Add filter to LogWalker

This is the first step towards adding a file history view. The filter
itself is not related to files specifically, though. It could also be
used for different purposes.

asyncgit/src/sync/logwalker.rs

@@ -28,11 +28,16 @@ impl<'a> Ord for TimeOrderedCommit<'a> {
     }
 }
 
+type LogWalkerFilter =
+    Box<dyn Fn(&Repository, &CommitId) -> Result<bool>>;
+
 ///
 pub struct LogWalker<'a> {
     commits: BinaryHeap<TimeOrderedCommit<'a>>,
     visited: HashSet<Oid>,
     limit: usize,
+    repo: &'a Repository,
+    filter: Option<LogWalkerFilter>,
 }
 
 impl<'a> LogWalker<'a> {
@@ -47,9 +52,19 @@ impl<'a> LogWalker<'a> {
             commits,
             limit,
             visited: HashSet::with_capacity(1000),
+            repo,
+            filter: None,
         })
     }
 
+    ///
+    pub fn filter(self, filter: LogWalkerFilter) -> Self {
+        Self {
+            filter: Some(filter),
+            ..self
+        }
+    }
+
     ///
     pub fn read(&mut self, out: &mut Vec<CommitId>) -> Result<usize> {
         let mut count = 0_usize;
@@ -59,7 +74,17 @@ impl<'a> LogWalker<'a> {
                 self.visit(p);
             }
 
-            out.push(c.0.id().into());
+            let id: CommitId = c.0.id().into();
+            let commit_should_be_included =
+                if let Some(ref filter) = self.filter {
+                    filter(self.repo, &id)?
+                } else {
+                    true
+                };
+
+            if commit_should_be_included {
+                out.push(id);
+            }
 
             count += 1;
             if count == self.limit {
@@ -82,9 +107,10 @@ impl<'a> LogWalker<'a> {
 #[cfg(test)]
 mod tests {
     use super::*;
+    use crate::error::Result;
     use crate::sync::{
-        commit, get_commits_info, stage_add_file,
-        tests::repo_init_empty,
+        commit, commit_files::get_commit_diff, get_commits_info,
+        stage_add_file, tests::repo_init_empty,
     };
     use pretty_assertions::assert_eq;
     use std::{fs::File, io::Write, path::Path};
@@ -144,4 +170,79 @@ mod tests {
 
         Ok(())
     }
+
+    #[test]
+    fn test_logwalker_with_filter() -> Result<()> {
+        let file_path = Path::new("foo");
+        let second_file_path = Path::new("baz");
+        let (_td, repo) = repo_init_empty().unwrap();
+        let root = repo.path().parent().unwrap();
+        let repo_path = root.as_os_str().to_str().unwrap();
+
+        File::create(&root.join(file_path))?.write_all(b"a")?;
+        stage_add_file(repo_path, file_path).unwrap();
+
+        let _first_commit_id = commit(repo_path, "commit1").unwrap();
+
+        File::create(&root.join(second_file_path))?
+            .write_all(b"a")?;
+        stage_add_file(repo_path, second_file_path).unwrap();
+
+        let second_commit_id = commit(repo_path, "commit2").unwrap();
+
+        File::create(&root.join(file_path))?.write_all(b"b")?;
+        stage_add_file(repo_path, file_path).unwrap();
+
+        let _third_commit_id = commit(repo_path, "commit3").unwrap();
+
+        let diff_contains_baz = |repo: &Repository,
+                                 commit_id: &CommitId|
+         -> Result<bool> {
+            let diff = get_commit_diff(
+                &repo,
+                *commit_id,
+                Some("baz".into()),
+            )?;
+
+            let contains_file = diff.deltas().len() > 0;
+
+            Ok(contains_file)
+        };
+
+        let mut items = Vec::new();
+        let mut walker = LogWalker::new(&repo, 100)?
+            .filter(Box::new(diff_contains_baz));
+        walker.read(&mut items).unwrap();
+
+        assert_eq!(items.len(), 1);
+        assert_eq!(items[0], second_commit_id.into());
+
+        let mut items = Vec::new();
+        walker.read(&mut items).unwrap();
+
+        assert_eq!(items.len(), 0);
+
+        let diff_contains_bar = |repo: &Repository,
+                                 commit_id: &CommitId|
+         -> Result<bool> {
+            let diff = get_commit_diff(
+                &repo,
+                *commit_id,
+                Some("bar".into()),
+            )?;
+
+            let contains_file = diff.deltas().len() > 0;
+
+            Ok(contains_file)
+        };
+
+        let mut items = Vec::new();
+        let mut walker = LogWalker::new(&repo, 100)?
+            .filter(Box::new(diff_contains_bar));
+        walker.read(&mut items).unwrap();
+
+        assert_eq!(items.len(), 0);
+
+        Ok(())
+    }
 }