var BITCOIN_MAINNET_PUBLIC = 0x0488b21e;
var BITCOIN_MAINNET_PRIVATE = 0x0488ade4;
var BITCOIN_TESTNET_PUBLIC = 0x043587cf;
var BITCOIN_TESTNET_PRIVATE = 0x04358394;
var DOGECOIN_MAINNET_PUBLIC = 0x02facafd;
var DOGECOIN_MAINNET_PRIVATE = 0x02fac398;
var DOGECOIN_TESTNET_PUBLIC = 0x0432a9a8;
var DOGECOIN_TESTNET_PRIVATE = 0x0432a243;
var LITECOIN_MAINNET_PUBLIC = 0x019da462;
var LITECOIN_MAINNET_PRIVATE = 0x019d9cfe;
var LITECOIN_TESTNET_PUBLIC = 0x0436f6e1;
var LITECOIN_TESTNET_PRIVATE = 0x0436ef7d;

var BIP32 = function(bytes) {
    // decode base58
    if( typeof bytes === "string" ) {
        var decoded = Bitcoin.Base58.decode(bytes);
        if( decoded.length != 82 ) throw new Error("Not enough data");
        var checksum = decoded.slice(78, 82);
        bytes = decoded.slice(0, 78);

        var hash = Crypto.SHA256( Crypto.SHA256( bytes, { asBytes: true } ), { asBytes: true } );

        if( hash[0] != checksum[0] || hash[1] != checksum[1] || hash[2] != checksum[2] || hash[3] != checksum[3] ) {
            throw new Error("Invalid checksum");
        }
    }

    if( bytes !== undefined ) 
        this.init_from_bytes(bytes);
}

BIP32.prototype.init_from_bytes = function(bytes) {
    // Both pub and private extended keys are 78 bytes
    if( bytes.length != 78 ) throw new Error("not enough data");

    this.version            = u32(bytes.slice(0, 4));
    this.depth              = u8 (bytes.slice(4, 5));
    this.parent_fingerprint = bytes.slice(5, 9);
    this.child_index        = u32(bytes.slice(9, 13));
    this.chain_code         = bytes.slice(13, 45);
    
    var key_bytes = bytes.slice(45, 78);

    var is_private = 
        (this.version == BITCOIN_MAINNET_PRIVATE  ||
         this.version == BITCOIN_TESTNET_PRIVATE  ||
         this.version == DOGECOIN_MAINNET_PRIVATE ||
         this.version == DOGECOIN_TESTNET_PRIVATE ||
         this.version == LITECOIN_MAINNET_PRIVATE ||
         this.version == LITECOIN_TESTNET_PRIVATE );

    var is_public = 
        (this.version == BITCOIN_MAINNET_PUBLIC  ||
         this.version == BITCOIN_TESTNET_PUBLIC  ||
         this.version == DOGECOIN_MAINNET_PUBLIC ||
         this.version == DOGECOIN_TESTNET_PUBLIC ||
         this.version == LITECOIN_MAINNET_PUBLIC ||
         this.version == LITECOIN_TESTNET_PUBLIC );

    if( is_private && key_bytes[0] == 0 ) {
        this.eckey = new Bitcoin.ECKey(key_bytes.slice(1, 33));
        this.eckey.setCompressed(true);

        var ecparams = getSECCurveByName("secp256k1");
        var pt = ecparams.getG().multiply(this.eckey.priv);
        this.eckey.pub = pt;
        this.eckey.pubKeyHash = Bitcoin.Util.sha256ripe160(this.eckey.pub.getEncoded(true));
        this.has_private_key = true;
    } else if( is_public && (key_bytes[0] == 0x02 || key_bytes[0] == 0x03) ) {
        this.eckey = new Bitcoin.ECKey();
        this.eckey.pub = decompress_pubkey(key_bytes);
        this.eckey.pubKeyHash = Bitcoin.Util.sha256ripe160(this.eckey.pub.getEncoded(true));
        this.eckey.setCompressed(true);
        this.has_private_key = false;
    } else {
        throw new Error("Invalid key");
    }

    this.build_extended_public_key();
    this.build_extended_private_key();
}

BIP32.prototype.build_extended_public_key = function() {
    this.extended_public_key = [];

