# encoding: utf-8

require "logstash/filters/base"
require "logstash/namespace"

# This filter helps automatically parse messages (or specific event fields)
# which are of the `foo=bar` variety.
#
# For example, if you have a log message which contains `ip=1.2.3.4
# error=REFUSED`, you can parse those automatically by configuring:
# [source,ruby]
#     filter {
#       kv { }
#     }
#
# The above will result in a message of `ip=1.2.3.4 error=REFUSED` having
# the fields:
#
# * `ip: 1.2.3.4`
# * `error: REFUSED`
#
# This is great for postfix, iptables, and other types of logs that
# tend towards `key=value` syntax.
#
# You can configure any arbitrary strings to split your data on,
# in case your data is not structured using `=` signs and whitespace.
# For example, this filter can also be used to parse query parameters like
# `foo=bar&baz=fizz` by setting the `field_split` parameter to `&`.
class LogStash::Filters::KV < LogStash::Filters::Base
  config_name "kv"

  # Constants used for transform check
  TRANSFORM_LOWERCASE_KEY = "lowercase"
  TRANSFORM_UPPERCASE_KEY = "uppercase"
  TRANSFORM_CAPITALIZE_KEY = "capitalize"

  # A string of characters to trim from the value. This is useful if your
  # values are wrapped in brackets or are terminated with commas (like postfix
  # logs).
  #
  # These characters form a regex character class and thus you must escape special regex
  # characters like `[` or `]` using `\`.
  #
  # For example, to strip `<`, `>`, `[`, `]` and `,` characters from values:
  # [source,ruby]
  #     filter {
  #       kv {
  #         trim => "<>\[\],"
  #       }
  #     }
  config :trim, :validate => :string

  # A string of characters to trim from the key. This is useful if your
  # keys are wrapped in brackets or start with space.
  #
  # These characters form a regex character class and thus you must escape special regex
  # characters like `[` or `]` using `\`.
  #
  # For example, to strip `<` `>` `[` `]` and `,` characters from keys:
  # [source,ruby]
  #     filter {
  #       kv {
  #         trimkey => "<>\[\],"
  #       }
  #     }
  config :trimkey, :validate => :string

  # Transform values to lower case, upper case or capitals.
  #
  # For example, to capitalize all values:
  # [source,ruby]
  #     filter {
  #       kv {
  #         transform_value => "capitalize"
  #       }
  #     }
  config :transform_value, :validate => [TRANSFORM_LOWERCASE_KEY, TRANSFORM_UPPERCASE_KEY, TRANSFORM_CAPITALIZE_KEY]

  # Transform keys to lower case, upper case or capitals.
  #
  # For example, to lowercase all keys:
  # [source,ruby]
  #     filter {
  #       kv {
  #         transform_key => "lowercase"
  #       }
  #     }
  config :transform_key, :validate => [TRANSFORM_LOWERCASE_KEY, TRANSFORM_UPPERCASE_KEY, TRANSFORM_CAPITALIZE_KEY]

  # A string of characters to use as delimiters for parsing out key-value pairs.
  #
  # These characters form a regex character class and thus you must escape special regex
  # characters like `[` or `]` using `\`.
  #
  # #### Example with URL Query Strings
  #
  # For example, to split out the args from a url query string such as
  # `?pin=12345~0&d=123&e=foo@bar.com&oq=bobo&ss=12345`:
  # [source,ruby]
  #     filter {
  #       kv {
  #         field_split => "&?"
  #       }
  #     }
  #
  # The above splits on both `&` and `?` characters, giving you the following
  # fields:
  #
  # * `pin: 12345~0`
  # * `d: 123`
  # * `e: foo@bar.com`
  # * `oq: bobo`
  # * `ss: 12345`
  config :field_split, :validate => :string, :default => ' '


  # A non-empty string of characters to use as delimiters for identifying key-value relations.
  #
  # These characters form a regex character class and thus you must escape special regex
  # characters like `[` or `]` using `\`.
  #
  # For example, to identify key-values such as
  # `key1:value1 key2:value2`:
  # [source,ruby]
  #     filter { kv { value_split => ":" } }
  config :value_split, :validate => :string, :default => '='

  # A string to prepend to all of the extracted keys.
  #
  # For example, to prepend arg_ to all keys:
  # [source,ruby]
  #     filter { kv { prefix => "arg_" } }
  config :prefix, :validate => :string, :default => ''

  # The field to perform `key=value` searching on
  #
  # For example, to process the `not_the_message` field:
  # [source,ruby]
  #     filter { kv { source => "not_the_message" } }
  config :source, :validate => :string, :default => "message"

  # The name of the container to put all of the key-value pairs into.
  #
  # If this setting is omitted, fields will be written to the root of the
  # event, as individual fields.
  #
  # For example, to place all keys into the event field kv:
  # [source,ruby]
  #     filter { kv { target => "kv" } }
  config :target, :validate => :string

  # An array specifying the parsed keys which should be added to the event.
  # By default all keys will be added.
  #
  # For example, consider a source like `Hey, from=<abc>, to=def foo=bar`.
  # To include `from` and `to`, but exclude the `foo` key, you could use this configuration:
  # [source,ruby]
  #     filter {
  #       kv {
  #         include_keys => [ "from", "to" ]
  #       }
  #     }
  config :include_keys, :validate => :array, :default => []

  # An array specifying the parsed keys which should not be added to the event.
  # By default no keys will be excluded.
  #
  # For example, consider a source like `Hey, from=<abc>, to=def foo=bar`.
  # To exclude `from` and `to`, but retain the `foo` key, you could use this configuration:
  # [source,ruby]
  #     filter {
  #       kv {
  #         exclude_keys => [ "from", "to" ]
  #       }
  #     }
  config :exclude_keys, :validate => :array, :default => []

