bar.go

/*
   Copyright The containerd Authors.

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.
*/

package progress

import (
	"bytes"
	"fmt"
)

// TODO(stevvooe): We may want to support more interesting parameterization of
// the bar. For now, it is very simple.

// Bar provides a very simple progress bar implementation.
//
// Use with fmt.Printf and "r" to format the progress bar. A "-" flag makes it
// progress from right to left.
type Bar float64

var _ fmt.Formatter = Bar(1.0)

// Format the progress bar as output
func (h Bar) Format(state fmt.State, r rune) {
	switch r {
	case 'r':
	default:
		panic(fmt.Sprintf("%v: unexpected format character", float64(h)))
	}

	if h > 1.0 {
		h = 1.0
	}

	if h < 0.0 {
		h = 0.0
	}

	if state.Flag('-') {
		h = 1.0 - h
	}

	width, ok := state.Width()
	if !ok {
		// default width of 40
		width = 40
	}

	var pad int

	extra := len([]byte(green)) + len([]byte(reset))

	p := make([]byte, width+extra)
	p[0], p[len(p)-1] = '|', '|'
	pad += 2

	positive := int(Bar(width-pad) * h)
	negative := width - pad - positive

	n := 1
	n += copy(p[n:], []byte(green))
	n += copy(p[n:], bytes.Repeat([]byte("+"), positive))
	n += copy(p[n:], []byte(reset))

	if negative > 0 {
		copy(p[n:len(p)-1], bytes.Repeat([]byte("-"), negative))
	}

	state.Write(p)
}