    var v = null;
    switch(this.version) {
    case BITCOIN_MAINNET_PUBLIC:
    case BITCOIN_MAINNET_PRIVATE:
        v = BITCOIN_MAINNET_PUBLIC;
        break;
    case BITCOIN_TESTNET_PUBLIC:
    case BITCOIN_TESTNET_PRIVATE:
        v = BITCOIN_TESTNET_PUBLIC;
        break;
    case DOGECOIN_MAINNET_PUBLIC:
    case DOGECOIN_MAINNET_PRIVATE:
        v = DOGECOIN_MAINNET_PUBLIC;
        break;
    case DOGECOIN_TESTNET_PUBLIC:
    case DOGECOIN_TESTNET_PRIVATE:
        v = DOGECOIN_TESTNET_PUBLIC;
        break;
    case LITECOIN_MAINNET_PUBLIC:
    case LITECOIN_MAINNET_PRIVATE:
        v = LITECOIN_MAINNET_PUBLIC;
        break;
    case LITECOIN_TESTNET_PUBLIC:
    case LITECOIN_TESTNET_PRIVATE:
        v = LITECOIN_TESTNET_PUBLIC;
        break;
     default:
        throw new Error("Unknown version");
    }

    // Version
    this.extended_public_key.push(v >> 24);
    this.extended_public_key.push((v >> 16) & 0xff);
    this.extended_public_key.push((v >> 8) & 0xff);
    this.extended_public_key.push(v & 0xff);

    // Depth
    this.extended_public_key.push(this.depth);

    // Parent fingerprint
    this.extended_public_key = this.extended_public_key.concat(this.parent_fingerprint);

    // Child index
    this.extended_public_key.push(this.child_index >>> 24);
    this.extended_public_key.push((this.child_index >>> 16) & 0xff);
    this.extended_public_key.push((this.child_index >>> 8) & 0xff);
    this.extended_public_key.push(this.child_index & 0xff);

    // Chain code
    this.extended_public_key = this.extended_public_key.concat(this.chain_code);

    // Public key
    this.extended_public_key = this.extended_public_key.concat(this.eckey.pub.getEncoded(true));
}

BIP32.prototype.extended_public_key_string = function(format) {
    if( format === undefined || format === "base58" ) {
        var hash = Crypto.SHA256( Crypto.SHA256( this.extended_public_key, { asBytes: true } ), { asBytes: true } );
        var checksum = hash.slice(0, 4);
        var data = this.extended_public_key.concat(checksum);
        return Bitcoin.Base58.encode(data);
    } else if( format === "hex" ) {
        return Crypto.util.bytesToHex(this.extended_public_key);
    } else {
        throw new Error("bad format");
    }
}

BIP32.prototype.build_extended_private_key = function() {
    if( !this.has_private_key ) return;
    this.extended_private_key = [];

    var v = this.version;

    // Version
    this.extended_private_key.push(v >> 24);
    this.extended_private_key.push((v >> 16) & 0xff);
    this.extended_private_key.push((v >> 8) & 0xff);
    this.extended_private_key.push(v & 0xff);

    // Depth
    this.extended_private_key.push(this.depth);

    // Parent fingerprint
    this.extended_private_key = this.extended_private_key.concat(this.parent_fingerprint);

    // Child index
    this.extended_private_key.push(this.child_index >>> 24);
    this.extended_private_key.push((this.child_index >>> 16) & 0xff);
    this.extended_private_key.push((this.child_index >>> 8) & 0xff);
    this.extended_private_key.push(this.child_index & 0xff);

    // Chain code
    this.extended_private_key = this.extended_private_key.concat(this.chain_code);

    // Private key
    this.extended_private_key.push(0);
    this.extended_private_key = this.extended_private_key.concat(this.eckey.priv.toByteArrayUnsigned());
}

BIP32.prototype.extended_private_key_string = function(format) {
    if( format === undefined || format === "base58" ) {
        var hash = Crypto.SHA256( Crypto.SHA256( this.extended_private_key, { asBytes: true } ), { asBytes: true } );
        var checksum = hash.slice(0, 4);
        var data = this.extended_private_key.concat(checksum);
        return Bitcoin.Base58.encode(data);
    } else if( format === "hex" ) {
        return Crypto.util.bytesToHex(this.extended_private_key);
    } else {
        throw new Error("bad format");
    }
}


BIP32.prototype.derive = function(path) {
    var e = path.split('/');

