Error handling

calendar.go

@@ -456,10 +456,10 @@ func ParseCalendar(r io.Reader) (*Calendar, error) {
 		}
 		line, err := ParseProperty(*l)
 		if err != nil {
-			return nil, fmt.Errorf("parsing line %d: %w", ln, err)
+			return nil, fmt.Errorf("%s %d: %w", ParsingLineError, ln, err)
 		}
 		if line == nil {
-			return nil, fmt.Errorf("parsing calendar line %d", ln)
+			return nil, fmt.Errorf("%s %d", ParsingCalendarLineError, ln)
 		}
 		switch state {
 		case "begin":
@@ -469,10 +469,10 @@ func ParseCalendar(r io.Reader) (*Calendar, error) {
 				case "VCALENDAR":
 					state = "properties"
 				default:
-					return nil, errors.New("malformed calendar; expected a vcalendar")
+					return nil, errors.New(MalformedCalendarExpectedVCalendarError)
 				}
 			default:
-				return nil, errors.New("malformed calendar; expected begin")
+				return nil, errors.New(MalformedCalendarExpectedBeginError)
 			}
 		case "properties":
 			switch line.IANAToken {
@@ -481,7 +481,7 @@ func ParseCalendar(r io.Reader) (*Calendar, error) {
 				case "VCALENDAR":
 					state = "end"
 				default:
-					return nil, errors.New("malformed calendar; expected end")
+					return nil, errors.New(MalformedCalendarExpectedEndError)
 				}
 			case "BEGIN":
 				state = "components"
@@ -499,7 +499,7 @@ func ParseCalendar(r io.Reader) (*Calendar, error) {
 				case "VCALENDAR":
 					state = "end"
 				default:
-					return nil, errors.New("malformed calendar; expected end")
+					return nil, errors.New(MalformedCalendarExpectedEndError)
 				}
 			case "BEGIN":
 				co, err := GeneralParseComponent(cs, line)
@@ -510,12 +510,12 @@ func ParseCalendar(r io.Reader) (*Calendar, error) {
 					c.Components = append(c.Components, co)
 				}
 			default:
-				return nil, errors.New("malformed calendar; expected begin or end")
+				return nil, errors.New(MalformedCalendarExpectedBeginOrEndError)
 			}
 		case "end":
-			return nil, errors.New("malformed calendar; unexpected end")
+			return nil, errors.New(MalformedCalendarUnexpectedEndError)
 		default:
-			return nil, errors.New("malformed calendar; bad state")
+			return nil, errors.New(MalformedCalendarBadStateError)
 		}
 	}
 	return c, nil

components.go

@@ -156,19 +156,19 @@ func (event *VEvent) SetDuration(d time.Duration) error {
 			return nil
 		}
 	}
-	return errors.New("start or end not yet defined")
+	return errors.New(StartOrEndNotYetDefinedError)
 }
 
 func (event *VEvent) getTimeProp(componentProperty ComponentProperty, expectAllDay bool) (time.Time, error) {
 	timeProp := event.GetProperty(componentProperty)
 	if timeProp == nil {
-		return time.Time{}, errors.New("property not found")
+		return time.Time{}, errors.New(PropertyNotFoundError)
 	}
 
 	timeVal := timeProp.BaseProperty.Value
 	matched := timeStampVariations.FindStringSubmatch(timeVal)
 	if matched == nil {
-		return time.Time{}, fmt.Errorf("time value not matched, got '%s'", timeVal)
+		return time.Time{}, fmt.Errorf("%s, got '%s'", TimeValueNotMatchedError, timeVal)
 	}
 	tOrZGrp := matched[2]
 	zGrp := matched[4]
@@ -179,7 +179,7 @@ func (event *VEvent) getTimeProp(componentProperty ComponentProperty, expectAllD
 	var propLoc *time.Location
 	if tzIdOk {
 		if len(tzId) != 1 {
-			return time.Time{}, errors.New("expected only one TZID")
+			return time.Time{}, errors.New(ExpectedOneTZIDError)
 		}
 		var tzErr error
 		propLoc, tzErr = time.LoadLocation(tzId[0])
@@ -202,7 +202,7 @@ func (event *VEvent) getTimeProp(componentProperty ComponentProperty, expectAllD
 			}
 		}
 
