/**
 * Stage one: the inputs a business user owns. The policy assumptions and,
 * below them, the journal rule source — which event posts which metric.
 * Both are plain cells, editable in the viewer.
 */
private Workbook policy() {
	Workbook wb = Workbook.create();
	Sheet sheet = wb.createSheet(POLICY);
	title(sheet, 0, "Policy assumptions · edit any value, then run the next stage");
	header(sheet, 1, "Assumption", "Value", "Notes");
	for (int i = 0; i < ASSUMPTIONS.length; i++) {
		row(sheet, 2 + i, ASSUMPTIONS[i]);
	}
	sheet.range(2, 0, 7, 0).setStyle(fill(IDENTITY, true));
	sheet.range(2, 1, 3, 1).setStyle(fill(IDENTITY, false));
	sheet.range(4, 1, 6, 1).setStyle(fill(IDENTITY, false, "#,##0"));
	sheet.range(7, 1, 7, 1).setStyle(fill(IDENTITY, false, "0.00"));

	title(sheet, RULE_TITLE_ROW, "Journal rule source · metrics are named, see the Metrics sheet");
	header(sheet, RULE_HEADER_ROW, "Event", "Description", "Debit metric", "Credit metric");
	for (int i = 0; i < JOURNAL_RULES.length; i++) {
		row(sheet, RULE_HEADER_ROW + 1 + i, (Object[]) JOURNAL_RULES[i]);
	}
	sheet.range(RULE_HEADER_ROW + 1, 0, RULE_HEADER_ROW + JOURNAL_RULES.length, 3)
			.setStyle(fill(RULE, false));

	sheet.setColumnWidth(0, 26);
	sheet.setColumnWidth(1, 46);
	sheet.setColumnWidth(2, 26);
	sheet.setColumnWidth(3, 26);
	return wb;
}