From 333b6dbc27b811c72216ac1f9483d40e8813b453 Mon Sep 17 00:00:00 2001
From: Laurence Withers <l@lwithers.me.uk>
Date: Sat, 13 May 2023 12:45:29 +0100
Subject: [PATCH] Improved printed of long lines

---
 display.go |   4 +--
 file.go    | 100 +++++++++++++++++++++++++++++++----------------------
 2 files changed, 61 insertions(+), 43 deletions(-)

diff --git a/display.go b/display.go
index f7b1d9e..ca52888 100644
--- a/display.go
+++ b/display.go
@@ -37,8 +37,8 @@ func (d *Display) TruncatedMarker() aurora.Value {
 	return d.a.Magenta("…")
 }
 
-func (d *Display) TruncatedBytes(byteCount int) aurora.Value {
-	return d.a.Faint(fmt.Sprintf("(%d bytes)", byteCount))
+func (d *Display) TruncatedChars(charCount int) aurora.Value {
+	return d.a.Faint(fmt.Sprintf("(%d chars)", charCount))
 }
 
 func (d *Display) BadUTF8Char() aurora.Value {
diff --git a/file.go b/file.go
index 4ef63cb..a3311d0 100644
--- a/file.go
+++ b/file.go
@@ -119,56 +119,73 @@ func file(path string, data []byte) {
 		b.Reset()
 		fmt.Fprintf(&b, "%4d: ", display.LineNumber(lineNum))
 
-		if loc[0] < 128 {
-			escape(&b, line[0:loc[0]])
-		} else {
-			start := loc[0] - 128
-			for i := 0; i < 5; i++ {
-				if utf8.RuneStart(line[start]) {
-					break
-				}
-				start++
-			}
-
-			b.WriteString(display.TruncatedBytes(start).String())
-			b.WriteString(display.TruncatedMarker().String())
-			escape(&b, line[start:loc[0]])
-		}
-
-		if loc[1]-loc[0] < 128 {
+		before := line[0:loc[0]]
+		matched := line[loc[0]:loc[1]]
+		after := line[loc[1]:]
+		if utf8.RuneCount(line) < longLine {
 			b2.Reset()
-			escape(&b2, line[loc[0]:loc[1]])
-			b.WriteString(display.Match(b2.String()).String())
+			escape(&b2, matched)
 
-			if loc[1]+128 > len(line) {
-				escape(&b, line[loc[1]:])
+			escape(&b, before)
+			b.WriteString(display.Match(b2.String()).String())
+			escape(&b, after)
+		} else {
+			n := utf8.RuneCount(before)
+			if n < 64 {
+				escape(&b, before)
 			} else {
-				end := loc[1] + 128
-				for i := 0; i < 5; i++ {
-					if utf8.RuneStart(line[end]) {
-						break
-					}
-					end--
+				var nbytes int
+				for i := 0; i < 64; i++ {
+					_, s := utf8.DecodeLastRune(before[:len(before)-nbytes])
+					nbytes += s
 				}
-				escape(&b, line[loc[1]:end])
-				b.WriteString(display.TruncatedBytes(len(line) - end).String())
+				b.WriteString(display.TruncatedChars(n - 64).String())
 				b.WriteString(display.TruncatedMarker().String())
+				escape(&b, before[len(before)-nbytes:])
 			}
 
-		} else {
-			end := loc[1]
-			for i := 0; i < 5; i++ {
-				if utf8.RuneStart(line[end]) {
-					break
+			n = utf8.RuneCount(matched)
+			if n < 64 {
+				b2.Reset()
+				escape(&b2, matched)
+				b.WriteString(display.Match(b2.String()).String())
+			} else {
+				var nbytes int
+				for i := 0; i < 32; i++ {
+					_, s := utf8.DecodeRune(matched[nbytes:])
+					nbytes += s
 				}
-				end--
+				b2.Reset()
+				escape(&b2, matched[:nbytes])
+				b.WriteString(display.Match(b2.String()).String())
+
+				b.WriteString(display.TruncatedMarker().String())
+				b.WriteString(display.TruncatedChars(n - 64).String())
+				b.WriteString(display.TruncatedMarker().String())
+
+				nbytes = 0
+				for i := 0; i < 32; i++ {
+					_, s := utf8.DecodeLastRune(matched[:len(matched)-nbytes])
+					nbytes += s
+				}
+				b2.Reset()
+				escape(&b2, matched[len(matched)-nbytes:])
+				b.WriteString(display.Match(b2.String()).String())
 			}
 
-			b2.Reset()
-			escape(&b2, line[loc[0]:end])
-			b.WriteString(display.Match(b2.String()).String())
-			b.WriteString(display.TruncatedMarker().String())
-			b.WriteString(display.TruncatedBytes(len(line) - end).String())
+			n = utf8.RuneCount(after)
+			if n < 64 {
+				escape(&b, after)
+			} else {
+				var nbytes int
+				for i := 0; i < 64; i++ {
+					_, s := utf8.DecodeRune(after[nbytes:])
+					nbytes += s
+				}
+				escape(&b, after[:nbytes])
+				b.WriteString(display.TruncatedMarker().String())
+				b.WriteString(display.TruncatedChars(n - 64).String())
+			}
 
 		}
 
@@ -202,8 +219,9 @@ func isBinary(data []byte) bool {
 	return false
 }
 
+const longLine = 256
+
 func isMinified(data []byte) bool {
-	const longLine = 256
 	bytesToExamine := 4096
 	var lineLength int