A simple Ruby program to support indexing in Jekyll

jekyll-index-term.rb

require 'digest/sha1'

module Jekyll

	module JekyllIndexTermFilter

		# html display name, index name
		def getnames(matchedString)
			stripped = matchedString.strip()
			matchResult = stripped.match(/(?<!\\)@/)
			if matchResult == nil then
				[stripped, stripped]
			else
				indexLeft = [Regexp.last_match.begin(0) - 1, 0].max
				htmlStr = stripped[0..indexLeft].strip()
				indexStr = stripped[Regexp.last_match.begin(0)+1..-1].strip()
				[htmlStr, indexStr]
			end
		end

		def parsecontent(pattern, content, warnDuplicate)
			rawIndexTerms = content.scan(pattern)
			tagConv = Hash.new

			counter = Hash.new(0)

			for expr in rawIndexTerms do
				names = getnames(expr[0])
				hashCode = Digest::SHA1.hexdigest(names[1])
				names.append(hashCode)
				counter[names[1]] += 1
				tagConv[expr[0]] = names
			end

			if warnDuplicate then
				counter.each do |k, v|
					if v > 1 then
						puts "\e[33mwarning: index term \"#{k}\" appeared #{v} times!\e[0m"
					end
				end
			end

			tagConv
		end

		def indexedbody(content)
			pattern = /%{(?!#)(.*?)}%/
			tagConv = parsecontent(pattern, content, true)

			# substitute normal tags
			tagStyle = '<span class="indexed-term-style"><a name="%s"></a>%s</span>'
			result = content.gsub(pattern){|s| tagStyle % [tagConv[$1][2], tagConv[$1][0]]}

			tagLookup = Hash.new
			tagConv.each do |k, v|
				tagLookup[v[1]] = '#' + v[2]
			end

			# substitue special tags
			specialPattern = /%{#(.*?)}%/
			result = result.gsub(specialPattern){|s|
				# get command and arguments
				spaceLoc = $1.index(' ')
				cmd = $1[0..spaceLoc - 1]
				if cmd == 'get_link' then
					totalCmd = $1[spaceLoc + 1..-1]
					#puts totalCmd
					tagLookup.fetch(totalCmd, $1)
				else
					puts "\e[33mwarning: invalid command \"#{cmd}\" detected\e[0m"
					$1
				end
			}

			result
		end

		def indexedterms(content)
			pattern = /%{(.*?)}%/
			tagConv = parsecontent(pattern, content, false)

			allTags = Array.new
			tagConv.each do |key, val|
				indexName = val[1].downcase
				allTags.append([indexName, val[2]])
			end
			allTags = allTags.sort{|a, b| a[0] <=> b[0]}

			indexTermStyle = '<a class="index-a" href="#%s">%s</a>'
			allLinks = Array.new

			for item in allTags do
				link = indexTermStyle % [item[1], item[0]]
				allLinks.append(link)
			end

			allLinks.join(' • ')
		end

	end

end

Liquid::Template.register_filter(Jekyll::JekyllIndexTermFilter)