=begin
  Copyright (C) 2005 Jeff Rose
  Copyright (C) 2005 Sam Roberts
    
  This library is free software; you can redistribute it and/or modify it
  under the same terms as the ruby language itself, see the file COPYING for
  details.
=end

require 'date'
require 'uri'

module Icalendar
  class Parser < Icalendar::Base
    # 1*(ALPHA / DIGIT / "=")
    NAME    = '[-a-z0-9]+'
    
    # <"> <Any character except CTLs, DQUOTE> <">
    QSTR    = '"[^"]*"'

    # *<Any character except CTLs, DQUOTE, ";", ":", ",">
    PTEXT   = '[^";:,]*'

    # param-value = ptext / quoted-string
    PVALUE  = "#{PTEXT}|#{QSTR}"

    # Contentline
    LINE = "(#{NAME})([^:]*)\:(.*)"

    # param = name "=" param-value *("," param-value)
    PARAM = ";(#{NAME})(=?)((?:#{PVALUE})(?:,#{PVALUE})*)"

    # date = date-fullyear ["-"] date-month ["-"] date-mday
    # date-fullyear = 4 DIGIT
    # date-month = 2 DIGIT
    # date-mday = 2 DIGIT
    DATE = '(\d\d\d\d)-?(\d\d)-?(\d\d)'

    # time = time-hour [":"] time-minute [":"] time-second [time-secfrac] [time-zone]
    # time-hour = 2 DIGIT
    # time-minute = 2 DIGIT
    # time-second = 2 DIGIT
    # time-secfrac = "," 1*DIGIT
    # time-zone = "Z" / time-numzone
    # time-numzome = sign time-hour [":"] time-minute
    TIME = '(\d\d):?(\d\d):?(\d\d)(\.\d+)?(Z|[-+]\d\d:?\d\d)?'

    def initialize(src)
      @@logger.debug("New Calendar Parser")
      
      # Setup the parser method hash table
      setup_parsers()

      # Define the next line method different depending on whether
      # this is a string or an IO object so we can be efficient about
      # parsing large files...
      
      # Just do the unfolding work in one shot if its a whole string
      if src.respond_to?(:split)
        unfolded = []

        # Split into an array of lines, then unfold those into a new array
        src.split(/\r?\n/).each do |line|

          # If it's a continuation line, add it to the last.
          # If it's an empty line, drop it from the input.
          if( line =~ /^[ \t]/ )
            unfolded << unfolded.pop + line[1, line.size-1]
          elsif( line =~ /^$/ )
          else
            unfolded << line
          end
        end

        @lines = unfolded
        @index = 0

        # Now that we are unfolded we can just iterate through the array.
        # Dynamically define next line for a string.
        def next_line
          if @index == @lines.size
            return nil
          else
            line = @lines[@index]
            @index += 1
            return line
          end
        end

        # If its a file we need to read and unfold on the go to save from reading
        # large amounts of data into memory.
      elsif src.respond_to?(:gets)
        @file = src
        @prev_line = src.gets
        if !@prev_line.nil?
          @prev_line.chomp!
        end
        
        # Dynamically define next line for an IO object
        def next_line
          line = @prev_line
          
          if line.nil? 
            return nil 
          end

          # Loop through until we get to a non-continuation line...
          loop do
            nextLine = @file.gets
            if !nextLine.nil?
              nextLine.chomp!
            end
            
            # If it's a continuation line, add it to the last.
            # If it's an empty line, drop it from the input.
            if( nextLine =~ /^[ \t]/ )
              line << nextLine[1, nextLine.size]
            elsif( nextLine =~ /^$/ )
            else
              @prev_line = nextLine
              break
            end
          end
          line
        end
      else
        raise ArgumentError, "CalendarParser.new cannot be called with a #{src.class} type!"
      end
    end
    
    # Parse the calendar into an object representation
    def parse
      calendars = []
      
      # Outer loop for Calendar objects
      while (line = next_line)
        fields = parse_line(line)
        
        # Just iterate through until we find the beginning of a calendar object
        if fields[:name] == "BEGIN" and fields[:value] == "VCALENDAR"
          cal = parse_component
          calendars << cal
        end
      end
      
      calendars
    end

    private
    
    # Parse a single VCALENDAR object
    # -- This should consist of the PRODID, VERSION, option METHOD & CALSCALE,
    # and then one or more calendar components: VEVENT, VTODO, VJOURNAL, 
    # VFREEBUSY, VTIMEZONE
    def parse_component(component = Calendar.new)
      while (line = next_line)
        fields = parse_line(line)

        name = fields[:name]
        
        # Although properties are supposed to come before components, we should
        # be able to handle them in any order...
        if name == "END"
          break
        elsif name == "BEGIN" # New component
          case(fields[:value])
          when "VEVENT"
            component.events << parse_component(Event.new)
          when "VTODO"
            component.todos << parse_component(Todo.new)
          when "VJOURNAL"
            component.journals << parse_component(Journal.new)
          when "VFREEBUSY"
            component.freebusys << parse_component(Freebusy.new)
          when "VTIMEZONE"
            component.timezones << parse_component(Timezone.new)
          when "VALARM"
            component.alarms << parse_component(Alarm.new)
          end
        else # If its not a component then it should be a property
          
