Provide a fix

Author: firelizzard18

analyzer.go

@@ -52,7 +52,7 @@ type Analyzer struct {
 	template string
 }
 
-func (a *Analyzer) Analyze(target *Target) Issue {
+func (a *Analyzer) Analyze(target *Target) (i Issue) {
 	if a.template == "" {
 		return NewIssue("Missed template for check")
 	}
@@ -74,6 +74,16 @@ func (a *Analyzer) Analyze(target *Target) Issue {
 			offset.Position += 3
 		}
 	}
+	defer func() {
+		if i.Message() == "" {
+			return
+		}
+		fix, ok := a.generateFix(i, file, header)
+		if !ok {
+			return
+		}
+		i = NewIssueWithFix(i.Message(), i.Location(), fix)
+	}()
 	header = strings.TrimSpace(header)
 	if header == "" {
 		return NewIssue("Missed header for check")
@@ -144,3 +154,93 @@ func New(options ...Option) *Analyzer {
 	}
 	return a
 }
+
+func (a *Analyzer) generateFix(i Issue, file *ast.File, header string) (Fix, bool) {
+	var expect string
+	t := NewReader(a.template)
+	for !t.Done() {
+		ch := t.Peek()
+		if ch == '{' {
+			f := a.values[a.readField(t)]
+			if f == nil {
+				return Fix{}, false
+			}
+			if f.Calculate(a.values) != nil {
+				return Fix{}, false
+			}
+			expect += f.Get()
+			continue
+		}
+
+		expect += string(ch)
+		t.Next()
+	}
+
+	fix := Fix{Expected: strings.Split(expect, "\n")}
+	if !(len(file.Comments) > 0 && file.Comments[0].Pos() < file.Package) {
+		for i := range fix.Expected {
+			fix.Expected[i] = "// " + fix.Expected[i]
+		}
+		return fix, true
+	}
+
+	actual := file.Comments[0].List[0].Text
+	if !strings.HasPrefix(actual, "/*") {
+		for i := range fix.Expected {
+			fix.Expected[i] = "// " + fix.Expected[i]
+		}
+		for _, c := range file.Comments[0].List {
+			fix.Actual = append(fix.Actual, c.Text)
+		}
+		i = NewIssueWithFix(i.Message(), i.Location(), fix)
+		return fix, true
+	}
+
+	gets := func(i int, end bool) string {
+		if i < 0 {
+			return header
+		}
+		if end {
+			return header[i+1:]
+		}
+		return header[:i]
+	}
+	start := strings.Index(actual, gets(strings.IndexByte(header, '\n'), false))
+	if start < 0 {
+		return Fix{}, false // Should be impossible
+	}
+	nl := strings.LastIndexByte(actual[:start], '\n')
+	if nl >= 0 {
+		fix.Actual = strings.Split(actual[:nl], "\n")
+		fix.Expected = append(fix.Actual, fix.Expected...)
+		actual = actual[nl+1:]
+		start -= nl + 1
+	}
+
+	prefix := actual[:start]
+	if nl < 0 {
+		fix.Expected[0] = prefix + fix.Expected[0]
+	} else {
+		n := len(fix.Actual)
+		for i := range fix.Expected[n:] {
+			fix.Expected[n+i] = prefix + fix.Expected[n+i]
+		}
+	}
+
+	last := gets(strings.LastIndexByte(header, '\n'), true)
+	end := strings.Index(actual, last)
+	if end < 0 {
+		return Fix{}, false // Should be impossible
+	}
+
+	trailing := actual[end+len(last):]
+	if i := strings.IndexRune(trailing, '\n'); i < 0 {
+		fix.Expected[len(fix.Expected)-1] += trailing
+	} else {
+		fix.Expected[len(fix.Expected)-1] += trailing[:i]
+		fix.Expected = append(fix.Expected, strings.Split(trailing[i+1:], "\n")...)
+	}
+
+	fix.Actual = append(fix.Actual, strings.Split(actual, "\n")...)
+	return fix, true
+}

issue.go

@@ -19,11 +19,18 @@ package goheader
 type Issue interface {
 	Location() Location
 	Message() string
+	Fix() *Fix
 }
 
 type issue struct {
 	msg      string
 	location Location
+	fix      *Fix
+}
+
+type Fix struct {
+	Actual   []string
+	Expected []string
 }
 
 func (i *issue) Location() Location {
@@ -34,13 +41,25 @@ func (i *issue) Message() string {
 	return i.msg
 }
 
+func (i *issue) Fix() *Fix {
+	return i.fix
+}
+
 func NewIssueWithLocation(msg string, location Location) Issue {
 	return &issue{
 		msg:      msg,
 		location: location,
 	}
 }
 
+func NewIssueWithFix(msg string, location Location, fix Fix) Issue {
+	return &issue{
+		msg:      msg,
+		location: location,
+		fix:      &fix,
+	}
+}
+
 func NewIssue(msg string) Issue {
 	return &issue{
 		msg: msg,