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#lang racket
(module+ test
(require rackunit))
;; Convenience macros to define, contract, and/or provide (i.e. other
;; permutations of those, like the standard define/contract).
(define-syntax define/contract/provide
(syntax-rules ()
[(_ (id . args) contract body ...)
(define/contract (id . args) contract body ...)
(provide/contract [id contract]))]
[(_ id contract expr)
(define/contract id contract expr)
(provide/contract [id contract]))] ))
(define-syntax define/provide
(syntax-rules ()
[(_ (id . args) body ...)
(define (id . args) body ...)
(provide id))]
[(_ id expr)
(define id expr)
(provide id))] ))
(provide define/contract/provide
;; NOTE: This predates racket/format and could probably be obsoleted.
;; (any/c ... -> string?) Given any number of Racket identifiers or
;; literals, convert them to a string. Non-literals are printed as
;; "expression = value". For use with e.g. log-debug which takes a
;; single string? not format or printf style, plus, we want to show
;; the expression = value thing.
(define-syntax tr
(syntax-rules ()
[(_ e)
(if (or (string? (syntax-e #'e))
(number? (syntax-e #'e)))
(format "~a" e)
(format "~s=~a"
(syntax->datum #'e)
[(_ e0 e1 ...)
(string-append (tr e0)
" "
(tr e1 ...))]))
(provide tr)
(require xml)
(define/contract/provide (tags xpr tag [direct-child-of #f])
((xexpr/c symbol?)
. ->* . (listof xexpr/c))
;; Given an xexpr return a list of all the elements starting with
;; tag, at any depth. Even if a tag is nested inside the same tag,
;; which is great for e.g. HTML, and convienent for certain known
;; XML responses, but be careful using this with arbitrary XML.
(define (do xpr parent)
(cond [(empty? xpr) '()]
(define this-xpr (first xpr))
(cond [(and (list? this-xpr)
(not (empty? this-xpr)))
(define this-tag (first this-xpr))
(define found? (and (equal? this-tag tag)
(or (not direct-child-of)
(equal? direct-child-of parent))))
(append (cond [found? (list this-xpr)] ;found one!
[else '()])
(do this-xpr this-tag) ;down
(do (rest xpr) parent))] ;across
(do (rest xpr) parent)])])) ;across
(do xpr #f))
(define/provide (first-tag-value x t [def #f])
;; Given a (listof xexpr?), return just the value of the first
;; element with tag `t`.
(match (tags x t)
['() def]
[(list (list _ v) ...) (first v)]
[(list (list _ _ v) ...) (first v)]
[else def]))
;; attribs <-> alist.
;; Former is (list/c symbol? string?), latter is (cons/c symbol? string?).
;; Although alists are standard Scheme/Racket fare, with xexprs we want
;; attribs, so will need to convert between sometimes.
(define/provide (attribs->alist xs)
(define (list->cons xs)
(match xs
[(list k v) (cons k v)]
[else (error 'attribs->alist "expected list of 2 items, got ~a" xs)]))
(map list->cons xs))
(module+ test
(check-exn exn:fail? (lambda () (attribs->alist '([a 1 more]))))
(check-equal? (attribs->alist '([a 1] [b 2])) '([a . 1][b . 2])))
(define/provide (alist->attribs xs)
(define (cons->list pr)
(match pr
[(cons k v) (list k v)]
[else (error 'alist->attribs "expected cons, got ~a" pr)]))
(map cons->list xs))
(module+ test
(check-equal? (alist->attribs '([a . 1][b . 2])) '([a 1] [b 2])))
;; Percent-encoding. Racket net/uri-codec does RFC 2396 but we want
;; RFC 3986.
(require net/uri-codec)
(define (percent-encode c)
(string-upcase (format "%~x" (char->integer c))))
(define (char->pair c)
(cons c (percent-encode c)))
;; The extra chars that uri-encode misses but 3986 wants
(define chars-to-encode (list #\! #\'#\(#\) #\*))
(define h (for/hash ([c (in-list chars-to-encode)])
(values c (percent-encode c))))
(define/provide (uri-encode/rfc-3986 s)
(for/fold ([accum ""])
([c (in-string (uri-encode s))])
(string-append accum (hash-ref h c (make-string 1 c)))))
;; Like Racket alist->form-urlencoded, but:
;; 1. Works on any dict? (not just an association list of cons pairs).
;; 2. Uses RFC 3986 encoding.
;; 3. The values can by any/c not just string?. Their ~a format is used.
(define/contract/provide (dict->form-urlencoded xs)
(dict? . -> . string?)
(define (value x)
(match x
[(list v) (value v)] ;permit [k v] not just [k . v]
[(var v) (format "~a" v)]))
(string-join (for/list ([(k v) (in-dict xs)])
(format "~a=~a"
(uri-encode/rfc-3986 (value v))))
(struct endpoint (host ssl?) #:transparent)
(provide (struct-out endpoint))
(define/contract/provide (endpoint->host:port x)
(endpoint? . -> . string?)
(match-define (endpoint host ssl?) x)
(string-append host (if ssl? ":443" "")))
(define/contract/provide (endpoint->uri x path)
(endpoint? string? . -> . string?)
(match-define (endpoint host ssl?) x)
(string-append (if ssl? "https" "http")
(if ssl? ":443" "")
(require "take.rkt")
;; Much like `hash' lets you supply the pairs as a flat list, `alist'
;; lets you do so for an association list. Saves some tedious typing
;; of parens and dots.
(define/provide (alist . xs)
(for/list ([(k v) (in-take xs 2)])
(cons k v)))
(module+ test
(define xs '([a . 1][b . 2]))
(check-equal? (alist 'a 1 'b 2) xs)
(check-equal? (apply alist '(a 1 b 2)) xs))
;; Given a list of couples k0 v0 k1 v1 ... kN vN, return the k v couples
;; where v is not #f.
(define/provide (true-value-pairs . xs)
(flatten (for/list ([(k v) (in-take xs 2)]
#:when v)
(list k v))))
(module+ test
(check-equal? (true-value-pairs 'a 1 'b #f 'c 2)
(list 'a 1 'c 2)))
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