/*!
 * @file iso.cpp
 * CD/DVD Reading.
 * This is a huge mess
 */

#include "common/log/log.h"
#include <cstring>
#include <cstdio>
#include "iso.h"
#include "iso_cd.h"
#include "iso_queue.h"
#include "iso_api.h"
#include "game/sce/iop.h"
#include "stream.h"
#include "dma.h"
#include "fake_iso.h"
#include "game/common/dgo_rpc_types.h"
#include "common/util/assert.h"

using namespace iop;

u32 ISOThread();
u32 DGOThread();
u32 ProcessVAGData(IsoMessage* _cmd, IsoBufferHeader* buffer_header);
u32 RunDGOStateMachine(IsoMessage* _cmd, IsoBufferHeader* buffer_header);
u32 CopyDataToEE(IsoMessage* _cmd, IsoBufferHeader* buffer_header);
u32 CopyDataToIOP(IsoMessage* _cmd, IsoBufferHeader* buffer_header);
u32 NullCallback(IsoMessage* _cmd, IsoBufferHeader* buffer_header);

constexpr int VAGDIR_SIZE = 0x28b4;
constexpr int LOADING_SCREEN_SIZE = 0x800000;
constexpr u32 LOADING_SCREEN_DEST_ADDR = 0x1000000;

IsoFs* isofs;
u32 iso_init_flag;
s32 sync_mbx;
s32 iso_mbx;
s32 dgo_mbx;
s32 iso_thread;
s32 dgo_thread;
s32 str_thread;
s32 play_thread;
u8 gVagDir[VAGDIR_SIZE];
u32 gPlayPos;
static RPC_Dgo_Cmd sRPCBuff[1];  // todo move...
DgoCommand scmd;

void iso_init_globals() {
  isofs = nullptr;
  iso_init_flag = 0;
  sync_mbx = 0;
  iso_mbx = 0;
  dgo_mbx = 0;
  iso_thread = 0;
  dgo_thread = 0;
  str_thread = 0;
  play_thread = 0;
  memset(gVagDir, 0, sizeof(gVagDir));
  gPlayPos = 0;
  memset(sRPCBuff, 0, sizeof(sRPCBuff));
  memset(&scmd, 0, sizeof(DgoCommand));
}

/*!
 * Initialize the ISO Driver.
 * Requires a buffer large enough to hold 3 sector (or 4 if you have DUP files)
 */
void InitDriver(u8* buffer) {
  MsgPacket msg_packet;

  if (!isofs->init(buffer)) {
    // succesful init!
    iso_init_flag = 0;
  }

  // you idiots, you're giving the kernel a pointer to a stack variable!
  // (this is fixed in Jak 1 Japan and NTSC Greatest Hits)
  SendMbx(sync_mbx, &msg_packet);
}

/*!
 * Does the messagebox have a message in it?
 */
u32 LookMbx(s32 mbx) {
  MsgPacket* msg_packet;
  return PollMbx((&msg_packet), mbx) != KE_MBOX_NOMSG;
}

/*!
 * Wait for a messagebox to have a message. This is inefficient and polls with a 100 us wait.
 * This is stupid because the IOP does have much better syncronization primitives so you don't have
 * to do this.
 */
void WaitMbx(s32 mbx) {
  while (!LookMbx(mbx)) {
    DelayThread(100);
  }
}

/*!
 * Initialize the ISO FileSystem system.
 * Returns 0 on success.
 */
u32 InitISOFS(const char* fs_mode, const char* loading_screen) {
  // in retail:
  // isofs = &iso_cd;

  // ADDED
  if (!strcmp(fs_mode, "iso_cd")) {
    isofs = &iso_cd_;
  } else if (!strcmp(fs_mode, "fakeiso")) {
    isofs = &fake_iso;
  } else {
    printf("[OVERLORD ISO] ISOFS has unknown fs_mode %s\n", fs_mode);
  }
  // END ADDED

  // mark us as NOT initialized.
  iso_init_flag = 1;

  // TODO ADD
  //  while(!DMA_SendToSPUAndSync(&VAG_SilentLoop, 0x30, gTrapSRAM)) {
  //    DelayThread(1000);
  //  }

