require 'facter'
require 'jgrep'

module FacterDB
  module Errors
    class InvalidFilter < RuntimeError; end
  end

  # @return [String] -  returns a giant incomprehensible string of concatenated json data
  def self.database
    @database ||= "[#{facterdb_fact_files.map { |f| read_json_file(f) }.join(',')}]\n"
  end

  # @note Call this method at the end of test suite, for example via after(:suite), to reclaim back the memory required to hold json data and filter cache
  def self.cleanup
    @database = nil
    Thread.current[:facterdb_last_filter_seen] = nil
    Thread.current[:facterdb_last_facts_seen] = nil
  end

  # @return [Boolean] - returns true if we should use the default facterdb database, false otherwise
  # @note If the user passes anything to the FACTERDB_SKIP_DEFAULTDB environment variable we assume
  # they want to skip the default db
  def self.use_defaultdb?
    ENV['FACTERDB_SKIP_DEFAULTDB'].nil?
  end

  # @return [Boolean] - returns true if we should inject the source file name and file path into the json factsets.
  # The default is false.
  def self.inject_source?
    !ENV['FACTERDB_INJECT_SOURCE'].nil?
  end

  def self.read_json_file(f)
    content = File.read(f)
    return content unless inject_source?
    # Find the opening brace
    first_brace = content.index('{')
    return content if first_brace.nil?
    # Inject source file information
    json_injection =  "\"_facterdb_filename\": #{File.basename(f).to_json}, "
    json_injection += "\"_facterdb_path\": #{File.expand_path(f).to_json}, "
    content.insert(first_brace + 1, json_injection)
  end
  private_class_method :read_json_file

  # @return [Array[String]] -  list of all files found in the default facterdb facts path
  def self.default_fact_files
    return [] unless use_defaultdb?
    proj_root = File.join(File.dirname(File.dirname(__FILE__)))
    facts_dir = File.expand_path(File.join(proj_root, 'facts'))
    Dir.glob(File.join(facts_dir, "**", '*.facts'))
  end

  # @return [Array[String]] -  list of all files found in the user supplied facterdb facts path
  # @param fact_paths [String] - a comma separated list of paths to search for fact files
  def self.external_fact_files(fact_paths = ENV['FACTERDB_SEARCH_PATHS'])
    fact_paths ||= ''
    return [] if fact_paths.empty?
    paths = fact_paths.split(File::PATH_SEPARATOR).map do |fact_path|
      unless File.directory?(fact_path)
        warn("[FACTERDB] Ignoring external facts path #{fact_path} as it is not a directory")
        next nil
      end
      fact_path = fact_path.gsub(File::ALT_SEPARATOR, File::SEPARATOR) if File::ALT_SEPARATOR
      File.join(fact_path.strip, '**', '*.facts')
    end.compact
    Dir.glob(paths)
  end

  # @return [Array[String]] -  list of all files found in the default facterdb facts path and user supplied path
  # @note external fact files supplied by the user will take precedence over default fact files found in this gem
  def self.facterdb_fact_files
    (external_fact_files + default_fact_files).uniq
  end

  def self.get_os_facts(facter_version='*', filter=[])
    if facter_version == '*'
      if filter.is_a?(Array)
        filter_str = filter.map { |f| f.map { |k,v | "#{k}=#{v}" }.join(' and ') }.join(' or ')
      elsif filter.is_a?(Hash)
        filter_str = filter.map { |k,v | "#{k}=#{v}" }.join(' and ')
      elsif filter.is_a?(String)
        filter_str = filter
      else
        raise 'filter must be either an Array a Hash or a String'
      end
    else
      if filter.is_a?(Array)
        filter_str = "facterversion=/^#{facter_version}/ and (#{filter.map { |f| f.map { |k,v | "#{k}=#{v}" }.join(' and ') }.join(' or ')})"
      elsif filter.is_a?(Hash)
        filter_str = "facterversion=/^#{facter_version}/ and (#{filter.map { |k,v | "#{k}=#{v}" }.join(' and ')})"
      elsif filter.is_a?(String)
        filter_str = "facterversion=/^#{facter_version}/ and (#{filter})"
      else
        raise 'filter must be either an Array a Hash or a String'
      end
    end

    warn "[DEPRECATION] `get_os_facts` is deprecated. Please use `get_facts(#{filter_str})` instead."

    get_facts(filter_str)
  end

  # @return [String] - the string filter
  # @param filter [Object] - The filter to convert to jgrep string
  def self.generate_filter_str(filter=nil)
    case filter
    when ::Array
      '(' + filter.map { |f| f.map { |k,v | "#{k}=#{v}" }.join(' and ') }.join(') or (') + ')'
    when ::Hash
      filter.map { |k,v | "#{k}=#{v}" }.join(' and ')
    when ::String
      filter
    when ::NilClass
      ''
    else
      raise Errors::InvalidFilter, "filter must be either an Array a Hash, String, or nil, received #{filter.class}"
    end
  end

  # @return [Boolean] - true if the filter is valid against the jgrep filter validator
  # @param filter [Object] - The filter to convert to jgrep string
  def self.valid_filters?(filters)
    filter_str = generate_filter_str(filters)
    JGrep.validate_filters(filter_str).nil?
  rescue RuntimeError
    false
  end

  # @return [Array] - array of hashes of facts
  # @param filter [Object] - The filter to convert to jgrep string
  def self.get_facts(filter=nil, cache=true)
    if cache && filter && filter == Thread.current[:facterdb_last_filter_seen]
      return Thread.current[:facterdb_last_facts_seen]
    end
    filter_str = generate_filter_str(filter)
    result = JGrep.jgrep(database, filter_str).map { |hash| Hash[hash.map{ |k, v| [k.to_sym, v] }] }
    if cache
      Thread.current[:facterdb_last_filter_seen] = filter
      Thread.current[:facterdb_last_facts_seen] = result
    end
    result
  end
end