//! Multipart requests support.
use std::{cmp, fmt};
use std::rc::Rc;
use std::cell::RefCell;
use std::marker::PhantomData;

use mime;
use httparse;
use bytes::Bytes;
use http::HttpTryFrom;
use http::header::{self, HeaderMap, HeaderName, HeaderValue};
use futures::{Async, Stream, Poll};
use futures::task::{Task, current as current_task};

use payload::{Payload, PayloadError};
use httprequest::HttpRequest;

const MAX_HEADERS: usize = 32;

#[derive(Debug)]
pub struct MultipartError {
    pub payload: Payload,
}

/// The server-side implementation of `multipart/form-data` requests.
///
/// This will parse the incoming stream into `MultipartItem` instances via its
/// Stream implementation.
/// `MultipartItem::Field` contains multipart field. `MultipartItem::Multipart`
/// is used for nested multipart streams.
#[derive(Debug)]
pub struct Multipart {
    safety: Safety,
    payload: PayloadRef,
    boundary: String,
    eof: bool,
    bof: bool,
    item: InnerMultipartItem,
}

#[derive(Debug)]
pub enum MultipartItem {
    // Multipart field
    Field(Field),
    // Nested multipart item
    Multipart(Multipart),
}

#[derive(Debug)]
enum InnerMultipartItem {
    None,
    Field(Rc<RefCell<InnerField>>),
    // Nested multipart item
    // Multipart(Multipart),
}

impl Multipart {
    pub fn new(req: &HttpRequest, payload: Payload) -> Result<Multipart, MultipartError> {
        if let Some(content_type) = req.headers().get(header::CONTENT_TYPE) {
            if let Ok(content_type) = content_type.to_str() {
                if let Ok(ct) = content_type.parse::<mime::Mime>() {
                    if let Some(boundary) = ct.get_param(mime::BOUNDARY) {
                        return Ok(Multipart {
                            safety: Safety::new(),
                            payload: PayloadRef::new(payload),
                            boundary: boundary.as_str().to_owned(),
                            eof: false,
                            bof: true,
                            item: InnerMultipartItem::None,
                        })
                    }
                }
            }
        }
        Err(MultipartError{payload: payload})
    }

    fn read_headers(payload: &mut Payload) -> Poll<HeaderMap, PayloadError>
    {
        match payload.readuntil(b"\r\n\r\n")? {
            Async::NotReady => Ok(Async::NotReady),
            Async::Ready(bytes) => {
                let mut hdrs = [httparse::EMPTY_HEADER; MAX_HEADERS];
                match httparse::parse_headers(&bytes, &mut hdrs) {
                    Ok(httparse::Status::Complete((_, hdrs))) => {
                        // convert headers
                        let mut headers = HeaderMap::with_capacity(hdrs.len());
                        for h in hdrs {
                            if let Ok(name) = HeaderName::try_from(h.name) {
                                if let Ok(value) = HeaderValue::try_from(h.value) {
                                    headers.append(name, value);
                                } else {
                                    return Err(PayloadError::Incomplete)
                                }
                            } else {
                                return Err(PayloadError::Incomplete)
                            }
                        }
                        Ok(Async::Ready(headers))
                    }
                    Ok(httparse::Status::Partial) | Err(_) => Err(PayloadError::Incomplete),
                }
            }
        }
    }

    fn read_boundary(payload: &mut Payload, boundary: &str) -> Poll<bool, PayloadError>
    {
        // TODO: need to read epilogue
        match payload.readline()? {
            Async::NotReady => Ok(Async::NotReady),
            Async::Ready(chunk) => {
                if chunk.len() == boundary.len() + 4 &&
                    &chunk[..2] == b"--" &&
                    &chunk[2..boundary.len()+2] == boundary.as_bytes()
                {
                    Ok(Async::Ready(false))
                } else if chunk.len() == boundary.len() + 6 &&
                    &chunk[..2] == b"--" &&
                    &chunk[2..boundary.len()+2] == boundary.as_bytes() &&
                    &chunk[boundary.len()+2..boundary.len()+4] == b"--"
                {
                    Ok(Async::Ready(true))
                } else {
                    Err(PayloadError::Incomplete)
                }
            }
        }
    }

