compute-rect.kt

    data class SelectedArea(val x: Int, val y: Int, val width: Int, val height: Int) {
        companion object {
            fun computeSelectedArea(selectedCells: ObservableList<TablePosition<*, *>>): SelectedArea? {
                if (selectedCells.size == 0) {
                    return null
                }

                val cols = selectedCells.groupBy { p -> p.column }.entries.sortedBy { e -> e.key }.map { e -> e.value }
                val rows = selectedCells.groupBy { p -> p.row }.entries.sortedBy { e -> e.key }.map { e -> e.value }

                val numCols = cols.size
                val numRows = rows.size

                val firstCol = cols.first().first().column
                var currCol = firstCol
                // Ensure that the columns are increasing
                cols.drop(1).forEach { col ->
                    currCol++
                    if(col.size != numRows || currCol != col.first().column) {
                        return null
                    }
                }

                // Check the same thing for all the rows
                val firstRow = rows.first().first().row
                var currRow = firstRow
                rows.drop(1).forEach { row ->
                    currRow++
                    if(row.size != numCols || currRow != row.first().row) {
                        return null
                    }
                }

                return SelectedArea(firstCol, firstRow, numCols, numRows)
            }
        }
    }