  // INITIALIZE MESSAGE BOXES
  MbxParam mbx_param;
  mbx_param.attr = 0;
  mbx_param.option = 0;
  iso_mbx = CreateMbx(&mbx_param);
  if (iso_mbx <= 0) {
    return 1;
  }

  mbx_param.attr = 0;
  mbx_param.option = 0;
  dgo_mbx = CreateMbx(&mbx_param);
  if (dgo_mbx <= 0) {
    return 1;
  }

  mbx_param.attr = 0;
  mbx_param.option = 0;
  sync_mbx = CreateMbx(&mbx_param);
  if (sync_mbx <= 0) {
    return 1;
  }

  // INITIALIZE THREADS
  ThreadParam thread_param;
  thread_param.attr = TH_C;
  thread_param.initPriority = 100;
  thread_param.stackSize = 0x1000;
  thread_param.option = 0;
  thread_param.entry = (void*)ISOThread;
  strcpy(thread_param.name, "ISOThread");
  iso_thread = CreateThread(&thread_param);
  if (iso_thread <= 0) {
    return 1;
  }

  thread_param.attr = TH_C;
  thread_param.initPriority = 98;
  thread_param.stackSize = 0x800;
  thread_param.option = 0;
  thread_param.entry = (void*)DGOThread;
  strcpy(thread_param.name, "DGOThread");
  dgo_thread = CreateThread(&thread_param);
  if (dgo_thread <= 0) {
    return 1;
  }

  thread_param.attr = TH_C;
  thread_param.initPriority = 97;
  thread_param.stackSize = 0x800;
  thread_param.option = 0;
  thread_param.entry = (void*)STRThread;
  strcpy(thread_param.name, "STRThread");
  str_thread = CreateThread(&thread_param);
  if (str_thread <= 0) {
    return 1;
  }

  thread_param.attr = TH_C;
  thread_param.initPriority = 97;
  thread_param.stackSize = 0x800;
  thread_param.option = 0;
  thread_param.entry = (void*)PLAYThread;
  strcpy(thread_param.name, "PLAYThread");
  play_thread = CreateThread(&thread_param);
  if (play_thread <= 0) {
    return 1;
  }

  // Start the threads!
  StartThread(iso_thread, 0);
  StartThread(dgo_thread, 0);
  StartThread(str_thread, 0);
  StartThread(play_thread, 0);

  // wait for ISO Thread to initialize
  WaitMbx(sync_mbx);

  // LOAD VAGDIR file
  FileRecord* vagdir_file = FindISOFile("VAGDIR.AYB");
  if (vagdir_file) {
    LoadISOFileToIOP(vagdir_file, gVagDir, VAGDIR_SIZE);
  }
  FileRecord* loading_screen_file = FindISOFile(loading_screen);
  if (loading_screen_file) {
    LoadISOFileToEE(loading_screen_file, LOADING_SCREEN_DEST_ADDR, LOADING_SCREEN_SIZE);
  }

  // should be set by ISOThread to 0 before the WaitMbx(sync_mbx);
  return iso_init_flag;
}

/*!
 * Find a file by name.  Return nullptr if it fails.
 */
FileRecord* FindISOFile(const char* name) {
  return isofs->find(name);
}

/*!
 * Get the length of an ISO File by FileRecord
 */
u32 GetISOFileLength(FileRecord* f) {
  return isofs->get_length(f);
}

struct VagDirEntry {
  union {
    char name[8];
    s32 name_as_s32s[2];
  };

  u32 unknown;
};
static_assert(sizeof(VagDirEntry) == 12, "bad size of VagDirEntry");

/*!
 * Find VAG file by "name", where name is 8 bytes (chars with spaces at the end, treated as two
 * s32's). Returns pointer to name in the VAGDIR file data.
 */
VagDirEntry* FindVAGFile(s32* name) {
  // First 4 bytes of VAGDIR file are the number of entries.
  // Next is a list of entries.
  VagDirEntry* entry = (VagDirEntry*)(gVagDir + 4);

  // loop over entries
  for (s32 idx = 0; idx < *(s32*)gVagDir; idx++) {
    // check if matching name
    if (entry->name_as_s32s[0] == name[0] && entry->name_as_s32s[1] == name[1]) {
      return entry;
    }
    entry++;
  }
  return nullptr;
}

/*!
 * The CD/DVD Reading Thread. This is a mess.
 */
u32 ISOThread() {
  // Initialize!
  InitBuffers();
  auto temp_buffer = AllocateBuffer(BUFFER_PAGE_SIZE);
  InitDriver(temp_buffer->get_data());  // unblocks InitISOFS's WaitMbx
  FreeBuffer(temp_buffer);

