;;; SPDX-License-Identifier: CC0-1.0
;;;
;;; Copyright (C) 2023, 2024 Wojtek Kosior <koszko@koszko.org>
(define-module (cantius)
#:use-module ((rnrs bytevectors) #:prefix bv:)
#:use-module ((srfi srfi-1) #:select (filter-map))
#:use-module ((srfi srfi-26) #:select (cut))
#:use-module ((srfi srfi-34) #:select (guard raise))
#:use-module ((srfi srfi-35) #:prefix s35:)
#:use-module ((srfi srfi-39) #:select (with-parameters*))
#:use-module ((srfi srfi-128) #:select (make-default-comparator))
#:use-module ((srfi srfi-146) #:prefix s146:)
#:use-module ((ice-9 format) #:select (format))
#:use-module ((ice-9 control) #:select (let/ec))
#:use-module ((ice-9 exceptions) #:select
(exception-with-message? exception-message))
#:use-module ((ice-9 regex) #:select
(match:substring match:end regexp-substitute/global))
#:use-module ((system repl debug) #:select (terminal-width))
#:use-module ((web http) #:select (read-headers))
#:use-module ((web request) #:select (request-uri))
#:use-module ((web response) #:select (build-response))
#:use-module ((web uri) #:prefix uri:)
#:use-module ((fibers web server) #:select (run-server))
#:use-module ((de-paul-records) #:select
(define-immutable-record-type* match match-let match-let*
match-lambda)))
(export ¬-found)
(export not-found-condition?)
(s35:define-condition-type ¬-found s35:&condition
not-found-condition?)
(export &forbidden)
(export forbidden-condition?)
(s35:define-condition-type &forbidden s35:&condition
forbidden-condition?)
(export &bad-request)
(export bad-request-condition?)
(s35:define-condition-type &bad-request s35:&condition
bad-request-condition?)
(export &condition-with-http-code)
(export condition-with-http-code?)
(export condition-http-code)
(s35:define-condition-type &condition-with-http-code s35:&condition
condition-with-http-code?
(http-code condition-http-code))
(define-public (normalize-path path)
(define absolute?
(eqv? #\/ (string-ref path 0)))
(let loop ((parent-walks 0)
(processed '())
(to-process (string-split path #\/)))
(match (list parent-walks processed to-process)
((0 () ())
(if absolute? "/" "."))
((_ _ ())
(string-join (append (map (const "..") (iota parent-walks))
(reverse processed))
"/"
(if absolute? 'prefix 'infix)))
((_ _ ((? (cut member <> '("" ".")))
. rest))
(loop parent-walks processed rest))
((_ () (".." . rest))
(loop (1+ parent-walks) '() rest))
((_ (_ . processed-rest) (".." . rest))
(loop parent-walks processed-rest rest))
((_ _ (segment . rest))
(loop parent-walks (cons segment processed) rest)))))
(define %illegal-path-regex
;; Assume normalized path, forbid parent directory ref.
(make-regexp "^/?[.][.](/.*)?$"))
(export find-resource-file)
(define* (find-resource-file file #:optional (root-path (%resource-root-path)))
(define normalized-file
(normalize-path file))
(when (regexp-exec %illegal-path-regex normalized-file)
(raise (s35:condition
(&forbidden)
(s35:&message
(message (format #f "Illegal resource path ~a" file))))))
(let loop ((paths root-path))
(match paths
(()
(raise (s35:condition
(¬-found)
(s35:&message
(message (format #f "Resource not found ~a" file))))))
((? string?)
(loop (list root-path)))
(((= (cut format #f "~a/~a" <> normalized-file) file-path)
. paths-rest)
(or (and (stat file-path #f) file-path)
(loop paths-rest))))))
;;;
;;; Multipart form parser
;;;
(define-immutable-record-type* form-data-part
#:export? #t
(name)
(headers)
(binary?)
