// This file is part of river, a dynamic tiling wayland compositor.
//
// Copyright 2020 The River Developers
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, version 3.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program. If not, see <https://www.gnu.org/licenses/>.

const Self = @This();

const build_options = @import("build_options");
const std = @import("std");
const assert = std.debug.assert;
const math = std.math;
const os = std.os;
const wlr = @import("wlroots");
const wl = @import("wayland").server.wl;

const server = &@import("main.zig").server;
const util = @import("util.zig");

const Output = @import("Output.zig");
const Seat = @import("Seat.zig");
const ViewStack = @import("view_stack.zig").ViewStack;
const XdgToplevel = @import("XdgToplevel.zig");
const XwaylandView = if (build_options.xwayland) @import("XwaylandView.zig") else @import("VoidView.zig");

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

pub const Constraints = struct {
    min_width: u31,
    max_width: u31,
    min_height: u31,
    max_height: u31,
};

const Impl = union(enum) {
    xdg_toplevel: XdgToplevel,
    xwayland_view: XwaylandView,
};

const State = struct {
    /// The output-relative effective coordinates and effective dimensions of the view. The
    /// surface itself may have other dimensions which are stored in the
    /// surface_box member.
    box: wlr.Box = wlr.Box{ .x = 0, .y = 0, .width = 0, .height = 0 },

    /// The tags of the view, as a bitmask
    tags: u32,

    /// Number of seats currently focusing the view
    focus: u32 = 0,

    float: bool = false,
    fullscreen: bool = false,
    urgent: bool = false,
};

const SavedBuffer = struct {
    client_buffer: *wlr.ClientBuffer,
    /// x/y relative to the root surface in the surface tree.
    surface_box: wlr.Box,
    source_box: wlr.FBox,
    transform: wl.Output.Transform,
};

/// The implementation of this view
impl: Impl,

/// The output this view is currently associated with
output: *Output,

/// This is non-null exactly when the view is mapped
surface: ?*wlr.Surface = null,

/// This indicates that the view should be destroyed when the current
/// transaction completes. See View.destroy()
destroying: bool = false,

/// The double-buffered state of the view
current: State,
pending: State,

/// The serial sent with the currently pending configure event
pending_serial: ?u32 = null,

/// The currently commited geometry of the surface. The x/y may be negative if
/// for example the client has decided to draw CSD shadows a la GTK.
surface_box: wlr.Box = undefined,

/// The geometry the view's surface had when the transaction started and
/// buffers were saved.
saved_surface_box: wlr.Box = undefined,

/// These are what we render while a transaction is in progress
saved_buffers: std.ArrayListUnmanaged(SavedBuffer) = .{},

/// The floating dimensions the view, saved so that they can be restored if the
/// view returns to floating mode.
float_box: wlr.Box = undefined,

/// This state exists purely to allow for more intuitive behavior when
/// exiting fullscreen if there is no active layout.
post_fullscreen_box: wlr.Box = undefined,

draw_borders: bool = true,

/// This is created when the view is mapped and destroyed when unmapped
foreign_toplevel_handle: ?*wlr.ForeignToplevelHandleV1 = null,
foreign_activate: wl.Listener(*wlr.ForeignToplevelHandleV1.event.Activated) =
    wl.Listener(*wlr.ForeignToplevelHandleV1.event.Activated).init(handleForeignActivate),
foreign_fullscreen: wl.Listener(*wlr.ForeignToplevelHandleV1.event.Fullscreen) =
    wl.Listener(*wlr.ForeignToplevelHandleV1.event.Fullscreen).init(handleForeignFullscreen),
foreign_close: wl.Listener(*wlr.ForeignToplevelHandleV1) =
    wl.Listener(*wlr.ForeignToplevelHandleV1).init(handleForeignClose),

request_activate: wl.Listener(*wlr.XdgActivationV1.event.RequestActivate) =
    wl.Listener(*wlr.XdgActivationV1.event.RequestActivate).init(handleRequestActivate),

pub fn init(self: *Self, output: *Output, impl: Impl) void {
    const initial_tags = blk: {
        const tags = output.current.tags & server.config.spawn_tagmask;
        break :blk if (tags != 0) tags else output.current.tags;
    };

    self.* = .{
        .impl = impl,
        .output = output,
        .current = .{ .tags = initial_tags },
        .pending = .{ .tags = initial_tags },
    };
}