  VagCommand* in_progress_vag_command = nullptr;

  // main CD/DVD read loop
  for (;;) {
    /////////////////////////////////////
    // Receive Messages and Add to Queue
    /////////////////////////////////////

    // receive a message
    IsoMessage* msg_from_mbx;
    IsoCommandLoadSingle* load_single_cmd;
    s32 mbx_status = PollMbx((MsgPacket**)(&msg_from_mbx), iso_mbx);
    load_single_cmd = (IsoCommandLoadSingle*)msg_from_mbx;

    if (mbx_status == 0) {
      // we got a new message!

      // initialize fields of the message
      msg_from_mbx->callback_buffer = nullptr;
      msg_from_mbx->ready_for_data = 1;
      msg_from_mbx->callback_function = NullCallback;
      msg_from_mbx->fd = nullptr;

      if (msg_from_mbx->cmd_id == LOAD_TO_EE_CMD_ID || msg_from_mbx->cmd_id == LOAD_TO_IOP_CMD_ID ||
          msg_from_mbx->cmd_id == LOAD_TO_EE_OFFSET_CMD_ID) {
        // A Simple File Load, add it to the queue
        if (QueueMessage(msg_from_mbx, 2, "LoadSingle")) {
          // if queued successfully, start by opening the file:
          if (load_single_cmd->cmd_id == LOAD_TO_EE_OFFSET_CMD_ID) {
            load_single_cmd->fd =
                isofs->open(load_single_cmd->file_record, load_single_cmd->offset);
          } else {
            // open takes -1 as "no offset", same as 0.
            load_single_cmd->fd = isofs->open(load_single_cmd->file_record, -1);
          }

          // Check to see if it opened correctly:
          if (!load_single_cmd->fd) {
            // nope, set the status to indicate we failed
            load_single_cmd->status = CMD_STATUS_FAILED_TO_OPEN;
            // remove us from the queue...
            UnqueueMessage(load_single_cmd);
            // and wake up whoever requested this.
            ReturnMessage(load_single_cmd);
          } else {
            // yep, opened correctly. Set up the pointers/sizes
            load_single_cmd->dst_ptr = load_single_cmd->dest_addr;
            load_single_cmd->bytes_done = 0;
            // by default, copy size is the full file.
            load_single_cmd->length_to_copy = isofs->get_length(load_single_cmd->file_record);

            if (load_single_cmd->length_to_copy == 0) {
              // if we get zero for some reason, use the commanded length.
              assert(false);
              load_single_cmd->length_to_copy = load_single_cmd->length;
            } else if (load_single_cmd->length < load_single_cmd->length_to_copy) {
              // if we ask for less than the full length, use the smaller value.
              load_single_cmd->length_to_copy = load_single_cmd->length;
            }

            // set status and callback function.
            load_single_cmd->status = CMD_STATUS_IN_PROGRESS;
            switch (msg_from_mbx->cmd_id) {
              case LOAD_TO_EE_CMD_ID:
              case LOAD_TO_EE_OFFSET_CMD_ID:
                msg_from_mbx->callback_function = CopyDataToEE;
                break;
              case LOAD_TO_IOP_CMD_ID:
                msg_from_mbx->callback_function = CopyDataToIOP;
                break;
            }
          }
        }
      } else if (msg_from_mbx->cmd_id == LOAD_DGO_CMD_ID) {
        // Got a DGO command. There is one LoadDGO command for the entire DGO.
        if (QueueMessage(msg_from_mbx, 0, "LoadDGO")) {
          // queued successfully, open the file.
          load_single_cmd->fd = isofs->open(load_single_cmd->file_record, -1);
          if (!load_single_cmd->fd) {
            // failed to open, return error
            load_single_cmd->status = CMD_STATUS_FAILED_TO_OPEN;
            UnqueueMessage(load_single_cmd);
            ReturnMessage(load_single_cmd);
          } else {
            // init DGO state machine and register as the callback.
            load_single_cmd->status = CMD_STATUS_IN_PROGRESS;
            ((DgoCommand*)load_single_cmd)->dgo_state = DgoState::Init;
            load_single_cmd->callback_function = RunDGOStateMachine;
          }
        }
      } else if (msg_from_mbx->cmd_id == LOAD_SOUND_BANK) {
        // if there's an in progress vag command, try again.
        if (!in_progress_vag_command || !in_progress_vag_command->field_0x3c) {
          auto buff = TryAllocateBuffer(BUFFER_PAGE_SIZE);
          if (!buff) {
            // no buffers, try again.
            SendMbx(iso_mbx, msg_from_mbx);
          } else {
            // todo - actual load here
            auto* cmd = (SoundBankLoadCommand*)msg_from_mbx;
            printf("Ignoring request to load sound bank %s\n", cmd->bank_name);
            FreeBuffer(buff);
            ReturnMessage(msg_from_mbx);
          }
        } else {
          // just try again...
          SendMbx(iso_mbx, msg_from_mbx);
        }
      }

