//! Common traits for input backends to receive input from.

use backend::NewIdType;

/// A seat describes a group of input devices and at least one
/// graphics device belonging together.
///
/// By default only one seat exists for most systems and smithay backends
/// however multiseat configurations are possible and should be treated as
/// separated users, all with their own focus, input and cursor available.
///
/// Seats can be checked for equality and hashed for differentiation.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub struct Seat { id: u32 }

impl NewIdType for Seat
{
    fn new(id: u32) -> Seat
    {
        Seat { id: id }
    }
}

/// State of key on a keyboard. Either pressed or released
#[derive(Debug, PartialEq, Eq, Clone, Copy)]
pub enum KeyState {
    /// Key is released
    Released,
    /// Key is pressed
    Pressed,
}

/// A particular mouse button
#[derive(Debug, PartialEq, Eq, Clone, Copy)]
pub enum MouseButton {
    /// Left mouse button
    Left,
    /// Middle mouse button
    Middle,
    /// Right mouse button
    Right,
    /// Other mouse button with index
    Other(u8),
}

/// State of a button on a mouse. Either pressed or released
#[derive(Debug, PartialEq, Eq, Clone, Copy)]
pub enum MouseButtonState {
    /// Button is released
    Released,
    /// Button is pressed
    Pressed,
}

/// Axis when scrolling
#[derive(Debug, PartialEq, Eq, Clone, Copy)]
pub enum Axis
{
    /// Vertical axis
    Vertical,
    /// Horizonal axis
    Horizontal,
}

/// Source of an axis when scrolling
#[derive(Debug, PartialEq, Eq, Clone, Copy)]
pub enum AxisSource
{
    /// Finger. Mostly used for trackpads.
    ///
    /// Guarantees that a scroll sequence is terminated with a scroll value of 0.
    /// A caller may use this information to decide on whether kinetic scrolling should
    /// be triggered on this scroll sequence.
    ///
    /// The coordinate system is identical to the
    /// cursor movement, i.e. a scroll value of 1 represents the equivalent relative
    /// motion of 1.
    Finger,
    /// Continous scrolling device. Almost identical to `Finger`
    ///
    /// No terminating event is guaranteed (though it may happen).
    ///
    /// The coordinate system is identical to
    /// the cursor movement, i.e. a scroll value of 1 represents the equivalent relative
    /// motion of 1.
    Continous,
    /// Scroll wheel.
    ///
    /// No terminating event is guaranteed (though it may happen). Scrolling is in
    /// discrete steps. It is up to the caller how to interpret such different step sizes.
    Wheel,
    /// Scrolling through tilting the scroll wheel.
    ///
    /// No terminating event is guaranteed (though it may happen). Scrolling is in
    /// discrete steps. It is up to the caller how to interpret such different step sizes.
    WheelTilt,
}

/// Slot of a different touch event.
///
/// Touch events are groubed by slots, usually to identify different
/// fingers on a multi-touch enabled input device. Events should only
/// be interpreted in the context of other events on the same slot.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub struct TouchSlot { id: u32 }

impl NewIdType for TouchSlot
{
    fn new(id: u32) -> TouchSlot
    {
        TouchSlot { id: id }
    }
}

/// Touch event
#[derive(Debug, PartialEq, Clone, Copy)]
pub enum TouchEvent
{
    /// The start of an event at a given position (x, y).
    ///
    /// If the device has multi-touch capabilities a slot is given.
    Down {
        /// `TouchSlot`, if the device has multi-touch capabilities
        slot: Option<TouchSlot>,
        /// Absolute x-coordinate of the touch position.
        x: f64,
        /// Absolute y-coordinate of the touch position.
        y: f64
    },
    /// Movement of a touch on the device surface to a given position (x, y).
    ///
    /// If the device has multi-touch capabilities a slot is given.
    Motion {
        /// `TouchSlot`, if the device has multi-touch capabilities
        slot: Option<TouchSlot>,
        /// Absolute x-coordinate of the final touch position after the motion.
        x: f64,
        /// Absolute y-coordinate of the final touch position after the motion.
        y: f64 },
    /// Stop of an event chain.
    ///
    /// If the device has multi-touch capabilities a slot is given.
    Up {
        /// `TouchSlot`, if the device has multi-touch capabilities
        slot: Option<TouchSlot>
    },
    /// Cancel of an event chain. All previous events in the chain should be ignored.
    ///
    /// If the device has multi-touch capabilities a slot is given.
    Cancel {
        /// `TouchSlot`, if the device has multi-touch capabilities
        slot: Option<TouchSlot>
    },
    /// Signals the end of a set of touchpoints at one device sample time.
    Frame
}

/// Trait that describes objects providing a source of input events. All input backends
/// need to implemenent this and provide the same base gurantees about the presicion of
/// given events.
pub trait InputBackend: Sized {
    /// Type of input device associated with the backend
    type InputConfig;
    /// Sets a new handler for this `InputBackend`
    fn set_handler<H: InputHandler<Self> + 'static>(&mut self, handler: H);
    /// Get a reference to the currently set handler, if any
    fn get_handler(&mut self) -> Option<&mut InputHandler<Self>>;
    /// Clears the currently handler, if one is set
    fn clear_handler(&mut self);

    /// Get current `InputConfig`
    fn input_config(&mut self) -> &mut Self::InputConfig;