(data))
(define (hex-escape bytestring)
(with-output-to-string
(lambda ()
(let loop ((idx 0))
(when (< idx (bv:bytevector-length bytestring))
(let ((byte (bv:bytevector-u8-ref bytestring idx)))
(cond ((or (> byte 127)
(= byte (char->integer #\\)))
(format #t "\\x~2,'0x" byte))
(else
(display (integer->char byte)))))
(loop (1+ idx)))))))
(define (hex-unescape string)
;; We assume a backslash is always followed by `x' and 2 digits (this is
;; indeed the case if the string has been generated by `hex-escape' above).
(define byte-length
(- (string-length string)
(* 3 (string-count string #\\))))
(define bytestring
(bv:make-bytevector byte-length))
(let loop ((byte-idx 0)
(str-idx 0))
(define (write-string str)
(string-fold (lambda (char char-idx)
(bv:bytevector-u8-set! bytestring char-idx
(char->integer char))
(1+ char-idx))
byte-idx str))
(match (string-contains string "\\x" str-idx)
(#f
(write-string (substring string str-idx))
bytestring)
((and (= (cut substring string str-idx <>) text-until)
escape-idx)
(let* ((byte-idx* (write-string text-until))
(str-idx* (+ 4 escape-idx))
(escape-hex (substring string (+ 2 escape-idx) str-idx*))
(byte (string->number escape-hex 16)))
(bv:bytevector-u8-set! bytestring byte-idx* byte)
(loop (1+ byte-idx*) str-idx*))))))
(define %part-regex
;; Headers, 2 new lines, actual data and one new line at the end.
(make-regexp "\r\n(([^\n]+\r\n)+\r\n)(.*)\r\n$"))
(define %backslash-regex
(make-regexp "\\\\"))
(define-public (parse-multipart/form-data boundary data)
;; `data' is a bytevector but Scheme lacks a `bytevector-contains' kind of
;; procedure so we instead convert our data to ASCII-only string (with
;; non-ASCII bytes expressed as hex escapes) and use regexes to split this
;; string around the occurences of boundary in O(n) time.
(define boundary*
;; A backslash is theoretically legal in boundary, let's make sure it's also
;; escaped.
(format #f "--~a"
(regexp-substitute/global #f %backslash-regex boundary
'pre "\\x5c" 'post)))
(define data*
(hex-escape data))
(define parts
(let loop ((idx 0)
(parts '()))
(match (string-contains data* boundary* idx)
(#f
(unless (string-prefix? "--\r\n" (substring data* idx))
(raise (s35:condition
(&bad-request)
(s35:&message
(message "Last boundary in multipart/form-data should end with extra double hyphen followed by CRLF")))))
;; Discard the last "part" (actually, the epilogue).
(reverse parts))
((and (= (cut substring data* idx <>) part)
(= (cut + <> (string-length boundary*)) idx*))
;; Discard the first "part" (actually, the preamble).
(loop idx* (if (= idx 0)
parts
(cons part parts)))))))
(map (lambda (part)
(match-let* (((and (= (cut match:substring <> 1) headers-string)
(= (cut match:substring <> 3) data))
(regexp-exec %part-regex part))
(headers
(call-with-input-string headers-string read-headers))
(('form-data . (= (cut assq-ref <> 'name)
(? string? name)))
(assq-ref headers 'content-disposition))
(content-transfer-encoding
(assq-ref headers 'content-transfer-encoding)))
(unless (member content-transfer-encoding '(#f "binary"))
(raise (s35:condition
(&condition-with-http-code
(http-code 415)) ;; Unsupported Media Type
(s35:&message
(message (format #f "Content-Transfer-Encoding of type \"~a\" is not currently supported for multipart/form-data parts, please use \"binary\" instead"
content-transfer-encoding))))))
(form-data-part
name
headers
(binary? (not (member (assq-ref headers 'content-type)
'(#f (text/plain)))))
(data (let ((data-binary (hex-unescape data)))
(if binary?
