/*
 * Copyright 2024, gRPC Authors All rights reserved.
 *
 * 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.
 */

public enum TLSConfig: Sendable {
  /// The serialization format of the provided certificates and private keys.
  public struct SerializationFormat: Sendable, Equatable {
    package enum Wrapped {
      case pem
      case der
    }

    package let wrapped: Wrapped

    public static let pem = Self(wrapped: .pem)
    public static let der = Self(wrapped: .der)
  }

  /// A description of where a certificate is coming from: either a byte array or a file.
  /// The serialization format is specified by ``TLSConfig/SerializationFormat``.
  public struct CertificateSource: Sendable {
    package enum Wrapped {
      case file(path: String, format: SerializationFormat)
      case bytes(bytes: [UInt8], format: SerializationFormat)
    }

    package let wrapped: Wrapped

    /// The certificate's source is a file.
    /// - Parameters:
    ///   - path: The file path containing the certificate.
    ///   - format: The certificate's format, as a ``TLSConfig/SerializationFormat``.
    /// - Returns: A source describing the certificate source is the given file.
    public static func file(path: String, format: SerializationFormat) -> Self {
      Self(wrapped: .file(path: path, format: format))
    }

    /// The certificate's source is an array of bytes.
    /// - Parameters:
    ///   - bytes: The array of bytes making up the certificate.
    ///   - format: The certificate's format, as a ``TLSConfig/SerializationFormat``.
    /// - Returns: A source describing the certificate source is the given bytes.
    public static func bytes(_ bytes: [UInt8], format: SerializationFormat) -> Self {
      Self(wrapped: .bytes(bytes: bytes, format: format))
    }
  }

  /// A description of where the private key is coming from: either a byte array or a file.
  /// The serialization format is specified by ``TLSConfig/SerializationFormat``.
  public struct PrivateKeySource: Sendable {
    package enum Wrapped {
      case file(path: String, format: SerializationFormat)
      case bytes(bytes: [UInt8], format: SerializationFormat)
    }

    package let wrapped: Wrapped

    /// The private key's source is a file.
    /// - Parameters:
    ///   - path: The file path containing the private key.
    ///   - format: The private key's format, as a ``TLSConfig/SerializationFormat``.
    /// - Returns: A source describing the private key source is the given file.
    public static func file(path: String, format: SerializationFormat) -> Self {
      Self(wrapped: .file(path: path, format: format))
    }

    /// The private key's source is an array of bytes.
    /// - Parameters:
    ///   - bytes: The array of bytes making up the private key.
    ///   - format: The private key's format, as a ``TLSConfig/SerializationFormat``.
    /// - Returns: A source describing the private key source is the given bytes.
    public static func bytes(
      _ bytes: [UInt8],
      format: SerializationFormat
    ) -> Self {
      Self(wrapped: .bytes(bytes: bytes, format: format))
    }
  }

  /// A description of where the trust roots are coming from: either a custom certificate chain, or the system default trust store.
  public struct TrustRootsSource: Sendable {
    package enum Wrapped {
      case certificates([CertificateSource])
      case systemDefault
    }

    package let wrapped: Wrapped

    /// A list of ``TLSConfig/CertificateSource``s making up the
    /// chain of trust.
    /// - Parameter certificateSources: The sources for the certificates that make up the chain of trust.
    /// - Returns: A trust root for the given chain of trust.
    public static func certificates(
      _ certificateSources: [CertificateSource]
    ) -> Self {
      Self(wrapped: .certificates(certificateSources))
    }

    /// The system default trust store.
    public static let systemDefault: Self = Self(wrapped: .systemDefault)
  }

  /// How to verify client certificates.
  public struct CertificateVerification: Sendable {
    package enum Wrapped {
      case doNotVerify
      case fullVerification
      case noHostnameVerification
    }

    package let wrapped: Wrapped

    /// All certificate verification disabled.
    public static let noVerification: Self = Self(wrapped: .doNotVerify)

    /// Certificates will be validated against the trust store, but will not be checked to see if they are valid for the given hostname.
    public static let noHostnameVerification: Self = Self(wrapped: .noHostnameVerification)

    /// Certificates will be validated against the trust store and checked against the hostname of the service we are contacting.
    public static let fullVerification: Self = Self(wrapped: .fullVerification)
  }
}

@available(macOS 15.0, iOS 18.0, watchOS 11.0, tvOS 18.0, visionOS 2.0, *)
extension HTTP2ServerTransport.Posix.Config {
  /// The security configuration for this connection.
  public struct TransportSecurity: Sendable {
    package enum Wrapped: Sendable {
      case plaintext
      case tls(TLS)
    }

    package let wrapped: Wrapped

    /// This connection is plaintext: no encryption will take place.
    public static let plaintext = Self(wrapped: .plaintext)

    #if canImport(NIOSSL)
    /// This connection will use TLS.
    public static func tls(_ tls: TLS) -> Self {
      Self(wrapped: .tls(tls))
    }
    #endif
  }

  public struct TLS: Sendable {
    /// The certificates the server will offer during negotiation.
    public var certificateChain: [TLSConfig.CertificateSource]

