const std = @import("std");
const assert = std.debug.assert;
const Allocator = std.mem.Allocator;
const builtin = @import("builtin");
const adw = @import("adw");
const gio = @import("gio");
const glib = @import("glib");
const gobject = @import("gobject");
const gtk = @import("gtk");

const build_config = @import("../../../build_config.zig");
const apprt = @import("../../../apprt.zig");
const cgroup = @import("../cgroup.zig");
const CoreApp = @import("../../../App.zig");
const configpkg = @import("../../../config.zig");
const internal_os = @import("../../../os/main.zig");
const xev = @import("../../../global.zig").xev;
const Config = configpkg.Config;

const adw_version = @import("../adw_version.zig");
const gtk_version = @import("../gtk_version.zig");
const GhosttyWindow = @import("window.zig").GhosttyWindow;

const log = std.log.scoped(.gtk_ghostty_application);

/// The primary entrypoint for the Ghostty GTK application.
///
/// This requires a `ghostty.App` and `ghostty.Config` and takes
/// care of the rest. Call `run` to run the application to completion.
pub const GhosttyApplication = extern struct {
    /// This type creates a new GObject class. Since the Application is
    /// the primary entrypoint I'm going to use this as a place to document
    /// how this all works and where you can find resources for it, but
    /// this applies to any other GObject class within this apprt.
    ///
    /// The various fields (parent_instance) and constants (Parent,
    /// getGObjectType, etc.) are mandatory "interfaces" for zig-gobject
    /// to create a GObject class.
    ///
    /// I found these to be the best resources:
    ///
    ///   * https://github.com/ianprime0509/zig-gobject/blob/d7f1edaf50193d49b56c60568dfaa9f23195565b/extensions/gobject2.zig
    ///   * https://github.com/ianprime0509/zig-gobject/blob/d7f1edaf50193d49b56c60568dfaa9f23195565b/example/src/custom_class.zig
    ///
    const Self = @This();

    parent_instance: Parent,
    pub const Parent = adw.Application;
    pub const getGObjectType = gobject.ext.defineClass(Self, .{
        .classInit = &Class.init,
        .parent_class = &Class.parent,
        .private = .{ .Type = Private, .offset = &Private.offset },
    });

    const Private = struct {
        /// The libghostty App instance.
        core_app: *CoreApp,

        /// The configuration for the application.
        config: *Config,

        /// The base path of the transient cgroup used to put all surfaces
        /// into their own cgroup. This is only set if cgroups are enabled
        /// and initialization was successful.
        transient_cgroup_base: ?[]const u8 = null,

        /// This is set to false internally when the event loop
        /// should exit and the application should quit. This must
        /// only be set by the main loop thread.
        running: bool = false,

        var offset: c_int = 0;
    };

    /// Creates a new GhosttyApplication instance.
    ///
    /// This does a lot more work than a typical class instantiation,
    /// because we expect that this is the main program entrypoint.
    ///
    /// The only failure mode of initializing the application is early OOM.
    /// Early OOM can't be recovered from. Every other error is mapped to
    /// some degraded state where we can at least show a window with an error.
    pub fn new(core_app: *CoreApp) Allocator.Error!*Self {
        const alloc = core_app.alloc;

        // Log our GTK versions
        gtk_version.logVersion();
        adw_version.logVersion();

        // Set gettext global domain to be our app so that our unqualified
        // translations map to our translations.
        internal_os.i18n.initGlobalDomain() catch |err| {
            // Failures shuldn't stop application startup. Our app may
            // not translate correctly but it should still work. In the
            // future we may want to add this to the GUI to show.
            log.warn("i18n initialization failed error={}", .{err});
        };

        // Load our configuration.
        const config: *Config = try alloc.create(Config);
        errdefer alloc.destroy(config);
        config.* = Config.load(alloc) catch |err| err: {
            // If we fail to load the configuration, then we should log
            // the error in the diagnostics so it can be shown to the user.
            // We can still load a default which only fails for OOM, allowing
            // us to startup.
            var default = try Config.default(alloc);
            errdefer default.deinit();
            const config_arena = default._arena.?.allocator();
            try default._diagnostics.append(config_arena, .{
                .message = try std.fmt.allocPrintZ(
                    config_arena,
                    "error loading user configuration: {}",
                    .{err},
                ),
            });

            break :err default;
        };
        errdefer config.deinit();

