package main

import (
	"bufio"
	"io"
	"main/json"
	"main/walk"
	"os"
)

type ProgramState struct {
	value, xreg, yreg, zreg []walk.Value
	start, prevStart, end, nextEnd bool
	// TODO: This will only ever have 0 or 1 values, it is a slice out of laziness
	peekStack []walk.WalkItem
	in walk.StredReader
	out walk.StredWriter
	program []Command
	pc int
}
func (state *ProgramState) Read() (walk.WalkItem, error) {
	if len(state.peekStack) > 0 {
		item := state.peekStack[len(state.peekStack) - 1]
		state.peekStack = state.peekStack[:len(state.peekStack) - 1]
		return item, nil
	}
	return state.in.Read()
}
func (state *ProgramState) Peek() (walk.WalkItem, error) {
	item, err := state.Read()
	if err != nil {
		return walk.WalkItem{}, err
	}
	state.peekStack = append(state.peekStack, item)
	return item, nil
}

type config struct {
	quiet bool
	program string
	in io.Reader
	out io.Writer
}

func run(config config) {
	tokens := Lex(config.program)
	program := Parse(tokens)

	stdin := bufio.NewReader(config.in)
	stdout := bufio.NewWriter(config.out)

	state := ProgramState {
		in: json.NewJSONReader(stdin),
		out: json.NewJSONWriter(stdout),
		program: program,
	}

	for {
		walkItem, err := state.Read()
		if err != nil {
			break
		}
		state.value = []walk.Value{walkItem.Value}
		state.start = walkItem.Start
		state.prevStart = walkItem.PrevStart
		state.end = walkItem.End
		state.nextEnd = walkItem.NextEnd
		state.pc = 0
		for state.pc < len(state.program) {
			state.program[state.pc].exec(&state)
		}
		if !config.quiet {
			for _, value := range state.value {
				err := state.out.Write(value)
				if err != nil {
					panic("Error while outputting")
				}
			}
		}
	}

	state.in.AssertDone()
	state.out.AssertDone()
}

func main() {
	config := config {
		quiet: false,
		in: os.Stdin,
		out: os.Stdout,
	}
	hasInput := false
	
	for i := 1; i < len(os.Args); i += 1 {
		switch os.Args[i] {
			case "-n":
				config.quiet = true
				continue
		}
		if i < len(os.Args) - 1 {
			panic("Unexpected arguments after program")
		}
		config.program = os.Args[i]
		hasInput = true
	}
	if !hasInput {
		panic("Missing program")
	}

	run(config)

}