/// If saved buffers of the view are currently in use by a transaction,
/// mark this view for destruction when the transaction completes. Otherwise
/// destroy immediately.
pub fn destroy(self: *Self) void {
    assert(self.surface == null);
    self.destroying = true;

    // If there are still saved buffers, then this view needs to be kept
    // around until the current transaction completes. This function will be
    // called again in Root.commitTransaction()
    if (self.saved_buffers.items.len == 0) {
        self.saved_buffers.deinit(util.gpa);

        const node = @fieldParentPtr(ViewStack(Self).Node, "view", self);
        util.gpa.destroy(node);
    }
}

/// Handle changes to pending state and start a transaction to apply them
pub fn applyPending(self: *Self) void {
    if (self.current.float and !self.pending.float) {
        // If switching from float to non-float, save the dimensions.
        self.float_box = self.current.box;
    } else if (!self.current.float and self.pending.float) {
        // If switching from non-float to float, apply the saved float dimensions.
        self.pending.box = self.float_box;
    }

    if (!self.lastSetFullscreenState() and self.pending.fullscreen) {
        // If switching to fullscreen, set the dimensions to the full area of the output
        self.setFullscreen(true);
        self.post_fullscreen_box = self.current.box;

        self.pending.box = .{
            .x = 0,
            .y = 0,
            .width = undefined,
            .height = undefined,
        };
        self.output.wlr_output.effectiveResolution(&self.pending.box.width, &self.pending.box.height);
    } else if (self.lastSetFullscreenState() and !self.pending.fullscreen) {
        self.setFullscreen(false);
        self.pending.box = self.post_fullscreen_box;
    }

    // We always need to arrange the output, as there could already be a
    // transaction in progress. If we were able to check against the state
    // that was pending when that transaction was started, we could in some
    // cases avoid the arrangeViews() call here, but we don't store that
    // information and it's simpler to always arrange anyways.
    self.output.arrangeViews();

    server.root.startTransaction();
}

pub fn needsConfigure(self: Self) bool {
    return switch (self.impl) {
        .xdg_toplevel => |xdg_toplevel| xdg_toplevel.needsConfigure(),
        .xwayland_view => |xwayland_view| xwayland_view.needsConfigure(),
    };
}

pub fn configure(self: *Self) void {
    switch (self.impl) {
        .xdg_toplevel => |*xdg_toplevel| xdg_toplevel.configure(),
        .xwayland_view => |*xwayland_view| xwayland_view.configure(),
    }
}

fn lastSetFullscreenState(self: Self) bool {
    return switch (self.impl) {
        .xdg_toplevel => |xdg_toplevel| xdg_toplevel.lastSetFullscreenState(),
        .xwayland_view => |xwayland_view| xwayland_view.lastSetFullscreenState(),
    };
}

pub fn sendFrameDone(self: Self) void {
    var now: os.timespec = undefined;
    os.clock_gettime(os.CLOCK.MONOTONIC, &now) catch @panic("CLOCK_MONOTONIC not supported");
    self.surface.?.sendFrameDone(&now);
}

pub fn dropSavedBuffers(self: *Self) void {
    for (self.saved_buffers.items) |buffer| buffer.client_buffer.base.unlock();
    self.saved_buffers.items.len = 0;
}

pub fn saveBuffers(self: *Self) void {
    assert(self.saved_buffers.items.len == 0);
    self.saved_surface_box = self.surface_box;
    self.forEachSurface(*std.ArrayListUnmanaged(SavedBuffer), saveBuffersIterator, &self.saved_buffers);
}

fn saveBuffersIterator(
    surface: *wlr.Surface,
    surface_x: c_int,
    surface_y: c_int,
    saved_buffers: *std.ArrayListUnmanaged(SavedBuffer),
) callconv(.C) void {
    if (surface.buffer) |buffer| {
        var source_box: wlr.FBox = undefined;
        surface.getBufferSourceBox(&source_box);
        saved_buffers.append(util.gpa, .{
            .client_buffer = buffer,
            .surface_box = .{
                .x = surface_x,
                .y = surface_y,
                .width = surface.current.width,
                .height = surface.current.height,
            },
            .source_box = source_box,
            .transform = surface.current.transform,
        }) catch return;
        _ = buffer.base.lock();
    }
}

/// Move a view from one output to another, sending the required enter/leave
/// events.
pub fn sendToOutput(self: *Self, destination_output: *Output) void {
    const node = @fieldParentPtr(ViewStack(Self).Node, "view", self);

    self.output.views.remove(node);
    destination_output.views.attach(node, server.config.attach_mode);

    self.output.sendViewTags();
    destination_output.sendViewTags();

    if (self.pending.urgent) {
        self.output.sendUrgentTags();
        destination_output.sendUrgentTags();
    }

