# frozen_string_literal: true

module Prawn
  module Text
    module Formatted
      # Implements a bi-directional parser between a subset of html and
      # formatted text arrays.
      class Parser
        # @group Extension API

        # Parser regular expression.
        # @private
        PARSER_REGEX =
          begin
            regex_string =
              "\n|" \
                '<b>|</b>|' \
                '<i>|</i>|' \
                '<u>|</u>|' \
                '<strikethrough>|</strikethrough>|' \
                '<sub>|</sub>|' \
                '<sup>|</sup>|' \
                '<link[^>]*>|</link>|' \
                '<color[^>]*>|</color>|' \
                '<font[^>]*>|</font>|' \
                '<strong>|</strong>|' \
                '<em>|</em>|' \
                '<a[^>]*>|</a>|' \
                "[^<\n]+"
            Regexp.new(regex_string, Regexp::MULTILINE)
          end

        # Escaped characters.
        # @private
        ESCAPE_CHARS = {
          '&' => '&amp;',
          '>' => '&gt;',
          '<' => '&lt;',
        }.freeze

        # @private
        UNESCAPE_CHARS = ESCAPE_CHARS.invert.freeze

        # Parse formatted string.
        #
        # @param string [String]
        # @return [Array<Hash>] Text fragments.
        def self.format(string, *_args)
          tokens = string.gsub(%r{<br\s*/?>}, "\n").scan(PARSER_REGEX)
          array_from_tokens(tokens)
        end

        # Serialize text fragments to an inline format string.
        #
        # @param array [Array<Hash>]
        # @return [String]
        def self.to_string(array)
          prefixes = {
            bold: '<b>',
            italic: '<i>',
            underline: '<u>',
            strikethrough: '<strikethrough>',
            subscript: '<sub>',
            superscript: '<sup>',
          }
          suffixes = {
            bold: '</b>',
            italic: '</i>',
            underline: '</u>',
            strikethrough: '</strikethrough>',
            subscript: '</sub>',
            superscript: '</sup>',
          }
          array
            .map { |hash|
              prefix = ''
              suffix = ''
              hash[:styles]&.each do |style|
                prefix += prefixes[style]
                suffix = suffixes[style] + suffix
              end

              font = hash[:font] ? " name='#{hash[:font]}'" : nil
              size = hash[:size] ? " size='#{hash[:size]}'" : nil
              character_spacing =
                if hash[:character_spacing]
                  " character_spacing='#{hash[:character_spacing]}'"
                end
              if font || size || character_spacing
                prefix += "<font#{font}#{size}#{character_spacing}>"
                suffix = '</font>'
              end

              link = hash[:link] ? " href='#{hash[:link]}'" : nil
              anchor = hash[:anchor] ? " anchor='#{hash[:anchor]}'" : nil
              if link || anchor
                prefix += "<link#{link}#{anchor}>"
                suffix = '</link>'
              end

              if hash[:color]
                prefix +=
                  if hash[:color].is_a?(Array)
                    "<color c='#{hash[:color][0]}' " \
                      "m='#{hash[:color][1]}' " \
                      "y='#{hash[:color][2]}' " \
                      "k='#{hash[:color][3]}'>"
                  else
                    "<color rgb='#{hash[:color]}'>"
                  end
                suffix = '</color>'
              end

              string = escape(hash[:text])
              prefix + string + suffix
            }
            .join
        end

        # Break text into paragraphs.
        #
        # @private
        # @param array [Array<Hash>] Text fragments.
        # @return [Array<Array<Hash>>] Pragraphs of text fragments.
        def self.array_paragraphs(array)
          paragraphs = []
          paragraph = []
          previous_string = "\n"
          scan_pattern = /[^\n]+|\n/
          array.each do |hash|
            hash[:text].scan(scan_pattern).each do |string|
              if string == "\n"
                if previous_string == "\n"
                  paragraph << hash.dup.merge(text: "\n")
                end
                paragraphs << paragraph unless paragraph.empty?
                paragraph = []
              else
                paragraph << hash.dup.merge(text: string)
              end
              previous_string = string
            end
          end
          paragraphs << paragraph unless paragraph.empty?
          paragraphs
        end

