exo/travel.go

package main

import (
	"bytes"
	"fmt"
	"text/template"
	"time"
)

type TravelState struct {
	CommandSuite
	start     *System
	dest      *System
	travelled float64 // distance traveled so far in parsecs
	dist      float64 // distance between start and end in parsecs
}

func NewTravel(c *Connection, start, dest *System) ConnectionState {
	t := &TravelState{
		start: start,
		dest:  dest,
		dist:  start.DistanceTo(dest),
	}
	t.CommandSuite = CommandSet{
		playersCommand,
		balCommand,
		Command{
			name:    "progress",
			summary: "displays how far you are along your travel",
			arity:   0,
			handler: t.progress,
		},
		Command{
			name:    "eta",
			summary: "displays estimated time of arrival",
			arity:   0,
			handler: func(c *Connection, args ...string) {
				c.Printf("%v\n", t.remaining())
			},
		},
	}
	return t
}

var enterTravelTemplate = template.Must(template.New("enter-travel").Parse(`
Departing:       {{.Departing}}
Destination:     {{.Destination}}
Total Trip Time: {{.Duration}}
`))

func (t *TravelState) Enter(c *Connection) {
	enterTravelTemplate.Execute(c, struct {
		Departing   *System
		Destination *System
		Duration    time.Duration
	}{
		t.start,
		t.dest,
		t.tripTime(),
	})
	t.start.Leave(c)
}

func (t *TravelState) Tick(c *Connection, frame int64) ConnectionState {
	dt := options.playerSpeed * options.lightSpeed

	segmentLength := t.dist / 18
	x := t.travelled
	for x > segmentLength {
		x -= segmentLength
	}
	if x < dt {
		c.Printf("%v", t.start.name)
		var buf bytes.Buffer
		segment := int(t.travelled / t.dist * 18)
		buf.WriteRune('|')
		for i := 0; i < 18; i++ {
			switch {
			case i == segment:
				buf.WriteRune('>')
			case i == segment-1:
				buf.WriteRune('=')
			case i < segment:
				buf.WriteRune('-')
			default:
				buf.WriteRune(' ')
			}
		}
		buf.WriteRune('|')
		c.Write(buf.Bytes())
		c.Printf("at %v in %v\n", t.dest.name, t.remaining())
	}

	t.travelled += dt
	if t.travelled >= t.dist {
		return Idle(t.dest)
	}
	return t
}

func (t *TravelState) Exit(c *Connection) {
	c.Printf("You have arrived at %v.\n", t.dest)
	t.dest.Arrive(c)
}

func (t *TravelState) String() string {
	return fmt.Sprintf("Traveling from %v to %v", t.start, t.dest)
}

func (t *TravelState) FillStatus(c *Connection, s *status) {
	s.Location = fmt.Sprintf("between %s and %s", t.start, t.dest)
}

func (t *TravelState) progress(c *Connection, args ...string) {
	c.Printf("%v\n", t.travelled/t.dist)
}

func (t *TravelState) remaining() time.Duration {
	remaining := t.dist - t.travelled
	frames := remaining / (options.playerSpeed * options.lightSpeed)
	return framesToDur(int64(frames))
}

func (t *TravelState) eta() time.Time {
	// distance remaining in parsecs
	return time.Now().Add(t.remaining())
}

func (t *TravelState) tripTime() time.Duration {
	frames := t.dist / (options.playerSpeed * options.lightSpeed)
	return framesToDur(int64(frames))
}