import Foundation

final class RTMPHandshake {
    static let sigSize: Int = 1536
    static let protocolVersion: UInt8 = 3

    var timestamp: TimeInterval = 0

    var c0c1packet: Data {
        let packet: ByteArray = ByteArray()
            .writeUInt8(RTMPHandshake.protocolVersion)
            .writeInt32(Int32(timestamp))
            .writeBytes(Data([0x00, 0x00, 0x00, 0x00]))
        for _ in 0..<RTMPHandshake.sigSize - 8 {
            packet.writeUInt8(UInt8(arc4random_uniform(0xff)))
        }
        return packet.data
    }

    func c2packet(_ s0s1packet: Data) -> Data {
        return ByteArray()
            .writeBytes(s0s1packet.subdata(in: 1..<5))
            .writeInt32(Int32(Date().timeIntervalSince1970 - timestamp))
            .writeBytes(s0s1packet.subdata(in: 9..<RTMPHandshake.sigSize + 1))
            .data
    }

    func clear() {
        timestamp = 0
    }
}