    /// The private key associated with the leaf certificate.
    public var privateKey: TLSConfig.PrivateKeySource

    /// How to verify the client certificate, if one is presented.
    public var clientCertificateVerification: TLSConfig.CertificateVerification

    /// The trust roots to be used when verifying client certificates.
    public var trustRoots: TLSConfig.TrustRootsSource

    /// Whether ALPN is required.
    ///
    /// If this is set to `true` but the client does not support ALPN, then the connection will be rejected.
    public var requireALPN: Bool

    /// Create a new HTTP2 NIO Posix transport TLS config, with some values defaulted:
    /// - `clientCertificateVerificationMode` equals `doNotVerify`
    /// - `trustRoots` equals `systemDefault`
    /// - `requireALPN` equals `false`
    ///
    /// - Parameters:
    ///   - certificateChain: The certificates the server will offer during negotiation.
    ///   - privateKey: The private key associated with the leaf certificate.
    /// - Returns: A new HTTP2 NIO Posix transport TLS config.
    public static func defaults(
      certificateChain: [TLSConfig.CertificateSource],
      privateKey: TLSConfig.PrivateKeySource
    ) -> Self {
      Self(
        certificateChain: certificateChain,
        privateKey: privateKey,
        clientCertificateVerification: .noVerification,
        trustRoots: .systemDefault,
        requireALPN: false
      )
    }

    /// Create a new HTTP2 NIO Posix transport TLS config, with some values defaulted to match
    /// the requirements of mTLS:
    /// - `clientCertificateVerificationMode` equals `noHostnameVerification`
    /// - `trustRoots` equals `systemDefault`
    /// - `requireALPN` equals `false`
    ///
    /// - Parameters:
    ///   - certificateChain: The certificates the server will offer during negotiation.
    ///   - privateKey: The private key associated with the leaf certificate.
    /// - Returns: A new HTTP2 NIO Posix transport TLS config.
    public static func mTLS(
      certificateChain: [TLSConfig.CertificateSource],
      privateKey: TLSConfig.PrivateKeySource
    ) -> Self {
      Self(
        certificateChain: certificateChain,
        privateKey: privateKey,
        clientCertificateVerification: .noHostnameVerification,
        trustRoots: .systemDefault,
        requireALPN: false
      )
    }
  }
}

@available(macOS 15.0, iOS 18.0, watchOS 11.0, tvOS 18.0, visionOS 2.0, *)
extension HTTP2ClientTransport.Posix.Config {
  /// The security configuration for this connection.
  public struct TransportSecurity: Sendable {
    package enum Wrapped: Sendable {
      case plaintext
      case tls(TLS)
    }

    package let wrapped: Wrapped

    /// This connection is plaintext: no encryption will take place.
    public static let plaintext = Self(wrapped: .plaintext)

    #if canImport(NIOSSL)
    /// This connection will use TLS.
    public static func tls(_ tls: TLS) -> Self {
      Self(wrapped: .tls(tls))
    }
    #endif
  }

  public struct TLS: Sendable {
    /// The certificates the client will offer during negotiation.
    public var certificateChain: [TLSConfig.CertificateSource]

    /// The private key associated with the leaf certificate.
    public var privateKey: TLSConfig.PrivateKeySource?

    /// How to verify the server certificate, if one is presented.
    public var serverCertificateVerification: TLSConfig.CertificateVerification

    /// The trust roots to be used when verifying server certificates.
    public var trustRoots: TLSConfig.TrustRootsSource

    /// An optional server hostname to use when verifying certificates.
    public var serverHostname: String?

    /// Create a new HTTP2 NIO Posix transport TLS config, with some values defaulted:
    /// - `certificateChain` equals `[]`
    /// - `privateKey` equals `nil`
    /// - `serverCertificateVerification` equals `fullVerification`
    /// - `trustRoots` equals `systemDefault`
    /// - `serverHostname` equals `nil`
    ///
    /// - Returns: A new HTTP2 NIO Posix transport TLS config.
    public static var defaults: Self {
      Self(
        certificateChain: [],
        privateKey: nil,
        serverCertificateVerification: .fullVerification,
        trustRoots: .systemDefault,
        serverHostname: nil
      )
    }

    /// Create a new HTTP2 NIO Posix transport TLS config, with some values defaulted to match
    /// the requirements of mTLS:
    /// - `trustRoots` equals `systemDefault`
    ///
    /// - Parameters:
    ///   - certificateChain: The certificates the client will offer during negotiation.
    ///   - privateKey: The private key associated with the leaf certificate.
    /// - Returns: A new HTTP2 NIO Posix transport TLS config.
    public static func mTLS(
      certificateChain: [TLSConfig.CertificateSource],
      privateKey: TLSConfig.PrivateKeySource
    ) -> Self {
      Self(
        certificateChain: certificateChain,
        privateKey: privateKey,
        serverCertificateVerification: .fullVerification,
        trustRoots: .systemDefault
      )
    }
  }
}