-		return time.Time{}, fmt.Errorf("time value matched but unsupported all-day timestamp, got '%s'", timeVal)
+		return time.Time{}, fmt.Errorf("%s, got '%s'", TimeValueMatchedButUnsupportedAllDayTimeStampError, timeVal)
 	}
 
 	if grp1len > 0 && grp3len > 0 && tOrZGrp == "T" && zGrp == "Z" {
@@ -223,7 +223,7 @@ func (event *VEvent) getTimeProp(componentProperty ComponentProperty, expectAllD
 		}
 	}
 
-	return time.Time{}, fmt.Errorf("time value matched but not supported, got '%s'", timeVal)
+	return time.Time{}, fmt.Errorf("%s, got '%s'", TimeValueMatchedButNotSupportedError, timeVal)
 }
 
 func (event *VEvent) GetStartAt() (time.Time, error) {
@@ -519,7 +519,7 @@ func GeneralParseComponent(cs *CalendarStream, startLine *BaseProperty) (Compone
 	var co Component
 	switch startLine.Value {
 	case "VCALENDAR":
-		return nil, errors.New("malformed calendar; vcalendar not where expected")
+		return nil, errors.New(MalformedCalendarVCalendarNotWhereExpectedError)
 	case "VEVENT":
 		co = ParseVEvent(cs, startLine)
 	case "VTODO":
@@ -660,18 +660,18 @@ func ParseComponent(cs *CalendarStream, startLine *BaseProperty) (ComponentBase,
 		}
 		line, err := ParseProperty(*l)
 		if err != nil {
-			return cb, fmt.Errorf("parsing component property %d: %w", ln, err)
+			return cb, fmt.Errorf("%s %d: %w", ParsingComponentPropertyError, ln, err)
 		}
 		if line == nil {
-			return cb, errors.New("parsing component line")
+			return cb, errors.New(ParsingComponentLineError)
 		}
 		switch line.IANAToken {
 		case "END":
 			switch line.Value {
 			case startLine.Value:
 				return cb, nil
 			default:
-				return cb, errors.New("unbalanced end")
+				return cb, errors.New(UnbalancedEndError)
 			}
 		case "BEGIN":
 			co, err := GeneralParseComponent(cs, line)
@@ -685,5 +685,5 @@ func ParseComponent(cs *CalendarStream, startLine *BaseProperty) (ComponentBase,
 			cb.Properties = append(cb.Properties, IANAProperty{*line})
 		}
 	}
-	return cb, errors.New("ran out of lines")
+	return cb, errors.New(OutOfLinesError)
 }

