#include <ui.h>

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

#include <cassert.h>

static void LayoutWidget(uiWidget* widget, int width, int height);

/// Return the area required to fit the text.
static uiSize GetTextSize(const string* text) {
  return (uiSize){
      .width  = (int)(g_ui.font->header.glyph_width * string_length(*text)),
      .height = (int)g_ui.font->header.glyph_height};
}

static void ResizeButton(uiButton* button, int width, int height) {
  assert(button);

  // TODO: Define the button's border. But don't store this. Make it a function
  //  shared between layout.c and render.c. Define it in a new common.h?

  const uiSize minSize = GetTextSize(&button->text);
  uiSize       size    = minSize;
  if (button->widget.stretch & uiStretchX) {
    size.width = Max(size.width, width);
  }
  if (button->widget.stretch & uiStretchY) {
    size.height = Max(size.height, height);
  }
  button->widget.rect.width  = size.width;
  button->widget.rect.height = size.height;
}

static void ResizeLabel(uiLabel* label, int width, int height) {
  assert(label);

  const uiSize minSize = GetTextSize(&label->text);
  uiSize       size    = minSize;
  if (label->widget.stretch & uiStretchX) {
    size.width = Max(size.width, width);
  }
  if (label->widget.stretch & uiStretchY) {
    size.height = Max(size.height, height);
  }
  label->widget.rect.width  = size.width;
  label->widget.rect.height = size.height;
}

static void LayoutTable(uiTable* table, int width, int height) {
  assert(table);

  if ((table->cols == 0) || (table->rows == 0)) {
    table->widget.rect.width  = 0;
    table->widget.rect.height = 0;
    return;
  }

  table->widget.rect.width  = width;
  table->widget.rect.height = height;

  // Compute the number of rows that are visible at once.
  table->num_visible_rows =
      Min(table->rows, height / g_ui.font->header.glyph_height);
  assert(table->num_visible_rows <= table->rows);

  // Determine if there is vertical overflow. This determines whether we need to
  // render a scroll bar, in which case room must be made for it.
  table->flags.vertical_overflow =
      (table->rows * g_ui.font->header.glyph_height) >
      table->widget.rect.height;

  // Surface width: W.
  // Columns: N
  //
  // First, find the minimum width of each column based on their contents.
  //
  // If the sum of column widths < N, then distribute the extra space first
  // among the smallest columns and building up towards the larger.
  //
  // If the sum of column widths > N, subtract from the largest column first and
  // move towards the smaller ones to distribute the space as evenly as
  // possible.

  // Find the minimum width for each column.
  int* widths = table->widths;
  // Header.
  for (int col = 0; col < table->cols; ++col) {
    const uiCell* cell   = &table->header[col];
    const int     length = (int)string_length(cell->text);

    widths[col] = length;
  }
  // Table contents.
  for (int row = 0; row < table->rows; ++row) {
    for (int col = 0; col < table->cols; ++col) {
      const uiCell* cell   = TableGetCell(table, row, col);
      const int     length = (int)string_length(cell->text);

      widths[col] = length > widths[col] ? length : widths[col];
    }
  }
  // Multiply string lengths times glyph width to compute pixel size.
  for (int col = 0; col < table->cols; ++col) {
    widths[col] *= g_ui.font->header.glyph_width;
  }

  // Find the sum of widths.
  int used_width = 0;
  for (int col = 0; col < table->cols; ++col) {
    used_width += widths[col];
  }

  // Pad if available width is larger than sum of widths.
  if (used_width < width) {
    // Divide evenly among columns.
    // const int extra = width - used_width;
    //    const int pad   = extra / table->cols;
    //    const int mod   = extra % table->cols;
    //    for (int col = 0; col < table->cols; ++col) {
    //      table->widths[col] += pad + (col < mod ? 1 : 0);
    //    }

    int extra = width - used_width;
    while (extra > 0) {
      // Find smallest column.
      int smallest = 0;
      for (int col = 1; col < table->cols; ++col) {
        if (widths[col] < widths[smallest]) {
          smallest = col;
        }
      }
      // Pad it and subtract from the budget.
      widths[smallest] += 1;
      extra--;
    }
  }
  // Shrink if available width is smaller than the sum of widths.
  else if (used_width > width) {
    int deficit = used_width - width;
    while (deficit > 0) {
      // Find largest column.
      int largest = 0;
      for (int col = 1; col < table->cols; ++col) {
        if (widths[col] > widths[largest]) {
          largest = col;
        }
      }
      // Shrink it and subtract from the deficit.
      widths[largest] -= 1;
      deficit--;
    }
  }

  // Now make room for the scroll bar, if necessary.
  uiScrollbar* scrollbar = &table->scrollbar;
  if (table->flags.vertical_overflow) {
    // Subtract room from table columns.
    const int offset    = ScrollbarWidth / table->cols;
    const int remainder = ScrollbarWidth % table->cols;
    for (int col = 0; col < table->cols; ++col) {
      table->widths[col] -= offset + (col < remainder ? 1 : 0);
      assert(table->widths[col] >= 0);
    }

