package utils

import (
	"bytes"
	"encoding/binary"
	"io"
)

// ReadUintN reads N bytes
// ToDo: add tests
func ReadUintN(b io.ByteReader, length uint8) (uint64, error) {
	var res uint64
	for i := uint8(0); i < length; i++ {
		bt, err := b.ReadByte()
		if err != nil {
			return 0, err
		}
		res ^= uint64(bt) << (i * 8)
	}
	return res, nil
}

// ReadUint32 reads a uint32
func ReadUint32(b io.ByteReader) (uint32, error) {
	slice, err := readNBytes(b, 4)
	if err != nil {
		return 0, err
	}
	return binary.LittleEndian.Uint32(slice), nil
}

// ReadUint32BigEndian reads a uint32 Big Endian
func ReadUint32BigEndian(b io.ByteReader) (uint32, error) {
	slice, err := readNBytes(b, 4)
	if err != nil {
		return 0, err
	}
	return binary.BigEndian.Uint32(slice), nil
}

// ReadUint16 reads a uint16
func ReadUint16(b io.ByteReader) (uint16, error) {
	slice, err := readNBytes(b, 2)
	if err != nil {
		return 0, err
	}
	return binary.LittleEndian.Uint16(slice), nil
}

func readNBytes(b io.ByteReader, n int) ([]byte, error) {
	slice := make([]byte, n, n)
	var val uint8
	var err error
	for i := 0; i < n; i++ {
		val, err = b.ReadByte()
		if err != nil {
			return []byte{}, err
		}
		slice[i] = val
	}
	return slice, nil
}

// WriteUint64 writes a uint64
func WriteUint64(b *bytes.Buffer, i uint64) {
	b.WriteByte(uint8(i & 0xff))
	b.WriteByte(uint8((i >> 8) & 0xff))
	b.WriteByte(uint8((i >> 16) & 0xff))
	b.WriteByte(uint8((i >> 24) & 0xff))
	b.WriteByte(uint8((i >> 32) & 0xff))
	b.WriteByte(uint8((i >> 40) & 0xff))
	b.WriteByte(uint8((i >> 48) & 0xff))
	b.WriteByte(uint8(i >> 56))
}

// WriteUint32 writes a uint32
func WriteUint32(b *bytes.Buffer, i uint32) {
	b.WriteByte(uint8(i & 0xff))
	b.WriteByte(uint8((i >> 8) & 0xff))
	b.WriteByte(uint8((i >> 16) & 0xff))
	b.WriteByte(uint8((i >> 24) & 0xff))
}

// WriteUint32BigEndian writes a uint32
func WriteUint32BigEndian(b *bytes.Buffer, i uint32) {
	b.WriteByte(uint8((i >> 24) & 0xff))
	b.WriteByte(uint8((i >> 16) & 0xff))
	b.WriteByte(uint8((i >> 8) & 0xff))
	b.WriteByte(uint8(i & 0xff))
}

// WriteUint16 writes a uint16
func WriteUint16(b *bytes.Buffer, i uint16) {
	b.WriteByte(uint8(i & 0xff))
	b.WriteByte(uint8((i >> 8) & 0xff))
}

// Uint32Slice attaches the methods of sort.Interface to []uint32, sorting in increasing order.
type Uint32Slice []uint32

func (s Uint32Slice) Len() int           { return len(s) }
func (s Uint32Slice) Less(i, j int) bool { return s[i] < s[j] }
func (s Uint32Slice) Swap(i, j int)      { s[i], s[j] = s[j], s[i] }