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use std::any::{Any, TypeId};
use std::collections::HashMap;
use std::hash::BuildHasherDefault;
use std::fmt;

use fnv::FnvHasher;

type AnyMap = HashMap<TypeId, Box<Any + Send + Sync>, BuildHasherDefault<FnvHasher>>;

/// A type map of protocol extensions.
///
/// `Extensions` can be used by `Request` and `Response` to store
/// extra data derived from the underlying protocol.
#[derive(Default)]
pub struct Extensions {
    map: AnyMap,
}

impl Extensions {
    /// Create an empty `Extensions`.
    #[inline]
    pub fn new() -> Extensions {
        Extensions {
            map: HashMap::default(),
        }
    }

    /// Insert a type into this `Extensions`.
    ///
    /// If a extension of this type already existed, it will
    /// be returned.
    ///
    /// # Example
    ///
    /// ```
    /// # use http::Extensions;
    /// let mut ext = Extensions::new();
    /// assert!(ext.insert(5i32).is_none());
    /// assert!(ext.insert(4u8).is_none());
    /// assert_eq!(ext.insert(9i32), Some(5i32));
    /// ```
    pub fn insert<T: Send + Sync + 'static>(&mut self, val: T) -> Option<T> {
        self.map.insert(TypeId::of::<T>(), Box::new(val))
            .and_then(|boxed| {
                //TODO: we can use unsafe and remove double checking the type id
                (boxed as Box<Any + 'static>)
                    .downcast()
                    .ok()
                    .map(|boxed| *boxed)
            })
    }

    /// Get a reference to a type previously inserted on this `Extensions`.
    ///
    /// # Example
    ///
    /// ```
    /// # use http::Extensions;
    /// let mut ext = Extensions::new();
    /// assert!(ext.get::<i32>().is_none());
    /// ext.insert(5i32);
    ///
    /// assert_eq!(ext.get::<i32>(), Some(&5i32));
    /// ```
    pub fn get<T: Send + Sync + 'static>(&self) -> Option<&T> {
        self.map.get(&TypeId::of::<T>())
            //TODO: we can use unsafe and remove double checking the type id
            .and_then(|boxed| (&**boxed as &(Any + 'static)).downcast_ref())
    }

    /// Get a mutable reference to a type previously inserted on this `Extensions`.
    ///
    /// # Example
    ///
    /// ```
    /// # use http::Extensions;
    /// let mut ext = Extensions::new();
    /// ext.insert(String::from("Hello"));
    /// ext.get_mut::<String>().unwrap().push_str(" World");
    ///
    /// assert_eq!(ext.get::<String>().unwrap(), "Hello World");
    /// ```
    pub fn get_mut<T: Send + Sync + 'static>(&mut self) -> Option<&mut T> {
        self.map.get_mut(&TypeId::of::<T>())
            //TODO: we can use unsafe and remove double checking the type id
            .and_then(|boxed| (&mut **boxed as &mut (Any + 'static)).downcast_mut())
    }


    /// Remove a type from this `Extensions`.
    ///
    /// If a extension of this type existed, it will be returned.
    ///
    /// # Example
    ///
    /// ```
    /// # use http::Extensions;
    /// let mut ext = Extensions::new();
    /// ext.insert(5i32);
    /// assert_eq!(ext.remove::<i32>(), Some(5i32));
    /// assert!(ext.get::<i32>().is_none());
    /// ```
    pub fn remove<T: Send + Sync + 'static>(&mut self) -> Option<T> {
        self.map.remove(&TypeId::of::<T>())
            .and_then(|boxed| {
                //TODO: we can use unsafe and remove double checking the type id
                (boxed as Box<Any + 'static>)
                    .downcast()
                    .ok()
                    .map(|boxed| *boxed)
            })
    }

    /// Clear the `Extensions` of all inserted extensions.
    ///
    /// # Example
    ///
    /// ```
    /// # use http::Extensions;
    /// let mut ext = Extensions::new();
    /// ext.insert(5i32);
    /// ext.clear();
    ///
    /// assert!(ext.get::<i32>().is_none());
    /// ```
    #[inline]
    pub fn clear(&mut self) {
        self.map.clear();
    }
}

impl fmt::Debug for Extensions {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        f.debug_struct("Extensions")
            .finish()
    }
}

#[test]
fn test_extensions() {
    #[derive(Debug, PartialEq)]
    struct MyType(i32);

    let mut extensions = Extensions::new();

    extensions.insert(5i32);
    extensions.insert(MyType(10));

    assert_eq!(extensions.get(), Some(&5i32));
    assert_eq!(extensions.get_mut(), Some(&mut 5i32));

    assert_eq!(extensions.remove::<i32>(), Some(5i32));
    assert!(extensions.get::<i32>().is_none());

    assert_eq!(extensions.get::<bool>(), None);
    assert_eq!(extensions.get(), Some(&MyType(10)));
}