import { _, cnst, g, id, l, n, pipe, r } from './core';
import { iif } from './bool';
import { Zero, ge, ifz, pred, succ } from './num';
import { x00 } from './byte';
import { fromChar as _c, dec as cdec, inc as cinc, eq, ifn } from './char';
import { Pair, first, fst, second, snd, uncurry } from './pair';
import { cons, head, repeat, set, singleton, tail, update } from './list';
import { Empty, get, len, snoc } from './string';

n('bf');

const done = g('done', uncurry._(l('p', cnst._(uncurry._(l('is', l('cs', ge._(head._('is'))._(len._('cs')))))._('p')))));

const command = g('command', l('c', uncurry._(l('p', cnst._(eq._('c')._(uncurry._(pipe._(get)._(head))._('p')))))));

const advance = g('advance', first._(first._(update._(succ)._(Zero))));

const save = g('save', first._(first._(l('is', cons._(head._('is'))._('is')))));

const restore = g('restore', first._(first._(tail)));

const reset = g('reset', first._(first._(l('is', cons._(head._('is'))._(tail._(tail._('is')))))));

const inc = g('inc', second._(first._(l('t', second._(update._(cinc)._(fst._('t')))._('t')))));

const dec = g('dec', second._(first._(l('t', second._(update._(cdec)._(fst._('t')))._('t')))));

const read = g('read', pipe._(pipe._(uncurry._(get))._(fst))._(snd));

const input = g('input', second._(uncurry._(l('t', l('io', Pair._(second._(set._(head._(fst._('io')))._(fst._('t')))._('t'))._(first._(tail)._('io')))))));

const output = g('output', second._(uncurry._(l('t', pipe._(Pair._('t'))._(second._(l('os', snoc._('os')._(uncurry._(get)._('t')))))))));

const next = g('next', second._(first._(first._(succ))));

const prev = g('prev', second._(first._(first._(pred))));

const jump = g('jump', l('d', l('s',
  iif._(command._(_c('['))._('s'))._(r('bf', 'jump')._(succ._('d')))
    ._(iif._(command._(_c(']'))._('s'))._(ifz._(pred._('d'))._(cnst._('s'))._(r('bf', 'jump')._(pred._('d'))))
      ._(r('bf', 'jump')._('d')))._(advance._('s')))));

const whlnz = g('whlnz', l('s', ifn._(read._('s'))._(jump._(Zero))._(save)._('s')));

const endwhl = g('endwhl', l('s', ifn._(read._('s'))._(reset)._(pipe._(save)._(restore))._('s')));

const exec = g('exec', l('s', iif._(done._('s'))._('s')._(r('bf', 'exec')._(advance
  ._(iif._(command._(_c('>'))._('s'))._(next)
    ._(iif._(command._(_c('<'))._('s'))._(prev)
      ._(iif._(command._(_c('+'))._('s'))._(inc)
        ._(iif._(command._(_c('-'))._('s'))._(dec)
          ._(iif._(command._(_c('.'))._('s'))._(output)
            ._(iif._(command._(_c(','))._('s'))._(input)
              ._(iif._(command._(_c('['))._('s'))._(whlnz)
                ._(iif._(command._(_c(']'))._('s'))._(endwhl)
                  ._(id))))))))._('s'))))));

export const run = g('run', l('p', l('i', snd._(snd._(snd._(exec._(Pair._(Pair._(singleton._(Zero))._('p'))._(Pair._(Pair._(Zero)._(repeat._(x00)))._(Pair._('i')._(Empty))))))))));