# frozen_string_literal: true
# :markup: markdown
# typed: ignore

# This file is responsible for mirroring the API provided by the C extension by
# using FFI to call into the shared library.

require "rbconfig"
require "ffi"

# We want to eagerly load this file if there are Ractors so that it does not get
# autoloaded from within a non-main Ractor.
require "prism/serialize" if defined?(Ractor)

module Prism # :nodoc:
  module LibRubyParser # :nodoc:
    extend FFI::Library

    # Define the library that we will be pulling functions from. Note that this
    # must align with the build shared library from make/rake.
    libprism_in_build = File.expand_path("../../build/libprism.#{RbConfig::CONFIG["SOEXT"]}", __dir__)
    libprism_in_libdir = "#{RbConfig::CONFIG["libdir"]}/prism/libprism.#{RbConfig::CONFIG["SOEXT"]}"

    if File.exist?(libprism_in_build)
      INCLUDE_DIR = File.expand_path("../../include", __dir__)
      ffi_lib libprism_in_build
    else
      INCLUDE_DIR = "#{RbConfig::CONFIG["libdir"]}/prism/include"
      ffi_lib libprism_in_libdir
    end

    # Convert a native C type declaration into a symbol that FFI understands.
    # For example:
    #
    #     const char * -> :pointer
    #     bool         -> :bool
    #     size_t       -> :size_t
    #     void         -> :void
    #
    def self.resolve_type(type, callbacks)
      type = type.strip

      if !type.end_with?("*")
        type.delete_prefix("const ").to_sym
      else
        type = type.delete_suffix("*").rstrip
        callbacks.include?(type.to_sym) ? type.to_sym : :pointer
      end
    end

    # Read through the given header file and find the declaration of each of the
    # given functions. For each one, define a function with the same name and
    # signature as the C function.
    def self.load_exported_functions_from(header, *functions, callbacks)
      File.foreach("#{INCLUDE_DIR}/#{header}") do |line|
        # We only want to attempt to load exported functions.
        next unless line.start_with?("PRISM_EXPORTED_FUNCTION ")

        # We only want to load the functions that we are interested in.
        next unless functions.any? { |function| line.include?(function) }

        # Strip trailing attributes (PRISM_NODISCARD, PRISM_NONNULL(...), etc.)
        line = line.sub(/\)(\s+PRISM_\w+(?:\([^)]*\))?)+\s*;/, ");")

        # Parse the function declaration.
        unless /^PRISM_EXPORTED_FUNCTION (?<return_type>.+) (?<name>\w+)\((?<arg_types>.+)\);$/ =~ line
          raise "Could not parse #{line}"
        end

        # Delete the function from the list of functions we are looking for to
        # mark it as having been found.
        functions.delete(name)

        # Split up the argument types into an array, ensure we handle the case
        # where there are no arguments (by explicit void).
        arg_types = arg_types.split(",").map(&:strip)
        arg_types = [] if arg_types == %w[void]

        # Resolve the type of the argument by dropping the name of the argument
        # first if it is present.
        arg_types.map! { |type| resolve_type(type.sub(/\w+$/, ""), callbacks) }

        # Attach the function using the FFI library.
        attach_function name, arg_types, resolve_type(return_type, [])
      end

      # If we didn't find all of the functions, raise an error.
      raise "Could not find functions #{functions.inspect}" unless functions.empty?
    end

    callback :pm_source_stream_fgets_t, [:pointer, :int, :pointer], :pointer
    callback :pm_source_stream_feof_t, [:pointer], :int
    pm_source_init_result_values = %i[PM_SOURCE_INIT_SUCCESS PM_SOURCE_INIT_ERROR_GENERIC PM_SOURCE_INIT_ERROR_DIRECTORY PM_SOURCE_INIT_ERROR_NON_REGULAR]
    enum :pm_source_init_result_t, pm_source_init_result_values
    enum :pm_string_query_t, [:PM_STRING_QUERY_ERROR, -1, :PM_STRING_QUERY_FALSE, :PM_STRING_QUERY_TRUE]
    enum :pm_errors_format_type_t, [:PM_ERRORS_FORMAT_PLAIN, 1, :PM_ERRORS_FORMAT_STYLE, :PM_ERRORS_FORMAT_COLOR]

