#include <ui.h>

#include "event.h"
#include "uiLibrary.h"
#include "widget/widget.h"

#include <cassert.h>

/// Return true if the rectangle contains the point.
static bool RectContains(uiRect rect, uiPoint point) {
  return (rect.x <= point.x) && (point.x <= (rect.x + rect.width)) &&
         (rect.y <= point.y) && (point.y <= (rect.y + rect.height));
}

/// Get the bottom-most widget under the given mouse position.
static uiWidget* GetWidgetUnderMouse(uiWidget* parent, uiPoint mouse) {
  assert(parent);

  // First check the children so that the selection is from "most specific" to
  // "less specific" from the user's perspective.
  list_foreach(parent->children, child, {
    uiWidget* target = GetWidgetUnderMouse(child, mouse);
    if (target != 0) {
      return target;
    }
  });

  if (RectContains(parent->rect, mouse)) {
    return parent;
  }

  return 0;
}

// -----------------------------------------------------------------------------
// Scrollbar.

/// Process a scrollbar mouse button event.
static void MouseButtonScrollbar(
    uiScrollbar* scrollbar, const uiMouseButtonEvent* event) {
  assert(scrollbar);
  assert(event);

  if (event->button_state == uiMouseDown) {
    UI_LOG("scroll start");
    // TODO: I don't quite like this global state, but I also don't want to
    //  store input state inside the widgets. Define a struct for input handling
    //  and pass it to these functions instead?
    g_ui.scroll.scrollbar_handle_y_start = scrollbar->handle_y;
    g_ui.scroll.scrolling                = true;
  } else if (event->button_state == uiMouseUp) {
    UI_LOG("scroll end");
    g_ui.scroll.scrolling = false;
  }
}

/// Process a scrollbar mouse move event.
///
/// Return the amount scrolled relative to the scroll starting position, in
/// pixels.
static int MouseMoveScrollbar(
    uiScrollbar* scrollbar, const uiMouseMoveEvent* event) {
  assert(scrollbar);
  assert(event);

  const int delta = event->mouse_position.y - g_ui.mouse_down.start_point.y;
  ScrollbarScroll(scrollbar, g_ui.scroll.scrollbar_handle_y_start + delta);
  return delta;
}

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

/// Get the table row and column at the given pixel position, or whether the
/// scrollbar was hit.
static void GetTableRowColAtXy(
    const uiTable* table, uiPoint p, int* out_row, int* out_col,
    bool* out_scrollbar) {
  assert(table);
  assert(out_row);
  assert(out_col);

  const uiWidget* widget = (uiWidget*)table;

  int  col       = -1;
  int  row       = -1;
  bool scrollbar = false;

  if (RectContains(widget->rect, p)) {
    int x = p.x - widget->rect.x;
    for (col = 0; (col < table->cols) && (x > table->widths[col]); ++col) {
      x -= table->widths[col];
    }
    // 0 is the header, and we want to map the first row to 0, so -1.
    row = table->offset +
          ((p.y - widget->rect.y) / g_ui.font->header.glyph_height) - 1;
    // Scrollbar area check.
    if ((col >= table->cols) && (row < table->rows)) {
      col       = -1;
      scrollbar = true;
    }
    // Out of bounds.
    else if ((col >= table->cols) || (row >= table->rows)) {
      col = row = -1;
    }
  }

  *out_col       = col;
  *out_row       = row;
  *out_scrollbar = scrollbar;
}

/// Process a table mouse button event.
static void MouseButtonTable(uiTable* table, const uiMouseButtonEvent* event) {
  assert(table);
  assert(event);

  if (event->button_state == uiMouseDown) {
    int  row, col;
    bool scrollbar;
    GetTableRowColAtXy(table, event->mouse_position, &row, &col, &scrollbar);

    if (scrollbar) {
      MouseButtonScrollbar(&table->scrollbar, event);
    }
  } else if ((event->button_state == uiMouseUp) && g_ui.scroll.scrolling) {
    // The mouse up event need not happen while the mouse is on the scrollbar,
    // so process mouse-up regardless of whether the mouse is.
    MouseButtonScrollbar(&table->scrollbar, event);
  }
}

/// Process a table click event.
static void ClickTable(uiTable* table, const uiMouseClickEvent* event) {
  assert(table);
  assert(event);

  int  row, col;
  bool scrollbar;
  GetTableRowColAtXy(table, event->mouse_position, &row, &col, &scrollbar);

  if ((row != -1) && (col != -1)) {
    PushWidgetEvent(&(uiWidgetEvent){
        .type        = uiWidgetEventClick,
        .widget      = uiMakeTablePtr(table),
        .table_click = (uiTableClickEvent){.row = row, .col = col}
    });
  }
}

/// Process a table scroll event.
static void ScrollTable(uiTable* table, const uiMouseScrollEvent* event) {
  assert(table);
  assert(event);

  const int row = table->offset - event->scroll_offset;
  uiTableScroll(table, row);
}

