[bug#52555] [PATCH v3 6/8] WIP: eris: Use HTTP to get ERIS blocks.

[pukkamustard <pukkamustard@posteo.net>]

- guix/eris.scm (guix-eris-block-ref): Refactor from call-with-eris-block-ref
and use eris-http-block-ref.
- guix/eris/fs-store.scm (eris-fs-store-ref): Refactor to take keyword
arguments.
- guix/scripts/substitute.scm (download-nar): Use guix-eris-block-ref.
- guix/scripts/publish.scm (make-request-handler): Use refactored
eris-fs-store-ref.

TODO:

- default value for %eris-peers parameter in (eris)
---
 guix/eris.scm               | 37 +++++++++++++++++++++++++++++++------
 guix/eris/fs-store.scm      | 21 ++++++++++-----------
 guix/scripts/publish.scm    |  9 ++++-----
 guix/scripts/substitute.scm | 14 ++++++++------
 4 files changed, 53 insertions(+), 28 deletions(-)

diff --git a/guix/eris.scm b/guix/eris.scm
index d9a0914b67..4af17c2807 100644
--- a/guix/eris.scm
+++ b/guix/eris.scm
@@ -21,9 +21,13 @@ (define-module (guix eris)
 
   #:use-module (guix config)
   #:use-module (guix eris fs-store)
+  #:use-module (guix eris http)
+
+  #:use-module (web uri)
+  #:use-module (ice-9 match)
 
   #:export (guix-eris-block-reducer
-            call-with-eris-block-ref
+            guix-eris-block-ref
 
             %eris-block-store-directory))
 
@@ -36,8 +40,29 @@ (define (guix-eris-block-reducer)
   "Returns a block reducer that stores blocks of ERIS encoded content."
   (eris-fs-store-reducer (%eris-block-store-directory)))
 
-(define (call-with-eris-block-ref f)
-  (let ((fs-store-block-ref
-         (eris-fs-store-ref
-          (%eris-block-store-directory))))
-    (f fs-store-block-ref)))
+(define %eris-peers
+  (make-parameter
+   ;; TODO
+   (list (string->uri "http://localhost:8081"))))
+
+(define* (try-in-order ref #:key block-refs)
+  (match block-refs
+    ((block-ref . rest)
+     (let ((block (block-ref ref)))
+       (if block
+           block
+           (try-in-order ref #:block-refs rest))))
+    (() #f)))
+
+(define* (guix-eris-block-ref ref #:key open-connection)
+  (try-in-order
+   ref
+   #:block-refs
+   (list
+    (lambda (ref)
+      (eris-fs-store-ref ref
+                         #:store-directory (%eris-block-store-directory)))
+    (lambda (ref)
+      (eris-http-block-ref ref
+                           #:host (string->uri "http://localhost:8081")
+                           #:open-connection open-connection)))))
diff --git a/guix/eris/fs-store.scm b/guix/eris/fs-store.scm
index 2ef7607988..38f5926280 100644
--- a/guix/eris/fs-store.scm
+++ b/guix/eris/fs-store.scm
@@ -54,14 +54,13 @@ (define (eris-fs-store-reducer store-directory)
 
        #t))))
 
-(define (eris-fs-store-ref store-directory)
-  (lambda (ref)
-    (let* ((b32 (base32-encode ref))
-	   (pre (substring b32 0 2))
-	   (suf (substring b32 2))
-	   (path (string-append store-directory "/" pre "/" suf)))
-      (if (file-exists? path)
-	  (call-with-input-file path
-	    (lambda (port) (get-bytevector-all port))
-	    #:binary #t)
-	  #f))))
+(define* (eris-fs-store-ref ref #:key store-directory)
+  (let* ((b32 (base32-encode ref))
+	 (pre (substring b32 0 2))
+	 (suf (substring b32 2))
+	 (path (string-append store-directory "/" pre "/" suf)))
+    (if (file-exists? path)
+	(call-with-input-file path
+	  (lambda (port) (get-bytevector-all port))
+	  #:binary #t)
+	#f)))
diff --git a/guix/scripts/publish.scm b/guix/scripts/publish.scm
index 15bdf02670..0ce50b2942 100644
--- a/guix/scripts/publish.scm
+++ b/guix/scripts/publish.scm
@@ -1085,13 +1085,12 @@ (define nar-path?
     (let ((expected (split-and-decode-uri-path nar-path)))
       (cut equal? expected <>)))
 
-  ;; Get ERIS blocks directly from the filesystem store.
-  (define eris-block-ref
-    (eris-fs-store-ref (%eris-block-store-directory)))
-
   ;; Create a handler for resolving blake2b URN queries.
   (define blake2b-urn-query-ref
-    (make-blake2b-urn-query-ref eris-block-ref))
+    (make-blake2b-urn-query-ref
+     (lambda (ref) (eris-fs-store-ref
+                    ref
+                    #:store-directory (%eris-block-store-directory)))))
 
   (define (handle request body)
     (format #t "~a ~a~%"
diff --git a/guix/scripts/substitute.scm b/guix/scripts/substitute.scm
index 8cf011d7e6..14a21f6c37 100755
--- a/guix/scripts/substitute.scm
+++ b/guix/scripts/substitute.scm
@@ -482,12 +482,14 @@ (define (fetch uri)
       ((urn)
        (let ((read-capability (->eris-read-capability uri)))
          (if (eris-read-capability? read-capability)
-             (call-with-eris-block-ref
-              (lambda (block-ref)
-                (values (open-eris-input-port
-                         read-capability
-                         #:block-ref block-ref)
-                        #f)))
+             (values
+              (open-eris-input-port
+               read-capability
+               #:block-ref (lambda (ref)
+                             (guix-eris-block-ref
+                              ref
+                              #:open-connection open-connection-for-uri/cached)))
+              #f)
              (leave (G_ "unsupported substitute URI scheme: ~a~%")
                     (uri->string uri)))))
       (else
-- 
2.38.1