    # Ractor-safe lookup table for pm_source_init_result_t, since FFI's
    # enum_type accesses module instance variables that are not shareable.
    SOURCE_INIT_RESULT = pm_source_init_result_values.freeze

    load_exported_functions_from(
      "prism/version.h",
      "pm_version",
      []
    )

    load_exported_functions_from(
      "prism/serialize.h",
      "pm_serialize_parse",
      "pm_serialize_parse_stream",
      "pm_serialize_parse_comments",
      "pm_serialize_lex",
      "pm_serialize_parse_lex",
      "pm_serialize_parse_success_p",
      "pm_serialize_parse_errors_format",
      []
    )

    load_exported_functions_from(
      "prism/string_query.h",
      "pm_string_query_local",
      "pm_string_query_constant",
      "pm_string_query_method_name",
      []
    )

    load_exported_functions_from(
      "prism/buffer.h",
      "pm_buffer_new",
      "pm_buffer_value",
      "pm_buffer_length",
      "pm_buffer_free",
      []
    )

    load_exported_functions_from(
      "prism/source.h",
      "pm_source_file_new",
      "pm_source_mapped_new",
      "pm_source_stream_new",
      "pm_source_free",
      "pm_source_source",
      "pm_source_length",
      [:pm_source_stream_fgets_t, :pm_source_stream_feof_t]
    )

    # This object represents a pm_buffer_t. We only use it as an opaque pointer,
    # so it doesn't need to know the fields of pm_buffer_t.
    class PrismBuffer # :nodoc:
      attr_reader :pointer

      def initialize(pointer)
        @pointer = pointer
      end

      def value
        LibRubyParser.pm_buffer_value(pointer)
      end

      def length
        LibRubyParser.pm_buffer_length(pointer)
      end

      def read
        value.read_string(length)
      end

      # Initialize a new buffer and yield it to the block. The buffer will be
      # automatically freed when the block returns.
      def self.with
        buffer = LibRubyParser.pm_buffer_new
        raise unless buffer

        begin
          yield new(buffer)
        ensure
          LibRubyParser.pm_buffer_free(buffer)
        end
      end
    end

    # This object represents source code to be parsed. For strings it wraps a
    # pointer directly; for files it uses a pm_source_t under the hood.
    class PrismSource # :nodoc:
      PLATFORM_EXPECTS_UTF8 =
        RbConfig::CONFIG["host_os"].match?(/bccwin|cygwin|djgpp|mingw|mswin|wince|darwin/i)

      attr_reader :pointer, :length

      def initialize(pointer, length, from_string)
        @pointer = pointer
        @length = length
        @from_string = from_string
      end

      def read
        raise "should use the original String instead" if @from_string
        @pointer.read_string(@length)
      end

      # Yields a PrismSource backed by the given string to the block.
      def self.with_string(string)
        raise TypeError unless string.is_a?(String)

        length = string.bytesize
        # + 1 to never get an address of 0, which pm_parser_init() asserts
        FFI::MemoryPointer.new(:char, length + 1, false) do |pointer|
          pointer.write_string(string)
          # since we have the extra byte we might as well \0-terminate
          pointer.put_char(length, 0)
          return yield new(pointer, length, true)
        end
      end

      # Yields a PrismSource to the given block, backed by a pm_source_t.
      def self.with_file(filepath)
        raise TypeError unless filepath.is_a?(String)

        # On Windows and Mac, it's expected that filepaths will be encoded in
        # UTF-8. If they are not, we need to convert them to UTF-8 before
        # passing them into pm_source_mapped_new.
        if PLATFORM_EXPECTS_UTF8 && (encoding = filepath.encoding) != Encoding::ASCII_8BIT && encoding != Encoding::UTF_8
          filepath = filepath.encode(Encoding::UTF_8)
        end

