use std::default::Default;
use std::fmt;
use std::io::{ErrorKind, Read, Write};

use byteorder::{BigEndian, ReadBytesExt, WriteBytesExt};
use bytes::Buf;
use rand;

use circular_buffer::CircularBuffer;
use protocol::{CloseCode, OpCode};
use result::{Error, Kind, Result};

fn apply_mask(buf: &mut [u8], mask: &[u8; 4]) {
    let iter = buf.iter_mut().zip(mask.iter().cycle());
    for (byte, &key) in iter {
        *byte ^= key
    }
}

/// A struct representing a WebSocket frame.
#[derive(Debug, Clone)]
pub struct Frame {
    finished: bool,
    rsv1: bool,
    rsv2: bool,
    rsv3: bool,
    opcode: OpCode,

    mask: Option<[u8; 4]>,

    payload: Vec<u8>,
}

impl Frame {
    /// Get the length of the frame.
    /// This is the length of the header + the length of the payload.
    #[inline]
    pub fn len(&self) -> usize {
        let mut header_length = 2;
        let payload_len = self.payload().len();
        if payload_len > 125 {
            if payload_len <= u16::max_value() as usize {
                header_length += 2;
            } else {
                header_length += 8;
            }
        }

        if self.is_masked() {
            header_length += 4;
        }

        header_length + payload_len
    }

    /// Return `false`: a frame is never empty since it has a header.
    #[inline]
    pub fn is_empty(&self) -> bool {
        false
    }

    /// Test whether the frame is a final frame.
    #[inline]
    pub fn is_final(&self) -> bool {
        self.finished
    }

    /// Test whether the first reserved bit is set.
    #[inline]
    pub fn has_rsv1(&self) -> bool {
        self.rsv1
    }

    /// Test whether the second reserved bit is set.
    #[inline]
    pub fn has_rsv2(&self) -> bool {
        self.rsv2
    }

    /// Test whether the third reserved bit is set.
    #[inline]
    pub fn has_rsv3(&self) -> bool {
        self.rsv3
    }

    /// Get the OpCode of the frame.
    #[inline]
    pub fn opcode(&self) -> OpCode {
        self.opcode
    }

    /// Test whether this is a control frame.
    #[inline]
    pub fn is_control(&self) -> bool {
        self.opcode.is_control()
    }

    /// Get a reference to the frame's payload.
    #[inline]
    pub fn payload(&self) -> &Vec<u8> {
        &self.payload
    }

    // Test whether the frame is masked.
    #[doc(hidden)]
    #[inline]
    pub fn is_masked(&self) -> bool {
        self.mask.is_some()
    }

    // Get an optional reference to the frame's mask.
    #[doc(hidden)]
    #[allow(dead_code)]
    #[inline]
    pub fn mask(&self) -> Option<&[u8; 4]> {
        self.mask.as_ref()
    }

    /// Make this frame a final frame.
    #[allow(dead_code)]
    #[inline]
    pub fn set_final(&mut self, is_final: bool) -> &mut Frame {
        self.finished = is_final;
        self
    }

    /// Set the first reserved bit.
    #[inline]
    pub fn set_rsv1(&mut self, has_rsv1: bool) -> &mut Frame {
        self.rsv1 = has_rsv1;
        self
    }

    /// Set the second reserved bit.
    #[inline]
    pub fn set_rsv2(&mut self, has_rsv2: bool) -> &mut Frame {
        self.rsv2 = has_rsv2;
        self
    }

    /// Set the third reserved bit.
    #[inline]
    pub fn set_rsv3(&mut self, has_rsv3: bool) -> &mut Frame {
        self.rsv3 = has_rsv3;
        self
    }

    /// Set the OpCode.
    #[allow(dead_code)]
    #[inline]
    pub fn set_opcode(&mut self, opcode: OpCode) -> &mut Frame {
        self.opcode = opcode;
        self
    }

    /// Edit the frame's payload.
    #[allow(dead_code)]
    #[inline]
    pub fn payload_mut(&mut self) -> &mut Vec<u8> {
        &mut self.payload
    }

