//! Headers container, and common header fields.
//!
//! hyper has the opinion that Headers should be strongly-typed, because that's
//! why we're using Rust in the first place. To set or get any header, an object
//! must implement the `Header` trait from this module. Several common headers
//! are already provided, such as `Host`, `ContentType`, `UserAgent`, and others.
use std::any::Any;
use std::borrow::Cow::{Borrowed, Owned};
use std::fmt;
use std::io::Read;
use std::raw::TraitObject;
use std::collections::HashMap;
use std::collections::hash_map::{Iter, Entry};
use std::iter::{FromIterator, IntoIterator};
use std::borrow::{Cow, IntoCow};
use std::{mem, raw};

use unicase::UniCase;

use self::internals::Item;
use {http, HttpResult, HttpError};

pub use self::shared::{Charset, Encoding, EntityTag, Quality, QualityItem, qitem, q};
pub use self::common::*;

mod common;
mod internals;
mod shared;
pub mod parsing;

type HeaderName = UniCase<Cow<'static, str>>;

/// A trait for any object that will represent a header field and value.
///
/// This trait represents the construction and identification of headers,
/// and contains trait-object unsafe methods.
pub trait Header: Clone + Any + Send + Sync {
    /// Returns the name of the header field this belongs to.
    ///
    /// This will become an associated constant once available.
    fn header_name() -> &'static str;
    /// Parse a header from a raw stream of bytes.
    ///
    /// It's possible that a request can include a header field more than once,
    /// and in that case, the slice will have a length greater than 1. However,
    /// it's not necessarily the case that a Header is *allowed* to have more
    /// than one field value. If that's the case, you **should** return `None`
    /// if `raw.len() > 1`.
    fn parse_header(raw: &[Vec<u8>]) -> Option<Self>;

}

/// A trait for any object that will represent a header field and value.
///
/// This trait represents the formatting of a Header for output to a TcpStream.
pub trait HeaderFormat: fmt::Debug + HeaderClone + Any + Send + Sync {
    /// Format a header to be output into a TcpStream.
    ///
    /// This method is not allowed to introduce an Err not produced
    /// by the passed-in Formatter.
    fn fmt_header(&self, fmt: &mut fmt::Formatter) -> fmt::Result;

}

#[doc(hidden)]
pub trait HeaderClone {
    fn clone_box(&self) -> Box<HeaderFormat + Sync + Send>;
}

impl<T: HeaderFormat + Send + Sync + Clone> HeaderClone for T {
    #[inline]
    fn clone_box(&self) -> Box<HeaderFormat + Sync + Send> {
        Box::new(self.clone())
    }
}

impl HeaderFormat {
    #[inline]
    unsafe fn downcast_ref_unchecked<T: 'static>(&self) -> &T {
        mem::transmute(mem::transmute::<&HeaderFormat, raw::TraitObject>(self).data)
    }

    #[inline]
    unsafe fn downcast_mut_unchecked<T: 'static>(&mut self) -> &mut T {
        mem::transmute(mem::transmute::<&mut HeaderFormat, raw::TraitObject>(self).data)
    }
}

impl Clone for Box<HeaderFormat + Send + Sync> {
    #[inline]
    fn clone(&self) -> Box<HeaderFormat + Send + Sync> {
        self.clone_box()
    }
}

#[inline]
fn header_name<T: Header>() -> &'static str {
    let name = <T as Header>::header_name();
    name
}

/// A map of header fields on requests and responses.
#[derive(Clone)]
pub struct Headers {
    data: HashMap<HeaderName, Item>
}

// To prevent DOS from a server sending a never ending header.
// The value was copied from curl.
const MAX_HEADERS_LENGTH: u32 = 100 * 1024;

impl Headers {

    /// Creates a new, empty headers map.
    pub fn new() -> Headers {
        Headers {
            data: HashMap::new()
        }
    }

