module Log2mail
  class Config

    class <<self
      def parse_config(config_path)
        Log2mail::Config.new(config_path)
        # pp config.config
        # config.files.each do |f|
        #   puts "File: #{f}"
        #   config.patterns_for_file(f).each do |pattern|
        #     puts "  Pattern: #{pattern}; mailto: " + config.mailtos_for_pattern( f, pattern ).join(', ')
        #   end
        # end
      end
    end

    # attr_reader :config

    INT_OPTIONS = [:sendtime, :resendtime, :maxlines]
    STR_OPTIONS = [:fromaddr, :sendmail]
    PATH_OPTIONS = [:template]

    def initialize(config_paths)
      $logger.debug "Reading configuration from #{config_paths}"
      @config_paths = Array(config_paths)
      expand_paths
      read_configuration
      validate_configuration
    end

    # returns all the paths of all files needed to be watched
    def files
      @config.keys - [:defaults]
    end

    def file_patterns
      h = {}
      files.each do |file|
        h[file] = patterns_for_file(file)
      end
      h
    end

    def patterns_for_file( file )
      Hash(@config[file][:patterns]).keys + \
      Hash(defaults[:patterns]).keys
    end

    def mailtos_for_pattern( file, pattern )
      m = []
      m.concat Hash( config_file_pattern(file, pattern)[:mailtos] ).keys
      m.concat Hash(Hash(Hash(defaults[:patterns])[pattern])[:mailtos]).keys
      m.concat Array(defaults[:mailtos]) if m.empty?
      m.uniq
    end

    def settings_for_mailto( file, pattern, mailto )
      h = defaults.reject {|k,v| k==:mailtos}
      h.merge config_file_mailto(file, pattern, mailto)
    end

    def defaults
      Hash(@config[:defaults])
    end

    def formatted( show_effective )
      Terminal::Table.new do |t|
        settings_header = show_effective ? 'Effective Settings' : 'Settings'
        t << ['File', 'Pattern', 'Recipient', settings_header]
        t << :separator
        files.each do |file|
          patterns_for_file(file).each do |pattern|
            mailtos_for_pattern(file, pattern).each do |mailto|
              settings = []
              if show_effective
                settings_for_mailto(file, pattern, mailto).each_pair \
                  { |k,v| settings << '%s=%s' % [k,v] }
              else
                config_file_mailto(file, pattern, mailto).each_pair \
                  { |k,v| settings << '%s=%s' % [k,v] }
              end
              t.add_row [file, pattern, mailto, settings.join($/)]
            end
          end
        end
      end
    end

    private

    def config_file(file)
      Hash(@config[file])
    end

    def config_file_pattern(file, pattern)
      Hash( Hash( config_file(file)[:patterns] )[pattern] )
    end

    def config_file_mailtos(file, pattern)
      Hash( config_file_pattern(file, pattern)[:mailtos] )
    end

    def config_file_mailto(file, pattern, mailto)
      Hash( config_file_mailtos(file, pattern)[mailto] )
    end

    def expand_paths
      expanded_paths = []
      @config_paths.each do |path|
        if ::File.directory?(path)
          expanded_paths.concat Dir.glob( ::File.join( path, '*[^~#]' ) )
        else
          expanded_paths << path
        end
      end
      @config_paths = expanded_paths
    end

    # tries to follow original code at https://github.com/lordlamer/log2mail/blob/master/config.cc#L192
    def read_configuration
      @config = {}
      @config_paths.each do |file|
        @section = nil; @pattern = nil; @mailto = nil
        # section, pattern, mailto are reset for every file (but not when included by 'include')
        parse_file( file )
      end
    end

    def parse_file( filename )
      IO.readlines(filename).each_with_index do |line, lineno|
        parse(filename, line, lineno + 1)
      end
    rescue Errno::ENOENT
      fail Error, "Configuration file or directory not found (or not readable): #{filename}"
    end

    def parse(file, line, lineno)
      line.strip!
      return if line =~ /^#/
      return if line =~ /^$/
      line =~ /^(\S+)\s*=?\s*"?(.*?)"?(\s*#.*)?$/  # drop double quotes on right hand side; drop comments
      key, value = $1.to_sym, $2.strip
      if key == :include # include shall work everywhere
        parse_file( ::File.join(Pathname(file).parent, value) )
        return
      end
      if key == :defaults and value.empty?  # section: specifies top level; must be 'defaults' or 'file'
        @section = key
        @pattern = nil; @mailto = nil
        fail Error, "Invalid section. Section 'defaults' already specified." if @config[@section]
        @config[@section] = {}
      elsif key == :file
        @section = value
        @pattern = nil; @mailto = nil
        @config[@section] ||= {}
      elsif key == :pattern # must come inside 'file' (or 'defaults')
        # fail "Invalid section. All statements must appear after 'defaults' or 'file=...'" unless @section
        @pattern = value; @mailto = nil
        @config[@section][:patterns] ||= {}
        warning { "Redefining pattern section '#{value}' which has been defined already for '#{@section}'." } \
          if @config[@section][:patterns][value]
        @config[@section][:patterns][value] = {}
      elsif key == :mailto and @section != :defaults # must come inside 'pattern' (or 'defaults')
        fail Error, "'mailto' statements only allowed inside 'pattern' or 'defaults'." unless @pattern
        @mailto = value
        @config[@section][:patterns][@pattern][:mailtos] ||= {}
        warning { "Redefining mailto section '#{value}' which has been defined already for '#{@section}'." } \
          if @config[@section][:patterns][@pattern][:mailtos][value]
        @config[@section][:patterns][@pattern][:mailtos][value] = {}
      else # everything else must come inside 'defaults' or 'mailto'
        fail Error, "'#{key}' must be set within 'defaults' or 'mailto'." unless @section == :defaults or @mailto
        if INT_OPTIONS.include?(key)
          value = value.to_i
        elsif STR_OPTIONS.include?(key)
        elsif PATH_OPTIONS.include?(key)
          value = ::File.expand_path( value, Pathname(file).parent ) unless Pathname(value).absolute?
        elsif key == :mailto # special handling for 'mailto' in 'defaults' section
          @config[:defaults][:mailtos] ||= []
          @config[:defaults][:mailtos] << value
          return # skip the 'mailto' entry itself
        else
          fail Error, "'#{key}' is an unknown configuration statement."
        end
        if @section == :defaults and !@pattern and !@mailto
          warning { "Redefining value for '#{key}'." } if @config[@section][key]
          @config[@section][key] = value
        else
          warning { "Redefining value for '#{key}'." } \
            if @config[@section][:patterns][@pattern][:mailtos][@mailto][key]
          @config[@section][:patterns][@pattern][:mailtos][@mailto][key] = value
        end
      end
    rescue
      fail Error, "#{file} (line #{lineno}): #{$!.message}#$/[#{$!.class} at #{$!.backtrace.first}]"
    end

    def validate_configuration
      files.each do |file|
        patterns_for_file(file).each do |pattern|
          mailtos = mailtos_for_pattern(file, pattern)
          $logger.warn "Pattern #{file}:#{pattern} has no recipients." if mailtos.empty?
        end
      end
      # FIXME: empty configuration should cause FATAL error
      # TODO: illegal regexp pattern should cause ERROR
    end

    def warning(&block)
      file = block.binding.eval('file')
      lineno = block.binding.eval('lineno')
      message = block.call
      $logger.warn "#{file} (line #{lineno}): #{message}#$/[at #{caller.first}]"
    end

  end
end