# frozen_string_literal: true

class Minitar
  # The class that writes a tar format archive to a data stream.
  class Writer
    # The exception raised when the user attempts to write more data to
    # a BoundedWriteStream than has been allocated.
    WriteBoundaryOverflow = Class.new(StandardError)

    # A stream wrapper that can only be written to. Any attempt to read from this
    # restricted stream will result in a NameError being thrown.
    class WriteOnlyStream
      def initialize(io)
        @io = io
      end

      def write(data) = @io.write(data)
    end

    private_constant :WriteOnlyStream

    # A WriteOnlyStream that also has a size limit.
    class BoundedWriteStream < WriteOnlyStream
      # The maximum number of bytes that may be written to this data stream.
      attr_reader :limit
      # The current total number of bytes written to this data stream.
      attr_reader :written

      def initialize(io, limit)
        @io = io
        @limit = limit
        @written = 0
      end

      def write(data)
        size = data.bytesize
        raise WriteBoundaryOverflow if (size + @written) > @limit
        @io.write(data)
        @written += size
        size
      end
    end

    private_constant :BoundedWriteStream

    # With no associated block, +Writer::open+ is a synonym for +Writer::new+. If the
    # optional code block is given, it will be passed the new _writer_ as an argument and
    # the Writer object will automatically be closed when the block terminates. In this
    # instance, +Writer::open+ returns the value of the block.
    #
    # :call-seq:
    #    w = Minitar::Writer.open(STDOUT)
    #    w.add_file_simple('foo.txt', :size => 3)
    #    w.close
    #
    #    Minitar::Writer.open(STDOUT) do |w|
    #      w.add_file_simple('foo.txt', :size => 3)
    #    end
    def self.open(io) # :yields: Writer
      writer = new(io)
      return writer unless block_given?

      # This exception context must remain, otherwise the stream closes on open even if
      # a block is not given.
      begin
        yield writer
      ensure
        writer.close
      end
    end

    # Creates and returns a new Writer object.
    def initialize(io)
      @io = io
      @closed = false
    end

    # Adds a file to the archive as +name+. The data can be provided in the
    # <tt>opts[:data]</tt> or provided to a BoundedWriteStream that is yielded to the
    # provided block.
    #
    # If <tt>opts[:data]</tt> is provided, all other values to +opts+ are optional. If the
    # data is provided to the yielded BoundedWriteStream, <tt>opts[:size]</tt> must be
    # provided.
    #
    # Valid parameters to +opts+ are:
    #
    # <tt>:data</tt>::  Optional. The data to write to the archive.
    # <tt>:mode</tt>::  The Unix file permissions mode value. If not provided, defaults to
    #                   0o644.
    # <tt>:size</tt>::  The size, in bytes. If <tt>:data</tt> is provided, this parameter
    #                   may be ignored (if it is less than the size of the data provided)
    #                   or used to add padding (if it is greater than the size of the data
    #                   provided).
    # <tt>:uid</tt>::   The Unix file owner user ID number.
    # <tt>:gid</tt>::   The Unix file owner group ID number.
    # <tt>:mtime</tt>:: File modification time, interpreted as an integer.
    #
    # An exception will be raised if the Writer is already closed, or if more data is
    # written to the BoundedWriteStream than expected.
    #
    # :call-seq:
    #    writer.add_file_simple('foo.txt', :data => "bar")
    #    writer.add_file_simple('foo.txt', :size => 3) do |w|
    #      w.write("bar")
    #    end
    def add_file_simple(name, opts = {}) # :yields: BoundedWriteStream
      raise ClosedStream if @closed

      header = {
        mode: opts.fetch(:mode, 0o644),
        mtime: opts.fetch(:mtime, nil),
        gid: opts.fetch(:gid, nil),
        uid: opts.fetch(:uid, nil)
      }

      data = opts.fetch(:data, nil)
      size = opts.fetch(:size, nil)

      if block_given?
        raise ArgumentError, "Too much data (opts[:data] and block_given?)." if data
        raise ArgumentError, "No size provided" unless size
      else
        raise ArgumentError, "No data provided" unless data

        bytes = data.bytesize
        size = bytes if size.nil? || size < bytes
      end

      header[:size] = size

      short_name, prefix, needs_long_name = split_name(name)
      write_header(header, name, short_name, prefix, needs_long_name)

      os = BoundedWriteStream.new(@io, size)
      if block_given?
        yield os
      else
        os.write(data)
      end

      min_padding = size - os.written
      @io.write("\0" * min_padding)
      remainder = (512 - (size % 512)) % 512
      @io.write("\0" * remainder)
    end

