function cons(a, b) {
	return [a, b];
}

function *listIter(l) {
	while (l) {
		yield l[0];
		l = l[1];
	}
}

function keySymVals(obj) {
	return [...Object.getOwnPropertyNames(obj),...Object.getOwnPropertySymbols(obj)]
		.map(e => [e,obj[e]]);
}

class EaterBase {
	result = {}; ownsResult = true;

	static #bannedSymbols = new WeakSet;

	static isBannedSymbol(sym) {
		return this.#bannedSymbols.has(sym);
	}

	static banSymbol(sym) {
		this.#bannedSymbols.add(sym);
	}

	inherit(...from) {
		from = from.filter(e => e);
		if (!from.length) from = [this];
		if (from.length == 1) {
			if (from[0] == this) return;
			this.result = from[0].result;
			from[0].ownsResult = false;
			this.ownsResult = false;
		} else {
			let iter = from.map(e => ({ result: e.result, eater: e })).values();
			do {
				let val = iter.next();
				if (val.done) break;
				val.value.eater.ownsResult = false;
				this.result = { ...val.value.result };
				this.ownsResult = true;
			} while (((o)=>{
				for (let i in o) return false;
				if (Object.getOwnPropertySymbols(o).length) return false;
				return true;
			})(this.result))
			for (let k of Object.getOwnPropertySymbols(this.result)) {
				if (EaterBase.isBannedSymbol(k))
					delete this.result[k];
			}
			let vals = iter.flatMap(e => (e.eater.ownsResult=false,keySymVals(e.result)))
				.filter(([k,v]) => !EaterBase.isBannedSymbol(k));
			for (let [k, v] of vals) {
				v.type == 'list' ? [...listIter(v.data)]
					.reverse()
					.forEach(e => this.addResult(k, e))
					: this.mapResult(k, () => v.data);
			}
		}
		return this;
	}

	addResult(k, v) {
		if (!this.ownsResult) {
			this.result = { ...this.result };
			this.ownsResult = true;
		}
		if ((this.result[k]?.type??'list') != 'list') {
			return false;
		}
		this.result[k] = {
			type: 'list',
			data: cons(v, this.result[k]?.data)
		};
		return true;
	}

	setResult(k, v) {
		if (!this.ownsResult) {
			this.result = { ...this.result };
			this.ownsResult = true;
		}
		if (this.result[k]) {
			return false;
		}
		this.result[k] = {
			type: 'value',
			data: v
		};
		if (v == null)
			delete this.result[k];
		return true;
	}

	getResult(k) {
		if (this.result[k]?.type == 'value')
			return this.result[k].data;
		else if (this.result[k]?.type == 'list')
			return listIter(this.result[k].data);
		return null;
	}

	mapResult(k, f) {
		if (!this.ownsResult) {
			this.result = { ...this.result };
			this.ownsResult = true;
		}
		let v = f(this.getResult(k));
		if (v == null && (k in this.result))
			delete this.result[k]
		else if (v != null)
			this.result[k] = {
				type: 'value',
				data: v
			};
		return false;
	}

}

class EaterResult extends EaterBase {
	build() {
		return Object.fromEntries(
			Object.entries(this.result)
				.map(([k,v]) => ([k,({
					'value': v => v.data,
					'list': v => [...listIter(v.data)].reverse(),
				})[v.type](v)]))
		)
	}
}

class TransitionController {
	#decider = null;
	next = () => {
		return this.#decider();
	};
	runWith(f, decider) {
		try {
			let prevDecider = this.#decider;
			this.#decider = decider;
			return f();
		} finally {
			this.#decider = prevDecider;
		}
	}
	setDecider(decider) { this.#decider = decider; }
}

export class Eater extends EaterBase {
	constructor() {
		super();
	}

	#autoInherit(o, par, ...other) {
		par = par ?? [this];
		if (par instanceof Eater || par instanceof EaterResult)
			par = [par];
		o.inherit(...par, ...other, o);
	}

