# frozen_string_literal: true

module YARP
  # This represents a source of Ruby code that has been parsed. It is used in
  # conjunction with locations to allow them to resolve line numbers and source
  # ranges.
  class Source
    attr_reader :source, :offsets

    def initialize(source, offsets = compute_offsets(source))
      @source = source
      @offsets = offsets
    end

    def slice(offset, length)
      source.byteslice(offset, length)
    end

    def line(value)
      offsets.bsearch_index { |offset| offset > value } || offsets.length
    end

    def line_offset(value)
      offsets[line(value) - 1]
    end

    def column(value)
      value - offsets[line(value) - 1]
    end

    private

    def compute_offsets(code)
      offsets = [0]
      code.b.scan("\n") { offsets << $~.end(0) }
      offsets
    end
  end

  # This represents a location in the source.
  class Location
    # A Source object that is used to determine more information from the given
    # offset and length.
    protected attr_reader :source

    # The byte offset from the beginning of the source where this location
    # starts.
    attr_reader :start_offset

    # The length of this location in bytes.
    attr_reader :length

    # The list of comments attached to this location
    attr_reader :comments

    def initialize(source, start_offset, length)
      @source = source
      @start_offset = start_offset
      @length = length
      @comments = []
    end

    # Create a new location object with the given options.
    def copy(**options)
      Location.new(
        options.fetch(:source) { source },
        options.fetch(:start_offset) { start_offset },
        options.fetch(:length) { length }
      )
    end

    # Returns a string representation of this location.
    def inspect
      "#<YARP::Location @start_offset=#{@start_offset} @length=#{@length}>"
    end

    # The source code that this location represents.
    def slice
      source.slice(start_offset, length)
    end

    # The byte offset from the beginning of the source where this location ends.
    def end_offset
      start_offset + length
    end

    # The line number where this location starts.
    def start_line
      source.line(start_offset)
    end

    # The content of the line where this location starts before this location.
    def start_line_slice
      offset = source.line_offset(start_offset)
      source.slice(offset, start_offset - offset)
    end

    # The line number where this location ends.
    def end_line
      source.line(end_offset - 1)
    end

    # The column number in bytes where this location starts from the start of
    # the line.
    def start_column
      source.column(start_offset)
    end

    # The column number in bytes where this location ends from the start of the
    # line.
    def end_column
      source.column(end_offset)
    end

    def deconstruct_keys(keys)
      { start_offset: start_offset, end_offset: end_offset }
    end

    def pretty_print(q)
      q.text("(#{start_offset}...#{end_offset})")
    end

    def ==(other)
      other.is_a?(Location) &&
        other.start_offset == start_offset &&
        other.end_offset == end_offset
    end

    # Returns a new location that stretches from this location to the given
    # other location. Raises an error if this location is not before the other
    # location or if they don't share the same source.
    def join(other)
      raise "Incompatible sources" if source != other.source
      raise "Incompatible locations" if start_offset > other.start_offset

      Location.new(source, start_offset, other.end_offset - start_offset)
    end

    def self.null
      new(0, 0)
    end
  end

  # This represents a comment that was encountered during parsing.
  class Comment
    TYPES = [:inline, :embdoc, :__END__]

    attr_reader :type, :location

    def initialize(type, location)
      @type = type
      @location = location
    end

    def deconstruct_keys(keys)
      { type: type, location: location }
    end

    # Returns true if the comment happens on the same line as other code and false if the comment is by itself
    def trailing?
      type == :inline && !location.start_line_slice.strip.empty?
    end

    def inspect
      "#<YARP::Comment @type=#{@type.inspect} @location=#{@location.inspect}>"
    end
  end

  # This represents an error that was encountered during parsing.
  class ParseError
    attr_reader :message, :location

    def initialize(message, location)
      @message = message
      @location = location
    end

    def deconstruct_keys(keys)
      { message: message, location: location }
    end

    def inspect
      "#<YARP::ParseError @message=#{@message.inspect} @location=#{@location.inspect}>"
    end
  end

  # This represents a warning that was encountered during parsing.
  class ParseWarning
    attr_reader :message, :location

    def initialize(message, location)
      @message = message
      @location = location
    end

    def deconstruct_keys(keys)
      { message: message, location: location }
    end

    def inspect
      "#<YARP::ParseWarning @message=#{@message.inspect} @location=#{@location.inspect}>"
    end
  end

