1 files changed, 186 insertions, 0 deletions
diff --git a/src/dependency_history.rs b/src/dependency_history.rs
new file mode 100644
index 0000000..4e36a7b
--- /dev/null
+++ b/src/dependency_history.rs
@@ -0,0 +1,186 @@
+//! Dependency history.
+
+use std::any::type_name;
+use std::collections::HashSet;
+use std::fmt::{Debug, Display};
+
+const BOLD_MODE: &str = "\x1b[1m";
+const RESET_BOLD_MODE: &str = "\x1b[22m";
+
+/// Dependency history interface.
+///
+/// **This trait is sealed and cannot be implemented for types outside this crate.**
+pub trait IDependencyHistory: private::Sealed
+{
+    #[doc(hidden)]
+    fn push<Dependency: 'static + ?Sized>(&mut self);
+
+    #[doc(hidden)]
+    fn contains<Dependency: 'static + ?Sized>(&self) -> bool;
+}
+
+/// Dependency history.
+#[derive(Clone, Debug)]
+pub struct DependencyHistory
+{
+    inner: Vec<&'static str>,
+}
+
+impl DependencyHistory
+{
+    #[must_use]
+    pub(crate) fn new() -> Self
+    {
+        Self { inner: vec![] }
+    }
+}
+
+impl IDependencyHistory for DependencyHistory
+{
+    #[doc(hidden)]
+    fn push<Dependency: 'static + ?Sized>(&mut self)
+    {
+        self.inner.push(type_name::<Dependency>());
+    }
+
+    #[doc(hidden)]
+    fn contains<Dependency: 'static + ?Sized>(&self) -> bool
+    {
+        self.inner.contains(&type_name::<Dependency>())
+    }
+}
+
+impl Display for DependencyHistory
+{
+    fn fmt(&self, formatter: &mut std::fmt::Formatter<'_>) -> std::fmt::Result
+    {
+        let mut found_items = HashSet::new();
+
+        let opt_dupe_item = self.inner.iter().find(|item| {
+            if found_items.contains(item) {
+                return true;
+            }
+
+            found_items.insert(*item);
+
+            false
+        });
+
+        for (index, item) in self.inner.iter().enumerate() {
+            let mut item_is_dupe = false;
+
+            if let Some(dupe_item) = opt_dupe_item {
+                if *item == *dupe_item {
+                    formatter
+                        .write_fmt(format_args!("{BOLD_MODE}{item}{RESET_BOLD_MODE}"))?;
+
+                    item_is_dupe = true;
+                }
+            }
+
+            if !item_is_dupe {
+                formatter.write_str(item)?;
+            }
+
+            if index != self.inner.len() - 1 {
+                formatter.write_str(" -> ")?;
+            }
+        }
+
+        if opt_dupe_item.is_some() {
+            formatter.write_str(" -> ...")?;
+        }
+
+        Ok(())
+    }
+}
+
+impl Default for DependencyHistory
+{
+    fn default() -> Self
+    {
+        Self::new()
+    }
+}
+
+impl private::Sealed for DependencyHistory {}
+
+pub(crate) mod private
+{
+    pub trait Sealed {}
+}
+
+#[cfg(test)]
+mod tests
+{
+    use super::*;
+    use crate::test_utils::subjects;
+
+    #[test]
+    fn can_push()
+    {
+        let mut dependency_history = DependencyHistory::new();
+
+        dependency_history.push::<dyn subjects::INumber>();
+
+        assert!(dependency_history
+            .inner
+            .contains(&type_name::<dyn subjects::INumber>()));
+    }
+
+    #[test]
+    fn contains_works()
+    {
+        let mut dependency_history = DependencyHistory::new();
+
+        dependency_history
+            .inner
+            .push(type_name::<dyn subjects::IUserManager>());
+
+        assert!(dependency_history.contains::<dyn subjects::IUserManager>());
+
+        assert!(!dependency_history.contains::<dyn subjects::INumber>());
+    }
+
+    #[test]
+    fn display_works()
+    {
+        trait Ninja {}
+        trait Katana {}
+        trait Blade {}
+
+        let mut dependency_history = DependencyHistory::new();
+
+        dependency_history.inner.push(type_name::<dyn Ninja>());
+        dependency_history.inner.push(type_name::<dyn Katana>());
+        dependency_history.inner.push(type_name::<dyn Blade>());
+
+        assert_eq!(
+            dependency_history.to_string(),
+            format!(
+                "{} -> {} -> {}",
+                type_name::<dyn Ninja>(),
+                type_name::<dyn Katana>(),
+                type_name::<dyn Blade>()
+            )
+        );
+
+        dependency_history.inner.push(type_name::<dyn Katana>());
+
+        assert_eq!(
+            dependency_history.to_string(),
+            format!(
+                concat!(
+                    "{} -> {bold_mode}{}{reset_bold_mode} -> {} -> ",
+                    "{bold_mode}{}{reset_bold_mode} -> ...",
+                ),
+                type_name::<dyn Ninja>(),
+                type_name::<dyn Katana>(),
+                type_name::<dyn Blade>(),
+                type_name::<dyn Katana>(),
+                bold_mode = BOLD_MODE,
+                reset_bold_mode = RESET_BOLD_MODE
+            )
+        );
+    }
+}