// 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;

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).

    ///

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

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

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

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

/// ```

#[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

    }

}