dump.go

package binpack

import (
	"fmt"
	"os"
	"path/filepath"
)

// DumpFragments writes every sprite to dir as its own PNG, named after the key
// it would get in the map. Renaming a fragment and joining the directory again
// is what turns a numbered cut into a meaningful name.
func DumpFragments(dir string, sprites []Sprite) error {
	if err := os.MkdirAll(dir, 0o755); err != nil {
		return err
	}

	for _, s := range sprites {
		path := filepath.Join(dir, s.Name+".png")
		if err := SavePNG(path, s.Img); err != nil {
			return fmt.Errorf("dump %s: %w", s.Name, err)
		}
	}

	return nil
}

// CountPNGs reports how many PNGs sit directly in dir. A missing directory
// counts as zero.
func CountPNGs(dir string) (int, error) {
	entries, err := os.ReadDir(dir)
	if os.IsNotExist(err) {
		return 0, nil
	}
	if err != nil {
		return 0, err
	}

	n := 0
	for _, e := range entries {
		if !e.IsDir() && isPNG(e.Name()) {
			n++
		}
	}

	return n, nil
}

// CheckFragmentsDir rejects an output directory that holds any of the input
// files, which would scatter fragments among the sheets they were cut from and
// feed them back in on the next run.
func CheckFragmentsDir(dir string, files []string) error {
	target, err := filepath.Abs(dir)
	if err != nil {
		return err
	}

	for _, f := range files {
		abs, err := filepath.Abs(f)
		if err != nil {
			return err
		}
		if filepath.Dir(abs) == target {
			return fmt.Errorf(
				"-outFolder %s holds input %s: split into an empty directory instead",
				dir, f,
			)
		}
	}

	return nil
}