# frozen_string_literal: true

require "rubygems/ext"
require "shellwords"
require_relative "cargo_builder"

# Root module
module RbSys
  # Helper class for creating Rust Makefiles
  module Mkmf
    # Helper for building Rust extensions by creating a Ruby compatible makefile
    # for Rust. By using this class, your rust extension will be 100% compatible
    # with the rake-compiler gem, which allows for easy cross compilation.
    #
    # @example Basic
    #   require 'mkmf'
    # . require 'rb_sys/mkmf'
    #
    # . create_rust_makefile("my_extension") #=> Generate a Makefile in the current directory
    #
    # @example Configure a custom build profile
    #   require 'mkmf'
    # . require 'rb_sys/mkmf'
    #
    # . create_rust_makefile("my_extension") do |r|
    # .   # All of these are optional
    # .   r.env = { 'FOO' => 'bar' }
    # .   r.profile = ENV.fetch('RB_SYS_CARGO_PROFILE', :dev).to_sym
    # .   r.features = %w[some_cargo_feature]
    # . end
    def create_rust_makefile(target, &blk)
      if target.include?("/")
        target_prefix, target = File.split(target)
        target_prefix[0, 0] = "/"
      else
        target_prefix = ""
      end

      spec = Struct.new(:name, :metadata).new(target, {})
      builder = CargoBuilder.new(spec)

      yield builder if blk

      srcprefix = "$(srcdir)/#{builder.ext_dir}".chomp("/")
      RbConfig.expand(srcdir = srcprefix.dup)

      full_cargo_command = cargo_command(srcdir, builder)

      # rubocop:disable Style/GlobalVars
      make_install = +<<~MAKE
        RB_SYS_CARGO_PROFILE ?= #{builder.profile}
        RB_SYS_CARGO_FEATURES ?= #{builder.features.join(",")}
        CARGO ?= cargo

        ifeq ($(RB_SYS_CARGO_PROFILE),dev)
          RB_SYS_TARGET_DIR ?= debug
        else
          RB_SYS_TARGET_DIR ?= $(RB_SYS_CARGO_PROFILE)
        endif

        target_prefix = #{target_prefix}
        TARGET_NAME = #{target[/\A\w+/]}
        TARGET_ENTRY = #{RbConfig::CONFIG["EXPORT_PREFIX"]}Init_$(TARGET_NAME)
        CLEANLIBS = $(RUSTLIB) $(DLLIB) $(DEFFILE)
        DISTCLEANDIRS = target/
        RUBYARCHDIR   = $(sitearchdir)$(target_prefix)
        RUSTLIB = #{dllib_path(builder)}
        TARGET = #{target}
        DLLIB = $(TARGET).#{RbConfig::CONFIG["DLEXT"]}
        TARGET_DIR = #{Dir.pwd}/target/$(RB_SYS_TARGET_DIR)
        DEFFILE = $(TARGET_DIR)/$(TARGET)-$(arch).def
        #{base_makefile(srcdir)}
        #{env_vars(builder)}

        FORCE: ;

        $(TARGET_DIR):
        \t$(ECHO) creating target directory \\($(@)\\)
        \t$(Q) $(MAKEDIRS) $(TARGET_DIR)

        $(DEFFILE): $(TARGET_DIR)
        \t$(ECHO) generating $(@)
        \t$(Q) ($(COPY) $(srcdir)/$(TARGET).def $@ 2> /dev/null) || (echo EXPORTS && echo $(TARGET_ENTRY)) > $@

        $(DLLIB): $(DEFFILE) FORCE
        \t$(ECHO) generating $(@) \\("$(RB_SYS_CARGO_PROFILE)"\\)
        \t$(Q) #{full_cargo_command}
        \t$(Q) $(COPY) "$(RUSTLIB)" $@

        install: $(DLLIB) Makefile
        \t$(ECHO) installing $(DLLIB)
        \t$(Q) $(MAKEDIRS) $(RUBYARCHDIR)
        \t$(Q) $(INSTALL_PROG) $(DLLIB) $(RUBYARCHDIR)

        all: #{$extout ? "install" : "$(DLLIB)"}
      MAKE

      gsub_cargo_command!(make_install, builder: builder)

      File.write("Makefile", make_install)
    end
    # rubocop:enable Style/GlobalVars

    private

    def base_makefile(cargo_dir)
      base_makefile = dummy_makefile(__dir__).join("\n")
      base_makefile.gsub!("all install static install-so install-rb", "all static install-so install-rb")
      base_makefile.gsub!("clean-so::", "clean-so:\n\t-$(Q)$(RM) $(DLLIB)\n")
      base_makefile.gsub!(/^srcdir = .*$/, "srcdir = #{cargo_dir}")
      base_makefile
    end

    def cargo_command(cargo_dir, builder)
      builder.ext_dir = cargo_dir
      dest_path = File.join(Dir.pwd, "target")
      args = ARGV.dup
      args.shift if args.first == "--"
      cargo_cmd = builder.cargo_command(dest_path, args)
      Shellwords.join(cargo_cmd).gsub("\\=", "=").gsub(/\Acargo/, "$(CARGO)")
    end

    def env_vars(builder)
      lines = builder.build_env.map { |k, v| env_line(k, v) }
      lines << env_line("CC", env_or_makefile_config("CC"))
      lines << env_line("AR", env_or_makefile_config("AR")) unless env_or_makefile_config("AR") == "libtool -static"
      lines.compact.join("\n")
    end

    def env_line(k, v)
      return unless v
      %($(DLLIB): export #{k} = #{v.gsub("\n", '\n')})
    end

    def env_or_makefile_config(key)
      ENV[key] || RbConfig::MAKEFILE_CONFIG[key]
    end

    def dllib_path(builder)
      builder.cargo_dylib_path(File.join(Dir.pwd, "target"))
    end

    def gsub_cargo_command!(cargo_command, builder:)
      cargo_command.gsub!("--profile #{builder.profile}", "--profile $(RB_SYS_CARGO_PROFILE)")
      cargo_command.gsub!(%r{--features \S+}, "--features $(RB_SYS_CARGO_FEATURES)")
      cargo_command.gsub!(%r{/target/\w+/}, "/target/$(RB_SYS_TARGET_DIR)/")
      cargo_command
    end
  end
end

include RbSys::Mkmf # rubocop:disable Style/MixinUsage