Hw02 unpack string

hw02_unpack_string/go.mod

@@ -5,6 +5,5 @@ go 1.16
 require (
 	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/stretchr/testify v1.7.0
-	gopkg.in/yaml.v2 v2.4.0 // indirect
 	gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b // indirect
 )

hw02_unpack_string/unpack.go

@@ -2,11 +2,95 @@ package hw02unpackstring
 
 import (
 	"errors"
+	"strconv"
+	"strings"
+	"unicode"
 )
 
 var ErrInvalidString = errors.New("invalid string")
 
-func Unpack(_ string) (string, error) {
-	// Place your code here.
-	return "", nil
+func Unpack(v string) (string, error) {
+	if v == "" {
+		return "", nil
+	}
+
+	var baffle, number bool
+	result := &strings.Builder{}
+	smbRep := &strings.Builder{}
+
+	if unicode.IsDigit(rune(v[0])) {
+		return "", ErrInvalidString
+	}
+
+	for _, currRune := range v {
+		if err := check(&baffle, &number, currRune, result, smbRep); err != nil {
+			return "", err
+		}
+	}
+
+	if baffle {
+		return result.String(), ErrInvalidString
+	}
+
+	result.WriteString(smbRep.String())
+	return result.String(), nil
+}
+
+func check(baffle, number *bool, currRune rune, result, smbRep *strings.Builder) error {
+	if currRune == '\\' {
+		*number = false
+		if *baffle {
+			if smbRep.Len() == 0 {
+				smbRep.WriteRune('\\')
+				*baffle = false
+				return nil
+			}
+			result.WriteString(smbRep.String())
+			smbRep.Reset()
+			return nil
+		}
+		*baffle = true
+		return nil
+	}
+
+	if num, err := strconv.Atoi(string(currRune)); err == nil {
+		if *number {
+			return ErrInvalidString
+		}
+
+		if *baffle {
+			smbRep.WriteRune(currRune)
+			*baffle = false
+			return nil
+		}
+
+		*number = true
+		if smbRep.Len() == 0 {
+			buf := result.String()
+			result.Reset()
+			result.WriteString(buf[:len(buf)-1])
+			smbRep.WriteRune(rune(buf[len(buf)-1]))
+		}
+
+		*baffle = false
+		if num != 0 {
+			result.WriteString(strings.Repeat(smbRep.String(), num))
+		}
+		smbRep.Reset()
+		return nil
+	}
+
+	if *baffle {
+		if smbRep.Len() == 0 {
+			smbRep.WriteRune('\\')
+			*baffle = false
+		}
+
+		smbRep.WriteRune(currRune)
+		return nil
+	}
+
+	result.WriteRune(currRune)
+	*number = false
+	return nil
 }

hw02_unpack_string/unpack_test.go

@@ -17,16 +17,18 @@ func TestUnpack(t *testing.T) {
 		{input: "", expected: ""},
 		{input: "aaa0b", expected: "aab"},
 		// uncomment if task with asterisk completed
-		// {input: `qwe\4\5`, expected: `qwe45`},
-		// {input: `qwe\45`, expected: `qwe44444`},
-		// {input: `qwe\\5`, expected: `qwe\\\\\`},
-		// {input: `qwe\\\3`, expected: `qwe\3`},
+		{input: `qwe\4\5`, expected: `qwe45`},
+		{input: `qwe\45`, expected: `qwe44444`},
+		{input: `qwe\\5`, expected: `qwe\\\\\`},
+		{input: `qwe\\\3`, expected: `qwe\3`},
+		{input: `d\n5abc`, expected: `d\n\n\n\n\nabc`},
 	}
 
 	for _, tc := range tests {
 		tc := tc
 		t.Run(tc.input, func(t *testing.T) {
 			result, err := Unpack(tc.input)
+			t.Log(result, err)
 			require.NoError(t, err)
 			require.Equal(t, tc.expected, result)
 		})