import * as forge from 'node-forge';

import { CryptoFunctionService } from '../abstractions/cryptoFunction.service';
import { PlatformUtilsService } from '../abstractions/platformUtils.service';

import { Utils } from '../misc/utils';

import { DecryptParameters } from '../models/domain/decryptParameters';
import { SymmetricCryptoKey } from '../models/domain/symmetricCryptoKey';

export class WebCryptoFunctionService implements CryptoFunctionService {
    private crypto: Crypto;
    private subtle: SubtleCrypto;
    private isEdge: boolean;
    private isIE: boolean;
    private isOldSafari: boolean;

    constructor(private win: Window, private platformUtilsService: PlatformUtilsService) {
        this.crypto = typeof win.crypto !== 'undefined' ? win.crypto : null;
        this.subtle = (!!this.crypto && typeof win.crypto.subtle !== 'undefined') ? win.crypto.subtle : null;
        this.isEdge = platformUtilsService.isEdge();
        this.isIE = platformUtilsService.isIE();
        const ua = win.navigator.userAgent;
        this.isOldSafari = platformUtilsService.isSafari() &&
            (ua.indexOf(' Version/10.') > -1 || ua.indexOf(' Version/9.') > -1);
    }

    async pbkdf2(password: string | ArrayBuffer, salt: string | ArrayBuffer, algorithm: 'sha256' | 'sha512',
        iterations: number): Promise<ArrayBuffer> {
        if (this.isEdge || this.isIE || this.isOldSafari) {
            const forgeLen = algorithm === 'sha256' ? 32 : 64;
            const passwordBytes = this.toByteString(password);
            const saltBytes = this.toByteString(salt);
            const derivedKeyBytes = (forge as any).pbkdf2(passwordBytes, saltBytes, iterations, forgeLen, algorithm);
            return Utils.fromByteStringToArray(derivedKeyBytes).buffer;
        }

        const wcLen = algorithm === 'sha256' ? 256 : 512;
        const passwordBuf = this.toBuf(password);
        const saltBuf = this.toBuf(salt);

        const pbkdf2Params: Pbkdf2Params = {
            name: 'PBKDF2',
            salt: saltBuf,
            iterations: iterations,
            hash: { name: this.toWebCryptoAlgorithm(algorithm) },
        };

        const impKey = await this.subtle.importKey('raw', passwordBuf, { name: 'PBKDF2' } as any,
            false, ['deriveBits']);
        return await this.subtle.deriveBits(pbkdf2Params, impKey, wcLen);
    }

    async hash(value: string | ArrayBuffer, algorithm: 'sha1' | 'sha256' | 'sha512' | 'md5'): Promise<ArrayBuffer> {
        if (((this.isEdge || this.isIE) && algorithm === 'sha1') || algorithm === 'md5') {
            const md = algorithm === 'md5' ? forge.md.md5.create() : forge.md.sha1.create();
            const valueBytes = this.toByteString(value);
            md.update(valueBytes, 'raw');
            return Utils.fromByteStringToArray(md.digest().data).buffer;
        }

        const valueBuf = this.toBuf(value);
        return await this.subtle.digest({ name: this.toWebCryptoAlgorithm(algorithm) }, valueBuf);
    }

    async hmac(value: ArrayBuffer, key: ArrayBuffer, algorithm: 'sha1' | 'sha256' | 'sha512'): Promise<ArrayBuffer> {
        if (this.isIE && algorithm === 'sha512') {
            const hmac = (forge as any).hmac.create();
            const keyBytes = this.toByteString(key);
            const valueBytes = this.toByteString(value);
            hmac.start(algorithm, keyBytes);
            hmac.update(valueBytes, 'raw');
            return Utils.fromByteStringToArray(hmac.digest().data).buffer;
        }

        const signingAlgorithm = {
            name: 'HMAC',
            hash: { name: this.toWebCryptoAlgorithm(algorithm) },
        };

        const impKey = await this.subtle.importKey('raw', key, signingAlgorithm, false, ['sign']);
        return await this.subtle.sign(signingAlgorithm, impKey, value);
    }