        FFI::MemoryPointer.new(:int) do |result_ptr|
          pm_source = LibRubyParser.pm_source_mapped_new(filepath, 0, result_ptr)

          case SOURCE_INIT_RESULT[result_ptr.read_int]
          when :PM_SOURCE_INIT_SUCCESS
            pointer = LibRubyParser.pm_source_source(pm_source)
            length = LibRubyParser.pm_source_length(pm_source)
            return yield new(pointer, length, false)
          when :PM_SOURCE_INIT_ERROR_GENERIC
            raise SystemCallError.new(filepath, FFI.errno)
          when :PM_SOURCE_INIT_ERROR_DIRECTORY
            raise Errno::EISDIR.new(filepath)
          when :PM_SOURCE_INIT_ERROR_NON_REGULAR
            # Fall back to reading the file through Ruby IO for non-regular
            # files (pipes, character devices, etc.)
            return with_string(File.read(filepath)) { |string| yield string }
          else
            raise "Unknown error initializing pm_source_t: #{result_ptr.read_int}"
          end
        ensure
          LibRubyParser.pm_source_free(pm_source) if pm_source && !pm_source.null?
        end
      end
    end
  end

  # Mark the LibRubyParser module as private as it should only be called through
  # the prism module.
  private_constant :LibRubyParser

  # The version constant is set by reading the result of calling pm_version.
  VERSION = LibRubyParser.pm_version.read_string.freeze

  class << self
    # Mirror the Prism.dump API by using the serialization API.
    def dump(source, **options)
      LibRubyParser::PrismSource.with_string(source) { |string| dump_common(string, options) }
    end

    # Mirror the Prism.dump_file API by using the serialization API.
    def dump_file(filepath, **options)
      options[:filepath] = filepath
      LibRubyParser::PrismSource.with_file(filepath) { |string| dump_common(string, options) }
    end

    # Mirror the Prism.lex API by using the serialization API.
    def lex(code, **options)
      LibRubyParser::PrismSource.with_string(code) { |string| lex_common(string, code, options) }
    end

    # Mirror the Prism.lex_file API by using the serialization API.
    def lex_file(filepath, **options)
      options[:filepath] = filepath
      LibRubyParser::PrismSource.with_file(filepath) { |string| lex_common(string, string.read, options) }
    end

    # Mirror the Prism.parse API by using the serialization API.
    def parse(code, **options)
      LibRubyParser::PrismSource.with_string(code) { |string| parse_common(string, code, options) }
    end

    # Mirror the Prism.parse_file API by using the serialization API. This uses
    # native strings instead of Ruby strings because it allows us to use mmap
    # when it is available.
    def parse_file(filepath, **options)
      options[:filepath] = filepath
      LibRubyParser::PrismSource.with_file(filepath) { |string| parse_common(string, string.read, options) }
    end

    # Mirror the Prism.parse_stream API by using the serialization API.
    def parse_stream(stream, **options)
      format_type = raise_error_format_type(options)

      LibRubyParser::PrismBuffer.with do |buffer|
        # The largest number of bytes a single character can occupy in any
        # encoding Ruby supports. IO#gets(limit) may return up to
        # (max_enc_len - 1) bytes more than requested to avoid splitting a
        # multi-byte character, so we reserve that much headroom (plus the NUL
        # terminator) to guarantee the result fits in the caller's buffer. This
        # mirrors MAX_ENC_LEN in ext/prism/extension.c.
        max_enc_len = 6

        source = +""
        callback = -> (string, size, _) {
          raise "Expected size to be > #{max_enc_len}, got: #{size}" if size <= max_enc_len

          line = String.try_convert(stream.gets(size - max_enc_len))
          if !line.nil?
            # A misbehaving `gets` may ignore the limit; never write past the
            # buffer (one byte is reserved for the NUL terminator).
            line = line.byteslice(0, size - 1) if line.bytesize > size - 1
            source << line
            string.write_string("#{line}\x00", line.bytesize + 1)
          end
        }

        eof_callback = -> (_) { stream.eof?  }

        pm_source = LibRubyParser.pm_source_stream_new(nil, callback, eof_callback)
        begin
          LibRubyParser.pm_serialize_parse_stream(buffer.pointer, pm_source, dump_options(options))
          result = Prism.load(source, buffer.read, options.fetch(:freeze, false))

          if format_type && result.failure?
            LibRubyParser::PrismSource.with_string(source) do |string|
              raise_error(string, options, format_type)
            end
          end

          result
        ensure
          LibRubyParser.pm_source_free(pm_source) if pm_source && !pm_source.null?
        end
      end
    end

