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    // Copyright 2013-2016 The rust-url developers.
    //
    // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
    // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
    // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
    // option. This file may not be copied, modified, or distributed
    // except according to those terms.

    //! URLs use special chacters to indicate the parts of the request.  For example, a forward slash
    //! indicates a path.  In order for that charcter to exist outside of a path separator, that
    //! charcter would need to be encoded.
    //!
    //! Percent encoding replaces reserved charcters with the `%` escape charcter followed by hexidecimal
    //! ASCII representaton.  For non-ASCII charcters that are percent encoded, a UTF-8 byte sequence
    //! becomes percent encoded.  A simple example can be seen when the space literal is replaced with
    //! `%20`.
    //!
    //! Percent encoding is further complicated by the fact that different parts of an URL have
    //! different encoding requirements.  In order to support the variety of encoding requirements,
    //! `url::percent_encoding` includes different *encode sets*.
    //! See [URL Standard](https://url.spec.whatwg.org/#percent-encoded-bytes) for details.
    //!
    //! This module provides some `*_ENCODE_SET` constants.
    //! If a different set is required, it can be created with
    //! the [`define_encode_set!`](../macro.define_encode_set!.html) macro.
    //!
    //! # Examples
    //!
    //! ```
    //! use url::percent_encoding::{utf8_percent_encode, DEFAULT_ENCODE_SET};
    //!
    //! assert_eq!(utf8_percent_encode("foo bar?", DEFAULT_ENCODE_SET).to_string(), "foo%20bar%3F");
    //! ```

    use std::ascii::AsciiExt;
    use std::borrow::Cow;
    use std::fmt;
    use std::slice;
    use std::str;

    /// Represents a set of characters / bytes that should be percent-encoded.
    ///
    /// See [encode sets specification](http://url.spec.whatwg.org/#simple-encode-set).
    ///
    /// Different characters need to be encoded in different parts of an URL.
    /// For example, a literal `?` question mark in an URL’s path would indicate
    /// the start of the query string.
    /// A question mark meant to be part of the path therefore needs to be percent-encoded.
    /// In the query string however, a question mark does not have any special meaning
    /// and does not need to be percent-encoded.
    ///
    /// A few sets are defined in this module.
    /// Use the [`define_encode_set!`](../macro.define_encode_set!.html) macro to define different ones.
    pub trait EncodeSet: Clone {
        /// Called with UTF-8 bytes rather than code points.
        /// Should return true for all non-ASCII bytes.
        fn contains(&self, byte: u8) -> bool;
    }

    /// Define a new struct
    /// that implements the [`EncodeSet`](percent_encoding/trait.EncodeSet.html) trait,
    /// for use in [`percent_decode()`](percent_encoding/fn.percent_encode.html)
    /// and related functions.
    ///
    /// Parameters are characters to include in the set in addition to those of the base set.
    /// See [encode sets specification](http://url.spec.whatwg.org/#simple-encode-set).
    ///
    /// Example
    /// =======
    ///
    /// ```rust
    /// #[macro_use] extern crate percent_encoding;
    /// use percent_encoding::{utf8_percent_encode, SIMPLE_ENCODE_SET};
    /// define_encode_set! {
    ///     /// This encode set is used in the URL parser for query strings.
    ///     pub QUERY_ENCODE_SET = [SIMPLE_ENCODE_SET] | {' ', '"', '#', '<', '>'}
    /// }
    /// # fn main() {
    /// assert_eq!(utf8_percent_encode("foo bar", QUERY_ENCODE_SET).collect::<String>(), "foo%20bar");
    /// # }
    /// ```
    #[macro_export]
    macro_rules! define_encode_set {
        ($(#[$attr: meta])* pub $name: ident = [$base_set: expr] | {$($ch: pat),*}) => {
            $(#[$attr])*
            #[derive(Copy, Clone, Debug)]
            #[allow(non_camel_case_types)]
            pub struct $name;

            impl $crate::EncodeSet for $name {
                #[inline]
                fn contains(&self, byte: u8) -> bool {
                    match byte as char {
                        $(
                            $ch => true,
                        )*
                        _ => $base_set.contains(byte)
                    }
                }
            }
        }
    }