data-binary
(bv:utf8->string data-binary)))))))
parts))
;;;
;;; Cookie parser
;;;
(define %cookie-regex
(make-regexp (string-append
"^\\s*"
"([^[:space:];=]([^;=]*[^[:space:];=])?)" ;; name
"\\s*=\\s*"
"(([^[:space:];]([^;]*[^[:space:];])?)?)" ;; value
"\\s*(;|$)")))
(define-public (parse-cookies cookies)
(let loop ((idx 0)
(cookies-alist '()))
(match (regexp-exec %cookie-regex cookies idx)
(#f
(when (string-index cookies char-set:graphic idx)
(raise (s35:condition
(&bad-request)
(s35:&message
(message "Unparseable cookie")))))
(reverse cookies-alist))
((and (= (cut match:substring <> 1) name)
(= (cut match:substring <> 3) value)
(= match:end idx*))
(loop idx* `((,name . ,value) . ,cookies-alist))))))
(define-public %current-path
(make-parameter #f))
(define-public %current-path-string
(make-parameter #f))
(define-public %resource-root-path
(make-parameter '()))
(define-public %redirect/normalize-path?
(make-parameter #t))
(define-public %redirect/remove-query?
(make-parameter #t))
(define *%default-headers
'((content-type . (text/plain (charset . "utf-8")))))
(define-public %default-headers
(make-parameter *%default-headers))
(define (make-handler-parameter http-code default-message)
(make-parameter (lambda* (request body #:key message)
(values (build-response* #:headers *%default-headers
#:code http-code)
(or message default-message)))))
(define-public %not-found-handler
(make-handler-parameter 404 "There's no page with this address :("))
(define-public %forbidden-handler
(make-handler-parameter 403 "You. Shall not. Pass. (forbidden)"))
(define-public %bad-request-handler
(make-handler-parameter 400 "Bad Request (you or your software seems to have messed sth up)."))
(define-public %default-handler
(let ((not-found-handler (%not-found-handler)))
(make-parameter (lambda (request body . _)
(not-found-handler request body)))))
(define-public %other-codes-handler
(make-parameter (lambda* (request body http-code #:key message)
(values (build-response* #:headers *%default-headers
#:code http-code)
(or message
(format #f "HTTP code ~d" http-code))))))
(define-immutable-record-type* endpoint
(handler #:default (lambda _ (raise (s35:condition (s35:&error)))))
(path #:default '())
(parameters #:default '())
#:export? yes,of-course)
(define-immutable-record-type* endpoint-tree-node
(direct-match #:default #f)
(any-match #:default #f)
(children #:default (s146:mapping (make-default-comparator))))
(define-immutable-record-type* endset
(endpoints #:default (endpoint-tree-node))
(parameters #:default '())
#:export? sure,why-not)
(define (endpoint-tree-+ tree path what)
(let recurse ((segments path)
(tree-node tree))
(define (processed-segments)
(list-head path (- (length path) (length segments))))
(match-let ((($* endpoint-tree-node direct-match any-match children)
tree-node))
(when (endset? direct-match)
(raise (s35:condition
(s35:&error)
(s35:&message
(message (format #f "Endset already registered for ~s"
(processed-segments)))))))
(match segments
(()
(cond (direct-match
(raise (s35:condition
(s35:&error)
(s35:&message
(message (format #f "Endpoint already registered for ~s"
path))))))
((and (endset? what) (not (s146:mapping-empty? children)))
(raise (s35:condition
(s35:&error)
(s35:&message
(message (format #f "Endpoints already registered under ~s"
path))))))
(#t
(endpoint-tree-node
#:<- tree-node
(direct-match what)))))
('any
(cond (any-match
(raise (s35:condition
(s35:&error)
(s35:&message
(message (format #f "\"any\" endpoint already registered for ~s"
path))))))
((endset? what)
(raise (s35:condition
(s35:&error)
(s35:&message
(message (format #f "endset should be registered at normal path, not ~s"
path))))))
(#t
(endpoint-tree-node
#:<- tree-node
(any-match what)))))
(((? string? current-segment) . segments-rest)