    // Generate a new mask for this frame.
    //
    // This method simply generates and stores the mask. It does not change the payload data.
    // Instead, the payload data will be masked with the generated mask when the frame is sent
    // to the other endpoint.
    #[doc(hidden)]
    #[inline]
    pub fn set_mask(&mut self) -> &mut Frame {
        self.mask = Some(rand::random());
        self
    }

    // This method unmasks the payload and should only be called on frames that are actually
    // masked. In other words, those frames that have just been received from a client endpoint.
    #[doc(hidden)]
    #[inline]
    pub fn remove_mask(&mut self) -> &mut Frame {
        self.mask
            .take()
            .map(|mask| apply_mask(&mut self.payload, &mask));
        self
    }

    /// Consume the frame into its payload.
    pub fn into_data(self) -> Vec<u8> {
        self.payload
    }

    /// Create a new data frame.
    #[inline]
    pub fn message(data: Vec<u8>, code: OpCode, finished: bool) -> Frame {
        debug_assert!(
            match code {
                OpCode::Text | OpCode::Binary | OpCode::Continue => true,
                _ => false,
            },
            "Invalid opcode for data frame."
        );

        Frame {
            finished,
            opcode: code,
            payload: data,
            ..Frame::default()
        }
    }

    /// Create a new Pong control frame.
    #[inline]
    pub fn pong(data: Vec<u8>) -> Frame {
        Frame {
            opcode: OpCode::Pong,
            payload: data,
            ..Frame::default()
        }
    }

    /// Create a new Ping control frame.
    #[inline]
    pub fn ping(data: Vec<u8>) -> Frame {
        Frame {
            opcode: OpCode::Ping,
            payload: data,
            ..Frame::default()
        }
    }

    /// Create a new Close control frame.
    #[inline]
    pub fn close(code: CloseCode, reason: &str) -> Frame {
        let payload = if let CloseCode::Empty = code {
            Vec::new()
        } else {
            let u: u16 = code.into();
            let raw = [(u >> 8) as u8, u as u8];
            [&raw, reason.as_bytes()].concat()
        };

        Frame {
            payload,
            ..Frame::default()
        }
    }

    /// Parse the input stream into a frame.
    pub fn parse(cursor: &mut CircularBuffer, max_payload_length: u64) -> Result<Option<Frame>> {
        let size = cursor.remaining();
        let initial = cursor.read_cursor();
        trace!("Position in buffer {:?}", initial);

        let mut head = [0u8; 2];
        if cursor.read(&mut head)? != 2 {
            cursor.set_read_cursor(initial);
            return Ok(None);
        }

        trace!("Parsed headers {:?}", head);

        let first = head[0];
        let second = head[1];
        trace!("First: {:b}", first);
        trace!("Second: {:b}", second);

        let finished = first & 0x80 != 0;

        let rsv1 = first & 0x40 != 0;
        let rsv2 = first & 0x20 != 0;
        let rsv3 = first & 0x10 != 0;

        let opcode = OpCode::from(first & 0x0F);
        trace!("Opcode: {:?}", opcode);

        let masked = second & 0x80 != 0;
        trace!("Masked: {:?}", masked);

        let mut header_length = 2;

        let mut length = u64::from(second & 0x7F);

        if let Some(length_nbytes) = match length {
            126 => Some(2),
            127 => Some(8),
            _ => None,
        } {
            match cursor.read_uint::<BigEndian>(length_nbytes) {
                Err(ref err) if err.kind() == ErrorKind::UnexpectedEof => {
                    cursor.set_read_cursor(initial);
                    return Ok(None);
                }
                Err(err) => {
                    return Err(Error::from(err));
                }
                Ok(read) => {
                    length = read;
                }
            };
            header_length += length_nbytes as u64;
        }
        trace!("Payload length: {}", length);

        if length > max_payload_length {
            return Err(Error::new(
                Kind::Protocol,
                format!(
                    "Rejected frame with payload length exceeding defined max: {}.",
                    max_payload_length
                ),
            ));
        }

        let mask = if masked {
            let mut mask_bytes = [0u8; 4];
            if cursor.read(&mut mask_bytes)? != 4 {
                cursor.set_read_cursor(initial);
                return Ok(None);
            } else {
                header_length += 4;
                Some(mask_bytes)
            }
        } else {
            None
        };

        match length.checked_add(header_length) {
            Some(l) if (size as u64) < l => {
                cursor.set_read_cursor(initial);
                return Ok(None);
            }
            Some(_) => (),
            None => return Ok(None),
        };

        let data = cursor.read_exact_into_vec(length as usize);

