require 'ffi'

module Stasis
  class Native
    extend FFI::Library

    ## Stasis typedefs

    typedef :uchar, :byte
    typedef :int, :xid
    typedef :int64, :lsn
    typedef :int64, :pageid
    typedef :int32, :slotid
    typedef :int16, :pageoff
    typedef :int16, :pagetype
    typedef :pointer, :iterator
    typedef :pointer, :bytes

    # Not a managed struct, won't be GC'ed
    class RecordId < FFI::Struct
      layout :page, :pageid,
             :slot, :slotid,
             :size, :int64,
    end
    typedef RecordId.by_value, :recordid

    ## Functions exported by libstasis.so

    ffi_lib "stasis"
    attach_function 'Tinit', [ ], :int
    attach_function 'Tdeinit', [ ], :int
    attach_function 'Tbegin', [ ], :xid
    attach_function 'Tcommit', [ :xid ], :int
    attach_function 'TsoftCommit', [ :xid ], :int
    attach_function 'TforceCommits', [ ], :void
    attach_function 'Tabort', [ :xid ], :int
    attach_function 'Tprepare', [ :xid ], :int
    attach_function 'Talloc', [ :xid, :int ], :recordid
    attach_function 'TrecordType', [ :xid, :recordid ], :int
    attach_function 'TrecordSize', [ :xid, :recordid ], :int
    attach_function 'Tset', [ :xid, :recordid, :bytes ], :int
    # the string is an out parameter
    attach_function 'Tread', [ :xid, :recordid, :bytes ], :int

    # The second two parameters should be -1.
    attach_function 'ThashCreate', [ :xid, :int, :int ], :recordid
    attach_function 'ThashInsert', [ :xid, :recordid,
                                     :bytes, :int, 
                                     :bytes, :int ], :int
    attach_function 'ThashRemove', [ :xid, :recordid,
                                     :bytes, :int ], :int
    ## Note: The pointer is an OUT param
    attach_function 'ThashLookup', [ :xid, :recordid,
                                     :bytes, :int, :pointer ], :int
  
    attach_function 'ThashGenericIterator', [ :xid, :recordid ], :iterator
  
    attach_function 'Titerator_next', [:xid, :iterator], :int
    ## Note: THe pointer is an OUT param
    attach_function 'Titerator_value', [:xid, :iterator, :pointer], :int
    attach_function 'Titerator_tupleDone', [:xid, :iterator ], :void
    attach_function 'Titerator_close', [:xid, :iterator], :void

    # XXX move to a different class!

    def Native.ThashLookupHelper(xid, rid, string) 
      objptrptr = MemoryPointer.new :pointer
      len = Stasis.ThashLookup(xid, rid, string, objptrptr);
      objptr = objptr.get_pointer(0)
      str = objptr.null ? nil : objptr.read_string
      objptr.free
      return str
    end


    def Native.TallocString(xid, str)
      rid = Talloc(xid, str.length+1) ## XXX str.length is wrong.
                                      ## want the size of the underlying buffer.
      Tset(xid, rid, str)
      return rid
    end
    
    def Native.TgetString(xid, rid)
      ret = " " * (TrecordSize(xid, rid)-1)
      Tread(xid, rid, ret)
      return ret
    end
    
    def Native.TsetString(xid, rid, str)
      if(str.length + 1 > TrecordSize(xid, rid)-1)
        return false # throw exception?
      else
        Tset(xid, rid, str)
        return true
      end
    end
  end
end