    #[doc(hidden)]
    pub fn from_raw<R: Read>(rdr: &mut R) -> HttpResult<Headers> {
        let mut headers = Headers::new();
        let mut count = 0u32;
        loop {
            match try!(http::read_header(rdr)) {
                Some((name, value)) => {
                    debug!("raw header: {:?}={:?}", name, &value[..]);
                    count += (name.len() + value.len()) as u32;
                    if count > MAX_HEADERS_LENGTH {
                        debug!("Max header size reached, aborting");
                        return Err(HttpError::HttpHeaderError)
                    }
                    let name = UniCase(Owned(name));
                    let mut item = match headers.data.entry(name) {
                        Entry::Vacant(entry) => entry.insert(Item::new_raw(vec![])),
                        Entry::Occupied(entry) => entry.into_mut()
                    };
                    item.mut_raw().push(value);
                },
                None => break,
            }
        }
        Ok(headers)
    }

    /// Set a header field to the corresponding value.
    ///
    /// The field is determined by the type of the value being set.
    pub fn set<H: Header + HeaderFormat>(&mut self, value: H) {
        self.data.insert(UniCase(Borrowed(header_name::<H>())),
                         Item::new_typed(Box::new(value)));
    }

    /// Access the raw value of a header.
    ///
    /// Prefer to use the typed getters instead.
    ///
    /// Example:
    ///
    /// ```
    /// # use hyper::header::Headers;
    /// # let mut headers = Headers::new();
    /// let raw_content_type = headers.get_raw("content-type");
    /// ```
    pub fn get_raw(&self, name: &str) -> Option<&[Vec<u8>]> {
        self.data
            .get(&UniCase(Borrowed(unsafe { mem::transmute::<&str, &str>(name) })))
            .map(Item::raw)
    }

    /// Set the raw value of a header, bypassing any typed headers.
    ///
    /// Example:
    ///
    /// ```
    /// # use hyper::header::Headers;
    /// # let mut headers = Headers::new();
    /// headers.set_raw("content-length", vec![b"5".to_vec()]);
    /// ```
    pub fn set_raw<K: IntoCow<'static, str>>(&mut self, name: K, value: Vec<Vec<u8>>) {
        self.data.insert(UniCase(name.into_cow()), Item::new_raw(value));
    }

    /// Remove a header set by set_raw
    pub fn remove_raw(&mut self, name: &str) {
        self.data.remove(&UniCase(name.into_cow()));
    }

    /// Get a reference to the header field's value, if it exists.
    pub fn get<H: Header + HeaderFormat>(&self) -> Option<&H> {
        self.data.get(&UniCase(Borrowed(header_name::<H>()))).and_then(Item::typed::<H>)
    }

    /// Get a mutable reference to the header field's value, if it exists.
    pub fn get_mut<H: Header + HeaderFormat>(&mut self) -> Option<&mut H> {
        self.data.get_mut(&UniCase(Borrowed(header_name::<H>()))).and_then(Item::typed_mut::<H>)
    }

    /// Returns a boolean of whether a certain header is in the map.
    ///
    /// Example:
    ///
    /// ```
    /// # use hyper::header::Headers;
    /// # use hyper::header::ContentType;
    /// # let mut headers = Headers::new();
    /// let has_type = headers.has::<ContentType>();
    /// ```
    pub fn has<H: Header + HeaderFormat>(&self) -> bool {
        self.data.contains_key(&UniCase(Borrowed(header_name::<H>())))
    }

    /// Removes a header from the map, if one existed.
    /// Returns true if a header has been removed.
    pub fn remove<H: Header + HeaderFormat>(&mut self) -> bool {
        self.data.remove(&UniCase(Borrowed(header_name::<H>()))).is_some()
    }

    /// Returns an iterator over the header fields.
    pub fn iter<'a>(&'a self) -> HeadersItems<'a> {
        HeadersItems {
            inner: self.data.iter()
        }
    }

    /// Returns the number of headers in the map.
    pub fn len(&self) -> usize {
        self.data.len()
    }

