姚章浩
66 lines
1.7 KiB
Go
66 lines
1.7 KiB
Go
package outboundimage
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import (
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"context"
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"regexp"
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"strings"
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)
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var resourceMarkdownImageRE = regexp.MustCompile(`!\[[^\]]*\]\((resource://[0-9A-Za-z_-]+)\)`)
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type Fetcher interface {
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Fetch(ctx context.Context, reference string) ([]byte, string, error)
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}
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type Publisher interface {
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Publish(ctx context.Context, data []byte, contentType string) (string, error)
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}
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type Rewriter struct {
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fetcher Fetcher
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publisher Publisher
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maxImages int
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}
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func NewRewriter(fetcher Fetcher, publisher Publisher, maxImages int) *Rewriter {
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return &Rewriter{fetcher: fetcher, publisher: publisher, maxImages: maxImages}
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}
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func (r *Rewriter) Rewrite(ctx context.Context, markdown string) string {
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if r == nil || r.fetcher == nil || r.publisher == nil || r.maxImages <= 0 {
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return resourceMarkdownImageRE.ReplaceAllString(markdown, "")
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}
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urls := map[string]string{}
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attempted := 0
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return resourceMarkdownImageRE.ReplaceAllStringFunc(markdown, func(image string) string {
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match := resourceMarkdownImageRE.FindStringSubmatch(image)
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if len(match) != 2 {
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return ""
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}
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reference := match[1]
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if signedURL, ok := urls[reference]; ok {
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if signedURL == "" {
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return ""
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}
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return strings.Replace(image, reference, signedURL, 1)
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}
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if attempted >= r.maxImages {
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urls[reference] = ""
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return ""
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}
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attempted++
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data, contentType, err := r.fetcher.Fetch(ctx, reference)
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if err != nil {
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urls[reference] = ""
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return ""
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}
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signedURL, err := r.publisher.Publish(ctx, data, contentType)
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if err != nil || !strings.HasPrefix(signedURL, "https://") {
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urls[reference] = ""
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return ""
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}
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urls[reference] = signedURL
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return strings.Replace(image, reference, signedURL, 1)
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})
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}
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