WIP DNM Support uploads using the "put" saver

The upload.js saver is old and clunky so it would be nice to switch
over to the put.js saver.

- Add a bogus WebDAV header for TiddlyWiki's put saver
- Add a controller method for the "put" saves and related routes
- Make it a configurable option for now, but still thinking about
  how to roll it out to prod, (hence the WIP).
- Add ETag header

There's a related PR for TiddlyWiki that would improve the UX by
showing the error explanations to the user.

Issue: #148

rails/app/controllers/concerns/subdomain_common.rb

@@ -10,4 +10,8 @@ def manage_iframe_header
     response.headers.except!('X-Frame-Options') if @site.try(:allow_in_iframe?)
   end
 
+  def etag_header
+    response.set_header 'ETag', @site.etag
+  end
+
 end

rails/app/controllers/tiddlyspot_controller.rb

@@ -14,11 +14,13 @@ def home
 
   def serve
     update_access_count_and_timestamp
+    etag_header
     render html: @site.html_content.html_safe, layout: false
   end
 
   def download
     update_access_count_and_timestamp
+    etag_header
     download_html_content(@site.html_content, @site.name)
   end
 

rails/app/controllers/tiddlywiki_controller.rb

@@ -7,7 +7,7 @@ class TiddlywikiController < ApplicationController
   before_action :find_site
 
   # TiddlyWiki can't provide the token for saving so we need to skip it
-  skip_before_action :verify_authenticity_token, only: :save
+  skip_before_action :verify_authenticity_token, only: [:upload_save, :put_save]
 
   # Rails wants a token for options requests, which TiddlyWiki similarly can't provide
   skip_before_action :verify_authenticity_token,
@@ -20,6 +20,11 @@ class TiddlywikiController < ApplicationController
   def serve
     return site_not_available unless site_visible?
 
+    # Convince TiddlyWiki it can use the put saver
+    dummy_webdav_header if request.options? && @site.enable_put_saver?
+
+    etag_header
+
     # Avoid site download for head or options requests
     return head 200 if request.head? || request.options?
 
@@ -35,6 +40,8 @@ def serve
   def json_content
     return site_not_available unless site_visible?
 
+    etag_header
+
     # Return empty body for options request with CORS headers
     return head 200 if request.options?
 
@@ -62,6 +69,8 @@ def tid_content
     # If we get nil, assume the tiddler doesn't exist
     return head 404 unless tiddler_data
 
+    etag_header
+
     # Return empty body for options request with CORS headers
     return head 200 if request.options?
 
@@ -86,7 +95,8 @@ def download
     download_html_content(@site.download_content, @site.name)
   end
 
-  def save
+  # Using the "upload" saver
+  def upload_save
     begin
       if site_saveable?
         @site.file_upload(params[:userfile])
@@ -102,6 +112,27 @@ def save
     end
   end
 
+  # Using the "put" saver
+  def put_save
+    begin
+      if site_saveable?
+        if request.headers['If-Match'].presence && request.headers['If-Match'] != @site.etag
+          render plain: "The site has been updated since you first loaded it. " +
+            "Saving now would cause the other changes to be lost.\n", status: 412
+        else
+          @site.file_upload(request.body)
+          @site.increment_save_count
+          head 204
+        end
+      else
+        render plain: "If this is your site please log in at\n#{main_site_url} and try again.\n", status: 403
+      end
+    rescue => e
+      # Todo: Should probably give a generic "Save failed!" message, and log the real problem
+      render plain: "#{e.class.name} #{e.message}\n", status: 500
+    end
+  end
+
   private
 
   def update_view_count_and_access_timestamp
@@ -194,4 +225,9 @@ def cors_headers
     response.set_header 'Access-Control-Allow-Headers', 'X-Requested-With'
   end
 
+  # TiddlyWiki just checks if the header it exists so the value doesn't matter
+  def dummy_webdav_header
+    response.set_header 'dav', "Dummy WebDAV header to enable TiddlyWiki's PUT saver"
+  end
+
 end

rails/app/models/concerns/site_common.rb

@@ -135,6 +135,11 @@ def site_cache(cache_type, &blk)
     Rails.cache.fetch(site_content_cache_key, expires_in: 4.weeks.from_now, &blk)
   end
 
+  # Should be a good enough for ETag headers
+  def etag
+    Digest::SHA256.base64digest("#{id}#{updated_at}#{blob.key}")
+  end
+
   def download_url
     "#{url}/download"
   end

rails/app/models/site.rb

@@ -56,7 +56,8 @@ def looks_valid?
   end
 
   def html_content(signed_in_user: nil)
-    th_file.apply_tiddlyhost_mods(name, signed_in_user: signed_in_user).to_html
+    th_file.apply_tiddlyhost_mods(name,
+      signed_in_user: signed_in_user, enable_put_saver: enable_put_saver).to_html
   end
 
   def json_data(opts={})

rails/config/routes.rb

@@ -29,7 +29,8 @@
     get '/favicon.ico', to: 'tiddlywiki#favicon'
     get '/download', to: 'tiddlywiki#download'
 
-    post '/', to: 'tiddlywiki#save'
+    post '/', to: 'tiddlywiki#upload_save'
+    put '/', to: 'tiddlywiki#put_save'
   end
 
   #

rails/db/migrate/20220404022507_add_put_saver_option_to_sites.rb

@@ -0,0 +1,5 @@
+class AddPutSaverOptionToSites < ActiveRecord::Migration[6.1]
+  def change
+    add_column :sites, :enable_put_saver, :boolean, default: false
+  end
+end

rails/db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 2022_03_30_234401) do
+ActiveRecord::Schema.define(version: 2022_04_04_022507) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -70,6 +70,7 @@
     t.integer "raw_byte_size"
     t.string "tw_version"
     t.boolean "allow_in_iframe", default: false
+    t.boolean "enable_put_saver", default: false
     t.index ["empty_id"], name: "index_sites_on_empty_id"
     t.index ["name"], name: "index_sites_on_name", unique: true
     t.index ["user_id"], name: "index_sites_on_user_id"

rails/lib/th_file.rb

@@ -38,17 +38,22 @@ def self.from_empty(empty_type)
     from_file(empty_path(empty_type))
   end
 
-  def apply_tiddlyhost_mods(site_name, for_download: false, signed_in_user: nil)
+  def apply_tiddlyhost_mods(site_name, for_download: false, enable_put_saver: false, signed_in_user: nil)
     if is_tw5?
 
-      upload_url = if !for_download
-        # The url for uploads is the same as the site url
-        Settings.subdomain_site_url(site_name)
-      else
-        # Clear $:/UploadURL so the save button in the downloaded file will not try
-        # to use upload.js. It should use another save method, probably download to file.
+      upload_url = if for_download || enable_put_saver
+        # Clear $:/UploadURL for downloads so the save button in the downloaded
+        # file will not try to use upload.js. It should use another save
+        # method, probably download to file.
+        #
         # Todo: Consider if we should do that also when signed_in_user is nil.
+        #
+        # Clear $:/UploadURL when using the put saver otherwise TW will
+        # prioritize the upload saver
         ""
+      else
+        # The url for uploads is the same as the site url
+        Settings.subdomain_site_url(site_name)
       end
 
       if !for_download && signed_in_user