package mp

import (
	"crypto/hmac"
	"crypto/sha256"
	"encoding/binary"
	"golang.org/x/crypto/scrypt"
	"runtime"
	"sync"
)

type TemplateType int

const (
	MaximumSecurityPassword TemplateType = iota
	LongPassword
	MediumPassword
	BasicPassword
	ShortPassword
	PIN
	Name
	Phrase
)

const variant = "com.lyndir.masterpassword"

var (
	typeMap = map[TemplateType][]string{
		MaximumSecurityPassword: {
			"anoxxxxxxxxxxxxxxxxx",
			"axxxxxxxxxxxxxxxxxno",
		},
		LongPassword: {
			"CvcvnoCvcvCvcv",
			"CvcvCvcvnoCvcv",
			"CvcvCvcvCvcvno",
			"CvccnoCvcvCvcv",
			"CvccCvcvnoCvcv",
			"CvccCvcvCvcvno",
			"CvcvnoCvccCvcv",
			"CvcvCvccnoCvcv",
			"CvcvCvccCvcvno",
			"CvcvnoCvcvCvcc",
			"CvcvCvcvnoCvcc",
			"CvcvCvcvCvccno",
			"CvccnoCvccCvcv",
			"CvccCvccnoCvcv",
			"CvccCvccCvcvno",
			"CvcvnoCvccCvcc",
			"CvcvCvccnoCvcc",
			"CvcvCvccCvccno",
			"CvccnoCvcvCvcc",
			"CvccCvcvnoCvcc",
			"CvccCvcvCvccno",
		},
		MediumPassword: {
			"CvcnoCvc",
			"CvcCvcno",
		},
		BasicPassword: {
			"aaanaaan",
			"aannaaan",
			"aaannaaa",
		},
		ShortPassword: {
			"Cvcn",
		},
		PIN: {
			"nnnn",
		},
		Name: {
			"cvccvcvcv",
		},
		Phrase: {
			"cvcc cvc cvccvcv cvc",
			"cvc cvccvcvcv cvcv",
			"cv cvccv cvc cvcvccv",
		},
	}
	charMap = map[rune]string{
		'V': "AEIOU",
		'C': "BCDFGHJKLMNPQRSTVWXYZ",
		'v': "aeiou",
		'c': "bcdfghjklmnpqrstvwxyz",
		'A': "AEIOUBCDFGHJKLMNPQRSTVWXYZ",
		'a': "AEIOUaeiouBCDFGHJKLMNPQRSTVWXYZbcdfghjklmnpqrstvwxyz",
		'n': "0123456789",
		'o': "@&%?,=[]_:-+*$#!'^~;()/.",
		'x': "AEIOUaeiouBCDFGHJKLMNPQRSTVWXYZbcdfghjklmnpqrstvwxyz0123456789!@#$%^&*()",
		' ': " ",
	}
)

func i2b(i int) (b []byte) {
	b = make([]byte, 4)
	binary.BigEndian.PutUint32(b, uint32(i))
	return
}

type MP struct {
	sync.Mutex
	key []byte
}

func NewMP(p, name []byte) (*MP, error) {
	salt := []byte(variant)
	salt = append(salt, i2b(len(name))...)
	salt = append(salt, name...)
	key, err := scrypt.Key(p, salt, 32768, 8, 2, 64)
	defer func() {
		for i := range p {
			p[i] = byte(0)
		}
		for i := range name {
			name[i] = byte(0)
		}
	}()
	if err != nil {
		return nil, err
	}
	return &MP{key: key}, nil
}

func (mp *MP) PrintPassword(site string, counter int, tempType TemplateType) {
	mp.Lock()
	defer mp.Unlock()
	salt := []byte(variant)
	salt = append(salt, i2b(len(site))...)
	salt = append(salt, []byte(site)...)
	salt = append(salt, i2b(counter)...)
	mac := hmac.New(sha256.New, mp.key)
	mac.Write(salt)
	seed := mac.Sum(nil)
	templates := typeMap[tempType]
	temp := templates[int(seed[0])%len(templates)]
	for i, c := range temp {
		chars := charMap[c]
		print(string(chars[int(seed[i+1])%len(chars)]))
	}
	print("\n")
}

func (mp *MP) DestroyKey() {
	mp.Lock()
	for i := range mp.key {
		mp.key[i] = byte(0)
	}
	mp.key = nil
	runtime.GC()
	mp.Unlock()
}