    /// This encode set is used for the path of cannot-be-a-base URLs.
    ///
    /// All ASCII charcters less than hexidecimal 20 and greater than 7E are encoded.  This includes
    /// special charcters such as line feed, carriage return, NULL, etc.
    #[derive(Copy, Clone, Debug)]
    #[allow(non_camel_case_types)]
    pub struct SIMPLE_ENCODE_SET;

    impl EncodeSet for SIMPLE_ENCODE_SET {
        #[inline]
        fn contains(&self, byte: u8) -> bool {
            byte < 0x20 || byte > 0x7E
        }
    }

    define_encode_set! {
        /// This encode set is used in the URL parser for query strings.
        ///
        /// Aside from special chacters defined in the [`SIMPLE_ENCODE_SET`](struct.SIMPLE_ENCODE_SET.html),
        /// space, double quote ("), hash (#), and inequality qualifiers (<), (>) are encoded.
        pub QUERY_ENCODE_SET = [SIMPLE_ENCODE_SET] | {' ', '"', '#', '<', '>'}
    }

    define_encode_set! {
        /// This encode set is used for path components.
        ///
        /// Aside from special chacters defined in the [`SIMPLE_ENCODE_SET`](struct.SIMPLE_ENCODE_SET.html),
        /// space, double quote ("), hash (#), inequality qualifiers (<), (>), backtick (`),
        /// question mark (?), and curly brackets ({), (}) are encoded.
        pub DEFAULT_ENCODE_SET = [QUERY_ENCODE_SET] | {'`', '?', '{', '}'}
    }

    define_encode_set! {
        /// This encode set is used for on '/'-separated path segment
        ///
        /// Aside from special chacters defined in the [`SIMPLE_ENCODE_SET`](struct.SIMPLE_ENCODE_SET.html),
        /// space, double quote ("), hash (#), inequality qualifiers (<), (>), backtick (`),
        /// question mark (?), and curly brackets ({), (}), percent sign (%), forward slash (/) are
        /// encoded.
        pub PATH_SEGMENT_ENCODE_SET = [DEFAULT_ENCODE_SET] | {'%', '/'}
    }

    define_encode_set! {
        /// This encode set is used for username and password.
        ///
        /// Aside from special chacters defined in the [`SIMPLE_ENCODE_SET`](struct.SIMPLE_ENCODE_SET.html),
        /// space, double quote ("), hash (#), inequality qualifiers (<), (>), backtick (`),
        /// question mark (?), and curly brackets ({), (}), forward slash (/), colon (:), semi-colon (;),
        /// equality (=), at (@), backslash (\\), square brackets ([), (]), caret (\^), and pipe (|) are
        /// encoded.
        pub USERINFO_ENCODE_SET = [DEFAULT_ENCODE_SET] | {
            '/', ':', ';', '=', '@', '[', '\\', ']', '^', '|'
        }
    }

    /// Return the percent-encoding of the given bytes.
    ///
    /// This is unconditional, unlike `percent_encode()` which uses an encode set.
    ///
    /// # Examples
    ///
    /// ```
    /// use url::percent_encoding::percent_encode_byte;
    ///
    /// assert_eq!("foo bar".bytes().map(percent_encode_byte).collect::<String>(),
    ///            "%66%6F%6F%20%62%61%72");
    /// ```
    pub fn percent_encode_byte(byte: u8) -> &'static str {
        let index = usize::from(byte) * 3;
        &"\
            %00%01%02%03%04%05%06%07%08%09%0A%0B%0C%0D%0E%0F\
            %10%11%12%13%14%15%16%17%18%19%1A%1B%1C%1D%1E%1F\
            %20%21%22%23%24%25%26%27%28%29%2A%2B%2C%2D%2E%2F\
            %30%31%32%33%34%35%36%37%38%39%3A%3B%3C%3D%3E%3F\
            %40%41%42%43%44%45%46%47%48%49%4A%4B%4C%4D%4E%4F\
            %50%51%52%53%54%55%56%57%58%59%5A%5B%5C%5D%5E%5F\
            %60%61%62%63%64%65%66%67%68%69%6A%6B%6C%6D%6E%6F\
            %70%71%72%73%74%75%76%77%78%79%7A%7B%7C%7D%7E%7F\
            %80%81%82%83%84%85%86%87%88%89%8A%8B%8C%8D%8E%8F\
            %90%91%92%93%94%95%96%97%98%99%9A%9B%9C%9D%9E%9F\
            %A0%A1%A2%A3%A4%A5%A6%A7%A8%A9%AA%AB%AC%AD%AE%AF\
            %B0%B1%B2%B3%B4%B5%B6%B7%B8%B9%BA%BB%BC%BD%BE%BF\
            %C0%C1%C2%C3%C4%C5%C6%C7%C8%C9%CA%CB%CC%CD%CE%CF\
            %D0%D1%D2%D3%D4%D5%D6%D7%D8%D9%DA%DB%DC%DD%DE%DF\
            %E0%E1%E2%E3%E4%E5%E6%E7%E8%E9%EA%EB%EC%ED%EE%EF\
            %F0%F1%F2%F3%F4%F5%F6%F7%F8%F9%FA%FB%FC%FD%FE%FF\
        "[index..index + 3]
    }