      else {
        printf("[OVERLORD] Unknown ISOThread message id 0x%x\n", msg_from_mbx->cmd_id);
      }

      // TODO magic number
    } else if (mbx_status == -0x1a9) {
      return 0;
    }

    ////////////////////////////
    // Handle Sound (TODO)
    ////////////////////////////

    ////////////////////////////
    // Begin a read
    ////////////////////////////

    IsoBufferHeader* read_buffer = nullptr;
    IsoMessage* cmd_to_process = GetMessage();
    if (cmd_to_process) {  // okay, there's a command queued that we should process
      // prep for a read !! DANGER !! - this read _may_ complete after the command is done.
      // At this point we don't know if the command actually needs another read or not!
      if (cmd_to_process->callback_function == ProcessVAGData) {
        read_buffer = AllocateBuffer(STR_BUFFER_DATA_SIZE);
      } else {
        read_buffer = AllocateBuffer(BUFFER_PAGE_SIZE);
      }

      if (!read_buffer) {
        // there aren't enough buffers.  give up on this command for now.
        cmd_to_process = nullptr;
      } else {
        // kick off read
        if (cmd_to_process->callback_function == ProcessVAGData) {
          cmd_to_process->status =
              isofs->begin_read(cmd_to_process->fd, read_buffer->get_data(), STR_BUFFER_DATA_SIZE);
        } else {
          cmd_to_process->status =
              isofs->begin_read(cmd_to_process->fd, read_buffer->get_data(), BUFFER_PAGE_SIZE);
        }

        // if we have bad status, kill read buffer
        if (cmd_to_process->status != CMD_STATUS_IN_PROGRESS) {
          FreeBuffer(read_buffer);
          read_buffer = nullptr;
          cmd_to_process = nullptr;
        }
      }
    }

    if (!cmd_to_process) {
      // drive is doing nothing, make sure the DVD is still in there.
      isofs->poll_drive();
    }

    // Deal with completed reads.  NOTE - this can close files and terminate return commands!
    ProcessMessageData();

    if (!read_buffer) {
      // didn't actually start a read, just delay for a bit I guess.
      DelayThread(100);
    } else {
      // attempt to sync read.  If we closed the file mid-read in ProcessMessageData, this returns
      // an error code.
      u32 read_status = isofs->sync_read();
      if (read_status == CMD_STATUS_READ_ERR) {
        // closed file mid-read, or the read failed.  Either way we can't give this read buffer to
        // anybody, so we should just free it.
        FreeBuffer(read_buffer);
      } else {
        // read is good!
        cmd_to_process->status = read_status;
        // setup the buffer for the callback.
        if (cmd_to_process->callback_function == ProcessVAGData) {
          read_buffer->data = read_buffer->get_data();
          read_buffer->data_size = STR_BUFFER_DATA_SIZE;
        } else {
          read_buffer->data = read_buffer->get_data();
          read_buffer->data_size = BUFFER_PAGE_SIZE;
        }

        // add buffer to linked list of buffers.
        if (!cmd_to_process->callback_buffer) {
          cmd_to_process->callback_buffer = read_buffer;
        } else {
          auto* bh = cmd_to_process->callback_buffer;
          while (bh->next) {
            bh = (IsoBufferHeader*)bh->next;
          }
          bh->next = read_buffer;
        }
      }
    }
  }  // for
  return 0;
}

/*!
 * Handler for DGO data buffers.
 */
u32 RunDGOStateMachine(IsoMessage* _cmd, IsoBufferHeader* buffer) {
  auto* cmd = (DgoCommand*)_cmd;
  u32 return_value = CMD_STATUS_IN_PROGRESS;
  u8* unprocessed_data = (u8*)buffer->data;
  u32 bytes_left = buffer->data_size;

