/**
 * GUI framework
 * 
 * Created on 2020/01/03.
 */

#ifndef REFLOWER_LIQUID_H
#define REFLOWER_LIQUID_H

#include <stdint.h>
#include <stdbool.h>

struct Liquid;

enum InputEvent_Kind {
    InputEventKind_Wheel,
    InputEventKind_Button,
};

struct InputEvent {
    enum InputEvent_Kind kind;
    union {
        struct {
            // Wheel delta
            int32_t delta;
        } wheel;
        struct {
            // Button state
            bool state;
        } button;
    };
};

static inline struct InputEvent InputEvent_Wheel(int32_t delta)
{
    return (struct InputEvent) {
        .kind = InputEventKind_Wheel,
        .wheel = {.delta = delta}
    };
}

/**
 * Button event (push, release)
 *
 * @param state - pushed
 * @return event
 */
static inline struct InputEvent InputEvent_Button(bool state)
{
    return (struct InputEvent) {
        .kind = InputEventKind_Button,
        .button = {.state = state},
    };
}

enum SceneEvent_Kind {
    SceneEventKind_Close,
    SceneEventKind_OpenChild,
    SceneEventKind_RequestRepaint,
    SceneEventKind_None,
};

// forward declaration
struct Scene;

/**
 * Scene event, returned from some scene methods.
 *
 * Use the constructor functions to create this struct.
 */
struct SceneEvent {
    /** Event kind enum */
    enum SceneEvent_Kind kind;
    union {
        /* data for Close event kind */
        struct {
            // Status code
            int32_t status;
            // Return data on heap
            void *data;
        } close;
        /* Data for Open event kind */
        struct {
            // Scene (initialized, with options loaded in through the constructor)
            struct Scene *scene;
            // Tag used by parent to identify the open child
            uint32_t tag;
        } open;
    };
};

/**
 * Create empty (null object) scene event.
 *
 * @return event
 */
static inline struct SceneEvent SceneEvent_None(void)
{
    return (struct SceneEvent) {
        .kind = SceneEventKind_None,
    };
}

/**
 * Request scene repaint
 *
 * @return event
 */
static inline struct SceneEvent SceneEvent_Repaint(void)
{
    return (struct SceneEvent) {
        .kind = SceneEventKind_RequestRepaint
    };
}

/**
 * Request a sub-scene to be opened
 *
 * @param child - child scene
 * @param tag - scene tag
 * @return event
 */
static inline struct SceneEvent SceneEvent_OpenChild(struct Scene *child, uint32_t tag) {
    return (struct SceneEvent) {
        .kind = SceneEventKind_OpenChild,
        .open = { .scene = child, .tag=tag },
    };
}

/**
 * Close this scene, returning to parent.
 *
 * @param status - status number for the parent
 * @param data - heap-allocated data for parent, can be NULL; e.g. user input as string.
 * @return event
 */
static inline struct SceneEvent SceneEvent_Close(int32_t status, void *data)
{
    return (struct SceneEvent) {
        .kind = SceneEventKind_Close,
        .close = {.status = status, .data=data},
    };
}

/**
 * Scene::onInput fp type - handle user input
 *
 * @param scene - self
 * @param event - the input event
 * @return follow-up scene event, can be SceneEvent_None() if not used.
 */
typedef struct SceneEvent (*Scene_onInput_t)(struct Scene *scene, struct InputEvent event);

/**
 * Scene::onChildReturn fp type
 *
 * @param scene - self
 * @param tag - child's tag
 * @param status - status code returned from the child
 * @param data - data returned from the child, must be heap-allocated if not NULL.
 * @return follow-up scene event, can be SceneEvent_None() if not used.
 */
typedef struct SceneEvent (*Scene_onChildReturn_t)(struct Scene *scene, uint32_t tag, int32_t status, void *data);

/**
 * Scene::onTick fp type
 *
 * @param scene - self
 * @return follow-up scene event, can be SceneEvent_None() if not used.
 */
typedef struct SceneEvent (*Scene_onTick_t)(struct Scene *scene);

/**
 * Scene::paint fp type
 *
 * @param scene - self
 */
typedef void (*Scene_paint_t)(struct Scene *scene);

/**
 * Scene::free fp type.
 * Release internally allocated resources.
 * This is called by the GUI engine when the scene is closed.
 *
 * @param scene - self
 */
typedef void (*Scene_free_t)(struct Scene *scene);

/**
 * Scene instance in the framework
 */
struct Scene {
    /**
     * Tag given to the scene by its parent to identify its close event.
     */
    uint32_t tag;

    /**
     * Handle input event.
     * Can return a follow-up scene event, e.g. repaint request.
     * Nullable field.
     */
    Scene_onInput_t onInput;

    /**
     * Child scene closed, handle its return value and data, if any.
     * Can return a follow-up scene event.
     * In any case, the scene will be re-painted, if it stays open and on top.
     * Nullable field.
     */
    Scene_onChildReturn_t onChildReturn;

    /**
     * Handle a periodic tick (10ms).
     * Can return a follow-up scene event, e.g. repaint request.
     * Nullable field.
     */
    Scene_onTick_t onTick;

    /**
     * Draw the scene to the LCD buffer.
     * DO NOT write to the display yet, it will be done by the GUI engine.
     *
     * MANDATORY FIELD
     */
    Scene_paint_t paint;

    /**
     * Release internally allocated resources, if any. Called on close.
     * Nullable field.
     */
    Scene_free_t free;
};

/** return 1 if repaint requested */
bool Liquid_handleInput(struct Liquid *container, struct InputEvent event);

/** return 1 if repaint requested */
bool Liquid_handleTick(struct Liquid *container);

/** render the active scene */
void Liquid_paint(struct Liquid *container);

/** Initialize the GUI system with a root scene */
struct Liquid *Liquid_start(void);

#endif //REFLOWER_LIQUID_H