    // if the view is mapped send enter/leave events
    if (self.surface != null) {
        self.sendLeave(self.output);
        self.sendEnter(destination_output);

        // Must be present if surface is non-null indicating that the view
        // is mapped.
        self.foreign_toplevel_handle.?.outputLeave(self.output.wlr_output);
        self.foreign_toplevel_handle.?.outputEnter(destination_output.wlr_output);
    }

    self.output = destination_output;

    var output_width: i32 = undefined;
    var output_height: i32 = undefined;
    destination_output.wlr_output.effectiveResolution(&output_width, &output_height);

    if (self.pending.float) {
        // Adapt dimensions of view to new output. Only necessary when floating,
        // because for tiled views the output will be rearranged, taking care
        // of this.
        if (self.pending.fullscreen) self.pending.box = self.post_fullscreen_box;
        const border_width = if (self.draw_borders) server.config.border_width else 0;
        self.pending.box.width = math.min(self.pending.box.width, output_width - (2 * border_width));
        self.pending.box.height = math.min(self.pending.box.height, output_height - (2 * border_width));

        // Adjust position of view so that it is fully inside the target output.
        self.move(0, 0);
    }

    if (self.pending.fullscreen) {
        // If the view is floating, we need to set the post_fullscreen_box, as
        // that is still set for the previous output.
        if (self.pending.float) self.post_fullscreen_box = self.pending.box;

        self.pending.box = .{
            .x = 0,
            .y = 0,
            .width = output_width,
            .height = output_height,
        };
    }
}

fn sendEnter(self: *Self, output: *Output) void {
    self.forEachSurface(*wlr.Output, sendEnterIterator, output.wlr_output);
}

fn sendEnterIterator(surface: *wlr.Surface, _: c_int, _: c_int, wlr_output: *wlr.Output) callconv(.C) void {
    surface.sendEnter(wlr_output);
}

fn sendLeave(self: *Self, output: *Output) void {
    self.forEachSurface(*wlr.Output, sendLeaveIterator, output.wlr_output);
}

fn sendLeaveIterator(surface: *wlr.Surface, _: c_int, _: c_int, wlr_output: *wlr.Output) callconv(.C) void {
    surface.sendLeave(wlr_output);
}

pub fn close(self: Self) void {
    switch (self.impl) {
        .xdg_toplevel => |xdg_toplevel| xdg_toplevel.close(),
        .xwayland_view => |xwayland_view| xwayland_view.close(),
    }
}

pub fn setActivated(self: Self, activated: bool) void {
    if (self.foreign_toplevel_handle) |handle| handle.setActivated(activated);
    switch (self.impl) {
        .xdg_toplevel => |xdg_toplevel| xdg_toplevel.setActivated(activated),
        .xwayland_view => |xwayland_view| xwayland_view.setActivated(activated),
    }
}

fn setFullscreen(self: *Self, fullscreen: bool) void {
    if (self.foreign_toplevel_handle) |handle| handle.setFullscreen(fullscreen);
    switch (self.impl) {
        .xdg_toplevel => |xdg_toplevel| xdg_toplevel.setFullscreen(fullscreen),
        .xwayland_view => |*xwayland_view| xwayland_view.setFullscreen(fullscreen),
    }
}

pub fn setResizing(self: Self, resizing: bool) void {
    switch (self.impl) {
        .xdg_toplevel => |xdg_toplevel| xdg_toplevel.setResizing(resizing),
        .xwayland_view => {},
    }
}

/// Iterates over all surfaces, subsurfaces, and popups in the tree
pub inline fn forEachSurface(
    self: Self,
    comptime T: type,
    iterator: fn (surface: *wlr.Surface, sx: c_int, sy: c_int, data: T) callconv(.C) void,
    user_data: T,
) void {
    switch (self.impl) {
        .xdg_toplevel => |xdg_toplevel| {
            xdg_toplevel.xdg_toplevel.base.forEachSurface(T, iterator, user_data);
        },
        .xwayland_view => {
            assert(build_options.xwayland);
            self.surface.?.forEachSurface(T, iterator, user_data);
        },
    }
}