    /// Percent-encode the given bytes with the given encode set.
    ///
    /// The encode set define which bytes (in addition to non-ASCII and controls)
    /// need to be percent-encoded.
    /// The choice of this set depends on context.
    /// For example, `?` needs to be encoded in an URL path but not in a query string.
    ///
    /// The return value is an iterator of `&str` slices (so it has a `.collect::<String>()` method)
    /// that also implements `Display` and `Into<Cow<str>>`.
    /// The latter returns `Cow::Borrowed` when none of the bytes in `input`
    /// are in the given encode set.
    ///
    /// # Examples
    ///
    /// ```
    /// use url::percent_encoding::{percent_encode, DEFAULT_ENCODE_SET};
    ///
    /// assert_eq!(percent_encode(b"foo bar?", DEFAULT_ENCODE_SET).to_string(), "foo%20bar%3F");
    /// ```
    #[inline]
    pub fn percent_encode<E: EncodeSet>(input: &[u8], encode_set: E) -> PercentEncode<E> {
        PercentEncode {
            bytes: input,
            encode_set: encode_set,
        }
    }

    /// Percent-encode the UTF-8 encoding of the given string.
    ///
    /// See `percent_encode()` for how to use the return value.
    ///
    /// # Examples
    ///
    /// ```
    /// use url::percent_encoding::{utf8_percent_encode, DEFAULT_ENCODE_SET};
    ///
    /// assert_eq!(utf8_percent_encode("foo bar?", DEFAULT_ENCODE_SET).to_string(), "foo%20bar%3F");
    /// ```
    #[inline]
    pub fn utf8_percent_encode<E: EncodeSet>(input: &str, encode_set: E) -> PercentEncode<E> {
        percent_encode(input.as_bytes(), encode_set)
    }

    /// The return type of `percent_encode()` and `utf8_percent_encode()`.
    #[derive(Clone, Debug)]
    pub struct PercentEncode<'a, E: EncodeSet> {
        bytes: &'a [u8],
        encode_set: E,
    }

    impl<'a, E: EncodeSet> Iterator for PercentEncode<'a, E> {
        type Item = &'a str;

        fn next(&mut self) -> Option<&'a str> {
            if let Some((&first_byte, remaining)) = self.bytes.split_first() {
                if self.encode_set.contains(first_byte) {
                    self.bytes = remaining;
                    Some(percent_encode_byte(first_byte))
                } else {
                    assert!(first_byte.is_ascii());
                    for (i, &byte) in remaining.iter().enumerate() {
                        if self.encode_set.contains(byte) {
                            // 1 for first_byte + i for previous iterations of this loop
                            let (unchanged_slice, remaining) = self.bytes.split_at(1 + i);
                            self.bytes = remaining;
                            return Some(unsafe { str::from_utf8_unchecked(unchanged_slice) })
                        } else {
                            assert!(byte.is_ascii());
                        }
                    }
                    let unchanged_slice = self.bytes;
                    self.bytes = &[][..];
                    Some(unsafe { str::from_utf8_unchecked(unchanged_slice) })
                }
            } else {
                None
            }
        }

        fn size_hint(&self) -> (usize, Option<usize>) {
            if self.bytes.is_empty() {
                (0, Some(0))
            } else {
                (1, Some(self.bytes.len()))
            }
        }
    }

    impl<'a, E: EncodeSet> fmt::Display for PercentEncode<'a, E> {
        fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
            for c in (*self).clone() {
                formatter.write_str(c)?
            }
            Ok(())
        }
    }

    impl<'a, E: EncodeSet> From<PercentEncode<'a, E>> for Cow<'a, str> {
        fn from(mut iter: PercentEncode<'a, E>) -> Self {
            match iter.next() {
                None => "".into(),
                Some(first) => {
                    match iter.next() {
                        None => first.into(),
                        Some(second) => {
                            let mut string = first.to_owned();
                            string.push_str(second);
                            string.extend(iter);
                            string.into()
                        }
                    }
                }
            }
        }
    }

