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

/// 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<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();
    debug_assert!(url.byte_at(url.path_start) == b'/');
    PathSegmentsMut {
        after_first_slash: url.path_start as usize + "/".len(),
        url: url,
        old_after_path_position: old_after_path_position,
        after_path: 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<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<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.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 {
        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<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<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 {
                    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
    }
}