init {
	stock := nil
	shortage := nil
}

channel CIO_enter {
	out arrival(s:Tuple, arrive(item:Str, num:Int)) == tuple(item, num)
}

channel CIO_req {
	out request(r:Tuple, req(item:Str, num:Int)) == tuple(item, num)
}

channel C1 {
	in arrival(ar, update1(ar2, st)) == ar2
	ref stock(st:Map, update1(ar2, st))
	out available(av:Tuple, update1(ar2, st)) == tuple(fst(ar2), snd(ar2) + lookup(st, fst(ar2)))
}

channel C2 {
	in available(av, update2(av2, sh)) == av2
	ref shortage(sh, update2(av2, sh))
	out deriver(dr:Tuple, update2(av2, sh)) == if(ge(snd(av2), lookup(sh, fst(av2))), 
												tuple(fst(av2), lookup(sh, fst(av2)), snd(av2) - lookup(sh, fst(av2))), 
												tuple(fst(av2), 0, snd(av2)))
	out shortage(s, update2(av2, sh)) == if(ge(snd(av2), lookup(s, fst(av2))), 
												insert(s, fst(av2), 0), 
												s)
}

channel C3 {
	in deriver(dr, update3(dr2)) == dr2
	out stock(st, update3(dr2)) == insert(st, fst(dr2), snd(snd(dr2)))
	out shipping(sp:Tuple, update3(dr2)) == tuple(fst(dr2), fst(snd(dr2)))
}

channel C4 {
	in request(rq, update4(rq2, st)) == rq2
	ref stock(st, update4(rq2, st))
	out deriver(dr, update4(rq2, st)) == if(ge(lookup(st, fst(rq2)), snd(rq2)), 
												tuple(fst(rq2), snd(rq2), lookup(st, fst(rq2)) - snd(rq2)), 
												tuple(fst(rq2), 0, lookup(st, fst(rq2))))
	out shortage(sh, update4(rq2, st)) == if(ge(lookup(st, fst(rq2)), snd(rq2)), 
												sh, 
												insert(sh, fst(rq2), lookup(sh, fst(rq2)) + snd(rq2)))
}