//! This module implements forwarding methods for standard `NSApplicationDelegate` calls. It also
//! creates a custom `NSApplication` subclass that currently does nothing; this is meant as a hook
//! for potential future use.

use std::unreachable;
use std::sync::Once;

use cocoa::base::{id, nil, BOOL, YES, NO};
use cocoa::foundation::{NSUInteger};

use objc::{class, msg_send, sel, sel_impl};
use objc::declare::ClassDecl;
use objc::runtime::{Class, Object, Sel};

use url::Url;

use crate::app::traits::AppController;
use crate::constants::APP_PTR;
use crate::error::AppKitError;
use crate::printing::PrintSettings;
use crate::utils::str_from;

/// A handy method for grabbing our `AppController` from the pointer.
fn app<T: AppController>(this: &Object) -> &T {
    unsafe {
        let app_ptr: usize = *this.get_ivar(APP_PTR);
        let app = app_ptr as *const T;
        &*app
    }
}

/// Fires when the Application Delegate receives a `applicationWillFinishLaunching` notification.
extern fn will_finish_launching<T: AppController>(this: &Object, _: Sel, _: id) {
    app::<T>(this).will_finish_launching();
}

/// Fires when the Application Delegate receives a `applicationDidFinishLaunching` notification.
extern fn did_finish_launching<T: AppController>(this: &Object, _: Sel, _: id) {
    app::<T>(this).did_finish_launching();
}

/// Fires when the Application Delegate receives a `applicationWillBecomeActive` notification.
extern fn will_become_active<T: AppController>(this: &Object, _: Sel, _: id) {
    app::<T>(this).will_become_active();
}

/// Fires when the Application Delegate receives a `applicationDidBecomeActive` notification.
extern fn did_become_active<T: AppController>(this: &Object, _: Sel, _: id) {
    app::<T>(this).did_become_active();
}

/// Fires when the Application Delegate receives a `applicationWillResignActive` notification.
extern fn will_resign_active<T: AppController>(this: &Object, _: Sel, _: id) {
    app::<T>(this).will_resign_active();
}

/// Fires when the Application Delegate receives a `applicationDidResignActive` notification.
extern fn did_resign_active<T: AppController>(this: &Object, _: Sel, _: id) {
    app::<T>(this).did_resign_active();
}

/// Fires when the Application Delegate receives a 'applicationShouldTerminate:` notification.
extern fn should_terminate<T: AppController>(this: &Object, _: Sel, _: id) -> NSUInteger {
    app::<T>(this).should_terminate().into()
}

/// Fires when the Application Delegate receives a `applicationWillTerminate:` notification.
extern fn will_terminate<T: AppController>(this: &Object, _: Sel, _: id) {
    app::<T>(this).will_terminate();
}

/// Fires when the Application Delegate receives a `applicationWillHide:` notification.
extern fn will_hide<T: AppController>(this: &Object, _: Sel, _: id) {
    app::<T>(this).will_hide();
}

/// Fires when the Application Delegate receives a `applicationDidHide:` notification.
extern fn did_hide<T: AppController>(this: &Object, _: Sel, _: id) {
    app::<T>(this).did_hide();
}

/// Fires when the Application Delegate receives a `applicationWillUnhide:` notification.
extern fn will_unhide<T: AppController>(this: &Object, _: Sel, _: id) {
    app::<T>(this).will_unhide();
}

/// Fires when the Application Delegate receives a `applicationDidUnhide:` notification.
extern fn did_unhide<T: AppController>(this: &Object, _: Sel, _: id) {
    app::<T>(this).did_unhide();
}

/// Fires when the Application Delegate receives a `applicationWillUpdate:` notification.
extern fn will_update<T: AppController>(this: &Object, _: Sel, _: id) {
    app::<T>(this).will_update();
}

/// Fires when the Application Delegate receives a `applicationDidUpdate:` notification.
extern fn did_update<T: AppController>(this: &Object, _: Sel, _: id) {
    app::<T>(this).did_update();
}

