//! This is a low level (no_std) crate with the ability to assemble and disassemble MQTT 3.1.1
//! packets and is used by both client and broker. Uses 'bytes' crate internally
#![no_std]

extern crate alloc;

mod packets;
mod read;
mod topic;

use bytes::Buf;
use core::fmt;
use core::fmt::{Display, Formatter};
pub use packets::*;
pub use read::*;
pub use topic::*;

/// Serialization/Deserialization errors
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum Error {
    InvalidConnectReturnCode(u8),
    InvalidProtocol,
    InvalidProtocolLevel(u8),
    IncorrectPacketFormat,
    InvalidPacketType(u8),
    InvalidQoS(u8),
    PacketIdZero,
    PayloadSizeIncorrect,
    PayloadTooLong,
    PayloadSizeLimitExceeded,
    PayloadRequired,
    TopicNotUtf8,
    BoundaryCrossed,
    MalformedRemainingLength,
    InsufficientBytes(usize),
}

/// Encapsulates all MQTT packet types
#[derive(Debug, Clone, PartialEq)]
pub enum Packet {
    Connect(Connect),
    ConnAck(ConnAck),
    Publish(Publish),
    PubAck(PubAck),
    PubRec(PubRec),
    PubRel(PubRel),
    PubComp(PubComp),
    Subscribe(Subscribe),
    SubAck(SubAck),
    Unsubscribe(Unsubscribe),
    UnsubAck(UnsubAck),
    PingReq,
    PingResp,
    Disconnect,
}

/// MQTT packet type
#[repr(u8)]
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum PacketType {
    Connect = 1,
    ConnAck,
    Publish,
    PubAck,
    PubRec,
    PubRel,
    PubComp,
    Subscribe,
    SubAck,
    Unsubscribe,
    UnsubAck,
    PingReq,
    PingResp,
    Disconnect,
}

/// Protocol type
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum Protocol {
    MQTT(u8),
}

/// Quality of service
#[repr(u8)]
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd)]
pub enum QoS {
    AtMostOnce = 0,
    AtLeastOnce = 1,
    ExactlyOnce = 2,
}

/// Packet type from a byte
///
/// ```ignore
///          7                          3                          0
///          +--------------------------+--------------------------+
/// byte 1   | MQTT Control Packet Type | Flags for each type      |
///          +--------------------------+--------------------------+
///          |         Remaining Bytes Len  (1/2/3/4 bytes)        |
///          +-----------------------------------------------------+
///
/// http://docs.oasis-open.org/mqtt/mqtt/v3.1.1/os/mqtt-v3.1.1-os.html#_Figure_2.2_-
/// ```
pub struct FixedHeader {
    /// First byte of the stream. Used to identify packet types and
    /// several flags
    byte1: u8,
    /// Length of fixed header. Byte 1 + (1..4) bytes. So fixed header
    /// len can vary from 2 bytes to 5 bytes
    /// 1..4 bytes are variable length encoded to represent remaining length
    fixed_len: usize,
    /// Remaining length of the packet. Doesn't include fixed header bytes
    /// Represents variable header + payload size
    remaining_len: usize,
}

impl FixedHeader {
    pub fn new(byte1: u8, remaining_len_len: usize, remaining_len: usize) -> FixedHeader {
        FixedHeader {
            byte1,
            fixed_len: remaining_len_len + 1,
            remaining_len,
        }
    }

    pub fn packet_type(&self) -> Result<PacketType, Error> {
        let num = self.byte1 >> 4;
        match num {
            1 => Ok(PacketType::Connect),
            2 => Ok(PacketType::ConnAck),
            3 => Ok(PacketType::Publish),
            4 => Ok(PacketType::PubAck),
            5 => Ok(PacketType::PubRec),
            6 => Ok(PacketType::PubRel),
            7 => Ok(PacketType::PubComp),
            8 => Ok(PacketType::Subscribe),
            9 => Ok(PacketType::SubAck),
            10 => Ok(PacketType::Unsubscribe),
            11 => Ok(PacketType::UnsubAck),
            12 => Ok(PacketType::PingReq),
            13 => Ok(PacketType::PingResp),
            14 => Ok(PacketType::Disconnect),
            _ => Err(Error::InvalidPacketType(num)),
        }
    }

    /// Returns the size of full packet (fixed header + variable header + payload)
    /// Fixed header is enough to get the size of a frame in the stream
    pub fn frame_length(&self) -> usize {
        self.fixed_len + self.remaining_len
    }
}

/// Maps a number to QoS
pub fn qos(num: u8) -> Result<QoS, Error> {
    match num {
        0 => Ok(QoS::AtMostOnce),
        1 => Ok(QoS::AtLeastOnce),
        2 => Ok(QoS::ExactlyOnce),
        qos => Err(Error::InvalidQoS(qos)),
    }
}

impl Display for Error {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        write!(f, "Error = {:?}", self)
    }
}