    # Adds a file to the archive as +name+. The data can be provided in the
    # <tt>opts[:data]</tt> or provided to a yielded +WriteOnlyStream+. The size of the
    # file will be determined from the amount of data written to the stream.
    #
    # Valid parameters to +opts+ are:
    #
    # <tt>:mode</tt>::  The Unix file permissions mode value. If not provided, defaults to
    #                   0o644.
    # <tt>:uid</tt>::   The Unix file owner user ID number.
    # <tt>:gid</tt>::   The Unix file owner group ID number.
    # <tt>:mtime</tt>:: File modification time, interpreted as an integer.
    # <tt>:data</tt>::  Optional. The data to write to the archive.
    #
    # If <tt>opts[:data]</tt> is provided, this acts the same as #add_file_simple.
    # Otherwise, the file's size will be determined from the amount of data written to the
    # stream.
    #
    # For #add_file to be used without <tt>opts[:data]</tt>, the Writer must be wrapping
    # a stream object that is seekable. Otherwise, #add_file_simple must be used.
    #
    # +opts+ may be modified during the writing of the file to the stream.
    def add_file(name, opts = {}, &) # :yields: WriteOnlyStream, +opts+
      raise ClosedStream if @closed

      return add_file_simple(name, opts, &) if opts[:data]

      raise Minitar::NonSeekableStream unless Minitar.seekable?(@io)

      short_name, prefix, needs_long_name = split_name(name)

      data_offset = needs_long_name ? 3 * 512 : 512
      init_pos = @io.pos
      @io.write("\0" * data_offset) # placeholder for the header

      yield WriteOnlyStream.new(@io), opts

      size = @io.pos - (init_pos + data_offset)
      remainder = (512 - (size % 512)) % 512
      @io.write("\0" * remainder)

      final_pos, @io.pos = @io.pos, init_pos

      header = {
        mode: opts[:mode],
        mtime: opts[:mtime],
        size: size,
        gid: opts[:gid],
        uid: opts[:uid]
      }

      write_header(header, name, short_name, prefix, needs_long_name)

      @io.pos = final_pos
    end

    # Creates a directory entry in the tar.
    def mkdir(name, opts = {})
      raise ClosedStream if @closed

      header = {
        mode: opts[:mode],
        typeflag: "5",
        size: 0,
        gid: opts[:gid],
        uid: opts[:uid],
        mtime: opts[:mtime]
      }

      short_name, prefix, needs_long_name = split_name(name)
      write_header(header, name, short_name, prefix, needs_long_name)

      nil
    end

    # Creates a symbolic link entry in the tar.
    def symlink(name, link_target, opts = {})
      raise ClosedStream if @closed
      raise FileNameTooLong if link_target.size > 100

      name, prefix = split_name(name)
      header = {
        name: name,
        mode: opts[:mode],
        typeflag: "2",
        size: 0,
        linkname: link_target,
        gid: opts[:gid],
        uid: opts[:uid],
        mtime: opts[:mtime],
        prefix: prefix
      }
      @io.write(PosixHeader.new(header).to_s)
      nil
    end

    # Passes the #flush method to the wrapped stream, used for buffered streams.
    def flush
      raise ClosedStream if @closed
      @io.flush if @io.respond_to?(:flush)
    end

    # Returns false if the writer is open.
    def closed? = @closed

    # Closes the Writer. This does not close the underlying wrapped output stream.
    def close
      return if @closed
      @io.write("\0" * 1024)
      @closed = true
    end

    private

    def write_header(header, long_name, short_name, prefix, needs_long_name)
      if needs_long_name
        long_name_header = {
          prefix: "",
          name: PosixHeader::GNU_EXT_LONG_LINK,
          typeflag: "L",
          size: long_name.length + 1,
          mode: 0
        }
        @io.write(PosixHeader.new(long_name_header).to_s)
        @io.write(long_name)
        @io.write("\0" * (512 - (long_name.length % 512)))
      end

      new_header = header.merge({name: short_name, prefix: prefix})
      @io.write(PosixHeader.new(new_header).to_s)
    end

    def split_name(name)
      if name.bytesize <= 100
        prefix = ""
      else
        parts = name.split("/")
        newname = parts.pop

        nxt = ""

        loop do
          nxt = parts.pop || ""
          break if newname.bytesize + 1 + nxt.bytesize >= 100
          newname = "#{nxt}/#{newname}"
        end

        prefix = (parts + [nxt]).join("/")

        name = newname
      end

      [name, prefix, name.bytesize > 100 || prefix.bytesize > 155]
    end
  end
end