session-ios/SessionSnodeKit/Models/SendMessageRequest.swift

// Copyright © 2022 Rangeproof Pty Ltd. All rights reserved.

import Foundation

extension SnodeAPI {
    public class SendMessageRequest: SnodeAuthenticatedRequestBody {
        enum CodingKeys: String, CodingKey {
            case namespace
            case signatureTimestamp = "timestamp"//"sig_timestamp"  // TODO: Add this back once the snodes are fixed
        }
        
        let message: SnodeMessage
        let namespace: SnodeAPI.Namespace
        
        // MARK: - Init
        
        public init(
            message: SnodeMessage,
            namespace: SnodeAPI.Namespace,
            subkey: String?,
            timestampMs: UInt64,
            ed25519PublicKey: [UInt8],
            ed25519SecretKey: [UInt8]
        ) {
            self.message = message
            self.namespace = namespace
            
            super.init(
                pubkey: message.recipient,
                ed25519PublicKey: ed25519PublicKey,
                ed25519SecretKey: ed25519SecretKey,
                subkey: subkey,
                timestampMs: timestampMs
            )
        }
        
        // MARK: - Coding
        
        override public func encode(to encoder: Encoder) throws {
            var container: KeyedEncodingContainer<CodingKeys> = encoder.container(keyedBy: CodingKeys.self)
            
            try super.encode(to: encoder)
            
            /// **Note:** We **MUST** do the `message.encode` after we call `super.encode` because it will
            /// override the `timestampMs` value with the value in the message (if we do it the other way around then
            /// the the API call timestamp will be sent instead which is incorrect. For this specific request type we have a
            /// separate `signatureTimestamp` value to store the timestamp used to generate the signature
            try message.encode(to: encoder)
            try container.encode(namespace, forKey: .namespace)
            try container.encode(timestampMs, forKey: .signatureTimestamp)
        }
        
        // MARK: - Abstract Methods
        
        override func generateSignature() throws -> [UInt8] {
            /// Ed25519 signature of `("store" || namespace || sig_timestamp)`, where namespace and
            /// `sig_timestamp` are the base10 expression of the namespace and `sig_timestamp` values.  Must be
            /// base64 encoded for json requests; binary for OMQ requests.  For non-05 type pubkeys (i.e. non
            /// session ids) the signature will be verified using `pubkey`.  For 05 pubkeys, see the following
            /// option.
            let verificationBytes: [UInt8] = SnodeAPI.Endpoint.sendMessage.rawValue.bytes
                .appending(contentsOf: namespace.verificationString.bytes)
                .appending(contentsOf: timestampMs.map { "\($0)" }?.data(using: .utf8)?.bytes)
            
            guard
                let signatureBytes: [UInt8] = sodium.wrappedValue.sign.signature(
                    message: verificationBytes,
                    secretKey: ed25519SecretKey
                )
            else {
                throw SnodeAPIError.signingFailed
            }
            
            return signatureBytes
        }
    }
}