Class: Collavre::MarkdownConverter

Inherits:
Object
  • Object
show all
Defined in:
app/services/collavre/markdown_converter.rb

Overview

Converts between Markdown and HTML for creative descriptions.

Extracted from CreativesHelper to keep conversion logic testable outside of view contexts and reusable from services (e.g. MarkdownImporter).

Class Method Summary collapse

Class Method Details

.data_image_to_attachment(data_url, alt) ⇒ Object

Convert a data-URI image to an Active Storage attachment <img> tag.



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# File 'app/services/collavre/markdown_converter.rb', line 197

def data_image_to_attachment(data_url, alt)
  if data_url =~ %r{\Adata:(image/[\w.+-]+);base64,(.+)\z}
    content_type = Regexp.last_match(1)
    data = Base64.decode64(Regexp.last_match(2))
    ext = Mime::Type.lookup(content_type).symbol.to_s
    filename = "import-#{SecureRandom.hex}.#{ext}"
    blob = ActiveStorage::Blob.create_and_upload!(io: StringIO.new(data), filename: filename, content_type: content_type)
    "<img src=\"#{Rails.application.routes.url_helpers.rails_blob_url(blob, only_path: true)}\" alt=\"#{alt}\" />"
  else
    "<img src=\"#{data_url}\" alt=\"#{alt}\" />"
  end
end

.data_uri_to_blob_path(data_url) ⇒ Object

Convert a data-URI to a freshly-uploaded Active Storage blob path. Returns the original URL unchanged on parse failure.



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# File 'app/services/collavre/markdown_converter.rb', line 255

def data_uri_to_blob_path(data_url)
  return data_url unless data_url =~ %r{\Adata:(image/[\w.+-]+);base64,(.+)\z}

  content_type = Regexp.last_match(1)
  data = Base64.decode64(Regexp.last_match(2))
  ext = Mime::Type.lookup(content_type).symbol.to_s
  filename = "import-#{SecureRandom.hex}.#{ext}"
  blob = ActiveStorage::Blob.create_and_upload!(io: StringIO.new(data), filename: filename, content_type: content_type)
  Rails.application.routes.url_helpers.rails_blob_url(blob, only_path: true)
end

.html_to_markdown(text) ⇒ Object

Convert HTML (links, bold, images, tables) back to Markdown.



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# File 'app/services/collavre/markdown_converter.rb', line 63

def html_to_markdown(text)
  return "" if text.nil?
  markdown = text.dup
  placeholders = {}
  index = 0

  # Tables → Markdown tables
  markdown.gsub!(%r{<table\b[^>]*>.*?</table>}im) do |match|
    token = "__TABLE#{index}__"; index += 1
    placeholders[token] = table_to_markdown(match)
    token
  end

  # Action-text attachments → data-URI images
  markdown.gsub!(%r{<action-text-attachment ([^>]+)>(?:</action-text-attachment>)?}) do |_match|
    attrs = Hash[$1.scan(/(\S+?)="([^"]*)"/)]
    sgid = attrs["sgid"]
    caption = attrs["caption"] || ""
    if (blob = GlobalID::Locator.locate_signed(sgid, for: "attachable"))
      data = Base64.strict_encode64(blob.download)
      token = "__IMG#{index}__"; index += 1
      placeholders[token] = "![#{caption}](data:#{blob.content_type};base64,#{data})"
      token
    else
      ""
    end
  end

  # Active Storage blob images → data-URI
  markdown.gsub!(%r{<img [^>]*src=["'](/rails/active_storage/blobs/[^"']+)["'][^>]*alt=["']([^"']*)["'][^>]*>}) do |match|
    blob_path = $1
    alt_text = $2
    if blob_path =~ %r{/rails/active_storage/blobs/(?:redirect|proxy)/([^/]+)/}
      signed_id = $1
      begin
        blob = ActiveStorage::Blob.find_signed(signed_id)
        data = Base64.strict_encode64(blob.download)
        token = "__IMG#{index}__"; index += 1
        placeholders[token] = "![#{alt_text}](data:#{blob.content_type};base64,#{data})"
        token
      rescue StandardError
        match
      end
    else
      match
    end
  end

