From b2e883105c2b7d5eae481abc5a0c9a3de913f544 Mon Sep 17 00:00:00 2001
From: Ray Miller <ray@metail.co.uk>
Date: Wed, 28 Aug 2024 14:51:43 +0100
Subject: [PATCH] Script to de-blogger markdown.

This script downloads images from blogger and replaces all the image
links in the markdown files with links to the local (just-downloaded)
files.

It also removes Amazon associate links and tracking and replaces links
to the orginal Blogger blog with relative links to the new blog.
---
 guile/de-blogger.scm | 115 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 115 insertions(+)
 create mode 100755 guile/de-blogger.scm

diff --git a/guile/de-blogger.scm b/guile/de-blogger.scm
new file mode 100755
index 0000000..70b90c2
--- /dev/null
+++ b/guile/de-blogger.scm
@@ -0,0 +1,115 @@
+#!/usr/bin/env -S guile -e main -s
+!#
+
+(use-modules (srfi srfi-26)
+             (srfi srfi-71)
+             (srfi srfi-197)
+             (ice-9 regex)
+             (ice-9 textual-ports)
+             (ice-9 binary-ports)
+             (ice-9 ftw)
+             (ice-9 format)
+             (ice-9 string-fun)
+             (web client)
+             (web response))
+
+(define base-dir "/home/ray/Workspace/personal/start-again-at-zero/")
+(define posts-dir (string-append base-dir "content/posts/"))
+(define image-dir (string-append base-dir "static/img/"))
+
+(define md-img-rx (make-regexp "!\\[[^]]*\\]\\((https?[^)]+)\\)"))
+
+(define md-img-link-rx (make-regexp "\\((https?[^)]+\\.(png|jpg))\\)" regexp/icase))
+
+(define img-src-rx (make-regexp "<img src=\"([^\"]+)\""))
+
+(define amazon-assoc-img-rx (make-regexp "!\\[\\]\\(http://www.assoc-amazon[^)]+\\)"))
+
+(define (http-get-follow-redirects url)
+  (let ((res body (http-get url #:streaming? #t)))
+    (if (<= 300 (response-code res) 399)
+        (http-get-follow-redirects (response-location res))
+        (if (eq? (car (response-content-type res)) 'text/html)
+            ;; Work-around for Google wrapping the image in HTML. Gah!
+            (let* ((content (get-string-all body))
+                   (new-url (match:substring (regexp-exec img-src-rx content) 1)))
+              (close-port body)
+              (http-get-follow-redirects new-url))
+            (values res body)))))
+
+(define download-image
+  (let ((image-num 1)
+        (images (make-hash-table)))
+    (lambda (url)
+      (format #t "download-image ~a~%" url)
+      (if (hash-ref images url)
+          (hash-ref images url)
+          (let* ((res body (http-get-follow-redirects url))
+                 (suffix (case (car (response-content-type res))
+                           ((image/jpeg) ".jpg")
+                           ((image/png) ".png")
+                           (else (error (format #f "download error: unexpected content-type for ~s" url)))))
+                 (filename (format #f "IMG_~4,'0d~a" image-num suffix)))
+            (hash-set! images url filename)
+            (set! image-num (1+ image-num))
+            (call-with-output-file (string-append image-dir filename)
+              (lambda (port)
+                (let loop ((data (get-bytevector-some body)))
+                  (unless (eof-object? data)
+                    (put-bytevector port data)
+                    (loop (get-bytevector-some body))))))
+            (close-port body)
+            filename)))))
+
+(define (replace-images doc)
+    (for-each (lambda (m)
+                (let* ((url (match:substring m 1))
+                       (filename (download-image url))
+                       (new-url (string-append "/img/" filename)))
+                  (set! doc (string-replace-substring doc url new-url))))
+              (list-matches md-img-rx doc))
+    doc)
+
+(define (replace-links doc)
+  (for-each (lambda (m)
+              (let* ((url (match:substring m 1))
+                     (filename (download-image url))
+                     (new-url (string-append "/img/" filename)))
+                (set! doc (string-replace-substring doc url new-url))))
+            (list-matches md-img-link-rx doc))
+  doc)
+
+(define (replace-amazon-tracking-images doc)
+  (for-each (lambda (m)
+              (set! doc (string-replace-substring doc (match:substring m) "")))
+            (list-matches amazon-assoc-img-rx doc))
+  doc)
+
+(define link-rx (make-regexp "\\[([^]]+)\\]\\(([^)]+)\\)"))
+
+(define (remove-amazon-links doc)
+  (for-each (lambda (m)
+              (when (string-contains (match:substring m 2) "staagaatzer-21")
+                (set! doc (string-replace-substring doc (match:substring m 0) (match:substring m 1)))))
+            (list-matches link-rx doc))
+  doc)
+
+(define (replace-self-links doc)
+  (string-replace-substring doc
+                            "http://startagainatzero.blogspot.com/"
+                            "/"))
+
+(define (process-file path)
+  (format #t "process-file ~a~%" path)
+  (let ((doc (chain (call-with-input-file path get-string-all)
+                    (replace-amazon-tracking-images _)
+                    (remove-amazon-links _)
+                    (replace-images _)
+                    (replace-links _)
+                    (replace-self-links _))))
+    (call-with-output-file path (cut put-string <> doc))))
+
+(define (main args)
+  (for-each process-file
+            (map (cute string-append posts-dir <>)
+                 (scandir posts-dir (cute string-suffix? ".md" <>)))))