Merge pull request #43 from blocknotes/prawn-html-instance

Introduce PrawnHtml::Instance class to preserve the context

Author: blocknotes

README.md

@@ -35,6 +35,23 @@ pdf.render_file('test.pdf')
 
 To check some examples with the PDF output see [examples](examples/) folder.
 
+Alternative form using _PrawnHtml::Instance_ to preserve the context:
+
+```rb
+require 'prawn-html'
+pdf = Prawn::Document.new(page_size: 'A4')
+phtml = PrawnHtml::Instance.new(pdf)
+css = <<~CSS
+  h1 { color: green }
+  i { color: red }
+CSS
+phtml.append(css: css)
+phtml.append(html: '<h1>Some <i>HTML</i> before</h1>')
+pdf.text 'Some Prawn text'
+phtml.append(html: '<h1>Some <i>HTML</i> after</h1>')
+pdf.render_file('test.pdf')
+```
+
 ## Supported tags & attributes
 
 HTML tags (using MDN definitions):

examples/instance.pdf

@@ -156,10 +156,7 @@ module PrawnHtml
   }.freeze
 
   def append_html(pdf, html)
-    pdf_wrapper = PdfWrapper.new(pdf)
-    renderer = DocumentRenderer.new(pdf_wrapper)
-    html_parser = PrawnHtml::HtmlParser.new(renderer)
-    html_parser.process(html)
+    PrawnHtml::Instance.new(pdf).append(html: html)
   end
 
   module_function :append_html
@@ -179,3 +176,4 @@ def append_html(pdf, html)
 require 'prawn_html/pdf_wrapper'
 require 'prawn_html/document_renderer'
 require 'prawn_html/html_parser'
+require 'prawn_html/instance'

lib/prawn-html.rb

@@ -15,19 +15,28 @@ def initialize(renderer, ignore_content_tags: %i[script style])
       @ignore = false
       @ignore_content_tags = ignore_content_tags
       @renderer = renderer
-      @styles = {}
+      @raw_styles = {}
     end
 
     # Processes HTML and renders it
     #
     # @param html [String] The HTML content to process
     def process(html)
+      @styles = {}
       @processing = !html.include?('<body')
       @document = Oga.parse_html(html)
+      process_styles # apply previously loaded styles
       traverse_nodes(document.children)
       renderer.flush
     end
 
+    # Parses CSS styles
+    #
+    # @param text_styles [String] The CSS styles to evaluate
+    def parse_styles(text_styles)
+      @raw_styles = text_styles.scan(REGEXP_STYLES).to_h
+    end
+
     private
 
     attr_reader :document, :ignore, :processing, :renderer, :styles
@@ -59,9 +68,9 @@ def init_element(node)
       end
     end
 
-    def process_styles(text_styles)
-      hash_styles = text_styles.scan(REGEXP_STYLES).to_h
-      hash_styles.each do |selector, rule|
+    def process_styles(text_styles = nil)
+      parse_styles(text_styles) if text_styles
+      @raw_styles.each do |selector, rule|
         document.css(selector).each do |node|
           styles[node] = rule
         end

lib/prawn_html/html_parser.rb

@@ -0,0 +1,18 @@
+# frozen_string_literal: true
+
+module PrawnHtml
+  class Instance
+    attr_reader :html_parser, :pdf_wrapper, :renderer
+
+    def initialize(pdf)
+      @pdf_wrapper = PrawnHtml::PdfWrapper.new(pdf)
+      @renderer = PrawnHtml::DocumentRenderer.new(@pdf_wrapper)
+      @html_parser = PrawnHtml::HtmlParser.new(@renderer)
+    end
+
+    def append(css: nil, html: nil)
+      html_parser.parse_styles(css) if css
+      html_parser.process(html) if html
+    end
+  end
+end

lib/prawn_html/instance.rb

@@ -0,0 +1,22 @@
+# frozen_string_literal: true
+
+RSpec.describe 'Instance' do
+  it 'preserves the styles in the instance' do
+    pdf = Prawn::Document.new(page_size: 'A4')
+    phtml = PrawnHtml::Instance.new(pdf)
+    css = <<~CSS
+      h1 { color: green }
+      i { color: red }
+    CSS
+    phtml.append(css: css)
+    phtml.append(html: '<h1>Some <i>HTML</i> before</h1>')
+    pdf.text 'Some Prawn text'
+    phtml.append(html: '<h1>Some <i>HTML</i> after</h1>')
+
+    output_file = File.expand_path('../../examples/instance.pdf', __dir__)
+    pdf.render_file(output_file) unless File.exist?(output_file)
+
+    expected_pdf = File.read(output_file)
+    expect(Zlib.crc32(pdf.render)).to eq Zlib.crc32(expected_pdf)
+  end
+end

spec/features/instance_spec.rb

@@ -38,6 +38,14 @@
     end
   end
 
+  describe '#parse_styles' do
+    subject(:parse_styles) { html_parser.parse_styles(css) }
+
+    let(:css) { 'h1 { color: red }' }
+
+    it { is_expected.to eq('h1' => 'color: red') }
+  end
+
   describe '#process' do
     subject(:process) { html_parser.process(html) }
 

spec/units/prawn_html/html_parser_spec.rb

@@ -0,0 +1,39 @@
+# frozen_string_literal: true
+
+RSpec.describe PrawnHtml::Instance do
+  describe 'initialize' do
+    subject(:instance) { described_class.new(pdf) }
+
+    let(:pdf) { instance_double(Prawn::Document) }
+
+    before do
+      allow(PrawnHtml::PdfWrapper).to receive(:new)
+      allow(PrawnHtml::DocumentRenderer).to receive(:new)
+      allow(PrawnHtml::HtmlParser).to receive(:new)
+    end
+
+    it 'initializes the required entities', :aggregate_failures do
+      instance
+      expect(PrawnHtml::PdfWrapper).to have_received(:new)
+      expect(PrawnHtml::DocumentRenderer).to have_received(:new)
+      expect(PrawnHtml::HtmlParser).to have_received(:new)
+    end
+  end
+
+  describe '#append' do
+    subject(:append) { described_class.new(pdf).append(html: html) }
+
+    let(:html) { '<h1>Some HTML</h1>' }
+    let(:html_parser) { instance_double(PrawnHtml::HtmlParser, process: nil) }
+    let(:pdf) { instance_double(Prawn::Document) }
+
+    before do
+      allow(PrawnHtml::HtmlParser).to receive(:new).and_return(html_parser)
+    end
+
+    it 'sends a process message to the html parser' do
+      append
+      expect(html_parser).to have_received(:process).with(html)
+    end
+  end
+end