package builtins

import (
	"git.sr.ht/~cco/go-scopes/forge"
)

type FE = forge.FE
type XT = forge.XT
type FPtr = forge.FPtr

type builtins struct {
	Add, Body, Code, Comp, Drop, Dup, Get, If, IfElse, Leave, LT, Lit,
	Mult, New1, Over, Put, Reg, Repeat, Sub, Swap,
	Var1 XT
}

func Get(f FE) *builtins {
	if v, ok := f.Voc().Lookup("builtins"); ok {
		return v.(*builtins)
	}
	b := setup(f)
	f.Voc().Register("builtins", b)
	return b
}

func setup(f FE) *builtins {
	voc := f.Voc()
	r := func(name string, fct forge.Callable) XT {
		return forge.Register(voc, forge.GoFunc(name, fct))
	}
	b := builtins{
		Add:    r("+", func(f FE, _ XT) { f.Push(f.PopI() + f.PopI()) }),
		Body:   r("body", func(f FE, _ XT) { f.Push(f.Pop().(XT).Code().New().Next()) }),
		Code:   r("code", func(f FE, _ XT) { f.Push(f.Code()) }),
		Comp:   r("comp", func(f FE, _ XT) { f.LatestXT().Code().Append(f.Pop()) }),
		Drop:   r("drop", func(f FE, _ XT) { f.Pop() }),
		Dup:    r("dup", func(f FE, _ XT) { f.Push(f.Peek(0)) }),
		Get:    r("@", func(f FE, _ XT) { f.Push(f.Pop().(FPtr).Value()) }),
		If:     r("if", func(f FE, _ XT) { doif(f) }),
		IfElse: r("if-else", func(f FE, _ XT) { doifelse(f) }),
		Leave:  r("leave", func(f FE, _ XT) { f.RPop() }),
		Lit:    r("lit", func(f FE, _ XT) { f.Push(f.Literal()) }),
		LT:     r("<", func(f FE, _ XT) { f.Push(f.PopI() > f.PopI()) }),
		Mult:   r("*", func(f FE, _ XT) { f.Push(f.PopI() * f.PopI()) }),
		New1:   r("new1", func(f FE, _ XT) { f.Push(f.NewVar()) }),
		Over:   r("over", func(f FE, _ XT) { f.Push(f.Peek(1)) }),
		Put:    r("!", func(f FE, _ XT) { f.Pop().(FPtr).Set(f.Pop()) }),
		Reg:    r("reg", func(f FE, _ XT) { doreg(f) }),
		Repeat: r("repeat", func(f FE, _ XT) { f.Reset() }),
		Sub: r("-", func(f FE, _ XT) {
			a := f.PopI()
			f.Push(f.PopI() - a)
		}),
		Swap: r("swap", func(f FE, _ XT) { doswap(f) }),
		/*Append:  r("append", func(f FE, _ XT) {
			item := f.Pop()
			f.Peek(0).(FPtr).Append(item)
		}),*/
	}
	rf := func(name string, code ...forge.FItem) XT {
		return forge.Register(voc, forge.FCode(name, f.Code(code...)))
	}
	b.Var1 = rf("var1", b.Code, b.Swap, b.Reg, b.New1, b.Comp)
	return &b
}

func doif(f FE) {
	ifBranch := f.Literal().(FPtr)
	if f.Pop().(bool) {
		f.Call(ifBranch)
	}
}

func doifelse(f FE) {
	ifBranch := f.Literal().(FPtr)
	elseBranch := f.Literal().(FPtr)
	if f.Pop().(bool) {
		f.Call(ifBranch)
	} else {
		f.Call(elseBranch)
	}
}

func doswap(f FE) {
	a := f.Pop()
	b := f.Pop()
	f.Push(a)
	f.Push(b)
}

func doreg(f FE) {
	f.Register(forge.FCode(f.Pop().(string), f.Pop().(FPtr)))
}

func create(f FE, _ XT) {
	name := f.Pop().(string)
	does := forge.AnonCode(f.Pop().(FPtr))
	f.Register(forge.GoFunc(name, func(f FE, _ XT) {
		f.Register(forge.FCode(f.Pop().(string),
			f.Code(f.NewVar(), does)))
	}))
}