;; 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 provider-confirmation)
  #:use-module (webid-oidc errors)
  #:use-module (webid-oidc fetch)
  #:use-module ((webid-oidc parameters) #:prefix p:)
  #:use-module (web uri)
  #:use-module (web response)
  #:use-module (rnrs bytevectors)
  #:use-module (srfi srfi-19)
  #:use-module (srfi srfi-26)
  #:use-module (ice-9 receive)
  #:use-module (ice-9 optargs)
  #:use-module (ice-9 match)
  #:use-module (ice-9 exceptions)
  #:use-module (webid-oidc web-i18n)
  #:use-module (rdf rdf)
  #:use-module (turtle tordf)
  #:declarative? #t
  #:export
  (

   &unconfirmed-provider
   make-unconfirmed-provider
   unconfirmed-provider?

   get-provider-confirmations
   confirm-provider
   ))

(define-exception-type
  &unconfirmed-provider
  &external-error
  make-unconfirmed-provider
  unconfirmed-provider?)

(define (find-confirmations subject graph)
  (let search-graph ((graph graph)
                     (confirmations '()))
    (match graph
      (() (reverse confirmations))
      ((hd graph ...)
       (match `(,(rdf-triple-subject hd)
                ,(rdf-triple-predicate hd)
                ,(rdf-triple-object hd))
         (((? (cute equal? subject <>) _)
           "http://www.w3.org/ns/solid/terms#oidcIssuer"
           (? string?
              (= string->uri
                 (and (? uri? provider)
                      (= uri-scheme 'https)))))
          (search-graph graph `(,provider ,@confirmations)))
         (else
          (search-graph graph confirmations)))))))

(define (serve-confirmations expiration-date subject cnf)
  (let ((resource (format #f "@prefix solid: <http://www.w3.org/ns/solid/terms#> .

<~a> solid:oidcIssuer ~a .
"
                          (uri->string subject)
                          (string-join (map (lambda (uri)
                                              (format #f "<~a>" (uri->string uri)))
                                            cnf)
                                       ", "))))
    (values (build-response #:headers `((content-type text/turtle)
                                        (expires . ,expiration-date)))
            resource)))

(define (get-provider-confirmations subject)
  (unless (equal? (uri-scheme subject) 'https)
    (set! subject (build-uri 'https
                             #:userinfo (uri-userinfo subject)
                             #:host (uri-host subject)
                             #:port (uri-port subject)
                             #:path (uri-path subject)
                             #:query (uri-query subject)
                             #:fragment (uri-fragment subject))))
  (let ((graph (fetch subject)))
    (cons (build-uri 'https
                     #:userinfo (uri-userinfo subject)
                     #:host (uri-host subject)
                     #:port (uri-port subject))
          (find-confirmations (uri->string subject) graph))))

(define (confirm-provider subject issuer)
  (unless (string=? (uri-host subject) (uri-host issuer))
    (let search ((providers (get-provider-confirmations subject)))
      (match providers
        (()
         (let ((final-message
                (format #f ("~s has not set ~s as an identity provider")
                        (uri->string subject)
                        (uri->string issuer))))
           (raise-exception
            (make-exception
             (make-unconfirmed-provider)
             (make-exception-with-message final-message)))))
        (((? (cute equal? <> issuer) _) . _)
         #t)
        ((_ providers ...)
         (search providers))))))