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#lang racket/base
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(require racket/match)
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(require "../tools.rkt" "../predicates.rkt" sugar txexpr/fast)
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(provide (all-defined-out))
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;; This module is a library of functions to be used in building pollen decoders.
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;; Typography
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;; insert typographic niceties
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;; ligatures are handled in css
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(define (typogrify str)
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;; make set of functions for replacers
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(define (make-replacer query replacement)
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(λ(str) (regexp-replace* query str replacement)))
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;; just store the query strings + replacement strings
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(define dashes
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;; fix em dashes first, else they'll be mistaken for en dashes
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;; [\\s ] is whitespace + nonbreaking space
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'((#px"[\\s ]*(---|—)[\\s ]*" "—") ; em dash
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(#px"[\\s ]*(--|–)[\\s ]*" "–"))) ; en dash
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(define smart-quotes
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'((#px"(?<=\\w)'(?=\\w)" "’") ; apostrophe
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(#px"(?<!\\w)'(?=\\w)" "‘") ; single_at_beginning
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(#px"(?<=\\S)'(?!\\w)" "’") ; single_at_end
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(#px"(?<!\\w)\"(?=\\w)" "“") ; double_at_beginning
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(#px"(?<=\\S)\"(?!\\w)" "”"))) ; double_at_end
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;; put replacers in desired order here
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(let* ([typogrifiers (append dashes smart-quotes)]
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[queries (map first typogrifiers)]
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[replacements (map second typogrifiers)])
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(define replacers (map make-replacer queries replacements))
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;; compose goes from last to first, so reverse order
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((apply compose1 (reverse replacers)) str)))
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;; insert nbsp between last two words
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(define (nonbreaking-last-space x
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#:nbsp [nbsp (->string #\u00A0)]
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#:minimum-word-length [minimum-word-length 6])
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;; todo: parameterize this, as it will be different for each project
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(define tags-to-pay-attention-to '(p aside)) ; only apply to paragraphs
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(define (replace-last-space str)
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(if (#\space . in? . str)
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(let ([reversed-str-list (reverse (string->list str))]
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[reversed-nbsp (reverse (string->list nbsp))])
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(define-values (last-word-chars other-chars)
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(splitf-at reversed-str-list (λ(i) (not (eq? i #\space)))))
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(list->string (reverse (append last-word-chars
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; OK for long words to be on their own line.
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(if (< (len last-word-chars) minimum-word-length)
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; first char of other-chars will be the space, so use cdr
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(append reversed-nbsp (cdr other-chars))
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other-chars)))))
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str))
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(define (find-last-word-space x) ; recursively traverse xexpr
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(cond
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[(string? x) (replace-last-space x)]
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[(txexpr? x)
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(let-values([(tag attr elements) (txexpr->values x)])
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(if (> (length elements) 0) ; elements is list of xexprs
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(let-values ([(all-but-last last) (split-at elements (sub1 (length elements)))])
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(make-txexpr tag attr `(,@all-but-last ,(find-last-word-space (car last)))))
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x))]
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[else x]))
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(if ((car x) . in? . tags-to-pay-attention-to)
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(find-last-word-space x)
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x))
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; wrap initial quotes for hanging punctuation
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; todo: improve this
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; does not handle <p>“<em>thing</em> properly
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(define (wrap-hanging-quotes nx
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#:single-prepend [single-pp '(squo)]
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#:double-prepend [double-pp '(dquo)])
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(define two-or-more-char-string? (λ(i) (and (string? i) (>= (len i) 2))))
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(define-values (tag attr elements) (txexpr->values nx))
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(make-txexpr tag attr
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(if (and (list? elements) (not (empty? elements)))
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(let ([new-car-elements (match (car elements)
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[(? two-or-more-char-string? tcs)
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(define str-first (get tcs 0))
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(define str-rest (get tcs 1 'end))
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(cond
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[(str-first . in? . '("\"" "“"))
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;; can wrap with any inline tag
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;; so that linebreak detection etc still works
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`(,@double-pp ,(->string #\“) ,str-rest)]
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[(str-first . in? . '("\'" "‘"))
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`(,@single-pp ,(->string #\‘) ,str-rest)]
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[else tcs])]
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[(? txexpr? nx) (wrap-hanging-quotes nx)]
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[else (car elements)])])
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(cons new-car-elements (cdr elements)))
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elements)))
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;; Lines, blocks, paragraphs
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;; turn the right items into <br> tags
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(define (convert-linebreaks xc #:newline [newline "\n"])
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;; todo: should this test be not block + not whitespace?
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(define not-block? (λ(i) (not (block-xexpr? i))))
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(filter-not empty?
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(for/list ([i (len xc)])
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(let ([item (get xc i)])
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(cond
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;; skip first and last
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[(or (= i 0) (= i (sub1 (len xc)))) item]
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[(equal? item newline)
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(match (get xc (- i 1) (+ i 2)) ; a three-element slice with x[i] in the middle
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;; only convert if neither adjacent tag is a block
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;; (because blocks automatically force a newline before & after)
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[(list (? not-block?) newline (? not-block?)) '(br)]
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[else empty])] ; otherwise delete
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[else item])))))
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;; recursive whitespace test
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(define (whitespace? x)
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(cond
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[(equal? "" x) #t] ; empty string is deemed whitespace
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[(or (string? x) (symbol? x)) (->boolean (regexp-match #px"^\\s+$" (->string x)))]
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[(or (list? x) (vector? x)) (andmap whitespace? (->list x))]
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[else #f]))
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;; is x a paragraph break?
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(define (paragraph-break? x #:pattern [paragraph-pattern #px"^\n\n+$"])
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(and (string? x) (->boolean (regexp-match paragraph-pattern x))))
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;; Find adjacent newline characters in a list and merge them into one item
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;; Scribble, by default, makes each newline a separate list item
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;; In practice, this is worthless.
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(define (merge-newlines x)
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(define (newline? x)
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(and (string? x) (equal? "\n" x)))
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(define (not-newline? x)
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(not (newline? x)))
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(define (really-merge-newlines xs [acc '()])
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(if (empty? xs)
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acc
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;; Try to peel the newlines off the front.
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(let-values ([(leading-newlines remainder) (splitf-at xs newline?)])
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(if (not (empty? leading-newlines)) ; if you got newlines ...
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;; combine them into a string and append them to the accumulator,
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;; and recurse on the rest
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(really-merge-newlines remainder (append acc (list (apply string-append leading-newlines))))
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;; otherwise peel off elements up to the next newline, append them to accumulator,
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;; and recurse on the rest
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(really-merge-newlines (dropf remainder not-newline?)
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(append acc (takef remainder not-newline?)))))))
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(cond
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[(list? x) (really-merge-newlines (map merge-newlines x))]
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[else x]))
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;; todo: add native support for list-xexpr
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;; decode triple newlines to list items
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;; prepare elements for paragraph testing
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(define (prep-paragraph-flow xc)
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(convert-linebreaks (merge-newlines (trim xc whitespace?))))
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;; apply paragraph tag
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(define (wrap-paragraph xc #:tag [tag 'p])
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(match xc
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[(list (? block-xexpr? bx)) bx] ; leave a single block xexpr alone
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[else (make-txexpr tag empty xc)])) ; otherwise wrap in p tag
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;; detect paragraphs
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;; todo: unit tests
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(define (detect-paragraphs elements)
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(let ([elements (prep-paragraph-flow elements)])
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(if (ormap paragraph-break? elements) ; need this condition to prevent infinite recursion
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(map wrap-paragraph (splitf-at* elements paragraph-break?)) ; split into ¶¶
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elements))) |