        // Disallow bad opcode
        if let OpCode::Bad = opcode {
            return Err(Error::new(
                Kind::Protocol,
                format!("Encountered invalid opcode: {}", first & 0x0F),
            ));
        }

        // control frames must have length <= 125
        match opcode {
            OpCode::Ping | OpCode::Pong if length > 125 => {
                return Err(Error::new(
                    Kind::Protocol,
                    format!(
                        "Rejected WebSocket handshake.Received control frame with length: {}.",
                        length
                    ),
                ))
            }
            OpCode::Close if length > 125 => {
                debug!("Received close frame with payload length exceeding 125. Morphing to protocol close frame.");
                return Ok(Some(Frame::close(
                    CloseCode::Protocol,
                    "Received close frame with payload length exceeding 125.",
                )));
            }
            _ => (),
        }

        let frame = Frame {
            finished,
            rsv1,
            rsv2,
            rsv3,
            opcode,
            mask,
            payload: data,
        };

        Ok(Some(frame))
    }

    /// Write a frame out to a buffer
    pub fn format<W>(&mut self, w: &mut W) -> Result<()>
    where
        W: Write,
    {
        let mut one = 0u8;
        let code: u8 = self.opcode.into();
        if self.is_final() {
            one |= 0x80;
        }
        if self.has_rsv1() {
            one |= 0x40;
        }
        if self.has_rsv2() {
            one |= 0x20;
        }
        if self.has_rsv3() {
            one |= 0x10;
        }
        one |= code;

        let mut two = 0u8;
        if self.is_masked() {
            two |= 0x80;
        }

        match self.payload.len() {
            len if len < 126 => {
                two |= len as u8;
            }
            len if len <= 65535 => {
                two |= 126;
            }
            _ => {
                two |= 127;
            }
        }
        w.write_all(&[one, two])?;

        if let Some(length_bytes) = match self.payload.len() {
            len if len < 126 => None,
            len if len <= 65535 => Some(2),
            _ => Some(8),
        } {
            w.write_uint::<BigEndian>(self.payload.len() as u64, length_bytes)?;
        }

        if self.is_masked() {
            let mask = self.mask.take().unwrap();
            apply_mask(&mut self.payload, &mask);
            w.write_all(&mask)?;
        }

        w.write_all(&self.payload)?;
        Ok(())
    }
}

impl Default for Frame {
    fn default() -> Frame {
        Frame {
            finished: true,
            rsv1: false,
            rsv2: false,
            rsv3: false,
            opcode: OpCode::Close,
            mask: None,
            payload: Vec::new(),
        }
    }
}

impl fmt::Display for Frame {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(
            f,
            "
<FRAME>
final: {}
reserved: {} {} {}
opcode: {}
length: {}
payload length: {}
payload: 0x{}
            ",
            self.finished,
            self.rsv1,
            self.rsv2,
            self.rsv3,
            self.opcode,
            // self.mask.map(|mask| format!("{:?}", mask)).unwrap_or("NONE".into()),
            self.len(),
            self.payload.len(),
            self.payload
                .iter()
                .map(|byte| format!("{:x}", byte))
                .collect::<String>()
        )
    }
}

mod test {
    #![allow(unused_imports, unused_variables, dead_code)]
    use super::*;
    use protocol::OpCode;

    #[test]
    fn display_frame() {
        let f = Frame::message("hi there".into(), OpCode::Text, true);
        let view = format!("{}", f);
        view.contains("payload:");
    }
}