/*
Licensed to the Apache Software Foundation (ASF) under one
or more contributor license agreements.  See the NOTICE file
distributed with this work for additional information
regarding copyright ownership.  The ASF licenses this file
to you under the Apache License, Version 2.0 (the
"License"); you may not use this file except in compliance
with the License.  You may obtain a copy of the License at

  http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing,
software distributed under the License is distributed on an
"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
KIND, either express or implied.  See the License for the
specific language governing permissions and limitations
under the License.
*/

package main

import (
	"encoding/hex"
	"fmt"

	amcl "git.apache.org/incubator-milagro-crypto.git/go/amcl-go"
)

func main() {
	// Assign the End-User an ID
	IDstr := "testUser@miracl.com"
	ID := []byte(IDstr)
	fmt.Printf("ID: ")
	amcl.MPIN_printBinary(ID)
	fmt.Printf("\n")

	// Epoch time in days
	date := amcl.MPIN_today()

	// PIN variable to create token
	PIN1 := -1
	// PIN variable to authenticate
	PIN2 := -1

	// Seed value for Random Number Generator (RNG)
	seedHex := "9e8b4178790cd57a5761c4a6f164ba72"
	seed, err := hex.DecodeString(seedHex)
	if err != nil {
		fmt.Println("Error decoding seed value")
		return
	}
	rng := amcl.NewRAND()
	rng.Seed(len(seed), seed)

	const EGS = amcl.MPIN_EGS
	const EFS = amcl.MPIN_EFS
	const G1S = 2*EFS + 1 /* Group 1 Size */
	const G2S = 4 * EFS   /* Group 2 Size */
	const EAS = amcl.MPIN_PAS

	var MS1 [EGS]byte
	var SS1 [G2S]byte
	var CS1 [G1S]byte
	var TP1 [G1S]byte
	var MS2 [EGS]byte
	var SS2 [G2S]byte
	var CS2 [G1S]byte
	var TP2 [G1S]byte
	var SS [G2S]byte
	var TP [G1S]byte
	var TOKEN [G1S]byte
	var SEC [G1S]byte
	var U [G1S]byte
	var UT [G1S]byte
	var X [EGS]byte
	var Y [EGS]byte
	var E [12 * EFS]byte
	var F [12 * EFS]byte
	var HID [G1S]byte
	var HTID [G1S]byte

	// Generate Master Secret Share 1
	amcl.MPIN_RANDOM_GENERATE(rng, MS1[:])
	fmt.Printf("MS1: 0x")
	amcl.MPIN_printBinary(MS1[:])

	// Generate Master Secret Share 2
	amcl.MPIN_RANDOM_GENERATE(rng, MS2[:])
	fmt.Printf("MS2: 0x")
	amcl.MPIN_printBinary(MS2[:])

	// Either Client or TA calculates Hash(ID)
	HCID := amcl.MPIN_HASH_ID(ID)

	// Generate server secret share 1
	amcl.MPIN_GET_SERVER_SECRET(MS1[:], SS1[:])
	fmt.Printf("SS1: 0x")
	amcl.MPIN_printBinary(SS1[:])

	// Generate server secret share 2
	amcl.MPIN_GET_SERVER_SECRET(MS2[:], SS2[:])
	fmt.Printf("SS2: 0x")
	amcl.MPIN_printBinary(SS2[:])

	// Combine server secret shares
	rtn := amcl.MPIN_RECOMBINE_G2(SS1[:], SS2[:], SS[:])
	if rtn != 0 {
		fmt.Println("MPIN_RECOMBINE_G2(SS1, SS2, SS) Error:", rtn)
		return
	}
	fmt.Printf("SS: 0x")
	amcl.MPIN_printBinary(SS[:])

	// Generate client secret share 1
	amcl.MPIN_GET_CLIENT_SECRET(MS1[:], HCID, CS1[:])
	fmt.Printf("Client Secret CS: 0x")
	amcl.MPIN_printBinary(CS1[:])

