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#lang racket
(require xml
(planet gh/http/request)
(planet gh/http/head)
;;; Some functions used by both SQS and SDB
;;; This module probably needs a better name/organization.
(define/contract/provide (post-with-retry uri xs-post-data heads [try 1])
((string? (listof (list/c symbol? string?)) dict?)
. ->* .
(define data (string->bytes/utf-8 (dict->form-urlencoded xs-post-data)))
(log-debug (tr "POST" data))
"1.1" "POST" uri data #f heads
(lambda (in h)
(define e (read-entity/xexpr in h))
(match (extract-http-code h)
[200 e]
(if (<= try 5)
(let ([sleep-time (sqr try)]) ;wait longer each time
(log-info (format "SDB returned 503. Try ~a in ~a secs."
(add1 try) sleep-time))
(sleep sleep-time)
(post-with-retry uri xs-post-data heads (add1 try)))
(error 'post-with-retry "too many 503 retries; giving up"))]
(raise (header&response->exn:fail:aws
h e (current-continuation-marks)))]))))
(define/provide (set-next-token params token)
(cons (list 'NextToken token)
(filter (lambda (x) (not (equal? (car x) 'NextToken)))
(define/provide (timestamp [seconds (current-seconds)])
(seconds->gmt-8601-string 'T/Z seconds))
;; SDB docs:
;; "To ensure that you can read all the data you sent via REST, if a
;; response contains invalid XML characters, Amazon SimpleDB
;; automatically Base64-encodes the UTF-8 octets of the text."
;; Example:
;; <Attribute>
;; <Name encoding="base64">...</Name>
;; <Value encoding="base64">...</Value>
;; </Attribute>
;; "When designing your application, make sure to scrub any data for
;; invalid characters or design your application to handle
;; Base64-encoded results."
(define/contract/provide (attribute-xexpr->attrib-pair x)
(xexpr? . -> . (list/c symbol? string?))
;; (Attribute () (Name () x) (Value () x))
(match x
[(list 'Attribute _ name val)
(let ([name (maybe-decode name)]
[val (maybe-decode val)])
(list (if (string? name) (string->symbol name) name)
(define/provide (maybe-decode x)
(match x
[(list (or 'Name 'Value) attrs val)
(match (assoc 'Encoding attrs)
[(list 'Encoding "base64") (base64-decode val)]
[else val])]))
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