        // Setup our GTK init env vars
        setGtkEnv(config) catch |err| switch (err) {
            error.NoSpaceLeft => {
                // If we fail to set GTK environment variables then we still
                // try to start the application...
                log.warn(
                    "error setting GTK environment variables err={}",
                    .{err},
                );
            },
        };
        adw.init();

        const single_instance = switch (config.@"gtk-single-instance") {
            .true => true,
            .false => false,
            .desktop => switch (config.@"launched-from".?) {
                .desktop, .systemd, .dbus => true,
                .cli => false,
            },
        };

        // Setup the flags for our application.
        const app_flags: gio.ApplicationFlags = app_flags: {
            var flags: gio.ApplicationFlags = .flags_default_flags;
            if (!single_instance) flags.non_unique = true;
            break :app_flags flags;
        };

        // Our app ID determines uniqueness and maps to our desktop file.
        // We append "-debug" to the ID if we're in debug mode so that we
        // can develop Ghostty in Ghostty.
        const app_id: [:0]const u8 = app_id: {
            if (config.class) |class| {
                if (gio.Application.idIsValid(class) != 0) {
                    break :app_id class;
                } else {
                    log.warn("invalid 'class' in config, ignoring", .{});
                }
            }

            const default_id = comptime build_config.bundle_id;
            break :app_id if (builtin.mode == .Debug) default_id ++ "-debug" else default_id;
        };

        // Create our GTK Application which encapsulates our process.
        log.debug("creating GTK application id={s} single-instance={}", .{
            app_id,
            single_instance,
        });

        // Initialize the app.
        const self = gobject.ext.newInstance(Self, .{
            .application_id = app_id.ptr,
            .flags = app_flags,

            // Force the resource path to a known value so it doesn't depend
            // on the app id (which changes between debug/release and can be
            // user-configured) and force it to load in compiled resources.
            .resource_base_path = "/com/mitchellh/ghostty",
        });

        // Setup our private state. More setup is done in the init
        // callback that GObject calls, but we can't pass this data through
        // to there (and we don't need it there directly) so this is here.
        const priv = self.private();
        priv.core_app = core_app;
        priv.config = config;

        return self;
    }

    /// Force deinitialize the application.
    ///
    /// Normally in a GObject lifecycle, this would be called by the
    /// finalizer. But applications are never fully unreferenced so this
    /// ensures that our memory is cleaned up properly.
    pub fn deinit(self: *Self) void {
        const alloc = self.allocator();
        const priv = self.private();
        priv.config.deinit();
        alloc.destroy(priv.config);
        if (priv.transient_cgroup_base) |base| alloc.free(base);
    }

    /// Run the application. This is a replacement for `gio.Application.run`
    /// because we want more tight control over our event loop so we can
    /// integrate it with libghostty.
    pub fn run(self: *Self, rt_app: *apprt.gtk_ng.App) !void {
        // Based on the actual `gio.Application.run` implementation:
        // https://github.com/GNOME/glib/blob/a8e8b742e7926e33eb635a8edceac74cf239d6ed/gio/gapplication.c#L2533

        // Acquire the default context for the application
        const ctx = glib.MainContext.default();
        if (glib.MainContext.acquire(ctx) == 0) return error.ContextAcquireFailed;

        // The final cleanup that is always required at the end of running.
        defer {
            // Sync any remaining settings
            gio.Settings.sync();

            // Clear out the event loop, don't block.
            while (glib.MainContext.iteration(ctx, 0) != 0) {}

            // Release the context so something else can use it.
            defer glib.MainContext.release(ctx);
        }

        // Register the application
        var err_: ?*glib.Error = null;
        if (self.as(gio.Application).register(
            null,
            &err_,
        ) == 0) {
            if (err_) |err| {
                defer err.free();
                log.warn(
                    "error registering application: {s}",
                    .{err.f_message orelse "(unknown)"},
                );
            }

            return error.ApplicationRegisterFailed;
        }
        assert(err_ == null);

