Provides a way to construct a markdown table by adding rows and then outputting the table in markdown format with properly aligned columns.

MarkdownTable.go

package export

import (
	"bytes"
	"io"
	"strings"
	"unicode/utf8"
)

type MarkdownTable struct {
	widths []int
	rows   [][]string
}

func (mkt *MarkdownTable) AddRow(data ...string) {
	if len(data) > len(mkt.widths) {
		newWidths := make([]int, len(data))
		copy(newWidths, mkt.widths)
		mkt.widths = newWidths
	}

	for cell_index, cell := range data {
		max_width := mkt.widths[cell_index]
		width := utf8.RuneCountInString(cell)
		if width > max_width {
			mkt.widths[cell_index] = width
		}
	}

	newRows := append(mkt.rows, data)
	mkt.rows = newRows
}

func (mkt MarkdownTable) WriteTo(w io.Writer) (int64, error) {
	sep := []byte("|")
	padding := []byte(" ")
	eol := []byte("\n")

	buffer := new(bytes.Buffer)
	var written int64

	for row_index, row := range mkt.rows {
		buffer.Reset()
		for cell_index, cell := range row {
			if cell_index == 0 {
				buffer.Write(sep)
				buffer.Write(padding)
			} else {
				buffer.Write(padding)
				buffer.Write(sep)
				buffer.Write(padding)
			}

			txtLenght := utf8.RuneCountInString(cell)
			cellLength := mkt.widths[cell_index]
			buffer.WriteString(cell)

			fillLength := cellLength - txtLenght
			fill := strings.Repeat(" ", fillLength)
			buffer.WriteString(fill)
		}
		buffer.Write(padding)
		buffer.Write(sep)
		buffer.Write(eol)

		if row_index == 0 {
			mkt.writeHeaderSeparator(buffer)
		}

		count, err := buffer.WriteTo(w)
		written += count
		if err != nil {
			return written, err
		}
	}
	return written, nil
}

func (mkt MarkdownTable) writeHeaderSeparator(w io.Writer) {
	sep := []byte("|")
	eol := []byte("\n")
	for _, width := range mkt.widths {
		w.Write(sep)
		fill := strings.Repeat("-", width+2)
		w.Write([]byte(fill))
	}
	w.Write(sep)
	w.Write(eol)
}

func NewMarkdownTable() *MarkdownTable {
	widths := make([]int, 0)
	rows := make([][]string, 0)
	mkt := MarkdownTable{rows: rows, widths: widths}
	return &mkt
}

MarkdownTable_test.go

package export

import (
	"bytes"
	"testing"

	"github.com/stretchr/testify/assert"
)

func TestBasic(t *testing.T) {
	mkt := NewMarkdownTable()
	mkt.AddRow("Lorem", "ipsum", "dolor", "sit", "amet")
	mkt.AddRow("consectetur", "adipiscing", "elit", "", "")

	bb := new(bytes.Buffer)
	mkt.WriteTo(bb)
	txt := bb.String()
	expected := "" +
		"| Lorem       | ipsum      | dolor | sit | amet |\n" +
		"|-------------|------------|-------|-----|------|\n" +
		"| consectetur | adipiscing | elit  |     |      |\n"

	assert.Equal(t, expected, txt)
}