/**
 * Topaz's Pizza Timer
 * Built for a future video
 * https://theindustriousrabbit.video
 *
 * Copyright 2022 John Bintz
 * MIT License
 */

#include <stdio.h>

// basic amiga stuff
#include <proto/dos.h>
#include <proto/exec.h>

// allow us to load and scale fonts
#include <proto/diskfont.h>

// handle images and sound
#include <proto/datatypes.h>
#include <datatypes/datatypesclass.h>
#include <datatypes/soundclass.h>

#include <proto/timer.h>

// this is the manual for the original intuition stuff.
// not much here is different: https://ia801905.us.archive.org/33/items/Amiga_Intuition_Reference_Manaual_1985_Adn-Wesley_Publishing_Company/Amiga_Intuition_Reference_Manaual_1985_Addison-Wesley_Publishing_Company.pdf
// gadtools gives a proper set of components for building UIs.
// http://amigadev.elowar.com/read/ADCD_2.1/Libraries_Manual_guide/node0278.html
#include <proto/intuition.h>
#include <proto/gadtools.h>
#include <intuition/gadgetclass.h>

// drawin' stuff
// This is where we get font handling
#include <proto/graphics.h>

// the main app window
#define WINDOW_WIDTH (240)
#define WINDOW_HEIGHT (80)
#define WINDOW_TITLE "Topaz's Pizza Timer"
#define WINDOW_CHROME_WIDTH (4)

struct Screen *screen;
struct Window *window;
struct Gadget *windowGadgets;

#define ABOUT_WINDOW_WIDTH (350)
#define ABOUT_WINDOW_HEIGHT (75)

// Fonts!
struct TextAttr Topaz80 = { "topaz.font", 8, 0, 0 };

// There's no native 16 pixel Topaz font so we'll use
// diskfont.library to make one.
struct TextAttr Topaz160 = { "topaz.font", 16, 0, 0 };
struct TextFont *topaz80Font;
struct TextFont *topaz160Font;

// Gadtools stuff
#define START_STOP_BUTTON_ID 0
#define RESET_BUTTON_ID 1
#define HOURS_SLIDER_ID 2
#define MINUTES_SLIDER_ID 3
#define SECONDS_SLIDER_ID 5

void *visualInfo;
struct Gadget *timerGadget, *hourSlider, *minuteSlider, *secondSlider;

// gadtools menus
// https://wiki.amigaos.net/wiki/GadTools_Menus

// Why the special struct, constants and struct instantiation?
// Because this way, when we get a menu message from Intuition,
// we can look up the menu item selected by ID, rather than
// looking it up by position in the menu tree structure.
struct MenuData {
  int id;
};

// Start this at 1, otherwise not selecting a menu item is the same as
// opening the menu and picking the item with ID 0
#define MENU_ABOUT_ID 1
#define MENU_QUIT_ID 2

struct MenuData MENU_ABOUT = { MENU_ABOUT_ID };
struct MenuData MENU_QUIT = { MENU_QUIT_ID };

struct NewMenu appMenu[] = {
  { NM_TITLE, "Pizza Timer", 0, 0, 0, 0, },
  { NM_ITEM, "About...", 0, 0, 0, &MENU_ABOUT },
  { NM_ITEM, "Quit", "Q", 0, 0, &MENU_QUIT },
  { NM_END, NULL, 0, 0, 0, 0, },
};

struct Menu *menu;

// timer stuff
#define TIMER_INTERVAL 200000

struct timerequest *TimerIO;
struct timeval currentSystemTime;
struct MsgPort *timerPort;

// sound stuff
// get that bell
#define BELL_FILENAME "bell.8svx"

APTR bellSound = NULL;
struct Library *DataTypesBase;
BYTE waitForSoundSignalNumber;

// our business logic
// for how long should I cook this pizza?
unsigned int uiHours = 0;
unsigned int uiMinutes = 12;
unsigned int uiSeconds = 0;

unsigned int priorHours, originalUiHours;
unsigned int priorMinutes, originalUiMinutes;
unsigned int priorSeconds, originalUiSeconds;

char timerText[9];
ULONG timerStartTime = 0, timerDistance, timerBuild;
BOOL timerIsRunning = FALSE;
BOOL timerStarted = FALSE;
BOOL terminated = FALSE;
BOOL openAboutWindowNext = FALSE;