  // loop until we've read all the data
  while (bytes_left) {
    // printf("run DGO in state %d (%s) with %d unprocessed buffered bytes\n", cmd->dgoState,
    // names[cmd->dgoState], buffer->data_size);
    switch (cmd->dgo_state) {
      case DgoState::Init:  // init
        cmd->bytes_processed = 0;
        // start by reading header.
        cmd->dgo_state = DgoState::Read_Header;
        cmd->finished_first_obj = 0;
        cmd->want_abort = 0;
        break;

      case DgoState::Read_Header:  // read dgo header.  If we are unlucky this crosses a boundary
                                   // and we have to do this in two chunks
      {
        u32 bytes_to_read = sizeof(DgoHeader) - cmd->bytes_processed;
        if (bytes_to_read > bytes_left) {
          bytes_to_read = bytes_left;
        }

        // copy to our local storage
        memcpy((u8*)&cmd->dgo_header + cmd->bytes_processed, unprocessed_data, bytes_to_read);
        unprocessed_data += bytes_to_read;
        bytes_left -= bytes_to_read;
        cmd->bytes_processed += bytes_to_read;

        // if we are done with header
        if (cmd->bytes_processed == sizeof(DgoHeader)) {
          // printf("[Overlord DGO] Got DGO file header for %s with %d objects\n",
          // cmd->dgo_header.name,
          // cmd->dgo_header.object_count);  // added
          lg::info("[Overlord DGO] Got DGO file header for {} with {} objects",
                   cmd->dgo_header.name, cmd->dgo_header.object_count);
          cmd->bytes_processed = 0;
          cmd->objects_loaded = 0;
          if (cmd->dgo_header.object_count == 1) {
            // if there's only one object, load to top immediately
            cmd->buffer_toggle = 0;
            cmd->ee_destination_buffer = cmd->buffer_heaptop;
            cmd->dgo_state = DgoState::Read_Obj_Header;
          } else {
            // otherwise load to buffer1 first.
            cmd->buffer_toggle = 1;
            cmd->ee_destination_buffer = cmd->buffer1;
            cmd->dgo_state = DgoState::Read_Obj_Header;
          }
        }
      } break;

      case DgoState::Finish_Obj:  // we have reached the end of an object file!
      {
        // EE synchronization occurs here.
        // we skip this if we're loading the first object so we can double buffer the
        // linking/loading process and have two in flight at a time (one loading, other linking)
        if (cmd->finished_first_obj) {
          s32 isSync = LookMbx(sync_mbx);  // did we get a "sync" message?
          if (isSync) {
            // if so, this means we got a CancelDGO or NextDGO
            if (cmd->want_abort) {
              // we got a CancelDGO.
              cmd->dgo_state = DgoState::Finish_Dgo;
              break;
            }
          } else {
            // nope, ee isn't ready. bail and wait for next run.
            goto cleanup_and_return;
          }
        }

        cmd->finished_first_obj = 1;
        cmd->status = CMD_STATUS_IN_PROGRESS;

        // select a buffer for next time.
        if (cmd->buffer_toggle == 1) {
          cmd->selectedBuffer = cmd->buffer1;
        } else {
          cmd->selectedBuffer = cmd->buffer2;
        }

        // we've processed the command, go wake up the DGO RPC thread.
        // doesn't terminate the command (ReleaseMessage does this, ReturnMessage just
        // wakes up the caller while keeping the command alive).
        ReturnMessage(cmd);

        // toggle buffer
        if (cmd->buffer_toggle == 1) {
          cmd->ee_destination_buffer = cmd->buffer2;
          cmd->buffer_toggle = 2;
        } else {
          cmd->ee_destination_buffer = cmd->buffer1;
          cmd->buffer_toggle = 1;
        }

