use std::str::from_utf8;

use chrono::Local;

use crate::{command::RequestSerializer, security::Security};

pub struct PacketBuilder<S: RequestSerializer> {
    command: S,

    packet: [u8; 40],
}

impl<S: RequestSerializer> PacketBuilder<S> {
    pub fn builder(device_id: u64, command: S) -> Self {
        #[rustfmt::skip]
        let mut packet = [
            // 2 bytes - StaicHeader
            0x5a, 0x5a,
            // 2 bytes - mMessageType
            0x01, 0x11,
            // 2 bytes - PacketLenght
            0x00, 0x00,
            // 2 bytes
            0x20, 0x00,
            // 4 bytes - MessageId
            0x00, 0x00, 0x00, 0x00,
            // 8 bytes - Date&Time
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            // 6 bytes - mDeviceID
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            // 12 bytes
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
        ];

        packet[12..20].copy_from_slice(&Self::packet_time());
        packet[20..28].copy_from_slice(&device_id.to_le_bytes()[0..8]);

        Self { command, packet }
    }

    fn packet_time() -> [u8; 8] {
        let mut t = Local::now()
            .format("%Y%m%d%H%M%S%f")
            .to_string()
            .as_bytes()
            .to_vec();
        t.truncate(16);

        let mut b = [0; 8];

        for (index, chars) in t.chunks(2).enumerate() {
            b[7 - index] = from_utf8(chars).unwrap().parse().unwrap();
        }

        b
    }

    pub fn finalize(self, msg_type: u8) -> Vec<u8> {
        let mut packet = self.packet.to_vec();

        if msg_type != 1 {
            packet[3] = 0x10;
            packet[6] = 0x7b;
        } else {
            packet.extend(Security::aes_encrypt(&self.command.serialize()));
        }

        // packet length
        packet[4..6].copy_from_slice(&(self.packet.len() as u16 + 16).to_le_bytes());

        // append a basic checksum data (16 bytes) to the packet
        packet.extend(Security::encode32_data(&self.packet));

        packet
    }
}

#[cfg(test)]
mod test {
    use std::str::from_utf8;

    #[test]
    fn packet_time() {
        let t = b"2023092913400641";
        let b_ref = b")\x06(\r\x1d\t\x17\x14";

        let mut b = [0; 8];

        for (index, chars) in t.chunks(2).enumerate() {
            b[7 - index] = from_utf8(chars).unwrap().parse().unwrap();
        }

        assert_eq!(&b, b_ref);
    }
}