    /// Remove all headers from the map.
    pub fn clear(&mut self) {
        self.data.clear()
    }
}

impl fmt::Display for Headers {
   fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
        for header in self.iter() {
            try!(write!(fmt, "{}\r\n", header));
        }
        Ok(())
    }
}

impl fmt::Debug for Headers {
    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
        try!(fmt.write_str("Headers {{ "));
        for header in self.iter() {
            try!(write!(fmt, "{:?}, ", header));
        }
        try!(fmt.write_str("}}"));
        Ok(())
    }
}

/// An `Iterator` over the fields in a `Headers` map.
pub struct HeadersItems<'a> {
    inner: Iter<'a, HeaderName, Item>
}

impl<'a> Iterator for HeadersItems<'a> {
    type Item = HeaderView<'a>;

    fn next(&mut self) -> Option<HeaderView<'a>> {
        match self.inner.next() {
            Some((k, v)) => Some(HeaderView(k, v)),
            None => None
        }
    }
}

/// Returned with the `HeadersItems` iterator.
pub struct HeaderView<'a>(&'a HeaderName, &'a Item);

impl<'a> HeaderView<'a> {
    /// Check if a HeaderView is a certain Header.
    #[inline]
    pub fn is<H: Header>(&self) -> bool {
        UniCase(header_name::<H>().into_cow()) == *self.0
    }

    /// Get the Header name as a slice.
    #[inline]
    pub fn name(&self) -> &'a str {
        self.0.as_slice()
    }

    /// Cast the value to a certain Header type.
    #[inline]
    pub fn value<H: Header + HeaderFormat>(&self) -> Option<&'a H> {
        self.1.typed::<H>()
    }

    /// Get just the header value as a String.
    #[inline]
    pub fn value_string(&self) -> String {
        (*self.1).to_string()
    }
}

impl<'a> fmt::Display for HeaderView<'a> {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "{}: {}", self.0, *self.1)
    }
}

impl<'a> fmt::Debug for HeaderView<'a> {
    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
        fmt::Display::fmt(self, fmt)
    }
}

impl<'a> Extend<HeaderView<'a>> for Headers {
    fn extend<I: IntoIterator<Item=HeaderView<'a>>>(&mut self, iter: I) {
        for header in iter {
            self.data.insert((*header.0).clone(), (*header.1).clone());
        }
    }
}

impl<'a> FromIterator<HeaderView<'a>> for Headers {
    fn from_iter<I: IntoIterator<Item=HeaderView<'a>>>(iter: I) -> Headers {
        let mut headers = Headers::new();
        headers.extend(iter);
        headers
    }
}

impl<'a> fmt::Display for &'a (HeaderFormat + Send + Sync) {
    #[inline]
    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
        (**self).fmt_header(fmt)
    }
}

/// A wrapper around any Header with a Display impl that calls fmt_header.
///
/// This can be used like so: `format!("{}", HeaderFormatter(&header))` to
/// get the representation of a Header which will be written to an
/// outgoing TcpStream.
pub struct HeaderFormatter<'a, H: HeaderFormat>(pub &'a H);

impl<'a, H: HeaderFormat> fmt::Display for HeaderFormatter<'a, H> {
    #[inline]
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        self.0.fmt_header(f)
    }
}

impl<'a, H: HeaderFormat> fmt::Debug for HeaderFormatter<'a, H> {
    #[inline]
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        self.0.fmt_header(f)
    }
}

#[cfg(test)]
mod tests {
    use std::fmt;
    use mime::Mime;
    use mime::TopLevel::Text;
    use mime::SubLevel::Plain;
    use super::{Headers, Header, HeaderFormat, ContentLength, ContentType,
                Accept, Host, qitem};

    use test::Bencher;

    #[test]
    fn test_from_raw() {
        let headers = Headers::from_raw(&mut b"Content-Length: 10\r\n\r\n").unwrap();
        assert_eq!(headers.get(), Some(&ContentLength(10)));
    }

