require 'pry/code/loc'
require 'pry/code/code_range'

class Pry
  class << self
    # Convert the given object into an instance of `Pry::Code`, if it isn't
    # already one.
    #
    # @param [Code, Method, UnboundMethod, Proc, Pry::Method, String, Array,
    #   IO] obj
    def Code(obj)
      case obj
      when Code
        obj
      when ::Method, UnboundMethod, Proc, Pry::Method
        Code.from_method(obj)
      else
        Code.new(obj)
      end
    end
  end

  # `Pry::Code` is a class that encapsulates lines of source code and their
  # line numbers and formats them for terminal output. It can read from a file
  # or method definition or be instantiated with a `String` or an `Array`.
  #
  # In general, the formatting methods in `Code` return a new `Code` object
  # which will format the text as specified when `#to_s` is called. This allows
  # arbitrary chaining of formatting methods without mutating the original
  # object.
  class Code

    # List of all supported languages.
    # @return [Hash]
    EXTENSIONS = {
      %w(.py)        => :python,
      %w(.js)        => :javascript,
      %w(.css)       => :css,
      %w(.xml)       => :xml,
      %w(.php)       => :php,
      %w(.html)      => :html,
      %w(.diff)      => :diff,
      %w(.java)      => :java,
      %w(.json)      => :json,
      %w(.c .h)      => :c,
      %w(.rhtml)     => :rhtml,
      %w(.yaml .yml) => :yaml,
      %w(.cpp .hpp .cc .h cxx) => :cpp,
      %w(.rb .ru .irbrc .gemspec .pryrc) => :ruby,
    }

    class << self
      include MethodSource::CodeHelpers

      # Instantiate a `Code` object containing code loaded from a file or
      # Pry's line buffer.
      #
      # @param [String] filename The name of a file, or "(pry)".
      # @param [Symbol] code_type The type of code the file contains.
      # @return [Code]
      def from_file(filename, code_type = type_from_filename(filename))
        code = if filename == Pry.eval_path
                 Pry.line_buffer.drop(1)
               else
                 File.read(abs_path(filename))
               end
        new(code, 1, code_type)
      end

      # Instantiate a `Code` object containing code extracted from a
      # `::Method`, `UnboundMethod`, `Proc`, or `Pry::Method` object.
      #
      # @param [::Method, UnboundMethod, Proc, Pry::Method] meth The method
      #   object.
      # @param [Integer, nil] start_line The line number to start on, or nil to
      #   use the method's original line numbers.
      # @return [Code]
      def from_method(meth, start_line = nil)
        meth = Pry::Method(meth)
        start_line ||= meth.source_line || 1
        new(meth.source, start_line, meth.source_type)
      end

      # Attempt to extract the source code for module (or class) `mod`.
      #
      # @param [Module, Class] mod The module (or class) of interest.
      # @param [Integer] candidate_rank The module candidate (by rank)
      #   to use (see `Pry::WrappedModule::Candidate` for more information).
      # @param [Integer, nil] start_line The line number to start on, or nil to
      #   use the method's original line numbers.
      # @return [Code]
      def from_module(mod, candidate_rank = 0, start_line=nil)
        candidate = Pry::WrappedModule(mod).candidate(candidate_rank)
        start_line ||= candidate.line
        new(candidate.source, start_line, :ruby)
      end

      protected

      # Guess the CodeRay type of a file from its extension, or nil if
      # unknown.
      #
      # @param [String] filename
      # @param [Symbol] default (:ruby) the file type to assume if none could be
      #   detected.
      # @return [Symbol, nil]
      def type_from_filename(filename, default = :ruby)
        _, type = Pry::Code::EXTENSIONS.find do |k, _|
          k.any? { |ext| ext == File.extname(filename) }
        end

        type || default
      end

      # @param [String] filename
      # @raise [MethodSource::SourceNotFoundError] if the +filename+ is not
      #   readable for some reason.
      # @return [String] absolute path for the given +filename+.
      def abs_path(filename)
        abs_path = [File.expand_path(filename, Dir.pwd),
                    File.expand_path(filename, Pry::INITIAL_PWD)
                   ].detect { |path| File.readable?(path) }
        abs_path or raise MethodSource::SourceNotFoundError,
                          "Cannot open #{filename.inspect} for reading."
      end
    end

    # @return [Symbol] The type of code stored in this wrapper.
    attr_accessor :code_type

    # Instantiate a `Code` object containing code from the given `Array`,
    # `String`, or `IO`. The first line will be line 1 unless specified
    # otherwise. If you need non-contiguous line numbers, you can create an
    # empty `Code` object and then use `#push` to insert the lines.
    #
    # @param [Array<String>, String, IO] lines
    # @param [Integer?] start_line
    # @param [Symbol?] code_type
    def initialize(lines = [], start_line = 1, code_type = :ruby)
      if lines.is_a? String
        lines = lines.lines
      end
      @lines = lines.each_with_index.map { |line, lineno|
        LOC.new(line, lineno + start_line.to_i) }
      @code_type = code_type
    end

    # Append the given line. +lineno+ is one more than the last existing
    # line, unless specified otherwise.
    #
    # @param [String] line
    # @param [Integer?] lineno
    # @return [String] The inserted line.
    def push(line, lineno = nil)
      if lineno.nil?
        lineno = @lines.last.lineno + 1
      end
      @lines.push(LOC.new(line, lineno))
      line
    end
    alias << push

    # Filter the lines using the given block.
    #
    # @yield [LOC]
    # @return [Code]
    def select(&block)
      alter do
        @lines = @lines.select(&block)
      end
    end