    # Mirror the Prism.parse_comments API by using the serialization API.
    def parse_comments(code, **options)
      LibRubyParser::PrismSource.with_string(code) { |string| parse_comments_common(string, code, options) }
    end

    # Mirror the Prism.parse_file_comments API by using the serialization
    # API. This uses native strings instead of Ruby strings because it allows us
    # to use mmap when it is available.
    def parse_file_comments(filepath, **options)
      options[:filepath] = filepath
      LibRubyParser::PrismSource.with_file(filepath) { |string| parse_comments_common(string, string.read, options) }
    end

    # Mirror the Prism.parse_lex API by using the serialization API.
    def parse_lex(code, **options)
      LibRubyParser::PrismSource.with_string(code) { |string| parse_lex_common(string, code, options) }
    end

    # Mirror the Prism.parse_lex_file API by using the serialization API.
    def parse_lex_file(filepath, **options)
      options[:filepath] = filepath
      LibRubyParser::PrismSource.with_file(filepath) { |string| parse_lex_common(string, string.read, options) }
    end

    # Mirror the Prism.parse_success? API by using the serialization API.
    def parse_success?(code, **options)
      LibRubyParser::PrismSource.with_string(code) { |string| parse_file_success_common(string, options) }
    end

    # Mirror the Prism.parse_failure? API by using the serialization API.
    def parse_failure?(code, **options)
      !parse_success?(code, **options)
    end

    # Mirror the Prism.parse_file_success? API by using the serialization API.
    def parse_file_success?(filepath, **options)
      options[:filepath] = filepath
      LibRubyParser::PrismSource.with_file(filepath) { |string| parse_file_success_common(string, options) }
    end

    # Mirror the Prism.parse_file_failure? API by using the serialization API.
    def parse_file_failure?(filepath, **options)
      !parse_file_success?(filepath, **options)
    end

    # Mirror the Prism.profile API by using the serialization API.
    def profile(source, **options)
      LibRubyParser::PrismSource.with_string(source) do |string|
        if (format_type = raise_error_format_type(options))
          raise_error(string, options, format_type)
        end

        LibRubyParser::PrismBuffer.with do |buffer|
          LibRubyParser.pm_serialize_parse(buffer.pointer, string.pointer, string.length, dump_options(options))
          nil
        end
      end
    end

    # Mirror the Prism.profile_file API by using the serialization API.
    def profile_file(filepath, **options)
      LibRubyParser::PrismSource.with_file(filepath) do |string|
        options[:filepath] = filepath

        if (format_type = raise_error_format_type(options))
          raise_error(string, options, format_type)
        end

        LibRubyParser::PrismBuffer.with do |buffer|
          LibRubyParser.pm_serialize_parse(buffer.pointer, string.pointer, string.length, dump_options(options))
          nil
        end
      end
    end

    private

    def dump_common(string, options) # :nodoc:
      if (format_type = raise_error_format_type(options))
        raise_error(string, options, format_type)
      end

      LibRubyParser::PrismBuffer.with do |buffer|
        LibRubyParser.pm_serialize_parse(buffer.pointer, string.pointer, string.length, dump_options(options))

        dumped = buffer.read
        dumped.freeze if options.fetch(:freeze, false)

        dumped
      end
    end

    def lex_common(string, code, options) # :nodoc:
      format_type = raise_error_format_type(options)

      LibRubyParser::PrismBuffer.with do |buffer|
        LibRubyParser.pm_serialize_lex(buffer.pointer, string.pointer, string.length, dump_options(options))
        result = Serialize.load_lex(code, buffer.read, options.fetch(:freeze, false))

        raise_error(string, options, format_type) if format_type && result.failure?
        result
      end
    end

    def parse_common(string, code, options) # :nodoc:
      format_type = raise_error_format_type(options)
      serialized = dump_common(string, options)
      result = Serialize.load_parse(code, serialized, options.fetch(:freeze, false))

      raise_error(string, options, format_type) if format_type && result.failure?
      result
    end

    def parse_comments_common(string, code, options) # :nodoc:
      if (format_type = raise_error_format_type(options))
        raise_error(string, options, format_type)
      end

