--[[
- @author Bruno Massa
- @file
- Functions to aid in the creation of sortable tables.
-
- All tables created with a call to theme('table') have the option of having
- column headers that the user can click on to sort the table by that column.
]]

--[[
- Format a table cell.
-
- Adds a class attribute to all cells in the currently active column.
-
- @param cell
-   Table, The cell to format.
- @param header
-   Tablle, Column headers in the format described in themes.table().
- @param ts
-   Table, The current table sort context as returned from ajato_tablesort_init().
- @param i
-   Number, The index of the cell's table column.
- @return
-   Table, A properly formatted cell, ready for themes.table_cell()
]]
function ajato_tablesort_cell(cell, header, ts, i)
  if header and header[i] and header[i]['data'] and
      header[i]['data'] == ts['name'] and hv(header[i]['field']) then
    if type(cell) == 'table' then
      if cell['class'] then
        cell['class'] = cell['class'] ..' active'
      else
        cell['class'] = 'active'
      end
    else
      cell = {['data'] = cell, ['class'] = 'active'}
    end
  end
  return cell
end

--[[
- Determine the current sort criterion.
-
- @param headers
-   Table, Column headers in the format described in theme_table().
- @return
-   Table, The criterion, containing the keys:
-   - "name": The localized title of the table column.
-   - "sql": The name of the database field to sort on.
]]
function ajato_tablesort_get_order(headers)
  local order = sys['get']['order'] or ''
  local default

  for _, header in pairs(headers) do
    if header['data'] and order == header['data'] then
      return {['name'] = header['data'], ['sql'] = (header['field'] or '')}
    end

    if header['sort'] and header['sort'] == 'asc' or header['sort'] == 'desc' then
      default = {['name'] = header['data'], ['sql'] = header['field'] or ''}
    end
  end

  if default then
    return default
  else
    -- The first column specified is initial 'order by' field unless otherwise specified
    if type(headers[0]) == 'table' then
      return {['name'] = headers[0]['data'], ['sql'] = headers[0]['field']}
    else
      return {['name'] = headers[0]}
    end
  end
end

--[[
- Initialize the table sort context.
]]
function ajato_tablesort_init(header)
  local ts            = ajato_tablesort_get_order(header)
  ts['sort']          = ajato_tablesort_get_sort(header)
  ts['query_string']  = ajato_tablesort_get_querystring()
  return ts
end