    #[test]
    fn test_content_type() {
        let content_type = Header::parse_header([b"text/plain".to_vec()].as_slice());
        assert_eq!(content_type, Some(ContentType(Mime(Text, Plain, vec![]))));
    }

    #[test]
    fn test_accept() {
        let text_plain = qitem(Mime(Text, Plain, vec![]));
        let application_vendor = "application/vnd.github.v3.full+json; q=0.5".parse().unwrap();

        let accept = Header::parse_header([b"text/plain".to_vec()].as_slice());
        assert_eq!(accept, Some(Accept(vec![text_plain.clone()])));

        let accept = Header::parse_header([b"application/vnd.github.v3.full+json; q=0.5, text/plain".to_vec()].as_slice());
        assert_eq!(accept, Some(Accept(vec![application_vendor, text_plain])));
    }

    #[derive(Clone, PartialEq, Debug)]
    struct CrazyLength(Option<bool>, usize);

    impl Header for CrazyLength {
        fn header_name() -> &'static str {
            "content-length"
        }
        fn parse_header(raw: &[Vec<u8>]) -> Option<CrazyLength> {
            use std::str::from_utf8;
            use std::str::FromStr;

            if raw.len() != 1 {
                return None;
            }
            // we JUST checked that raw.len() == 1, so raw[0] WILL exist.
            match from_utf8(unsafe { &raw.get_unchecked(0)[..] }) {
                Ok(s) => FromStr::from_str(s).ok(),
                Err(_) => None
            }.map(|u| CrazyLength(Some(false), u))
        }
    }

    impl HeaderFormat for CrazyLength {
        fn fmt_header(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
            let CrazyLength(ref opt, ref value) = *self;
            write!(fmt, "{:?}, {:?}", opt, value)
        }
    }

    #[test]
    fn test_different_structs_for_same_header() {
        let headers = Headers::from_raw(&mut b"Content-Length: 10\r\n\r\n").unwrap();
        assert_eq!(headers.get::<ContentLength>(), Some(&ContentLength(10)));
        assert_eq!(headers.get::<CrazyLength>(), Some(&CrazyLength(Some(false), 10)));
    }

    #[test]
    fn test_trailing_whitespace() {
        let headers = Headers::from_raw(&mut b"Content-Length: 10   \r\n\r\n").unwrap();
        assert_eq!(headers.get::<ContentLength>(), Some(&ContentLength(10)));
    }

    #[test]
    fn test_multiple_reads() {
        let headers = Headers::from_raw(&mut b"Content-Length: 10\r\n\r\n").unwrap();
        let ContentLength(one) = *headers.get::<ContentLength>().unwrap();
        let ContentLength(two) = *headers.get::<ContentLength>().unwrap();
        assert_eq!(one, two);
    }

    #[test]
    fn test_different_reads() {
        let headers = Headers::from_raw(&mut b"Content-Length: 10\r\nContent-Type: text/plain\r\n\r\n").unwrap();
        let ContentLength(_) = *headers.get::<ContentLength>().unwrap();
        let ContentType(_) = *headers.get::<ContentType>().unwrap();
    }

    #[test]
    fn test_get_mutable() {
        let mut headers = Headers::from_raw(&mut b"Content-Length: 10\r\nContent-Type: text/plain\r\n\r\n").unwrap();
        *headers.get_mut::<ContentLength>().unwrap() = ContentLength(20);
        assert_eq!(*headers.get::<ContentLength>().unwrap(), ContentLength(20));
    }

    #[test]
    fn test_headers_show() {
        let mut headers = Headers::new();
        headers.set(ContentLength(15));
        headers.set(Host { hostname: "foo.bar".to_string(), port: None });

        let s = headers.to_string();
        // hashmap's iterators have arbitrary order, so we must sort first
        let mut pieces = s.split("\r\n").collect::<Vec<&str>>();
        pieces.sort();
        let s = pieces.into_iter().rev().collect::<Vec<&str>>().connect("\r\n");
        assert_eq!(s, "Host: foo.bar\r\nContent-Length: 15\r\n");
    }

