Split modules (#86)

* Split diffing to separate module
* Split assets to separate module

src/diff.rs

@@ -0,0 +1,76 @@
+use git2::{DiffOptions, IntoCString, Repository};
+use std::collections::HashMap;
+use std::fs;
+use std::path::Path;
+
+#[derive(Copy, Clone, Debug)]
+pub enum LineChange {
+    Added,
+    RemovedAbove,
+    RemovedBelow,
+    Modified,
+}
+
+pub type LineChanges = HashMap<u32, LineChange>;
+
+pub fn get_git_diff(filename: &str) -> Option<LineChanges> {
+    let repo = Repository::discover(&filename).ok()?;
+    let path_absolute = fs::canonicalize(&filename).ok()?;
+    let path_relative_to_repo = path_absolute.strip_prefix(repo.workdir()?).ok()?;
+
+    let mut diff_options = DiffOptions::new();
+    let pathspec = path_relative_to_repo.into_c_string().ok()?;
+    diff_options.pathspec(pathspec);
+    diff_options.context_lines(0);
+
+    let diff = repo.diff_index_to_workdir(None, Some(&mut diff_options))
+        .ok()?;
+
+    let mut line_changes: LineChanges = HashMap::new();
+
+    let mark_section =
+        |line_changes: &mut LineChanges, start: u32, end: i32, change: LineChange| {
+            for line in start..(end + 1) as u32 {
+                line_changes.insert(line, change);
+            }
+        };
+
+    let _ = diff.foreach(
+        &mut |_, _| true,
+        None,
+        Some(&mut |delta, hunk| {
+            let path = delta.new_file().path().unwrap_or_else(|| Path::new(""));
+
+            if path_relative_to_repo != path {
+                return false;
+            }
+
+            let old_lines = hunk.old_lines();
+            let new_start = hunk.new_start();
+            let new_lines = hunk.new_lines();
+            let new_end = (new_start + new_lines) as i32 - 1;
+
+            if old_lines == 0 && new_lines > 0 {
+                mark_section(&mut line_changes, new_start, new_end, LineChange::Added);
+            } else if new_lines == 0 && old_lines > 0 {
+                if new_start == 0 {
+                    mark_section(&mut line_changes, 1, 1, LineChange::RemovedAbove);
+                } else {
+                    mark_section(
+                        &mut line_changes,
+                        new_start,
+                        new_start as i32,
+                        LineChange::RemovedBelow,
+                    );
+                }
+            } else {
+                mark_section(&mut line_changes, new_start, new_end, LineChange::Modified);
+            }
+
+            true
+        }),
+        None,
+    );
+
+    Some(line_changes)
+}