require_relative "upstream"

module Litestream
  module Commands
    DEFAULT_DIR = File.expand_path(File.join(__dir__, "..", "..", "exe"))
    GEM_NAME = "litestream"

    # raised when the host platform is not supported by upstream litestream's binary releases
    UnsupportedPlatformException = Class.new(StandardError)

    # raised when the litestream executable could not be found where we expected it to be
    ExecutableNotFoundException = Class.new(StandardError)

    # raised when LITESTREAM_INSTALL_DIR does not exist
    DirectoryNotFoundException = Class.new(StandardError)

    # raised when a litestream command requires a database argument but it isn't provided
    DatabaseRequiredException = Class.new(StandardError)

    # raised when litestream fails to restore a database backup
    BackupFailedException = Class.new(StandardError)

    class << self
      def platform
        [:cpu, :os].map { |m| Gem::Platform.local.send(m) }.join("-")
      end

      def executable(exe_path: DEFAULT_DIR)
        litestream_install_dir = ENV["LITESTREAM_INSTALL_DIR"]
        if litestream_install_dir
          if File.directory?(litestream_install_dir)
            warn "NOTE: using LITESTREAM_INSTALL_DIR to find litestream executable: #{litestream_install_dir}"
            exe_path = litestream_install_dir
            exe_file = File.expand_path(File.join(litestream_install_dir, "litestream"))
          else
            raise DirectoryNotFoundException, <<~MESSAGE
              LITESTREAM_INSTALL_DIR is set to #{litestream_install_dir}, but that directory does not exist.
            MESSAGE
          end
        else
          if Litestream::Upstream::NATIVE_PLATFORMS.keys.none? { |p| Gem::Platform.match_gem?(Gem::Platform.new(p), GEM_NAME) }
            raise UnsupportedPlatformException, <<~MESSAGE
              litestream-ruby does not support the #{platform} platform
              Please install litestream following instructions at https://litestream.io/install
            MESSAGE
          end

          exe_file = Dir.glob(File.expand_path(File.join(exe_path, "*", "litestream"))).find do |f|
            Gem::Platform.match_gem?(Gem::Platform.new(File.basename(File.dirname(f))), GEM_NAME)
          end
        end

        if exe_file.nil? || !File.exist?(exe_file)
          raise ExecutableNotFoundException, <<~MESSAGE
            Cannot find the litestream executable for #{platform} in #{exe_path}

            If you're using bundler, please make sure you're on the latest bundler version:

                gem install bundler
                bundle update --bundler

            Then make sure your lock file includes this platform by running:

                bundle lock --add-platform #{platform}
                bundle install

            See `bundle lock --help` output for details.

            If you're still seeing this message after taking those steps, try running
            `bundle config` and ensure `force_ruby_platform` isn't set to `true`. See
            https://github.com/fractaledmind/litestream-ruby#check-bundle_force_ruby_platform
            for more details.
          MESSAGE
        end

        exe_file
      end

      def replicate(async: false, **argv)
        execute("replicate", argv, async: async, hashify: false)
      end

      def restore(database, async: false, **argv)
        raise DatabaseRequiredException, "database argument is required for restore command, e.g. litestream:restore -- --database=path/to/database.sqlite" if database.nil?
        argv.stringify_keys!

        execute("restore", argv, database, async: async, hashify: false)

        argv["-o"] || database
      end

      def verify(database, async: false, **argv)
        raise DatabaseRequiredException, "database argument is required for verify command, e.g. litestream:verify -- --database=path/to/database.sqlite" if database.nil? || !File.exist?(database)
        argv.stringify_keys!

        dir, file = File.split(database)
        ext = File.extname(file)
        base = File.basename(file, ext)
        now = Time.now.utc.strftime("%Y%m%d%H%M%S")
        backup = File.join(dir, "#{base}-#{now}#{ext}")
        args = {
          "-o" => backup
        }.merge(argv)

        backup = restore(database, async: false, **args)

        raise BackupFailedException, "Failed to create backup for validation" unless File.exist?(backup)

        restored_tables_count = `sqlite3 #{backup} "select count(*) from sqlite_schema where type='table';"`.chomp.to_i
        restored_size = File.size(backup)
        original_tables_count = `sqlite3 #{database} "select count(*) from sqlite_schema where type='table';"`.chomp.to_i
        original_size = File.size(database)

        Dir.glob(backup + "*").each { |file| File.delete(file) }

        {
          "size" => {"original" => original_size, "restored" => restored_size},
          "tables" => {"original" => original_tables_count, "restored" => restored_tables_count}
        }
      end

      def databases(async: false, **argv)
        execute("databases", argv, async: async, hashify: true)
      end

      def generations(database, async: false, **argv)
        raise DatabaseRequiredException, "database argument is required for generations command, e.g. litestream:generations -- --database=path/to/database.sqlite" if database.nil?

        execute("generations", argv, database, async: async, hashify: true)
      end

      def snapshots(database, async: false, **argv)
        raise DatabaseRequiredException, "database argument is required for snapshots command, e.g. litestream:snapshots -- --database=path/to/database.sqlite" if database.nil?

        execute("snapshots", argv, database, async: async, hashify: true)
      end

      private

      def execute(command, argv = {}, database = nil, async: false, hashify: false)
        cmd = prepare(command, argv, database)
        run(cmd, async: async, hashify: hashify)
      end

      def prepare(command, argv = {}, database = nil)
        if Litestream.configuration
          ENV["LITESTREAM_REPLICA_BUCKET"] ||= Litestream.configuration.replica_bucket
          ENV["LITESTREAM_ACCESS_KEY_ID"] ||= Litestream.configuration.replica_key_id
          ENV["LITESTREAM_SECRET_ACCESS_KEY"] ||= Litestream.configuration.replica_access_key
        end

        args = {
          "--config" => Rails.root.join("config", "litestream.yml").to_s
        }.merge(argv.stringify_keys).to_a.flatten.compact
        cmd = [executable, command, *args, database].compact
        puts cmd.inspect if ENV["DEBUG"]

        cmd
      end

      def run(cmd, async: false, hashify: false)
        if async
          # To release the resources of the Ruby process, just fork and exit.
          # The forked process executes litestream and replaces itself.
          exec(*cmd) if fork.nil?
        else
          out = `#{cmd.join(" ")}`
          text_table_to_hashes(out) if hashify
        end
      end

      def text_table_to_hashes(string)
        keys, *rows = string.split("\n").map { _1.split(/\s+/) }
        rows.map { keys.zip(_1).to_h }
      end
    end
  end
end