#34: Remove blank vertical spaces in Markdown format

Author: vdjagilev

formatter/formatter_md.go

@@ -5,6 +5,7 @@ import (
 	_ "embed"
 	"fmt"
 	"html/template"
+	"io"
 	"strings"
 )
 
@@ -17,6 +18,77 @@ type MarkdownFormatter struct {
 // MarkdownTemplate variable is used to store markdown.tmpl embed file contents
 var MarkdownTemplate string
 
+type markdownOutputFilter struct {
+	writer  io.Writer
+	content []byte
+}
+
+func (m *markdownOutputFilter) Write(p []byte) (n int, err error) {
+	m.content = append(m.content, p...)
+	return len(p), nil
+}
+
+// split is used to split markdown content with new line delimiters
+func (m *markdownOutputFilter) split() [][]byte {
+	lines := [][]byte{}
+	line := []byte{}
+	for _, b := range m.content {
+		if b == '\n' {
+			// No need to add new line if previous one was defined as new line
+			if len(line) != 0 {
+				lines = append(lines, line)
+			}
+			lines = append(lines, []byte{})
+			line = []byte{}
+			continue
+		}
+		line = append(line, b)
+	}
+	if len(line) != 0 {
+		lines = append(lines, line)
+	}
+	return lines
+}
+
+func (m *markdownOutputFilter) filter() []byte {
+	content := []byte{}
+	contentLines := m.split()
+	newLines := 0
+	isCodeBlock := false
+	for _, l := range contentLines {
+		if len(l) >= 3 &&
+			l[0] == '`' &&
+			l[1] == '`' &&
+			l[2] == '`' {
+			isCodeBlock = !isCodeBlock
+		}
+
+		if !isCodeBlock {
+			if len(l) == 0 {
+				newLines++
+			} else {
+				newLines = 0
+			}
+
+			// Skip other new lines
+			if newLines > 2 {
+				continue
+			}
+
+			if newLines > 0 {
+				l = append(l, '\n')
+			}
+		} else {
+			// Simply add newline if it's empty slice
+			if len(l) == 0 {
+				l = append(l, '\n')
+			}
+		}
+		content = append(content, l...)
+	}
+	return content
+}
+
 // Format the data and output it to appropriate io.Writer
 func (f *MarkdownFormatter) Format(td *TemplateData) (err error) {
 	tmpl := template.New("markdown")
@@ -25,7 +97,13 @@ func (f *MarkdownFormatter) Format(td *TemplateData) (err error) {
 	if err != nil {
 		return
 	}
-	return tmpl.Execute(f.config.Writer, td)
+	markdownOutput := &markdownOutputFilter{writer: f.config.Writer, content: []byte{}}
+	err = tmpl.Execute(markdownOutput, td)
+	if err != nil {
+		return err
+	}
+	_, err = f.config.Writer.Write(markdownOutput.filter())
+	return err
 }
 
 func (f *MarkdownFormatter) defineTemplateFunctions(tmpl *template.Template) {

formatter/formatter_md_test.go

@@ -541,3 +541,104 @@ func Test_markdownHostAnchorTitle(t *testing.T) {
 		})
 	}
 }
+
+func Test_markdownOutputFilter_filter(t *testing.T) {
+	tests := []struct {
+		name string
+		m    *markdownOutputFilter
+		want []byte
+	}{
+		{
+			name: "Double new lines",
+			m: &markdownOutputFilter{
+				content: []byte("# Header\n## Header 2\n### Header 3\n\nNew sentence\n\nAnother new sentence"),
+			},
+			want: []byte("# Header\n## Header 2\n### Header 3\n\nNew sentence\n\nAnother new sentence"),
+		},
+		{
+			name: "Simple codeblock",
+			m: &markdownOutputFilter{
+				content: []byte("# Header\nSome code:\n```\n\nSome newlines should be ignored\nhere\n\n```\n\n# Test\n\nNew sentence\n"),
+			},
+			want: []byte("# Header\nSome code:\n```\n\nSome newlines should be ignored\nhere\n\n```\n\n# Test\n\nNew sentence\n"),
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := tt.m.filter(); !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("markdownOutputFilter.filter() = %v, want %v", string(got), string(tt.want))
+			}
+		})
+	}
+}
+
+func Test_markdownOutputFilter_split(t *testing.T) {
+	tests := []struct {
+		name string
+		m    *markdownOutputFilter
+		want [][]byte
+	}{
+		{
+			name: "Double new line",
+			m: &markdownOutputFilter{
+				content: []byte("Test double\n\ntest"),
+			},
+			want: [][]byte{
+				[]byte("Test double"),
+				{},
+				{},
+				[]byte("test"),
+			},
+		},
+		{
+			name: "Multiple lines with double new lines",
+			m: &markdownOutputFilter{
+				content: []byte("# Header\n## Header 2\n### Header 3\n\nNew sentence\n\nAnother new sentence"),
+			},
+			want: [][]byte{
+				[]byte("# Header"),
+				{},
+				[]byte("## Header 2"),
+				{},
+				[]byte("### Header 3"),
+				{},
+				{},
+				[]byte("New sentence"),
+				{},
+				{},
+				[]byte("Another new sentence"),
+			},
+		},
+		{
+			name: "New line in the beginning",
+			m: &markdownOutputFilter{
+				content: []byte("\nNew line\n\n"),
+			},
+			want: [][]byte{
+				{},
+				[]byte("New line"),
+				{},
+				{},
+			},
+		},
+		{
+			name: "Many lines in the end",
+			m: &markdownOutputFilter{
+				content: []byte("New test\n\n\n"),
+			},
+			want: [][]byte{
+				[]byte("New test"),
+				{},
+				{},
+				{},
+			},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := tt.m.split(); !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("markdownOutputFilter.split() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}

formatter/resources/templates/markdown.tmpl

@@ -17,6 +17,7 @@ NMAP Scan Result: {{ .NMAPRun.StartStr }}
 
 {{- if not $skipSummary }}
 ----
+
 ## Scan Summary
 
 | Name | Value |