library/ui/ui.go

package ui

import (
	"strings"

	"github.com/gdamore/tcell"
)

type Drawable interface {
	Draw(tcell.Screen)
	SetSize(x, y, h, w int)
}

type Offsets struct {
	Top    int
	Bottom int
	Left   int
	Right  int
}

type Contents []struct {
	Offsets   Offsets
	Container Drawable
}

const (
	LayoutUnmanaged = iota
	LayoutHorizontalEven
	LayoutVerticalEven
)

// A Container has no visible UI of its own, but arranges sub-components on the screen.
// layoutMethod manages how subcomponents are organized. If `LayoutUnmanaged`, it just uses the offsets
// in contents to paint on the screen. Otherwise, `LayoutHorizontalEven` and `LayoutVerticalEven` will
// have it compute even distributions of space for all components either horizontally or vertically,
// filling the container.
type Container struct {
	x, y         int
	h, w         int
	layoutMethod int
	contents     Contents
}

func NewContainer(contents Contents, layoutMethod int) *Container {
	return &Container{
		layoutMethod: layoutMethod,
		contents:     contents,
	}
}

func (c *Container) Draw(s tcell.Screen) {
	for i := range c.contents {
		c.contents[i].Container.Draw(s)
	}
}

func (c *Container) SetSize(x, y, h, w int) {
	c.x, c.y, c.h, c.w = x, y, h, w
	if c.layoutMethod == LayoutVerticalEven {
		num := len(c.contents)
		for r := range c.contents {
			x := c.x
			y := c.y + (num * (r + 1))
			h := c.h / num
			w := c.w
			c.contents[r].Container.SetSize(x, y, h, w)
		}
	} else if c.layoutMethod == LayoutHorizontalEven {
		num := len(c.contents)
		for r := range c.contents {
			w := c.w / num
			h := c.h
			x := c.x + (w * r)
			y := c.y
			c.contents[r].Container.SetSize(x, y, h, w)
		}
	} else {
		for r := range c.contents {
			x := c.x + c.contents[r].Offsets.Left
			y := c.y + c.contents[r].Offsets.Top
			h := c.h - c.contents[r].Offsets.Bottom
			w := c.w - c.contents[r].Offsets.Right
			c.contents[r].Container.SetSize(x, y, h, w)
		}
	}
}

func (c *Container) Contents() Contents {
	return c.contents
}

func (c *Container) SetContents(con Contents) {
	c.contents = con
}

// A Box draws a ASCII box around its contents, with an optional title and footer.
type Box struct {
	x, y      int
	h, w      int
	title     Drawable
	menuItems Drawable
	contents  Contents
}

func NewBox(title string, menuItems []string, contents Contents) *Box {
	return &Box{
		title:     NewPaddedText(title),
		menuItems: NewPaddedText(strings.Join(menuItems, " ")),
		contents:  contents,
	}
}

func (b *Box) SetSize(x, y, h, w int) {
	b.x, b.y, b.h, b.w = x, y, h, w
	b.title.SetSize(b.x+2, b.y, 0, 0)
	b.menuItems.SetSize(b.x+2, b.y+b.h-1, 0, 0)
	for c := range b.contents {
		x := b.x + b.contents[c].Offsets.Left
		y := b.y + b.contents[c].Offsets.Top
		h := b.h - b.contents[c].Offsets.Bottom
		w := b.w - b.contents[c].Offsets.Right
		b.contents[c].Container.SetSize(x, y, h, w)
	}
}

func (b *Box) Draw(s tcell.Screen) {
	for m := 1; m < b.w-1; m++ {
		s.SetContent(m, b.y, tcell.RuneHLine, nil, tcell.StyleDefault)
		s.SetContent(m, b.h-1, tcell.RuneHLine, nil, tcell.StyleDefault)
	}
	for m := 1; m < b.h-1; m++ {
		s.SetContent(b.x, m, tcell.RuneVLine, nil, tcell.StyleDefault)
		s.SetContent(b.w-1, m, tcell.RuneVLine, nil, tcell.StyleDefault)
	}
	s.SetContent(b.x, b.y, tcell.RuneULCorner, nil, tcell.StyleDefault)
	s.SetContent(b.w-1, b.y, tcell.RuneURCorner, nil, tcell.StyleDefault)
	s.SetContent(b.x, b.h-1, tcell.RuneLLCorner, nil, tcell.StyleDefault)
	s.SetContent(b.w-1, b.h-1, tcell.RuneLRCorner, nil, tcell.StyleDefault)

	if b.title != nil {
		b.title.Draw(s)
	}
	if b.menuItems != nil {
		b.menuItems.Draw(s)
	}
	for c := range b.contents {
		b.contents[c].Container.Draw(s)
	}
}

func (b *Box) Contents() Contents {
	return b.contents
}

func (b *Box) SetContents(c Contents) {
	b.contents = c
}

// A List is a scrollable, pageable list with a selector token.
type List struct {
	x, y      int
	h, w      int
	selected  int
	listItems []string
}

func NewList(listItems []string, initialSelected int) *List {
	return &List{
		listItems: listItems,
		selected:  initialSelected,
	}
}

func (l *List) SetSize(x, y, h, w int) {
	l.x, l.y, l.h, l.w = x, y, h, w
}

func (l *List) Draw(s tcell.Screen) {
	for i := range l.listItems {
		for j, r := range l.listItems[i] {
			s.SetContent(l.x+j, l.y+i, r, nil, tcell.StyleDefault)
		}
		if i == l.selected {
			s.SetContent(l.x+len(l.listItems[i])+1, l.y+i, '<', nil, tcell.StyleDefault)
		}
	}
}

func (l *List) Selected() int {
	return l.selected
}

func (l *List) SetSelected(i int) {
	l.selected = i
}

func (l *List) ListMembers() []string {
	return l.listItems
}

// PaddedText outputs strings with a space on both sides.
// Useful for generating headings, footers, etc. Used by Box.
type PaddedText struct {
	x, y int
	h, w int
	text string
}

func NewPaddedText(text string) *PaddedText {
	return &PaddedText{text: text}
}

func (p *PaddedText) SetSize(x, y, _, _ int) {
	p.x, p.y, p.h, p.w = x, y, 1, len(p.text)+2
}

func (p *PaddedText) Draw(s tcell.Screen) {
	t := p.x
	s.SetContent(t, p.y, ' ', nil, tcell.StyleDefault)
	t++
	for _, r := range p.text {
		s.SetContent(t, p.y, r, nil, tcell.StyleDefault)
		t++
	}
	s.SetContent(t, p.y, ' ', nil, tcell.StyleDefault)
}