          # Just set the properties so that the parser can still
          # parse invalid files...
          @@logger.debug("Setting #{name} => #{fields[:value]}")
          
          # Lookup the property name to see if we have a string to
          # object parser for this property type.
          if @parsers.has_key?(name.upcase)
            val = @parsers[name.upcase].call(name, fields[:params], fields[:value])
          else
            val = fields[:value]
          end

          if component.multi_property?(name.upcase) && component.properties
            val = [val]

            if fields[:params].empty?
              params = [nil]
            else
              params = fields[:params]
            end
            
            if component.properties.has_key?(name)
              component.properties[name] += val
              component.property_params[name] += params
            else
              component.properties[name] = val
              component.property_params[name] = params
            end

          else
            component.properties[name] = val            

            unless fields[:params].empty?
              component.property_params[name] = fields[:params]
            end
          end
        end  
      end

      component

    end

    def parse_line(line)
      unless line =~ %r{#{LINE}}i # Case insensitive match for a valid line
        raise "Invalid line in calendar string!"
      end

      name = $1.upcase # The case insensitive part is upcased for easier comparison...
      paramslist = $2
      value = $3
      
      params = {}
      
      # Collect the params, if any.
      if paramslist.size > 1
        
        # v3.0 and v2.1 params
        paramslist.scan( %r{#{PARAM}}i ) do
          
          # param names are case-insensitive, and multi-valued
          pname = $1
          pvals = $3
          
          # v2.1 pvals have no '=' sign, figure out what kind of param it
          # is (either its a known encoding, or we treat it as a 'type'
          # param).
          if $2 == ""
            pvals = $1
            case $1
            when /quoted-printable/i
              pname = 'encoding'
              
            when /base64/i
              pname = 'encoding'
              
            else
              pname = 'type'
            end
          end
          
          unless params.key? pname
            params[pname] = []
          end
          pvals.scan( %r{(#{PVALUE})} ) do
            if $1.size > 0
              params[pname] << $1
            end
          end
        end
      end
      
      {:name => name, :params => params, :value => value}
    end
    
    ## Following is a collection of parsing functions for various 
    ## icalendar property value data types...  First we setup
    ## a hash with property names pointing to methods...
    def setup_parsers
      @parsers = {}

      # Integer properties
      m = self.method(:parse_integer)
      @parsers["PERCENT-COMPLETE"] = m
      @parsers["PRIORITY"] = m
      @parsers["REPEAT"] = m
      @parsers["SEQUENCE"] = m

      # Dates and Times
      m = self.method(:parse_datetime)
      @parsers["COMPLETED"] = m
      @parsers["DTEND"] = m
      @parsers["DUE"] = m
      @parsers["DTSTART"] = m
      @parsers["RECURRENCE-ID"] = m
      @parsers["EXDATE"] = m
      @parsers["RDATE"] = m
      @parsers["CREATED"] = m
      @parsers["DTSTAMP"] = m
      @parsers["LAST-MODIFIED"] = m

      # URI's
      m = self.method(:parse_uri)
      @parsers["TZURL"] = m
      @parsers["ATTENDEE"] = m
      @parsers["ORGANIZER"] = m
      @parsers["URL"] = m
      
      # This is a URI by default, and if its not a valid URI
      # it will be returned as a string which works for binary data
      # the other possible type.
      @parsers["ATTACH"] = m 

      # GEO
      m = self.method(:parse_geo)
      @parsers["GEO"] = m

    end
    
    # Booleans
    # NOTE: It appears that although this is a valid data type
    # there aren't any properties that use it...  Maybe get
    # rid of this in the future.
    def parse_boolean(name, params, value)
      if value.upcase == "FALSE"
        false
      else
        true
      end
    end
    
    # Dates, Date-Times & Times
    # NOTE: invalid dates & times will be returned as strings...
    def parse_datetime(name, params, value)
      begin
        DateTime.parse(value)
      rescue Exception
        value
      end
      
    end
    
    # Durations
    # TODO: Need to figure out the best way to represent durations 
    # so just returning string for now.
    def parse_duration(name, params, value)
      value
    end
    
    # Floats
    # NOTE: returns 0.0 if it can't parse the value
    def parse_float(name, params, value)
      value.to_f
    end
    
    # Integers
    # NOTE: returns 0 if it can't parse the value
    def parse_integer(name, params, value)
      value.to_i
    end
    
    # Periods
    # TODO: Got to figure out how to represent periods also...
    def parse_period(name, params, value)
      value
    end
    
    # Calendar Address's & URI's
    # NOTE: invalid URI's will be returned as strings...
    def parse_uri(name, params, value)
      begin
        URI.parse(value)
      rescue Exception
        value
      end
    end

    # Geographical location (GEO)
    # NOTE: returns an array with two floats (long & lat)
    # if the parsing fails return the string
    def parse_geo(name, params, value)
      strloc = value.split(';')
      if strloc.size != 2 
        return value
      end

      val = []
      val[0] = strloc[0].to_f
      val[1] = strloc[1].to_f
      val
    end
    
  end
end