;; disfluid, implementation of the Solid specification
;; Copyright (C) 2020, 2021  Vivien Kraus

;; This program is free software: you can redistribute it and/or modify
;; it under the terms of the GNU Affero General Public License as
;; published by the Free Software Foundation, either version 3 of the
;; License, or (at your option) any later version.

;; This program is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;; GNU Affero General Public License for more details.

;; You should have received a copy of the GNU Affero General Public License
;; along with this program.  If not, see <https://www.gnu.org/licenses/>.

(define-module (webid-oidc client)
  #:use-module (webid-oidc errors)
  #:use-module (webid-oidc provider-confirmation)
  #:use-module (webid-oidc oidc-id-token)
  #:use-module (webid-oidc dpop-proof)
  #:use-module (webid-oidc jwk)
  #:use-module ((webid-oidc parameters) #:prefix p:)
  #:use-module ((webid-oidc stubs) #:prefix stubs:)
  #:use-module ((webid-oidc config) #:prefix cfg:)
  #:use-module ((webid-oidc cache) #:prefix cache:)
  #:use-module ((webid-oidc client accounts) #:prefix account:)
  #:use-module ((webid-oidc client client) #:prefix client:)
  #:use-module (web uri)
  #:use-module (web request)
  #:use-module (web response)
  #:use-module (web server)
  #:use-module (web http)
  #:use-module (ice-9 optargs)
  #:use-module (ice-9 receive)
  #:use-module (srfi srfi-9)
  #:use-module (srfi srfi-19)
  #:use-module (srfi srfi-26)
  #:use-module (rnrs bytevectors)
  #:use-module (ice-9 i18n)
  #:use-module (ice-9 getopt-long)
  #:use-module (ice-9 suspendable-ports)
  #:use-module (ice-9 match)
  #:use-module (sxml simple)
  #:use-module (oop goops)
  #:re-export
  (
   (client:<client> . <client>)
   (client:client-id . client-id)
   (client:key-pair . key-pair)
   (client:redirect-uri . redirect-uri)

   (client:client . client)
   (account:authorization-process . authorization-process)
   (account:authorization-state . authorization-state)
   )
  #:export
  (
   request

   serve-application
   )
  #:declarative? #t)

;; For syntax highlighting
(define <account:account> account:<account>)
(define <client:client> client:<client>)

(define (setup-headers!)
  ;; HACK: guile does not support other authentication schemes in
  ;; WWW-Authenticate than Basic, so it will crash when a response
  ;; containing that header will be issued.
  (declare-header!
   "WWW-Authenticate"
   (cute parse-header 'pragma <>)
   (lambda (value)
     (and (list? value)
          (let check-value ((schemes value))
            (match schemes
              (() #t)
              (((hd . args) tl ...)
               (and (symbol? hd)
                    (let check-args ((args args))
                      (match args
                        (() #t)
                        (((key . value) tl ...)
                         (and (symbol? key)
                              (string? value)
                              (check-args tl)))))
                    (check-value tl)))))))
   (cute write-header 'pragma <> <>))
  ;; The same applies for the authorization header.
  (let ((original-parser (header-parser 'authorization))
        (original-writer (header-writer 'authorization)))
    (declare-header!
     "Authorization"
     original-parser
     (lambda (value) #t)
     (match-lambda*
       ((('dpop . dpop) port)
        (format port "DPoP ~a" dpop))
       ((value port)
        (original-writer value port))))))

(define* (initial-login client issuer)
  (setup-headers!)
  (parameterize ((client:client client))
    (make <account:account>
      #:issuer issuer)))

(define (request account uri . other-args)
  (setup-headers!)
  (unless (account:access-token account)
    (set! account (account:refresh account)))
  (define (do-with-headers method headers non-header-args can-fail?)
    (let* ((access-token (account:access-token account))
           (dpop-proof
            (let ((key-pair (account:key-pair account)))
              (issue <dpop-proof>
                     key-pair
                     #:jwk (public-key key-pair)
                     #:htm method
                     #:htu uri
                     #:access-token access-token))))
      (let ((all-headers
             `((dpop . ,dpop-proof)
               (authorization . (dpop . ,access-token))
               ,@headers)))
        (receive (response body)
            (apply (p:anonymous-http-request) uri
                   #:headers all-headers
                   non-header-args)
          (let ((code (response-code response)))
            (if (and (eqv? code 401) can-fail?)
                ;; Code expired
                (begin
                  (set! account (account:refresh (account:invalidate-access-token account)))
                  ;; retry
                  (do-with-headers method headers non-header-args #f))
                (values account response body)))))))
  (let scan-arguments ((args other-args)
                       (headers #f)
                       (non-header-args '())
                       (method #f))
    (match args
      (()
       (cond
        ((not headers)
         (scan-arguments args '() non-header-args method))
        ((not method)
         (scan-arguments args headers non-header-args 'GET))
        (else
         (do-with-headers method headers (reverse non-header-args) #t))))
      ((#:method new-method args ...)
       (scan-arguments args headers non-header-args (or method new-method)))
      ((#:headers (new-headers ...) args ...)
       (scan-arguments args (or headers new-headers) non-header-args method))
      ((kw value args ...)
       (scan-arguments args headers `(,value ,kw ,@non-header-args) method)))))