        // setup for next run
        if (cmd->objects_loaded + 1 == cmd->dgo_header.object_count) {
          cmd->dgo_state = DgoState::Read_Last_Obj;
        } else {
          cmd->dgo_state = DgoState::Read_Obj_Header;
        }
        break;
      }

      case DgoState::Read_Last_Obj:  // setup load last
      {
        // extra sync here
        s32 sync = LookMbx(sync_mbx);
        if (sync) {
          if (cmd->want_abort) {
            cmd->dgo_state = DgoState::Finish_Dgo;
          } else {
            // EE ready, no abort. Nothing in flight, so we are safe to do a top load!
            cmd->ee_destination_buffer = cmd->buffer_heaptop;
            cmd->buffer_toggle = 0;
            cmd->dgo_state = DgoState::Read_Obj_Header;
          }
        } else {
          goto cleanup_and_return;
        }
      } break;

      case DgoState::Read_Obj_Header:  // read object file header
      {
        u32 bytesToRead = sizeof(ObjectHeader) - cmd->bytes_processed;
        if (bytes_left < bytesToRead) {
          bytesToRead = bytes_left;
        }

        // for now, buffer locally
        memcpy((u8*)&cmd->objHeader + cmd->bytes_processed, unprocessed_data, bytesToRead);
        unprocessed_data += bytesToRead;
        bytes_left -= bytesToRead;
        cmd->bytes_processed += bytesToRead;

        // once we're done, send the header to the EE, and start reading object data
        if (cmd->bytes_processed == sizeof(ObjectHeader)) {
          //          printf("[Overlord DGO] Got object header for %s, object size 0x%x bytes (sent
          //          to 0x%p)\n",
          //                 cmd->objHeader.name, cmd->objHeader.size, cmd->ee_destination_buffer);
          DMA_SendToEE(&cmd->objHeader, sizeof(ObjectHeader), cmd->ee_destination_buffer);
          DMA_Sync();
          cmd->ee_destination_buffer += sizeof(ObjectHeader);
          cmd->objHeader.size = (cmd->objHeader.size + 0xf) & 0xfffffff0;
          cmd->dgo_state = DgoState::Read_Obj_data;
          cmd->bytes_processed = 0;
        }
      } break;

      case DgoState::Read_Obj_data:  // read object file data
      {
        u32 bytesToRead = cmd->objHeader.size - cmd->bytes_processed;
        if (bytes_left < bytesToRead) {
          bytesToRead = bytes_left;
        }

        // send contents directly to EE
        DMA_SendToEE(unprocessed_data, bytesToRead, cmd->ee_destination_buffer);
        DMA_Sync();
        unprocessed_data += bytesToRead;
        bytes_left -= bytesToRead;
        cmd->ee_destination_buffer += bytesToRead;
        cmd->bytes_processed += bytesToRead;

        if (cmd->bytes_processed == cmd->objHeader.size) {
          cmd->objects_loaded++;
          if (cmd->objects_loaded == cmd->dgo_header.object_count) {
            cmd->dgo_state = DgoState::Finish_Dgo;
          } else {
            cmd->dgo_state = DgoState::Finish_Obj;
            cmd->bytes_processed = 0;
          }
        }
      } break;

      case DgoState::Finish_Dgo: {
        // done with buffer, complete. Kill the ISO thread read.
        return_value = CMD_STATUS_DONE;
        goto cleanup_and_return;
      }

      default:
        printf("unknown dgoState!\n");
    }
  }

  //  printf("[DGO State Machine Complete] Out of things to read!\n");

cleanup_and_return:
  if (return_value == 0) {
    buffer->data = nullptr;
    buffer->data_size = 0;
  } else {
    if (!bytes_left) {
      buffer->data = nullptr;
      buffer->data_size = 0;
    } else {
      buffer->data = unprocessed_data;
      buffer->data_size = bytes_left;
    }
  }
  return return_value;
}

/*!
 * Callback for sending to EE.
 */
u32 CopyDataToEE(IsoMessage* _cmd, IsoBufferHeader* buffer_header) {
  auto* cmd = (IsoCommandLoadSingle*)_cmd;

  s32 bytes_to_send = cmd->length_to_copy - cmd->bytes_done;

  // make sure we don't copy too much (if the buffer does not have enough data)
  if (buffer_header->data_size < (u32)bytes_to_send) {
    bytes_to_send = (s32)buffer_header->data_size;
  }

  DMA_SendToEE(buffer_header->get_data(), bytes_to_send, cmd->dest_addr);
  DMA_Sync();

  cmd->dest_addr += bytes_to_send;
  cmd->bytes_done += bytes_to_send;
  buffer_header->data = nullptr;
  buffer_header->data_size = 0;
  if (cmd->bytes_done == cmd->length_to_copy) {
    return CMD_STATUS_DONE;
  } else {
    return CMD_STATUS_IN_PROGRESS;
  }
}