	rawNext;
	get next() {
		let next = this.rawNext;
		if (typeof next == 'function')
			return (...par) => {
				let o = next.apply(this);
				if (!o)
					o = new EaterResult;
				this.#autoInherit(o, ...par);
				if (o instanceof Eater)
					o.start();
				return o;
			};
		else if (next == null) {
			return (...par) => {
				let o = new EaterResult;
				this.#autoInherit(o, ...par);
				return o;
			}
		}
		return () => next;
	}
	set next(v) {
		if (v == null)
			v = undefined;
		else if (!(
			typeof v == 'function' ||
			v instanceof Eater ||
			v instanceof EaterResult
		)) {
			throw new TypeError('Invalid value for \'Eater.next\'');
		}
		this.rawNext = v;
	}

	isDone() { return true; }
	peek(c) { return false; }
	eat(c) { return this.peek(c); }
	start() {}
	end(c) {}

	eof() {
		let eater = this, ok;
		({ ok, eater } = this.endResolve());
		if (ok && !(eater instanceof EaterResult))
			throw new Error('EOF but still Eater');
		return ok
			? eater
			: false;
	}

	eatResolve(c) {
		let eater = this, ok;
		({ ok, eater } = this.endResolve(c));
		if (!ok)
			return {
				ate: false,
				eater: eater instanceof EaterResult ? eater
				: (e => e instanceof EaterResult ? e : false)(eater.endResolve())
			};
		if (!eater.eat(c))
			throw new Error('peek() reported edibility but eat() failed');
		return { ate: true, eater: eater.resolve() };
	}

	endResolve(...c) {
		let o = this;
		let e = !!c.length;
		let check = e
			? () => o instanceof Eater && o.peek(...c)
			: () => o instanceof EaterResult;
		let checked = null;

		while (1) {
			if (checked ? checked.res : check()) {
				return { ok: true, eater: o };
			}

			checked = null;

			if (!(o instanceof Eater))
				return { ok: false, eater: o };

			o.end(...c);
			let old = o;
			o = o.resolve();

			if ((checked = { res: check() }).res) {
				continue;
			}

			if (old == o)
				return { ok: false, eater: o };
		}
	}

	resolve() {
		if (this.isDone()) {
			let v = this.next();
			if (v instanceof Eater)
				v = v.resolve();
			return v;
		}
		return this;
	}
}

class EatGate extends Eater {
	#d = false; #fn;
	constructor(fn) {
		super();
		this.#fn = fn;
	}
	isDone() { return this.#d; }
	peek(c) { return false; }
	eat(c) { return false; }
	end(...c) {
		this.#fn(this);
		this.#d = true;
	}
}

class AbortEater extends Eater {
	isDone() { return false; }
	peek(c) { return false; }
}

class DisjunctionEater extends Eater {
	#u = []; #f = []; #d = false; #ctrl; #count=0;
	#syms = { count: Symbol('DisjunctionEater.count'), };
	constructor(ctrl, ...u) {
		super();
		ctrl.setDecider(() => {
			let o = new EatGate((o) => {
				o.setResult(this.#syms.count, this.#count);
			});
			o.next = this.rawNext;
			return o;
		});
		this.#ctrl = ctrl;
		this.#u = [...u];
	}
	#checkFinish() {
		if (this.#f.length && !this.#u.length) {
			this.#d = true;
			let next = this.#f.pop();
			for (let i in this.#syms) {
				EaterBase.banSymbol(this.#syms[i]);
			}
			this.next = next;
			this.#f = [];
		}
	}
	start() {
		let nextU = [];
		let nextF = [];
		for (let o of this.#u) {
			o.inherit(this);
			o.start();
			o = o.resolve();
			let oi = o.getResult(this.#syms.count);
			if (oi == null)
				nextU.push(o);
			else
				nextF[oi] ??= o;
		}
		this.#u = nextU;
		this.#f = nextF;
		this.#checkFinish();
	}
	end(...c) {
		let nextU = [];
		let nextF = [];
		for (let i in this.#f) {
			let o = this.#f[i];
			if (o instanceof EaterResult) {
				let oi = o.getResult(this.#syms.count);
				nextF[oi] ??= o;
				continue;
			}
			let ok;
			({ ok, eater: o } = o.endResolve(...c));
			let oi = o.getResult(this.#syms.count);
			nextF[oi] ??= o;
		}
		for (let o of this.#u) {
			let ok;
			({ ok, eater: o } = o.endResolve(...c));
			let oi = o.getResult(this.#syms.count);
			if (oi == null)
				nextU.push(o);
			else
				nextF[oi] ??= o;
		}
		this.#u = nextU;
		this.#f = nextF;
		this.#checkFinish();
	}
	peek(c) {
		for (let o of this.#u) {
			if (o.peek(c))
				return true;
		}
		for (let i in this.#f) {
			let o = this.#f[i];
			if (o instanceof EaterResult)
				continue;
			if (o.peek(c))
				return true;
		}
		return false;
	}
	isDone() {
		return this.#d;
	}
	eat(c) {
		if (!this.#u.length)
			return false;
		let nextU = [];
		let nextF = [];
		for (let i in this.#f) {
			let eater = this.#f[i];
			if (!(eater instanceof Eater)) {
				continue;
			}
			let ate;
			({ ate, eater } = eater.eatResolve(c));
			let oi = eater.getResult(this.#syms.count);
			if (ate) {
				nextF[oi] ??= eater;
			}
		}
		for (let eater of this.#u) {
			let ate;
			({ ate, eater } = eater.eatResolve(c));
			if (ate) {
				let oi = eater.getResult(this.#syms.count);
				if (oi == null) {
					nextU.push(eater);
				} else {
					nextF[oi] ??= eater;
				}
			}
		}
		this.#u = nextU;
		this.#f = nextF;
		let ok = this.#u.length || this.#f.length
		this.#checkFinish();
		this.#count++;
		return ok;
	}
}