      LibRubyParser::PrismBuffer.with do |buffer|
        LibRubyParser.pm_serialize_parse_comments(buffer.pointer, string.pointer, string.length, dump_options(options))
        Serialize.load_parse_comments(code, buffer.read, options.fetch(:freeze, false))
      end
    end

    def parse_lex_common(string, code, options) # :nodoc:
      format_type = raise_error_format_type(options)

      LibRubyParser::PrismBuffer.with do |buffer|
        LibRubyParser.pm_serialize_parse_lex(buffer.pointer, string.pointer, string.length, dump_options(options))
        result = Serialize.load_parse_lex(code, buffer.read, options.fetch(:freeze, false))

        raise_error(string, options, format_type) if format_type && result.failure?
        result
      end
    end

    def parse_file_success_common(string, options) # :nodoc:
      format_type = raise_error_format_type(options)
      success = LibRubyParser.pm_serialize_parse_success_p(string.pointer, string.length, dump_options(options))

      raise_error(string, options, format_type) if format_type && !success
      success
    end

    # Extract the raise_error option from the given options hash and convert
    # it into the format type that should be used when formatting errors, or
    # nil if raising is disabled.
    def raise_error_format_type(options) # :nodoc:
      case (value = options.delete(:raise_error))
      when nil, false
        nil
      when true
        # When given true, mirror the behavior of CRuby itself: color when
        # $stderr is a terminal (unless NO_COLOR is set), bold styling when
        # NO_COLOR is set, plain otherwise. This policy is duplicated in
        # ext/prism/extension.c (build_options_i) and the two must stay in
        # sync.
        if $stderr.respond_to?(:tty?) && $stderr.tty?
          no_color = ENV["NO_COLOR"]
          (no_color.nil? || no_color.empty?) ? :PM_ERRORS_FORMAT_COLOR : :PM_ERRORS_FORMAT_STYLE
        else
          :PM_ERRORS_FORMAT_PLAIN
        end
      when :plain
        :PM_ERRORS_FORMAT_PLAIN
      when :style
        :PM_ERRORS_FORMAT_STYLE
      when :color
        :PM_ERRORS_FORMAT_COLOR
      when Symbol
        raise ArgumentError, "invalid raise_error value: #{value}"
      else
        raise TypeError, "wrong argument type #{value.class} (expected Symbol)"
      end
    end

    # Parse the given source and format any errors that are encountered into
    # an appropriate exception, then raise it. If the source parses without
    # any errors, then return nil.
    def raise_error(string, options, format_type) # :nodoc:
      LibRubyParser::PrismBuffer.with do |buffer|
        level = LibRubyParser.pm_serialize_parse_errors_format(buffer.pointer, string.pointer, string.length, dump_options(options), format_type)
        return if level == -1

        encoding_name, _, message = buffer.read.partition("\0")

        case level
        when 0 # syntax
          error = SyntaxError.new(message.force_encoding(encoding_name))
          error.instance_variable_set(:@path, options.fetch(:filepath, ""))
          raise error
        when 1 # argument
          raise ArgumentError, message.force_encoding(encoding_name)
        when 2 # load
          error = LoadError.new(message.force_encoding(Encoding.find("locale")))
          error.instance_variable_set(:@path, nil)
          raise error
        else
          raise "Unknown error level: #{level}"
        end
      end
    end

    # Return the value that should be dumped for the command_line option.
    def dump_options_command_line(options)
      command_line = options.fetch(:command_line, "")
      raise ArgumentError, "command_line must be a string" unless command_line.is_a?(String)

      command_line.each_char.inject(0) do |value, char|
        case char
        when "a" then value | 0b000001
        when "e" then value | 0b000010
        when "l" then value | 0b000100
        when "n" then value | 0b001000
        when "p" then value | 0b010000
        when "x" then value | 0b100000
        else raise ArgumentError, "invalid command_line option: #{char}"
        end
      end
    end

    # Return the value that should be dumped for the version option.
    def dump_options_version(version)
      case version
      when "current"
        version_string_to_number(RUBY_VERSION) || raise(CurrentVersionError, RUBY_VERSION)
      when "latest", nil
        0 # Handled in pm_parser_init
      when "nearest"
        dump = version_string_to_number(RUBY_VERSION)
        return dump if dump
        if RUBY_VERSION < "3.3"
          version_string_to_number("3.3")
        else
          0 # Handled in pm_parser_init
        end
      else
        version_string_to_number(version) || raise(ArgumentError, "invalid version: #{version}")
      end
    end