/*!
 * Callback for loading to IOP buffer.
 */
u32 CopyDataToIOP(IsoMessage* _cmd, IsoBufferHeader* buffer_header) {
  auto* cmd = (IsoCommandLoadSingle*)_cmd;

  s32 bytes_to_send = cmd->length_to_copy - cmd->bytes_done;

  // make sure we don't copy too much (if the buffer does not have enough data)
  if (buffer_header->data_size < (u32)bytes_to_send) {
    bytes_to_send = (s32)buffer_header->data_size;
  }

  memcpy(cmd->dst_ptr, buffer_header->get_data(), bytes_to_send);

  cmd->dst_ptr += bytes_to_send;
  cmd->bytes_done += bytes_to_send;
  buffer_header->data = nullptr;
  buffer_header->data_size = 0;
  if (cmd->bytes_done == cmd->length_to_copy) {
    return CMD_STATUS_DONE;
  } else {
    return CMD_STATUS_IN_PROGRESS;
  }
}

/*!
 * Callback which does nothing.
 */
u32 NullCallback(IsoMessage* _cmd, IsoBufferHeader* buffer_header) {
  (void)_cmd;
  buffer_header->data_size = 0;
  return CMD_STATUS_NULL_CB;
}

/*!
 * Initialize a VagCommand.
 */
void InitVAGCmd(VagCommand* cmd, u32 x) {
  cmd->field_0x30 = 0;
  cmd->field_0x34 = 0;
  cmd->field_0x38 = 0;
  cmd->field_0x3c = x;
  cmd->field_0x40 = 0;
  cmd->field_0x44 = 0;
  cmd->field_0x48 = 0xffffffff;
  gPlayPos = 0x30;
  cmd->messagebox_to_reply = 0;
  cmd->thread_id = 0;
}

/*!
 * Byte-swap.
 */
u32 bswap(u32 in) {
  return ((in >> 0x18) & 0xff) | ((in >> 8) & 0xff00) | ((in & 0xff00) << 8) | (in << 0x18);
}

/*!
 * TODO - implement.
 */
u32 ProcessVAGData(IsoMessage* _cmd, IsoBufferHeader* buffer_header) {
  (void)_cmd;
  (void)buffer_header;
  assert(false);
  return 0;
}

// TODO - StopVAG
// TODO - PauseVAG
// TODO - CalculateVAGVolumes
// TODO - UnpauseVAG
// TODO - SetVAGVol
// TODO - GetPlayPos
// TODO - UpdatePlayPos
// TODO - CheckVAGStreamProgress

void* RPC_DGO(unsigned int fno, void* _cmd, int y);
void LoadDGO(RPC_Dgo_Cmd* cmd);
void LoadNextDGO(RPC_Dgo_Cmd* cmd);
void CancelDGO(RPC_Dgo_Cmd* cmd);

/*!
 * DGO RPC Thread.
 */
u32 DGOThread() {
  sceSifQueueData dq;
  sceSifServeData serve;

  // setup RPC.
  CpuDisableIntr();
  sceSifInitRpc(0);
  sceSifSetRpcQueue(&dq, GetThreadId());
  sceSifRegisterRpc(&serve, DGO_RPC_ID, RPC_DGO, sRPCBuff, nullptr, nullptr, &dq);
  CpuEnableIntr();
  sceSifRpcLoop(&dq);
  return 0;
}

/*!
 * DGO RPC Handler.
 */
void* RPC_DGO(unsigned int fno, void* _cmd, int y) {
  (void)y;
  auto* cmd = (RPC_Dgo_Cmd*)_cmd;
  // call appropriate handler.
  switch (fno) {
    case DGO_RPC_LOAD_FNO:
      LoadDGO(cmd);
      break;
    case DGO_RPC_LOAD_NEXT_FNO:
      LoadNextDGO(cmd);
      break;
    case DGO_RPC_CANCEL_FNO:
      CancelDGO(cmd);
      break;
    default:
      cmd->result = DGO_RPC_RESULT_ERROR;
  }
  return cmd;
}

