# frozen_string_literal: true

module RBS
  class EnvironmentLoader
    class UnknownLibraryError < StandardError
      attr_reader :library

      def initialize(lib:)
        @library = lib

        super("Cannot find type definitions for library: #{lib.name} (#{lib.version || "[nil]"})")
      end
    end

    include FileFinder

    class Library < Struct.new(:name, :version, keyword_init: true)
    end

    attr_reader :core_root
    attr_reader :repository

    attr_reader :libs
    attr_reader :dirs

    DEFAULT_CORE_ROOT = Pathname(_ = __dir__) + "../../core"

    def self.gem_sig_path(name, version)
      requirements = [] #: Array[String]
      requirements << version if version
      spec = Gem::Specification.find_by_name(name, *requirements)
      path = Pathname(spec.gem_dir) + "sig"
      if path.directory?
        [spec, path]
      end
    rescue Gem::MissingSpecError
      nil
    end

    def initialize(core_root: DEFAULT_CORE_ROOT, repository: Repository.new)
      @core_root = core_root
      @repository = repository

      @libs = Set.new
      @dirs = []
    end

    def add(path: nil, library: nil, version: nil, resolve_dependencies: true)
      case
      when path
        dirs << path
      when library
        case library
        when 'pathname'
          RBS.logger.warn "`#{library}` has been moved to core library, so it is always loaded. Remove explicit loading `#{library}`"
          return
        end

        if libs.add?(Library.new(name: library, version: version)) && resolve_dependencies
          resolve_dependencies(library: library, version: version)
        end
      end
    end

    def resolve_dependencies(library:, version:)
      [Collection::Sources::Rubygems.instance, Collection::Sources::Stdlib.instance].each do |source|
        next unless source.has?(library, version)

        unless version
          version = source.versions(library).last or raise
        end

        source.dependencies_of(library, version)&.each do |dep|
          add(library: dep['name'], version: nil)
        end
        return
      end
    end

    def add_collection(lockfile)
      lockfile.check_rbs_availability!

      repository.add(lockfile.fullpath)

      lockfile.gems.each_value do |gem|
        name = gem[:name]
        locked_version = gem[:version]

        if (source = gem[:source]).is_a?(Collection::Sources::Rubygems)
          # allow loading different version of a gem

          unless source.has?(name, locked_version)
            if (spec, _ = self.class.gem_sig_path(name, nil))
              RBS.logger.warn { "Loading type definition from gem `#{name}-#{spec.version}` because locked version `#{locked_version}` is unavailable. Try `rbs collection update` to fix the (potential) issue." }
              locked_version = spec.version.to_s
            end
          end
        end

        add(library: gem[:name], version: locked_version, resolve_dependencies: false)
      end
    end

    def has_library?(library:, version:)
      if self.class.gem_sig_path(library, version) || repository.lookup(library, version)
        true
      else
        false
      end
    end

    def load(env:)
      # @type var loaded: Array[[AST::Declarations::t, Pathname, source]]
      loaded = []

      # For migrating stringio to stdlib
      if @core_root && libs.none? { |lib| lib.name == 'stringio' }
        add(library: 'stringio', version: nil)
      end

      each_signature do |source, path, buffer, decls, dirs|
        decls.each do |decl|
          loaded << [decl, path, source]
        end
        env.add_signature(buffer: buffer, directives: dirs, decls: decls)
      end

      loaded
    end

    def each_dir
      if root = core_root
        yield :core, root
      end

      libs.each do |lib|
        unless has_library?(version: lib.version, library: lib.name)
          raise UnknownLibraryError.new(lib: lib)
        end

        case
        when from_gem = self.class.gem_sig_path(lib.name, lib.version)
          yield lib, from_gem[1]
        when from_repo = repository.lookup(lib.name, lib.version)
          yield lib, from_repo
        end
      end

      dirs.each do |dir|
        yield dir, dir
      end
    end

    def each_signature
      files = Set[]

      each_dir do |source, dir|
        skip_hidden = !source.is_a?(Pathname)

        FileFinder.each_file(dir, skip_hidden: skip_hidden) do |path|
          next if files.include?(path)

          files << path
          buffer = Buffer.new(name: path.to_s, content: path.read(encoding: "UTF-8"))

          _, dirs, decls = Parser.parse_signature(buffer)

          yield source, path, buffer, decls, dirs
        end
      end
    end
  end
end
