Move the command line from cmd/bsdaily into internal/cli (closes #8)

cmd/bsdaily/main.go now only passes Version to cli.Main and exits with
the status it returns, as REPO_POLICIES.md requires of cmd/. The cobra
command, the flag rules and the date parsing moved unchanged into
internal/cli, so flags, help text, error messages, exit status and the
first log line stay as they were. The fallback to dev for an empty
version moved with them into cli.Main.

parseTargetDates is exported as ParseTargetDates so that a table test
outside the package can reach it; the test never touches the filesystem
or runs the extraction. README describes the new layout and TODO.md
records the step.

Model: opus-5-5
Co-authored-by: clawbot <sneak+clawbot@sneak.cloud>

cmd/bsdaily/main.go

@@ -3,21 +3,9 @@
 package main
 
 import (
-	"errors"
-	"fmt"
-	"log/slog"
 	"os"
-	"time"
 
-	"git.eeqj.de/sneak/bsdaily/internal/bsdaily"
-	"github.com/spf13/cobra"
-)
-
-var (
-	errDateExclusive  = errors.New("--date and --from/--to are mutually exclusive")
-	errFromRequiresTo = errors.New("--from requires --to")
-	errToRequiresFrom = errors.New("--to requires --from")
-	errFromAfterTo    = errors.New("is after --to")
+	"git.eeqj.de/sneak/bsdaily/internal/cli"
 )
 
 // Version is the git tag or short commit, set at link time with
@@ -28,111 +16,5 @@ var (
 var Version string
 
 func main() {
-	if Version == "" {
-		Version = "dev"
-	}
-
-	logger := slog.New(slog.NewTextHandler(os.Stderr, &slog.HandlerOptions{
-		Level: slog.LevelInfo,
-	}))
-	slog.SetDefault(logger)
-
-	var dateFlag, fromFlag, toFlag string
-
-	rootCmd := &cobra.Command{
-		Use:          "bsdaily",
-		Short:        "Extract a single day's data from the latest daily snapshot",
-		Version:      Version,
-		SilenceUsage: true,
-		RunE: func(_ *cobra.Command, _ []string) error {
-			slog.Info("starting", "version", Version)
-
-			targetDates, err := parseTargetDates(dateFlag, fromFlag, toFlag)
-			if err != nil {
-				return err
-			}
-
-			err = bsdaily.Run(targetDates)
-			if err != nil {
-				return err
-			}
-
-			slog.Info("completed successfully")
-
-			return nil
-		},
-	}
-
-	rootCmd.Flags().StringVarP(&dateFlag, "date", "d", "",
-		"target date to extract (YYYY-MM-DD); "+
-			"defaults to snapshot date minus one day")
-	rootCmd.Flags().StringVar(&fromFlag, "from", "",
-		"start of date range to extract (YYYY-MM-DD, inclusive); use with --to")
-	rootCmd.Flags().StringVar(&toFlag, "to", "",
-		"end of date range to extract (YYYY-MM-DD, inclusive); use with --from")
-
-	err := rootCmd.Execute()
-	if err != nil {
-		os.Exit(1)
-	}
-}
-
-// parseTargetDates turns the --date, --from and --to flags into the days
-// to extract. It returns nil when none of them is set, which Run takes
-// to mean the snapshot date minus one day.
-func parseTargetDates(dateFlag, fromFlag, toFlag string) ([]time.Time, error) {
-	hasDate := dateFlag != ""
-	hasFrom := fromFlag != ""
-	hasTo := toFlag != ""
-
-	// Validate mutual exclusivity
-	if hasDate && (hasFrom || hasTo) {
-		return nil, errDateExclusive
-	}
-
-	if hasFrom != hasTo {
-		if hasFrom {
-			return nil, errFromRequiresTo
-		}
-
-		return nil, errToRequiresFrom
-	}
-
-	if hasDate {
-		t, err := time.Parse("2006-01-02", dateFlag)
-		if err != nil {
-			return nil, fmt.Errorf(
-				"invalid --date %q (expected YYYY-MM-DD): %w", dateFlag, err)
-		}
-
-		return []time.Time{t}, nil
-	}
-
-	if !hasFrom {
-		return nil, nil
-	}
-
-	from, err := time.Parse("2006-01-02", fromFlag)
-	if err != nil {
-		return nil, fmt.Errorf(
-			"invalid --from %q (expected YYYY-MM-DD): %w", fromFlag, err)
-	}
-
-	to, err := time.Parse("2006-01-02", toFlag)
-	if err != nil {
-		return nil, fmt.Errorf(
-			"invalid --to %q (expected YYYY-MM-DD): %w", toFlag, err)
-	}
-
-	if from.After(to) {
-		return nil, fmt.Errorf("--from %s %w %s", fromFlag, errFromAfterTo, toFlag)
-	}
-
-	var targetDates []time.Time
-
-	for d := from; !d.After(to); d = d.AddDate(0, 0, 1) {
-		targetDates = append(targetDates, d)
-	}
-
-	return targetDates, nil
+	os.Exit(cli.Main(Version))
 }