  # Inline data-URI images (src before alt)
  markdown.gsub!(/<img [^>]*src=['"](data:[^'"]+)['"][^>]*alt=['"]([^'"]*)['"][^>]*>/) do
    token = "__IMG#{index}__"; index += 1
    placeholders[token] = "![#{$2}](#{$1})"
    token
  end

  # Inline data-URI images (alt before src)
  markdown.gsub!(/<img [^>]*alt=['"]([^'"]*)['"][^>]*src=['"](data:[^'"]+)['"][^>]*>/) do
    token = "__IMG#{index}__"; index += 1
    placeholders[token] = "![#{$1}](#{$2})"
    token
  end

  # Links → [text](url)
  markdown.gsub!(/<a [^>]*href=['"]([^'"]+)['"][^>]*>(.*?)<\/a>/m) do
    inner = ActionView::Base.full_sanitizer.sanitize($2)
    token = "__LINK#{index}__"; index += 1
    placeholders[token] = "[#{inner}](#{$1})"
    token
  end

  # Bold → **text**
  markdown.gsub!(/<(strong|b)(?:\s+[^>]*)?>(.*?)<\/\1>/im) do
    token = "__BOLD#{index}__"; index += 1
    placeholders[token] = "**#{$2.strip}**"
    token
  end

  # Escape markdown special chars in remaining text
  markdown.gsub!(/([\\*\[\]()!#~+\-])/) { "\\#{$1}" }

  # Restore placeholders
  placeholders.each { |k, v| markdown.gsub!(k, v) }

  # Strip remaining HTML tags
  markdown.gsub!(/<[^>]+>/, "")
  markdown
end

.markdown_to_html(text, image_refs = {}) ⇒ Object

Convert Markdown to HTML using commonmarker (GFM full support). Falls back to lightweight regex conversion for short inline fragments.



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# File 'app/services/collavre/markdown_converter.rb', line 15

def markdown_to_html(text, image_refs = {})
  return "" if text.nil?

  # Protect fenced code blocks and inline code spans from the regex
  # rewrites below — a Markdown sample like ```` ```md\n![x](data:...)\n``` ````
  # must not silently upload its data URI as an Active Storage blob.
  input = with_code_protected(text.dup) do |source|
    # Collect reference-style data-URI images. CommonMark allows both the
    # angle-bracket form `[alt]: <data:...>` and the bare form
    # `[alt]: data:image/...`, optionally followed by a title.
    source.gsub!(/^\s*\[([^\]]+)\]:\s*(?:<\s*(data:image\/[^>]+?)\s*>|(data:image\/\S+))\s*(?:"[^"]*"|'[^']*'|\([^)]*\))?\s*$/) do
      image_refs[$1] = ($2 || $3).strip
      ""
    end

    # Convert data-URI images to Active Storage before rendering
    source.gsub!(/(?<!\\)!\[([^\]]*)\]\[([^\]]+)\]/) do
      if (data_url = image_refs[$2])
        data_image_to_attachment(data_url, $1)
      else
        "![#{$1}][#{$2}]"
      end
    end

    # Inline data-URI images. base64 contains no whitespace or `)`, so bound
    # the URL on those and capture an optional CommonMark title separately;
    # otherwise `data:...;base64,XYZ "caption"` would be slurped as one URL
    # and fail the strict parser in `data_image_to_attachment`. Titles may be
    # double-quoted, single-quoted, or parenthesized per CommonMark.
    source.gsub!(/(?<!\\)!\[([^\]]*)\]\(\s*(data:image\/[^\s)]+)(?:\s+(?:"[^"]*"|'[^']*'|\([^)]*\)))?\s*\)/) do
      data_image_to_attachment($2, $1)
    end

    source
  end

  # Render with commonmarker (GFM extensions: table, strikethrough, autolink, tasklist, tagfilter)
  html = Commonmarker.to_html(input, options: {
    parse: { smart: true },
    render: { unsafe: true },
    extension: { table: true, strikethrough: true, autolink: true, tasklist: true, tagfilter: true }
  })

  html.strip!
  html
end

.rewrite_data_uri_images(text) ⇒ Object

Rewrite data-URI image references in Markdown source to point at newly-created Active Storage blobs. Returns rewritten Markdown.

