1 files changed, 145 insertions, 0 deletions
diff --git a/core/src/menu.rs b/core/src/menu.rs
new file mode 100644
index 00000000..8a679085
--- /dev/null
+++ b/core/src/menu.rs
@@ -0,0 +1,145 @@
+//! Build menus for your application.
+use crate::keyboard::Hotkey;
+
+/// Menu representation.
+///
+/// This can be used by `shell` implementations to create a menu.
+#[derive(Debug, Clone)]
+pub struct Menu<Message> {
+    entries: Vec<Entry<Message>>,
+}
+
+impl<Message> PartialEq for Menu<Message> {
+    fn eq(&self, other: &Self) -> bool {
+        self.entries == other.entries
+    }
+}
+
+impl<Message> Menu<Message> {
+    /// Creates an empty [`Menu`].
+    pub fn new() -> Self {
+        Self::with_entries(Vec::new())
+    }
+
+    /// Creates a new [`Menu`] with the given entries.
+    pub fn with_entries(entries: Vec<Entry<Message>>) -> Self {
+        Self { entries }
+    }
+
+    /// Returns a [`MenuEntry`] iterator.
+    pub fn iter(&self) -> impl Iterator<Item = &Entry<Message>> {
+        self.entries.iter()
+    }
+
+    /// Adds an [`Entry`] to the [`Menu`].
+    pub fn push(mut self, entry: Entry<Message>) -> Self {
+        self.entries.push(entry);
+        self
+    }
+
+    /// Maps the `Message` of the [`Menu`] using the provided function.
+    ///
+    /// This is useful to compose menus and split them into different
+    /// abstraction levels.
+    pub fn map<B>(self, f: impl Fn(Message) -> B + Copy) -> Menu<B> {
+        // TODO: Use a boxed trait to avoid reallocation of entries
+        Menu {
+            entries: self
+                .entries
+                .into_iter()
+                .map(|entry| entry.map(f))
+                .collect(),
+        }
+    }
+}
+
+/// Represents one of the possible entries used to build a [`Menu`].
+#[derive(Debug, Clone)]
+pub enum Entry<Message> {
+    /// Item for a [`Menu`]
+    Item {
+        /// The title of the item
+        title: String,
+        /// The [`Hotkey`] to activate the item, if any
+        hotkey: Option<Hotkey>,
+        /// The message generated when the item is activated
+        on_activation: Message,
+    },
+    /// Dropdown for a [`Menu`]
+    Dropdown {
+        /// Title of the dropdown
+        title: String,
+        /// The submenu of the dropdown
+        submenu: Menu<Message>,
+    },
+    /// Separator for a [`Menu`]
+    Separator,
+}
+
+impl<Message> Entry<Message> {
+    /// Creates an [`Entry::Item`].
+    pub fn item<S: Into<String>>(
+        title: S,
+        hotkey: impl Into<Option<Hotkey>>,
+        on_activation: Message,
+    ) -> Self {
+        let title = title.into();
+        let hotkey = hotkey.into();
+
+        Self::Item {
+            title,
+            hotkey,
+            on_activation,
+        }
+    }
+
+    /// Creates an [`Entry::Dropdown`].
+    pub fn dropdown<S: Into<String>>(title: S, submenu: Menu<Message>) -> Self {
+        let title = title.into();
+
+        Self::Dropdown { title, submenu }
+    }
+
+    fn map<B>(self, f: impl Fn(Message) -> B + Copy) -> Entry<B> {
+        match self {
+            Self::Item {
+                title,
+                hotkey,
+                on_activation,
+            } => Entry::Item {
+                title,
+                hotkey,
+                on_activation: f(on_activation),
+            },
+            Self::Dropdown { title, submenu } => Entry::Dropdown {
+                title,
+                submenu: submenu.map(f),
+            },
+            Self::Separator => Entry::Separator,
+        }
+    }
+}
+
+impl<Message> PartialEq for Entry<Message> {
+    fn eq(&self, other: &Self) -> bool {
+        match (self, other) {
+            (
+                Entry::Item { title, hotkey, .. },
+                Entry::Item {
+                    title: other_title,
+                    hotkey: other_hotkey,
+                    ..
+                },
+            ) => title == other_title && hotkey == other_hotkey,
+            (
+                Entry::Dropdown { title, submenu },
+                Entry::Dropdown {
+                    title: other_title,
+                    submenu: other_submenu,
+                },
+            ) => title == other_title && submenu == other_submenu,
+            (Entry::Separator, Entry::Separator) => true,
+            _ => false,
+        }
+    }
+}