/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

use azure::azure_hl::Color;
use constellation_msg::{Key, KeyState, KeyModifiers};
use geom::point::Point2D;
use geom::rect::Rect;
use layers::platform::surface::NativeGraphicsMetadata;
use layers::layers::LayerBufferSet;
use std::fmt::{Formatter, Debug};
use std::fmt;

use constellation_msg::PipelineId;

/// A newtype struct for denoting the age of messages; prevents race conditions.
#[derive(PartialEq, Eq, Debug, Copy, Clone, PartialOrd, Ord)]
pub struct Epoch(pub u32);

impl Epoch {
    pub fn next(&mut self) {
        let Epoch(ref mut u) = *self;
        *u += 1;
    }
}

#[derive(PartialEq, Eq, Debug, Copy, Clone)]
pub struct FrameTreeId(pub u32);

impl FrameTreeId {
    pub fn next(&mut self) {
        let FrameTreeId(ref mut u) = *self;
        *u += 1;
    }
}

#[derive(Clone, PartialEq, Eq, Copy)]
pub struct LayerId(pub usize, pub u32);

impl Debug for LayerId {
    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
        let LayerId(a, b) = *self;
        write!(f, "Layer({}, {})", a, b)
    }
}

impl LayerId {
    /// FIXME(#2011, pcwalton): This is unfortunate. Maybe remove this in the future.
    pub fn null() -> LayerId {
        LayerId(0, 0)
    }
}

/// The scrolling policy of a layer.
#[derive(Clone, PartialEq, Eq, Copy)]
pub enum ScrollPolicy {
    /// These layers scroll when the parent receives a scrolling message.
    Scrollable,
    /// These layers do not scroll when the parent receives a scrolling message.
    FixedPosition,
}

/// All layer-specific information that the painting task sends to the compositor other than the
/// buffer contents of the layer itself.
#[derive(Copy, Clone)]
pub struct LayerProperties {
    /// An opaque ID. This is usually the address of the flow and index of the box within it.
    pub id: LayerId,
    /// The position and size of the layer in pixels.
    pub rect: Rect<f32>,
    /// The background color of the layer.
    pub background_color: Color,
    /// The scrolling policy of this layer.
    pub scroll_policy: ScrollPolicy,
}

/// The interface used by the painter to acquire draw targets for each paint frame and
/// submit them to be drawn to the display.
pub trait PaintListener {
    fn get_graphics_metadata(&mut self) -> Option<NativeGraphicsMetadata>;

    /// Informs the compositor of the layers for the given pipeline. The compositor responds by
    /// creating and/or destroying paint layers as necessary.
    fn initialize_layers_for_pipeline(&mut self,
                                      pipeline_id: PipelineId,
                                      properties: Vec<LayerProperties>,
                                      epoch: Epoch);

    /// Sends new buffers for the given layers to the compositor.
    fn assign_painted_buffers(&mut self,
                              pipeline_id: PipelineId,
                              epoch: Epoch,
                              replies: Vec<(LayerId, Box<LayerBufferSet>)>,
                              frame_tree_id: FrameTreeId);

    // Notification that the paint task wants to exit.
    fn notify_paint_task_exiting(&mut self, pipeline_id: PipelineId);
}

/// The interface used by the script task to tell the compositor to update its ready state,
/// which is used in displaying the appropriate message in the window's title.
pub trait ScriptListener {
    fn scroll_fragment_point(&mut self,
                             pipeline_id: PipelineId,
                             layer_id: LayerId,
                             point: Point2D<f32>);
    /// Informs the compositor that the title of the page with the given pipeline ID has changed.
    fn set_title(&mut self, pipeline_id: PipelineId, new_title: Option<String>);
    fn close(&mut self);
    fn dup(&mut self) -> Box<ScriptListener+'static>;
    fn send_key_event(&mut self, key: Key, state: KeyState, modifiers: KeyModifiers);
}