        // This just calls the `activate` signal but its part of the normal startup
        // routine so we just call it, but only if the config allows it (this allows
        // for launching Ghostty in the "background" without immediately opening
        // a window). An initial window will not be immediately created if we were
        // launched by D-Bus activation or systemd.  D-Bus activation will send it's
        // own `activate` or `new-window` signal later.
        //
        // https://gitlab.gnome.org/GNOME/glib/-/blob/bd2ccc2f69ecfd78ca3f34ab59e42e2b462bad65/gio/gapplication.c#L2302
        const priv = self.private();
        const config = priv.config;
        if (config.@"initial-window") switch (config.@"launched-from".?) {
            .desktop, .cli => self.as(gio.Application).activate(),
            .dbus, .systemd => {},
        };

        // If we are NOT the primary instance, then we never want to run.
        // This means that another instance of the GTK app is running and
        // our "activate" call above will open a window.
        if (self.as(gio.Application).getIsRemote() != 0) {
            log.debug(
                "application is remote, exiting run loop after activation",
                .{},
            );
            return;
        }

        log.debug("entering runloop", .{});
        defer log.debug("exiting runloop", .{});
        priv.running = true;
        while (priv.running) {
            _ = glib.MainContext.iteration(ctx, 1);

            // Tick the core Ghostty terminal app
            try priv.core_app.tick(rt_app);

            // Check if we must quit based on the current state.
            const must_quit = q: {
                // If we are configured to always stay running, don't quit.
                if (!config.@"quit-after-last-window-closed") break :q false;

                // If the quit timer has expired, quit.
                // if (self.quit_timer == .expired) break :q true;

                // There's no quit timer running, or it hasn't expired, don't quit.
                break :q false;
            };

            if (must_quit) {
                //self.quit();
                priv.running = false;
            }
        }
    }

    pub fn as(app: *Self, comptime T: type) *T {
        return gobject.ext.as(T, app);
    }

    pub fn unref(self: *Self) void {
        gobject.Object.unref(self.as(gobject.Object));
    }

    fn private(self: *GhosttyApplication) *Private {
        return gobject.ext.impl_helpers.getPrivate(
            self,
            Private,
            Private.offset,
        );
    }

    fn startup(self: *GhosttyApplication) callconv(.C) void {
        log.debug("startup", .{});

        // Setup our event loop
        self.startupXev();

        // Setup our style manager (light/dark mode)
        self.startupStyleManager();

        // Setup our cgroup for the application.
        self.startupCgroup() catch {
            log.warn("TODO", .{});
        };

        gio.Application.virtual_methods.startup.call(
            Class.parent,
            self.as(Parent),
        );
    }

    /// Configure libxev to use a specific backend.
    ///
    /// This must be called before any other xev APIs are used.
    fn startupXev(self: *GhosttyApplication) void {
        const priv = self.private();
        const config = priv.config;

        // If our backend is auto then we have no setup to do.
        if (config.@"async-backend" == .auto) return;

        // Setup our event loop backend to the preferred method
        const result: bool = switch (config.@"async-backend") {
            .auto => unreachable,
            .epoll => if (comptime xev.dynamic) xev.prefer(.epoll) else false,
            .io_uring => if (comptime xev.dynamic) xev.prefer(.io_uring) else false,
        };

        if (result) {
            log.info(
                "libxev manual backend={s}",
                .{@tagName(xev.backend)},
            );
        } else {
            log.warn(
                "libxev manual backend failed, using default={s}",
                .{@tagName(xev.backend)},
            );
        }
    }

    /// Setup the style manager on startup. The primary task here is to
    /// setup our initial light/dark mode based on the configuration and
    /// setup listeners for changes to the style manager.
    fn startupStyleManager(self: *GhosttyApplication) void {
        const priv = self.private();
        const config = priv.config;

        // Setup our initial light/dark
        const style = self.as(adw.Application).getStyleManager();
        style.setColorScheme(switch (config.@"window-theme") {
            .auto, .ghostty => auto: {
                const lum = config.background.toTerminalRGB().perceivedLuminance();
                break :auto if (lum > 0.5)
                    .prefer_light
                else
                    .prefer_dark;
            },
            .system => .prefer_light,
            .dark => .force_dark,
            .light => .force_light,
        });