        # @private
        # @param tokens [Array<String>]
        # @return [Array<Hash>]
        def self.array_from_tokens(tokens)
          array = []
          styles = []
          colors = []
          link = nil
          anchor = nil
          local = nil
          fonts = []
          sizes = []
          character_spacings = []

          tokens.each do |token|
            case token
            when '<b>', '<strong>'
              styles << :bold
            when '<i>', '<em>'
              styles << :italic
            when '<u>'
              styles << :underline
            when '<strikethrough>'
              styles << :strikethrough
            when '<sub>'
              styles << :subscript
            when '<sup>'
              styles << :superscript
            when '</b>', '</strong>'
              styles.delete(:bold)
            when '</i>', '</em>'
              styles.delete(:italic)
            when '</u>'
              styles.delete(:underline)
            when '</strikethrough>'
              styles.delete(:strikethrough)
            when '</sub>'
              styles.delete(:subscript)
            when '</sup>'
              styles.delete(:superscript)
            when '</link>', '</a>'
              link = nil
              anchor = nil
              local = nil
            when '</color>'
              colors.pop
            when '</font>'
              fonts.pop
              sizes.pop
              character_spacings.pop
            when /^<link[^>]*>$/, /^<a[^>]*>$/
              matches = /href="([^"]*)"/.match(token) ||
                /href='([^']*)'/.match(token)
              link = matches[1] unless matches.nil?

              matches = /anchor="([^"]*)"/.match(token) ||
                /anchor='([^']*)'/.match(token)
              anchor = matches[1] unless matches.nil?

              matches = /local="([^"]*)"/.match(token) ||
                /local='([^']*)'/.match(token)
              local = matches[1] unless matches.nil?
            when /^<color[^>]*>$/
              matches = /rgb="#?([^"]*)"/.match(token) ||
                /rgb='#?([^']*)'/.match(token)
              colors << matches[1] if matches

              match = /c="#?([^"]*)"/.match(token) ||
                /c='#?([^']*)'/.match(token)
              c = Integer(match[1], 10) unless match.nil?
              match = /m="#?([^"]*)"/.match(token) ||
                /m='#?([^']*)'/.match(token)
              m = Integer(match[1], 10) unless match.nil?
              match = /y="#?([^"]*)"/.match(token) ||
                /y='#?([^']*)'/.match(token)
              y = Integer(match[1], 10) unless match.nil?
              match = /k="#?([^"]*)"/.match(token) ||
                /k='#?([^']*)'/.match(token)
              k = Integer(match[1], 10) unless match.nil?
              colors << [c, m, y, k] if [c, m, y, k].all?

              # intend to support rgb="#ffffff" or rgb='#ffffff',
              # r="255" g="255" b="255" or r='255' g='255' b='255',
              # and c="100" m="100" y="100" k="100" or
              # c='100' m='100' y='100' k='100'
              # color = { :rgb => "#ffffff" }
              # color = { :r => 255, :g => 255, :b => 255 }
              # color = { :c => 100, :m => 100, :y => 100, :k => 100 }
            when /^<font[^>]*>$/
              matches = /name="([^"]*)"/.match(token) ||
                /name='([^']*)'/.match(token)
              fonts << matches[1] unless matches.nil?

              matches = /size="([^"]*)"/.match(token) ||
                /size='([^']*)'/.match(token)
              sizes << Float(matches[1]) unless matches.nil?

              matches = /character_spacing="([^"]*)"/.match(token) ||
                /character_spacing='([^']*)'/.match(token)
              character_spacings << Float(matches[1]) unless matches.nil?
            else
              string = unescape(token)
              array << {
                text: string,
                styles: styles.dup,
                color: colors.last,
                local: local,
                link: link,
                anchor: anchor,
                font: fonts.last,
                size: sizes.last,
                character_spacing: character_spacings.last,
              }
            end
          end
          array
        end

        # Escape characters that can interfere with inline format parsing.
        #
        # @param text [String]
        # @return [String]
        def self.escape(text)
          text.gsub(Regexp.union(ESCAPE_CHARS.keys), ESCAPE_CHARS)
        end

        # Unescape characters that can interfere with inline format parsing.
        #
        # @param text [String]
        # @return [String]
        def self.unescape(text)
          text.gsub(Regexp.union(UNESCAPE_CHARS.keys), UNESCAPE_CHARS)
        end
      end
    end
  end
end