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imgbundler.go
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/
imgbundler.go
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package imgbundler
import (
"bytes"
"context"
"encoding/base64"
"fmt"
"io/ioutil"
"mime"
"net/http"
"net/url"
"os"
"path"
"regexp"
"strings"
"sync"
"time"
"golang.org/x/xerrors"
"oss.terrastruct.com/util-go/xdefer"
"oss.terrastruct.com/util-go/xmain"
)
const maxImageSize int64 = 1 << 25 // 33_554_432
var imageRegex = regexp.MustCompile(`<image href="([^"]+)"`)
func BundleLocal(ctx context.Context, ms *xmain.State, in []byte) ([]byte, error) {
return bundle(ctx, ms, in, false)
}
func BundleRemote(ctx context.Context, ms *xmain.State, in []byte) ([]byte, error) {
return bundle(ctx, ms, in, true)
}
type repl struct {
from []byte
to []byte
}
func bundle(ctx context.Context, ms *xmain.State, svg []byte, isRemote bool) (_ []byte, err error) {
if isRemote {
defer xdefer.Errorf(&err, "failed to bundle remote images")
} else {
defer xdefer.Errorf(&err, "failed to bundle local images")
}
imgs := imageRegex.FindAllSubmatch(svg, -1)
imgs = filterImageElements(imgs, isRemote)
ctx, cancel := context.WithTimeout(ctx, time.Minute*5)
defer cancel()
return runWorkers(ctx, ms, svg, imgs, isRemote)
}
// filterImageElements finds all image elements in imgs that are eligible
// for bundling in the current context.
func filterImageElements(imgs [][][]byte, isRemote bool) [][][]byte {
imgs2 := imgs[:0]
for _, img := range imgs {
href := string(img[1])
// Skip already bundled images.
if strings.HasPrefix(href, "data:") {
continue
}
u, err := url.Parse(href)
isRemoteImg := err == nil && strings.HasPrefix(u.Scheme, "http")
if isRemoteImg == isRemote {
imgs2 = append(imgs2, img)
}
}
return imgs2
}
func runWorkers(ctx context.Context, ms *xmain.State, svg []byte, imgs [][][]byte, isRemote bool) (_ []byte, err error) {
var wg sync.WaitGroup
replc := make(chan repl)
wg.Add(len(imgs))
go func() {
wg.Wait()
close(replc)
}()
// Limits the number of workers to 16.
sema := make(chan struct{}, 16)
var errhrefsMu sync.Mutex
var errhrefs []string
// Start workers as the sema allows.
go func() {
for _, img := range imgs {
img := img
sema <- struct{}{}
go func() {
defer func() {
wg.Done()
<-sema
}()
bundledImage, err := worker(ctx, img[1], isRemote)
if err != nil {
ms.Log.Error.Printf("failed to bundle %s: %v", img[1], err)
errhrefsMu.Lock()
errhrefs = append(errhrefs, string(img[1]))
errhrefsMu.Unlock()
return
}
select {
case <-ctx.Done():
case replc <- repl{
from: img[0],
to: bundledImage,
}:
}
}()
}
}()
t := time.NewTicker(time.Second * 5)
defer t.Stop()
for {
select {
case <-ctx.Done():
return svg, xerrors.Errorf("failed to wait for workers: %w", ctx.Err())
case <-t.C:
ms.Log.Info.Printf("fetching images...")
case repl, ok := <-replc:
if !ok {
if len(errhrefs) > 0 {
return svg, xerrors.Errorf("%v", errhrefs)
}
return svg, nil
}
svg = bytes.Replace(svg, repl.from, repl.to, 1)
}
}
}
func worker(ctx context.Context, href []byte, isRemote bool) ([]byte, error) {
var buf []byte
var mimeType string
var err error
if isRemote {
buf, mimeType, err = httpGet(ctx, string(href))
} else {
buf, err = os.ReadFile(string(href))
}
if err != nil {
return nil, err
}
if mimeType == "" {
mimeType = sniffMimeType(href, buf, isRemote)
}
mimeType = strings.Replace(mimeType, "text/xml", "image/svg+xml", 1)
b64 := base64.StdEncoding.EncodeToString(buf)
return []byte(fmt.Sprintf(`<image href="data:%s;base64,%s"`, mimeType, b64)), nil
}
var httpClient = &http.Client{}
func httpGet(ctx context.Context, href string) ([]byte, string, error) {
ctx, cancel := context.WithTimeout(ctx, time.Minute)
defer cancel()
req, err := http.NewRequestWithContext(ctx, "GET", href, nil)
if err != nil {
return nil, "", err
}
resp, err := httpClient.Do(req)
if err != nil {
return nil, "", err
}
defer resp.Body.Close()
if resp.StatusCode != 200 {
return nil, "", fmt.Errorf("expected status 200 but got %d %s", resp.StatusCode, resp.Status)
}
r := http.MaxBytesReader(nil, resp.Body, maxImageSize)
buf, err := ioutil.ReadAll(r)
if err != nil {
return nil, "", err
}
return buf, resp.Header.Get("Content-Type"), nil
}
// sniffMimeType sniffs the mime type of href based on its file extension and contents.
func sniffMimeType(href, buf []byte, isRemote bool) string {
p := string(href)
if isRemote {
u, err := url.Parse(p)
if err != nil {
p = ""
} else {
p = u.Path
}
}
mimeType := mime.TypeByExtension(path.Ext(p))
if mimeType == "" {
mimeType = http.DetectContentType(buf)
}
return mimeType
}