text: calculate rune widths better; fixes #78 (#79)

Gopkg.toml

@@ -29,6 +29,10 @@
   name = "github.com/stretchr/testify"
   version = "1.2.1"
 
+[[constraint]]
+  name = "github.com/mattn/go-runewidth"
+  version = "0.0.4"
+
 [prune]
   go-tests = true
   unused-packages = true

text/string.go

@@ -3,6 +3,8 @@ package text
 import (
 	"strings"
 	"unicode/utf8"
+
+	"github.com/mattn/go-runewidth"
 )
 
 // Constants
@@ -39,7 +41,7 @@ func InsertEveryN(str string, runeToInsert rune, n int) string {
 		}
 		out.WriteRune(c)
 		if !isEscSeq {
-			outLen++
+			outLen += RuneWidth(c)
 		}
 
 		if isEscSeq && c == EscapeStopRune {
@@ -68,11 +70,11 @@ func LongestLineLen(str string) int {
 			}
 			currLength = 0
 		} else if !isEscSeq {
-			currLength++
+			currLength += RuneWidth(c)
 		}
 	}
 	if currLength > maxLength {
-		return currLength
+		maxLength = currLength
 	}
 	return maxLength
 }
@@ -125,12 +127,24 @@ func RuneCount(str string) int {
 				isEscSeq = false
 			}
 		} else {
-			count++
+			count += RuneWidth(c)
 		}
 	}
 	return count
 }
 
+// RuneWidth returns the mostly accurate character-width of the rune. This is
+// not 100% accurate as the character width is usually dependant on the
+// typeface (font) used in the console/terminal. For ex.:
+//  RuneWidth('A') == 1
+//  RuneWidth('ツ') == 2
+//  RuneWidth('⊙') == 1
+//  RuneWidth('︿') == 2
+//  RuneWidth(0x27) == 0
+func RuneWidth(r rune) int {
+	return runewidth.RuneWidth(r)
+}
+
 // Snip returns the given string with a fixed length. For ex.:
 //  Snip("Ghost", 0, "~") == "Ghost"
 //  Snip("Ghost", 1, "~") == "~"

text/string_test.go

@@ -37,12 +37,14 @@ func ExampleInsertEveryN() {
 
 func TestInsertEveryN(t *testing.T) {
 	assert.Equal(t, "Ghost", InsertEveryN("Ghost", '-', 0))
+	assert.Equal(t, "Gツhツoツsツt", InsertEveryN("Ghost", 'ツ', 1))
 	assert.Equal(t, "G-h-o-s-t", InsertEveryN("Ghost", '-', 1))
 	assert.Equal(t, "Gh-os-t", InsertEveryN("Ghost", '-', 2))
 	assert.Equal(t, "Gho-st", InsertEveryN("Ghost", '-', 3))
 	assert.Equal(t, "Ghos-t", InsertEveryN("Ghost", '-', 4))
 	assert.Equal(t, "Ghost", InsertEveryN("Ghost", '-', 5))
 	assert.Equal(t, "\x1b[33mGhost\x1b[0m", InsertEveryN("\x1b[33mGhost\x1b[0m", '-', 0))
+	assert.Equal(t, "\x1b[33mGツhツoツsツt\x1b[0m", InsertEveryN("\x1b[33mGhost\x1b[0m", 'ツ', 1))
 	assert.Equal(t, "\x1b[33mG-h-o-s-t\x1b[0m", InsertEveryN("\x1b[33mGhost\x1b[0m", '-', 1))
 	assert.Equal(t, "\x1b[33mGh-os-t\x1b[0m", InsertEveryN("\x1b[33mGhost\x1b[0m", '-', 2))
 	assert.Equal(t, "\x1b[33mGho-st\x1b[0m", InsertEveryN("\x1b[33mGhost\x1b[0m", '-', 3))
@@ -54,13 +56,15 @@ func ExampleLongestLineLen() {
 	fmt.Printf("LongestLineLen(\"\"): %d\n", LongestLineLen(""))
 	fmt.Printf("LongestLineLen(\"\\n\\n\"): %d\n", LongestLineLen("\n\n"))
 	fmt.Printf("LongestLineLen(\"Ghost\"): %d\n", LongestLineLen("Ghost"))
+	fmt.Printf("LongestLineLen(\"Ghostツ\"): %d\n", LongestLineLen("Ghostツ"))
 	fmt.Printf("LongestLineLen(\"Winter\\nIs\\nComing\"): %d\n", LongestLineLen("Winter\nIs\nComing"))
 	fmt.Printf("LongestLineLen(\"Mother\\nOf\\nDragons\"): %d\n", LongestLineLen("Mother\nOf\nDragons"))
 	fmt.Printf("LongestLineLen(\"\\x1b[33mMother\\x1b[0m\\nOf\\nDragons\"): %d\n", LongestLineLen("\x1b[33mMother\x1b[0m\nOf\nDragons"))
 