        // Setup color change notifications
        _ = gobject.Object.signals.notify.connect(
            style,
            *GhosttyApplication,
            handleStyleManagerDark,
            self,
            .{ .detail = "dark" },
        );
    }

    const CgroupError = error{
        DbusConnectionFailed,
        CgroupInitFailed,
    };

    /// Setup our cgroup for the application, if enabled.
    ///
    /// The setup for cgroups involves creating the cgroup for our
    /// application, moving ourselves into it, and storing the base path
    /// so that created surfaces can also have their own cgroups.
    fn startupCgroup(self: *GhosttyApplication) CgroupError!void {
        const priv = self.private();
        const config = priv.config;

        // If cgroup isolation isn't enabled then we don't do this.
        if (!switch (config.@"linux-cgroup") {
            .never => false,
            .always => true,
            .@"single-instance" => single: {
                const flags = self.as(gio.Application).getFlags();
                break :single !flags.non_unique;
            },
        }) {
            log.info(
                "cgroup isolation disabled via config={}",
                .{config.@"linux-cgroup"},
            );
            return;
        }

        // We need a dbus connection to do anything else
        const dbus = self.as(gio.Application).getDbusConnection() orelse {
            if (config.@"linux-cgroup-hard-fail") {
                log.err("dbus connection required for cgroup isolation, exiting", .{});
                return error.DbusConnectionFailed;
            }

            return;
        };

        const alloc = priv.core_app.alloc;
        const path = cgroup.init(alloc, dbus, .{
            .memory_high = config.@"linux-cgroup-memory-limit",
            .pids_max = config.@"linux-cgroup-processes-limit",
        }) catch |err| {
            // If we can't initialize cgroups then that's okay. We
            // want to continue to run so we just won't isolate surfaces.
            // NOTE(mitchellh): do we want a config to force it?
            log.warn(
                "failed to initialize cgroups, terminals will not be isolated err={}",
                .{err},
            );

            // If we have hard fail enabled then we exit now.
            if (config.@"linux-cgroup-hard-fail") {
                log.err("linux-cgroup-hard-fail enabled, exiting", .{});
                return error.CgroupInitFailed;
            }

            return;
        };

        log.info("cgroup isolation enabled base={s}", .{path});
        priv.transient_cgroup_base = path;
    }

    fn activate(self: *GhosttyApplication) callconv(.C) void {
        log.debug("activate", .{});

        // Call the parent activate method.
        gio.Application.virtual_methods.activate.call(
            Class.parent,
            self.as(Parent),
        );

        const win = GhosttyWindow.new(self);
        gtk.Window.present(win.as(gtk.Window));
    }

    fn finalize(self: *GhosttyApplication) callconv(.C) void {
        self.deinit();
        gobject.Object.virtual_methods.finalize.call(
            Class.parent,
            self.as(Parent),
        );
    }

    fn handleStyleManagerDark(
        style: *adw.StyleManager,
        _: *gobject.ParamSpec,
        self: *GhosttyApplication,
    ) callconv(.c) void {
        _ = self;

        const color_scheme: apprt.ColorScheme = if (style.getDark() == 0)
            .light
        else
            .dark;

        log.debug("style manager changed scheme={}", .{color_scheme});
    }

    fn allocator(self: *GhosttyApplication) std.mem.Allocator {
        return self.private().core_app.alloc;
    }

    pub const Class = extern struct {
        parent_class: Parent.Class,
        var parent: *Parent.Class = undefined;
        pub const Instance = Self;

        fn init(class: *Class) callconv(.C) void {
            // Register our compiled resources exactly once.
            {
                const c = @cImport({
                    // generated header files
                    @cInclude("ghostty_resources.h");
                });
                if (c.ghostty_get_resource()) |ptr| {
                    gio.resourcesRegister(@ptrCast(@alignCast(ptr)));
                } else {
                    // If we fail to load resources then things will
                    // probably look really bad but it shouldn't stop our
                    // app from loading.
                    log.warn("unable to load resources", .{});
                }
            }

            // Virtual methods
            gio.Application.virtual_methods.activate.implement(class, &activate);
            gio.Application.virtual_methods.startup.implement(class, &startup);
            gobject.Object.virtual_methods.finalize.implement(class, &finalize);
        }
    };
};

