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chore: import upstream snapshot with attribution
2026-07-13 12:16:49 +08:00

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package util
import (
"math/rand/v2"
"strings"
pdf "ragflow/internal/deepdoc/parser/pdf/type"
)
// IsASCIIPrintable returns true for characters that match Python's
// is_english regex: [ a-zA-Z0-9,/¸;:'\[\]\(\)!@#$%^&*\"?<>._-]
func IsASCIIPrintable(r rune) bool {
if r == ' ' {
return true
}
if r >= 'a' && r <= 'z' {
return true
}
if r >= 'A' && r <= 'Z' {
return true
}
if r >= '0' && r <= '9' {
return true
}
// Additional ASCII symbols from the Python regex
switch r {
case ',', '/', '¸', ';', ':', '\'', '[', ']', '(', ')',
'!', '@', '#', '$', '%', '^', '&', '*', '"', '?',
'<', '>', '.', '_', '-':
return true
}
return false
}
// DefaultSampleChars returns a random sample of up to n character texts,
// concatenated. Matches Python's random.choices([c["text"] for c in
// page_chars], k=min(100, len(page_chars))).
func DefaultSampleChars(chars []pdf.TextChar, n int) string {
if n <= 0 || len(chars) == 0 {
return ""
}
m := min(n, len(chars))
// Fisher-Yates shuffle on indices, then take first m.
indices := make([]int, len(chars))
for i := range indices {
indices[i] = i
}
rand.Shuffle(len(indices), func(i, j int) {
indices[i], indices[j] = indices[j], indices[i]
})
var buf strings.Builder
for i := 0; i < m; i++ {
buf.WriteString(chars[indices[i]].Text)
}
return buf.String()
}
// FullTextFromChars concatenates all chars text across pages for scan noise detection.
func FullTextFromChars(pageChars map[int][]pdf.TextChar) string {
var sb strings.Builder
for _, chars := range pageChars {
for _, c := range chars {
sb.WriteString(c.Text)
}
}
return sb.String()
}
// DetectEnglishPage reports whether one page contains a run of 30+
// consecutive ASCII-printable characters in a random sample of up to 100
// extracted character texts.
func DetectEnglishPage(chars []pdf.TextChar, sample pdf.SampleFunc) bool {
if len(chars) == 0 {
return false
}
if sample == nil {
sample = DefaultSampleChars
}
sampleText := sample(chars, 100)
run := 0
for _, r := range sampleText {
if IsASCIIPrintable(r) {
run++
if run >= 30 {
return true
}
} else {
run = 0
}
}
return false
}
// DetectEnglish detects whether a PDF is primarily English by per-page
// majority vote, matching Python's is_english logic in __images__
// (pdf_parser.py:1519-1526).
//
// Each page votes via DetectEnglishPage. Returns true when a strict majority
// of pages vote yes. totalPages remains the denominator so image-only pages
// still dilute the majority, matching Python behavior.
func DetectEnglish(pageChars map[int][]pdf.TextChar, totalPages int, sample pdf.SampleFunc) bool {
if totalPages == 0 || len(pageChars) == 0 {
return false
}
pagesWithSeq := 0
for _, chars := range pageChars {
if DetectEnglishPage(chars, sample) {
pagesWithSeq++
}
}
return pagesWithSeq > totalPages/2
}