 	// Output: LongestLineLen(""): 0
 	// LongestLineLen("\n\n"): 0
 	// LongestLineLen("Ghost"): 5
+	// LongestLineLen("Ghostツ"): 7
 	// LongestLineLen("Winter\nIs\nComing"): 6
 	// LongestLineLen("Mother\nOf\nDragons"): 7
 	// LongestLineLen("\x1b[33mMother\x1b[0m\nOf\nDragons"): 7
@@ -70,6 +74,7 @@ func TestLongestLineLen(t *testing.T) {
 	assert.Equal(t, 0, LongestLineLen(""))
 	assert.Equal(t, 0, LongestLineLen("\n\n"))
 	assert.Equal(t, 5, LongestLineLen("Ghost"))
+	assert.Equal(t, 7, LongestLineLen("Ghostツ"))
 	assert.Equal(t, 6, LongestLineLen("Winter\nIs\nComing"))
 	assert.Equal(t, 7, LongestLineLen("Mother\nOf\nDragons"))
 	assert.Equal(t, 7, LongestLineLen("\x1b[33mMother\x1b[0m\nOf\nDragons"))
@@ -125,22 +130,47 @@ func TestRepeatAndTrim(t *testing.T) {
 func ExampleRuneCount() {
 	fmt.Printf("RuneCount(\"\"): %d\n", RuneCount(""))
 	fmt.Printf("RuneCount(\"Ghost\"): %d\n", RuneCount("Ghost"))
+	fmt.Printf("RuneCount(\"Ghostツ\"): %d\n", RuneCount("Ghostツ"))
 	fmt.Printf("RuneCount(\"\\x1b[33mGhost\\x1b[0m\"): %d\n", RuneCount("\x1b[33mGhost\x1b[0m"))
 	fmt.Printf("RuneCount(\"\\x1b[33mGhost\\x1b[0\"): %d\n", RuneCount("\x1b[33mGhost\x1b[0"))
 
 	// Output: RuneCount(""): 0
 	// RuneCount("Ghost"): 5
+	// RuneCount("Ghostツ"): 7
 	// RuneCount("\x1b[33mGhost\x1b[0m"): 5
 	// RuneCount("\x1b[33mGhost\x1b[0"): 5
 }
 
 func TestRuneCount(t *testing.T) {
 	assert.Equal(t, 0, RuneCount(""))
 	assert.Equal(t, 5, RuneCount("Ghost"))
+	assert.Equal(t, 7, RuneCount("Ghostツ"))
 	assert.Equal(t, 5, RuneCount("\x1b[33mGhost\x1b[0m"))
 	assert.Equal(t, 5, RuneCount("\x1b[33mGhost\x1b[0"))
 }
 
+func ExampleRuneWidth() {
+	fmt.Printf("RuneWidth('A'): %d\n", RuneWidth('A'))
+	fmt.Printf("RuneWidth('ツ'): %d\n", RuneWidth('ツ'))
+	fmt.Printf("RuneWidth('⊙'): %d\n", RuneWidth('⊙'))
+	fmt.Printf("RuneWidth('︿'): %d\n", RuneWidth('︿'))
+	fmt.Printf("RuneWidth(rune(27)): %d\n", RuneWidth(rune(27))) // ANSI escape sequence
+
+	// Output: RuneWidth('A'): 1
+	// RuneWidth('ツ'): 2
+	// RuneWidth('⊙'): 1
+	// RuneWidth('︿'): 2
+	// RuneWidth(rune(27)): 0
+}
+
+func TestRuneWidth(t *testing.T) {
+	assert.Equal(t, 1, RuneWidth('A'))
+	assert.Equal(t, 2, RuneWidth('ツ'))
+	assert.Equal(t, 1, RuneWidth('⊙'))
+	assert.Equal(t, 2, RuneWidth('︿'))
+	assert.Equal(t, 0, RuneWidth(rune(27))) // ANSI escape sequence
+}
+
 func ExampleSnip() {
 	fmt.Printf("Snip(\"Ghost\", 0, \"~\"): %#v\n", Snip("Ghost", 0, "~"))
 	fmt.Printf("Snip(\"Ghost\", 1, \"~\"): %#v\n", Snip("Ghost", 1, "~"))