    #[test]
    fn test_headers_show_raw() {
        let headers = Headers::from_raw(&mut b"Content-Length: 10\r\n\r\n").unwrap();
        let s = headers.to_string();
        assert_eq!(s, "Content-Length: 10\r\n");
    }

    #[test]
    fn test_set_raw() {
        let mut headers = Headers::new();
        headers.set(ContentLength(10));
        headers.set_raw("content-LENGTH", vec![b"20".to_vec()]);
        assert_eq!(headers.get_raw("Content-length").unwrap(), &[b"20".to_vec()][..]);
        assert_eq!(headers.get(), Some(&ContentLength(20)));
    }

    #[test]
    fn test_remove_raw() {
        let mut headers = Headers::new();
        headers.set_raw("content-LENGTH", vec![b"20".to_vec()]);
        headers.remove_raw("content-LENGTH");
        assert_eq!(headers.get_raw("Content-length"), None);
    }

    #[test]
    fn test_len() {
        let mut headers = Headers::new();
        headers.set(ContentLength(10));
        assert_eq!(headers.len(), 1);
        headers.set(ContentType(Mime(Text, Plain, vec![])));
        assert_eq!(headers.len(), 2);
        // Redundant, should not increase count.
        headers.set(ContentLength(20));
        assert_eq!(headers.len(), 2);
    }

    #[test]
    fn test_clear() {
        let mut headers = Headers::new();
        headers.set(ContentLength(10));
        headers.set(ContentType(Mime(Text, Plain, vec![])));
        assert_eq!(headers.len(), 2);
        headers.clear();
        assert_eq!(headers.len(), 0);
    }

    #[test]
    fn test_iter() {
        let mut headers = Headers::new();
        headers.set(ContentLength(11));
        for header in headers.iter() {
            assert!(header.is::<ContentLength>());
            assert_eq!(header.name(), <ContentLength as Header>::header_name());
            assert_eq!(header.value(), Some(&ContentLength(11)));
            assert_eq!(header.value_string(), "11".to_string());
        }
    }

    #[bench]
    fn bench_headers_new(b: &mut Bencher) {
        b.iter(|| {
            let mut h = Headers::new();
            h.set(ContentLength(11));
            h
        })
    }

    #[bench]
    fn bench_headers_from_raw(b: &mut Bencher) {
        b.iter(|| Headers::from_raw(&mut b"Content-Length: 10\r\n\r\n").unwrap())
    }

    #[bench]
    fn bench_headers_get(b: &mut Bencher) {
        let mut headers = Headers::new();
        headers.set(ContentLength(11));
        b.iter(|| assert_eq!(headers.get::<ContentLength>(), Some(&ContentLength(11))))
    }

    #[bench]
    fn bench_headers_get_miss(b: &mut Bencher) {
        let headers = Headers::new();
        b.iter(|| assert!(headers.get::<ContentLength>().is_none()))
    }

    #[bench]
    fn bench_headers_set(b: &mut Bencher) {
        let mut headers = Headers::new();
        b.iter(|| headers.set(ContentLength(12)))
    }

    #[bench]
    fn bench_headers_has(b: &mut Bencher) {
        let mut headers = Headers::new();
        headers.set(ContentLength(11));
        b.iter(|| assert!(headers.has::<ContentLength>()))
    }

    #[bench]
    fn bench_headers_view_is(b: &mut Bencher) {
        let mut headers = Headers::new();
        headers.set(ContentLength(11));
        let mut iter = headers.iter();
        let view = iter.next().unwrap();
        b.iter(|| assert!(view.is::<ContentLength>()))
    }

    #[bench]
    fn bench_headers_fmt(b: &mut Bencher) {
        let mut headers = Headers::new();
        headers.set(ContentLength(11));
        b.iter(|| headers.to_string())
    }
}