>
+  input =>
+    mapResult(parser(input), fn)
+
+export const map = <T, R>(parser: Parser<T>, fn: (_: T) => R): Parser<R> =>
+  mapParseResult(parser, ({ value, ...rest }) => ({
+    ...rest,
+    value: fn(value),
+  }))
+
+export const zip2 =
+  <A, B>(parserA: Parser<A>, parserB: Parser<B>): Parser<readonly [A, B]> =>
+  input => {
+    // TODO: refactor please. shit code
+    const resa: Result<
+      { value: A; input: string },
+      { error: string; input: string }
+    > = parserA(input)
+    return chainResult(resa, ({ value: a, input: inputB }) => {
+      const res: Result<
+        { value: readonly [A, B]; input: string },
+        { error: string; input: string }
+      > = map(parserB, b => [a, b] as const)(inputB)
+      return res
+    })
+  }
+
+export const prefixed = <A>(
+  parserPrefix: Parser<any>,
+  parser: Parser<A>,
+): Parser<A> => map(zip2(parserPrefix, parser), ([_, a]) => a)
+
+export const suffixed = <A>(
+  parser: Parser<A>,
+  parserSuffix: Parser<any>,
+): Parser<A> => map(zip2(parser, parserSuffix), ([a, _]) => a)
+
+export const between = <A>(
+  prefix: Parser<any>,
+  parser: Parser<A>,
+  suffix: Parser<any>,
+): Parser<A> => suffixed(prefixed(prefix, parser), suffix)
+
+export const many0 =
+  <A>(parser: Parser<A>): Parser<Array<A>> =>
+  originalInput =>
+    match(parser(originalInput), {
+      Ok: ({ value, input }) => map(many0(parser), ls => [value, ...ls])(input),
+      Err: ({ input }) => Result.Ok({ value: [], input }),
+    })
+
+export const many1 =
+  <A>(parser: Parser<A>): Parser<Array<A>> =>
+  originalInput =>
+    match(parser(originalInput), {
+      Ok: ({ value, input }) => map(many0(parser), ls => [value, ...ls])(input),
+      Err: err => Result.Err(err),
+    })
+
+export const sepBy =
+  <A>(parser: Parser<A>, sepP: Parser<any>): Parser<Array<A>> =>
+  originalInput =>
+    match(parser(originalInput), {
+      Ok: ({ value, input }) =>
+        map(many0(prefixed(sepP, parser)), ls => [value, ...ls])(input),
+      Err: _ => Result.Ok({ value: [], input: originalInput }),
+    })
+
+export const optional =
+  <A>(parser: Parser<A>): Parser<undefined | A> =>
+  input => {
+    const result = parser(input)
+    return match(result, {
+      Ok: _ => result,
+      Err: _ => Result.Ok({ value: undefined, input }),
+    })
+  }
diff --git a/src/utils/result.ts b/src/utils/result.ts
new file mode 100644
index 0000000..39a7fe6
--- /dev/null
+++ b/src/utils/result.ts
@@ -0,0 +1,18 @@
+import { Enum, constructors, match } from './adt'
+
+export type Result<V, E> = Enum<{ Ok: V; Err: E }>
+export const Result = constructors<Result<any, any>>()
+
+export const mapResult = <A, B, E>(
+  res: Result<A, E>,
+  fn: (_: A) => B,
+): Result<B, E> => chainResult(res, a => Result.Ok(fn(a)))
+
+export const chainResult = <A, B, E>(
+  res: Result<A, E>,
+  fn: (_: A) => Result<B, E>,
+): Result<B, E> =>
+  match(res, {
+    Ok: a => fn(a),
+    Err: e => Result.Err(e),
+  })