(endpoint-tree-node
#:<- tree-node
(children (s146:mapping-update/default
children current-segment (cut recurse segments-rest <>)
%null-endpoint-tree-node))))))))
(define-public (endset-+ endset-obj path what)
(endset
#:<- endset-obj
(endpoints (endpoint-tree-+ (endset-endpoints endset-obj) path what))))
(eval-when (compile load eval)
(define-immutable-record-type* path-spec
(path-syntax)
(extra-handler-args-syntax))
(define (syntax->path-spec x)
(let loop ((path-segments '())
(path-syntax x))
(syntax-case path-syntax (unquote unquote-splicing)
(()
(path-spec (path-syntax #``(#,@(reverse path-segments)))
(extra-handler-args-syntax #'())))
(rest-arg
(identifier? #'rest-arg)
(path-spec (path-syntax #``(#,@(reverse path-segments) . any))
(extra-handler-args-syntax #'(rest-arg))))
((unquote list-expression)
(path-spec (path-syntax #``(#,@(reverse path-segments)
. ,list-expression))
(extra-handler-args-syntax #'())))
((segment-arg . rest)
(identifier? #'segment-arg)
(raise (s35:condition
(s35:&error)
(s35:&message
(message "Binding identifiers to path segments not yet supported")))))
(((unquote segment-expression) . rest)
(loop (cons #',segment-expression path-segments) #'rest))
(((unquote-splicing segments-expression) . rest)
(loop (cons #',@segments-expression path-segments) #'rest))
((segment . rest)
(string? (syntax->datum #'segment))
(loop (cons #'segment path-segments) #'rest))))))
(export define-endpoint)
(define-syntax define-endpoint
(lambda (x)
(syntax-case x ()
((_ endset-identifier handler-identifier path parameters-list
handler-body handler-body-rest ...)
(and (identifier? #'webservice-identifier)
(identifier? #'handler-identifier))
(match (syntax->path-spec #'path)
(($* path-spec path-syntax extra-handler-args-syntax)
#`(begin
(define (handler-identifier
#,(datum->syntax #'handler-identifier 'request)
#,(datum->syntax #'handler-identifier 'body)
. #,extra-handler-args-syntax)
handler-body handler-body-rest ...)
(define endset-identifier
(endset-+ endset-identifier #,path-syntax
(endpoint (parameters parameters-list)
(handler handler-identifier)))))))))))
(define-immutable-record-type* endpoint-ref-result
(path-tail)
(endpoint)
(parameters)
#:finalize (match-lambda
((and result ($* endpoint-ref-result (parameters #f) endpoint))
(let ((parameters (match endpoint
(($* endpoint parameters)
parameters)
(($* endset parameters)
parameters))))
(endpoint-ref-result #:<- result parameters)))
(result
result)))
(define (default-endpoint)
(endpoint (handler (%default-handler))
(parameters `((,%redirect/normalize-path? . #f)
(,%redirect/remove-query? . #f)))))
(define* (endpoint-tree-ref tree path #:key
(default-endpoint (default-endpoint)))
(let loop ((segments path)
(tree-node tree)
(best-any-match-endpoint default-endpoint)
(best-any-match-path #f))
(define (default-result)
(endpoint-ref-result (path-tail best-any-match-path)
(endpoint best-any-match-endpoint)))
(match segments
(()
(match tree-node
(($* endpoint-tree-node (direct-match (? identity endpoint)))
(endpoint-ref-result (path-tail #f) endpoint))
(_
(default-result))))
((current-segment . segments-rest)
(match-let* (((best-any-match-endpoint best-any-match-path)
(or (and=> (endpoint-tree-node-any-match tree-node)
(cut list <> segments))
(list best-any-match-endpoint best-any-match-path)))
(children (endpoint-tree-node-children tree-node))
(subnode (s146:mapping-ref/default children current-segment
#f)))
(cond (subnode
(loop segments-rest subnode
best-any-match-endpoint best-any-match-path))
(best-any-match-endpoint
(endpoint-ref-result (path-tail best-any-match-path)
(endpoint best-any-match-endpoint)))
(#t
(default-result))))))))
(define* (query-endset endset path #:optional (default #f))
(match-let loop ((($* endset endpoints (parameters endset-parameters)) endset)