    fn skip_until_boundary(payload: &mut Payload, boundary: &str) -> Poll<bool, PayloadError>
    {
        let mut eof = false;
        loop {
            if let Async::Ready(chunk) = payload.readline()? {
                if chunk.is_empty() {
                    //ValueError("Could not find starting boundary %r"
                    //% (self._boundary))
                }
                if &chunk[..2] == b"--" && &chunk[2..chunk.len()-2] == boundary.as_bytes() {
                    break;
                } else {
                    let b: &[u8] = boundary.as_ref();
                    if chunk.len() <= boundary.len() + 2 &&
                        &chunk[..boundary.len()] == b &&
                        &chunk[boundary.len()..boundary.len()+2] == b"--" {
                            eof = true;
                            break;
                        }
                }
            } else {
                return Ok(Async::NotReady)
            }
        }
        Ok(Async::Ready(eof))
    }
}

impl Drop for Multipart {
    fn drop(&mut self) {
        // InnerMultipartItem::Field has to be dropped first because of Safety.
        self.item = InnerMultipartItem::None;
    }
}

impl Stream for Multipart {
    type Item = MultipartItem;
    type Error = PayloadError;

    fn poll(&mut self) -> Poll<Option<Self::Item>, Self::Error> {
        if self.eof {
            Ok(Async::Ready(None))
        } else {
            // release field
            loop {
                let stop = match self.item {
                    InnerMultipartItem::Field(ref mut field) => {
                        match field.borrow_mut().poll(&self.safety)? {
                            Async::NotReady =>
                                return Ok(Async::NotReady),
                            Async::Ready(Some(_)) =>
                                continue,
                            Async::Ready(None) =>
                                true,
                        }
                    }
                    _ => false,
                };
                if stop {
                    self.item = InnerMultipartItem::None;
                }
                if let InnerMultipartItem::None = self.item {
                    break;
                }
            }

            let headers = if let Some(payload) = self.payload.get_mut(&self.safety) {
                // read until first boundary
                if self.bof {
                    if let Async::Ready(eof) =
                        Multipart::skip_until_boundary(payload, &self.boundary)?
                    {
                        self.eof = eof;
                    } else {
                        return Ok(Async::NotReady)
                    }
                    self.bof = false;
                } else {
                    // read boundary
                    match Multipart::read_boundary(payload, &self.boundary)? {
                        Async::NotReady => return Ok(Async::NotReady),
                        Async::Ready(eof) => self.eof = eof,
                    }
                }

                if self.eof {
                    return Ok(Async::Ready(None))
                }

                // read field headers
                if let Async::Ready(headers) = Multipart::read_headers(payload)? {
                    headers
                } else {
                    return Ok(Async::NotReady)
                }
            } else {
                debug!("NotReady: field is in flight");
                return Ok(Async::NotReady)
            };

            //
            let field = Rc::new(RefCell::new(InnerField::new(
                self.payload.clone(), self.boundary.clone(), &headers)?));
            self.item = InnerMultipartItem::Field(Rc::clone(&field));

            Ok(Async::Ready(Some(
                MultipartItem::Field(Field::new(self.safety.clone(), headers, field)))))
        }
    }
}

