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table.go
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table.go
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/*
Copyright (c) 2021 - Present. Blend Labs, Inc. All rights reserved
Use of this source code is governed by a MIT license that can be found in the LICENSE file.
*/
package ansi
import (
"fmt"
"io"
"reflect"
"strings"
"unicode/utf8"
"github.com/blend/go-sdk/ex"
)
// Table character constants.
const (
TableTopLeft = "┌"
TableTopRight = "┐"
TableBottomLeft = "└"
TableBottomRight = "┘"
TableMidLeft = "├"
TableMidRight = "┤"
TableVertBar = "│"
TableHorizBar = "─"
TableTopSep = "┬"
TableBottomSep = "┴"
TableMidSep = "┼"
NewLine = "\n"
)
// TableForSlice prints a table for a given slice.
// It will infer column names from the struct fields.
// If it is a mixed array (i.e. []interface{}) it will probably panic.
func TableForSlice(wr io.Writer, collection interface{}) error {
// infer the column names from the fields
cv := reflect.ValueOf(collection)
for cv.Kind() == reflect.Ptr {
cv = cv.Elem()
}
if cv.Kind() != reflect.Slice {
return ex.New("table for slice; cannot iterate over non-slice collection")
}
ct := cv.Type()
for ct.Kind() == reflect.Ptr || ct.Kind() == reflect.Slice {
ct = ct.Elem()
}
columns := make([]string, ct.NumField())
for index := 0; index < ct.NumField(); index++ {
columns[index] = ct.Field(index).Name
}
var rows [][]string
var rowValue reflect.Value
for row := 0; row < cv.Len(); row++ {
rowValue = cv.Index(row)
rowValues := make([]string, ct.NumField())
for fieldIndex := 0; fieldIndex < ct.NumField(); fieldIndex++ {
rowValues[fieldIndex] = fmt.Sprintf("%v", rowValue.Field(fieldIndex).Interface())
}
rows = append(rows, rowValues)
}
return Table(wr, columns, rows)
}
// Table writes a table to a given writer.
func Table(wr io.Writer, columns []string, rows [][]string) (err error) {
if len(columns) == 0 {
return ex.New("table; invalid columns; column set is empty")
}
/* helpers */
defer func() {
if r := recover(); r != nil {
if typed, ok := r.(error); ok {
err = typed
}
}
}()
write := func(str string) {
_, writeErr := io.WriteString(wr, str)
if writeErr != nil {
panic(writeErr)
}
}
/* end helpers */
/* begin establish max widths of columns */
maxWidths := make([]int, len(columns))
for index, columnName := range columns {
maxWidths[index] = stringWidth(columnName)
}
var width int
for _, cols := range rows {
for index, columnValue := range cols {
width = stringWidth(columnValue)
if maxWidths[index] < width {
maxWidths[index] = width
}
}
}
/* end establish max widths of columns */
/* draw top of column row */
write(TableTopLeft)
for index := range columns {
write(repeat(TableHorizBar, maxWidths[index]))
if isNotLast(index, columns) {
write(TableTopSep)
}
}
write(TableTopRight)
write(NewLine)
/* end draw top of column row */
/* draw column names */
write(TableVertBar)
for index, columnLabel := range columns {
write(padRight(columnLabel, maxWidths[index]))
if isNotLast(index, columns) {
write(TableVertBar)
}
}
write(TableVertBar)
write(NewLine)
/* end draw column names */
/* draw bottom of column row */
write(TableMidLeft)
for index := range columns {
write(repeat(TableHorizBar, maxWidths[index]))
if isNotLast(index, columns) {
write(TableMidSep)
}
}
write(TableMidRight)
write(NewLine)
/* end draw bottom of column row */
/* draw rows */
for _, row := range rows {
write(TableVertBar)
for index, column := range row {
write(padRight(column, maxWidths[index]))
if isNotLast(index, columns) {
write(TableVertBar)
}
}
write(TableVertBar)
write(NewLine)
}
/* end draw rows */
/* draw footer */
write(TableBottomLeft)
for index := range columns {
write(repeat(TableHorizBar, maxWidths[index]))
if isNotLast(index, columns) {
write(TableBottomSep)
}
}
write(TableBottomRight)
write(NewLine)
/* end draw footer */
return
}
func stringWidth(value string) (width int) {
var runeWidth int
for _, c := range value {
runeWidth = utf8.RuneLen(c)
if runeWidth > 1 {
width += 2
} else {
width++
}
}
return
}
func repeat(str string, count int) string {
return strings.Repeat(str, count)
}
func padRight(value string, width int) string {
valueWidth := stringWidth(value)
spaces := width - valueWidth
if spaces == 0 {
return value
}
return value + strings.Repeat(" ", spaces)
}
func isNotLast(index int, values []string) bool {
return index < (len(values) - 1)
}