    # Converts a version string like "4.0.0" or "4.0" into a number.
    # Returns nil if the version is unknown.
    def version_string_to_number(version)
      case version
      when /\A3\.3(\.\d+)?\z/
        1
      when /\A3\.4(\.\d+)?\z/
        2
      when /\A3\.5(\.\d+)?\z/, /\A4\.0(\.\d+)?\z/
        3
      when /\A4\.1(\.\d+)?\z/
        4
      end
    end

    # The set of options that are understood by the parsing APIs. Note that
    # raise_error is not listed here because it is deleted from the options
    # hash by raise_error_format_type before the options are dumped.
    DUMP_OPTIONS_KEYS = [:command_line, :encoding, :filepath, :freeze, :frozen_string_literal, :line, :main_script, :partial_script, :scopes, :version].freeze
    private_constant :DUMP_OPTIONS_KEYS

    # Convert the given options into a serialized options string.
    def dump_options(options)
      unknown_keys = options.keys - DUMP_OPTIONS_KEYS
      raise ArgumentError, "unknown keyword: #{unknown_keys.first}" unless unknown_keys.empty?

      template = +""
      values = []

      template << "L"
      if (filepath = options[:filepath])
        values.push(filepath.bytesize, filepath.b)
        template << "A*"
      else
        values << 0
      end

      template << "l"
      values << options.fetch(:line, 1)

      template << "L"
      if (encoding = options[:encoding])
        name = encoding.is_a?(Encoding) ? encoding.name : encoding
        values.push(name.bytesize, name.b)
        template << "A*"
      else
        values << 0
      end

      template << "C"
      values << (options.fetch(:frozen_string_literal, false) ? 1 : 0)

      template << "C"
      values << dump_options_command_line(options)

      template << "C"
      values << dump_options_version(options[:version])

      template << "C"
      values << (options[:encoding] == false ? 1 : 0)

      template << "C"
      values << (options.fetch(:main_script, false) ? 1 : 0)

      template << "C"
      values << (options.fetch(:partial_script, false) ? 1 : 0)

      template << "C"
      values << (options.fetch(:freeze, false) ? 1 : 0)

      template << "L"
      if (scopes = options[:scopes])
        values << scopes.length

        scopes.each do |scope|
          locals = nil
          forwarding = 0

          case scope
          when Array
            locals = scope
          when Scope
            locals = scope.locals

            scope.forwarding.each do |forward|
              case forward
              when :*     then forwarding |= 0x1
              when :**    then forwarding |= 0x2
              when :&     then forwarding |= 0x4
              when :"..." then forwarding |= 0x8
              else raise ArgumentError, "invalid forwarding value: #{forward}"
              end
            end
          else
            raise TypeError, "wrong argument type #{scope.class.inspect} (expected Array or Prism::Scope)"
          end

          template << "L"
          values << locals.length

          template << "C"
          values << forwarding

          locals.each do |local|
            name = local.name
            template << "L"
            values << name.bytesize

            template << "A*"
            values << name.b
          end
        end
      else
        values << 0
      end

      values.pack(template)
    end
  end

  # Here we are going to patch StringQuery to put in the class-level methods so
  # that it can maintain a consistent interface
  class StringQuery # :nodoc:
    class << self
      # Mirrors the C extension's StringQuery::local? method.
      def local?(string)
        query(LibRubyParser.pm_string_query_local(string, string.bytesize, string.encoding.name))
      end

      # Mirrors the C extension's StringQuery::constant? method.
      def constant?(string)
        query(LibRubyParser.pm_string_query_constant(string, string.bytesize, string.encoding.name))
      end

      # Mirrors the C extension's StringQuery::method_name? method.
      def method_name?(string)
        query(LibRubyParser.pm_string_query_method_name(string, string.bytesize, string.encoding.name))
      end

      private

      # Parse the enum result and return an appropriate boolean.
      def query(result)
        case result
        when :PM_STRING_QUERY_ERROR
          raise ArgumentError, "Invalid or non ascii-compatible encoding"
        when :PM_STRING_QUERY_FALSE
          false
        when :PM_STRING_QUERY_TRUE
          true
        end
      end
    end
  end
end
