use std::{str, slice};
use iter::Bytes;

mod iter;

macro_rules! next {
    ($bytes:ident) => ({
        match $bytes.next() {
            Some(b) => b,
            None => return Ok(Status::Partial)
        }
    })
}

macro_rules! expect {
    ($bytes:ident.next() == $pat:pat => $ret:expr) => {
        match next!($bytes) {
            v@$pat => v,
            _ => return $ret
        }
    }
}

macro_rules! complete {
    ($e:expr) => {
        match try!($e) {
            Status::Complete(v) => v,
            Status::Partial => return Ok(Status::Partial)
        }
    }
}

#[inline]
fn shrink<T>(slice: &mut &mut [T], len: usize) {
    debug_assert!(slice.len() >= len);
    let ptr = slice.as_mut_ptr();
    *slice = unsafe { slice::from_raw_parts_mut(ptr, len) };
}

/// Determines if byte is a token char.
///
/// > ```notrust
/// > token          = 1*tchar
/// >
/// > tchar          = "!" / "#" / "$" / "%" / "&" / "'" / "*"
/// >                / "+" / "-" / "." / "^" / "_" / "`" / "|" / "~"
/// >                / DIGIT / ALPHA
/// >                ; any VCHAR, except delimiters
/// > ```
#[inline]
fn is_token(b: u8) -> bool {
    b > 0x1F && b < 0x7F
}

macro_rules! space {
    ($bytes:ident or $err:expr) => ({
        expect!($bytes.next() == b' ' => Err($err));
        $bytes.slice();
    })
}

macro_rules! newline {
    ($bytes:ident) => ({
        match next!($bytes) {
            b'\r' => {
                expect!($bytes.next() == b'\n' => Err(Error::NewLine));
                $bytes.slice();
            },
            b'\n' => {
                $bytes.slice();
            },
            _ => return Err(Error::NewLine)
        }
    })
}

#[derive(Copy, Clone, PartialEq, Eq, Debug)]
pub enum Error {
    HeaderName,
    HeaderValue,
    NewLine,
    Status,
    Token,
    TooManyHeaders,
    Version
}

#[derive(Copy, Clone, PartialEq, Debug)]
pub enum Status<T> {
    Complete(T),
    Partial
}

impl<T> Status<T> {
    #[inline]
    pub fn is_complete(&self) -> bool {
        match *self {
            Status::Complete(..) => true,
            Status::Partial => false
        }
    }

    #[inline]
    pub fn is_partial(&self) -> bool {
        match *self {
            Status::Complete(..) => false,
            Status::Partial => true
        }
    }

    #[inline]
    pub fn unwrap(self) -> T {
        match self {
            Status::Complete(t) => t,
            Status::Partial => panic!("Tried to unwrap Status::Partial")
        }
    }
}

pub struct Request<'headers, 'buf: 'headers> {
    pub method: Option<&'buf str>,
    pub path: Option<&'buf str>,
    pub version: Option<u8>,
    pub headers: &'headers mut [Header<'buf>]
}

impl<'h, 'b> Request<'h, 'b> {
    #[inline]
    pub fn new(headers: &'h mut [Header<'b>]) -> Request<'h, 'b> {
        Request {
            method: None,
            path: None,
            version: None,
            headers: headers,
        }
    }

    pub fn parse(&mut self, buf: &'b [u8]) -> Result<Status<usize>, Error> {
        let orig_len = buf.len();
        let mut bytes = Bytes::new(buf);
        self.method = Some(complete!(parse_token(&mut bytes)));
        self.path = Some(complete!(parse_token(&mut bytes)));
        self.version = Some(complete!(parse_version(&mut bytes)));
        newline!(bytes);

        let len = orig_len - bytes.len();
        let headers_len = complete!(parse_headers(&mut self.headers, &mut bytes));

