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// Copyright 2022 Nick White.
// Use of this source code is governed by the GPLv3
// license that can be found in the LICENSE file.
package main
import (
"context"
"encoding/json"
"fmt"
"io"
"io/ioutil"
"net/http"
"os"
"os/exec"
"path"
"strings"
"unicode"
"rescribe.xyz/bookpipeline/internal/pipeline"
)
const maxPartLength = 48
// formatAuthors formats a list of authors by just selecting
// the first one listed, and returning the uppercased final
// name.
func formatAuthors(authors []string) string {
if len(authors) == 0 {
return ""
}
s := authors[0]
parts := strings.Fields(s)
if len(parts) > 1 {
s = parts[len(parts)-1]
}
s = strings.ToUpper(s)
if len(s) > maxPartLength {
s = s[:maxPartLength]
}
s = strings.Map(stripNonLetters, s)
return s
}
// mapTitle is a function for strings.Map to strip out
// unwanted characters from the title.
func stripNonLetters(r rune) rune {
if !unicode.IsLetter(r) {
return -1
}
return r
}
// formatTitle formats a title to our preferences, notably
// by stripping spaces and punctuation characters.
func formatTitle(title string) string {
s := strings.Map(stripNonLetters, title)
if len(s) > maxPartLength {
s = s[:maxPartLength]
}
return s
}
// getMetadata queries Google Books for metadata we care about
// and returns it formatted as we need it.
func getMetadata(id string) (string, string, string, error) {
var author, title, year string
url := fmt.Sprintf("https://www.googleapis.com/books/v1/volumes/%s", id)
// designed to be unmarshalled by encoding/json's Unmarshal()
type bookInfo struct {
VolumeInfo struct {
Title string
Authors []string
PublishedDate string
}
}
resp, err := http.Get(url)
if err != nil {
return author, title, year, fmt.Errorf("Error downloading metadata %s: %v", url, err)
}
defer resp.Body.Close()
if resp.StatusCode != http.StatusOK {
return author, title, year, fmt.Errorf("Error downloading metadata %s: %v", url, err)
}
b, err := ioutil.ReadAll(resp.Body)
if err != nil {
return author, title, year, fmt.Errorf("Error reading metadata %s: %v", url, err)
}
v := bookInfo{}
err = json.Unmarshal(b, &v)
if err != nil {
return author, title, year, fmt.Errorf("Error parsing metadata %s: %v", url, err)
}
author = formatAuthors(v.VolumeInfo.Authors)
title = formatTitle(v.VolumeInfo.Title)
year = v.VolumeInfo.PublishedDate
return author, title, year, nil
}
// moveFile just copies a file to the destination without
// using os.Rename, as that can fail if crossing filesystem
// boundaries
func moveFile(from string, to string) error {
ffrom, err := os.Open(from)
if err != nil {
return err
}
defer ffrom.Close()
fto, err := os.Create(to)
if err != nil {
return err
}
defer fto.Close()
_, err = io.Copy(fto, ffrom)
if err != nil {
return err
}
ffrom.Close()
err = os.Remove(from)
if err != nil {
return err
}
return nil
}
// getGoogleBook downloads all images of a book to a directory
// named YEAR_AUTHORSURNAME_Title_bookid inside basedir, returning
// the directory path
func getGoogleBook(ctx context.Context, id string, basedir string) (string, error) {
author, title, year, err := getMetadata(id)
if err != nil {
return "", err
}
tmpdir, err := ioutil.TempDir("", "bookpipeline")
if err != nil {
return "", fmt.Errorf("Error setting up temporary directory: %v", err)
}
// TODO: use embedded version if necessary
cmd := exec.CommandContext(ctx, "getgbook", id)
pipeline.HideCmd(cmd)
cmd.Dir = tmpdir
cmd.Stdout = os.Stdout
cmd.Stderr = os.Stderr
err = cmd.Run()
if err != nil {
return "", fmt.Errorf("Error running getgbook %s: %v", id, err)
}
select {
case <-ctx.Done():
_ = os.Remove(tmpdir)
return "", ctx.Err()
default:
}
// getgbook downloads into id directory, so move files out of
// there directly into dir
tmpdir = path.Join(tmpdir, id)
f, err := os.Open(tmpdir)
if err != nil {
return "", fmt.Errorf("Failed to open %s to move files: %v", tmpdir, err)
}
files, err := f.Readdir(0)
if err != nil {
return "", fmt.Errorf("Failed to readdir %s to move files: %v", tmpdir, err)
}
d := fmt.Sprintf("%s_%s_%s_%s", year, author, title, id)
dir := path.Join(basedir, d)
err = os.MkdirAll(dir, 0755)
if err != nil {
return "", fmt.Errorf("Couldn't create directory %s: %v", dir, err)
}
for _, v := range files {
orig := path.Join(tmpdir, v.Name())
new := path.Join(dir, v.Name())
err = moveFile(orig, new)
if err != nil {
return dir, fmt.Errorf("Failed to move %s to %s: %v", orig, new, err)
}
}
err = os.Remove(tmpdir)
if err != nil {
return dir, fmt.Errorf("Failed to remove temporary directory %s: %v", tmpdir, err)
}
return dir, nil
}
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