    // Special cases:
    if( path == 'm' || path == 'M' || path == 'm\'' || path == 'M\'' ) return this;

    var bip32 = this;
    for( var i in e ) {
        var c = e[i];

        if( i == 0 ) {
            if( c != 'm' ) throw new Error("invalid path");
            continue;
        }

        var use_private = (c.length > 1) && (c[c.length-1] == '\'');
        var child_index = parseInt(use_private ? c.slice(0, c.length - 1) : c) & 0x7fffffff;

        if( use_private )
            child_index += 0x80000000;

        bip32 = bip32.derive_child(child_index);
    }

    return bip32;
}

BIP32.prototype.derive_child = function(i) {
    var ib = [];
    ib.push( (i >> 24) & 0xff );
    ib.push( (i >> 16) & 0xff );
    ib.push( (i >>  8) & 0xff );
    ib.push( i & 0xff );

    var use_private = (i & 0x80000000) != 0;
    var ecparams = getSECCurveByName("secp256k1");

    var is_private = 
        (this.version == BITCOIN_MAINNET_PRIVATE  ||
         this.version == BITCOIN_TESTNET_PRIVATE  ||
         this.version == DOGECOIN_MAINNET_PRIVATE ||
         this.version == DOGECOIN_TESTNET_PRIVATE ||
         this.version == LITECOIN_MAINNET_PRIVATE ||
         this.version == LITECOIN_TESTNET_PRIVATE);

    if( use_private && (!this.has_private_key || !is_private) ) throw new Error("Cannot do private key derivation without private key");

    var ret = null;
    if( this.has_private_key ) {
        var data = null;

        if( use_private ) {
            data = [0].concat(this.eckey.priv.toByteArrayUnsigned()).concat(ib);
        } else {
            data = this.eckey.pub.getEncoded(true).concat(ib);
        }

        var j = new jsSHA(Crypto.util.bytesToHex(data), 'HEX');   
        var hash = j.getHMAC(Crypto.util.bytesToHex(this.chain_code), "HEX", "SHA-512", "HEX");
        var il = new BigInteger(hash.slice(0, 64), 16);
        var ir = Crypto.util.hexToBytes(hash.slice(64, 128));

        // ki = IL + kpar (mod n).
        var curve = ecparams.getCurve();
        var k = il.add(this.eckey.priv).mod(ecparams.getN());

        ret = new BIP32();
        ret.chain_code  = ir;

        ret.eckey = new Bitcoin.ECKey(k.toByteArrayUnsigned());
        ret.eckey.pub = ret.eckey.getPubPoint();
        ret.has_private_key = true;

    } else {
        var data = this.eckey.pub.getEncoded(true).concat(ib);
        var j = new jsSHA(Crypto.util.bytesToHex(data), 'HEX');   
        var hash = j.getHMAC(Crypto.util.bytesToHex(this.chain_code), "HEX", "SHA-512", "HEX");
        var il = new BigInteger(hash.slice(0, 64), 16);
        var ir = Crypto.util.hexToBytes(hash.slice(64, 128));

        // Ki = (IL + kpar)*G = IL*G + Kpar
        var k = ecparams.getG().multiply(il).add(this.eckey.pub);

        ret = new BIP32();
        ret.chain_code  = ir;

        ret.eckey = new Bitcoin.ECKey();
        ret.eckey.pub = k;
        ret.has_private_key = false;
    }

    ret.child_index = i;
    ret.parent_fingerprint = this.eckey.pubKeyHash.slice(0,4);
    ret.version = this.version;
    ret.depth   = this.depth + 1;

    ret.eckey.setCompressed(true);
    ret.eckey.pubKeyHash = Bitcoin.Util.sha256ripe160(ret.eckey.pub.getEncoded(true));

    ret.build_extended_public_key();
    ret.build_extended_private_key();

    return ret;
}


function uint(f, size) {
    if (f.length < size)
        throw new Error("not enough data");
    var n = 0;
    for (var i = 0; i < size; i++) {
        n *= 256;
        n += f[i];
    }
    return n;
}

function u8(f)  { return uint(f,1); }
function u16(f) { return uint(f,2); }
function u32(f) { return uint(f,4); }
function u64(f) { return uint(f,8); }

function decompress_pubkey(key_bytes) {
    var y_bit = u8(key_bytes.slice(0, 1)) & 0x01;
    var ecparams = getSECCurveByName("secp256k1");

    // build X
    var x     = BigInteger.ZERO.clone();
    x.fromString(Crypto.util.bytesToHex(key_bytes.slice(1, 33)), 16);
    
    // get curve
    var curve = ecparams.getCurve();
    var a = curve.getA().toBigInteger();
    var b = curve.getB().toBigInteger();
    var p = curve.getQ();
    
    // compute y^2 = x^3 + a*x + b
    var tmp = x.multiply(x).multiply(x).add(a.multiply(x)).add(b).mod(p);
    
    // compute modular square root of y (mod p)
    var y = tmp.modSqrt(p);
    
    // flip sign if we need to
    if( (y[0] & 0x01) != y_bit ) {
        y = y.multiply(new BigInteger("-1")).mod(p);
    }
    
    return new ECPointFp(curve, curve.fromBigInteger(x), curve.fromBigInteger(y));
}