errors.go

@@ -0,0 +1,35 @@
+package ics
+
+const (
+	MalformedCalendarExpectedVCalendarError  = "malformed calendar; expected a vcalendar"
+	MalformedCalendarExpectedBeginError      = "malformed calendar; expected begin"
+	MalformedCalendarExpectedEndError        = "malformed calendar; expected a end"
+	MalformedCalendarExpectedBeginOrEndError = "malformed calendar; expected begin or end"
+
+	MalformedCalendarUnexpectedEndError             = "malformed calendar; unexpected end"
+	MalformedCalendarBadStateError                  = "malformed calendar; bad state"
+	MalformedCalendarVCalendarNotWhereExpectedError = "malformed calendar; vcalendar not where expected"
+
+	StartOrEndNotYetDefinedError = "start or end not yet defined"
+	PropertyNotFoundError        = "property not found"
+	ExpectedOneTZIDError         = "expected one TZID"
+
+	TimeValueNotMatchedError                           = "time value not matched"
+	TimeValueMatchedButUnsupportedAllDayTimeStampError = "time value matched but unsupported all-day timestamp"
+	TimeValueMatchedButNotSupportedError               = "time value matched but not supported"
+
+	ParsingComponentPropertyError = "parsing component property"
+	ParsingComponentLineError     = "parsing component line"
+	ParsingLineError              = "parsing line"
+	ParsingCalendarLineError      = "parsing calendar line"
+	ParsingPropertyError          = "parsing property"
+	ParseError                    = "parse error"
+
+	MissingPropertyValueError = "missing property value"
+
+	UnexpectedASCIICharError                       = "unexpected char ascii"
+	UnexpectedDoubleQuoteInPropertyParamValueError = "unexpected double quote in property param value"
+
+	UnbalancedEndError = "unbalanced end"
+	OutOfLinesError    = "ran out of lines"
+)

property.go

@@ -2,6 +2,7 @@ package ics
 
 import (
 	"bytes"
+	"errors"
 	"fmt"
 	"io"
 	"log"
@@ -174,7 +175,7 @@ func ParseProperty(contentLine ContentLine) (*BaseProperty, error) {
 			t := r.IANAToken
 			r, np, err = parsePropertyParam(r, string(contentLine), p+1)
 			if err != nil {
-				return nil, fmt.Errorf("parsing property %s: %w", t, err)
+				return nil, fmt.Errorf("%s %s: %w", ParsingPropertyError, t, err)
 			}
 			if r == nil {
 				return nil, nil
@@ -198,7 +199,7 @@ func parsePropertyParam(r *BaseProperty, contentLine string, p int) (*BaseProper
 	case '=':
 		p += 1
 	default:
-		return nil, p, fmt.Errorf("missing property value for %s in %s", k, r.IANAToken)
+		return nil, p, fmt.Errorf("%s for %s in %s", MissingPropertyValueError, k, r.IANAToken)
 	}
 	for {
 		if p >= len(contentLine) {
@@ -207,7 +208,7 @@ func parsePropertyParam(r *BaseProperty, contentLine string, p int) (*BaseProper
 		var err error
 		v, p, err = parsePropertyParamValue(contentLine, p)
 		if err != nil {
-			return nil, 0, fmt.Errorf("parse error: %w %s in %s", err, k, r.IANAToken)
+			return nil, 0, fmt.Errorf("%s: %w %s in %s", ParseError, err, k, r.IANAToken)
 		}
 		r.ICalParameters[k] = append(r.ICalParameters[k], v)
 		switch rune(contentLine[p]) {
@@ -253,10 +254,10 @@ func parsePropertyParamValue(s string, p int) (string, int, error) {
 	for ; p < len(s) && !done; p++ {
 		switch s[p] {
 		case 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08:
-			return "", 0, fmt.Errorf("unexpected char ascii:%d in property param value", s[p])
+			return "", 0, fmt.Errorf("%s:%d in property param value", UnexpectedASCIICharError, s[p])
 		case 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19, 0x1A, 0x1B,
 			0x1C, 0x1D, 0x1E, 0x1F:
-			return "", 0, fmt.Errorf("unexpected char ascii:%d in property param value", s[p])
+			return "", 0, fmt.Errorf("%s:%d in property param value", UnexpectedASCIICharError, s[p])
 		case '\\':
 			r = append(r, []byte(FromText(string(s[p+1:p+2])))...)
 			p++
@@ -276,7 +277,7 @@ func parsePropertyParamValue(s string, p int) (string, int, error) {
 				done = true
 				continue
 			}
-			return "", 0, fmt.Errorf("unexpected double quote in property param value")
+			return "", 0, errors.New(UnexpectedDoubleQuoteInPropertyParamValueError)
 		}
 		r = append(r, s[p])
 	}