96 lines
2.0 KiB
Go
96 lines
2.0 KiB
Go
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package deadlinks
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import (
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"bufio"
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"errors"
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"fmt"
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"io"
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"strings"
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"sync"
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)
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// Parser is a thread-safe type which can parse URLs out of the body of a file,
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// using a mimeType to determine what kind of file it is.
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//
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// The returned URLs may be either relative or absolute, and may or may not
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// include other URL elements like scheme, host, etc...
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//
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// It is not required that the Parser fully reads the body io.Reader.
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//
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// If an error is returned then some set of URLs may still be returned.
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type Parser interface {
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Parse(mimeType string, body io.Reader) ([]URL, error)
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}
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type parser struct {
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brPool sync.Pool
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}
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// NewParser returns a basic Parser supporting some commonly used document
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// types which support hyperlinks. The returned Parser will return an empty URL
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// set for all unsupported MIME types.
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//
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// Supported MIME types:
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// - text/gemtext
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// - text/html (TODO)
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// - application/rss+xml (TODO)
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// - application/atom+xml (TODO)
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func NewParser() Parser {
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return &parser{
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brPool: sync.Pool{
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New: func() any { return bufio.NewReader(nil) },
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},
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}
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}
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func parseGemtext(body *bufio.Reader) ([]URL, error) {
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var (
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urls []URL
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errs []error
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)
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for {
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line, err := body.ReadString('\n')
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if strings.HasPrefix(line, "=> ") {
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if parts := strings.Fields(line); len(parts) >= 2 {
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u, err := ParseURL(parts[1])
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if err != nil {
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errs = append(errs, fmt.Errorf(
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"parsing URL from line %q: %w", line, err,
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))
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continue
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}
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urls = append(urls, u)
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}
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}
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if errors.Is(err, io.EOF) {
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break
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} else if err != nil {
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errs = append(errs, err)
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break
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}
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}
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return urls, errors.Join(errs...)
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}
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var parsersByMimeType = map[string]func(*bufio.Reader) ([]URL, error){
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"text/gemini": parseGemtext,
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}
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func (p *parser) Parse(mimeType string, body io.Reader) ([]URL, error) {
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fn, ok := parsersByMimeType[mimeType]
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if !ok {
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return nil, nil
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}
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br := p.brPool.Get().(*bufio.Reader)
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br.Reset(body)
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defer p.brPool.Put(br)
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return fn(br)
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}
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