    # Remove all lines that aren't in the given range, expressed either as a
    # `Range` object or a first and last line number (inclusive). Negative
    # indices count from the end of the array of lines.
    #
    # @param [Range, Integer] start_line
    # @param [Integer?] end_line
    # @return [Code]
    def between(start_line, end_line = nil)
      return self unless start_line

      code_range = CodeRange.new(start_line, end_line)

      alter do
        @lines = @lines[code_range.indices_range(@lines)] || []
      end
    end

    # Take `num_lines` from `start_line`, forward or backwards.
    #
    # @param [Integer] start_line
    # @param [Integer] num_lines
    # @return [Code]
    def take_lines(start_line, num_lines)
      start_idx =
        if start_line >= 0
          @lines.index { |loc| loc.lineno >= start_line } || @lines.length
        else
          [@lines.length + start_line, 0].max
        end

      alter do
        @lines = @lines.slice(start_idx, num_lines)
      end
    end

    # Remove all lines except for the +lines+ up to and excluding +lineno+.
    #
    # @param [Integer] lineno
    # @param [Integer] lines
    # @return [Code]
    def before(lineno, lines = 1)
      return self unless lineno

      select do |loc|
        loc.lineno >= lineno - lines && loc.lineno < lineno
      end
    end

    # Remove all lines except for the +lines+ on either side of and including
    # +lineno+.
    #
    # @param [Integer] lineno
    # @param [Integer] lines
    # @return [Code]
    def around(lineno, lines = 1)
      return self unless lineno

      select do |loc|
        loc.lineno >= lineno - lines && loc.lineno <= lineno + lines
      end
    end

    # Remove all lines except for the +lines+ after and excluding +lineno+.
    #
    # @param [Integer] lineno
    # @param [Integer] lines
    # @return [Code]
    def after(lineno, lines = 1)
      return self unless lineno

      select do |loc|
        loc.lineno > lineno && loc.lineno <= lineno + lines
      end
    end

    # Remove all lines that don't match the given `pattern`.
    #
    # @param [Regexp] pattern
    # @return [Code]
    def grep(pattern)
      return self unless pattern
      pattern = Regexp.new(pattern)

      select do |loc|
        loc.line =~ pattern
      end
    end

    # Format output with line numbers next to it, unless `y_n` is falsy.
    #
    # @param [Boolean?] y_n
    # @return [Code]
    def with_line_numbers(y_n = true)
      alter do
        @with_line_numbers = y_n
      end
    end

    # Format output with a marker next to the given +lineno+, unless +lineno+ is
    # falsy.
    #
    # @param [Integer?] lineno
    # @return [Code]
    def with_marker(lineno = 1)
      alter do
        @with_marker   = !!lineno
        @marker_lineno = lineno
      end
    end

    # Format output with the specified number of spaces in front of every line,
    # unless `spaces` is falsy.
    #
    # @param [Integer?] spaces
    # @return [Code]
    def with_indentation(spaces = 0)
      alter do
        @with_indentation = !!spaces
        @indentation_num  = spaces
      end
    end

    # @return [String]
    def inspect
      Object.instance_method(:to_s).bind(self).call
    end

    # @return [Integer] the number of digits in the last line.
    def max_lineno_width
      @lines.length > 0 ? @lines.last.lineno.to_s.length : 0
    end

    # @return [String] a formatted representation (based on the configuration of
    #   the object).
    def to_s
      @lines.map { |loc|
        loc = loc.dup
        loc.colorize(@code_type)              if Pry.color
        loc.add_line_number(max_lineno_width) if @with_line_numbers
        loc.add_marker(@marker_lineno)        if @with_marker
        loc.indent(@indentation_num)          if @with_indentation
        loc.line
      }.join("\n") + "\n"
    end

    # Get the comment that describes the expression on the given line number.
    #
    # @param [Integer] line_number (1-based)
    # @return [String] the code.
    def comment_describing(line_number)
      self.class.comment_describing(raw, line_number)
    end

    # Get the multiline expression that starts on the given line number.
    #
    # @param [Integer] line_number (1-based)
    # @return [String] the code.
    def expression_at(line_number, consume = 0)
      self.class.expression_at(raw, line_number, :consume => consume)
    end

    # Get the (approximate) Module.nesting at the give line number.
    #
    # @param [Integer] line_number line number starting from 1
    # @param [Module] top_module the module in which this code exists
    # @return [Array<Module>] a list of open modules.
    def nesting_at(line_number, top_module = Object)
      Pry::Indent.nesting_at(raw, line_number)
    end

    # Return an unformatted String of the code.
    #
    # @return [String]
    def raw
      @lines.map(&:line).join("\n") + "\n"
    end

    # Return the number of lines stored.
    #
    # @return [Integer]
    def length
      @lines ? @lines.length : 0
    end

    # Two `Code` objects are equal if they contain the same lines with the same
    # numbers. Otherwise, call `to_s` and `chomp` and compare as Strings.
    #
    # @param [Code, Object] other
    # @return [Boolean]
    def ==(other)
      if other.is_a?(Code)
        other_lines = other.instance_variable_get(:@lines)
        @lines.each_with_index.all? { |loc, i| loc == other_lines[i] }
      else
        to_s.chomp == other.to_s.chomp
      end
    end

    # Forward any missing methods to the output of `#to_s`.
    def method_missing(name, *args, &block)
      to_s.send(name, *args, &block)
    end
    undef =~

    protected

    # An abstraction of the `dup.instance_eval` pattern used throughout this
    # class.
    def alter(&block)
      dup.tap { |o| o.instance_eval(&block) }
    end
  end
end