        Ok(Status::Complete(len + headers_len))
    }
}

pub struct Response<'headers, 'buf: 'headers> {
    pub version: Option<u8>,
    pub code: Option<u16>,
    pub reason: Option<&'buf str>,
    pub headers: &'headers mut [Header<'buf>]
}

impl<'h, 'b> Response<'h, 'b> {
    #[inline]
    pub fn new(headers: &'h mut [Header<'b>]) -> Response<'h, 'b> {
        Response {
            version: None,
            code: None,
            reason: None,
            headers: headers,
        }
    }

    pub fn parse(&mut self, buf: &'b [u8]) -> Result<Status<usize>, Error> {
        let orig_len = buf.len();
        let mut bytes = Bytes::new(buf);

        self.version = Some(complete!(parse_version(&mut bytes)));
        space!(bytes or Error::Version);
        self.code = Some(complete!(parse_code(&mut bytes)));
        space!(bytes or Error::Status);
        self.reason = Some(complete!(parse_reason(&mut bytes)));
        newline!(bytes);

        let len = orig_len - bytes.len();
        let headers_len = complete!(parse_headers(&mut self.headers, &mut bytes));
        Ok(Status::Complete(len + headers_len))
    }
}

#[derive(Copy, Clone, PartialEq, Debug)]
pub struct Header<'a> {
    pub name: &'a str,
    pub value: &'a [u8],
}

pub const EMPTY_HEADER: Header<'static> = Header { name: "", value: b"" };

#[inline]
fn parse_version(bytes: &mut Bytes) -> Result<Status<u8>, Error> {
    expect!(bytes.next() == b'H' => Err(Error::Version));
    expect!(bytes.next() == b'T' => Err(Error::Version));
    expect!(bytes.next() == b'T' => Err(Error::Version));
    expect!(bytes.next() == b'P' => Err(Error::Version));
    expect!(bytes.next() == b'/' => Err(Error::Version));
    expect!(bytes.next() == b'1' => Err(Error::Version));
    expect!(bytes.next() == b'.' => Err(Error::Version));
    let v = match next!(bytes) {
        b'0' => 0,
        b'1' => 1,
        _ => return Err(Error::Version)
    };
    //expect!(buf[i] == (b' ' | b'\r' | b'\n') => Err(Error::Version));
    Ok(Status::Complete(v))
}

// From [RFC 7230](https://tools.ietf.org/html/rfc7230):
//
// > ```notrust
// > reason-phrase  = *( HTAB / SP / VCHAR / obs-text )
// > HTAB           = %x09        ; horizontal tab
// > VCHAR          = %x21-7E     ; visible (printing) characters
// > obs-text       = %x80-FF
// > ```
//
// > A.2.  Changes from RFC 2616
// >
// > Non-US-ASCII content in header fields and the reason phrase
// > has been obsoleted and made opaque (the TEXT rule was removed).
//
// Note that the following implementation deliberately rejects the obsoleted (non-US-ASCII) text range.
//
// The fully compliant parser should probably just return the reason-phrase as an opaque &[u8] data
// and leave interpretation to user or specialized helpers (akin to .display() in std::path::Path)

#[inline]
fn parse_reason<'a>(bytes: &mut Bytes<'a>) -> Result<Status<&'a str>, Error> {
    loop {
        let b = next!(bytes);
        if b == b'\r' || b == b'\n' {
            return Ok(Status::Complete(unsafe {
                // all bytes up till `i` must have been HTAB / SP / VCHAR
                str::from_utf8_unchecked(bytes.slice_skip(1))
            }));
        } else if !((b >= 0x20 && b <= 0x7E) || b == b'\t') {
            return Err(Error::Status);
        }
    }
}

#[inline]
fn parse_token<'a>(bytes: &mut Bytes<'a>) -> Result<Status<&'a str>, Error> {
    loop {
        let b = next!(bytes);
        if b == b' ' || b == b'\r' || b == b'\n' {
            return Ok(Status::Complete(unsafe {
                // all bytes up till `i` must have been `is_token`.
                str::from_utf8_unchecked(bytes.slice_skip(1))
            }));
        } else if !is_token(b) {
            return Err(Error::Token);
        }
    }
}

#[inline]
fn parse_code(bytes: &mut Bytes) -> Result<Status<u16>, Error> {
    let hundreds = expect!(bytes.next() == b'0'...b'9' => Err(Error::Status));
    let tens = expect!(bytes.next() == b'0'...b'9' => Err(Error::Status));
    let ones = expect!(bytes.next() == b'0'...b'9' => Err(Error::Status));

    Ok(Status::Complete((hundreds - b'0') as u16 * 100 +
                        (tens - b'0') as u16 * 10 +
                        (ones - b'0') as u16))
}