/**
 * Initialize system stuff.
 */
// This function, despite taking no parameters, still needs void as a
// parameter.
// http://www.hipooniosamigasite.org/amigadocs/files/LOON-DOCS-DISKS/LOON5/LatticeC.pt3
int setup(void) {
  // make sure the font exists on the computer
  // http://amigadev.elowar.com/read/ADCD_2.1/Includes_and_Autodocs_3._guide/node0308.html
  if (NULL == (topaz80Font = OpenFont(&Topaz80))) {
    return 0;
  }

  // load this via disk so it can be scaled up
  // http://amigadev.elowar.com/read/ADCD_2.1/Includes_and_Autodocs_3._guide/node0137.html
  if (NULL == (topaz160Font = OpenDiskFont(&Topaz160))) {
    return 0;
  }

  // get a handle on the Workbench screen
  if (NULL == (screen = LockPubScreen(NULL))) {
    return 0;
  }

  // Get...visual info. GadTools needs this, and it's all private.
  // secrets. secrets between gadtools and the amiga.
  // don't snoop. they wouldn't like it.
  if (NULL == (visualInfo = GetVisualInfo(screen, TAG_END))) {
    return 0;
  }

  // set up the async timer message port
  // we create this port, but it ends up in the timerequest structure when
  // we're done with the device open, so we don't have to worry about
  // hanging onto a pointer to it.
  if (NULL == (timerPort = CreatePort(0, 0))) {
    return 0;
  }
  // create an IO object we can get responses to on our timer port
  if (NULL == (TimerIO = (struct timerequest *)CreateExtIO(timerPort, sizeof(struct timerequest)))) {
    return 0;
  }

  if (NULL == (DataTypesBase = OpenLibrary("datatypes.library", 40))) {
    // this is ok, we just won't play sound
    printf("no sound!");
  } else {
    waitForSoundSignalNumber = AllocSignal(-1);
  }

  return 1;
}

/**
 * Tear down system stuff.
 */
void teardown(void) {
  // http://amigadev.elowar.com/read/ADCD_2.1/Devices_Manual_guide/node0196.html
  if (DataTypesBase) {
    CloseLibrary(DataTypesBase);
    FreeSignal(waitForSoundSignalNumber);
  }
  if (TimerIO) {
    // if the timer's still running, wait for it to be done
    if (!CheckIO((struct IORequest *)TimerIO)) {
      WaitIO((struct IORequest *)TimerIO);
    }

    DeleteExtIO((struct IORequest *)TimerIO);
  }
  if (timerPort) {
    DeletePort(timerPort);
  }
  // all right, then. keep your secrets.
  if (visualInfo) FreeVisualInfo(visualInfo);
  if (screen) UnlockPubScreen(NULL, screen);
  if (topaz80Font) CloseFont(topaz80Font);
  if (topaz160Font) CloseFont(topaz160Font);
}

/**
 * Build the GadTools gadgets for this UI.
 * Normally I'd move this to a separate piece of code,
 * but for example purposes I want everything in this one file
 * for easier searching.
 */
struct Gadget *buildUI(void) {
  struct NewGadget ng;
  struct Gadget *currentGadget;
  struct Gadget *glist;

  // Add an empty gadget for GadTools to store extra data.
  // http://amigadev.elowar.com/read/ADCD_2.1/Includes_and_Autodocs_3._guide/node0274.html
  currentGadget = CreateContext(&glist);

  ng.ng_LeftEdge = window->BorderLeft;
  ng.ng_TopEdge = window->BorderTop;
  ng.ng_Height = 12;
  ng.ng_Width = 0;
  ng.ng_GadgetText = NULL;
  ng.ng_TextAttr = &Topaz80;
  ng.ng_VisualInfo = visualInfo;

  ng.ng_GadgetID = NULL;
  ng.ng_Flags = PLACETEXT_IN;

  // Timer display
  ng.ng_Width = window->Width - window->BorderLeft - window->BorderRight;
  ng.ng_TextAttr = &Topaz160;
  ng.ng_Height = 20;

  timerGadget = currentGadget = CreateGadget(
      TEXT_KIND,
      currentGadget,
      &ng,
      GTTX_Text, &timerText,
      GTTX_Justification, GTJ_CENTER,
      TAG_END
      );

  ng.ng_TextAttr = &Topaz80;
  ng.ng_Height = 12;

