require "rubygems/ext"
require "rubygems/ext/builder"
require_relative "cargo_builder/link_flag_converter"

module RbSys
  # A class to build a Ruby gem Cargo. Extracted from `rubygems` gem, with some modifications.
  # @api private
  class CargoBuilder < Gem::Ext::Builder
    WELL_KNOWN_WRAPPERS = %w[sccache cachepot].freeze

    attr_accessor :spec, :runner, :env, :features, :target, :extra_rustc_args, :dry_run, :ext_dir, :extra_rustflags,
      :extra_cargo_args
    attr_writer :profile

    def initialize(spec)
      require "rubygems/command"
      require_relative "cargo_builder/link_flag_converter"

      @spec = spec
      @runner = self.class.method(:run)
      @profile = ENV.fetch("RB_SYS_CARGO_PROFILE", :release).to_sym
      @env = {}
      @features = []
      @target = ENV["CARGO_BUILD_TARGET"] || ENV["RUST_TARGET"]
      @extra_rustc_args = []
      @extra_cargo_args = []
      @dry_run = true
      @ext_dir = ""
      @extra_rustflags = []
    end

    def profile
      return :release if rubygems_invoked?

      @profile
    end

    def build(_extension, dest_path, results, args = [], lib_dir = nil, cargo_dir = Dir.pwd)
      require "fileutils"
      require "shellwords"

      build_crate(dest_path, results, args, cargo_dir)
      validate_cargo_build!(dest_path)
      rename_cdylib_for_ruby_compatibility(dest_path)
      finalize_directory(dest_path, lib_dir, cargo_dir)
      results
    end

    def build_crate(dest_path, results, args, cargo_dir)
      env = build_env
      cmd = cargo_command(dest_path, args)
      runner.call cmd, results, "cargo", cargo_dir, env

      results
    end

    def build_env
      build_env = rb_config_env
      build_env["RUBY_STATIC"] = "true" if ruby_static? && ENV.key?("RUBY_STATIC")
      build_env.merge(env)
    end

    def manifest_dir
      ext_dir
    end

    def cargo_command(dest_path, args = [])
      cmd = []
      cmd += ["cargo", "rustc"]
      cmd += ["--target", target] if target
      cmd += ["--target-dir", dest_path]
      cmd += ["--features", features.join(",")] unless features.empty?
      cmd += ["--lib"]
      cmd += ["--profile", profile.to_s]
      cmd += Gem::Command.build_args
      cmd += args
      cmd += ["--"]
      cmd += [*rustc_args(dest_path)]
      cmd += extra_rustc_args
      cmd
    end

    def cargo_dylib_path(dest_path)
      prefix = so_ext == "dll" ? "" : "lib"
      path_parts = [dest_path]
      path_parts << target if target
      path_parts += [profile_target_directory, "#{prefix}#{cargo_crate_name}.#{so_ext}"]
      File.join(*path_parts)
    end

    # We have to basically reimplement RbConfig::CONFIG['SOEXT'] here to support
    # Ruby < 2.5
    #
    # @see https://github.com/ruby/ruby/blob/c87c027f18c005460746a74c07cd80ee355b16e4/configure.ac#L3185
    def so_ext
      return RbConfig::CONFIG["SOEXT"] if RbConfig::CONFIG.key?("SOEXT")

      if win_target?
        "dll"
      elsif darwin_target?
        "dylib"
      else
        "so"
      end
    end

    private

    def rb_config_env
      result = {}
      RbConfig::CONFIG.each { |k, v| result["RBCONFIG_#{k}"] = v }
      result
    end

    def rustc_args(dest_dir)
      [
        *linker_args,
        *mkmf_libpath,
        *rustc_dynamic_linker_flags(dest_dir),
        *rustc_lib_flags(dest_dir),
        *platform_specific_rustc_args(dest_dir)
      ]
    end

    def platform_specific_rustc_args(dest_dir, flags = [])
      if mingw_target?
        # On mingw platforms, mkmf adds libruby to the linker flags
        flags += libruby_args(dest_dir)

        # Make sure ALSR is used on mingw
        # see https://github.com/rust-lang/rust/pull/75406/files
        flags += ["-C", "link-arg=-Wl,--dynamicbase"]
        flags += ["-C", "link-arg=-Wl,--disable-auto-image-base"]

        # If the gem is installed on a host with build tools installed, but is
        # run on one that isn't the missing libraries will cause the extension
        # to fail on start.
        flags += ["-C", "link-arg=-static-libgcc"]
      elsif darwin_target?
        # See https://github.com/oxidize-rb/rb-sys/issues/88
        dl_flag = "-Wl,-undefined,dynamic_lookup"
        flags += ["-C", "link-arg=#{dl_flag}"] unless makefile_config("DLDFLAGS")&.include?(dl_flag)
      end

      flags
    end

    # We want to use the same linker that Ruby uses, so that the linker flags from
    # mkmf work properly.
    def linker_args
      cc_flag = Shellwords.split(makefile_config("CC"))
      linker = cc_flag.shift

      if WELL_KNOWN_WRAPPERS.any? { |w| linker.include?(w) }
        linker = cc_flag.shift
      end

      link_args = cc_flag.flat_map { |a| ["-C", "link-arg=#{a}"] }

      return mswin_link_args if linker == "cl"