/// A single field in a multipart stream
pub struct Field {
    ct: mime::Mime,
    headers: HeaderMap,
    inner: Rc<RefCell<InnerField>>,
    safety: Safety,
}

impl Field {

    fn new(safety: Safety, headers: HeaderMap, inner: Rc<RefCell<InnerField>>) -> Self {
        let mut mt = mime::APPLICATION_OCTET_STREAM;
        if let Some(content_type) = headers.get(header::CONTENT_TYPE) {
            if let Ok(content_type) = content_type.to_str() {
                if let Ok(ct) = content_type.parse::<mime::Mime>() {
                    mt = ct;
                }
            }
        }
        Field {
            ct: mt,
            headers: headers,
            inner: inner,
            safety: safety,
        }
    }

    pub fn headers(&self) -> &HeaderMap {
        &self.headers
    }

    pub fn content_type(&self) -> &mime::Mime {
        &self.ct
    }
}

impl Stream for Field {
    type Item = Bytes;
    type Error = PayloadError;

    fn poll(&mut self) -> Poll<Option<Self::Item>, Self::Error> {
        if self.safety.current() {
            self.inner.borrow_mut().poll(&self.safety)
        } else {
            Ok(Async::NotReady)
        }
    }
}

impl fmt::Debug for Field {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        let res = write!(f, "\nMultipartField: {}\n", self.ct);
        let _ = write!(f, "  boundary: {}\n", self.inner.borrow().boundary);
        let _ = write!(f, "  headers:\n");
        for key in self.headers.keys() {
            let vals: Vec<_> = self.headers.get_all(key).iter().collect();
            if vals.len() > 1 {
                let _ = write!(f, "    {:?}: {:?}\n", key, vals);
            } else {
                let _ = write!(f, "    {:?}: {:?}\n", key, vals[0]);
            }
        }
        res
    }
}

#[derive(Debug)]
struct InnerField {
    payload: Option<PayloadRef>,
    boundary: String,
    eof: bool,
    length: Option<u64>,
}

impl InnerField {

    fn new(payload: PayloadRef, boundary: String, headers: &HeaderMap)
           -> Result<InnerField, PayloadError>
    {
        let len = if let Some(len) = headers.get(header::CONTENT_LENGTH) {
            if let Ok(s) = len.to_str() {
                if let Ok(len) = s.parse::<u64>() {
                    Some(len)
                } else {
                    return Err(PayloadError::Incomplete)
                }
            } else {
                return Err(PayloadError::Incomplete)
            }
        } else {
            None
        };

        Ok(InnerField {
            payload: Some(payload),
            boundary: boundary,
            eof: false,
            length: len })
    }

    /// Reads body part content chunk of the specified size.
    /// The body part must has `Content-Length` header with proper value.
    fn read_len(payload: &mut Payload, size: &mut u64) -> Poll<Option<Bytes>, PayloadError>
    {
        if *size == 0 {
            Ok(Async::Ready(None))
        } else {
            match payload.readany() {
                Async::NotReady => Ok(Async::NotReady),
                Async::Ready(None) => Ok(Async::Ready(None)),
                Async::Ready(Some(Ok(mut chunk))) => {
                    let len = cmp::min(chunk.len() as u64, *size);
                    *size -= len;
                    let ch = chunk.split_to(len as usize);
                    if !chunk.is_empty() {
                        payload.unread_data(chunk);
                    }
                    Ok(Async::Ready(Some(ch)))
                },
                Async::Ready(Some(Err(err))) => Err(err)
            }
        }
    }

    /// Reads content chunk of body part with unknown length.
    /// The `Content-Length` header for body part is not necessary.
    fn read_stream(payload: &mut Payload, boundary: &str) -> Poll<Option<Bytes>, PayloadError>
    {
        match payload.readuntil(b"\r")? {
            Async::NotReady => Ok(Async::NotReady),
            Async::Ready(mut chunk) => {
                if chunk.len() == 1 {
                    payload.unread_data(chunk);
                    match payload.readexactly(boundary.len() + 4)? {
                        Async::NotReady => Ok(Async::NotReady),
                        Async::Ready(chunk) => {
                            if &chunk[..2] == b"\r\n" && &chunk[2..4] == b"--" &&
                                &chunk[4..] == boundary.as_bytes()
                            {
                                payload.unread_data(chunk);
                                Ok(Async::Ready(None))
                            } else {
                                Ok(Async::Ready(Some(chunk)))
                            }
                        }
                    }
                } else {
                    let to = chunk.len() - 1;
                    let ch = chunk.split_to(to);
                    payload.unread_data(chunk);
                    Ok(Async::Ready(Some(ch)))
                }
            }
        }
    }

