import { pipe } from 'fp-ts/function'
import { chain, orElse, right } from 'fp-ts/lib/Either'
import {
  delimited,
  many1,
  mapTo,
  optional,
  or,
  Parser,
  ParserResult,
  prefixed,
  symbol,
  tuple3,
} from './utils'
import { Expr } from '../types'

export const start = mapTo(symbol('^'), _ => Expr.Start(null))
export const end = mapTo(symbol('$'), _ => Expr.End(null))
export const anyItem = mapTo(symbol('.'), _ => Expr.AnyItem(null))
export const nextItem = mapTo(symbol(','), _ => Expr.NextItem(null))
export const anyString = mapTo(symbol('\\s'), _ => Expr.AnyString(null))
export const anyNumber = mapTo(symbol('\\n'), _ => Expr.AnyNumber(null))
export const anyBool = mapTo(symbol('\\b'), _ => Expr.AnyBool(null))
export const truthy = mapTo(symbol('\\T'), _ => Expr.Truthy(null))
export const falsey = mapTo(symbol('\\F'), _ => Expr.Falsey(null))

export const wrapQuantifiers: (e: ParserResult<Expr>) => ParserResult<Expr> =
  chain(([expr, input]) =>
    pipe(
      input,
      or([
        mapTo(symbol('*'), _ => Expr.ZeroOrMore({ expr })),
        mapTo(symbol('+'), _ => Expr.OneOrMore({ expr })),
        mapTo(symbol('?'), _ => Expr.Optional({ expr })),
      ]),
      orElse(_ => right([expr, input])),
    ),
  )

export const wrapAlt: (e: ParserResult<Expr>) => ParserResult<Expr> = chain(
  ([expr, input]) =>
    pipe(
      input,
      mapTo(prefixed(symbol('|'), many1(expressionP)), rest =>
        Expr.Or({ left: expr, right: rest }),
      ),
      orElse(_ => right([expr, input])),
    ),
)

export const expressionP: Parser<Expr> = (input: string) =>
  pipe(
    input,
    or([
      mapTo(delimited(symbol('('), many1(expressionP), symbol(')')), exprs =>
        Expr.Group({ exprs }),
      ),
      nextItem,
      anyItem,
      anyString,
      anyNumber,
      anyBool,
      truthy,
      falsey,
    ]),
    wrapQuantifiers,
    wrapAlt,
  )

export const parser = tuple3(optional(start), many1(expressionP), optional(end))

/*

{3,6} => 3 to 6 instances
(> 5) => number greater than
(< 5) => number less than
[name x] => apply x on property `name`
/x/ => match regular expression (string values in list)

*/