    // Safely compare two values in a way that protects against timing attacks (Double HMAC Verification).
    // ref: https://www.nccgroup.trust/us/about-us/newsroom-and-events/blog/2011/february/double-hmac-verification/
    // ref: https://paragonie.com/blog/2015/11/preventing-timing-attacks-on-string-comparison-with-double-hmac-strategy
    async compare(a: ArrayBuffer, b: ArrayBuffer): Promise<boolean> {
        const macKey = await this.randomBytes(32);
        const signingAlgorithm = {
            name: 'HMAC',
            hash: { name: 'SHA-256' },
        };
        const impKey = await this.subtle.importKey('raw', macKey, signingAlgorithm, false, ['sign']);
        const mac1 = await this.subtle.sign(signingAlgorithm, impKey, a);
        const mac2 = await this.subtle.sign(signingAlgorithm, impKey, b);

        if (mac1.byteLength !== mac2.byteLength) {
            return false;
        }

        const arr1 = new Uint8Array(mac1);
        const arr2 = new Uint8Array(mac2);
        for (let i = 0; i < arr2.length; i++) {
            if (arr1[i] !== arr2[i]) {
                return false;
            }
        }

        return true;
    }

    hmacFast(value: string, key: string, algorithm: 'sha1' | 'sha256' | 'sha512'): Promise<string> {
        const hmac = (forge as any).hmac.create();
        hmac.start(algorithm, key);
        hmac.update(value);
        const bytes = hmac.digest().getBytes();
        return Promise.resolve(bytes);
    }

    async compareFast(a: string, b: string): Promise<boolean> {
        const rand = await this.randomBytes(32);
        const bytes = new Uint32Array(rand);
        const buffer = forge.util.createBuffer();
        for (let i = 0; i < bytes.length; i++) {
            buffer.putInt32(bytes[i]);
        }
        const macKey = buffer.getBytes();

        const hmac = (forge as any).hmac.create();
        hmac.start('sha256', macKey);
        hmac.update(a);
        const mac1 = hmac.digest().getBytes();

        hmac.start(null, null);
        hmac.update(b);
        const mac2 = hmac.digest().getBytes();

        const equals = mac1 === mac2;
        return equals;
    }

    async aesEncrypt(data: ArrayBuffer, iv: ArrayBuffer, key: ArrayBuffer): Promise<ArrayBuffer> {
        const impKey = await this.subtle.importKey('raw', key, { name: 'AES-CBC' } as any, false, ['encrypt']);
        return await this.subtle.encrypt({ name: 'AES-CBC', iv: iv }, impKey, data);
    }

    aesDecryptFastParameters(data: string, iv: string, mac: string, key: SymmetricCryptoKey):
        DecryptParameters<string> {
        const p = new DecryptParameters<string>();
        if (key.meta != null) {
            p.encKey = key.meta.encKeyByteString;
            p.macKey = key.meta.macKeyByteString;
        }

        if (p.encKey == null) {
            p.encKey = forge.util.decode64(key.encKeyB64);
        }
        p.data = forge.util.decode64(data);
        p.iv = forge.util.decode64(iv);
        p.macData = p.iv + p.data;
        if (p.macKey == null && key.macKeyB64 != null) {
            p.macKey = forge.util.decode64(key.macKeyB64);
        }
        if (mac != null) {
            p.mac = forge.util.decode64(mac);
        }

        // cache byte string keys for later
        if (key.meta == null) {
            key.meta = {};
        }
        if (key.meta.encKeyByteString == null) {
            key.meta.encKeyByteString = p.encKey;
        }
        if (p.macKey != null && key.meta.macKeyByteString == null) {
            key.meta.macKeyByteString = p.macKey;
        }

        return p;
    }

    aesDecryptFast(parameters: DecryptParameters<string>): Promise<string> {
        const dataBuffer = (forge as any).util.createBuffer(parameters.data);
        const decipher = (forge as any).cipher.createDecipher('AES-CBC', parameters.encKey);
        decipher.start({ iv: parameters.iv });
        decipher.update(dataBuffer);
        decipher.finish();
        const val = decipher.output.toString('utf8');
        return Promise.resolve(val);
    }

    async aesDecrypt(data: ArrayBuffer, iv: ArrayBuffer, key: ArrayBuffer): Promise<ArrayBuffer> {
        const impKey = await this.subtle.importKey('raw', key, { name: 'AES-CBC' } as any, false, ['decrypt']);
        return await this.subtle.decrypt({ name: 'AES-CBC', iv: iv }, impKey, data);
    }