/// Fires when the Application Delegate receives a
/// `applicationShouldHandleReopen:hasVisibleWindows:` notification.
extern fn should_handle_reopen<T: AppController>(this: &Object, _: Sel, _: id, has_visible_windows: BOOL) -> BOOL {
    match app::<T>(this).should_handle_reopen(match has_visible_windows {
        YES => true,
        NO => false,
        _ => { unreachable!(); },
    }) {
        true => YES,
        false => NO
    }
}

/// Fires when the application delegate receives a `applicationDockMenu:` request.
extern fn dock_menu<T: AppController>(_this: &Object, _: Sel, _: id) -> id {
    nil
}

/// Fires when the application delegate receives a `application:willPresentError:` notification.
extern fn will_present_error<T: AppController>(this: &Object, _: Sel, _: id, error: id) -> id {
    let error = AppKitError::new(error);
    app::<T>(this).will_present_error(*error).into_nserror()
}

/// Fires when the application receives a `applicationDidChangeScreenParameters:` notification.
extern fn did_change_screen_parameters<T: AppController>(this: &Object, _: Sel, _: id) {
    app::<T>(this).did_change_screen_parameters();
}

/// Fires when the application receives a `application:willContinueUserActivityWithType:`
/// notification.
extern fn will_continue_user_activity_with_type<T: AppController>(_this: &Object, _: Sel, _: id, activity_type: id) -> BOOL {
    let activity = str_from(activity_type);
    NO

    /*match app::<T>(this).will_continue_user_activity_with_type(activity) {
        true => YES,
        false => NO
    }*/
}

/// Fires when the application receives a `application:continueUserActivity:restorationHandler:` notification.
extern fn continue_user_activity<T: AppController>(_this: &Object, _: Sel, _: id, _: id, _: id) -> BOOL {
    NO
}

/// Fires when the application receives a
/// `application:didFailToContinueUserActivityWithType:error:` message.
extern fn failed_to_continue_user_activity<T: AppController>(_this: &Object, _: Sel, _: id, activity_type: id, error: id) {

}

/// Fires when the application receives a `application:didUpdateUserActivity:` message.
extern fn did_update_user_activity<T: AppController>(_this: &Object, _: Sel, _: id, _: id) {

}

/// Fires when the application receives a `application:didRegisterForRemoteNotificationsWithDeviceToken:` message.
extern fn registered_for_remote_notifications<T: AppController>(_this: &Object, _: Sel, _: id, _: id) {

}

/// Fires when the application receives a `application:didFailToRegisterForRemoteNotificationsWithError:` message.
extern fn failed_to_register_for_remote_notifications<T: AppController>(_this: &Object, _: Sel, _: id, _: id) {

}

/// Fires when the application receives a `application:didReceiveRemoteNotification:` message.
extern fn did_receive_remote_notification<T: AppController>(_this: &Object, _: Sel, _: id, _: id) {

}

/// Fires when the application receives a `application:userDidAcceptCloudKitShareWithMetadata:`
/// message.
extern fn accepted_cloudkit_share<T: AppController>(_this: &Object, _: Sel, _: id, _: id) {

}

/// Fires when the application receives an `application:openURLs` message.
extern fn open_urls<T: AppController>(this: &Object, _: Sel, _: id, file_urls: id) {
    app::<T>(this).open_urls(unsafe {
        let count: usize = msg_send![file_urls, count];
        let mut urls: Vec<Url> = Vec::with_capacity(count);

        let mut index = 0;
        loop {
            let url: id = msg_send![file_urls, objectAtIndex:index];
            let absolute_string: id = msg_send![url, absoluteString];
            let uri = str_from(absolute_string);

            if let Ok(u) = Url::parse(uri) {
                urls.push(u);
            }
            
            index += 1;
            if index == count { break; }
        }

        urls
    });
}

/// Fires when the application receives an `application:openFileWithoutUI:` message.
extern fn open_file_without_ui<T: AppController>(this: &Object, _: Sel, _: id, file: id) -> BOOL {
    let filename = str_from(file);

    match app::<T>(this).open_file_without_ui(filename) {
        true => YES,
        false => NO
    }
}