(define* (serve-application id redirect-uri
                            #:key
                            (client-name "Example application")
                            (client-uri "https://webid-oidc-demo.planete-kraus.eu"))
  (when (string? id)
    (set! id (string->uri id)))
  (when (string? redirect-uri)
    (set! redirect-uri (string->uri redirect-uri)))
  (when (string? client-uri)
    (set! client-uri (string->uri client-uri)))
  (let* ((manifest
          (format #f
                  "{
  \"@context\": \"https://www.w3.org/ns/solid/oidc-context.jsonld\",
  \"client_id\" : \"~a\",
  \"redirect_uris\" : [\"~a\"],
  \"client_name\" : \"~a\",
  \"client_uri\" : \"~a\",
  \"grant_types\" : [\"refresh_token\", \"authorization_code\"],
  \"response_types\" : [\"code\"]
}
"
                  (uri->string id)
                  (uri->string redirect-uri)
                  client-name
                  (uri->string id)))
         (manifest-etag (stubs:hash 'SHA-256 manifest)))
    (lambda (request request-body)
      (let ((uri (request-uri request)))
        (cond
         ((equal? (uri-path uri) (uri-path id))
          (let ((if-none-match (request-if-none-match request)))
            (if (and (list? if-none-match)
                     (member manifest-etag
                             (map car (request-if-none-match request))))
                (values
                 (build-response
                  #:code 304
                  #:reason-phrase "Not Modified"
                  #:headers `((content-type application/ld+json)
                              (etag . (,manifest-etag . #t))))
                 #f)
                (values
                 (build-response
                  #:headers `((content-type application/ld+json)
                              (etag . (,manifest-etag . #t))
                              (cache-control public must-revalidate)))
                 manifest))))
         ((equal? (uri-path uri) (uri-path redirect-uri))
          (let ((query-args
                 (map
                  (lambda (key=value)
                    (let ((splits
                           (map uri-decode (string-split key=value #\=))))
                      (if (or (null? splits) (null? (cdr splits)))
                          splits
                          (cons (string->symbol (car splits)) (cdr splits)))))
                  (string-split (uri-query uri) #\&))))
            (let ((code (assq-ref query-args 'code)))
              (if code
                  (values
                   (build-response
                    #:headers `((content-type application/xhtml+xml)))
                   (with-output-to-string
                     (lambda ()
                       (sxml->xml
                        `(*TOP*
                          (*PI* xml "version=\"1.0\" encoding=\"utf-8\"")
                          (html (@ (xmlns "http://www.w3.org/1999/xhtml")
                                   (xml:lang "en"))
                                (head
                                 (title "Authorization"))
                                (body
                                 (p "You have been authorized. Please paste the following code in the application:")
                                 (p (strong ,code)))))))))
                  (values
                   (build-response
                    #:code 400
                    #:reason-phrase "Invalid Request"
                    #:headers `((content-type application/xhtml+xml)))
                   (with-output-to-string
                     (lambda ()
                       (sxml->xml
                        `(*TOP*
                          (*PI* xml "version=\"1.0\" encoding=\"utf-8\"")
                          (html (@ (xmlns "http://www.w3.org/1999/xhtml")
                                   (xml:lang "en"))
                                (head
                                 (title "Error"))
                                (body
                                 (p "Your identity provider did not authorize you. :("))))))))))))
         (else
          (values
           (build-response
            #:code 404
            #:reason-phrase "Not Found"
            #:headers `((content-type application/xhtml+xml)))
           (with-output-to-string
             (lambda ()
               (sxml->xml
                `(*TOP*
                  (*PI* xml "version=\"1.0\" encoding=\"utf-8\"")
                  (html (@ (xmlns "http://www.w3.org/1999/xhtml")
                           (xml:lang "en"))
                        (head
                         (title "Not Found"))
                        (body
                         (p "This page does not exist on the server."))))))))))))))