# A mini-language for parsing files.  This is only used file the ParsedFile
# provider, but it makes more sense to split it out so it's easy to maintain
# in one place.
#
# You can use this module to create simple parser/generator classes.  For instance,
# the following parser should go most of the way to parsing /etc/passwd:
#
#   class Parser
#       include Puppet::Util::FileParsing
#       record_line :user, :fields => %w{name password uid gid gecos home shell},
#           :separator => ":"
#   end
#
# You would use it like this:
#
#   parser = Parser.new
#   lines = parser.parse(File.read("/etc/passwd"))
#
#   lines.each do |type, hash| # type will always be :user, since we only have one
#       p hash
#   end
#
# Each line in this case would be a hash, with each field set appropriately.
# You could then call 'parser.to_line(hash)' on any of those hashes to generate
# the text line again.

require 'puppet/util/methodhelper'

module Puppet::Util::FileParsing
    include Puppet::Util
    attr_writer :line_separator, :trailing_separator

    class FileRecord
        include Puppet::Util
        include Puppet::Util::MethodHelper
        attr_accessor :absent, :joiner, :rts, :separator, :rollup, :name, :match, :block_eval

        attr_reader :fields, :optional, :type

        INVALID_FIELDS = [:record_type, :target, :on_disk]

        # Customize this so we can do a bit of validation.
        def fields=(fields)
            @fields = fields.collect do |field|
                r = symbolize(field)
                if INVALID_FIELDS.include?(r)
                    raise ArgumentError.new("Cannot have fields named %s" % r)
                end
                r
            end
        end

        def initialize(type, options = {}, &block)
            @type = symbolize(type)
            unless [:record, :text].include?(@type)
                raise ArgumentError, "Invalid record type %s" % @type
            end

            set_options(options)

            if self.type == :record
                # Now set defaults.
                self.absent ||= ""
                self.separator ||= /\s+/
                self.joiner ||= " "
                self.optional ||= []
                unless defined? @rollup
                    @rollup = true
                end
            end

            if block_given?
                @block_eval ||= :process

                # Allow the developer to specify that a block should be instance-eval'ed.
                if @block_eval == :instance
                    instance_eval(&block)
                else
                    meta_def(@block_eval, &block)
                end
            end
        end

        # Convert a record into a line by joining the fields together appropriately.
        # This is pulled into a separate method so it can be called by the hooks.
        def join(details)
            joinchar = self.joiner

            fields.collect { |field|
                # If the field is marked absent, use the appropriate replacement
                if details[field] == :absent or details[field] == [:absent] or details[field].nil?
                    if self.optional.include?(field)
                        self.absent
                    else
                        raise ArgumentError, "Field '%s' is required" % field
                    end
                else
                    details[field].to_s
                end
            }.reject { |c| c.nil?}.join(joinchar)
        end

        # Customize this so we can do a bit of validation.
        def optional=(optional)
            @optional = optional.collect do |field|
                symbolize(field)
            end
        end

        # Create a hook that modifies the hash resulting from parsing.
        def post_parse=(block)
            meta_def(:post_parse, &block)
        end

        # Create a hook that modifies the hash just prior to generation.
        def pre_gen=(block)
            meta_def(:pre_gen, &block)
        end

        # Are we a text type?
        def text?
            type == :text
        end

        def to_line=(block)
            meta_def(:to_line, &block)
        end
    end

    # Clear all existing record definitions.  Only used for testing.
    def clear_records
        @record_types.clear
        @record_order.clear
    end

    def fields(type)
        if record = record_type(type)
            record.fields.dup
        else
            nil
        end
    end

    # Try to match a specific text line.
    def handle_text_line(line, record)
        if line =~ record.match
            return {:record_type => record.name, :line => line}
        else
            return nil
        end
    end

    # Try to match a record.
    def handle_record_line(line, record)
        ret = nil
        if record.respond_to?(:process)
            if ret = record.send(:process, line.dup)
                unless ret.is_a?(Hash)
                    raise Puppet::DevError,
                        "Process record type %s returned non-hash" % record.name
                end
            else
                return nil
            end
        elsif regex = record.match
            # In this case, we try to match the whole line and then use the
            # match captures to get our fields.
            if match = regex.match(line)
                fields = []
                ret = {}
                record.fields.zip(match.captures).each do |field, value|
                    if value == record.absent 
                        ret[field] = :absent
                    else
                        ret[field] = value
                    end
                end
            else
                nil
            end
        else
            ret = {}
            sep = record.separator