/// Fired when the application receives an `applicationShouldOpenUntitledFile:` message.
extern fn should_open_untitled_file<T: AppController>(this: &Object, _: Sel, _: id) -> BOOL {
    match app::<T>(this).should_open_untitled_file() {
        true => YES,
        false => NO
    }
}

/// Fired when the application receives an `applicationOpenUntitledFile:` message.
extern fn open_untitled_file<T: AppController>(this: &Object, _: Sel, _: id) -> BOOL {
    match app::<T>(this).open_untitled_file() {
        true => YES,
        false => NO
    }
}

/// Fired when the application receives an `application:openTempFile:` message.
extern fn open_temp_file<T: AppController>(this: &Object, _: Sel, _: id, filename: id) -> BOOL {
    let filename = str_from(filename);

    match app::<T>(this).open_temp_file(filename) {
        true => YES,
        false => NO
    }
}

/// Fired when the application receives an `application:printFile:` message.
extern fn print_file<T: AppController>(this: &Object, _: Sel, _: id, file: id) -> BOOL {
    let filename = str_from(file);

    match app::<T>(this).print_file(filename) {
        true => YES,
        false => NO
    }
}

/// Fired when the application receives an `application:printFiles:withSettings:showPrintPanels:`
/// message.
extern fn print_files<T: AppController>(this: &Object, _: Sel, _: id, files: id, settings: id, show_print_panels: BOOL) -> NSUInteger {
    app::<T>(this).print_files(vec![], PrintSettings::default(), match show_print_panels {
        YES => true,
        NO => false,
        _ => { unreachable!(); }
    }).into()
}

/// Called when the application receives an `application:delegateHandlesKey:` message.
/// Note: this may not fire in sandboxed applications. Apple's documentation is unclear on the
/// matter.
extern fn delegate_handles_key<T: AppController>(this: &Object, _: Sel, _: id, key: id) -> BOOL {
    let key = str_from(key);

    match app::<T>(this).delegate_handles_key(key) {
        true => YES,
        false => NO
    }
}

/// Registers an `NSObject` application delegate, and configures it for the various callbacks and
/// pointers we need to have.
pub(crate) fn register_app_controller_class<T: AppController>() -> *const Class {
    static mut DELEGATE_CLASS: *const Class = 0 as *const Class;
    static INIT: Once = Once::new();

    INIT.call_once(|| unsafe {
        let superclass = class!(NSObject);
        let mut decl = ClassDecl::new("RSTAppController", superclass).unwrap();

        decl.add_ivar::<usize>(APP_PTR);

        // Launching Applications
        decl.add_method(sel!(applicationWillFinishLaunching:), will_finish_launching::<T> as extern fn(&Object, _, _));
        decl.add_method(sel!(applicationDidFinishLaunching:), did_finish_launching::<T> as extern fn(&Object, _, _));
        
        // Managing Active Status
        decl.add_method(sel!(applicationWillBecomeActive:), will_become_active::<T> as extern fn(&Object, _, _));
        decl.add_method(sel!(applicationDidBecomeActive:), did_become_active::<T> as extern fn(&Object, _, _));
        decl.add_method(sel!(applicationWillResignActive:), will_resign_active::<T> as extern fn(&Object, _, _));
        decl.add_method(sel!(applicationDidResignActive:), did_resign_active::<T> as extern fn(&Object, _, _));

        // Terminating Applications
        decl.add_method(sel!(applicationShouldTerminate:), should_terminate::<T> as extern fn(&Object, _, _) -> NSUInteger);
        decl.add_method(sel!(applicationWillTerminate:), will_terminate::<T> as extern fn(&Object, _, _));

        // Hiding Applications
        decl.add_method(sel!(applicationWillHide:), will_hide::<T> as extern fn(&Object, _, _));
        decl.add_method(sel!(applicationDidHide:), did_hide::<T> as extern fn(&Object, _, _));
        decl.add_method(sel!(applicationWillUnhide:), will_unhide::<T> as extern fn(&Object, _, _));
        decl.add_method(sel!(applicationDidUnhide:), did_unhide::<T> as extern fn(&Object, _, _));

