Jānis Kacēns
63 lines
1.4 KiB
Go
63 lines
1.4 KiB
Go
package parse
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import (
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"bytes"
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"errors"
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"fmt"
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"io"
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"strings"
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"unicode"
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"github.com/ledongthuc/pdf"
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)
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// ErrScanPDF is returned when extracted text is empty or non-textual,
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// indicating a scan-based (image-only) PDF that cannot be parsed.
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var ErrScanPDF = errors.New("scan-based PDF: please convert to text first")
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// ExtractPDF reads a PDF and returns its concatenated plain text.
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// Returns ErrScanPDF if the content appears to be empty or non-textual.
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func ExtractPDF(r io.Reader) (string, error) {
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data, err := io.ReadAll(r)
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if err != nil {
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return "", fmt.Errorf("read pdf: %w", err)
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}
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reader, err := pdf.NewReader(bytes.NewReader(data), int64(len(data)))
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if err != nil {
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return "", fmt.Errorf("parse pdf: %w", err)
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}
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var sb strings.Builder
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for i := 1; i <= reader.NumPage(); i++ {
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page := reader.Page(i)
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if page.V.IsNull() {
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continue
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}
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text, err := page.GetPlainText(nil)
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if err != nil {
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continue
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}
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sb.WriteString(text)
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sb.WriteByte('\n')
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}
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text := sb.String()
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if isGibberish(text) {
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return "", ErrScanPDF
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}
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return text, nil
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}
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// isGibberish returns true when text is too short or has < 2% alphanumeric content.
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func isGibberish(text string) bool {
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runes := []rune(text)
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if len(runes) < 50 {
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return true
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}
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var alpha int
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for _, c := range runes {
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if unicode.IsLetter(c) || unicode.IsDigit(c) {
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alpha++
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}
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}
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return float64(alpha)/float64(len(runes)) < 0.02
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}
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