	// Generate client secret share 2
	amcl.MPIN_GET_CLIENT_SECRET(MS2[:], HCID, CS2[:])
	fmt.Printf("Client Secret CS: 0x")
	amcl.MPIN_printBinary(CS2[:])

	// Combine client secret shares : TOKEN is the full client secret
	rtn = amcl.MPIN_RECOMBINE_G1(CS1[:], CS2[:], TOKEN[:])
	if rtn != 0 {
		fmt.Println("MPIN_RECOMBINE_G1(CS1, CS2, TOKEN) Error:", rtn)
		return
	}

	// Generate time permit share 1
	amcl.MPIN_GET_CLIENT_PERMIT(date, MS1[:], HCID, TP1[:])
	fmt.Printf("TP1: 0x")
	amcl.MPIN_printBinary(TP1[:])

	// Generate time permit share 2
	amcl.MPIN_GET_CLIENT_PERMIT(date, MS2[:], HCID, TP2[:])
	fmt.Printf("TP2: 0x")
	amcl.MPIN_printBinary(TP2[:])

	// Combine time permit shares
	rtn = amcl.MPIN_RECOMBINE_G1(TP1[:], TP2[:], TP[:])
	if rtn != 0 {
		fmt.Println("MPIN_RECOMBINE_G1(TP1, TP2, TP) Error:", rtn)
		return
	}

	// Client extracts PIN1 from secret to create Token
	for PIN1 < 0 {
		fmt.Printf("Please enter PIN to create token: ")
		fmt.Scan(&PIN1)
	}

	rtn = amcl.MPIN_EXTRACT_PIN(ID, PIN1, TOKEN[:])
	if rtn != 0 {
		fmt.Printf("FAILURE: EXTRACT_PIN rtn: %d\n", rtn)
		return
	}
	fmt.Printf("Client Token TK: 0x")
	amcl.MPIN_printBinary(TOKEN[:])

	for PIN2 < 0 {
		fmt.Printf("Please enter PIN to authenticate: ")
		fmt.Scan(&PIN2)
	}

	/* Clients first pass. Calculate U and UT */
	rtn = amcl.MPIN_CLIENT_1(date, ID, rng, X[:], PIN2, TOKEN[:], SEC[:], U[:], UT[:], TP[:])
	if rtn != 0 {
		fmt.Printf("FAILURE: CLIENT rtn: %d\n", rtn)
		return
	}

	/* Server first pass. Calculate H(ID) and H(T|H(ID)) (if time permits enabled), and maps them to points on the curve HID and HTID resp. */
	amcl.MPIN_SERVER_1(date, ID, HID[:], HTID[:])

	/* Server generates Random number Y and sends it to Client */
	amcl.MPIN_RANDOM_GENERATE(rng, Y[:])

	/* Client Second Pass: Inputs Client secret SEC, x and y. Outputs -(x+y)*SEC */
	rtn = amcl.MPIN_CLIENT_2(X[:], Y[:], SEC[:])
	if rtn != 0 {
		fmt.Printf("FAILURE: CLIENT_2 rtn: %d\n", rtn)
	}

	/* Server Second pass. Inputs hashed client id, random Y, -(x+y)*SEC, xID and xCID and Server secret SST. E and F help kangaroos to find error. */
	/* If PIN error not required, set E and F = null */
	rtn = amcl.MPIN_SERVER_2(date, HID[:], HTID[:], Y[:], SS[:], U[:], UT[:], SEC[:], E[:], F[:])
	if rtn != 0 {
		fmt.Printf("FAILURE: MPIN_SERVER_2 rtn: %d\n", rtn)
	}
	fmt.Printf("HID: 0x")
	amcl.MPIN_printBinary(HID[:])
	fmt.Printf("HTID: 0x")
	amcl.MPIN_printBinary(HTID[:])

	if rtn == amcl.MPIN_BAD_PIN {
		fmt.Printf("Authentication failed Error Code %d\n", rtn)
		err := amcl.MPIN_KANGAROO(E[:], F[:])
		if err != 0 {
			fmt.Printf("PIN Error %d\n", err)
		}
		return
	} else {
		fmt.Printf("Authenticated ID: %s \n", IDstr)
	}
}