Open the report on last month

The report answered for the whole index, which is the one window a spending
report is least often asked for: last January's groceries sat in the same total
as last week's, and nothing on screen said which was which. It now opens on the
month that has just ended -- the last one a statement can be complete for --
and left/right step along an axis beside the totals, from all time down through
the named windows to the oldest month the index holds.

The period narrows the report and nothing else. reloadReport runs its own query
rather than reusing the rows the transaction list is showing: the two share the
account, the search and the untagged toggle, and differ only in the date
bounds, so opening on last month must not hide the rest of the index from the
list beside it. Nothing may put the period into m.filter, which is exactly what
would make it leak.

The windows are relative to today, never to the newest statement. "Last month"
with nothing in it reports nothing and says so, because silently answering for
a month nobody asked for is worse than an empty screen; an empty period and an
empty index therefore give different messages, one asking for another period
and the other for an import. The rolling windows run to the end of this month
rather than to the last complete one -- "last 3 months" is asked in order to
see what is happening now, and leaving out the days since the 1st answers a
question nobody put. The axis is built over the whole index rather than the
rows in view, or it would grow and shrink as the account or search filter
changed and move under the cursor; a reload rebuilds it, since an import can
reach further back, but keeps the window the user was on.

s cycles how those rows are arranged: largest out first as before, then in, net
lowest first so the biggest losses lead, count, and the tag A to Z. A letter
rather than a chord because the report is not a form. The marked heading says
which column the rows are read from and the help names what the key does next,
as the rule builder's preview already does. The sort rearranges rows and never
changes which rows there are, so the order stays out of the filter for the same
reason the period does. Currency remains the outer key under every order --
there are no rates here, so two currencies interleaved by amount would invite a
comparison that cannot be made -- and every order falls back to the tag, so
ties keep a fixed position instead of reshuffling between reloads.

money report takes the same choice as --sort out|in|net|count|tag, and a
misspelt one is refused rather than silently reporting in the default order. It
keeps --month and has no equivalent of the wider windows.

store.Filter gains From and To, compared as strings because dates are stored
ISO-8601 and a string comparison is therefore a date comparison. store.Months
replaces report.Months, which nothing had ever called: the axis needs the
months of the whole index, not of a slice already in hand.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

internal/report/report_test.go

@@ -1,6 +1,7 @@
 package report
 
 import (
+	"strings"
 	"testing"
 
 	"git.petrovv.com/nikola/money/internal/model"
@@ -27,7 +28,7 @@ func TestByTagLeavesTransferLegsOut(t *testing.T) {
 		leg(1, -50000, &id),
 		leg(2, 50000, &id),
 		{Currency: "EUR", MinorDigits: 2, AmountMinor: -2000, RuleTag: "groceries"},
-	})
+	}, OrderOut)
 
