xkcd-time/main.go

105 lines
1.7 KiB
Go

package main
import (
"bytes"
"context"
"flag"
"fmt"
"image"
"image/color"
"image/png"
"log"
"net/http"
"os"
"sync"
"time"
"github.com/pkg/errors"
)
var port = flag.Int("port", 8000, "port")
var freq = flag.Duration("d", 15*time.Second, "refresh interval")
type Now struct {
sync.RWMutex
cache *bytes.Buffer
}
func NewNow(ctx context.Context, d time.Duration) *Now {
n := &Now{
cache: &bytes.Buffer{},
}
n.Update()
go func() {
t := time.NewTicker(d)
for {
select {
case <-t.C:
n.Update()
case <-ctx.Done():
return
}
}
}()
return n
}
func (n *Now) ServeHTTP(w http.ResponseWriter, req *http.Request) {
n.RLock()
w.Write(n.cache.Bytes())
n.RUnlock()
}
func (n *Now) Update() error {
resp, err := http.Get("http://imgs.xkcd.com/comics/now.png")
if err != nil {
return errors.Wrap(err, "get")
}
defer resp.Body.Close()
src, err := png.Decode(resp.Body)
if err != nil {
return errors.Wrap(err, "png decode")
}
bounds := src.Bounds()
dest := image.NewNRGBA(bounds)
for y := bounds.Min.Y; y < bounds.Max.Y; y++ {
for x := bounds.Min.X; x < bounds.Max.X; x++ {
r, g, b, _ := src.At(x, y).RGBA()
if r == 0xFFFF && g == 0xFFFF && b == 0xFFFF {
dest.Set(x, y, color.NRGBA{0, 0, 0, 0})
} else {
dest.Set(x, y, src.At(x, y))
}
}
}
n.Lock()
png.Encode(n.cache, dest)
n.Unlock()
return nil
}
func main() {
flag.Parse()
hostname, err := os.Hostname()
if err != nil {
log.Fatal("problem getting hostname:", err)
}
log.Printf("serving on: http://%s:%d/", hostname, *port)
addr := fmt.Sprintf(":%d", *port)
n := NewNow(context.Background(), *freq)
http.Handle("/", n)
err = http.ListenAndServe(addr, nil)
if err != nil {
log.Fatal(err)
}
}