#[inline]
fn parse_headers<'a, 'b>(headers: &mut &mut [Header<'a>], bytes: &'b mut Bytes<'a>) -> Result<Status<usize>, Error> {
    let mut num_headers: usize = 0;
    let mut count: usize = 0;
    let mut result = Err(Error::TooManyHeaders);

    {
        let mut iter = headers.iter_mut();

        'headers: loop {
            // a newline here means the head is over!
            let b = next!(bytes);
            if b == b'\r' {
                expect!(bytes.next() == b'\n' => Err(Error::NewLine));
                result = Ok(Status::Complete(count + bytes.pos()));
                break;
            } else if b == b'\n' {
                result = Ok(Status::Complete(count + bytes.pos()));
                break;
            } else if b == b':' || !is_token(b) {
                return Err(Error::HeaderName);
            }

            let header = match iter.next() {
                Some(header) => header,
                None => break 'headers
            };

            num_headers += 1;
            // parse header name until colon
            loop {
                let b = next!(bytes);
                if b == b':' {
                    count += bytes.pos();
                    header.name = unsafe {
                        str::from_utf8_unchecked(bytes.slice_skip(1))
                    };
                    break;
                } else if !is_token(b) {
                    return Err(Error::HeaderName);
                }
            }

            let mut b;

            'value: loop {

                // eat white space between colon and value
                loop {
                    b = next!(bytes);
                    if b == b' ' || b == b'\t' {
                        count += bytes.pos();
                        bytes.slice();
                        continue;
                    } else {
                        if !is_token(b) {
                            if (b < 0o40 && b != 0o11) || b == 0o177 {
                                break 'value;
                            }
                        }
                        break;
                    }
                }

                // parse value till EOL



                macro_rules! check {
                    ($bytes:ident, $i:ident) => ({
                        b = $bytes.$i();
                        if !is_token(b) {
                            if (b < 0o40 && b != 0o11) || b == 0o177 {
                                break 'value;
                            }
                        }
                    });
                    ($bytes:ident) => ({
                        check!($bytes, _0);
                        check!($bytes, _1);
                        check!($bytes, _2);
                        check!($bytes, _3);
                        check!($bytes, _4);
                        check!($bytes, _5);
                        check!($bytes, _6);
                        check!($bytes, _7);
                    })
                }
                while let Some(mut bytes8) = bytes.next_8() {
                    check!(bytes8);
                }
                loop {
                    b = next!(bytes);
                    if !is_token(b) {
                        if (b < 0o40 && b != 0o11) || b == 0o177 {
                            break 'value;
                        }
                    }
                }
            }

            //found_ctl
            if b == b'\r' {
                expect!(bytes.next() == b'\n' => Err(Error::HeaderValue));
                count += bytes.pos();
                header.value = bytes.slice_skip(2);
            } else if b == b'\n' {
                count += bytes.pos();
                header.value = bytes.slice_skip(1);
            } else {
                return Err(Error::HeaderValue);
            }

        }
    } // drop iter

    shrink(headers, num_headers);
    result
}

#[cfg(test)]
mod tests {
    use super::{Request, Response, Status, EMPTY_HEADER, shrink};

    const NUM_OF_HEADERS: usize = 4;

    #[test]
    fn test_shrink() {
        let mut arr = [EMPTY_HEADER; 16];
        {
            let slice = &mut &mut arr[..];
            assert_eq!(slice.len(), 16);
            shrink(slice, 4);
            assert_eq!(slice.len(), 4);
        }
        assert_eq!(arr.len(), 16);
    }

    macro_rules! req {
        ($name:ident, $buf:expr, $closure:expr) => (
            req! {$name, $buf, Ok(Status::Complete($buf.len())), $closure }
        );
        ($name:ident, $buf:expr, $len:expr, $closure:expr) => (
        #[test]
        fn $name() {
            let mut headers = [EMPTY_HEADER; NUM_OF_HEADERS];
            let mut req = Request::new(&mut headers[..]);
            let closure: Box<Fn(Request)> = Box::new($closure);
            let status = req.parse($buf.as_ref());
            assert_eq!(status, $len);
            closure(req);
        }
        )
    }

    req! {
        test_request_simple,
        b"GET / HTTP/1.1\r\n\r\n",
        |req| {
            assert_eq!(req.method.unwrap(), "GET");
            assert_eq!(req.path.unwrap(), "/");
            assert_eq!(req.version.unwrap(), 1);
            assert_eq!(req.headers.len(), 0);
        }
    }

