main: refactor a bit to get logic out of main and into ./cmd/

Signed-off-by: Vincent Batts <vbatts@hashbangbash.com>

cmd/coreutils.go

@@ -0,0 +1,61 @@
+package cmd
+
+import (
+	"bufio"
+	"encoding/hex"
+	"errors"
+	"fmt"
+	"io"
+	"os"
+	"strings"
+
+	"github.com/kyokomi/emoji"
+)
+
+/*
+ParseCoreUtils expects some input like:
+```shell
+$ sha256sum ./tmp.efLuko
+f18bd8b680e834ab8097a66deb0255821195d9624e39da6b65903ff6a09a01bb  ./tmp.efLuko
+```
+*/
+func ParseCoreUtils(line string) (filename string, sum []byte, err error) {
+	chunks := strings.SplitN(strings.TrimRight(line, "\n"), "  ", 2)
+	if len(chunks) != 2 {
+		return "", nil, ErrNotCoreUtilsLine
+	}
+	sum, err = hex.DecodeString(chunks[0])
+	if err != nil {
+		return "", nil, err
+	}
+	return chunks[1], sum, nil
+}
+
+// ErrNotCoreUtilsLine when the line to parse is not formated like a coreutils checksum line
+var ErrNotCoreUtilsLine = errors.New("not a coreutils checksum line")
+
+// PrintCoreUtils reads in the content like from `sha25sum ...` and returns
+// in likeness but with emojisum instead.
+// TODO(vb) return a buffer that the caller can choose to print out themselves
+func PrintCoreUtils(rdr io.Reader) error {
+	buf := bufio.NewReader(rdr)
+	for {
+		line, err := buf.ReadString('\n')
+		if err != nil && err == io.EOF {
+			break
+		} else if err != nil {
+			return err
+		}
+		name, sum, err := ParseCoreUtils(line)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "%s: %q\n", err, line)
+			continue
+		}
+		str := EmojiFromBytes(sum)
+		fmt.Printf("%x  %s\n", sum, name)
+		fmt.Printf("%s  %s\n", str, name)
+		emoji.Print(str)
+		fmt.Printf("  %s\n", name)
+	}
+	return nil
+}