/// Return the surface at output coordinates ox, oy and set sx, sy to the
/// corresponding surface-relative coordinates, if there is a surface.
pub fn surfaceAt(self: Self, ox: f64, oy: f64, sx: *f64, sy: *f64) ?*wlr.Surface {
    return switch (self.impl) {
        .xdg_toplevel => |xdg_toplevel| xdg_toplevel.surfaceAt(ox, oy, sx, sy),
        .xwayland_view => |xwayland_view| xwayland_view.surfaceAt(ox, oy, sx, sy),
    };
}

/// Return the current title of the view if any.
pub fn getTitle(self: Self) ?[*:0]const u8 {
    return switch (self.impl) {
        .xdg_toplevel => |xdg_toplevel| xdg_toplevel.getTitle(),
        .xwayland_view => |xwayland_view| xwayland_view.getTitle(),
    };
}

/// Return the current app_id of the view if any.
pub fn getAppId(self: Self) ?[*:0]const u8 {
    return switch (self.impl) {
        .xdg_toplevel => |xdg_toplevel| xdg_toplevel.getAppId(),
        .xwayland_view => |xwayland_view| xwayland_view.getAppId(),
    };
}

/// Clamp the width/height of the pending state to the constraints of the view
pub fn applyConstraints(self: *Self) void {
    const constraints = self.getConstraints();
    const box = &self.pending.box;
    box.width = math.clamp(box.width, constraints.min_width, constraints.max_width);
    box.height = math.clamp(box.height, constraints.min_height, constraints.max_height);
}

/// Return bounds on the dimensions of the view
pub fn getConstraints(self: Self) Constraints {
    return switch (self.impl) {
        .xdg_toplevel => |xdg_toplevel| xdg_toplevel.getConstraints(),
        .xwayland_view => |xwayland_view| xwayland_view.getConstraints(),
    };
}

/// Modify the pending x/y of the view by the given deltas, clamping to the
/// bounds of the output.
pub fn move(self: *Self, delta_x: i32, delta_y: i32) void {
    const border_width = if (self.draw_borders) server.config.border_width else 0;
    var output_width: i32 = undefined;
    var output_height: i32 = undefined;
    self.output.wlr_output.effectiveResolution(&output_width, &output_height);

    const max_x = output_width - self.pending.box.width - border_width;
    self.pending.box.x += delta_x;
    self.pending.box.x = math.max(self.pending.box.x, border_width);
    self.pending.box.x = math.min(self.pending.box.x, max_x);
    self.pending.box.x = math.max(self.pending.box.x, 0);

    const max_y = output_height - self.pending.box.height - border_width;
    self.pending.box.y += delta_y;
    self.pending.box.y = math.max(self.pending.box.y, border_width);
    self.pending.box.y = math.min(self.pending.box.y, max_y);
    self.pending.box.y = math.max(self.pending.box.y, 0);
}

/// Find and return the view corresponding to a given surface, if any
pub fn fromWlrSurface(surface: *wlr.Surface) ?*Self {
    if (surface.isXdgSurface()) {
        const xdg_surface = wlr.XdgSurface.fromWlrSurface(surface) orelse return null;
        if (xdg_surface.role == .toplevel) {
            return @intToPtr(*Self, xdg_surface.data);
        }
    }
    if (build_options.xwayland and surface.isXWaylandSurface()) {
        const xwayland_surface = wlr.XwaylandSurface.fromWlrSurface(surface) orelse return null;
        return @intToPtr(?*Self, xwayland_surface.data);
    }
    if (surface.isSubsurface()) {
        if (wlr.Subsurface.fromWlrSurface(surface)) |ss| {
            if (ss.parent) |s| {
                return fromWlrSurface(s);
            }
        }
    }
    return null;
}

pub fn shouldTrackConfigure(self: Self) bool {
    // We don't give a damn about frame perfection for xwayland views
    if (build_options.xwayland and self.impl == .xwayland_view) return false;

    // There are exactly three cases in which we do not track configures
    // 1. the view was and remains floating
    // 2. the view is changing from float/layout to fullscreen
    // 3. the view is changing from fullscreen to float
    return !((self.pending.float and self.current.float) or
        (self.pending.fullscreen and !self.current.fullscreen) or
        (self.pending.float and !self.pending.fullscreen and self.current.fullscreen));
}

/// Called by the impl when the surface is ready to be displayed
pub fn map(self: *Self) !void {
    log.debug("view '{s}' mapped", .{self.getTitle()});

