#pragma once

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

typedef uint8_t uiChannel;

typedef struct uiPixel {
  uiChannel r, g, b, a;
} uiPixel;

typedef struct uiSize {
  int width;
  int height;
} uiSize;

/// A UI surface to which widgets are rendered.
typedef struct uiSurface {
  int      width;
  int      height;
  uiPixel* pixels;
} uiSurface;

/// Rectangle.
/// (x,y) is the top-left corner.
typedef struct uiRect {
  int x;
  int y;
  int width;
  int height;
} uiRect;

/// Point.
typedef struct uiPoint {
  int x;
  int y;
} uiPoint;

/// Widget ID.
typedef int uiWidgetId;

/// Widget type.
typedef enum uiWidgetType {
  uiTypeButton,
  uiTypeFrame,
  uiTypeLabel,
  uiTypeTable,
  uiTypeMax,
} uiWidgetType;

typedef struct uiButton uiButton;
typedef struct uiFrame  uiFrame;
typedef struct uiLabel  uiLabel;
typedef struct uiTable  uiTable;
typedef struct uiWidget uiWidget;

/// Widget pointer.
typedef struct uiPtr {
  uiWidgetType type;
  union {
    uiButton* button;
    uiFrame*  frame;
    uiLabel*  label;
    uiTable*  table;
    uiWidget* widget;
  };
} uiPtr;

/// Mouse button.
typedef enum uiMouseButton {
  uiLMB,
  uiRMB,
  uiMouseButtonMax,
} uiMouseButton;

/// Mouse button state.
typedef enum uiMouseButtonState {
  uiMouseUp,
  uiMouseDown,
} uiMouseButtonState;

/// Mouse button event.
typedef struct uiMouseButtonEvent {
  uiMouseButton      button;
  uiMouseButtonState state;
  uiPoint            mouse_position;
} uiMouseButtonEvent;

/// Mouse click event.
typedef struct uiMouseClickEvent {
  uiMouseButton button;
  uiPoint       mouse_position;
} uiMouseClickEvent;

/// Mouse scroll event.
typedef struct uiMouseScrollEvent {
  uiPoint mouse_position;
  int     scroll_offset; /// Positive = down; negative = up.
} uiMouseScrollEvent;

/// Input event type.
typedef enum uiInputEventType {
  uiEventMouseButton,
  uiEventMouseClick,
  uiEventMouseScroll,
} uiInputEventType;

/// Input event.
typedef struct uiInputEvent {
  uiInputEventType type;
  union {
    uiMouseButtonEvent mouse_button;
    uiMouseClickEvent  mouse_click;
    uiMouseScrollEvent mouse_scroll;
  };
} uiInputEvent;

/// Table click event.
typedef struct uiTableClickEvent {
  int col;
  int row;
} uiTableClickEvent;

/// UI event type.
typedef enum uiWidgetEventType {
  uiWidgetEventClick,
} uiWidgetEventType;

/// UI event.
/// These are events from the UI widgets back to the client application.
typedef struct uiWidgetEvent {
  uiWidgetEventType type;
  uiPtr             widget;
  union {
    uiTableClickEvent table_click;
  };
} uiWidgetEvent;

// -----------------------------------------------------------------------------
// Library.

/// Initialize the UI library.
/// This should be called once during application startup.
bool uiInit(void);

/// Shutdown the UI library.
/// This should be called once during application shutdown.
void uiShutdown(void);

// -----------------------------------------------------------------------------
// Widget pointers.

uiPtr uiMakeButtonPtr(uiButton*);
uiPtr uiMakeFramePtr(uiFrame*);
uiPtr uiMakeLabelPtr(uiLabel*);
uiPtr uiMakeTablePtr(uiTable*);

uiButton* uiGetButtonPtr(uiPtr ptr);
uiFrame*  uiGetFramePtr(uiPtr ptr);
uiLabel*  uiGetLabelPtr(uiPtr ptr);
uiTable*  uiGetTablePtr(uiPtr ptr);

// -----------------------------------------------------------------------------
// Widget.

uiWidgetType uiWidgetGetType(const uiWidget*);

void uiWidgetSetParent(uiPtr child, uiPtr parent);

// -----------------------------------------------------------------------------
// Button.

/// Create a button.
uiButton* uiMakeButton(const char* text);

// -----------------------------------------------------------------------------
// Frame.

/// Create a frame.
uiFrame* uiMakeFrame(void);

/// Destroy the frame.
void uiDestroyFrame(uiFrame**);

/// Resize the frame.
void uiResizeFrame(uiFrame*, int width, int height);

/// Get the frame's dimensions.
uiSize uiGetFrameSize(const uiFrame*);

// -----------------------------------------------------------------------------
// Label.

/// Create a label.
uiLabel* uiMakeLabel(const char* text);

/// Return the label's text.
const char* uiLabelGetText(const uiLabel*);

// -----------------------------------------------------------------------------
// Table.

/// Create a table.
uiTable* uiMakeTable(int rows, int cols, const char** header);

/// Clear the table.
/// This clears the contents, but not the header.
void uiTableClear(uiTable*);

/// Add a row.
void uiTableAddRow(uiTable*, const char** row);

/// Set the table's cell.
void uiTableSet(uiTable*, int row, int col, uiPtr widget);

/// Get the table's cell.
const uiWidget* uiTableGet(const uiTable*, int row, int col);

/// Get the table's cell.
uiWidget* uiTableGetMut(uiTable*, int row, int col);

// -----------------------------------------------------------------------------
// Rendering.

/// Render the frame.
void uiRender(const uiFrame*, uiSurface*);

// -----------------------------------------------------------------------------
// UI Events.

/// Get the widget events.
/// Return the number of events in the returned array.
///
/// This function clears the events recorded by the UI library since the last
/// input event. Subsequent calls to this function, with no further user input,
/// therefore report zero widget events.
int uiGetEvents(uiWidgetEvent const**);

// -----------------------------------------------------------------------------
// User input.

/// Send an input event to the UI.
/// Return true if the UI requires a redraw.
bool uiSendEvent(uiFrame*, const uiInputEvent*);