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package main
import (
"flag"
"fmt"
"io"
"io/ioutil"
"log"
"net/http"
"os"
"path"
"strings"
)
const usage = `Usage: iiifdownloader url
Downloads all pages from a IIIF server.
Currently supports the following IIIF using services:
- BNF's Gallica (any book or page URL should work)
`
const bnfPrefix = `https://gallica.bnf.fr/ark:/`
const bsbPrefix = `https://reader.digitale-sammlungen.de/de/fs1/object/display/`
func filesAreIdentical(fn1, fn2 string) (bool, error) {
f1, err := os.Open(fn1)
defer f1.Close()
if err != nil {
return false, fmt.Errorf("Error opening file %s: %v\n", fn1, err)
}
b1, err := ioutil.ReadAll(f1)
if err != nil {
return false, fmt.Errorf("Error reading file %s: %v\n", fn1, err)
}
f2, err := os.Open(fn2)
defer f2.Close()
if err != nil {
return false, fmt.Errorf("Error opening file %s: %v\n", fn2, err)
}
b2, err := ioutil.ReadAll(f2)
if err != nil {
return false, fmt.Errorf("Error reading file %s: %v\n", fn2, err)
}
for i, _ := range b1 {
if b1[i] != b2[i] {
return false, nil
}
}
return true, nil
}
func parseMets(url string) ([]string, error) {
var urls []string
// TODO: download and parse xml;
// https://daten.digitale-sammlungen.de/~db/mets/bsb11274872_mets.xml
// mets:mets -> mets:fileSec -> mets:fileGrp USE="MAX" -> mets:file -> mets:FLocat xlink:href
return urls, nil
}
func main() {
flag.Usage = func() {
fmt.Fprintf(flag.CommandLine.Output(), usage)
flag.PrintDefaults()
}
flag.Parse()
if flag.NArg() < 1 {
flag.Usage()
return
}
url := flag.Arg(0)
var bookdir string
var pgurlStart, pgurlEnd string
var pgurlAltStart, pgurlAltEnd string
var pgUrls []string
var noPgNums bool
var err error
switch {
case strings.HasPrefix(url, bnfPrefix):
f := strings.Split(url[len(bnfPrefix):], "/")
if len(f) < 2 {
log.Fatalln("Failed to extract BNF book ID from URL")
}
var lastpart string
dot := strings.Index(f[1], ".")
if dot == -1 {
lastpart = f[1]
} else {
lastpart = f[1][0:dot]
}
bookid := f[0] + "/" + lastpart
bookdir = f[0] + "-" + lastpart
pgurlStart = "https://gallica.bnf.fr/iiif/ark:/" + bookid + "/f"
pgurlEnd = "/full/full/0/native.jpg"
noPgNums = true
// BNF don't have all pages available from IIIF, but they do have
// the missing ones in less good quality from an alternative URL.
pgurlAltStart = "https://gallica.bnf.fr/ark:/" + bookid + "/f"
pgurlAltEnd = ".highres"
case strings.HasPrefix(url, bsbPrefix):
f := strings.Split(url[len(bsbPrefix):], "_")
if len(f) < 2 {
log.Fatalln("Failed to extract BNF book ID from URL")
}
bookid := f[0]
metsurl := "https://daten.digitale-sammlungen.de/~db/mets/" + bookid + "_mets.xml"
pgUrls, err = parseMets(metsurl)
if err != nil {
log.Fatalf("Error parsing mets url %s: %v\n", metsurl, err)
}
default:
log.Fatalln("Error: generic IIIF downloading not supported yet")
}
err = os.MkdirAll(bookdir, 0777)
if err != nil {
log.Fatalf("Error creating book dir: %v\n", err)
}
if len(pgUrls) > 0 {
fmt.Printf("I'll do something proper with these urls: %v\n", pgUrls)
} else if noPgNums {
pgnum := 0
for {
pgnum++
fmt.Printf("Downloading page %d\n", pgnum)
fn := path.Join(bookdir, fmt.Sprintf("%04d.jpg", pgnum))
_, err = os.Stat(fn)
if err == nil || os.IsExist(err) {
fmt.Printf("Skipping already present page %d\n", pgnum)
continue
}
u := fmt.Sprintf("%s%d%s", pgurlStart, pgnum, pgurlEnd)
resp, err := http.Get(u)
if err != nil {
log.Fatalf("Error downloading page %d, %s: %v\n", pgnum, u, err)
}
defer resp.Body.Close()
switch {
case resp.StatusCode == http.StatusNotFound:
fmt.Printf("Got 404, assuming end of pages, for page %d, %s\n", pgnum, u)
return
case resp.StatusCode != http.StatusOK:
fmt.Printf("Error downloading page %d, %s: HTTP Code %s\n", pgnum, u, resp.Status)
if pgurlAltStart == "" && pgurlAltEnd == "" {
log.Fatalln("No alternative URL to try, book failed (or ended, hopefully)")
}
fmt.Printf("Trying to redownload page %d at lower quality\n", pgnum)
u = fmt.Sprintf("%s%d%s", pgurlAltStart, pgnum, pgurlAltEnd)
resp, err = http.Get(u)
if err != nil {
log.Fatalf("Error downloading page %d, %s: %v\n", pgnum, u, err)
}
defer resp.Body.Close()
if resp.StatusCode != http.StatusOK {
log.Fatalf("Error downloading page %d, %s: HTTP Code %s\n", pgnum, u, resp.Status)
}
}
f, err := os.Create(fn)
defer f.Close()
if err != nil {
log.Fatalf("Error creating file %s: %v\n", fn, err)
}
_, err = io.Copy(f, resp.Body)
if err != nil {
log.Fatalf("Error writing file %s: %v\n", fn, err)
}
// Close once finished with, as defer won't trigger until the end of the function
resp.Body.Close()
f.Close()
// Check that the last two downloaded files aren't identical, as this
// can happen when there are no more pages to download.
if pgnum == 1 {
continue
}
fn2 := path.Join(bookdir, fmt.Sprintf("%04d.jpg", pgnum-1))
identical, err := filesAreIdentical(fn, fn2)
if err != nil {
log.Fatalf("Error checking for files being identical: %v\n", err)
}
if identical {
fmt.Println("Last 2 pages were identical, looks like it's the end of the book")
err = os.Remove(fn)
if err != nil {
log.Fatalf("Error removing dupilicate page %d: %v", fn, err)
}
return
}
}
}
}
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