    {
        assert(self.foreign_toplevel_handle == null);
        const handle = try wlr.ForeignToplevelHandleV1.create(server.foreign_toplevel_manager);
        self.foreign_toplevel_handle = handle;

        handle.events.request_activate.add(&self.foreign_activate);
        handle.events.request_fullscreen.add(&self.foreign_fullscreen);
        handle.events.request_close.add(&self.foreign_close);

        if (self.getTitle()) |s| handle.setTitle(s);
        if (self.getAppId()) |s| handle.setAppId(s);

        handle.outputEnter(self.output.wlr_output);
    }

    server.xdg_activation.events.request_activate.add(&self.request_activate);

    // Add the view to the stack of its output
    const node = @fieldParentPtr(ViewStack(Self).Node, "view", self);
    self.output.views.attach(node, server.config.attach_mode);

    // Inform all seats that the view has been mapped so they can handle focus
    var it = server.input_manager.seats.first;
    while (it) |seat_node| : (it = seat_node.next) try seat_node.data.handleViewMap(self);

    self.sendEnter(self.output);

    self.output.sendViewTags();

    self.applyPending();
}

/// Called by the impl when the surface will no longer be displayed
pub fn unmap(self: *Self) void {
    log.debug("view '{s}' unmapped", .{self.getTitle()});

    if (self.saved_buffers.items.len == 0) self.saveBuffers();

    assert(self.surface != null);
    self.surface = null;

    // Inform all seats that the view has been unmapped so they can handle focus
    var it = server.input_manager.seats.first;
    while (it) |seat_node| : (it = seat_node.next) seat_node.data.handleViewUnmap(self);

    assert(self.foreign_toplevel_handle != null);
    self.foreign_activate.link.remove();
    self.foreign_fullscreen.link.remove();
    self.foreign_close.link.remove();
    self.foreign_toplevel_handle.?.destroy();
    self.foreign_toplevel_handle = null;

    self.request_activate.link.remove();

    self.output.sendViewTags();

    // Still need to arrange if fullscreened from the layout
    if (!self.current.float) self.output.arrangeViews();

    server.root.startTransaction();
}

pub fn notifyTitle(self: Self) void {
    if (self.foreign_toplevel_handle) |handle| {
        if (self.getTitle()) |s| handle.setTitle(s);
    }
    // Send title to all status listeners attached to a seat which focuses this view
    var seat_it = server.input_manager.seats.first;
    while (seat_it) |seat_node| : (seat_it = seat_node.next) {
        if (seat_node.data.focused == .view and seat_node.data.focused.view == &self) {
            var client_it = seat_node.data.status_trackers.first;
            while (client_it) |client_node| : (client_it = client_node.next) {
                client_node.data.sendFocusedView();
            }
        }
    }
}

pub fn notifyAppId(self: Self) void {
    if (self.foreign_toplevel_handle) |handle| {
        if (self.getAppId()) |s| handle.setAppId(s);
    }
}

/// Only honors the request if the view is already visible on the seat's
/// currently focused output. TODO: consider allowing this request to switch
/// output/tag focus.
fn handleForeignActivate(
    listener: *wl.Listener(*wlr.ForeignToplevelHandleV1.event.Activated),
    event: *wlr.ForeignToplevelHandleV1.event.Activated,
) void {
    const self = @fieldParentPtr(Self, "foreign_activate", listener);
    const seat = @intToPtr(*Seat, event.seat.data);
    seat.focus(self);
    server.root.startTransaction();
}

fn handleForeignFullscreen(
    listener: *wl.Listener(*wlr.ForeignToplevelHandleV1.event.Fullscreen),
    event: *wlr.ForeignToplevelHandleV1.event.Fullscreen,
) void {
    const self = @fieldParentPtr(Self, "foreign_fullscreen", listener);
    self.pending.fullscreen = event.fullscreen;
    self.applyPending();
}

fn handleForeignClose(
    listener: *wl.Listener(*wlr.ForeignToplevelHandleV1),
    _: *wlr.ForeignToplevelHandleV1,
) void {
    const self = @fieldParentPtr(Self, "foreign_close", listener);
    self.close();
}

fn handleRequestActivate(
    _: *wl.Listener(*wlr.XdgActivationV1.event.RequestActivate),
    event: *wlr.XdgActivationV1.event.RequestActivate,
) void {
    if (fromWlrSurface(event.surface)) |view| {
        if (view.current.focus == 0) {
            view.pending.urgent = true;
            server.root.startTransaction();
        }
    }
}