package ini

import (

	"bytes"

	"fmt"

	"strconv"

)

const (

	none = numberFormat(iota)

	binary

	octal

	decimal

	hex

	exponent

)

type numberFormat int

// numberHelper is used to dictate what format a number is in

// and what to do for negative values. Since -1e-4 is a valid

// number, we cannot just simply check for duplicate negatives.

type numberHelper struct {

	numberFormat numberFormat

	negative         bool

	negativeExponent bool

}

func (b numberHelper) Exists() bool {

	return b.numberFormat != none

}

func (b numberHelper) IsNegative() bool {

	return b.negative || b.negativeExponent

}

func (b *numberHelper) Determine(c rune) error {

	if b.Exists() {

		return NewParseError(fmt.Sprintf("multiple number formats: 0%v", string(c)))

	}

	switch c {

	case 'b':

		b.numberFormat = binary

	case 'o':

		b.numberFormat = octal

	case 'x':

		b.numberFormat = hex

	case 'e', 'E':

		b.numberFormat = exponent

	case '-':

		if b.numberFormat != exponent {

			b.negative = true

		} else {

			b.negativeExponent = true

		}

	case '.':

		b.numberFormat = decimal

	default:

		return NewParseError(fmt.Sprintf("invalid number character: %v", string(c)))

	}

	return nil

}

func (b numberHelper) CorrectByte(c rune) bool {

	switch {

	case b.numberFormat == binary:

		if !isBinaryByte(c) {

			return false

		}

	case b.numberFormat == octal:

		if !isOctalByte(c) {

			return false

		}

	case b.numberFormat == hex:

		if !isHexByte(c) {

			return false

		}

	case b.numberFormat == decimal:

		if !isDigit(c) {

			return false

		}

	case b.numberFormat == exponent:

		if !isDigit(c) {

			return false

		}

	case b.negativeExponent:

		if !isDigit(c) {

			return false

		}

	case b.negative:

		if !isDigit(c) {

			return false

		}

	default:

		if !isDigit(c) {

			return false

		}

	}

	return true

}

func (b numberHelper) Base() int {

	switch b.numberFormat {

	case binary:

		return 2

	case octal:

		return 8

	case hex:

		return 16

	default:

		return 10

	}

}

func (b numberHelper) String() string {

	buf := bytes.Buffer{}

	i := 0

	switch b.numberFormat {

	case binary:

		i++

		buf.WriteString(strconv.Itoa(i) + ": binary format\n")

	case octal:

		i++

		buf.WriteString(strconv.Itoa(i) + ": octal format\n")

	case hex:

		i++

		buf.WriteString(strconv.Itoa(i) + ": hex format\n")

	case exponent:

		i++

		buf.WriteString(strconv.Itoa(i) + ": exponent format\n")

	default:

		i++

		buf.WriteString(strconv.Itoa(i) + ": integer format\n")

	}

	if b.negative {

		i++

		buf.WriteString(strconv.Itoa(i) + ": negative format\n")

	}

	if b.negativeExponent {

		i++

		buf.WriteString(strconv.Itoa(i) + ": negative exponent format\n")

	}

	return buf.String()

}