      ["-C", "linker=#{linker}", *link_args]
    end

    def mswin_link_args
      args = []
      args += ["-l", makefile_config("LIBRUBYARG_SHARED").chomp(".lib")]
      args += split_flags("LIBS").flat_map { |lib| ["-l", lib.chomp(".lib")] }
      args += split_flags("LOCAL_LIBS").flat_map { |lib| ["-l", lib.chomp(".lib")] }
      args
    end

    def libruby_args(dest_dir)
      libs = makefile_config(ruby_static? ? "LIBRUBYARG_STATIC" : "LIBRUBYARG_SHARED")
      raw_libs = Shellwords.split(libs)
      raw_libs.flat_map { |l| ldflag_to_link_modifier(l) }
    end

    def ruby_static?
      return true if %w[1 true].include?(ENV["RUBY_STATIC"])

      makefile_config("ENABLE_SHARED") == "no"
    end

    # Ruby expects the dylib to follow a file name convention for loading
    def rename_cdylib_for_ruby_compatibility(dest_path)
      new_path = final_extension_path(dest_path)
      FileUtils.cp(cargo_dylib_path(dest_path), new_path)
      new_path
    end

    def validate_cargo_build!(dir)
      dylib_path = cargo_dylib_path(dir)

      raise DylibNotFoundError, dir unless File.exist?(dylib_path)

      dylib_path
    end

    def final_extension_path(dest_path)
      dylib_path = cargo_dylib_path(dest_path)
      dlext_name = "#{spec.name}.#{makefile_config("DLEXT")}"
      dylib_path.gsub(File.basename(dylib_path), dlext_name)
    end

    def cargo_crate_name
      spec.metadata.fetch("cargo_crate_name", spec.name).tr("-", "_")
    end

    def rustc_dynamic_linker_flags(dest_dir)
      split_flags("DLDFLAGS")
        .map { |arg| maybe_resolve_ldflag_variable(arg, dest_dir) }
        .compact
        .flat_map { |arg| ldflag_to_link_modifier(arg) }
    end

    def rustc_lib_flags(dest_dir)
      split_flags("LIBS").flat_map { |arg| ldflag_to_link_modifier(arg) }
    end

    def split_flags(var)
      Shellwords.split(RbConfig::CONFIG.fetch(var, ""))
    end

    def ldflag_to_link_modifier(arg)
      LinkFlagConverter.convert(arg)
    end

    def msvc_target?
      makefile_config("target_os").include?("msvc")
    end

    def darwin_target?
      makefile_config("target_os").include?("darwin")
    end

    def mingw_target?
      makefile_config("target_os").include?("mingw")
    end

    def win_target?
      target_platform = RbConfig::CONFIG["target_os"]
      !!Gem::WIN_PATTERNS.find { |r| target_platform =~ r }
    end

    # Interpolate substition vars in the arg
    def maybe_resolve_ldflag_variable(input_arg, dest_dir)
      var_matches = input_arg.match(/\$\((\w+)\)/)

      return input_arg unless var_matches

      var_name = var_matches[1]

      return input_arg if var_name.nil? || var_name.chomp.empty?

      case var_name
      when "DEFFILE"
        # DEFFILE already generated by cargo
      else
        RbConfig::CONFIG[var_name]
      end
    end

    # Corresponds to $(LIBPATH) in mkmf
    def mkmf_libpath
      ["-L", "native=#{makefile_config("libdir")}"]
    end

    def makefile_config(var_name)
      val = RbConfig::MAKEFILE_CONFIG[var_name]

      return unless val

      RbConfig.expand(val.dup)
    end

    # Copied from ExtConfBuilder
    def finalize_directory(dest_path, lib_dir, extension_dir)
      require "fileutils"
      require "tempfile"

      ext_path = final_extension_path(dest_path)

      begin
        tmp_dest = Dir.mktmpdir(".gem.", extension_dir)

        # Some versions of `mktmpdir` return absolute paths, which will break make
        # if the paths contain spaces. However, on Ruby 1.9.x on Windows, relative
        # paths cause all C extension builds to fail.
        #
        # As such, we convert to a relative path unless we are using Ruby 1.9.x on
        # Windows. This means that when using Ruby 1.9.x on Windows, paths with
        # spaces do not work.
        #
        # Details: https://github.com/rubygems/rubygems/issues/977#issuecomment-171544940
        tmp_dest_relative = get_relative_path(tmp_dest.clone, extension_dir)

        if tmp_dest_relative
          full_tmp_dest = File.join(extension_dir, tmp_dest_relative)

          # TODO: remove in RubyGems 3
          if Gem.install_extension_in_lib && lib_dir
            FileUtils.mkdir_p lib_dir
            FileUtils.cp_r ext_path, lib_dir, remove_destination: true
          end

          FileUtils::Entry_.new(full_tmp_dest).traverse do |ent|
            destent = ent.class.new(dest_path, ent.rel)
            destent.exist? || FileUtils.mv(ent.path, destent.path)
          end
        end
      ensure
        FileUtils.rm_rf tmp_dest if tmp_dest
      end
    end

    def get_relative_path(path, base)
      path[0..base.length - 1] = "." if path.start_with?(base)
      path
    end

    def profile_target_directory
      case profile.to_sym
      when :release then "release"
      when :dev then "debug"
      else raise "unknown target directory for profile: #{profile}"
      end
    end

    def rubygems_invoked?
      ENV.key?("SOURCE_DATE_EPOCH")
    end

    # Error raised when no cdylib artifact was created
    class DylibNotFoundError < StandardError
      def initialize(dir)
        files = Dir.glob(File.join(dir, "**", "*")).map { |f| "- #{f}" }.join "\n"

        super <<~MSG
          Dynamic library not found for Rust extension (in #{dir})

          Make sure you set "crate-type" in Cargo.toml to "cdylib"

          Found files:
          #{files}
        MSG
      end
    end
  end
end