cmd(lectio-ef-dump): new EF calendar dumper for colitur's differential oracle

Prints one line per day, sorted ascending, for a civil-year range: date,
weekday, season, week, observed slug, rank, colour, then zero or more
+slug tokens for the day's other (losing) candidates. The line format
matches colitur's `colitur day` output field-for-field so the two
streams diff directly; every column carries lectio's own vocabulary
(season names, slugs, rank/colour spellings) with no translation toward
colitur's — that mapping belongs to the differential comparator, not
this dumper.

Uses calendar.Compute with Selection{Form: "old"} over the embedded
tridentine layer (caldata.Tridentine()), mirroring the setup already
used by oracle_ef_test.go. Lives in cmd/ because internal/calendar
cannot be imported outside this module; colitur's build is untouched.

Note for the comparator: lectio has no RG 111 commemoration-admission
logic, so the trailing +slug tokens are the day's losing candidates,
not admitted commemorations.

1 files changed, 106 insertions, 0 deletions

diff --git a/cmd/lectio-ef-dump/main.go b/cmd/lectio-ef-dump/main.go
new file mode 100644
index 0000000..08ff547
--- /dev/null
+++ b/cmd/lectio-ef-dump/main.go
@@ -0,0 +1,106 @@
+// Command lectio-ef-dump prints lectio's Extraordinary Form (1962) calendar,
+// one line per day, for use as colitur's differential oracle.
+//
+// Output format matches colitur's `colitur day <year>` line for line (see
+// colitur's bin/main.ml, day_line), so the two streams are diffable directly:
+//
+//	YYYY-MM-DD weekday season week slug rank colour [+other-slug]...
+//
+// Every column carries lectio's OWN vocabulary (season names, slugs, rank and
+// colour spellings) -- this dumper does not translate lectio's values into
+// colitur's. The mapping between the two vocabularies is the differential
+// comparator's job, not this dumper's; translating here would hide real
+// divergences behind an already-reconciled view.
+//
+// The trailing "+other-slug" tokens are lectio's Others: the sanctoral
+// candidates that lost the day's precedence contest. lectio has no RG 111
+// commemoration-admission logic, so this is the set of losing candidates, not
+// the set of admitted commemorations -- the two are different things. See the
+// task report for detail; the comparator does not diff this column.
+//
+// Usage: lectio-ef-dump <from-year> <to-year>
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"os"
+	"strconv"
+	"strings"
+	"time"
+
+	"github.com/lukaszkasprzak/lectio/internal/caldata"
+	"github.com/lukaszkasprzak/lectio/internal/calendar"
+)
+
+func main() {
+	os.Exit(run(os.Args[1:], os.Stdout, os.Stderr))
+}
+
+// run is lectio-ef-dump's testable entry point: parse args, compute, and
+// write. Returns a process exit code (0 ok, 1 runtime error, 2 usage error).
+func run(args []string, stdout, stderr io.Writer) int {
+	if len(args) != 2 {
+		fmt.Fprintln(stderr, "usage: lectio-ef-dump <from-year> <to-year>")
+		return 2
+	}
+	from, errFrom := strconv.Atoi(args[0])
+	to, errTo := strconv.Atoi(args[1])
+	if errFrom != nil || errTo != nil {
+		fmt.Fprintln(stderr, "lectio-ef-dump: from-year and to-year must be integers")
+		return 2
+	}
+	if from > to {
+		fmt.Fprintf(stderr, "lectio-ef-dump: from-year %d is after to-year %d\n", from, to)
+		return 2
+	}
+
+	sel := calendar.DefaultSelection()
+	sel.Form = "old"
+	layers := []calendar.Layer{caldata.Tridentine()}
+
+	w := bufio.NewWriter(stdout)
+	for y := from; y <= to; y++ {
+		start := time.Date(y, time.January, 1, 0, 0, 0, 0, time.UTC)
+		end := time.Date(y, time.December, 31, 0, 0, 0, 0, time.UTC)
+		for d := start; !d.After(end); d = d.AddDate(0, 0, 1) {
+			day := calendar.Compute(d, sel, layers)
+			if _, err := w.WriteString(dumpLine(day)); err != nil {
+				fmt.Fprintf(stderr, "lectio-ef-dump: %v\n", err)
+				return 1
+			}
+		}
+	}
+	if err := w.Flush(); err != nil {
+		fmt.Fprintf(stderr, "lectio-ef-dump: %v\n", err)
+		return 1
+	}
+	return 0
+}
+
+// dumpLine renders one LiturgicalDay as a colitur-format line. Week is
+// lectio's own int (0 where no season week applies, e.g. named I class feasts
+// and per annum green-season ferias); printed as "-" there so the field count
+// stays fixed, matching colitur's own convention for an absent week.
+func dumpLine(day calendar.LiturgicalDay) string {
+	week := "-"
+	if day.Week != 0 {
+		week = strconv.Itoa(day.Week)
+	}
+	var b strings.Builder
+	fmt.Fprintf(&b, "%s %s %s %s %s %s %s",
+		day.Date.Format("2006-01-02"),
+		strings.ToLower(day.Weekday.String()),
+		string(day.Season),
+		week,
+		day.Observed.Slug,
+		string(day.Observed.Rank),
+		string(day.Colour),
+	)
+	for _, o := range day.Others {
+		fmt.Fprintf(&b, " +%s", o.Slug)
+	}
+	b.WriteByte('\n')
+	return b.String()
+}