class StringEater extends Eater {
	#s; #i=0; constructor(s) { super(); this.#s = s; }
	isDone() {
		return this.#i >= this.#s.length;
	}
	peek(c) {
		return this.#s[this.#i] == c;
	}
	eat(c) {
		let ok = this.peek(c);
		this.#i++;
		return ok;
	}
}

class RepeatEater extends Eater {
	#min; #max; #spawn; #ctrl; #sym;
	#cur = null; #cont = null; #ctrlSetNext;
	get #i() { return this.getResult(this.#sym.i) ?? 0; }
	constructor(ctrl, spawn, min, max, sym={ i: Symbol('RepeatEater.i'), over: Symbol('RepeatEater.over') }) {
		super();
		this.#ctrl = ctrl;
		let next;
		this.#ctrlSetNext = x => next = x;
		ctrl.setDecider(() => {
			let u = new (class extends Eater {
				start() {
					this.mapResult(sym.i, i => (i??0) + 1);
					this.setResult(sym.over, true);
					let next = this.next(this);
					next.sus = true;
					this.next = next;
				}
			});
			u.next = () => {
				let o = new RepeatEater(ctrl, spawn, min, max, sym);
				o.next = next;
				o.id=Math.random();
				return o;
			}
			return u
		});
		this.#spawn = function(...par) {
			let ns = spawn()
			ns.inherit(...par);
			ns.mapResult(sym.over, () => null);
			ns.start();
			return ns;
		};
		this.#min = min ?? 0;
		this.#max = max ?? Infinity;
		this.#sym = sym;
	}
	#ended = false;
	#check() {
		if (this.#cur?.getResult(this.#sym.over)) {
			this.#ended = true;
			this.next = this.#cur;
			return;
		}
		if (((!!this.#cur) + (!!this.#cont)) == 1) {
			this.#ended = true;
			this.next = this.#cur || this.#cont;
			return;
		}
	}
	start() {
		this.#ctrlSetNext(this.rawNext);
		if (this.#i < this.#max)
			this.#cur = this.#spawn(this);
		if (this.#i >= this.#min) {
			let [over, i] = ['over','i'].map(e => this.getResult(this.#sym[e]));
			this.mapResult(this.#sym.over, () => null);
			this.mapResult(this.#sym.i, () => null);
			this.#cont = this.next();
			this.mapResult(this.#sym.over, () => over);
			this.mapResult(this.#sym.i, () => i);
		}
		this.#check();
	}
	isDone() {
		return this.#ended;
	}
	peek(c) {
		return (
			(this.#cur instanceof Eater && this.#cur.peek(c)) ||
			(this.#cont instanceof Eater && this.#cont.peek(c))
		)
	}
	#forEaters(f,cl) {
		if (this.#cur instanceof Eater) {
			let etc, eater, ok;
			({ eater, ...etc } = f(this.#cur));
			ok = etc.ok ?? etc.ate;
			this.#cur = ok ? eater : null;
		} else if (cl) {
			this.#cur = null;
		}
		if (this.#cont instanceof Eater) {
			let etc, eater, ok;
			({ eater, ...etc } = f(this.#cont));
			ok = etc.ok ?? etc.ate;
			this.#cont = ok ? eater : null;
		} else if (cl) {
			this.#cont = null;
		}
		this.#check();
	}
	eat(c) {
		this.#forEaters(o => o.eatResolve(c), 1)
		return this.#cur || this.#cont
	}
	end(...c) {
		this.#forEaters(o => o.endResolve(...c), c.length);
	}
}