(path path)
(parameters-lists '()))
(match (endpoint-tree-ref endpoints path)
(($* endpoint-ref-result
path-tail
(endpoint (? endset? next-endset)))
(loop next-endset path-tail (cons endset-parameters parameters-lists)))
(result
(endpoint-ref-result
#:<- result
(parameters #:-> (apply append (reverse (cons* parameters
endset-parameters
parameters-lists)))))))))
(export build-response*)
(define* (build-response* #:key (redirect-to #f) (headers (%default-headers))
(code #f) #:rest args)
(define code*
(or code (if redirect-to 301 200)))
(define redirect-to*
(if (string? redirect-to)
(uri:string->uri redirect-to)
redirect-to))
(define headers*
(if redirect-to*
`((location . ,redirect-to*) . ,headers)
headers))
(let loop ((to-filter args)
(filtered '()))
(match to-filter
(()
(apply build-response #:code code* #:headers headers*
(reverse filtered)))
(((? (cut memq <> '(#:code #:headers #:redirect-to))) _ . rest)
(loop rest filtered))
((keyword keyword-arg . rest)
(loop rest (cons* keyword-arg keyword filtered))))))
(define (%catchall-ref-result)
(endpoint-ref-result (path-tail #f)
(endpoint (endpoint (handler (%default-handler))))))
(define %ugly-uri-path-regex
(make-regexp ".+/(/|$)"))
(define (exception->msg ex)
(format #f "~a~%~a~%"
(if (exception-with-message? ex)
(format #f "Error: ~a." (exception-message ex))
"Error occured.")
ex))
(define (handler request body root-endset)
(define (bt-string)
(call-with-output-string (lambda (port)
(terminal-width 10000)
(display-backtrace (make-stack #t 5 0) port))))
(match-let* ((uri (request-uri request))
(path-string (uri:uri-path uri))
(path (uri:split-and-decode-uri-path path-string))
(($* endpoint-ref-result path-tail endpoint parameters)
(query-endset root-endset path (%catchall-ref-result))))
(define (normalized-uri-path-string)
(format #f "/~a" (uri:encode-and-join-uri-path path)))
(define (redirect-path)
(if (%redirect/normalize-path?)
(normalized-uri-path-string)
(uri:uri-path (request-uri request))))
(define (redirect-query)
(if (%redirect/remove-query?)
#f
(uri:uri-query uri)))
(define (compute-response)
(if (or (and (%redirect/normalize-path?)
(regexp-exec %ugly-uri-path-regex path-string))
(and (%redirect/remove-query?)
(uri:uri-query uri)))
(values (build-response* #:headers *%default-headers
#:redirect-to (uri:build-relative-ref
#:path (redirect-path)
#:query (redirect-query)))
"Redirect...")
(let/ec escape
(with-exception-handler
(lambda (ex)
(define msg
(exception->msg ex))
(display msg (current-error-port))
(escape (build-response* #:headers *%default-headers
#:code 500)
(string-append msg "\nBacktrace:\n\n" (bt-string))))
(lambda ()
(parameterize ((%current-path path)
(%current-path-string path-string))
(start-stack 'cantius-request
(guard (ex ((s35:condition-has-type? ex ¬-found)
((%not-found-handler) request body))
((s35:condition-has-type? ex &forbidden)
((%forbidden-handler) request body))
((s35:condition-has-type? ex &bad-request)
((%bad-request-handler) request body))
((s35:condition-has-type?
ex &condition-with-http-code)
((%other-codes-handler) request body
(condition-http-code ex)
#:message
(and (s35:condition-has-type? ex s35:&message)
(s35:condition-message ex)))))
(apply (endpoint-handler endpoint) request body
(or (and=> path-tail list) '()))))))))))
(with-parameters* (map car parameters) (map cdr parameters)
(lambda ()
(match ((compose list compute-response))
((response-body)
(values (build-response*) response-body))
((response response-body)
(values response response-body))
(something-else
(values (build-response* #:headers *%default-headers #:code 500)
(format #f "Invalid return values from handler:~%~a"
something-else))))))))
(define-public (run-cantius endset . server-args)
(apply run-server (cut handler <> <> endset) server-args))
