import { AssetProxyId, ERC20AssetData, ERC721AssetData } from '@0xproject/types';
import { BigNumber } from '@0xproject/utils';
import BN = require('bn.js');
import ethUtil = require('ethereumjs-util');

const ERC20_ASSET_DATA_BYTE_LENGTH = 36;
const ERC721_ASSET_DATA_MINIMUM_BYTE_LENGTH = 53;
const ASSET_DATA_ADDRESS_OFFSET = 0;
const ERC721_ASSET_DATA_TOKEN_ID_OFFSET = 20;
const ERC721_ASSET_DATA_RECEIVER_DATA_LENGTH_OFFSET = 52;
const ERC721_ASSET_DATA_RECEIVER_DATA_OFFSET = 84;

// TODO: Push upstream to DefinitelyTyped
interface EthAbi {
    simpleEncode(signature: string, ...args: any[]): Buffer;
    rawDecode(signature: string[], data: Buffer): any[];
}
const ethAbi = require('ethereumjs-abi') as EthAbi;

export const assetProxyUtils = {
    encodeAssetProxyId(assetProxyId: AssetProxyId): Buffer {
        return ethUtil.toBuffer(assetProxyId);
    },
    decodeAssetProxyId(encodedAssetProxyId: Buffer): AssetProxyId {
        const string = ethUtil.bufferToHex(encodedAssetProxyId);
        if (string === AssetProxyId.ERC20) {
            return AssetProxyId.ERC20;
        }
        if (string === AssetProxyId.ERC721) {
            return AssetProxyId.ERC721;
        }
        throw new Error(`Invalid ProxyId: ${string}`);
    },
    encodeAddress(address: string): Buffer {
        if (!ethUtil.isValidAddress(address)) {
            throw new Error(`Invalid Address: ${address}`);
        }
        const encodedAddress = ethUtil.toBuffer(address);
        const padded = ethUtil.setLengthLeft(encodedAddress, 32);
        return padded;
    },
    decodeAddress(encodedAddress: Buffer): string {
        const unpadded = ethUtil.setLengthLeft(encodedAddress, 20);
        const address = ethUtil.bufferToHex(unpadded);
        if (!ethUtil.isValidAddress(address)) {
            throw new Error(`Invalid Address: ${address}`);
        }
        return address;
    },
    encodeUint256(value: BigNumber): Buffer {
        const base = 10;
        const formattedValue = new BN(value.toString(base));
        const encodedValue = ethUtil.toBuffer(formattedValue);
        // tslint:disable-next-line:custom-no-magic-numbers
        const paddedValue = ethUtil.setLengthLeft(encodedValue, 32);
        return paddedValue;
    },
    decodeUint256(encodedValue: Buffer): BigNumber {
        const formattedValue = ethUtil.bufferToHex(encodedValue);
        const value = new BigNumber(formattedValue, 16);
        return value;
    },
    encodeERC20AssetData(tokenAddress: string): string {
        return ethUtil.bufferToHex(ethAbi.simpleEncode(
            'ERC20Token(address)',
            tokenAddress,
        ));
    },
    decodeERC20AssetData(assetData: string): ERC20AssetData {
        const data = ethUtil.toBuffer(assetData);
        if (data.byteLength < ERC20_ASSET_DATA_BYTE_LENGTH) {
            throw new Error(
                `Could not decode ERC20 Proxy Data. Expected length of encoded data to be at least ${ERC20_ASSET_DATA_BYTE_LENGTH}. Got ${data.byteLength}`,
            );
        }
        const assetProxyId = ethUtil.bufferToHex(data.slice(0, 4));
        if (assetProxyId !== AssetProxyId.ERC20) {
            throw new Error(
                `Could not decode ERC20 Proxy Data. Expected Asset Proxy Id to be ERC20 (${AssetProxyId.ERC20}), but got ${assetProxyId}`,
            );
        }
        const [tokenAddress] = ethAbi.rawDecode(['address'], data.slice(4));
        return {
            assetProxyId,
            tokenAddress: ethUtil.addHexPrefix(tokenAddress),
        };
    },
    encodeERC721AssetData(tokenAddress: string, tokenId: BigNumber, receiverData?: string): string {
        // TODO: Pass `tokendId` as a BigNumber.
        return ethUtil.bufferToHex(ethAbi.simpleEncode(
            'ERC721Token(address,uint256,bytes)',
            tokenAddress,
            tokenId.toString(16),
            ethUtil.toBuffer(receiverData || '0x'),
        ));
    },
    decodeERC721AssetData(assetData: string): ERC721AssetData {
        const data = ethUtil.toBuffer(assetData);
        if (data.byteLength < ERC721_ASSET_DATA_MINIMUM_BYTE_LENGTH) {
            throw new Error(
                `Could not decode ERC721 Asset Data. Expected length of encoded data to be at least ${ERC721_ASSET_DATA_MINIMUM_BYTE_LENGTH}. Got ${data.byteLength}`,
            );
        }
        const assetProxyId = ethUtil.bufferToHex(data.slice(0, 4));
        if (assetProxyId !== AssetProxyId.ERC721) {
            throw new Error(
                `Could not decode ERC721 Asset Data. Expected Asset Proxy Id to be ERC721 (${AssetProxyId.ERC721}), but got ${assetProxyId}`,
            );
        }
        const [tokenAddress, tokenId, receiverData] = ethAbi.rawDecode(
            ['address', 'uint256', 'bytes'],
            data.slice(4),
        );
        return {
            assetProxyId,
            tokenAddress: ethUtil.addHexPrefix(tokenAddress),
            tokenId: new BigNumber(tokenId.toString()),
            receiverData: ethUtil.bufferToHex(receiverData),
        };
    },
    decodeAssetDataId(assetData: string): AssetProxyId {
        const encodedAssetData = ethUtil.toBuffer(assetData);
        if (encodedAssetData.byteLength < 4) {
            throw new Error(
                `Could not decode Proxy Data. Expected length of encoded data to be at least 4. Got ${encodedAssetData.byteLength}`,
            );
        }
        const encodedAssetProxyId = encodedAssetData.slice(0, 4);
        const assetProxyId = assetProxyUtils.decodeAssetProxyId(encodedAssetProxyId);
        return assetProxyId;
    },
    decodeAssetData(assetData: string): ERC20AssetData | ERC721AssetData {
        const assetProxyId = assetProxyUtils.decodeAssetDataId(assetData);
        switch (assetProxyId) {
            case AssetProxyId.ERC20:
                const erc20AssetData = assetProxyUtils.decodeERC20AssetData(assetData);
                return erc20AssetData;
            case AssetProxyId.ERC721:
                const erc721AssetData = assetProxyUtils.decodeERC721AssetData(assetData);
                return erc721AssetData;
            default:
                throw new Error(`Unrecognized asset proxy id: ${assetProxyId}`);
        }
    },
};