 	if len(rows) != 1 || rows[0].Tag != "groceries" {
 		t.Fatalf("rows = %+v, want only the groceries row", rows)
@@ -41,7 +42,7 @@ func TestByTagLeavesTransferLegsOut(t *testing.T) {
 // account and cannot be shown to have arrived must not quietly vanish from the
 // report.
 func TestByTagKeepsUnpairedLegs(t *testing.T) {
-	rows := ByTag([]model.Transaction{leg(1, -50000, nil)})
+	rows := ByTag([]model.Transaction{leg(1, -50000, nil)}, OrderOut)
 	if len(rows) != 1 || rows[0].Out != 50000 {
 		t.Fatalf("rows = %+v, want the unpaired leg counted", rows)
 	}
@@ -133,3 +134,133 @@ func TestExcludedClaimsNoFeeAcrossCurrencies(t *testing.T) {
 		}
 	}
 }
+
+// row is a transaction under one tag, for the ordering tests.
+func row(tag string, amount int64) model.Transaction {
+	return model.Transaction{Currency: "EUR", MinorDigits: 2, AmountMinor: amount, RuleTag: tag}
+}
+
+// tags is the order the breakdown came out in.
+func tags(rows []TagTotal) []string {
+	var out []string
+	for _, r := range rows {
+		out = append(out, r.Tag)
+	}
+	return out
+}
+
+func TestByTagOrders(t *testing.T) {
+	txns := []model.Transaction{
+		row("rent", -100000),
+		row("groceries", -2000),
+		row("groceries", -3000),
+		row("groceries", -1000),
+		row("salary", 250000),
+		row("refund", 500),
+		row("refund", -400),
+	}
+
+	for _, tc := range []struct {
+		order Order
+		want  []string
+	}{
+		{OrderOut, []string{"rent", "groceries", "refund", "salary"}},
+		{OrderIn, []string{"salary", "refund", "groceries", "rent"}},
+		{OrderNet, []string{"rent", "groceries", "refund", "salary"}},
+		{OrderCount, []string{"groceries", "refund", "rent", "salary"}},
+		{OrderTag, []string{"groceries", "refund", "rent", "salary"}},
+	} {
+		got := tags(ByTag(txns, tc.order))
+		if len(got) != len(tc.want) {
+			t.Errorf("%s: rows = %v, want %v", tc.order, got, tc.want)
+			continue
+		}
+		for i := range got {
+			if got[i] != tc.want[i] {
+				t.Errorf("%s: rows = %v, want %v", tc.order, got, tc.want)
+				break
+			}
+		}
+	}
+}
+
+// Every order falls back to the tag, so rows that tie do not shuffle about
+// between one reload and the next.
+func TestByTagTiesBreakOnTheTag(t *testing.T) {
+	txns := []model.Transaction{row("zebra", -1000), row("apple", -1000)}
+	for _, o := range Orders() {
+		if got := tags(ByTag(txns, o)); got[0] != "apple" {
+			t.Errorf("%s: rows = %v, want the tie broken on the tag", o, got)
+		}
+	}
+}
+
+// No order may interleave currencies: with no exchange rates here, two amounts
+// in different columns are not comparable and must not be sorted against each
+// other.
+func TestByTagNeverInterleavesCurrencies(t *testing.T) {
+	txns := []model.Transaction{
+		{Currency: "EUR", MinorDigits: 2, AmountMinor: -100, RuleTag: "small"},
+		{Currency: "BGN", MinorDigits: 2, AmountMinor: -900000, RuleTag: "huge"},
+		{Currency: "EUR", MinorDigits: 2, AmountMinor: -200, RuleTag: "medium"},
+	}
+	for _, o := range Orders() {
+		rows := ByTag(txns, o)
+		if rows[0].Currency != "BGN" || rows[1].Currency != "EUR" || rows[2].Currency != "EUR" {
+			t.Errorf("%s: currencies = %+v, want them grouped", o, rows)
+		}
+	}
+}
+
+// The cycle visits every order and comes back to where it started.
+func TestOrderNextCycles(t *testing.T) {
+	seen := map[Order]bool{}
+	o := OrderOut
+	for range len(Orders()) {
+		if seen[o] {
+			t.Fatalf("order %s came round twice in one cycle", o)
+		}
+		seen[o] = true
+		o = o.Next()
+	}
+	if o != OrderOut {
+		t.Errorf("the cycle ended on %s, want it back at %s", o, OrderOut)
+	}
+}
+
+// A misspelt --sort is refused rather than silently reporting in the default
+// order, and the error names what it would have accepted.
+func TestParseOrder(t *testing.T) {
+	for _, o := range Orders() {
+		got, err := ParseOrder(o.String())
+		if err != nil || got != o {
+			t.Errorf("ParseOrder(%q) = %s, %v, want %s", o.String(), got, err, o)
+		}
+	}
+	_, err := ParseOrder("descending")
+	if err == nil {
+		t.Fatal("ParseOrder accepted a name that is not an order")
+	}
+	for _, want := range []string{"descending", "out", "tag"} {
+		if !strings.Contains(err.Error(), want) {
+			t.Errorf("error %q does not mention %q", err, want)
+		}
+	}
+}
+
+// Each order marks a different column, and only headings the table actually
+// has, or the marker would land nowhere.
+func TestOrderColumnsAreDistinct(t *testing.T) {
+	headings := map[string]bool{"Tag": true, "Cur": true, "Out": true, "In": true, "Net": true, "N": true}
+	seen := map[string]bool{}
+	for _, o := range Orders() {
+		c := o.Column()
+		if !headings[c] {
+			t.Errorf("%s sorts on %q, which is not a report column", o, c)
+		}
+		if seen[c] {
+			t.Errorf("%s marks %q, which another order already marks", o, c)
+		}
+		seen[c] = true
+	}
+}