package main

import (
	"crypto/sha1"
	"encoding/binary"
	"encoding/hex"
	"fmt"
	"strings"
)

var rom = []byte{
	0xA9, 0x16, 0x20, 0xC9, 0xFC, 0x85, 0x2E, 0x20,
	0xFA, 0xFC, 0xA0, 0x24, 0x20, 0xFD, 0xFC, 0xB0,
	0xF9, 0x20, 0xFD, 0xFC, 0xA0, 0x3B, 0x20, 0xEC,
	0xFC, 0x81, 0x3C, 0x45, 0x2E, 0x85, 0x2E, 0x20,
	0xBA, 0xFC, 0xA0, 0x35, 0x90, 0xF0, 0x20, 0xEC,
	0xFC, 0xC5, 0x2E, 0xF0, 0x0D, 0xA9, 0xC5, 0x20,
	0xED, 0xFD, 0xA9, 0xD2, 0x20, 0xED, 0xFD, 0x20,
	0xED, 0xFD, 0xA9, 0x87, 0x4C, 0xED, 0xFD, 0xA5,
	0x48, 0x48, 0xA5, 0x45, 0xA6, 0x46, 0xA4, 0x47,
	0x28, 0x60, 0x85, 0x45, 0x86, 0x46, 0x84, 0x47,
	0x08, 0x68, 0x85, 0x48, 0xBA, 0x86, 0x49, 0xD8,
	0x60, 0x20, 0x84, 0xFE, 0x20, 0x2F, 0xFB, 0x20,
	0x93, 0xFE, 0x20, 0x89, 0xFE, 0xD8, 0x20, 0x3A,
	0xFF, 0xA9, 0xAA, 0x85, 0x33, 0x20, 0x67, 0xFD,
	0x20, 0xC7, 0xFF, 0x20, 0xA7, 0xFF, 0x84, 0x34,
	0xA0, 0x17, 0x88, 0x30, 0xE8, 0xD9, 0xCC, 0xFF,
	0xD0, 0xF8, 0x20, 0xBE, 0xFF, 0xA4, 0x34, 0x4C,
	0x73, 0xFF, 0xA2, 0x03, 0x0A, 0x0A, 0x0A, 0x0A,
	0x0A, 0x26, 0x3E, 0x26, 0x3F, 0xCA, 0x10, 0xF8,
	0xA5, 0x31, 0xD0, 0x06, 0xB5, 0x3F, 0x95, 0x3D,
	0x95, 0x41, 0xE8, 0xF0, 0xF3, 0xD0, 0x06, 0xA2,
	0x00, 0x86, 0x3E, 0x86, 0x3F, 0xB9, 0x00, 0x02,
	0xC8, 0x49, 0xB0, 0xC9, 0x0A, 0x90, 0xD3, 0x69,
	0x88, 0xC9, 0xFA, 0xB0, 0xCD, 0x60, 0xA9, 0xFE,
	0x48, 0xB9, 0xE3, 0xFF, 0x48, 0xA5, 0x31, 0xA0,
	0x00, 0x84, 0x31, 0x60, 0xBC, 0xB2, 0xBE, 0xB2,
	0xEF, 0xC4, 0xB2, 0xA9, 0xBB, 0xA6, 0xA4, 0x06,
	0x95, 0x07, 0x02, 0x05, 0xF0, 0x00, 0xEB, 0x93,
	0xA7, 0xC6, 0x99, 0xB2, 0xC9, 0xBE, 0xC1, 0x35,
	0x8C, 0xC4, 0x96, 0xAF, 0x17, 0x17, 0x2B, 0x1F,
	0x83, 0x7F, 0x5D, 0xCC, 0xB5, 0xFC, 0x17, 0x17,
	0xF5, 0x03, 0xFB, 0x03, 0x62, 0xFA, 0x59, 0xFF,
}

func main() {
	print40s(expand(pad(rom[:0x37])))
	fmt.Printf("%x\n", sha1.Sum(rom[:0x37]))
	fmt.Printf("%x\n", sha1.Sum(rom[:0]))
}

func print40s(in []byte) {
	for i := 0; i < len(in); i += 20 {
		end := i + 20
		if end > len(in) {
			end = len(in)
		}
		fmt.Println(strings.ToUpper(hex.EncodeToString(in[i:end])))
	}
	fmt.Printf("length: %d 0x%x\n", len(in), len(in))
}

func pad(in []byte) []byte {
	out := make([]byte, len(in))
	copy(out, in)
	out = append(out, 0x80)
	for len(out)%64 != 56 {
		out = append(out, 0)
	}
	l := uint64(len(in)) << 3
	for i := uint(0); i < 8; i++ {
		out = append(out, byte(l>>(56-8*i)))
	}
	return out
}

func expand(in []byte) []byte {
	var w [80]uint32
	for i := 0; i < 16; i++ {
		w[i] = binary.BigEndian.Uint32(in[i*4:])
	}

	for i := 16; i < 80; i++ {
		w[i] = w[i-3] ^ w[i-8] ^ w[i-14] ^ w[i-16]
		w[i] = w[i]<<1 + w[i]>>31
	}

	out := make([]byte, len(w)*4)
	for i, wi := range w {
		binary.BigEndian.PutUint32(out[i*4:], wi)
	}
	return out
}