    /// Percent-decode the given bytes.
    ///
    /// The return value is an iterator of decoded `u8` bytes
    /// that also implements `Into<Cow<u8>>`
    /// (which returns `Cow::Borrowed` when `input` contains no percent-encoded sequence)
    /// and has `decode_utf8()` and `decode_utf8_lossy()` methods.
    ///
    /// # Examples
    ///
    /// ```
    /// use url::percent_encoding::percent_decode;
    ///
    /// assert_eq!(percent_decode(b"foo%20bar%3F").decode_utf8().unwrap(), "foo bar?");
    /// ```
    #[inline]
    pub fn percent_decode(input: &[u8]) -> PercentDecode {
        PercentDecode {
            bytes: input.iter()
        }
    }

    /// The return type of `percent_decode()`.
    #[derive(Clone, Debug)]
    pub struct PercentDecode<'a> {
        bytes: slice::Iter<'a, u8>,
    }

    fn after_percent_sign(iter: &mut slice::Iter<u8>) -> Option<u8> {
        let initial_iter = iter.clone();
        let h = iter.next().and_then(|&b| (b as char).to_digit(16));
        let l = iter.next().and_then(|&b| (b as char).to_digit(16));
        if let (Some(h), Some(l)) = (h, l) {
            Some(h as u8 * 0x10 + l as u8)
        } else {
            *iter = initial_iter;
            None
        }
    }

    impl<'a> Iterator for PercentDecode<'a> {
        type Item = u8;

        fn next(&mut self) -> Option<u8> {
            self.bytes.next().map(|&byte| {
                if byte == b'%' {
                    after_percent_sign(&mut self.bytes).unwrap_or(byte)
                } else {
                    byte
                }
            })
        }

        fn size_hint(&self) -> (usize, Option<usize>) {
            let bytes = self.bytes.len();
            (bytes / 3, Some(bytes))
        }
    }

    impl<'a> From<PercentDecode<'a>> for Cow<'a, [u8]> {
        fn from(iter: PercentDecode<'a>) -> Self {
            match iter.if_any() {
                Some(vec) => Cow::Owned(vec),
                None => Cow::Borrowed(iter.bytes.as_slice()),
            }
        }
    }

    impl<'a> PercentDecode<'a> {
        /// If the percent-decoding is different from the input, return it as a new bytes vector.
        pub fn if_any(&self) -> Option<Vec<u8>> {
            let mut bytes_iter = self.bytes.clone();
            while bytes_iter.any(|&b| b == b'%') {
                if let Some(decoded_byte) = after_percent_sign(&mut bytes_iter) {
                    let initial_bytes = self.bytes.as_slice();
                    let unchanged_bytes_len = initial_bytes.len() - bytes_iter.len() - 3;
                    let mut decoded = initial_bytes[..unchanged_bytes_len].to_owned();
                    decoded.push(decoded_byte);
                    decoded.extend(PercentDecode {
                        bytes: bytes_iter
                    });
                    return Some(decoded)
                }
            }
            // Nothing to decode
            None
        }

        /// Decode the result of percent-decoding as UTF-8.
        ///
        /// This is return `Err` when the percent-decoded bytes are not well-formed in UTF-8.
        pub fn decode_utf8(self) -> Result<Cow<'a, str>, str::Utf8Error> {
            match self.clone().into() {
                Cow::Borrowed(bytes) => {
                    match str::from_utf8(bytes) {
                        Ok(s) => Ok(s.into()),
                        Err(e) => Err(e),
                    }
                }
                Cow::Owned(bytes) => {
                    match String::from_utf8(bytes) {
                        Ok(s) => Ok(s.into()),
                        Err(e) => Err(e.utf8_error()),
                    }
                }
            }
        }

        /// Decode the result of percent-decoding as UTF-8, lossily.
        ///
        /// Invalid UTF-8 percent-encoded byte sequences will be replaced � U+FFFD,
        /// the replacement character.
        pub fn decode_utf8_lossy(self) -> Cow<'a, str> {
            decode_utf8_lossy(self.clone().into())
        }
    }

    fn decode_utf8_lossy(input: Cow<[u8]>) -> Cow<str> {
        match input {
            Cow::Borrowed(bytes) => String::from_utf8_lossy(bytes),
            Cow::Owned(bytes) => {
                let raw_utf8: *const [u8];
                match String::from_utf8_lossy(&bytes) {
                    Cow::Borrowed(utf8) => raw_utf8 = utf8.as_bytes(),
                    Cow::Owned(s) => return s.into(),
                }
                // from_utf8_lossy returned a borrow of `bytes` unchanged.
                debug_assert!(raw_utf8 == &*bytes as *const [u8]);
                // Reuse the existing `Vec` allocation.
                unsafe { String::from_utf8_unchecked(bytes) }.into()
            }
        }
    }

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