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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::parser::{self, to_u32, SchemeType};
    use crate::Url;
    use std::str;

    /// Exposes methods to manipulate the path of an URL that is not cannot-be-base.
    ///
    /// The path always starts with a `/` slash, and is made of slash-separated segments.
    /// There is always at least one segment (which may be the empty string).
    ///
    /// Examples:
    ///
    /// ```rust
    /// use url::Url;
    /// # use std::error::Error;
    ///
    /// # fn run() -> Result<(), Box<dyn Error>> {
    /// let mut url = Url::parse("mailto:me@example.com")?;
    /// assert!(url.path_segments_mut().is_err());
    ///
    /// let mut url = Url::parse("http://example.net/foo/index.html")?;
    /// url.path_segments_mut().map_err(|_| "cannot be base")?
    ///     .pop().push("img").push("2/100%.png");
    /// assert_eq!(url.as_str(), "http://example.net/foo/img/2%2F100%25.png");
    /// # Ok(())
    /// # }
    /// # run().unwrap();
    /// ```
    #[derive(Debug)]
    pub struct PathSegmentsMut<'a> {
        url: &'a mut Url,
        after_first_slash: usize,
        after_path: String,
        old_after_path_position: u32,
    }

    // Not re-exported outside the crate
    pub fn new(url: &mut Url) -> PathSegmentsMut<'_> {
        let after_path = url.take_after_path();
        let old_after_path_position = to_u32(url.serialization.len()).unwrap();
        // Special urls always have a non empty path
        if SchemeType::from(url.scheme()).is_special() {
            debug_assert!(url.byte_at(url.path_start) == b'/');
        } else {
            debug_assert!(
                url.serialization.len() == url.path_start as usize
                    || url.byte_at(url.path_start) == b'/'
            );
        }
        PathSegmentsMut {
            after_first_slash: url.path_start as usize + "/".len(),
            url,
            old_after_path_position,
            after_path,
        }
    }

    impl<'a> Drop for PathSegmentsMut<'a> {
        fn drop(&mut self) {
            self.url
                .restore_after_path(self.old_after_path_position, &self.after_path)
        }
    }

    impl<'a> PathSegmentsMut<'a> {
        /// Remove all segments in the path, leaving the minimal `url.path() == "/"`.
        ///
        /// Returns `&mut Self` so that method calls can be chained.
        ///
        /// Example:
        ///
        /// ```rust
        /// use url::Url;
        /// # use std::error::Error;
        ///
        /// # fn run() -> Result<(), Box<dyn Error>> {
        /// let mut url = Url::parse("https://github.com/servo/rust-url/")?;
        /// url.path_segments_mut().map_err(|_| "cannot be base")?
        ///     .clear().push("logout");
        /// assert_eq!(url.as_str(), "https://github.com/logout");
        /// # Ok(())
        /// # }
        /// # run().unwrap();
        /// ```
        pub fn clear(&mut self) -> &mut Self {
            self.url.serialization.truncate(self.after_first_slash);
            self
        }

        /// Remove the last segment of this URL’s path if it is empty,
        /// except if these was only one segment to begin with.
        ///
        /// In other words, remove one path trailing slash, if any,
        /// unless it is also the initial slash (so this does nothing if `url.path() == "/")`.
        ///
        /// Returns `&mut Self` so that method calls can be chained.
        ///
        /// Example:
        ///
        /// ```rust
        /// use url::Url;
        /// # use std::error::Error;
        ///
        /// # fn run() -> Result<(), Box<dyn Error>> {
        /// let mut url = Url::parse("https://github.com/servo/rust-url/")?;
        /// url.path_segments_mut().map_err(|_| "cannot be base")?
        ///     .push("pulls");
        /// assert_eq!(url.as_str(), "https://github.com/servo/rust-url//pulls");
        ///
        /// let mut url = Url::parse("https://github.com/servo/rust-url/")?;
        /// url.path_segments_mut().map_err(|_| "cannot be base")?
        ///     .pop_if_empty().push("pulls");
        /// assert_eq!(url.as_str(), "https://github.com/servo/rust-url/pulls");
        /// # Ok(())
        /// # }
        /// # run().unwrap();
        /// ```
        pub fn pop_if_empty(&mut self) -> &mut Self {
            if self.after_first_slash >= self.url.serialization.len() {
                return self;
            }
            if self.url.serialization[self.after_first_slash..].ends_with('/') {
                self.url.serialization.pop();
            }
            self
        }

