PostgreSQLMessage+StartupMessage.swift

extension PostgreSQLMessage {
    /// First message sent from the frontend during startup.
    struct StartupMessage {
        /// Creates a `PostgreSQLStartupMessage` with "3.0" as the protocol version.
        static func versionThree(parameters: [String: String]) -> StartupMessage {
            return .init(protocolVersion: 196608, parameters: parameters)
        }
        
        /// The protocol version number. The most significant 16 bits are the major
        /// version number (3 for the protocol described here). The least significant
        /// 16 bits are the minor version number (0 for the protocol described here).
        var protocolVersion: Int32
        
        /// The protocol version number is followed by one or more pairs of parameter
        /// name and value strings. A zero byte is required as a terminator after
        /// the last name/value pair. Parameters can appear in any order. user is required,
        /// others are optional. Each parameter is specified as:
        var parameters: [String: String]
        
        /// Creates a new `PostgreSQLStartupMessage`.
        init(protocolVersion: Int32, parameters: [String: String]) {
            self.protocolVersion = protocolVersion
            self.parameters = parameters
        }
    }
}

// MARK: Serialize

extension PostgreSQLMessage.StartupMessage {
    /// Serializes this message into a byte buffer.
    func serialize(into buffer: inout ByteBuffer) {
        buffer.write(integer: protocolVersion)
        for (key, val) in parameters {
            buffer.write(nullTerminated: key)
            buffer.write(nullTerminated: val)
        }
        // terminator
        buffer.write(nullTerminated: "")
    }
}