            # String "helpfully" replaces ' ' with /\s+/ in splitting, so we
            # have to work around it.
            if sep == " "
                sep = / /
            end
            line_fields = line.split(sep)
            record.fields.each do |param|
                value = line_fields.shift
                if value and value != record.absent
                    ret[param] = value
                else
                    ret[param] = :absent
                end
            end

            if record.rollup and ! line_fields.empty?
                last_field = record.fields[-1]
                val = ([ret[last_field]] + line_fields).join(record.joiner)
                ret[last_field] = val
            end
        end

        if ret
            ret[:record_type] = record.name
            return ret
        else
            return nil
        end
    end

    def line_separator
        unless defined?(@line_separator)
            @line_separator = "\n"
        end

        @line_separator
    end

    # Split text into separate lines using the record separator.
    def lines(text)
        # Remove any trailing separators, and then split based on them
        # LAK:NOTE See http://snurl.com/21zf8  [groups_google_com] 
        x = text.sub(/#{self.line_separator}\Q/,'').split(self.line_separator)
    end

    # Split a bunch of text into lines and then parse them individually.
    def parse(text)
        count = 1
        lines(text).collect do |line|
            count += 1
            if val = parse_line(line)
                val
            else
                error = Puppet::Error.new("Could not parse line %s" % line.inspect)
                error.line = count
                raise error
            end
        end
    end

    # Handle parsing a single line.
    def parse_line(line)
        unless records?
            raise Puppet::DevError, "No record types defined; cannot parse lines"
        end

        @record_order.each do |record|
            # These are basically either text or record lines.
            method = "handle_%s_line" % record.type
            if respond_to?(method)
                if result = send(method, line, record)
                    if record.respond_to?(:post_parse)
                        record.send(:post_parse, result)
                    end
                    return result
                end
            else
                raise Puppet::DevError,
                    "Somehow got invalid line type %s" % record.type
            end
        end

        return nil
    end

    # Define a new type of record.  These lines get split into hashes.  Valid
    # options are:
    # * <tt>:absent</tt>: What to use as value within a line, when a field is
    #   absent.  Note that in the record object, the literal :absent symbol is
    #   used, and not this value.  Defaults to "".
    # * <tt>:fields</tt>: The list of fields, as an array.  By default, all
    #   fields are considered required.
    # * <tt>:joiner</tt>: How to join fields together.  Defaults to '\t'.
    # * <tt>:optional</tt>: Which fields are optional.  If these are missing,
    #   you'll just get the 'absent' value instead of an ArgumentError.
    # * <tt>:rts</tt>: Whether to remove trailing whitespace.  Defaults to false.
    #   If true, whitespace will be removed; if a regex, then whatever matches
    #   the regex will be removed.
    # * <tt>:separator</tt>: The record separator.  Defaults to /\s+/.
    def record_line(name, options, &block)
        unless options.include?(:fields)
            raise ArgumentError, "Must include a list of fields"
        end

        record = FileRecord.new(:record, options, &block)
        record.name = symbolize(name)

        new_line_type(record)
    end

    # Are there any record types defined?
    def records?
        defined?(@record_types) and ! @record_types.empty?
    end

    # Define a new type of text record.
    def text_line(name, options, &block)
        unless options.include?(:match)
            raise ArgumentError, "You must provide a :match regex for text lines"
        end

        record = FileRecord.new(:text, options, &block)
        record.name = symbolize(name)

        new_line_type(record)
    end

    # Generate a file from a bunch of hash records.
    def to_file(records)
        text = records.collect { |record| to_line(record) }.join(line_separator)

        if trailing_separator
            text += line_separator
        end

        return text
    end

    # Convert our parsed record into a text record.
    def to_line(details)
        unless record = record_type(details[:record_type])
            raise ArgumentError, "Invalid record type %s" % details[:record_type].inspect
        end

        if record.respond_to?(:pre_gen)
            details = details.dup
            record.send(:pre_gen, details)
        end

        case record.type
        when :text: return details[:line]
        else
            if record.respond_to?(:to_line)
                return record.to_line(details)
            end

            line = record.join(details)

            if regex = record.rts
                # If they say true, then use whitespace; else, use their regex.
                if regex == true
                    regex = /\s+$/
                end
                return line.sub(regex,'')
            else
                return line
            end
        end
    end

    # Whether to add a trailing separator to the file.  Defaults to true
    def trailing_separator
        if defined? @trailing_separator
            return @trailing_separator
        else
            return true
        end
    end

    def valid_attr?(type, attr)
        type = symbolize(type)
        if record = record_type(type) and record.fields.include?(symbolize(attr))
            return true
        else
            if symbolize(attr) == :ensure
                return true
            else
                false
            end
        end
    end

    private

    # Define a new type of record.
    def new_line_type(record)
        @record_types ||= {}
        @record_order ||= []

        if @record_types.include?(record.name)
            raise ArgumentError, "Line type %s is already defined" % record.name
        end

        @record_types[record.name] = record
        @record_order << record

        return record
    end

    # Retrieve the record object.
    def record_type(type)
        @record_types[symbolize(type)]
    end
end