/*!
 * Begin loading a DGO.  Returns when the first obj is loaded.
 * Then will load the next obj into the second buffer.
 * Then the DGO loader will block until LoadNextDGO is called.
 * This approach keeps two loads in flight at a time to increase loading throughput.
 * One load will be read from DVD / DMA'd to EE
 * Another will be linked on the EE.
 * The final load is done directly onto the heap, and isn't double buffered
 * (otherwise the linking object could allocate on the heap where the final loading object is
 * being copied).  This avoids having to relocate the data from the temporary load buffer to the
 * heap, and is the only way to make sure that the entire heap can be filled.
 */
void LoadDGO(RPC_Dgo_Cmd* cmd) {
  // Find the file
  FileRecord* fr = isofs->find(cmd->name);
  if (!fr) {
    cmd->result = DGO_RPC_RESULT_ERROR;
    return;
  }

  // cancel an in progress command and wait for it to end.
  // note - this doesn't handle a nullptr correctly, so if this actually ends up cancelling
  // it will crash.
  CancelDGO(nullptr);

  // set up the ISO Command
  scmd.cmd_id = LOAD_DGO_CMD_ID;
  scmd.messagebox_to_reply = dgo_mbx;
  scmd.thread_id = 0;
  scmd.buffer1 = (u8*)(u64)(cmd->buffer1);
  scmd.buffer2 = (u8*)(u64)(cmd->buffer2);
  scmd.buffer_heaptop = (u8*)(u64)(cmd->buffer_heap_top);
  scmd.fr = fr;

  // send the command to ISO Thread
  SendMbx(iso_mbx, &scmd);

  // wait for the ReturnMessage in the DGO callback state machine.
  // this happens when the first file is loaded
  WaitMbx(dgo_mbx);

  if (scmd.status == CMD_STATUS_IN_PROGRESS) {
    // we got one, but there's more to load.
    // we don't set cmd->buffer1 as it's already the correct buffer in this case -
    // when there are >1 objs, we load into buffer1 first.
    cmd->result = DGO_RPC_RESULT_MORE;
  } else if (scmd.status == CMD_STATUS_DONE) {
    // all done! make sure our reply says we loaded to the top.
    cmd->result = DGO_RPC_RESULT_DONE;
    cmd->buffer1 = cmd->buffer_heap_top;
    scmd.cmd_id = 0;
  } else {
    // error.
    cmd->result = DGO_RPC_RESULT_ERROR;
    scmd.cmd_id = 0;
  }
}

/*!
 * Signal to the IOP it can keep loading and overwrite the oldest obj buffer.
 * This will return when there's another loaded obj.
 */
void LoadNextDGO(RPC_Dgo_Cmd* cmd) {
  if (scmd.cmd_id == 0) {
    // something went wrong.
    cmd->result = DGO_RPC_RESULT_ERROR;
  } else {
    // update heap location
    scmd.buffer_heaptop = (u8*)(u64)cmd->buffer_heap_top;
    // allow DGO state machine to advance
    SendMbx(sync_mbx, nullptr);
    // wait for another load to finish.
    WaitMbx(dgo_mbx);
    // another load finished, respond with the result.
    if (scmd.status == CMD_STATUS_IN_PROGRESS) {
      // more, use the selected buffer.
      cmd->result = DGO_RPC_RESULT_MORE;
      cmd->buffer1 = (u32)(u64)scmd.selectedBuffer;
    } else if (scmd.status == CMD_STATUS_DONE) {
      // last obj, always loaded to top.
      cmd->result = DGO_RPC_RESULT_DONE;
      cmd->buffer1 = cmd->buffer_heap_top;
      scmd.cmd_id = 0;
    } else {
      cmd->result = DGO_RPC_RESULT_ERROR;
      scmd.cmd_id = 0;
    }
  }
}

/*!
 * Abort an in progress load.
 */
void CancelDGO(RPC_Dgo_Cmd* cmd) {
  if (scmd.cmd_id) {
    scmd.want_abort = 1;
    // wake up DGO state machine with abort
    SendMbx(sync_mbx, nullptr);
    // wait for it to abort.
    WaitMbx(dgo_mbx);
    // this will cause a crash if we cancel because we try to load 2 dgos at the same time.
    // this should succeed if it's an actual cancel because we changed which level we're trying to
    // load.
    assert(cmd);
    cmd->result = DGO_RPC_RESULT_ABORTED;
    scmd.cmd_id = 0;
  }
}

// TODO - GetVAGStreamPos
// TODO - VAG_MarkLoopStart
// TODO - VAG_MarkLoopEnd
// TODO - VAG_MarkNonloopStart
// TODO - VAG_MarkNonloopEnd