    fn poll(&mut self, s: &Safety) -> Poll<Option<Bytes>, PayloadError> {
        if self.payload.is_none() {
            return Ok(Async::Ready(None))
        }
        if self.eof {
            if let Some(payload) = self.payload.as_ref().unwrap().get_mut(s) {
                match payload.readline()? {
                    Async::NotReady =>
                        return Ok(Async::NotReady),
                    Async::Ready(chunk) => {
                        assert_eq!(
                            chunk.as_ref(), b"\r\n",
                            "reader did not read all the data or it is malformed");
                    }
                }
            } else {
                return Ok(Async::NotReady);
            }

            self.payload.take();
            return Ok(Async::Ready(None))
        }

        let result = if let Some(payload) = self.payload.as_ref().unwrap().get_mut(s) {
            let res = if let Some(ref mut len) = self.length {
                InnerField::read_len(payload, len)?
            } else {
                InnerField::read_stream(payload, &self.boundary)?
            };

            match res {
                Async::NotReady => Async::NotReady,
                Async::Ready(Some(bytes)) => Async::Ready(Some(bytes)),
                Async::Ready(None) => {
                    self.eof = true;
                    match payload.readline()? {
                        Async::NotReady => Async::NotReady,
                        Async::Ready(chunk) => {
                            assert_eq!(
                                chunk.as_ref(), b"\r\n",
                                "reader did not read all the data or it is malformed");
                            Async::Ready(None)
                        }
                    }
                }
            }
        } else {
            Async::NotReady
        };

        if Async::Ready(None) == result {
            self.payload.take();
        }
        Ok(result)
    }
}

#[derive(Debug)]
struct PayloadRef {
    task: Option<Task>,
    payload: Rc<Payload>,
}

impl PayloadRef {
    fn new(payload: Payload) -> PayloadRef {
        PayloadRef {
            task: None,
            payload: Rc::new(payload),
        }
    }

    fn get_mut<'a, 'b>(&'a self, s: &'b Safety) -> Option<&'a mut Payload>
        where 'a: 'b
    {
        if s.current() {
            let payload: &mut Payload = unsafe {
                &mut *(self.payload.as_ref() as *const _ as *mut _)};
            Some(payload)
        } else {
            None
        }
    }
}

impl Clone for PayloadRef {
    fn clone(&self) -> PayloadRef {
        PayloadRef {
            task: Some(current_task()),
            payload: Rc::clone(&self.payload),
        }
    }
}

/// Counter. It tracks of number of clones of payloads and give access to payload only
/// to top most task panics if Safety get destroyed and it not top most task.
#[derive(Debug)]
struct Safety {
    task: Option<Task>,
    level: usize,
    payload: Rc<PhantomData<bool>>,
}

impl Safety {
    fn new() -> Safety {
        let payload = Rc::new(PhantomData);
        Safety {
            task: None,
            level: Rc::strong_count(&payload),
            payload: payload,
        }
    }

    fn current(&self) -> bool {
        Rc::strong_count(&self.payload) == self.level
    }

}

impl Clone for Safety {
    fn clone(&self) -> Safety {
        let payload = Rc::clone(&self.payload);
        Safety {
            task: Some(current_task()),
            level: Rc::strong_count(&payload),
            payload: payload,
        }
    }
}

impl Drop for Safety {
    fn drop(&mut self) {
        // parent task is dead
        if Rc::strong_count(&self.payload) != self.level {
            panic!("Safety get dropped but it is not from top-most task");
        }
        if let Some(task) = self.task.take() {
            task.notify()
        }
    }
}