alba/backend/main.go

package main

import (
	"fmt"
	"log"
	"net/http"
	"os"
	"os/exec"
	"text/template"
	"time"

	"github.com/mmcdole/gofeed"
	"gogs.carduccidante.edu.it/karmen/core/util/pandoc"
	tplutil "gogs.carduccidante.edu.it/karmen/core/util/template"
)

var funcmap = template.FuncMap{
	"day": func() int {
		_, _, day := time.Now().Date()
		return day
	},
	"month": func() int {
		_, month, _ := time.Now().Date()
		return int(month)
	},
	"year": func() int {
		year, _, _ := time.Now().Date()
		return year
	},
	"news": func() []*gofeed.Item {
		result := make([]*gofeed.Item, 0)

		fp := gofeed.NewParser()
		feed, _ := fp.ParseURL("https://www.agi.it/innovazione/rss")

		for _, it := range feed.Items {
			result = append(result, it)
		}

		return result[:2]
	},
	"weather": func() []*gofeed.Item {
		result := make([]*gofeed.Item, 0)

		fp := gofeed.NewParser()
		feed, _ := fp.ParseURL("https://www.meteowebcam.eu/rss.xml")

		for _, it := range feed.Items {
			result = append(result, it)
		}

		return result[:1]
	},
}

func convertPDFToBMP(filename string) error {
	out, err := exec.Command("pdftoppm", filename, "./data/screen", "-png").CombinedOutput()
	if string(out) != "" {
		return fmt.Errorf("pdftoppm: %s", string(out))
	}
	if err != nil {
		return err
	}
	out, err = exec.Command("convert", "./data/screen-1.png",
		"-rotate", "-90",
		"-resize", "800x480!",
		"-dither", "none",
		"-remap", "./data/palette.gif",
		"BMP3:./data/screen.bmp",
	).CombinedOutput()
	if string(out) != "" {
		return fmt.Errorf("covert: %s", string(out))
	}
	if err != nil {
		return err
	}

	return nil
}

func serveScreen(res http.ResponseWriter, req *http.Request) {
	tpl, err := tplutil.LoadTextTemplate("./data/screen.tpl.md", funcmap)
	if err != nil {
		panic(err)
	}

	f, err := os.Create("./data/screen.md")
	if err != nil {
		panic(err)
	}
	defer f.Close()

	var data struct {
		Title string
		Item  *gofeed.Item
	}

	log.Println("Generating markdown file from template.")
	if err := tpl.Execute(f, data); err != nil {
		panic(err)
	}

	log.Println("Converting markdown to pdf.")
	// err = pandoc.Convert("./data/screen.md", "./data/screen.pdf", "-V", "geometry:papersize={3.8in,6in}", "-V", "pagestyle:empty")
	err = pandoc.Convert("./data/screen.md", "./data/screen.pdf", "-V", "pagestyle:empty")
	if err != nil {
		panic(err)
	}

	log.Println("Converting PDF to monochrome BMP.")
	err = convertPDFToBMP("./data/screen.pdf")
	if err != nil {
		panic(err)
	}

	log.Println("Serving screen.png...")
	http.ServeFile(res, req, "./data/screen.bmp")
}

func main() {
	http.HandleFunc("/", serveScreen)

	log.Println("Start alba backend...")
	http.ListenAndServe(":3000", nil)
}