Consolidate CLI report date policy

internal/cli/report_date.go

@@ -0,0 +1,75 @@
+package cli
+
+import (
+	"errors"
+	"fmt"
+	"time"
+
+	"gitea.maximumdirect.net/eric/weatherreporter/internal/app"
+	"gitea.maximumdirect.net/eric/weatherreporter/internal/timeutil"
+)
+
+var (
+	errReportDateRequired    = errors.New("report date is required")
+	errReportDateNotAccepted = errors.New("report does not accept a date")
+)
+
+type reportDatePolicy struct {
+	acceptsDate         bool
+	requiresDate        bool
+	defaultsToLocalDate bool
+}
+
+func reportDatePolicyFor(report app.ReportKind) reportDatePolicy {
+	switch report {
+	case app.ReportDaily:
+		return reportDatePolicy{acceptsDate: true, requiresDate: true}
+	case app.ReportToday:
+		return reportDatePolicy{acceptsDate: true, defaultsToLocalDate: true}
+	default:
+		return reportDatePolicy{}
+	}
+}
+
+func addReportDateFlag(fs interface {
+	StringVar(*string, string, string, string)
+}, report app.ReportKind, value *string) {
+	if reportDatePolicyFor(report).acceptsDate {
+		fs.StringVar(value, "date", "", "report date in YYYY-MM-DD")
+	}
+}
+
+func reportDateRequiredError(action string, report app.ReportKind, value string) error {
+	if reportDatePolicyFor(report).requiresDate && value == "" {
+		return fmt.Errorf("%s %s requires --date YYYY-MM-DD", action, report)
+	}
+	return nil
+}
+
+func resolveActionReportDate(action string, report app.ReportKind, value string, location *time.Location, now time.Time) (time.Time, error) {
+	date, err := resolveReportDate(report, value, location, now)
+	if errors.Is(err, errReportDateRequired) {
+		return time.Time{}, fmt.Errorf("%s %s requires --date YYYY-MM-DD", action, report)
+	}
+	return date, err
+}
+
+func resolveReportDate(report app.ReportKind, value string, location *time.Location, now time.Time) (time.Time, error) {
+	policy := reportDatePolicyFor(report)
+	if !policy.acceptsDate {
+		if value != "" {
+			return time.Time{}, errReportDateNotAccepted
+		}
+		return time.Time{}, nil
+	}
+	if value == "" {
+		if policy.requiresDate {
+			return time.Time{}, errReportDateRequired
+		}
+		if policy.defaultsToLocalDate {
+			return timeutil.LocalDate(now, location), nil
+		}
+		return time.Time{}, nil
+	}
+	return timeutil.ParseLocalDate(value, location)
+}