main.go

package main

import (
	"fmt"
	"log"
	"os"
	"time"

	"github.com/codegangsta/cli"
	"github.com/nlopes/slack"
)

func main() {
	app := cli.NewApp()
	app.Name = "slacknimate"
	app.Usage = "text animation for Slack messages"
	app.Version = "1.0.0-alpha"
	app.UsageText = "slacknimate [options]"
	app.Flags = []cli.Flag{
		cli.StringFlag{
			Name:   "api-token, a",
			Usage:  "API token*",
			EnvVar: "SLACK_TOKEN",
		},
		cli.Float64Flag{
			Name:  "delay, d",
			Usage: "minimum delay between frames",
			Value: 1,
		},
		cli.StringFlag{
			Name:   "channel, c",
			Usage:  "channel/destination*",
			EnvVar: "SLACK_CHANNEL",
		},
		cli.BoolFlag{
			Name:  "loop, l",
			Usage: "loop content upon reaching end",
		},
		cli.BoolFlag{
			Name:  "preview",
			Usage: "preview on terminal instead of posting",
		},
	}
	app.Action = func(c *cli.Context) {
		apiToken := c.String("api-token")
		channel := c.String("channel")
		delay := c.Float64("delay")
		noop := c.Bool("preview")

		if !noop {
			stderr := log.New(os.Stderr, "", 0) // log to stderr with no timestamps
			if apiToken == "" {
				stderr.Fatal("API token is required.",
					" Use --api-token or set SLACK_TOKEN env variable.")
			}
			if channel == "" {
				stderr.Fatal("Destination is required.",
					" Use --channel or set SLACK_CHANNEL env variable.")
			}
			if delay < 0.001 {
				stderr.Fatal("You must have a delay >=0.001 to avoid creating a time paradox.")
			}
		}

		var frames chan string
		if c.Bool("loop") {
			frames = LoopingStdinScanner()
		} else {
			frames = StdinScanner()
		}

		api := slack.New(apiToken)
		params := slack.NewPostMessageParameters()
		params.AsUser = true

		var dst, ts, txt string
		tickerChan := time.Tick(time.Millisecond * time.Duration(delay*1000))

		for frame := range frames {
			<-tickerChan
			if noop {
				fmt.Printf("\033[2K\r%s", frame)
			} else {
				if dst == "" || ts == "" {
					var err error
					dst, ts, err = api.PostMessage(channel, frame, params)
					if err != nil {
						log.Fatal("FATAL: Could not post initial frame to Slack: ", err)
					}
					log.Printf("initial frame %v/%v: %v\n", dst, ts, frame)
				} else {
					var err error
					_, _, txt, err = api.UpdateMessage(dst, ts, frame)
					if err != nil {
						log.Printf("ERROR updating %v/%v with frame %v: %v", dst, ts, frame, err)
					} else {
						log.Printf("updated frame %v/%v: %v", dst, ts, txt)
					}
				}
			}
		}

		fmt.Println("\nDone!")
	}

	app.Run(os.Args)
}