/// This sets various GTK-related environment variables as necessary
/// given the runtime environment or configuration.
///
/// This must be called BEFORE GTK initialization.
fn setGtkEnv(config: *const Config) error{NoSpaceLeft}!void {
    assert(gtk.isInitialized() == 0);

    var gdk_debug: struct {
        /// output OpenGL debug information
        opengl: bool = false,
        /// disable GLES, Ghostty can't use GLES
        @"gl-disable-gles": bool = false,
        // GTK's new renderer can cause blurry font when using fractional scaling.
        @"gl-no-fractional": bool = false,
        /// Disabling Vulkan can improve startup times by hundreds of
        /// milliseconds on some systems. We don't use Vulkan so we can just
        /// disable it.
        @"vulkan-disable": bool = false,
    } = .{
        .opengl = config.@"gtk-opengl-debug",
    };

    var gdk_disable: struct {
        @"gles-api": bool = false,
        /// current gtk implementation for color management is not good enough.
        /// see: https://bugs.kde.org/show_bug.cgi?id=495647
        /// gtk issue: https://gitlab.gnome.org/GNOME/gtk/-/issues/6864
        @"color-mgmt": bool = true,
        /// Disabling Vulkan can improve startup times by hundreds of
        /// milliseconds on some systems. We don't use Vulkan so we can just
        /// disable it.
        vulkan: bool = false,
    } = .{};

    environment: {
        if (gtk_version.runtimeAtLeast(4, 18, 0)) {
            gdk_disable.@"color-mgmt" = false;
        }

        if (gtk_version.runtimeAtLeast(4, 16, 0)) {
            // From gtk 4.16, GDK_DEBUG is split into GDK_DEBUG and GDK_DISABLE.
            // For the remainder of "why" see the 4.14 comment below.
            gdk_disable.@"gles-api" = true;
            gdk_disable.vulkan = true;
            break :environment;
        }
        if (gtk_version.runtimeAtLeast(4, 14, 0)) {
            // We need to export GDK_DEBUG to run on Wayland after GTK 4.14.
            // Older versions of GTK do not support these values so it is safe
            // to always set this. Forwards versions are uncertain so we'll have
            // to reassess...
            //
            // Upstream issue: https://gitlab.gnome.org/GNOME/gtk/-/issues/6589
            gdk_debug.@"gl-disable-gles" = true;
            gdk_debug.@"vulkan-disable" = true;

            if (gtk_version.runtimeUntil(4, 17, 5)) {
                // Removed at GTK v4.17.5
                gdk_debug.@"gl-no-fractional" = true;
            }
            break :environment;
        }

        // Versions prior to 4.14 are a bit of an unknown for Ghostty. It
        // is an environment that isn't tested well and we don't have a
        // good understanding of what we may need to do.
        gdk_debug.@"vulkan-disable" = true;
    }

    {
        var buf: [1024]u8 = undefined;
        var fmt = std.io.fixedBufferStream(&buf);
        const writer = fmt.writer();
        var first: bool = true;
        inline for (@typeInfo(@TypeOf(gdk_debug)).@"struct".fields) |field| {
            if (@field(gdk_debug, field.name)) {
                if (!first) try writer.writeAll(",");
                try writer.writeAll(field.name);
                first = false;
            }
        }
        try writer.writeByte(0);
        const value = fmt.getWritten();
        log.warn("setting GDK_DEBUG={s}", .{value[0 .. value.len - 1]});
        _ = internal_os.setenv("GDK_DEBUG", value[0 .. value.len - 1 :0]);
    }

    {
        var buf: [1024]u8 = undefined;
        var fmt = std.io.fixedBufferStream(&buf);
        const writer = fmt.writer();
        var first: bool = true;
        inline for (@typeInfo(@TypeOf(gdk_disable)).@"struct".fields) |field| {
            if (@field(gdk_disable, field.name)) {
                if (!first) try writer.writeAll(",");
                try writer.writeAll(field.name);
                first = false;
            }
        }
        try writer.writeByte(0);
        const value = fmt.getWritten();
        log.warn("setting GDK_DISABLE={s}", .{value[0 .. value.len - 1]});
        _ = internal_os.setenv("GDK_DISABLE", value[0 .. value.len - 1 :0]);
    }
}