Used by the inline Markdown editor to persist blob URLs in the stored ‘markdown_source`, so subsequent text edits around the image do not re-import the same data URI into a fresh blob on every autosave.



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# File 'app/services/collavre/markdown_converter.rb', line 216

def rewrite_data_uri_images(text)
  return text if text.nil?
  image_refs = {}

  # Protect fenced code blocks and inline code spans before rewriting —
  # a Markdown code sample like ```` ```md\n![x](data:...)\n``` ```` must
  # not be silently uploaded as a blob and have its source rewritten,
  # which would corrupt the user's code snippet on every autosave.
  with_code_protected(text.dup) do |result|
    # Collect reference-style data-URI image definitions. CommonMark accepts
    # both the angle-bracket form `[alt]: <data:...>` and the bare form
    # `[alt]: data:image/...`, optionally followed by a title. Rewrite each
    # definition to point at a freshly-uploaded blob, normalizing to the
    # bare form (titles are dropped since blob paths cannot collide with
    # surrounding text).
    result.gsub!(/^(\s*\[)([^\]]+)(\]:\s*)(?:<\s*(data:image\/[^>]+?)\s*>|(data:image\/\S+))(\s*(?:"[^"]*"|'[^']*'|\([^)]*\))?\s*)$/) do
      lead, label, mid, angle_url, bare_url, tail = $1, $2, $3, $4, $5, $6
      data_url = (angle_url || bare_url).strip
      blob_path = data_uri_to_blob_path(data_url)
      image_refs[label] = blob_path
      "#{lead}#{label}#{mid}#{blob_path}#{tail}"
    end

    # Inline data-URI images: ![alt](data:...) or ![alt](data:... "title")
    # → ![alt](blob_path) / ![alt](blob_path "title"). Parse the title
    # separately so it doesn't get captured into the data URL and break
    # strict matching in `data_uri_to_blob_path`. Titles may be
    # double-quoted, single-quoted, or parenthesized per CommonMark.
    result.gsub!(/(?<!\\)!\[([^\]]*)\]\(\s*(data:image\/[^\s)]+)(\s+(?:"[^"]*"|'[^']*'|\([^)]*\)))?\s*\)/) do
      alt, data_url, title = $1, $2, $3
      "![#{alt}](#{data_uri_to_blob_path(data_url)}#{title})"
    end

    result
  end
end

.table_block?(text) ⇒ Boolean

Check whether text looks like a Markdown table block.

Returns:

  • (Boolean) 


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# File 'app/services/collavre/markdown_converter.rb', line 152

def table_block?(text)
  lines = text.to_s.strip.split("\n")
  return false if lines.length < 2

  header_line = lines[0]
  alignment_line = lines[1]
  return false unless header_line.match?(/\A\|.*\|\z/)
  return false unless alignment_line.match?(/\A\|[ \-:\|]+\|\z/)

  true
end

.table_to_markdown(table_html) ⇒ Object

Convert an HTML <table> fragment to a Markdown table string.



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# File 'app/services/collavre/markdown_converter.rb', line 165

def table_to_markdown(table_html)
  fragment = Nokogiri::HTML::DocumentFragment.parse(table_html)
  table = fragment.at_css("table")
  return "" unless table

  header_row = table.at_css("thead tr") || table.css("tr").first
  return "" unless header_row

  header_cells = header_row.css("th,td")
  headers = header_cells.map { |cell| escape_table_cell(html_to_markdown(cell.inner_html).strip) }
  alignments = header_cells.map { |cell| alignment_from_cell(cell) }

  body_rows = table.css("tbody tr")
  if body_rows.empty?
    all_rows = table.css("tr")
    body_rows = all_rows.drop(1)
  end

  body_lines = body_rows.map do |row|
    cells = row.css("th,td").map { |cell| escape_table_cell(html_to_markdown(cell.inner_html).strip) }
    normalized = pad_cells(cells, headers.length)
    "| #{normalized.join(' | ')} |"
  end

  alignment_cells = pad_cells(alignments, headers.length).map { |align| alignment_marker(align) }
  header_line = "| #{headers.map(&:strip).join(' | ')} |"
  alignment_line = "| #{alignment_cells.join(' | ')} |"

  ([ header_line, alignment_line ] + body_lines).join("\n")
end