    async rsaEncrypt(data: ArrayBuffer, publicKey: ArrayBuffer, algorithm: 'sha1' | 'sha256'): Promise<ArrayBuffer> {
        // Note: Edge browser requires that we specify name and hash for both key import and decrypt.
        // We cannot use the proper types here.
        const rsaParams = {
            name: 'RSA-OAEP',
            hash: { name: this.toWebCryptoAlgorithm(algorithm) },
        };
        const impKey = await this.subtle.importKey('spki', publicKey, rsaParams, false, ['encrypt']);
        return await this.subtle.encrypt(rsaParams, impKey, data);
    }

    async rsaDecrypt(data: ArrayBuffer, privateKey: ArrayBuffer, algorithm: 'sha1' | 'sha256'): Promise<ArrayBuffer> {
        // Note: Edge browser requires that we specify name and hash for both key import and decrypt.
        // We cannot use the proper types here.
        const rsaParams = {
            name: 'RSA-OAEP',
            hash: { name: this.toWebCryptoAlgorithm(algorithm) },
        };
        const impKey = await this.subtle.importKey('pkcs8', privateKey, rsaParams, false, ['decrypt']);
        return await this.subtle.decrypt(rsaParams, impKey, data);
    }

    async rsaExtractPublicKey(privateKey: ArrayBuffer): Promise<ArrayBuffer> {
        const rsaParams = {
            name: 'RSA-OAEP',
            // Have to specify some algorithm
            hash: { name: this.toWebCryptoAlgorithm('sha1') },
        };
        const impPrivateKey = await this.subtle.importKey('pkcs8', privateKey, rsaParams, true, ['decrypt']);
        const jwkPrivateKey = await this.subtle.exportKey('jwk', impPrivateKey);
        const jwkPublicKeyParams = {
            kty: 'RSA',
            e: jwkPrivateKey.e,
            n: jwkPrivateKey.n,
            alg: 'RSA-OAEP',
            ext: true,
        };
        const impPublicKey = await this.subtle.importKey('jwk', jwkPublicKeyParams, rsaParams, true, ['encrypt']);
        return await this.subtle.exportKey('spki', impPublicKey);
    }

    async rsaGenerateKeyPair(length: 1024 | 2048 | 4096): Promise<[ArrayBuffer, ArrayBuffer]> {
        const rsaParams = {
            name: 'RSA-OAEP',
            modulusLength: length,
            publicExponent: new Uint8Array([0x01, 0x00, 0x01]), // 65537
            // Have to specify some algorithm
            hash: { name: this.toWebCryptoAlgorithm('sha1') },
        };
        const keyPair = await this.subtle.generateKey(rsaParams, true, ['encrypt', 'decrypt']);
        const publicKey = await this.subtle.exportKey('spki', keyPair.publicKey);
        const privateKey = await this.subtle.exportKey('pkcs8', keyPair.privateKey);
        return [publicKey, privateKey];
    }

    randomBytes(length: number): Promise<ArrayBuffer> {
        const arr = new Uint8Array(length);
        this.crypto.getRandomValues(arr);
        return Promise.resolve(arr.buffer);
    }

    private toBuf(value: string | ArrayBuffer): ArrayBuffer {
        let buf: ArrayBuffer;
        if (typeof (value) === 'string') {
            buf = Utils.fromUtf8ToArray(value).buffer;
        } else {
            buf = value;
        }
        return buf;
    }

    private toByteString(value: string | ArrayBuffer): string {
        let bytes: string;
        if (typeof (value) === 'string') {
            bytes = forge.util.encodeUtf8(value);
        } else {
            bytes = Utils.fromBufferToByteString(value);
        }
        return bytes;
    }

    private toWebCryptoAlgorithm(algorithm: 'sha1' | 'sha256' | 'sha512' | 'md5'): string {
        if (algorithm === 'md5') {
            throw new Error('MD5 is not supported in WebCrypto.');
        }
        return algorithm === 'sha1' ? 'SHA-1' : algorithm === 'sha256' ? 'SHA-256' : 'SHA-512';
    }
}