# taken from irb
# Implements tab completion for Readline in Pry
class Pry::InputCompleter
  NUMERIC_REGEXP            = /^(-?(0[dbo])?[0-9_]+(\.[0-9_]+)?([eE]-?[0-9]+)?)\.([^.]*)$/
  ARRAY_REGEXP              = /^([^\]]*\])\.([^.]*)$/
  SYMBOL_REGEXP             = /^(:[^:.]*)$/
  SYMBOL_METHOD_CALL_REGEXP = /^(:[^:.]+)\.([^.]*)$/
  REGEX_REGEXP              = /^(\/[^\/]*\/)\.([^.]*)$/
  PROC_OR_HASH_REGEXP       = /^([^\}]*\})\.([^.]*)$/
  TOPLEVEL_LOOKUP_REGEXP    = /^::([A-Z][^:\.\(]*)$/
  CONSTANT_REGEXP           = /^([A-Z][A-Za-z0-9]*)$/
  CONSTANT_OR_METHOD_REGEXP = /^([A-Z].*)::([^:.]*)$/
  HEX_REGEXP                = /^(-?0x[0-9a-fA-F_]+)\.([^.]*)$/
  GLOBALVARIABLE_REGEXP     = /^(\$[^.]*)$/
  VARIABLE_REGEXP           = /^([^."].*)\.([^.]*)$/

  ReservedWords = [
                   "BEGIN", "END",
                   "alias", "and",
                   "begin", "break",
                   "case", "class",
                   "def", "defined", "do",
                   "else", "elsif", "end", "ensure",
                   "false", "for",
                   "if", "in",
                   "module",
                   "next", "nil", "not",
                   "or",
                   "redo", "rescue", "retry", "return",
                   "self", "super",
                   "then", "true",
                   "undef", "unless", "until",
                   "when", "while",
                   "yield" ]

  Operators = [
               "%", "&", "*", "**", "+", "-", "/",
               "<", "<<", "<=", "<=>", "==", "===", "=~", ">", ">=", ">>",
               "[]", "[]=", "^", "!", "!=", "!~"
              ]

  WORD_ESCAPE_STR = " \t\n\"\\'`><=;|&{("

  def initialize(input, pry = nil)
    @pry = pry
    @input = input
    @input.basic_word_break_characters = WORD_ESCAPE_STR if @input.respond_to?(:basic_word_break_characters=)
    @input.completion_append_character = nil if @input.respond_to?(:completion_append_character=)
  end

  #
  # Return a new completion proc for use by Readline.
  #
  def call(str, options = {})
    custom_completions = options[:custom_completions] || []
    # if there are multiple contexts e.g. cd 1/2/3
    # get new target for 1/2 and find candidates for 3
    path, input = build_path(str)

    if path.call.empty?
      target = options[:target]
    else
      # Assume the user is tab-completing the 'cd' command
      begin
        target = Pry::ObjectPath.new(path.call, @pry.binding_stack).resolve.last
      # but if that doesn't work, assume they're doing division with no spaces
      rescue Pry::CommandError
        target = options[:target]
      end
    end

    begin
      bind = target
      # Complete stdlib symbols
      case input
      when REGEX_REGEXP # Regexp
        receiver = $1
        message = Regexp.quote($2)
        candidates = Regexp.instance_methods.collect(&:to_s)
        select_message(path, receiver, message, candidates)
      when ARRAY_REGEXP # Array
        receiver = $1
        message = Regexp.quote($2)
        candidates = Array.instance_methods.collect(&:to_s)
        select_message(path, receiver, message, candidates)
      when PROC_OR_HASH_REGEXP # Proc or Hash
        receiver = $1
        message = Regexp.quote($2)
        candidates = Proc.instance_methods.collect(&:to_s)
        candidates |= Hash.instance_methods.collect(&:to_s)
        select_message(path, receiver, message, candidates)
      when SYMBOL_REGEXP # Symbol
        if Symbol.respond_to?(:all_symbols)
          sym        = Regexp.quote($1)
          candidates = Symbol.all_symbols.collect{|s| ":" << s.id2name}
          candidates.grep(/^#{sym}/)
        else
          []
        end
      when TOPLEVEL_LOOKUP_REGEXP # Absolute Constant or class methods
        receiver = $1
        candidates = Object.constants.collect(&:to_s)
        candidates.grep(/^#{receiver}/).collect{|e| "::" << e}
      when CONSTANT_REGEXP # Constant
        message = $1
        begin
          context = target.eval("self")
          context = context.class unless context.respond_to? :constants
          candidates = context.constants.collect(&:to_s)
        rescue
          candidates = []
        end
        candidates = candidates.grep(/^#{message}/).collect(&path)
      when CONSTANT_OR_METHOD_REGEXP # Constant or class methods
        receiver = $1
        message = Regexp.quote($2)
        begin
          candidates = eval("#{receiver}.constants.collect(&:to_s)", bind)
          candidates |= eval("#{receiver}.methods.collect(&:to_s)", bind)
        rescue Pry::RescuableException
          candidates = []
        end
        candidates.grep(/^#{message}/).collect{|e| receiver + "::" + e}
      when SYMBOL_METHOD_CALL_REGEXP # method call on a Symbol
        receiver = $1
        message = Regexp.quote($2)
        candidates = Symbol.instance_methods.collect(&:to_s)
        select_message(path, receiver, message, candidates)
      when NUMERIC_REGEXP
        # Numeric
        receiver = $1
        message = Regexp.quote($5)
        begin
          candidates = eval(receiver, bind).methods.collect(&:to_s)
        rescue Pry::RescuableException
          candidates = []
        end
        select_message(path, receiver, message, candidates)
      when HEX_REGEXP
        # Numeric(0xFFFF)
        receiver = $1
        message = Regexp.quote($2)
        begin
          candidates = eval(receiver, bind).methods.collect(&:to_s)
        rescue Pry::RescuableException
          candidates = []
        end
        select_message(path, receiver, message, candidates)
      when GLOBALVARIABLE_REGEXP # global
        regmessage = Regexp.new(Regexp.quote($1))
        candidates = global_variables.collect(&:to_s).grep(regmessage)
      when VARIABLE_REGEXP # variable
        receiver = $1
        message = Regexp.quote($2)