class CaptureEater extends Eater {
	#s; #d; #opts;
	#syms = { eaten: Symbol('CaptureEater.eaten') };
	constructor(s, { key, add, finish, multi, ctrl }) {
		super();
		this.#s = s;
		ctrl.setDecider(() => {
			let o = new EatGate(o => {
				let ok;
				if (this.#opts.multi)
					ok = o.addResult(this.#opts.key, this.#opts.finish())
				else
					ok = o.setResult(this.#opts.key, this.#opts.finish());
				o.setResult(this.#syms.eaten, true);
				if (!ok)
					o.next = () => new AbortEater;
			});
			o.next = this.rawNext;
			return o;
		});
		this.#opts = { key, add, finish, multi, ctrl };
	}
	isDone() { return this.#d; }
	#check() {
		if (this.#s.getResult(this.#syms.eaten) != null) {
			this.#d = true;
			for (let i in this.#syms) {
				EaterBase.banSymbol(this.#syms[i]);
			}
			this.next = this.#s;
		}
	}
	start() {
		this.#s.inherit(this);
		this.#s.start();
		this.#s = this.#s.resolve();
		this.#check();
	}
	end(...c) {
		({ eater: this.#s } = this.#s.endResolve(...c));
		this.#check();
	}
	peek(c) { return (this.#s instanceof Eater) && this.#s.peek(c); }
	eat(c) {
		let ate;
		({ ate, eater: this.#s } = this.#s.eatResolve(c));
		this.#opts.add(c);
		this.#check();
		return ate;
	}
}

class CharsetEater extends Eater {
	#f; #d = false;
	constructor(f) {
		super();
		this.#f = f;
	}
	isDone() { return this.#d; }
	peek(c) { return this.#f(c); }
	eat(c) {
		if (this.peek(c))
			return this.#d = true;
		return false;
	}
}

class ResultEditEater extends Eater {
	#f; constructor(f) { super(); this.#f = f; }
	isDone() { return true; }
	peek(c) { return false; }
	start() {
		let ret = this.#f({
			set: (k, v) => {
				this.mapResult(k, () => v);
			},
			get: (k) => {
				return this.getResult(k);
			},
			add: (k, v) => {
				return this.addResult(k, v);
			}
		});
		this.#f = null;
		if ((!ret) && (ret != null)) {
			this.next = () => new AbortEater;
		}
	}
}

function lastfun(f) {
	while (f.next) {
		f = f.next;
	}
	return f;
}

function _nwrapper() {
	let wf;
	wf = Object.assign((...arg) => {
		let v = wf.inner(...arg);
		v.next = wf.next;
		if (wf.dbg)
			v.dbg = wf.dbg;
		return v;
	}, {
		inner: null,
		next: null,
		prev: null,
		regexoidal: true,
	});
	return wf;
}

function nwrap(f, dbg) {
	let wf = _nwrapper();
	wf.inner = f;
	return wf;
}

function nwrapClone(wf, onLast) {
	let cf = nwrap(wf.inner);
	let fcf = cf;
	cf.prev = wf;
	while (wf) {
		if (wf.next) {
			cf.next = nwrap(wf.next.inner);
			cf.next.prev = cf;
		}

		wf = wf.next;
		if ((!wf) && onLast) {
			onLast(cf);
		}
		cf = cf.next;
	}
	return fcf;
}

