package main

import (
	"fmt"
	"slices"
)

type Input struct {
	index int
	input []Lexeme
}

func (in Input) Index() int {
	return in.index
}

func (in Input) String() string {
	_ = in.input[in.index]
	return fmt.Sprintf("%v", in.input[in.index:])
}

func (in *Input) Len() int {
	// _ = in.input[in.index]
	return len(in.input[in.index:])
}

func (in *Input) Peek(i int) Lexeme {
	return in.input[in.index+i]
}

func (in *Input) Pop() (Lexeme, bool) {
	if in.index > len(in.input)-1 {
		return nil, false
	}
	v := in.input[in.index]
	in.index++
	return v, true
}

func (in *Input) Seek(i int) {
	_ = in.input[i]
	in.index = i
}

func (in *Input) Take(offset int) *Input {
	var out = &Input{
		index: 0,
		input: in.input[in.index : in.index+offset],
	}
	in.index += offset
	return out
}

func (in *Input) Find(open, close *Token) (int, bool) {
	level := 1
	_ = in.input[in.index]
	idx := slices.IndexFunc(in.input[in.index:], func(a Lexeme) bool {
		switch {
		case a.Equals(open):
			level++
		case a.Equals(close):
			level--
			return level == 0
		}
		return false
	})
	if idx > -1 {
		return idx, true
	} else {
		return 0, false
	}
}

func (in *Input) TakeParens(open, close *Token) (*Input, error) {
	if in.input[in.index].Equals(open) {
		return nil, noMatch
	}
	start := in.index
	level := 1
	idx := slices.IndexFunc(in.input[start+1:], func(a Lexeme) bool {
		switch {
		case a.Equals(open):
			level++
		case a.Equals(close):
			level--
			return level == 0
		}
		return false
	})
	if idx > -1 {
		_ = in.Take(idx + 1)
		return &Input{index: 0, input: in.input[start+1 : idx]}, nil
	} else {
		return nil, fmt.Errorf("unmatched parenthesis starting at %s", in.Peek(start).Position())
	}
}