//! Keyboard layouts (ZIG/src/input/keyboard.zig).

use crate::config::OptionAsAlt;

/// Keyboard layouts.
///
/// These aren't heavily used in Ghostty and having a fully comprehensive
/// list is not important. We only need to distinguish between a few
/// different layouts for some nice-to-have features, such as setting a default
/// value for "macos-option-as-alt".
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum Layout {
    /// Unknown, unmapped layout. Ghostty should not make any assumptions
    /// about the layout of the keyboard.
    Unknown,

    // The remaining should be fairly self-explanatory:
    UsStandard,
    UsInternational,
}

impl Layout {
    /// Map an Apple keyboard layout ID to a value in this enum. The layout
    /// ID can be retrieved using Carbon's TIKeyboardLayoutGetInputSourceProperty
    /// function.
    ///
    /// Even though our layout supports "unknown", we return None if we don't
    /// recognize the layout ID so callers can detect this scenario.
    pub fn map_apple_id(id: &str) -> Option<Layout> {
        match id {
            "com.apple.keylayout.US" => Some(Layout::UsStandard),
            "com.apple.keylayout.USInternational" => Some(Layout::UsInternational),
            _ => None,
        }
    }

    /// Returns the default macos-option-as-alt value for this layout.
    ///
    /// We apply some heuristics to change the default based on the keyboard
    /// layout if "macos-option-as-alt" is unset. We do this because on some
    /// keyboard layouts such as US standard layouts, users generally expect
    /// an input such as option-b to map to alt-b but macOS by default will
    /// convert it to the codepoint "∫".
    ///
    /// This behavior however is desired on international layout where the
    /// option key is used for important, regularly used inputs.
    pub fn detect_option_as_alt(self) -> OptionAsAlt {
        match self {
            // On US standard, the option key is typically used as alt
            // and not as a modifier for other codepoints. For example,
            // option-B = ∫ but usually the user wants alt-B.
            Layout::UsStandard | Layout::UsInternational => OptionAsAlt::True,
            Layout::Unknown => OptionAsAlt::False,
        }
    }
}