package main

import (
	"main/walk"
	"main/subex"
)

type Command interface {
	exec(*ProgramState)
}

type PrintValueCommand struct {}
func (cmd PrintValueCommand) exec(state *ProgramState) {
	pathValues, err := walk.Compound(state.path)
	if err != nil {
		panic("Tried to convert invalid atoms to values")
	}
	path := walk.PathFromWalkValues(pathValues)
	values, err := walk.Compound(state.value)
	if err != nil {
		panic("Tried to convert invalid atoms to values")
	}
	for _, value := range values {
		state.out <- walk.WalkItem {
			Value: value,
			Path: path,
		}
	}
}

type SequenceCommand struct {
	commands []Command
}
func (cmd SequenceCommand) exec(state *ProgramState) {
	for _, command := range cmd.commands {
		command.exec(state)
	}
}

type NextCommand struct {}
func (cmd NextCommand) exec(state *ProgramState) {
	nextItem := <- state.in
	state.value = walk.Atomise([]walk.WalkValue{nextItem.Value})
	state.path = walk.Atomise(nextItem.Path.ToWalkValues())
}

type AppendNextCommand struct {}
func (cmd AppendNextCommand) exec(state *ProgramState) {
	nextItem := <- state.in
	state.value = append(state.value, walk.Atomise([]walk.WalkValue{nextItem.Value})...)
	state.path = walk.Atomise(nextItem.Path.ToWalkValues())
}

type DeleteValueCommand struct {}
func (cmd DeleteValueCommand) exec(state *ProgramState) {
	state.value = nil
}

type DeletePathCommand struct {}
func (cmd DeletePathCommand) exec(state *ProgramState) {
	state.path = nil
}

func runSubex(state subex.SubexState, in []walk.Atom) (out []walk.Atom, error bool) {
	atomsOut, error := subex.RunTransducer(state, in)
	if error {
		return nil, true
	}
	return atomsOut, false
}

type SubstituteValueCommand struct {
	subex subex.SubexState
	next Command
}
func (cmd SubstituteValueCommand) exec(state *ProgramState) {
	newValue, err := runSubex(cmd.subex, state.value)
	if err {
		return
	}
	state.value = newValue
	cmd.next.exec(state)
}

type SubstitutePathCommand struct {
	subex subex.SubexState
	next Command
}
func (cmd SubstitutePathCommand) exec(state *ProgramState) {
	newPath, err := runSubex(cmd.subex, state.path)
	if err {
		return
	}
	state.path = newPath
	cmd.next.exec(state)
}

type NoopCommand struct {}
func (cmd NoopCommand) exec(state *ProgramState) {}

type SwapXRegCommand struct {}
func (cmd SwapXRegCommand) exec(state *ProgramState) {
	v := state.value
	state.value = state.xreg
	state.xreg = v
}

type AppendXRegCommand struct {}
func (cmd AppendXRegCommand) exec(state *ProgramState) {
	state.xreg = append(state.xreg, state.value...)
}

type SwapPathCommand struct {}
func (cmd SwapPathCommand) exec(state *ProgramState) {
	v := state.value
	state.value = state.path
	state.path = v
}

type AppendPathCommand struct {}
func (cmd AppendPathCommand) exec(state *ProgramState) {
	state.path = append(state.path, state.value...)
}