require 'fileutils'
require 'base64'
require 'tempfile'

module Mathematical
  class Render
    include Corrections

    FORMAT_TYPES = %w(svg png mathml)

    DEFAULT_OPTS = {
      ppi: 72.0,
      zoom: 1.0,
      base64: false,
      maxsize: 0,
      format: 'svg'
    }

    XML_HEADER = "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n"

    def initialize(opts = {})
      @config = DEFAULT_OPTS.merge(opts)

      validate_config

      @config[:formatInt] = FORMAT_TYPES.index(@config[:format])

      @processer = Mathematical::Process.new(@config)
    end

    def validate_config
      fail(TypeError, 'maxsize must be an integer!') unless @config[:maxsize].is_a? Fixnum
      fail(TypeError, 'maxsize cannot be less than 0!') if @config[:maxsize] < 0
      fail(TypeError, 'format must be a string!') unless @config[:format].is_a? String
      fail(TypeError, "format type must be one of the following formats: #{FORMAT_TYPES.join(', ')}") unless FORMAT_TYPES.include?(@config[:format])
    end

    def render(maths)
      maths = validate_content(maths)

      begin
        data_hash = @processer.process(maths)
        fail RuntimeError unless data_hash

        case @config[:format]
        when 'svg'
          # remove starting <?xml...> tag
          data_hash['svg'] = data_hash['svg'][XML_HEADER.length..-1]
          data_hash['svg'] = svg_to_base64(data_hash['svg']) if @config[:base64]
          data_hash
        when 'png', 'mathml'
          data_hash
        end
      rescue ParseError, DocumentCreationError, DocumentReadError => e
        # an error in the C code, probably a bad TeX parse
        $stderr.puts "#{e.message}: #{maths}"
        maths
      end
    end

    def validate_content(maths)
      fail(TypeError, 'text must be a string!') unless maths.is_a? String
      maths = maths.strip
      fail(ArgumentError, 'text must be in tex format (`$...$` or `$$...$$`)!') unless maths =~ /\A\${1,2}/
      apply_corrections(maths)
    end

    private

    def svg_to_base64(contents)
      "data:image/svg+xml;base64,#{Base64.strict_encode64(contents)}"
    end
  end
end