  # A class that knows how to walk down the tree. None of the individual visit
  # methods are implemented on this visitor, so it forces the consumer to
  # implement each one that they need. For a default implementation that
  # continues walking the tree, see the Visitor class.
  class BasicVisitor
    def visit(node)
      node&.accept(self)
    end

    def visit_all(nodes)
      nodes.map { |node| visit(node) }
    end

    def visit_child_nodes(node)
      visit_all(node.child_nodes)
    end
  end

  class Visitor < BasicVisitor
  end

  # This represents the result of a call to ::parse or ::parse_file. It contains
  # the AST, any comments that were encounters, and any errors that were
  # encountered.
  class ParseResult
    attr_reader :value, :comments, :errors, :warnings, :source

    def initialize(value, comments, errors, warnings, source)
      @value = value
      @comments = comments
      @errors = errors
      @warnings = warnings
      @source = source
    end

    def deconstruct_keys(keys)
      { value: value, comments: comments, errors: errors, warnings: warnings }
    end

    def success?
      errors.empty?
    end

    def failure?
      !success?
    end
  end

  # This represents a token from the Ruby source.
  class Token
    attr_reader :type, :value, :location

    def initialize(type, value, location)
      @type = type
      @value = value
      @location = location
    end

    def deconstruct_keys(keys)
      { type: type, value: value, location: location }
    end

    def pretty_print(q)
      q.group do
        q.text(type.to_s)
        self.location.pretty_print(q)
        q.text("(")
        q.nest(2) do
          q.breakable("")
          q.pp(value)
        end
        q.breakable("")
        q.text(")")
      end
    end

    def ==(other)
      other.is_a?(Token) &&
        other.type == type &&
        other.value == value
    end
  end

  # This represents a node in the tree.
  class Node
    attr_reader :location

    def newline?
      @newline ? true : false
    end

    def set_newline_flag(newline_marked)
      line = location.start_line
      unless newline_marked[line]
        newline_marked[line] = true
        @newline = true
      end
    end

    # Slice the location of the node from the source.
    def slice
      location.slice
    end

    def pretty_print(q)
      q.text(inspect.chomp)
    end
  end

  # This object is responsible for generating the output for the inspect method
  # implementations of child nodes.
  class NodeInspector
    attr_reader :prefix, :output

    def initialize(prefix = "")
      @prefix = prefix
      @output = +""
    end

    # Appends a line to the output with the current prefix.
    def <<(line)
      output << "#{prefix}#{line}"
    end

    # This generates a string that is used as the header of the inspect output
    # for any given node.
    def header(node)
      output = +"@ #{node.class.name.split("::").last} ("
      output << "location: (#{node.location.start_offset}...#{node.location.end_offset})"
      output << ", newline: true" if node.newline?
      output << ")\n"
      output
    end

    # Generates a string that represents a list of nodes. It handles properly
    # using the box drawing characters to make the output look nice.
    def list(prefix, nodes)
      output = +"(length: #{nodes.length})\n"
      last_index = nodes.length - 1

      nodes.each_with_index do |node, index|
        pointer, preadd = (index == last_index) ? ["└── ", "    "] : ["├── ", "│   "]
        node_prefix = "#{prefix}#{preadd}"
        output << node.inspect(NodeInspector.new(node_prefix)).sub(node_prefix, "#{prefix}#{pointer}")
      end

      output
    end

    # Generates a string that represents a location field on a node.
    def location(value)
      if value
        "(#{value.start_offset}...#{value.end_offset}) = #{value.slice.inspect}"
      else
        "∅"
      end
    end

    # Generates a string that represents a child node.
    def child_node(node, append)
      node.inspect(child_inspector(append)).delete_prefix(prefix)
    end

    # Returns a new inspector that can be used to inspect a child node.
    def child_inspector(append)
      NodeInspector.new("#{prefix}#{append}")
    end

    # Returns the output as a string.
    def to_str
      output
    end
  end

  # Load the serialized AST using the source as a reference into a tree.
  def self.load(source, serialized)
    Serialize.load(source, serialized)
  end

  # This module is used for testing and debugging and is not meant to be used by
  # consumers of this library.
  module Debug
    class ISeq
      attr_reader :parts

      def initialize(parts)
        @parts = parts
      end

      def type
        parts[0]
      end

      def local_table
        parts[10]
      end

      def instructions
        parts[13]
      end

      def each_child
        instructions.each do |instruction|
          # Only look at arrays. Other instructions are line numbers or
          # tracepoint events.
          next unless instruction.is_a?(Array)

          instruction.each do |opnd|
            # Only look at arrays. Other operands are literals.
            next unless opnd.is_a?(Array)

            # Only look at instruction sequences. Other operands are literals.
            next unless opnd[0] == "YARVInstructionSequence/SimpleDataFormat"

            yield ISeq.new(opnd)
          end
        end
      end
    end

    # For the given source, compiles with CRuby and returns a list of all of the
    # sets of local variables that were encountered.
    def self.cruby_locals(source)
      verbose = $VERBOSE
      $VERBOSE = nil

      begin
        locals = []
        stack = [ISeq.new(RubyVM::InstructionSequence.compile(source).to_a)]

        while (iseq = stack.pop)
          if iseq.type != :once
            names = iseq.local_table

            # CRuby will push on a special local variable when there are keyword
            # arguments. We get rid of that here.
            names = names.grep_v(Integer)

            # TODO: We don't support numbered local variables yet, so we get rid
            # of those here.
            names = names.grep_v(/^_\d$/)

