// Package forge implements sort of a stack-based interpreter.
package forge

import (
	"io"
	"os"

	"git.sr.ht/~cco/go-scopes/common/ptr"
	"git.sr.ht/~cco/go-scopes/common/stack"
	"git.sr.ht/~cco/go-scopes/common/voc"
)

type DataItem interface{}

type Ptr = ptr.Ptr[DataItem]
type Stack = stack.Stack[DataItem]
type Voc = voc.Vocabulary[XT]

type Callable func(*ForgeEnv, *Item)

type Item struct {
	name      string
	immediate bool
	fct       Callable
	body      Ptr
}

type XT = *Item

type ForgeEnv struct {
	ds, rs     Stack
	cp, ip, dp Ptr
	voc        *Voc
	latestXT   XT
	cstate     bool
	output     io.Writer
}

func NewVoc(parent *Voc) *Voc {
	return voc.NewVoc[XT](parent)
}

func NewFE() *ForgeEnv {
	return newFE(NewVoc(nil))
}

func (f *ForgeEnv) ChildFE() *ForgeEnv {
	return newFE(NewVoc(f.voc))
}

func newFE(voc *Voc) *ForgeEnv {
	return &ForgeEnv{
		ds:     stack.NewStack[DataItem](),
		rs:     stack.NewStack[DataItem](),
		ip:     ptr.NewSlice[DataItem](),
		voc:    voc,
		output: os.Stdout,
	}
}

// ForgeEnv methods

func (f *ForgeEnv) Exec() {
}

// dummy stuff for testing

var builtins = struct{ add, sub XT }{}

var work = struct{ square XT }{}

func init() {
	builtins.add = &Item{}
	builtins.sub = &Item{}
}