/*
 * Copyright (c) 2023 New Vector Ltd
 *
 * Licensed 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 io.element.android.libraries.cryptography.impl

import com.squareup.anvil.annotations.ContributesBinding
import io.element.android.libraries.cryptography.api.AESEncryptionSpecs
import io.element.android.libraries.cryptography.api.EncryptionDecryptionService
import io.element.android.libraries.cryptography.api.EncryptionResult
import io.element.android.libraries.di.AppScope
import javax.crypto.Cipher
import javax.crypto.SecretKey
import javax.crypto.spec.GCMParameterSpec
import javax.inject.Inject

/**
 * Default implementation of [EncryptionDecryptionService] using AES encryption.
 */
@ContributesBinding(AppScope::class)
class AESEncryptionDecryptionService @Inject constructor() : EncryptionDecryptionService {
    override fun createEncryptionCipher(key: SecretKey): Cipher {
        return Cipher.getInstance(AESEncryptionSpecs.CIPHER_TRANSFORMATION).apply {
            init(Cipher.ENCRYPT_MODE, key)
        }
    }

    override fun createDecryptionCipher(key: SecretKey, initializationVector: ByteArray): Cipher {
        val spec = GCMParameterSpec(128, initializationVector)
        return Cipher.getInstance(AESEncryptionSpecs.CIPHER_TRANSFORMATION).apply {
            init(Cipher.DECRYPT_MODE, key, spec)
        }
    }

    override fun encrypt(key: SecretKey, input: ByteArray): EncryptionResult {
        val cipher = createEncryptionCipher(key)
        val encryptedData = cipher.doFinal(input)
        return EncryptionResult(encryptedData, cipher.iv)
    }

    override fun decrypt(key: SecretKey, encryptionResult: EncryptionResult): ByteArray {
        val cipher = createDecryptionCipher(key, encryptionResult.initializationVector)
        return cipher.doFinal(encryptionResult.encryptedByteArray)
    }
}
