//! macOS Adapter
//!
//! Reads AppKit's semantic colors in the effective appearance and watches
//! the system's color preferences.

use objc2::rc::Retained;
use objc2::runtime::{NSObjectProtocol, ProtocolObject};
use objc2_app_kit::{
    NSAppearance, NSAppearanceNameAqua, NSAppearanceNameDarkAqua, NSColor, NSColorSpace,
    NSWorkspace,
};
use objc2_foundation::{
    NSDistributedNotificationCenter, NSNotification, NSNotificationName, NSOperationQueue,
};
use std::ptr::NonNull;

use super::ThemeSource;
use crate::ThemeVariant;
use crate::system::{AccessibilityPreferences, PartialPalette, SourceKind, SystemTheme};

/// Default control radius for macOS controls.
const CONTROL_RADIUS_PTS: f32 = 6.0;

#[derive(Default)]
pub(crate) struct MacosSource {
    _observers: Vec<Retained<ProtocolObject<dyn NSObjectProtocol>>>,
}

impl MacosSource {
    fn color_to_hsla(color: &NSColor) -> Option<gpui::Hsla> {
        let srgb = NSColorSpace::sRGBColorSpace();
        let converted = color.colorUsingColorSpace(&srgb)?;

        Some(gpui::Hsla::from(gpui::Rgba {
            r: converted.redComponent() as f32,
            g: converted.greenComponent() as f32,
            b: converted.blueComponent() as f32,
            a: converted.alphaComponent() as f32,
        }))
    }

    /// Resolves the semantic colors with `variant` as the current drawing appearance.
    fn snapshot_in_appearance(&self, variant: ThemeVariant) -> PartialPalette {
        let name = match variant {
            ThemeVariant::Light => {
                // SAFETY: extern statics exported by AppKit, always initialized.
                unsafe { NSAppearanceNameAqua }
            }
            ThemeVariant::Dark => {
                // SAFETY: as above.
                unsafe { NSAppearanceNameDarkAqua }
            }
        };

        let Some(appearance) = NSAppearance::appearanceNamed(name) else {
            return self.read_palette();
        };

        let palette = std::cell::Cell::new(PartialPalette::default());
        appearance.performAsCurrentDrawingAppearance(&block2::RcBlock::new(|| {
            palette.set(self.read_palette());
        }));

        palette.into_inner()
    }

    fn read_palette(&self) -> PartialPalette {
        PartialPalette {
            background: Self::color_to_hsla(&NSColor::windowBackgroundColor()),
            foreground: Self::color_to_hsla(&NSColor::labelColor()),
            surface: Self::color_to_hsla(&NSColor::textBackgroundColor()),
            surface_foreground: Self::color_to_hsla(&NSColor::labelColor()),
            primary_foreground: Self::color_to_hsla(&NSColor::alternateSelectedControlTextColor()),
            accent_foreground: Self::color_to_hsla(&NSColor::alternateSelectedControlTextColor()),
            secondary: None,
            secondary_foreground: Self::color_to_hsla(&NSColor::secondaryLabelColor()),
            muted: None,
            muted_foreground: Self::color_to_hsla(&NSColor::secondaryLabelColor()),
            destructive: Self::color_to_hsla(&NSColor::systemRedColor()),
            border: Self::color_to_hsla(&NSColor::separatorColor()),
            input: Self::color_to_hsla(&NSColor::controlBackgroundColor()),
            ring: Self::color_to_hsla(&NSColor::keyboardFocusIndicatorColor()),
            selection: Self::color_to_hsla(&NSColor::selectedTextBackgroundColor()),
        }
    }
}

impl ThemeSource for MacosSource {
    fn snapshot(&self, variant: ThemeVariant) -> SystemTheme {
        let workspace = NSWorkspace::sharedWorkspace();

        let accessibility = AccessibilityPreferences {
            high_contrast: workspace.accessibilityDisplayShouldIncreaseContrast(),
            reduce_motion: workspace.accessibilityDisplayShouldReduceMotion(),
            reduce_transparency: workspace.accessibilityDisplayShouldReduceTransparency(),
        };

        let palette = self.snapshot_in_appearance(variant);

        SystemTheme {
            variant,
            accent: Self::color_to_hsla(&NSColor::controlAccentColor()),
            palette,
            control_radius: Some(gpui::px(CONTROL_RADIUS_PTS)),
            accessibility,
            source: SourceKind::Macos,
        }
    }

    /// Fires on accent and appearance changes (System Settings > Appearance)
    /// and re-runs the resolve pipeline through `async_cx`.
    fn install_watchers(&mut self, async_cx: gpui::AsyncApp) {
        let center = NSDistributedNotificationCenter::defaultCenter();
        let queue = NSOperationQueue::mainQueue();

        for name in [
            "AppleColorPreferencesChangedNotification",
            "AppleInterfaceThemeChangedNotification",
        ] {
            let async_cx = async_cx.clone();
            let block = block2::RcBlock::new(move |_notification: NonNull<NSNotification>| {
                async_cx.update(crate::reapply);
            });
            let name = NSNotificationName::from_str(name);
            // SAFETY: the observer token is retained for the source's lifetime,
            // the block is sendable (AsyncApp is Clone + 'static)
            // and the main queue runs it outside any App borrow.
            let observer = unsafe {
                center.addObserverForName_object_queue_usingBlock(
                    Some(&name),
                    None,
                    Some(&queue),
                    &block,
                )
            };
            self._observers.push(observer);
        }
    }

    fn label(&self) -> &'static str {
        SourceKind::Macos.label()
    }
}