  # A hash specifying the default keys and their values which should be added to the event
  # in case these keys do not exist in the source field being parsed.
  # [source,ruby]
  #     filter {
  #       kv {
  #         default_keys => [ "from", "logstash@example.com",
  #                          "to", "default@dev.null" ]
  #       }
  #     }
  config :default_keys, :validate => :hash, :default => {}

  # A bool option for removing duplicate key/value pairs. When set to false, only
  # one unique key/value pair will be preserved.
  #
  # For example, consider a source like `from=me from=me`. `[from]` will map to
  # an Array with two elements: `["me", "me"]`. to only keep unique key/value pairs,
  # you could use this configuration:
  # [source,ruby]
  #     filter {
  #       kv {
  #         allow_duplicate_values => false
  #       }
  #     }
  config :allow_duplicate_values, :validate => :boolean, :default => true

  # A boolean specifying whether to treat square brackets, angle brackets,
  # and parentheses as value "wrappers" that should be removed from the value.
  # [source,ruby]
  #     filter {
  #       kv {
  #         include_brackets => true
  #       }
  #     }
  #
  # For example, the result of this line:
  # `bracketsone=(hello world) bracketstwo=[hello world] bracketsthree=<hello world>`
  #
  # will be:
  #
  # * bracketsone: hello world
  # * bracketstwo: hello world
  # * bracketsthree: hello world
  #
  # instead of:
  #
  # * bracketsone: (hello
  # * bracketstwo: [hello
  # * bracketsthree: <hello
  #
  config :include_brackets, :validate => :boolean, :default => true

  # A boolean specifying whether to drill down into values
  # and recursively get more key-value pairs from it.
  # The extra key-value pairs will be stored as subkeys of the root key.
  #
  # Default is not to recursive values.
  # [source,ruby]
  #     filter {
  #       kv {
  #         recursive => "true"
  #       }
  #     }
  #
  config :recursive, :validate => :boolean, :default => false

  def register
    if @value_split.empty?
      raise LogStash::ConfigurationError, I18n.t(
        "logstash.agent.configuration.invalid_plugin_register",
        :plugin => "filter",
        :type => "kv",
        :error => "Configuration option 'value_split' must be a non-empty string"
      )
    end

    @trim_re = Regexp.new("[#{@trim}]") if @trim
    @trimkey_re = Regexp.new("[#{@trimkey}]") if @trimkey

    valueRxString = "(?:\"([^\"]+)\"|'([^']+)'"
    valueRxString += "|\\(([^\\)]+)\\)|\\[([^\\]]+)\\]|<([^>]+)>" if @include_brackets
    valueRxString += "|((?:\\\\ |[^" + @field_split + "])+))"
    @scan_re = Regexp.new("((?:\\\\ |[^" + @field_split + @value_split + "])+)\s*[" + @value_split + "]\s*" + valueRxString)
    @value_split_re = /[#{@value_split}]/
  end

  def filter(event)
    kv = Hash.new
    value = event[@source]

    case value
    when nil
      # Nothing to do
    when String
      kv = parse(value, event, kv)
    when Array
      value.each { |v| kv = parse(v, event, kv) }
    else
      @logger.warn("kv filter has no support for this type of data", :type => value.class, :value => value)
    end

    # Add default key-values for missing keys
    kv = @default_keys.merge(kv)

    return if kv.empty?

    if @target
      @logger.debug? && @logger.debug("Overwriting existing target field", :target => @target)
      event[@target] = kv
    else
      kv.each{|k, v| event[k] = v}
    end

    filter_matched(event)
  end

  private

  def has_value_splitter?(s)
    s =~ @value_split_re
  end

  def transform(text, method)
    case method
    when TRANSFORM_LOWERCASE_KEY
      return text.downcase
    when TRANSFORM_UPPERCASE_KEY
      return text.upcase
    when TRANSFORM_CAPITALIZE_KEY
      return text.capitalize
    end
  end

  def parse(text, event, kv_keys)
    # short circuit parsing if the text does not contain the @value_split
    return kv_keys unless has_value_splitter?(text)

    # Interpret dynamic keys for @include_keys and @exclude_keys
    include_keys = @include_keys.map{|key| event.sprintf(key)}
    exclude_keys = @exclude_keys.map{|key| event.sprintf(key)}

    text.scan(@scan_re) do |key, v1, v2, v3, v4, v5, v6|
      value = v1 || v2 || v3 || v4 || v5 || v6
      key = @trimkey ? key.gsub(@trimkey_re, "") : key
      key = @transform_key ? transform(key, @transform_key) : key

      # Bail out as per the values of include_keys and exclude_keys
      next if not include_keys.empty? and not include_keys.include?(key)
      # next unless include_keys.include?(key)
      next if exclude_keys.include?(key)

      key = event.sprintf(@prefix) + key

      value = @trim ? value.gsub(@trim_re, "") : value
      value = @transform_value ? transform(value, @transform_value) : value

      # Bail out if inserting duplicate value in key mapping when unique_values
      # option is set to true.
      next if not @allow_duplicate_values and kv_keys.has_key?(key) and kv_keys[key].include?(value)

      # recursively get more kv pairs from the value
      if @recursive
        innerKv = parse(value, event, {})
        value = innerKv unless innerKv.empty?
      end

      if kv_keys.has_key?(key)
        if kv_keys[key].is_a?(Array)
          kv_keys[key].push(value)
        else
          kv_keys[key] = [kv_keys[key], value]
        end
      else
        kv_keys[key] = value
      end
    end

    return kv_keys
  end
end