    /// Sets the cursor position, useful for e.g. pointer wrapping.
    ///
    /// Not guaranteed to be supported on every backend. The result usually
    /// depends on the capability of the backend, but may also fail for certain
    /// specific actions. See the backends documentation.
    fn set_cursor_position(&mut self, x: u32, y: u32) -> Result<(), ()>;
}

/// Implement to receive input events from any `InputBackend`.
pub trait InputHandler<B: InputBackend> {
    /// Called when a new `Seat` has been created
    fn on_seat_created(&mut self, seat: &Seat);
    /// Called when an existing `Seat` has been destroyed.
    fn on_seat_destroyed(&mut self, seat: &Seat);
    /// Called when a new keyboard event was received.
    ///
    /// # Arguments
    ///
    /// - `seat` - The `Seat` the event belongs to
    /// - `time` - A upward counting variable useful for event ordering. Makes no gurantees about actual time passed between events.
    /// - `key_code` - Code of the pressed key. See linux/input-event-codes.h
    /// - `state` - `KeyState` of the event
    /// - `count` - Total number of keys pressed on all devices on the associated `Seat`
    ///
    /// # TODO:
    /// - check if events can arrive out of order.
    /// - Make stronger time guarantees
    fn on_keyboard_key(&mut self, seat: &Seat, time: u32, key_code: u32, state: KeyState, count: u32);
    /// Called when a new pointer movement event was received.
    ///
    /// # Arguments
    ///
    /// - `seat` - The `Seat` the event belongs to
    /// - `time` - A upward counting variable useful for event ordering. Makes no gurantees about actual time passed between events.
    /// - `to` - Absolute screen coordinates of the pointer moved to.
    ///
    /// # TODO:
    /// - check if events can arrive out of order.
    /// - Make stronger time guarantees
    fn on_pointer_move(&mut self, seat: &Seat, time: u32, to: (u32, u32));
    /// Called when a new pointer button event was received.
    ///
    /// # Arguments
    ///
    /// - `seat` - The `Seat` the event belongs to
    /// - `time` - A upward counting variable useful for event ordering. Makes no gurantees about actual time passed between events.
    /// - `button` - Which button was pressed..
    /// - `state` - `MouseButtonState` of the event
    ///
    /// # TODO:
    /// - check if events can arrive out of order.
    /// - Make stronger time guarantees
    fn on_pointer_button(&mut self, seat: &Seat, time: u32, button: MouseButton, state: MouseButtonState);
    /// Called when a new pointer scroll event was received.
    ///
    /// # Arguments
    ///
    /// - `seat` - The `Seat` the event belongs to
    /// - `time` - A upward counting variable useful for event ordering. Makes no gurantees about actual time passed between events.
    /// - `axis` - `Axis` this event was generated for.
    /// - `source` - Source of the scroll event. Important for interpretation of `amount`.
    /// - `amount` - Amount of scrolling on the given `Axis`. See `source` for interpretation.
    ///
    /// # TODO:
    /// - check if events can arrive out of order.
    /// - Make stronger time guarantees
    fn on_pointer_scroll(&mut self, seat: &Seat, time: u32, axis: Axis, source: AxisSource, amount: f64);
    /// Called when a new touch event was received.
    ///
    /// # Arguments
    ///
    /// - `seat` - The `Seat` the event belongs to
    /// - `time` - A upward counting variable useful for event ordering. Makes no gurantees about actual time passed between events.
    /// - `event` - Touch event recieved. See `TouchEvent`.
    ///
    /// # TODO:
    /// - check if events can arrive out of order.
    /// - Make stronger time guarantees
    fn on_touch(&mut self, seat: &Seat, time: u32, event: TouchEvent);

    /// Called when the `InputConfig` was changed through an external event.
    ///
    /// What kind of events can trigger this call is completely backend dependent.
    /// E.g. an input devices was attached/detached or changed it's own configuration.
    fn on_input_config_changed(&mut self, config: &mut B::InputConfig);
}

impl<B: InputBackend> InputHandler<B> for Box<InputHandler<B>> {
    fn on_seat_created(&mut self, seat: &Seat) {
        (**self).on_seat_created(seat)
    }

    fn on_seat_destroyed(&mut self, seat: &Seat) {
        (**self).on_seat_destroyed(seat)
    }

    fn on_keyboard_key(&mut self, seat: &Seat, time: u32, key_code: u32, state: KeyState, count: u32) {
        (**self).on_keyboard_key(seat, time, key_code, state, count)
    }

    fn on_pointer_move(&mut self, seat: &Seat, time: u32, to: (u32, u32)) {
        (**self).on_pointer_move(seat, time, to)
    }

    fn on_pointer_button(&mut self, seat: &Seat, time: u32, button: MouseButton, state: MouseButtonState) {
        (**self).on_pointer_button(seat, time, button, state)
    }

    fn on_pointer_scroll(&mut self, seat: &Seat, time: u32, axis: Axis, source: AxisSource, amount: f64) {
        (**self).on_pointer_scroll(seat, time, axis, source, amount)
    }

    fn on_touch(&mut self, seat: &Seat, time: u32, event: TouchEvent) {
        (**self).on_touch(seat, time, event)
    }

    fn on_input_config_changed(&mut self, config: &mut B::InputConfig) {
        (**self).on_input_config_changed(config)
    }
}