        /// Remove the last segment of this URL’s path.
        ///
        /// If the path only has one segment, make it empty such that `url.path() == "/"`.
        ///
        /// Returns `&mut Self` so that method calls can be chained.
        pub fn pop(&mut self) -> &mut Self {
            if self.after_first_slash >= self.url.serialization.len() {
                return self;
            }
            let last_slash = self.url.serialization[self.after_first_slash..]
                .rfind('/')
                .unwrap_or(0);
            self.url
                .serialization
                .truncate(self.after_first_slash + last_slash);
            self
        }

        /// Append the given segment at the end of this URL’s path.
        ///
        /// See the documentation for `.extend()`.
        ///
        /// Returns `&mut Self` so that method calls can be chained.
        pub fn push(&mut self, segment: &str) -> &mut Self {
            self.extend(Some(segment))
        }

        /// Append each segment from the given iterator at the end of this URL’s path.
        ///
        /// Each segment is percent-encoded like in `Url::parse` or `Url::join`,
        /// except that `%` and `/` characters are also encoded (to `%25` and `%2F`).
        /// This is unlike `Url::parse` where `%` is left as-is in case some of the input
        /// is already percent-encoded, and `/` denotes a path segment separator.)
        ///
        /// Note that, in addition to slashes between new segments,
        /// this always adds a slash between the existing path and the new segments
        /// *except* if the existing path is `"/"`.
        /// If the previous last segment was empty (if the path had a trailing slash)
        /// the path after `.extend()` will contain two consecutive slashes.
        /// If that is undesired, call `.pop_if_empty()` first.
        ///
        /// To obtain a behavior similar to `Url::join`, call `.pop()` unconditionally first.
        ///
        /// Returns `&mut Self` so that method calls can be chained.
        ///
        /// Example:
        ///
        /// ```rust
        /// use url::Url;
        /// # use std::error::Error;
        ///
        /// # fn run() -> Result<(), Box<dyn Error>> {
        /// let mut url = Url::parse("https://github.com/")?;
        /// let org = "servo";
        /// let repo = "rust-url";
        /// let issue_number = "188";
        /// url.path_segments_mut().map_err(|_| "cannot be base")?
        ///     .extend(&[org, repo, "issues", issue_number]);
        /// assert_eq!(url.as_str(), "https://github.com/servo/rust-url/issues/188");
        /// # Ok(())
        /// # }
        /// # run().unwrap();
        /// ```
        ///
        /// In order to make sure that parsing the serialization of an URL gives the same URL,
        /// a segment is ignored if it is `"."` or `".."`:
        ///
        /// ```rust
        /// use url::Url;
        /// # use std::error::Error;
        ///
        /// # fn run() -> Result<(), Box<dyn Error>> {
        /// let mut url = Url::parse("https://github.com/servo")?;
        /// url.path_segments_mut().map_err(|_| "cannot be base")?
        ///     .extend(&["..", "rust-url", ".", "pulls"]);
        /// assert_eq!(url.as_str(), "https://github.com/servo/rust-url/pulls");
        /// # Ok(())
        /// # }
        /// # run().unwrap();
        /// ```
        pub fn extend<I>(&mut self, segments: I) -> &mut Self
        where
            I: IntoIterator,
            I::Item: AsRef<str>,
        {
            let scheme_type = SchemeType::from(self.url.scheme());
            let path_start = self.url.path_start as usize;
            self.url.mutate(|parser| {
                parser.context = parser::Context::PathSegmentSetter;
                for segment in segments {
                    let segment = segment.as_ref();
                    if matches!(segment, "." | "..") {
                        continue;
                    }
                    if parser.serialization.len() > path_start + 1
                        // Non special url's path might still be empty
                        || parser.serialization.len() == path_start
                    {
                        parser.serialization.push('/');
                    }
                    let mut has_host = true; // FIXME account for this?
                    parser.parse_path(
                        scheme_type,
                        &mut has_host,
                        path_start,
                        parser::Input::new(segment),
                    );
                }
            });
            self
        }
    }