// Command sfdupes quickly identifies candidate duplicate files across
// very large filesystems without reading full file contents. Files are
// considered duplicates when they have identical size, identical SHA-256
// of their first 1024 bytes, and identical SHA-256 of their last 1024
// bytes.
//
// Usage:
//
//	sfdupes scan [--workers N] [-x] PATH... > files.dat
//	sfdupes report [files.dat|-] > dupes.tsv
//	sfdupes trees [files.dat|-] > dupetrees.tsv
//
// See README.md for the complete specification.
package main

import (
	"fmt"
	"os"
	"runtime"

	"github.com/spf13/cobra"
)

// Exit codes: 0 is success (even with per-file warnings), exitFatal is
// a fatal error, exitUsage is a usage error.
const (
	exitFatal = 1
	exitUsage = 2
)

// Version is the build version, injected at link time via -ldflags
// (see the Makefile); "dev" for a plain go build.
//
//nolint:gochecknoglobals // written only by the linker
var Version = "dev"

func main() {
	root := &cobra.Command{
		Use:     "sfdupes",
		Short:   "Find candidate duplicate files by size and head/tail SHA-256",
		Version: Version,
		Args:    cobra.NoArgs,
		Run: func(cmd *cobra.Command, _ []string) {
			// A missing subcommand prints usage and exits 2.
			_ = cmd.Usage()

			os.Exit(exitUsage)
		},
	}
	// Everything on stdout is machine-readable data; all human-facing
	// output (help, usage, errors) goes to stderr.
	root.SetOut(os.Stderr)
	root.SetErr(os.Stderr)
	root.CompletionOptions.DisableDefaultCmd = true

	var (
		scanWorkers int
		scanOneFS   bool
	)

	scanCmd := &cobra.Command{
		Use:   "scan [--workers N] [-x] PATH...",
		Short: "Walk trees and emit one record per regular file on stdout",
		Args:  cobra.MinimumNArgs(1),
		Run: func(_ *cobra.Command, args []string) {
			runScan(args, scanWorkers, scanOneFS)
		},
	}
	scanCmd.Flags().IntVar(&scanWorkers, "workers", runtime.NumCPU(),
		"concurrent workers for the stat and hash passes")
	scanCmd.Flags().BoolVarP(&scanOneFS, "one-file-system", "x", false,
		"do not cross filesystem boundaries")

	reportCmd := &cobra.Command{
		Use:   "report [files.dat|-]",
		Short: "Read a scan stream and print the file-level duplicates report",
		Args:  cobra.MaximumNArgs(1),
		Run: func(_ *cobra.Command, args []string) {
			runReport(args)
		},
	}

	treesCmd := &cobra.Command{
		Use:   "trees [files.dat|-]",
		Short: "Read a scan stream and print the duplicate-tree report",
		Args:  cobra.MaximumNArgs(1),
		Run: func(_ *cobra.Command, args []string) {
			runTrees(args)
		},
	}

	root.AddCommand(scanCmd, reportCmd, treesCmd)

	err := root.Execute()
	if err != nil {
		// Cobra has already printed the error and usage to stderr;
		// an invalid subcommand or bad arguments is a usage error.
		os.Exit(exitUsage)
	}
}

// fatalf reports a fatal error and exits 1.
func fatalf(format string, args ...any) {
	fmt.Fprintf(os.Stderr, "sfdupes: "+format+"\n", args...)
	os.Exit(exitFatal)
}