        gv = eval("global_variables", bind).collect(&:to_s)
        lv = eval("local_variables", bind).collect(&:to_s)
        cv = eval("self.class.constants", bind).collect(&:to_s)

        if (gv | lv | cv).include?(receiver) or /^[A-Z]/ =~ receiver && /\./ !~ receiver
          # foo.func and foo is local var. OR
          # Foo::Bar.func
          begin
            candidates = eval("#{receiver}.methods", bind).collect(&:to_s)
          rescue Pry::RescuableException
            candidates = []
          end
        else
          # func1.func2
          require 'set'
          candidates = Set.new
          to_ignore = ignored_modules
          ObjectSpace.each_object(Module){|m|
            next if (to_ignore.include?(m) rescue true)

            # jruby doesn't always provide #instance_methods() on each
            # object.
            if m.respond_to?(:instance_methods)
              candidates.merge m.instance_methods(false).collect(&:to_s)
            end
          }
        end
        select_message(path, receiver, message, candidates.sort)
      when /^\.([^.]*)$/
        # Unknown(maybe String)
        receiver = ""
        message = Regexp.quote($1)
        candidates = String.instance_methods(true).collect(&:to_s)
        select_message(path, receiver, message, candidates)
      else
        candidates = eval(
                          "methods | private_methods | local_variables | " \
                          "self.class.constants | instance_variables",
                          bind
                          ).collect(&:to_s)

        if eval("respond_to?(:class_variables)", bind)
          candidates += eval("class_variables", bind).collect(&:to_s)
        end
        candidates = (candidates|ReservedWords|custom_completions).grep(/^#{Regexp.quote(input)}/)
        candidates.collect(&path)
      end
    rescue Pry::RescuableException
      []
    end
  end

  def select_message(path, receiver, message, candidates)
    candidates.grep(/^#{message}/).collect { |e|
      case e
      when /^[a-zA-Z_]/
        path.call(receiver + "." << e)
      when /^[0-9]/
      when *Operators
        #receiver + " " << e
      end
    }.compact
  end

  # build_path seperates the input into two parts: path and input.
  # input is the partial string that should be completed
  # path is a proc that takes an input and builds a full path.
  def build_path(input)
    # check to see if the input is a regex
    return proc {|i| i.to_s }, input if input[/\/\./]

    trailing_slash = input.end_with?('/')
    contexts = input.chomp('/').split(/\//)
    input = contexts[-1]
    path = proc do |i|
      p = contexts[0..-2].push(i).join('/')
      p += '/' if trailing_slash && !i.nil?
      p
    end
    return path, input
  end

  def ignored_modules
    # We could cache the result, but IRB is not loaded by default.
    # And this is very fast anyway.
    # By using this approach, we avoid Module#name calls, which are
    # relatively slow when there are a lot of anonymous modules defined.
    s = Set.new

    scanner = lambda do |m|
      next if s.include?(m) # IRB::ExtendCommandBundle::EXCB recurses.

      s << m
      m.constants(false).each do |c|
        value = m.const_get(c)
        scanner.call(value) if value.is_a?(Module)
      end
    end

    # FIXME: Add Pry here as well?
    [:IRB, :SLex, :RubyLex, :RubyToken].each do |module_name|
      next unless Object.const_defined?(module_name)

      scanner.call(Object.const_get(module_name))
    end

    s.delete(IRB::Context) if defined?(IRB::Context)
    s
  end
end