using System;
using Cosmos.CPU.x86;
using Cosmos.Debug.Kernel;

namespace Cosmos.CPU.x86.Memory.Old {
    public static unsafe class GlobalSystemInfo {
        private static volatile GlobalInformationTable* mGlobalInformationTable;
        public static GlobalInformationTable* GlobalInformationTable {
            get {
                EnsureInitialized();
                return mGlobalInformationTable;
            }
        }

        public static unsafe void EnsureInitialized() {
            if (mGlobalInformationTable == null) {
                // todo: should we align this structure somehow?

                var xEndOfKernel = Processor.GetEndOfKernel();
                xEndOfKernel = xEndOfKernel + (1024 * 1024); // for now, skip 1 MB
                Processor.ZeroFill(xEndOfKernel, (uint)(sizeof(GlobalInformationTable) + TotalDataLookupTableSize) * 4);
                mGlobalInformationTable = (GlobalInformationTable*)xEndOfKernel;
                uint xFirstDataLookupLocation = (uint)(xEndOfKernel + sizeof(GlobalInformationTable));
                //Debugger.DoSend("Setting FirstDataLookupTable to ");
                //Debugger.DoSendNumber(xFirstDataLookupLocation);
                mGlobalInformationTable->FirstDataLookupTable = (DataLookupTable*)xFirstDataLookupLocation;
                //Debugger.DoSend("FirstDataLookupTable was set to ");
                //Debugger.DoSendNumber((uint)mGlobalInformationTable->FirstDataLookupTable);
            }
        }

        public static uint TotalDataLookupTableSize {
            get {
                return (uint)(sizeof(DataLookupTable) + (DataLookupTable.EntriesPerTable * sizeof(DataLookupEntry)));
            }
        }
    }
}