    req! {
        test_request_headers,
        b"GET / HTTP/1.1\r\nHost: foo.com\r\nCookie: \r\n\r\n",
        |req| {
            assert_eq!(req.method.unwrap(), "GET");
            assert_eq!(req.path.unwrap(), "/");
            assert_eq!(req.version.unwrap(), 1);
            assert_eq!(req.headers.len(), 2);
            assert_eq!(req.headers[0].name, "Host");
            assert_eq!(req.headers[0].value, b"foo.com");
            assert_eq!(req.headers[1].name, "Cookie");
            assert_eq!(req.headers[1].value, b"");
        }
    }

    req! {
        test_request_headers_max,
        b"GET / HTTP/1.1\r\nA: A\r\nB: B\r\nC: C\r\nD: D\r\n\r\n",
        |req| {
            assert_eq!(req.headers.len(), NUM_OF_HEADERS);
        }
    }

    req! {
        test_request_multibyte,
        b"GET / HTTP/1.1\r\nHost: foo.com\r\nUser-Agent: \xe3\x81\xb2\xe3/1.0\r\n\r\n",
        |req| {
            assert_eq!(req.method.unwrap(), "GET");
            assert_eq!(req.path.unwrap(), "/");
            assert_eq!(req.version.unwrap(), 1);
            assert_eq!(req.headers[0].name, "Host");
            assert_eq!(req.headers[0].value, b"foo.com");
            assert_eq!(req.headers[1].name, "User-Agent");
            assert_eq!(req.headers[1].value, b"\xe3\x81\xb2\xe3/1.0");
        }
    }


    req! {
        test_request_partial,
        b"GET / HTTP/1.1\r\n\r", Ok(Status::Partial),
        |_req| {}
    }

    req! {
        test_request_newlines,
        b"GET / HTTP/1.1\n\n",
        |_| {}
    }


    macro_rules! res {
        ($name:ident, $buf:expr, $closure:expr) => (
            res! {$name, $buf, Ok(Status::Complete($buf.len())), $closure }
        );
        ($name:ident, $buf:expr, $len:expr, $closure:expr) => (
        #[test]
        fn $name() {
            let mut headers = [EMPTY_HEADER; NUM_OF_HEADERS];
            let mut res = Response::new(&mut headers[..]);
            let closure: Box<Fn(Response)> = Box::new($closure);
            let status = res.parse($buf.as_ref());
            assert_eq!(status, $len);
            closure(res);
        }
        )
    }

    res! {
        test_response_simple,
        b"HTTP/1.1 200 OK\r\n\r\n",
        |res| {
            assert_eq!(res.version.unwrap(), 1);
            assert_eq!(res.code.unwrap(), 200);
            assert_eq!(res.reason.unwrap(), "OK");
        }
    }

    res! {
        test_response_reason_missing,
        b"HTTP/1.1 200 \r\n\r\n",
        |res| {
            assert_eq!(res.version.unwrap(), 1);
            assert_eq!(res.code.unwrap(), 200);
            assert_eq!(res.reason.unwrap(), "");
        }
    }

    res! {
        test_response_reason_with_space_and_tab,
        b"HTTP/1.1 101 Switching Protocols\t\r\n\r\n",
        |res| {
            assert_eq!(res.version.unwrap(), 1);
            assert_eq!(res.code.unwrap(), 101);
            assert_eq!(res.reason.unwrap(), "Switching Protocols\t");
        }
    }

    static RESPONSE_REASON_WITH_OBS_TEXT_BYTE: &'static [u8] = b"HTTP/1.1 200 X\xFFZ\r\n\r\n";
    res! {
        test_response_reason_with_obsolete_text_byte,
        RESPONSE_REASON_WITH_OBS_TEXT_BYTE,
        Err(::Error::Status),
        |_res| {}
    }

    res! {
        test_response_reason_with_nul_byte,
        b"HTTP/1.1 200 \x00\r\n\r\n",
        Err(::Error::Status),
        |_res| {}
    }

    res! {
        test_response_version_missing_space,
        b"HTTP/1.1",
        Ok(Status::Partial),
        |_res| {}
    }

    res! {
        test_response_code_missing_space,
        b"HTTP/1.1 200",
        Ok(Status::Partial),
        |_res| {}
    }
}