use std::convert::AsRef;

use outcome::IntoOutcome;
use response::{self, Responder};
use request::{self, Request, FromRequest};
use http::hyper::{HyperSetCookie, HyperCookiePair, FreshHyperResponse};

const FLASH_COOKIE_NAME: &'static str = "_flash";

/// Sets a "flash" cookies that will be removed the next time it is accessed.
/// The anologous type on the request side is
/// [FlashMessage](/rocket/request/type.FlashMessage.html).
///
/// This type makes it easy to send messages across requests. It is typically
/// used for "status" messages after redirects. For instance, if a user attempts
/// to visit a page he/she does not have access to, you may want to redirect the
/// user to a safe place and show a message indicating what happened on the
/// redirected page. The message should only persist for a single request. This
/// can be accomplished with this type.
///
/// # Usage
///
/// Each `Flash` message consists of a `name` and some `msg` contents. A generic
/// constructor ([new](#method.new)) can be used to construct a message with any
/// name, while the [warning](#method.warning), [success](#method.success), and
/// [error](#method.error) constructors create messages with the corresponding
/// names.
///
/// Messages can be retrieved on the request side via the
/// [FlashMessage](/rocket/request/type.FlashMessage.html) type and the
/// [name](#method.name) and [msg](#method.msg) methods.
///
/// # Responder
///
/// The `Responder` implementation for `Flash` sets the message cookie and then
/// uses the passed in responder `res` to complete the response. In other words,
/// it simply sets a cookie and delagates the rest of the response handling to
/// the wrapped responder.
pub struct Flash<R> {
    name: String,
    message: String,
    responder: R,
}

impl<R: Responder> Flash<R> {
    /// Constructs a new `Flash` message with the given `name`, `msg`, and
    /// underlying `responder`.
    ///
    /// # Examples
    ///
    /// Construct a "suggestion" message with contents "Try this out!" that
    /// redirects to "/".
    ///
    /// ```rust
    /// use rocket::response::{Redirect, Flash};
    ///
    /// let msg = Flash::new(Redirect::to("/"), "suggestion", "Try this out!");
    /// ```
    pub fn new<N: AsRef<str>, M: AsRef<str>>(res: R, name: N, msg: M) -> Flash<R> {
        Flash {
            name: name.as_ref().to_string(),
            message: msg.as_ref().to_string(),
            responder: res,
        }
    }

    /// Constructs a "success" `Flash` message with the given `responder` and
    /// `msg`.
    ///
    /// # Examples
    ///
    /// Construct a "success" message with contents "It worked!" that redirects
    /// to "/".
    ///
    /// ```rust
    /// use rocket::response::{Redirect, Flash};
    ///
    /// let msg = Flash::success(Redirect::to("/"), "It worked!");
    /// ```
    pub fn success<S: AsRef<str>>(responder: R, msg: S) -> Flash<R> {
        Flash::new(responder, "success", msg)
    }

    /// Constructs a "warning" `Flash` message with the given `responder` and
    /// `msg`.
    ///
    /// # Examples
    ///
    /// Construct a "warning" message with contents "Watch out!" that redirects
    /// to "/".
    ///
    /// ```rust
    /// use rocket::response::{Redirect, Flash};
    ///
    /// let msg = Flash::warning(Redirect::to("/"), "Watch out!");
    /// ```
    pub fn warning<S: AsRef<str>>(responder: R, msg: S) -> Flash<R> {
        Flash::new(responder, "warning", msg)
    }

    /// Constructs an "error" `Flash` message with the given `responder` and
    /// `msg`.
    ///
    /// # Examples
    ///
    /// Construct an "error" message with contents "Whoops!" that redirects
    /// to "/".
    ///
    /// ```rust
    /// use rocket::response::{Redirect, Flash};
    ///
    /// let msg = Flash::error(Redirect::to("/"), "Whoops!");
    /// ```
    pub fn error<S: AsRef<str>>(responder: R, msg: S) -> Flash<R> {
        Flash::new(responder, "error", msg)
    }

    fn cookie_pair(&self) -> HyperCookiePair {
        let content = format!("{}{}{}", self.name.len(), self.name, self.message);
        let mut pair = HyperCookiePair::new(FLASH_COOKIE_NAME.to_string(), content);
        pair.path = Some("/".to_string());
        pair.max_age = Some(300);
        pair
    }
}

impl<R: Responder> Responder for Flash<R> {
    fn respond<'b>(&mut self, mut res: FreshHyperResponse<'b>) -> response::Outcome<'b> {
        trace_!("Flash: setting message: {}:{}", self.name, self.message);
        res.headers_mut().set(HyperSetCookie(vec![self.cookie_pair()]));
        self.responder.respond(res)
    }
}

impl Flash<()> {
    fn named(name: &str, msg: &str) -> Flash<()> {
        Flash {
            name: name.to_string(),
            message: msg.to_string(),
            responder: (),
        }
    }

    /// Returns the `name` of this message.
    pub fn name(&self) -> &str {
        self.name.as_str()
    }

    /// Returns the `msg` contents of this message.
    pub fn msg(&self) -> &str {
        self.message.as_str()
    }
}

// This is Type-Aliased in Request.
impl<'r> FromRequest<'r> for Flash<()> {
    type Error = ();

    fn from_request(request: &'r Request) -> request::Outcome<Self, Self::Error> {
        trace_!("Flash: attemping to retrieve message.");
        let r = request.cookies().find(FLASH_COOKIE_NAME).ok_or(()).and_then(|cookie| {
            // Clear the flash message.
            trace_!("Flash: retrieving message: {:?}", cookie);
            request.cookies().remove(FLASH_COOKIE_NAME);

            // Parse the flash.
            let content = cookie.pair().1;
            let (len_str, rest) = match content.find(|c: char| !c.is_digit(10)) {
                Some(i) => (&content[..i], &content[i..]),
                None => (content, ""),
            };

            let name_len: usize = len_str.parse().map_err(|_| ())?;
            let (name, msg) = (&rest[..name_len], &rest[name_len..]);
            Ok(Flash::named(name, msg))
        });

        r.into_outcome()
    }
}