package byteutil

import (
	"reflect"
	"unsafe"
)

// Copy returns a copy of []byte.
func Copy(b []byte) []byte {
	if b == nil {
		return nil
	}
	p := make([]byte, len(b))
	copy(p, b)
	return p
}

// B2S returns a string representation of []byte without allocation.
func B2S(b []byte) string {
	return *(*string)(unsafe.Pointer(&b))
}

// S2B returns a []byte representation of string without allocation (minus slice header).
func S2B(s string) []byte {
	var b []byte

	// Get byte + string headers
	bh := (*reflect.SliceHeader)(unsafe.Pointer(&b))
	sh := (*reflect.StringHeader)(unsafe.Pointer(&s))

	// Manually set bytes to string
	bh.Data = sh.Data
	bh.Len = sh.Len
	bh.Cap = sh.Len

	return b
}

// ToUpper offers a faster ToUpper implementation using a lookup table.
func ToUpper(b []byte) {
	const toUpperTable = "\x00\x01\x02\x03\x04\x05\x06\a\b\t\n\v\f\r\x0e\x0f\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f" +
		" !\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`ABCDEFGHIJKLMNOPQRSTUVWXYZ{|}~" +
		"\u007f\x80\x81\x82\x83\x84\x85\x86\x87\x88\x89\x8a\x8b\x8c\x8d\x8e\x8f\x90\x91\x92\x93\x94\x95\x96" +
		"\x97\x98\x99\x9a\x9b\x9c\x9d\x9e\x9f\xa0\xa1\xa2\xa3\xa4\xa5\xa6\xa7\xa8\xa9\xaa\xab\xac\xad\xae\xaf" +
		"\xb0\xb1\xb2\xb3\xb4\xb5\xb6\xb7\xb8\xb9\xba\xbb\xbc\xbd\xbe\xbf\xc0\xc1\xc2\xc3\xc4\xc5\xc6\xc7\xc8" +
		"\xc9\xca\xcb\xcc\xcd\xce\xcf\xd0\xd1\xd2\xd3\xd4\xd5\xd6\xd7\xd8\xd9\xda\xdb\xdc\xdd\xde\xdf\xe0\xe1" +
		"\xe2\xe3\xe4\xe5\xe6\xe7\xe8\xe9\xea\xeb\xec\xed\xee\xef\xf0\xf1\xf2\xf3\xf4\xf5\xf6\xf7\xf8\xf9\xfa\xfb\xfc\xfd\xfe\xff"
	for i := 0; i < len(b); i++ {
		b[i] = toUpperTable[b[i]]
	}
}

// ToLower offers a faster ToLower implementation using a lookup table.
func ToLower(b []byte) {
	const toLowerTable = "\x00\x01\x02\x03\x04\x05\x06\a\b\t\n\v\f\r\x0e\x0f\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f" +
		" !\"#$%&'()*+,-./0123456789:;<=>?@abcdefghijklmnopqrstuvwxyz[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~" +
		"\u007f\x80\x81\x82\x83\x84\x85\x86\x87\x88\x89\x8a\x8b\x8c\x8d\x8e\x8f\x90\x91\x92\x93\x94\x95\x96" +
		"\x97\x98\x99\x9a\x9b\x9c\x9d\x9e\x9f\xa0\xa1\xa2\xa3\xa4\xa5\xa6\xa7\xa8\xa9\xaa\xab\xac\xad\xae\xaf" +
		"\xb0\xb1\xb2\xb3\xb4\xb5\xb6\xb7\xb8\xb9\xba\xbb\xbc\xbd\xbe\xbf\xc0\xc1\xc2\xc3\xc4\xc5\xc6\xc7\xc8" +
		"\xc9\xca\xcb\xcc\xcd\xce\xcf\xd0\xd1\xd2\xd3\xd4\xd5\xd6\xd7\xd8\xd9\xda\xdb\xdc\xdd\xde\xdf\xe0\xe1" +
		"\xe2\xe3\xe4\xe5\xe6\xe7\xe8\xe9\xea\xeb\xec\xed\xee\xef\xf0\xf1\xf2\xf3\xf4\xf5\xf6\xf7\xf8\xf9\xfa\xfb\xfc\xfd\xfe\xff"
	for i := 0; i < len(b); i++ {
		b[i] = toLowerTable[b[i]]
	}
}