library/main.go

package main

import (
	"flag"
	"fmt"
	"io"
	"log"
	"net/http"
	"net/url"
	"os"
	"path/filepath"
	"os/exec"
	"strings"
	_ "embed"
)

//go:embed tncmd.sh
var thumbnailCmd string

//go:embed styles.css
var styleSheet string

//easily put attrs in a tag
type htmlAttrs map[string]string
func (attrs htmlAttrs) String() string {
	var ret string
	for k, v := range attrs {
		ret += fmt.Sprintf("%s=\"%s\" ", k, url.QueryEscape(v))
	}

	return ret
}

func imgWithTagAttrs(a htmlAttrs) string {
	return fmt.Sprintf("<img %s/>", a.String())
}

func wrapWithTagAttrs(str, tag string, a htmlAttrs) string {
	return fmt.Sprintf("<%s %s>%s</%s>", tag, a.String(), str, tag)
}

func wrapWithTag(str string, tag string) string {
	return fmt.Sprintf("<%s>%s</%s>", tag, str, tag)
}

//cleaner than making an attr for one href
func wrapWithTagHref(str string, tag string) string {
	return fmt.Sprintf("<%s href=%s>%s</%s>", tag, url.QueryEscape(str), str, tag)
}

func serveStylesheet(w http.ResponseWriter, r *http.Request) {
	sheet, err := os.Open("styles.css")
	if err != nil {
		http.Error(w, "File not found", http.StatusNotFound)
		return	
	}
	defer sheet.Close()

	w.Header().Set("Content-Disposition", "attachment; filename=style.css")
	w.Header().Set("Content-Type", "text/css")
	
	_, err = io.Copy(w, sheet)
	if err != nil {
		http.Error(w, "Error sending file", http.StatusInternalServerError)
		return
	}
	
}

func createThumbnailsDirectory() {
	if _, err := os.Stat("./thumbnails"); err != nil {
		if os.IsNotExist(err) {
			os.Mkdir("thumbnails", 0755)
		}
		return
	}
}

func main() {
	port  := flag.String("p", "6969", "port to serve on")
	directory := flag.String("d", ".", "the directory of static file to host")
	converter := flag.String("t", ".", "location of conversion script")
	flag.Parse()

	createThumbnailsDirectory()

	var contents string
	entries, err := os.ReadDir(*directory)
	if err != nil {
		log.Fatal(err)
	}

	for _, e := range entries {
		go func(name string) {
			new := name
			newImg := strings.TrimSuffix(new, filepath.Ext(new)) + ".png"
		
			if filepath.Ext(new) != ".pdf" {
				return
			}

			dir, _ := filepath.Abs(*directory)

			cmd := exec.Command(*converter, filepath.Join(dir, name))

			fmt.Println(cmd)

			if err := cmd.Run(); err != nil {
				log.Println(err)
			} else {
				fmt.Println("Created thumbnail for: " + new)
				http.HandleFunc("/" + url.QueryEscape(newImg), func(w http.ResponseWriter, r *http.Request) {
					w.Header().Set("Content-Type", "img/png")

					file, err := os.Open(*directory +"/"+ newImg)
					if err != nil {
						http.Error(w, "File not found.", http.StatusNotFound)
						return	
					}
					defer file.Close()
					
					_, err = io.Copy(w, file)
					if err != nil {
						http.Error(w, "Error sending file.", http.StatusInternalServerError)
						return
					}
				})
			}
		}(e.Name())
	}

	for _, e := range entries {
		new := e.Name()
		newImg := strings.TrimSuffix(new, filepath.Ext(new)) + ".png"
	
		if filepath.Ext(new) != ".pdf" {
			continue
		}

		//if new == "style.css" { continue }		

		http.HandleFunc("/" + url.QueryEscape(new), func(w http.ResponseWriter, r *http.Request) {
			log.Println("Request for resource: ", r.RequestURI)
			
			file, err := os.Open(*directory + "/" +  new)
			if err != nil {
				http.Error(w, "File not found.", http.StatusNotFound)
				return
			}
			defer file.Close()

			w.Header().Set("Content-Disposition", "attachment; filename=" + new)
			w.Header().Set("Content-Type", "application/pdf")

			_, err = io.Copy(w, file)
			if err != nil {
				http.Error(w, "Error sending file.", http.StatusInternalServerError)
				return
			}
		})

		gridAttrs := htmlAttrs {
			"class": "grid-item", 
		}

		hrefAttrs := htmlAttrs {
			"href": e.Name(),
		}

		imgAttrs := htmlAttrs {
			"src": newImg,
		}

		var img string
		img = imgWithTagAttrs(imgAttrs)

		var href string
		href = wrapWithTagAttrs(img, "a", hrefAttrs)
		contents += wrapWithTagAttrs(href, "div", gridAttrs)
		contents += "\n"
	}

	gridContainerAttrs := htmlAttrs {
		"class": "grid-container",
	}

	contents = wrapWithTagAttrs(contents, "div", gridContainerAttrs)
	contents = wrapWithTag(contents, "pre")

	contents = wrapWithTag(string(styleSheet), "style") + contents
	contents = wrapWithTag(contents, "html")
	contents = "<!DOCTYPE html>" + contents

	handler := func(w http.ResponseWriter, r *http.Request) {
		w.Write([]byte(contents))
	}

	http.Handle("/", http.HandlerFunc(handler))
	//http.Handle("/styles.css", http.HandlerFunc(serveStylesheet))
	log.Printf("Serving %s on HTTP port: %s\n", *directory, *port)
	log.Fatal(http.ListenAndServe(":"+*port, nil))
}