const elliptic = require('elliptic')
const secp256k1 = elliptic.ec('secp256k1')
const hash = require('hash.js')
const keypairs = require('ripple-keypairs')

const hexToDecimal = (x) => secp256k1.keyFromPrivate(x, 'hex').getPrivate().toString(10)

module.exports = {
    sign (message, familySeed) {
        const digest = hash.sha256().update(message).digest('hex').toUpperCase()
        const keypair = keypairs.deriveKeypair(familySeed)
        const signature = secp256k1.sign(digest, keypair.privateKey.substr(2))
        return {
            hash: digest,
            signature: (signature.r.toJSON() + signature.s.toJSON() + signature.recoveryParam.toString(16)).toUpperCase()
        }
    },
    unserializeSignature (signature) {
        return {
            r: signature.slice(0, 64).toLowerCase(),
            s: signature.slice(64, 128).toLowerCase(),
            recoveryParam: parseInt(signature.slice(128), 16)
        }
    },
    deriveAddress (familySeed) {
        const keypair = keypairs.deriveKeypair(familySeed)
        return keypairs.deriveAddress(keypair.publicKey)
    },
    recoverPubKey (hash, signature) {
        const unserializedSignature = this.unserializeSignature(signature)
        const pubKeyRecovered = secp256k1.recoverPubKey(hexToDecimal(hash), unserializedSignature, unserializedSignature.recoveryParam, 'hex')
        return pubKeyRecovered
    },
    recoverAddress (hash, signature) {
        return keypairs.deriveAddress(this.recoverPubKey(hash, signature).encodeCompressed('hex'))
    },
    verify (message, signature) {
        const digest = hash.sha256().update(message).digest('hex')
        const unserializedSignature = this.unserializeSignature(signature)
        return secp256k1.verify(digest, unserializedSignature, this.recoverPubKey(digest, signature))
    }
}