/// Process a table mouse move event.
static void MouseMoveTable(uiTable* table, const uiMouseMoveEvent* event) {
  assert(table);
  assert(event);

  if (g_ui.scroll.scrolling) {
    MouseMoveScrollbar(&table->scrollbar, event);
    SyncTableToScrollbar(table);
  }
}

/// Process a mouse button event.
static bool ProcessMouseButtonEvent(
    uiWidget* widget, const uiMouseButtonEvent* event) {
  assert(widget);
  assert(event);

  bool processed = false;

  switch (widget->type) {
  case uiTypeTable:
    MouseButtonTable((uiTable*)widget, event);
    processed = true;
    break;
  default:
    break;
  }

  return processed;
}

/// Process a click event.
static bool ProcessMouseClickEvent(
    uiWidget* widget, const uiMouseClickEvent* event) {
  assert(widget);
  assert(event);

  bool processed = false;

  switch (widget->type) {
  case uiTypeTable:
    ClickTable((uiTable*)widget, event);
    processed = true;
    break;
  default:
    break;
  }

  return processed;
}

/// Process a scroll event.
static bool ProcessMouseScrollEvent(
    uiWidget* widget, const uiMouseScrollEvent* event) {
  assert(widget);
  assert(event);

  bool processed = false;

  switch (widget->type) {
  case uiTypeTable:
    ScrollTable((uiTable*)widget, event);
    processed = true;
    break;
  default:
    break;
  }

  return processed;
}

/// Process a mouse move event.
static bool ProcessMouseMoveEvent(
    uiWidget* widget, const uiMouseMoveEvent* event) {
  assert(widget);
  assert(event);

  bool processed = false;

  switch (widget->type) {
  case uiTypeTable:
    MouseMoveTable((uiTable*)widget, event);
    processed = true;
    break;
  default:
    break;
  }

  return processed;
}

bool uiSendEvent(uiFrame* frame, const uiInputEvent* event) {
  assert(frame);
  assert(event);

  // TODO: processed != redraw. The client will redraw if this function
  // returns
  //  true, but whether an event was processed does it imply that the UI needs
  //  a redraw.
  //
  // TODO: Also think about limiting redraws in xplorer to like 25fps or
  //  something in a "battery saving" mode of sorts.
  bool processed = false;

  switch (event->type) {
  case uiEventMouseButton: {
    const uiMouseButtonEvent* ev = &event->mouse_button;

    // Update the mouse button state.
    uiMouseButtonState* button_state    = &g_ui.mouse_button_state[ev->button];
    const uiMouseButtonState prev_state = *button_state;
    *button_state                       = ev->button_state;

    // If this is a mouse up event and a widget is currently being
    // mouse-downed, send the event to that widget.
    if ((ev->button_state == uiMouseUp) &&
        !uiIsNullptr(g_ui.mouse_down.widget)) {
      processed = ProcessMouseButtonEvent(g_ui.mouse_down.widget.widget, ev);
      g_ui.mouse_down = (uiMouseDownState){0};
    } else { // Mouse down or no widget.
      uiWidget* target =
          GetWidgetUnderMouse((uiWidget*)frame, ev->mouse_position);
      if (target) {
        processed = ProcessMouseButtonEvent(target, ev);
        if (processed && (ev->button_state == uiMouseDown)) {
          g_ui.mouse_down.widget      = uiMakeWidgetPtr(target);
          g_ui.mouse_down.start_point = ev->mouse_position;
        } else {
          g_ui.mouse_down = (uiMouseDownState){0};
        }
      }
    }

    if ((prev_state == uiMouseDown) && (ev->button_state == uiMouseUp)) {
      // Click.
      uiSendEvent(
          frame,
          &(uiInputEvent){
              .type        = uiEventMouseClick,
              .mouse_click = (uiMouseClickEvent){
                                                 .button = ev->button, .mouse_position = ev->mouse_position}
      });
    }
    break;
  }
  case uiEventMouseClick: {
    const uiMouseClickEvent* ev = &event->mouse_click;

    uiWidget* target =
        GetWidgetUnderMouse((uiWidget*)frame, ev->mouse_position);
    if (target) {
      processed = ProcessMouseClickEvent(target, ev);
    }
    break;
  }
  case uiEventMouseScroll: {
    const uiMouseScrollEvent* ev = &event->mouse_scroll;

    uiWidget* target =
        GetWidgetUnderMouse((uiWidget*)frame, ev->mouse_position);
    if (target) {
      processed = ProcessMouseScrollEvent(target, ev);
    }
    break;
  }
  case uiEventMouseMove: {
    const uiMouseMoveEvent* ev = &event->mouse_move;

    // If a widget is currently being moused-down, send the event to that
    // widget.
    if (!uiIsNullptr(g_ui.mouse_down.widget)) {
      processed = ProcessMouseMoveEvent(g_ui.mouse_down.widget.widget, ev);
    } else {
      uiWidget* target =
          GetWidgetUnderMouse((uiWidget*)frame, ev->mouse_position);
      if (target) {
        processed = ProcessMouseMoveEvent(target, ev);
      }
    }

    break;
  }
  }

  return processed;
}