parser.rb

module Chesters
  class Invoice
    attr_accessor :number, :phone, :fax, :account_code,
                  :date, :payment_due, :sub_total, :total,
                  :gst, :sales_despatch, :sales_order,
                  :customer_order, :staff, :gst_no
    attr_accessor :line_items

    def initialize
      @line_items = []
    end
  end

  class LineItem
    attr_accessor :item_code, :description, :quantity,
                  :unit_amount, :price, :line_value, :list_price
  end

  class << self
    def parse(file_path)
      pdf_doc = PDF::Reader.new(file_path)

      @invoices = []

      pdf_doc.pages.each do |page|
        @invoice = Chesters::Invoice.new
        clean_page_lines = page.text.split("\n").delete_if { |val| val == "" }

        @table_start = false
        @table_end = false
        @table_meta_done = false

        clean_page_lines.each do |line|
          @invoice.date ||= invoice_date(line)
          @invoice.number ||= invoice_number(line, @invoice.number)
          @invoice.payment_due ||= payment_date(line)
          @invoice.account_code ||= customer(line)
          @invoice.gst_no ||= gst_number(line)
          @invoice.phone ||= phone(line)
          @invoice.fax ||= fax(line)

          table_start?(line)
          table_end?(line)

          if @table_end
            @invoice.sub_total ||= sub_total(line)
            @invoice.gst ||= gst(line)
            @invoice.total ||= total(line)
          end

          # break if @table_end
          unless @invoice.total.nil?
            @page_end = true
            break
          end

          @invoice.sales_despatch ||= sales_despatch(line) if @table_start && !@table_meta_done
          if @table_start && !@table_meta_done
            table_meta(line, @invoice)
            next if @table_meta_done
          end

          if @table_start && @table_meta_done && !@table_end
            li = build_line_item(line)
            @invoice.line_items << li if li
          end
        end

        @invoices << @invoice
      end

      @invoices
    end

    private

    def table_start?(line)
      if line.include_each?(['Item', 'Description', 'Quantity', 'Unit', 'Unit Price', 'Line valu', 'List Price']) ||
         (!@table_start && line.include_each?(['Quantity Unit', 'Unit Price', 'Line value', 'List Price']))
        @table_start = true
        return true
      end
      false
    end

    def table_end?(line)
      if line.include? 'For paying by Direct Credit, our bank details are'
        @table_end = true
        return true
      end
      false
    end

    def table_meta(line, invoice)
      return nil unless line.include_each? ['Sales order', 'Customer order', 'CreatedBy']

      params = line.split(/ {2,}/)
      invoice.sales_order = params[1]
      invoice.customer_order = params[3]
      invoice.staff = params[5]

      @table_meta_done = true
    end

    def compile(long, short)
      str = long.dup
      vals = short.strip.split(/ {2,}/)
      vals.each do |val|
        pos = short.index(val)
        val.each_char do |chr|
          str[pos] = chr
          pos += 1
        end
      end
      str
    end

    def build_line_item(line)
      values = line.strip.split(/ {2,}/)

      if @tmp_line
        new_line = line.size > @tmp_line.size ? compile(line, @tmp_line) : compile(@tmp_line, line)
        values = new_line.strip.split(/ {2,}/)
        @tmp_line = nil
      end

      if values.size < 6 && values.size > 1
        @tmp_line = line
        return nil
      end

      return nil if values.size < 2

      line_item = Chesters::LineItem.new

      line_item.item_code = values[0]
      line_item.description = values[1]
      line_item.quantity = values[2].split(' ').first
      line_item.unit_amount = values[2].split(' ').last
      line_item.price = values[3]
      line_item.line_value = values[4]
      line_item.list_price = values[5]

      defined?(line_item) ? line_item : nil
    end

    def invoice_number(line, invoice_number)
      line[/[0-9]+/] if line.include?('Tax Invoice Number') ||
                        (invoice_number.nil? &&
                        line.split(' ').size == 2 &&
                        line[/ [A-Z]{2} /] &&
                        line[/ [0-9]+/])
    end

    def invoice_date(line)
      line[/([0-9]{1,2}\/){2}[0-9]{4}/] if line[/Invoice date/i]
    end

    def payment_date(line)
      line[/([0-9]{1,2}\/){2}[0-9]{4}/] if line.include? 'Payment due'
    end

    def customer(line)
      line.split(' ').last if line.include? 'Customer'
    end

    def gst_number(line)
      line[/[0-9]*-[0-9]*-[0-9]*/] if line.include? 'GST Number'
    end

    def phone(line)
      line[/[0-9]{1} [0-9]{3} [0-9]{4}/] if line.include? 'Phone:'
    end

    def fax(line)
      line[/[0-9]{1} [0-9]{3} [0-9]{4}/] if line.include? 'Fax:'
    end

    def sales_despatch(line)
      line.split(' ').last if line.include? 'Sales despatch'
    end

    def sub_total(line)
      line.split(' ').last(2).first if line.include?('Subtotal')
    end

    def gst(line)
      line.split(' ').last(2).first if line.include?('GST')
    end

    def total(line)
      line.split(' ').last(2).first if line.include?('Total')
    end
  end
end