    // Set scrollbar layout.
    scrollbar->width         = ScrollbarWidth;
    scrollbar->height        = height;
    scrollbar->handle_height = (int)((double)table->num_visible_rows /
                                     (double)table->rows * (double)height);
    uiTableScroll(table, table->offset);
  } else { // Scroll bar not visible.
    scrollbar->width         = 0;
    scrollbar->height        = 0;
    scrollbar->handle_height = 0;
    scrollbar->handle_y      = 0;
  }
}

static void Layout(uiLayout* layout, int width, int height) {
  assert(layout);

  layout->widget.rect.width  = width;
  layout->widget.rect.height = height;

  // Resizing a layout can get complicated depending on how much flexibility we
  // want to support. To start simple:
  // 1. Let the layout stretch to occupy the given size.
  // 2. For each child, check whether the child has a fixed width/height or
  //    if it wants to grow.
  // 3. Fixed-size widgets get their requested size.
  // 4. Variably-sized widgets get the remainder of the space uniformly
  //    distributed among them.

  // First resize fixed-size widgets and compute free area, if any, to determine
  // the size of stretchable widgets along the layout direction. Then resize
  // stretchable widgets by uniformly distributing the free area.
  switch (layout->direction) {
  case uiVertical: {
    // Resize fixed-size children and compute free area.
    int free_area         = height;
    int stretchable_count = 0; // Number of stretchable widgets.
    list_foreach(layout->widget.children, child, {
      if (child->stretch & uiStretchY) {
        stretchable_count++;
      } else {
        LayoutWidget(child, width, free_area);
        free_area -= child->rect.height;
      }
    });
    if (stretchable_count > 0) {
      // Resize stretchable children.
      const int stretchable_widget_size = free_area / stretchable_count;
      list_foreach(layout->widget.children, child, {
        if (child->stretch != uiStretchNone) {
          LayoutWidget(child, width, stretchable_widget_size);
        } else {
          LayoutWidget(child, width, height);
        }
      });
    }
    // Now position all widgets inside the layout.
    int y = 0;
    list_foreach(layout->widget.children, child, {
      child->rect.y = y;
      y += child->rect.height;
    });
    // Layout's width is max of its children.
    layout->widget.rect.width = 0;
    list_foreach(layout->widget.children, child, {
      layout->widget.rect.width =
          Max(layout->widget.rect.width, child->rect.width);
    });
    break;
  }
  case uiHorizontal: {
    // Resize fixed-size children and compute free area.
    int free_area         = width;
    int stretchable_count = 0; // Number of stretchable widgets.
    list_foreach(layout->widget.children, child, {
      if (child->stretch & uiStretchX) {
        stretchable_count++;
      } else {
        LayoutWidget(child, free_area, height);
        free_area -= child->rect.width;
      }
    });
    if (stretchable_count > 0) {
      // Resize stretchable children.
      const int stretchable_size = free_area / stretchable_count;
      list_foreach(layout->widget.children, child, {
        if (child->stretch != uiStretchNone) {
          LayoutWidget(child, stretchable_size, height);
        }
      });
    }
    // Now position all widgets inside the layout.
    int x = 0;
    list_foreach(layout->widget.children, child, {
      child->rect.x = x;
      x += child->rect.width;
    });
    // Layout's height is max of its children.
    layout->widget.rect.height = 0;
    list_foreach(layout->widget.children, child, {
      layout->widget.rect.height =
          Max(layout->widget.rect.height, child->rect.height);
    });
    break;
  }
  }
}

static void ResizeFrame(uiFrame* frame, int width, int height) {
  assert(frame);

  frame->widget.rect.width  = width;
  frame->widget.rect.height = height;

  list_foreach_mut(
      frame->widget.children, child, { LayoutWidget(child, width, height); });
}

void uiLayOut(uiFrame* frame, int width, int height) {
  assert(frame);
  LayoutWidget(&frame->widget, width, height);
}

static void LayoutWidget(uiWidget* widget, int width, int height) {
  assert(widget);

  switch (widget->type) {
  case uiTypeLayout:
    Layout((uiLayout*)widget, width, height);
    break;
  case uiTypeButton:
    ResizeButton((uiButton*)widget, width, height);
    break;
  case uiTypeFrame:
    ResizeFrame((uiFrame*)widget, width, height);
    break;
  case uiTypeLabel:
    ResizeLabel((uiLabel*)widget, width, height);
    break;
  case uiTypeEdit:
    // TODO: ResizeEdit()
    break;
  case uiTypeTable:
    LayoutTable((uiTable*)widget, width, height);
    break;
  case uiTypeMax:
    TRAP();
    break;
  }
}