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//! A macro for writing HTML templates.
//!
//! This documentation only describes the runtime API. For a general
//! guide, check out the [book] instead.
//!
//! [book]: http://lfairy.gitbooks.io/maud/content/

use std::fmt;
use std::io;

/// Wraps a `std::io::Write` in a `std::fmt::Write`.
///
/// Most I/O libraries work with binary data (`[u8]`), but Maud outputs
/// Unicode strings (`str`). This adapter links them together by
/// encoding the output as UTF-8.
///
/// # Example
///
/// ```rust,ignore
/// use std::io;
/// let writer = Utf8Writer::new(io::stdout());
/// let _ = html!(writer, p { "Hello, " $name "!" });
/// let result = writer.into_result();
/// result.unwrap();
/// ```
pub struct Utf8Writer<W: io::Write> {
    inner: W,
    result: io::Result<()>,
}

impl<W: io::Write> Utf8Writer<W> {
    /// Creates a `Utf8Writer` from a `std::io::Write`.
    pub fn new(inner: W) -> Utf8Writer<W> {
        Utf8Writer {
            inner: inner,
            result: Ok(()),
        }
    }

    pub fn into_inner(self) -> (W, io::Result<()>) {
        let Utf8Writer { inner, result } = self;
        (inner, result)
    }

    pub fn into_result(self) -> io::Result<()> {
        self.result
    }
}

impl<W: io::Write> fmt::Write for Utf8Writer<W> {
    fn write_str(&mut self, s: &str) -> fmt::Result {
        match io::Write::write_all(&mut self.inner, s.as_bytes()) {
            Ok(()) => Ok(()),
            Err(e) => {
                self.result = Err(e);
                Err(fmt::Error)
            }
        }
    }

    fn write_fmt(&mut self, args: fmt::Arguments) -> fmt::Result {
        match io::Write::write_fmt(&mut self.inner, args) {
            Ok(()) => Ok(()),
            Err(e) => {
                self.result = Err(e);
                Err(fmt::Error)
            }
        }
    }
}

/// Escapes an HTML value.
pub fn escape(s: &str) -> String {
    use std::fmt::Write;
    let mut buf = String::new();
    rt::Escaper { inner: &mut buf }.write_str(s).unwrap();
    buf
}

/// Internal functions used by the `maud_macros` package. You should
/// never need to call these directly.
#[doc(hidden)]
pub mod rt {
    use std::fmt;

    pub struct Escaper<'a, 'b: 'a> {
        pub inner: &'a mut (fmt::Write + 'b),
    }

    impl<'a, 'b> fmt::Write for Escaper<'a, 'b> {
        fn write_str(&mut self, s: &str) -> fmt::Result {
            for c in s.chars() {
                try!(match c {
                    '&' => self.inner.write_str("&amp;"),
                    '<' => self.inner.write_str("&lt;"),
                    '>' => self.inner.write_str("&gt;"),
                    '"' => self.inner.write_str("&quot;"),
                    '\'' => self.inner.write_str("&#39;"),
                    _ => write!(self.inner, "{}", c),
                });
            }
            Ok(())
        }
    }
}