package main

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

type PrintValueCommand struct {}
func (cmd PrintValueCommand) exec(state *ProgramState) {
	path := walk.PathFromWalkValues(state.path)
	for _, value := range state.value {
		state.out <- walk.WalkItem {
			Value: value,
			Path: path,
		}
	}
}

type ToggleTerminalCommand struct {}
func (cmd ToggleTerminalCommand) exec(state *ProgramState) {
	toggled := map[walk.TerminalValue]walk.TerminalValue {
		walk.ArrayBegin: walk.MapBegin,
		walk.ArrayEnd: walk.MapEnd,
		walk.MapBegin: walk.ArrayBegin,
		walk.MapEnd: walk.ArrayEnd,
	}

	for i := range state.value {
		terminal, isTerminal := state.value[i].(walk.TerminalValue)
		if !isTerminal {
			continue
		}
		state.value[i] = toggled[terminal]
	}
}

type FilteredCommand struct {
	filter Filter
	command Command
}
func (cmd FilteredCommand) exec(state *ProgramState) {
	path := walk.PathFromWalkValues(state.path)
	for _, value := range state.value {
		if cmd.filter.exec(walk.WalkItem {
			Value: value,
			Path: path,
		}) {
			cmd.command.exec(state)
			return
		}
	}
}

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

type AppendLiteralCommand struct {
	values []walk.WalkValue
}
func (cmd AppendLiteralCommand) exec(state *ProgramState) {
	state.value = append(state.value, cmd.values...)
}

type PrependLiteralCommand struct {
	values []walk.WalkValue
}
func (cmd PrependLiteralCommand) exec(state *ProgramState) {
	var newItems []walk.WalkValue
	newItems = append(newItems, cmd.values...)
	state.value = append(newItems, state.value...)
}

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

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

type PrintLiteralsCommand struct {
	items []walk.WalkItem
}
func (cmd PrintLiteralsCommand) exec(state *ProgramState) {
	for _, item := range cmd.items {
		state.out <- item
	}
}

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

type SubstituteCommand struct {
	subex subex.SubexState
	next Command
}
func (cmd SubstituteCommand) exec(state *ProgramState) {
	valueStream := make(chan walk.WalkValue)
	go func(in []walk.WalkValue, out chan<- walk.WalkValue) {
		for _, value := range in {
			out <- value
		}
		close(out)
	}(state.value, valueStream)
	atomStream := walk.Atomise(valueStream)
	atomsOut, error := subex.RunTransducer(cmd.subex, atomStream)
	if error {
		return
	}
	valuesOut, err := walk.MemoryCompound(atomsOut)
	if err != nil {
		return
	}
	state.value = valuesOut
	cmd.next.exec(state)
}

type Command interface {
	exec(*ProgramState)
}

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...)
}