            # For some reason, CRuby occasionally pushes this special local
            # variable when there are splat arguments. We get rid of that here.
            names = names.grep_v(:"#arg_rest")

            # Now push them onto the list of locals.
            locals << names
          end

          iseq.each_child { |child| stack << child }
        end

        locals
      ensure
        $VERBOSE = verbose
      end
    end

    # For the given source, parses with YARP and returns a list of all of the
    # sets of local variables that were encountered.
    def self.yarp_locals(source)
      locals = []
      stack = [YARP.parse(source).value]

      while (node = stack.pop)
        case node
        when BlockNode, DefNode, LambdaNode
          names = node.locals

          params = node.parameters
          params = params&.parameters unless node.is_a?(DefNode)

          # YARP places parameters in the same order that they appear in the
          # source. CRuby places them in the order that they need to appear
          # according to their own internal calling convention. We mimic that
          # order here so that we can compare properly.
          if params
            sorted = [
              *params.requireds.grep(RequiredParameterNode).map(&:name),
              *params.optionals.map(&:name),
              *((params.rest.name || :*) if params.rest && params.rest.operator != ","),
              *params.posts.grep(RequiredParameterNode).map(&:name),
              *params.keywords.reject(&:value).map(&:name),
              *params.keywords.select(&:value).map(&:name)
            ]

            # TODO: When we get a ... parameter, we should be pushing * and &
            # onto the local list. We don't do that yet, so we need to add them
            # in here.
            if params.keyword_rest.is_a?(ForwardingParameterNode)
              sorted.push(:*, :&, :"...")
            end

            # Recurse down the parameter tree to find any destructured
            # parameters and add them after the other parameters.
            param_stack = params.requireds.concat(params.posts).grep(RequiredDestructuredParameterNode).reverse
            while (param = param_stack.pop)
              case param
              when RequiredDestructuredParameterNode
                param_stack.concat(param.parameters.reverse)
              when RequiredParameterNode
                sorted << param.name
              when SplatNode
                sorted << param.expression.name if param.expression
              end
            end

            names = sorted.concat(names - sorted)
          end

          locals << names
        when ClassNode, ModuleNode, ProgramNode, SingletonClassNode
          locals << node.locals
        when ForNode
          locals << []
        when PostExecutionNode
          locals.push([], [])
        when InterpolatedRegularExpressionNode
          locals << [] if node.once?
        end

        stack.concat(node.child_nodes.compact)
      end

      locals
    end

    def self.newlines(source)
      YARP.parse(source).source.offsets
    end

    def self.parse_serialize_file(filepath)
      parse_serialize_file_metadata(filepath, [filepath.bytesize, filepath.b, 0].pack("LA*L"))
    end
  end

  # Marking this as private so that consumers don't see it. It makes it a little
  # annoying for testing since you have to const_get it to access the methods,
  # but at least this way it's clear it's not meant for consumers.
  private_constant :Debug
end

require_relative "yarp/lex_compat"
require_relative "yarp/mutation_visitor"
require_relative "yarp/desugar_visitor"
require_relative "yarp/node"
require_relative "yarp/ripper_compat"
require_relative "yarp/serialize"
require_relative "yarp/pack"
require_relative "yarp/pattern"

require_relative "yarp/parse_result/comments"
require_relative "yarp/parse_result/newlines"

if RUBY_ENGINE == "ruby" and !ENV["YARP_FFI_BACKEND"]
  require "yarp/yarp"
else
  require_relative "yarp/ffi"
end

# Reopening the YARP module after yarp/node is required so that constant
# reflection APIs will find the constants defined in the node file before these.
# This block is meant to contain extra APIs we define on YARP nodes that aren't
# templated and are meant as convenience methods.
module YARP
  class FloatNode < Node
    # Returns the value of the node as a Ruby Float.
    def value
      Float(slice)
    end
  end

  class ImaginaryNode < Node
    # Returns the value of the node as a Ruby Complex.
    def value
      Complex(0, numeric.value)
    end
  end

  class IntegerNode < Node
    # Returns the value of the node as a Ruby Integer.
    def value
      Integer(slice)
    end
  end

  class InterpolatedRegularExpressionNode < Node
    # Returns a numeric value that represents the flags that were used to create
    # the regular expression. This mirrors the Regexp#options method in Ruby.
    # Note that this is effectively masking only the three common flags that are
    # used in Ruby, and does not include the full set of flags like encoding.
    def options
      flags & 0b111
    end
  end

  class RationalNode < Node
    # Returns the value of the node as a Ruby Rational.
    def value
      Rational(slice.chomp("r"))
    end
  end

  class RegularExpressionNode < Node
    # Returns a numeric value that represents the flags that were used to create
    # the regular expression. This mirrors the Regexp#options method in Ruby.
    # Note that this is effectively masking only the three common flags that are
    # used in Ruby, and does not include the full set of flags like encoding.
    def options
      flags & 0b111
    end
  end
end