// matchers.rs

//

// Copyright 2019 Raphaël Gomès <rgomes@octobus.net>

//

// This software may be used and distributed according to the terms of the

// GNU General Public License version 2 or any later version.

//! Structs and types for matching files and directories.

use std::collections::HashSet;

use std::iter::FromIterator;

use std::ops::Deref;

#[derive(Debug, PartialEq)]

pub enum VisitChildrenSet<'a> {

    /// Don't visit anything

    Empty,

    /// Only visit this directory

    This,

    /// Visit this directory and these subdirectories

    /// TODO Should we implement a `NonEmptyHashSet`?

    Set(HashSet<&'a HgPath>),

    /// Visit this directory and all subdirectories

    Recursive,

}

pub trait Matcher {

    /// Explicitly listed files

    fn file_set(&self) -> Option<&HashSet<&HgPath>>;

    /// Returns whether `filename` is in `file_set`

    fn exact_match(&self, filename: impl AsRef<HgPath>) -> bool;

    /// Returns whether `filename` is matched by this matcher

    fn matches(&self, filename: impl AsRef<HgPath>) -> bool;

    /// Decides whether a directory should be visited based on whether it

    /// has potential matches in it or one of its subdirectories, and

    /// potentially lists which subdirectories of that directory should be

    /// visited. This is based on the match's primary, included, and excluded

    /// patterns.

    ///

    /// # Example

    ///

    /// Assume matchers `['path:foo/bar', 'rootfilesin:qux']`, we would

    /// return the following values (assuming the implementation of

    /// visit_children_set is capable of recognizing this; some implementations

    /// are not).

    ///

    /// ```text

    /// ```ignore

    /// '' -> {'foo', 'qux'}

    /// 'baz' -> set()

    /// 'foo' -> {'bar'}

    /// // Ideally this would be `Recursive`, but since the prefix nature of

    /// // matchers is applied to the entire matcher, we have to downgrade this

    /// // to `This` due to the (yet to be implemented in Rust) non-prefix

    /// // `RootFilesIn'-kind matcher being mixed in.

    /// 'foo/bar' -> 'this'

    /// 'qux' -> 'this'

    /// ```

    /// # Important

    ///

    /// Most matchers do not know if they're representing files or

    /// directories. They see `['path:dir/f']` and don't know whether `f` is a

    /// file or a directory, so `visit_children_set('dir')` for most matchers

    /// will return `HashSet{ HgPath { "f" } }`, but if the matcher knows it's

    /// a file (like the yet to be implemented in Rust `ExactMatcher` does),

    /// it may return `VisitChildrenSet::This`.

    /// Do not rely on the return being a `HashSet` indicating that there are

    /// no files in this dir to investigate (or equivalently that if there are

    /// files to investigate in 'dir' that it will always return

    /// `VisitChildrenSet::This`).

    fn visit_children_set(

        &self,

        directory: impl AsRef<HgPath>,

    ) -> VisitChildrenSet;

    /// Matcher will match everything and `files_set()` will be empty:

    /// optimization might be possible.

    fn matches_everything(&self) -> bool;

    /// Matcher will match exactly the files in `files_set()`: optimization

    /// might be possible.

    fn is_exact(&self) -> bool;

}

/// Matches everything.

///```

/// use hg::{ matchers::{Matcher, AlwaysMatcher}, utils::hg_path::HgPath };

///

/// let matcher = AlwaysMatcher;

///

/// assert_eq!(matcher.matches(HgPath::new(b"whatever")), true);

/// assert_eq!(matcher.matches(HgPath::new(b"b.txt")), true);

/// assert_eq!(matcher.matches(HgPath::new(b"main.c")), true);

/// assert_eq!(matcher.matches(HgPath::new(br"re:.*\.c$")), true);

/// ```

#[derive(Debug)]

pub struct AlwaysMatcher;

impl Matcher for AlwaysMatcher {

    fn file_set(&self) -> Option<&HashSet<&HgPath>> {

        None

    }

    fn exact_match(&self, _filename: impl AsRef<HgPath>) -> bool {

        false

    }

    fn matches(&self, _filename: impl AsRef<HgPath>) -> bool {

        true

    }

    fn visit_children_set(

        &self,

        _directory: impl AsRef<HgPath>,

    ) -> VisitChildrenSet {

        VisitChildrenSet::Recursive

    }

    fn matches_everything(&self) -> bool {

        true

    }

    fn is_exact(&self) -> bool {

        false

    }

}

/// Matches the input files exactly. They are interpreted as paths, not

/// patterns.

///

///```

/// use hg::{ matchers::{Matcher, FileMatcher}, utils::hg_path::HgPath };

///

/// let files = [HgPath::new(b"a.txt"), HgPath::new(br"re:.*\.c$")];

/// let matcher = FileMatcher::new(&files).unwrap();

///

/// assert_eq!(matcher.matches(HgPath::new(b"a.txt")), true);

/// assert_eq!(matcher.matches(HgPath::new(b"b.txt")), false);

/// assert_eq!(matcher.matches(HgPath::new(b"main.c")), false);

/// assert_eq!(matcher.matches(HgPath::new(br"re:.*\.c$")), true);

/// ```

#[derive(Debug)]

pub struct FileMatcher<'a> {

    files: HashSet<&'a HgPath>,

    dirs: DirsMultiset,

}

impl<'a> FileMatcher<'a> {

    pub fn new(

        files: &'a [impl AsRef<HgPath>],

    ) -> Result<Self, DirstateMapError> {

        Ok(Self {

            files: HashSet::from_iter(files.iter().map(|f| f.as_ref())),

            dirs: DirsMultiset::from_manifest(files)?,

        })

