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    // Copyright 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.

    use crate::Url;
    use std::ops::{Index, Range, RangeFrom, RangeFull, RangeTo};

    impl Index<RangeFull> for Url {
        type Output = str;
        fn index(&self, _: RangeFull) -> &str {
            &self.serialization
        }
    }

    impl Index<RangeFrom<Position>> for Url {
        type Output = str;
        fn index(&self, range: RangeFrom<Position>) -> &str {
            &self.serialization[self.index(range.start)..]
        }
    }

    impl Index<RangeTo<Position>> for Url {
        type Output = str;
        fn index(&self, range: RangeTo<Position>) -> &str {
            &self.serialization[..self.index(range.end)]
        }
    }

    impl Index<Range<Position>> for Url {
        type Output = str;
        fn index(&self, range: Range<Position>) -> &str {
            &self.serialization[self.index(range.start)..self.index(range.end)]
        }
    }

    /// Indicates a position within a URL based on its components.
    ///
    /// A range of positions can be used for slicing `Url`:
    ///
    /// ```rust
    /// # use url::{Url, Position};
    /// # fn something(some_url: Url) {
    /// let serialization: &str = &some_url[..];
    /// let serialization_without_fragment: &str = &some_url[..Position::AfterQuery];
    /// let authority: &str = &some_url[Position::BeforeUsername..Position::AfterPort];
    /// let data_url_payload: &str = &some_url[Position::BeforePath..Position::AfterQuery];
    /// let scheme_relative: &str = &some_url[Position::BeforeUsername..];
    /// # }
    /// ```
    ///
    /// In a pseudo-grammar (where `[`…`]?` makes a sub-sequence optional),
    /// URL components and delimiters that separate them are:
    ///
    /// ```notrust
    /// url =
    ///     scheme ":"
    ///     [ "//" [ username [ ":" password ]? "@" ]? host [ ":" port ]? ]?
    ///     path [ "?" query ]? [ "#" fragment ]?
    /// ```
    ///
    /// When a given component is not present,
    /// its "before" and "after" position are the same
    /// (so that `&some_url[BeforeFoo..AfterFoo]` is the empty string)
    /// and component ordering is preserved
    /// (so that a missing query "is between" a path and a fragment).
    ///
    /// The end of a component and the start of the next are either the same or separate
    /// by a delimiter.
    /// (Not that the initial `/` of a path is considered part of the path here, not a delimiter.)
    /// For example, `&url[..BeforeFragment]` would include a `#` delimiter (if present in `url`),
    /// so `&url[..AfterQuery]` might be desired instead.
    ///
    /// `BeforeScheme` and `AfterFragment` are always the start and end of the entire URL,
    /// so `&url[BeforeScheme..X]` is the same as `&url[..X]`
    /// and `&url[X..AfterFragment]` is the same as `&url[X..]`.
    #[derive(Copy, Clone, Debug)]
    pub enum Position {
        BeforeScheme,
        AfterScheme,
        BeforeUsername,
        AfterUsername,
        BeforePassword,
        AfterPassword,
        BeforeHost,
        AfterHost,
        BeforePort,
        AfterPort,
        BeforePath,
        AfterPath,
        BeforeQuery,
        AfterQuery,
        BeforeFragment,
        AfterFragment,
    }

    impl Url {
        #[inline]
        fn index(&self, position: Position) -> usize {
            match position {
                Position::BeforeScheme => 0,

                Position::AfterScheme => self.scheme_end as usize,

                Position::BeforeUsername => {
                    if self.has_authority() {
                        self.scheme_end as usize + "://".len()
                    } else {
                        debug_assert!(self.byte_at(self.scheme_end) == b':');
                        debug_assert!(self.scheme_end + ":".len() as u32 == self.username_end);
                        self.scheme_end as usize + ":".len()
                    }
                }

                Position::AfterUsername => self.username_end as usize,

                Position::BeforePassword => {
                    if self.has_authority() && self.byte_at(self.username_end) == b':' {
                        self.username_end as usize + ":".len()
                    } else {
                        debug_assert!(self.username_end == self.host_start);
                        self.username_end as usize
                    }
                }

                Position::AfterPassword => {
                    if self.has_authority() && self.byte_at(self.username_end) == b':' {
                        debug_assert!(self.byte_at(self.host_start - "@".len() as u32) == b'@');
                        self.host_start as usize - "@".len()
                    } else {
                        debug_assert!(self.username_end == self.host_start);
                        self.host_start as usize
                    }
                }

                Position::BeforeHost => self.host_start as usize,

                Position::AfterHost => self.host_end as usize,

                Position::BeforePort => {
                    if self.port.is_some() {
                        debug_assert!(self.byte_at(self.host_end) == b':');
                        self.host_end as usize + ":".len()
                    } else {
                        self.host_end as usize
                    }
                }

                Position::AfterPort => self.path_start as usize,

                Position::BeforePath => self.path_start as usize,

                Position::AfterPath => match (self.query_start, self.fragment_start) {
                    (Some(q), _) => q as usize,
                    (None, Some(f)) => f as usize,
                    (None, None) => self.serialization.len(),
                },

                Position::BeforeQuery => match (self.query_start, self.fragment_start) {
                    (Some(q), _) => {
                        debug_assert!(self.byte_at(q) == b'?');
                        q as usize + "?".len()
                    }
                    (None, Some(f)) => f as usize,
                    (None, None) => self.serialization.len(),
                },

                Position::AfterQuery => match self.fragment_start {
                    None => self.serialization.len(),
                    Some(f) => f as usize,
                },

                Position::BeforeFragment => match self.fragment_start {
                    Some(f) => {
                        debug_assert!(self.byte_at(f) == b'#');
                        f as usize + "#".len()
                    }
                    None => self.serialization.len(),
                },

                Position::AfterFragment => self.serialization.len(),
            }
        }
    }