From c606c71cb77a044b2bc34210f5eac719ba75354f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?c=C3=A6l=C5=8Drum=20spect=C4=81tr=C4=ABx?=
 <afiw@linuxposting.xyz>
Date: Fri, 21 Nov 2025 21:44:43 +0100
Subject: [PATCH] Add parallel downloads

---
 rain.scm | 34 ++++++++++++++++++++++++++++------
 1 file changed, 28 insertions(+), 6 deletions(-)

diff --git a/rain.scm b/rain.scm
index 28fb8cf..a373d91 100755
--- a/rain.scm
+++ b/rain.scm
@@ -3,13 +3,16 @@
 exec csi -ss "$0" "$@"
 |#
 
+(define parallel 1)
+
 (import (chicken io)
         (chicken format)
         (chicken port)
         (chicken process-context)
         (html-parser)
         (http-client)
-        (matchable))
+        (matchable)
+        (srfi-18))
 
 (define (find-comic-image index)
   (call-with-current-continuation
@@ -27,16 +30,28 @@ exec csi -ss "$0" "$@"
       (call-with-input-request (find-comic-image index)
                                #f
                                (lambda (in)
-                                 (copy-port in out))))))
+                                 (copy-port in out)))))
+  (format (current-error-port) "* downloaded comic image ~a~%" index))
 
 (define (download-all indices)
-  (for-each download-comic-image indices))
+  (format (current-error-port) "* using ~a threads~%" parallel)
+  (for-each download-batch (chop indices parallel)))
+
+(define (download-batch batch)
+  (let ((threads (map (lambda (index)
+                        (make-thread
+                         (lambda ()
+                           (download-comic-image index))))
+                      batch)))
+    (for-each thread-start! threads)
+    (for-each thread-join! threads)))
 
 (define (usage)
-  (format (current-error-port) "usage: ~a [OPTION ...] [INDEX ...]~%" (program-name))
+  (format (current-error-port) "usage: ~a [OPTION ...] INDEX ...~%" (program-name))
   (format (current-error-port) "options:~%")
-  (format (current-error-port) "  -h|-help    display this help message~%")
-  (format (current-error-port) "  -v|-version display version information~%"))
+  (format (current-error-port) "  -h|-help        display this help message~%")
+  (format (current-error-port) "  -v|-version     display version information~%")
+  (format (current-error-port) "  -j|-parallel N  download N images in parallel~%"))
 
 (define parse-command-line
   (match-lambda
@@ -44,6 +59,13 @@ exec csi -ss "$0" "$@"
      (usage))
     (((or "-v" "-version") . _)
      (format (current-error-port) "rain.scm 1.0.0~%" (program-name)))
+    (((or "-j" "-parallel") n . rest)
+     (let ((nn (string->number n)))
+       (unless nn
+         (usage)
+         (exit 1))
+       (set! parallel nn)
+       (parse-command-line rest)))
     (()
      (usage))
     (indices