    }

    fn inner_matches(&self, filename: impl AsRef<HgPath>) -> bool {

        self.files.contains(filename.as_ref())

    }

}

impl<'a> Matcher for FileMatcher<'a> {

    fn file_set(&self) -> Option<&HashSet<&HgPath>> {

        Some(&self.files)

    }

    fn exact_match(&self, filename: impl AsRef<HgPath>) -> bool {

        self.inner_matches(filename)

    }

    fn matches(&self, filename: impl AsRef<HgPath>) -> bool {

        self.inner_matches(filename)

    }

    fn visit_children_set(

        &self,

        directory: impl AsRef<HgPath>,

    ) -> VisitChildrenSet {

        if self.files.is_empty() || !self.dirs.contains(&directory) {

            return VisitChildrenSet::Empty;

        }

        let dirs_as_set = self.dirs.iter().map(|k| k.deref()).collect();

        let mut candidates: HashSet<&HgPath> =

            self.files.union(&dirs_as_set).map(|k| *k).collect();

        candidates.remove(HgPath::new(b""));

        if !directory.as_ref().is_empty() {

            let directory = [directory.as_ref().as_bytes(), b"/"].concat();

            candidates = candidates

                .iter()

                .filter_map(|c| {

                    if c.as_bytes().starts_with(&directory) {

                        Some(HgPath::new(&c.as_bytes()[directory.len()..]))

                    } else {

                        None

                    }

                })

                .collect();

        }

        // `self.dirs` includes all of the directories, recursively, so if

        // we're attempting to match 'foo/bar/baz.txt', it'll have '', 'foo',

        // 'foo/bar' in it. Thus we can safely ignore a candidate that has a

        // '/' in it, indicating it's for a subdir-of-a-subdir; the immediate

        // subdir will be in there without a slash.

        VisitChildrenSet::Set(

            candidates

                .iter()

                .filter_map(|c| {

                    if c.bytes().all(|b| *b != b'/') {

                        Some(*c)

                    } else {

                        None

                    }

                })

                .collect(),

        )

    }

    fn matches_everything(&self) -> bool {

        false

    }

    fn is_exact(&self) -> bool {

        true

    }

}

#[cfg(test)]

mod tests {

    use super::*;

    use pretty_assertions::assert_eq;

    #[test]

    fn test_filematcher_visit_children_set() {

        // Visitchildrenset

        let files = vec![HgPath::new(b"dir/subdir/foo.txt")];

        let matcher = FileMatcher::new(&files).unwrap();

        let mut set = HashSet::new();

        set.insert(HgPath::new(b"dir"));

        assert_eq!(

            matcher.visit_children_set(HgPath::new(b"")),

            VisitChildrenSet::Set(set)

        );

        let mut set = HashSet::new();

        set.insert(HgPath::new(b"subdir"));

        assert_eq!(

            matcher.visit_children_set(HgPath::new(b"dir")),

            VisitChildrenSet::Set(set)

        );

        let mut set = HashSet::new();

        set.insert(HgPath::new(b"foo.txt"));

        assert_eq!(

            matcher.visit_children_set(HgPath::new(b"dir/subdir")),

            VisitChildrenSet::Set(set)

        );

        assert_eq!(

            matcher.visit_children_set(HgPath::new(b"dir/subdir/x")),

            VisitChildrenSet::Empty

        );

        assert_eq!(

            matcher.visit_children_set(HgPath::new(b"dir/subdir/foo.txt")),

            VisitChildrenSet::Empty

        );

        assert_eq!(

            matcher.visit_children_set(HgPath::new(b"folder")),

            VisitChildrenSet::Empty

        );

    }

    #[test]

    fn test_filematcher_visit_children_set_files_and_dirs() {

        let files = vec![

            HgPath::new(b"rootfile.txt"),

            HgPath::new(b"a/file1.txt"),

            HgPath::new(b"a/b/file2.txt"),

            // No file in a/b/c

            HgPath::new(b"a/b/c/d/file4.txt"),

        ];

        let matcher = FileMatcher::new(&files).unwrap();

        let mut set = HashSet::new();

        set.insert(HgPath::new(b"a"));

        set.insert(HgPath::new(b"rootfile.txt"));

        assert_eq!(

            matcher.visit_children_set(HgPath::new(b"")),

            VisitChildrenSet::Set(set)

        );

        let mut set = HashSet::new();

        set.insert(HgPath::new(b"b"));

        set.insert(HgPath::new(b"file1.txt"));

        assert_eq!(

            matcher.visit_children_set(HgPath::new(b"a")),

            VisitChildrenSet::Set(set)

        );

        let mut set = HashSet::new();

        set.insert(HgPath::new(b"c"));

        set.insert(HgPath::new(b"file2.txt"));

        assert_eq!(

            matcher.visit_children_set(HgPath::new(b"a/b")),

            VisitChildrenSet::Set(set)

        );

        let mut set = HashSet::new();

        set.insert(HgPath::new(b"d"));

        assert_eq!(

            matcher.visit_children_set(HgPath::new(b"a/b/c")),

            VisitChildrenSet::Set(set)

        );

        let mut set = HashSet::new();

        set.insert(HgPath::new(b"file4.txt"));

        assert_eq!(

            matcher.visit_children_set(HgPath::new(b"a/b/c/d")),

            VisitChildrenSet::Set(set)

        );

        assert_eq!(

            matcher.visit_children_set(HgPath::new(b"a/b/c/d/e")),

            VisitChildrenSet::Empty

        );

        assert_eq!(

            matcher.visit_children_set(HgPath::new(b"folder")),

            VisitChildrenSet::Empty

        );

    }

}