function checkprev(f) {
	if (f.prev) {
		throw new Error('cannot use the same regex element more than once');
	}
}

let r = {
	seq(...elem) {
		elem = elem.map(e => {
			if (typeof e == 'function' && e.regexoidal) {
				return e;
			} else if (e.length != null) {
				return nwrap(() => new StringEater(e));
			} else {
				throw new Error('bad element: '+e);
			}
		});
		if (!elem.length) {
			elem = [nwrap(() => new Eater())];
		}
		let lastfs = elem.map(e => lastfun(e));
		for (let i=0; i<elem.length; i++) {
			let [f, lf] = [elem[i], lastfs[i]];
			checkprev(f);
			if (i < elem.length - 1){
				lf.next = elem[i+1];
			}
			if (i > 0) {
				f.prev = lastfs[i-1];
			}
		}
		return elem[0];
	},

	any(...elem) {
		elem = elem.map(e => this.seq(e));
		let f = nwrap(() => {
			let ctrl = new TransitionController;
			return new DisjunctionEater(ctrl,
				...(elem
					.map(e => nwrapClone(e, e => e.next = ctrl.next))
					.map(e => e())
				)
			)
		});
		elem.forEach(e => (
			checkprev(e),
			e.prev = f
		));
		return f;
	},

	rep([min, max], ...elem) {
		let spawn = this.seq(...elem);
		let f = nwrap(() => {
			let ctrl = new TransitionController;
			return new RepeatEater(ctrl,
				nwrapClone(spawn, e => e.next = ctrl.next),
				min, max
			)
		});
		checkprev(spawn);
		spawn.prev = f;
		return f;
	},

	abort() {
		return nwrap(() => new AbortEater);
	},

	map(f) {
		return nwrap(() => new ResultEditEater(f));
	},

	chars(pred) {
		return nwrap(() => new CharsetEater(pred));
	},

	...((o) => Object.fromEntries(
		Object.entries(o)
			.flatMap(([k,v]) => [
				[k, function(...arg) { return v.call(this, false, ...arg); }],
				[k+'Multi', function(...arg) { return v.call(this, true, ...arg); }],
			])
	))({
		mark(multi, key, value=true) {
			return nwrap(() => {
				let ctrl = new TransitionController;
				return new CaptureEater((e => (e.next = ctrl.next, e))(new Eater), {
					key,
					add: () => {},
					finish: () => value,
					multi,
					ctrl,
				})
			});
		},

		capture(multi, key, ...elem) {
			let s = this.seq(...elem);
			let f = nwrap(() => {
				let ctrl = new TransitionController;
				let val = [];
				return new CaptureEater(nwrapClone(s, e => e.next = ctrl.next)(), {
					key,
					add: c => val.push(c),
					finish: () => val.join(''),
					multi,
					ctrl,
				})
			});
			checkprev(s);
			s.prev = f;
			return f;
		},
	}),

	custom(f, ...arg) {
		return nwrap(() => f(...arg));
	},
};

for (let k in r)
	r[k] = r[k].bind(r);

export function regexoid(f) {
	let spawn = r.seq(f(r));

	return () => {
		let o = spawn();
		o.start();
		o = o.resolve();

		let eofResult = null;

		return function(chunk) {
			let i = 0;
			if (!chunk) {
				if (eofResult) {
					return eofResult;
				}
				o = ((o instanceof Eater) ? o.eof() : o) || false;
				return {
					done: true,
					match: o ? o.build() : o,
					count: 0,
				}
			} else {
				let ret;
				for (let c of chunk) {
					if (eofResult) {
						eofResult = null;
						break;
					}
					i++;
					if (o instanceof Eater) {
						let ate;
						({ ate, eater: o } = o.eatResolve(c));
						if (!ate) {
							let v = o;
							o = null;
							return {
								done: true,
								match: v ? v.build() : v,
								count: i - 1,
							}
						}
					}
					if (o instanceof EaterResult) {
						ret = eofResult = {
							done: true,
							match: o.build(),
							count: i,
						};
						o = null;
					}
				}
				if (ret)
					return ret;
			}
			return {
				done: false,
				count: i
			};
		}
	}
}