From a16299b65adf521b86d37a48010141f4c76d124d Mon Sep 17 00:00:00 2001
From: Eugen Rochko <eugen@zeonfederated.com>
Date: Mon, 14 Aug 2023 20:19:05 +0200
Subject: [PATCH] Change hashtags at the end of the post to render out-of-band

---
 app/helpers/formatting_helper.rb |  2 +-
 app/lib/text_formatter.rb        | 43 +++++++++++++++++++++++++++++++-
 spec/lib/text_formatter_spec.rb  | 35 +++++++++++++++++++++++---
 3 files changed, 75 insertions(+), 5 deletions(-)

diff --git a/app/helpers/formatting_helper.rb b/app/helpers/formatting_helper.rb
index 5ab0c8c7ba..72377e2771 100644
--- a/app/helpers/formatting_helper.rb
+++ b/app/helpers/formatting_helper.rb
@@ -15,7 +15,7 @@ module FormattingHelper
   module_function :extract_status_plain_text
 
   def status_content_format(status)
-    html_aware_format(status.text, status.local?, preloaded_accounts: [status.account] + (status.respond_to?(:active_mentions) ? status.active_mentions.map(&:account) : []))
+    html_aware_format(status.text, status.local?, strip_rich_entities: true, preloaded_accounts: [status.account] + (status.respond_to?(:active_mentions) ? status.active_mentions.map(&:account) : []))
   end
 
   def rss_status_content_format(status)
diff --git a/app/lib/text_formatter.rb b/app/lib/text_formatter.rb
index 581ee835b3..f659edfa1b 100644
--- a/app/lib/text_formatter.rb
+++ b/app/lib/text_formatter.rb
@@ -20,6 +20,7 @@ class TextFormatter
   # @option options [Boolean] :multiline
   # @option options [Boolean] :with_domains
   # @option options [Boolean] :with_rel_me
+  # @option options [Boolean] :strip_rich_entities
   # @option options [Array<Account>] :preloaded_accounts
   def initialize(text, options = {})
     @text    = text
@@ -75,16 +76,22 @@ class TextFormatter
       entity[:indices].first
     end
 
+    interrupt_text_at = detect_hashtag_block if options[:strip_rich_entities]
     result = +''
 
     last_index = entities.reduce(0) do |index, entity|
       indices = entity[:indices]
+
       result << h(text[index...indices.first])
+
+      break interrupt_text_at if interrupt_text_at.present? && indices.first >= interrupt_text_at
+
       result << yield(entity)
+
       indices.last
     end
 
-    result << h(text[last_index..])
+    result << h(text[last_index..]) unless interrupt_text_at.present? && last_index >= interrupt_text_at
 
     result
   end
@@ -163,4 +170,38 @@ class TextFormatter
   def preloaded_accounts?
     preloaded_accounts.present?
   end
+
+  def detect_hashtag_block
+    block_begin = nil
+    block_end = nil
+
+    entities.map.with_index do |entity, i|
+      next unless entity[:hashtag]
+
+      next_entity = entities[i + 1]
+
+      if !next_entity.nil? && !next_entity[:hashtag]
+        block_begin = nil
+        block_end = nil
+        next
+      elsif next_entity.nil?
+        block_begin = entity[:indices].first if block_begin.nil?
+        block_end = entity[:indices].last
+        next
+      end
+
+      entity_end = entity[:indices].last
+      next_entity_start = next_entity[:indices].first
+
+      if next_entity_start == entity_end + 1
+        block_begin = entity[:indices].first if block_begin.nil?
+        block_end = entity_end
+      else
+        block_begin = nil
+        block_end = nil
+      end
+    end
+
+    block_begin if block_begin.present? && block_end.present? && text[block_end..].blank? && text[block_begin - 1] == "\n"
+  end
 end
diff --git a/spec/lib/text_formatter_spec.rb b/spec/lib/text_formatter_spec.rb
index 8b922c018b..72bbb40512 100644
--- a/spec/lib/text_formatter_spec.rb
+++ b/spec/lib/text_formatter_spec.rb
@@ -4,8 +4,9 @@ require 'rails_helper'
 
 RSpec.describe TextFormatter do
   describe '#to_s' do
-    subject { described_class.new(text, preloaded_accounts: preloaded_accounts).to_s }
+    subject { described_class.new(text, strip_rich_entities: strip_rich_entities, preloaded_accounts: preloaded_accounts).to_s }
 
+    let(:strip_rich_entities) { false }
     let(:preloaded_accounts) { nil }
 
     context 'when given text containing plain text' do
@@ -273,7 +274,7 @@ RSpec.describe TextFormatter do
     end
 
     context 'when given text containing a hashtag' do
-      let(:text)  { '#hashtag' }
+      let(:text)  { 'foo #hashtag' }
 
       it 'creates a hashtag link' do
         expect(subject).to include '/tags/hashtag" class="mention hashtag" rel="tag">#<span>hashtag</span></a>'
@@ -281,7 +282,7 @@ RSpec.describe TextFormatter do
     end
 
     context 'when given text containing a hashtag with Unicode chars' do
-      let(:text)  { '#hashtagタグ' }
+      let(:text)  { 'foo #hashtagタグ' }
 
       it 'creates a hashtag link' do
         expect(subject).to include '/tags/hashtag%E3%82%BF%E3%82%B0" class="mention hashtag" rel="tag">#<span>hashtagタグ</span></a>'
@@ -311,5 +312,33 @@ RSpec.describe TextFormatter do
         expect(subject).to include 'href="magnet:?xt=urn:btih:c12fe1c06bba254a9dc9f519b335aa7c1367a88a"'
       end
     end
+
+    context 'with strip_rich_entities option' do
+      let(:strip_rich_entities) { true }
+
+      context 'when a hashtag is in the middle of a sentence' do
+        let(:text) { 'Hello #foo world' }
+
+        it 'keeps the hashtag in place' do
+          expect(subject).to include 'foo'
+        end
+      end
+
+      context 'when a hashtag starts a line but is followed by text' do
+        let(:text) { '#foo Hello world' }
+
+        it 'keeps the hashtag in place' do
+          expect(subject).to include 'foo'
+        end
+      end
+
+      context 'when a hashtag is on the last line in the text' do
+        let(:text) { "Hello world\n#foo" }
+
+        it 'strips out the hashtag' do
+          expect(subject).to_not include 'foo'
+        end
+      end
+    end
   end
 end