        // Managing Windows
        decl.add_method(sel!(applicationWillUpdate:), will_update::<T> as extern fn(&Object, _, _));
        decl.add_method(sel!(applicationDidUpdate:), did_update::<T> as extern fn(&Object, _, _));
        decl.add_method(sel!(applicationShouldHandleReopen:hasVisibleWindows:), should_handle_reopen::<T> as extern fn(&Object, _, _, BOOL) -> BOOL);

        // Dock Menu
        decl.add_method(sel!(applicationDockMenu:), dock_menu::<T> as extern fn(&Object, _, _) -> id);

        // Displaying Errors
        decl.add_method(sel!(application:willPresentError:), will_present_error::<T> as extern fn(&Object, _, _, id) -> id);

        // Managing the Screen
        decl.add_method(sel!(applicationDidChangeScreenParameters:), did_change_screen_parameters::<T> as extern fn(&Object, _, _));

        // User Activities
        decl.add_method(sel!(application:willContinueUserActivityWithType:), will_continue_user_activity_with_type::<T> as extern fn(&Object, _, _, id) -> BOOL);
        decl.add_method(sel!(application:continueUserActivity:restorationHandler:), continue_user_activity::<T> as extern fn(&Object, _, _, id, id) -> BOOL);
        decl.add_method(sel!(application:didFailToContinueUserActivityWithType:error:), failed_to_continue_user_activity::<T> as extern fn(&Object, _, _, id, id));
        decl.add_method(sel!(application:didUpdateUserActivity:), did_update_user_activity::<T> as extern fn(&Object, _, _, id));

        // Handling push notifications
        decl.add_method(sel!(application:didRegisterForRemoteNotificationsWithDeviceToken:), registered_for_remote_notifications::<T> as extern fn(&Object, _, _, id));
        decl.add_method(sel!(application:didFailToRegisterForRemoteNotificationsWithError:), failed_to_register_for_remote_notifications::<T> as extern fn(&Object, _, _, id));
        decl.add_method(sel!(application:didReceiveRemoteNotification:), did_receive_remote_notification::<T> as extern fn(&Object, _, _, id));

        // CloudKit
        decl.add_method(sel!(application:userDidAcceptCloudKitShareWithMetadata:), accepted_cloudkit_share::<T> as extern fn(&Object, _, _, id));

        // Opening Files
        decl.add_method(sel!(application:openURLs:), open_urls::<T> as extern fn(&Object, _, _, id));
        decl.add_method(sel!(application:openFileWithoutUI:), open_file_without_ui::<T> as extern fn(&Object, _, _, id) -> BOOL);
        decl.add_method(sel!(applicationShouldOpenUntitledFile:), should_open_untitled_file::<T> as extern fn(&Object, _, _) -> BOOL);
        decl.add_method(sel!(applicationOpenUntitledFile:), open_untitled_file::<T> as extern fn(&Object, _, _) -> BOOL);
        decl.add_method(sel!(application:openTempFile:), open_temp_file::<T> as extern fn(&Object, _, _, id) -> BOOL);

        // Printing
        decl.add_method(sel!(application:printFile:), print_file::<T> as extern fn(&Object, _, _, id) -> BOOL);
        decl.add_method(sel!(application:printFiles:withSettings:showPrintPanels:), print_files::<T> as extern fn(&Object, _, id, id, id, BOOL) -> NSUInteger);

        // @TODO: Restoring Application State
        // Depends on NSCoder support, which is... welp.

        // Scripting
        decl.add_method(sel!(application:delegateHandlesKey:), delegate_handles_key::<T> as extern fn(&Object, _, _, id) -> BOOL);

        DELEGATE_CLASS = decl.register();
    });

    unsafe {
        DELEGATE_CLASS
    }
}

/// Used for injecting a custom NSApplication. Currently does nothing.
pub(crate) fn register_app_class() -> *const Class {
    static mut APP_CLASS: *const Class = 0 as *const Class;
    static INIT: Once = Once::new();

    INIT.call_once(|| unsafe {
        let superclass = class!(NSApplication);
        let decl = ClassDecl::new("RSTApplication", superclass).unwrap();
        APP_CLASS = decl.register();
    });

    unsafe {
        APP_CLASS
    }
}