Added function for error reporting

Author: shellyln

base/types.go

@@ -26,6 +26,15 @@ type SourcePosition struct {
 	Length int `json:"len,omitempty"`
 }
 
+// Source position (for error reporting)
+type LineAndColPosition struct {
+	LineIndex int
+	Line      int
+	Col       int
+	Position  int
+	ErrSource string
+}
+
 // Match result status
 type MatchStatusType int
 

base/util.go

@@ -0,0 +1,68 @@
+package parser
+
+import (
+	"strings"
+)
+
+//
+func GetLineAndColPosition(src string, pos SourcePosition) LineAndColPosition {
+	prevLineIndex := 0
+	lineIndex := 0
+	line := 1
+	col := 1
+
+	for i := 0; i < pos.Position; i++ {
+		switch src[i] {
+		case '\r':
+			line++
+			if i+1 < pos.Position && src[i+1] == '\n' {
+				i++
+			}
+			prevLineIndex = lineIndex
+			lineIndex = i + 1
+			col = 1
+		case '\n':
+			line++
+			prevLineIndex = lineIndex
+			lineIndex = i + 1
+			col = 1
+		default:
+			col++
+		}
+	}
+
+	srcLen := len(src)
+	endIndex := pos.Position
+OUTER:
+	for i := pos.Position; i < srcLen; i++ {
+		switch src[i] {
+		case '\r', '\n':
+			break OUTER
+		default:
+			endIndex++
+		}
+	}
+
+	errGuideCol := col - 1
+	if errGuideCol < 0 {
+		errGuideCol = 0
+	}
+
+	errSource := src[prevLineIndex:endIndex]
+	if strings.Contains(errSource, "\n") {
+		errSource = "   | " + strings.Replace(errSource, "\n", "\n > | ", 1) + "\n"
+	} else if strings.Contains(errSource, "\r") {
+		errSource = "   | " + strings.Replace(errSource, "\r", "\r > | ", 1) + "\r"
+	} else {
+		errSource = " > | " + errSource + "\n"
+	}
+	errSource += "   | " + strings.Repeat(" ", errGuideCol) + "^^^^"
+
+	return LineAndColPosition{
+		LineIndex: lineIndex,
+		Line:      line,
+		Col:       col,
+		Position:  pos.Position,
+		ErrSource: errSource,
+	}
+}