  // start/stop button
  ng.ng_Width = (window->Width - window->BorderLeft - window->BorderRight) / 2;
  ng.ng_TopEdge += 18;
  if (timerIsRunning) {
    ng.ng_GadgetText = "_Stop";
  } else {
    ng.ng_GadgetText = "_Start";
  }

  ng.ng_GadgetID = START_STOP_BUTTON_ID;

  currentGadget = CreateGadget(
      BUTTON_KIND,
      currentGadget,
      &ng,
      GT_Underscore, '_',
      TAG_END
      );

  // reset button
  ng.ng_LeftEdge += ng.ng_Width; // lol reuse it
  ng.ng_GadgetText = "_Reset";
  ng.ng_GadgetID = RESET_BUTTON_ID;

  currentGadget = CreateGadget(
      BUTTON_KIND,
      currentGadget,
      &ng,
      GT_Underscore, '_',
      GA_Disabled, timerIsRunning || !timerStarted,
      TAG_END
      );

  // hours slider
  ng.ng_LeftEdge = 85;
  ng.ng_Width = window->Width - window->BorderLeft - window->BorderRight - ng.ng_LeftEdge + 4;
  ng.ng_TopEdge += 12;
  // The level is also displayed to the left of the slider by default.
  // We need to leave space for its rendering, which is done separately
  // from label rendering.
  ng.ng_GadgetText = "Hours:   ";
  ng.ng_Flags = PLACETEXT_LEFT;
  ng.ng_GadgetID = HOURS_SLIDER_ID;

  hourSlider = currentGadget = CreateGadget(
      SLIDER_KIND,
      currentGadget,
      &ng,
      GTSL_Min, 0,
      GTSL_Max, 23,
      GTSL_Level, uiHours,
      // You need both MaxLevelLen and LevelFormat for the label to display.
      GTSL_MaxLevelLen, 2,
      // The level is also a long, so use long number formattting.
      GTSL_LevelFormat, "%2ld",
      GA_Disabled, timerIsRunning,
      TAG_END
      );

  // minutes slider
  ng.ng_TopEdge += 12;
  ng.ng_GadgetText = "Mins:   ";
  ng.ng_GadgetID = MINUTES_SLIDER_ID;

  minuteSlider = currentGadget = CreateGadget(
      SLIDER_KIND,
      currentGadget,
      &ng,
      GTSL_Min, 0,
      GTSL_Max, 59,
      GTSL_Level, uiMinutes,
      GTSL_MaxLevelLen, 2,
      GTSL_LevelFormat, "%2ld",
      GA_Disabled, timerIsRunning,
      TAG_END
      );

  // seconds slider
  ng.ng_TopEdge += 12;
  ng.ng_GadgetText = "Secs:   ";
  ng.ng_GadgetID = SECONDS_SLIDER_ID;

  secondSlider = currentGadget = CreateGadget(
      SLIDER_KIND,
      currentGadget,
      &ng,
      GTSL_Min, 0,
      GTSL_Max, 59,
      GTSL_Level, uiSeconds,
      GTSL_MaxLevelLen, 2,
      GTSL_LevelFormat, "%2ld",
      GA_Disabled, timerIsRunning,
      TAG_END
      );

  return glist;
}

/**
 * Set the text of the timer and redraw the necessary gadgets.
 */
void setTimerText(void) {
  // Only change the timer widget text if the time is different
  // from the last render. This prevents unnecessary renders and potential
  // flashes of UI redraw.
  if (
      (priorHours != uiHours) ||
      (priorMinutes != uiMinutes) ||
      (priorSeconds != uiSeconds)
     ) {
    // _Technically_ this will change the label's contents all on its own,
    // but the newly-rendered label stomps on the old one without clearing
    // it out, so we need to force the full label redraw with GT_SetGadgetAttrs.
    sprintf(timerText, "%02d:%02d:%02d", uiHours, uiMinutes, uiSeconds);

    GT_SetGadgetAttrs(
      timerGadget,
      window,
      NULL,
      GTTX_Text, &timerText,
      TAG_DONE
    );

    priorHours = uiHours;
    priorMinutes = uiMinutes;
    priorSeconds = uiSeconds;
  }
}


/**
 * Ask the timer to send a message to our message port
 * after a defined number of milliseconds.
 */
int startTimer(void) {
  // TODO: handle timer.device not being available
  if (0 != (OpenDevice(TIMERNAME, UNIT_MICROHZ, (struct IORequest *)TimerIO, 0L))) {
    printf("Unable to open timer!");
    return 1;
  }

  TimerIO->tr_node.io_Command = TR_ADDREQUEST;
  TimerIO->tr_time.tv_secs = 0;
  TimerIO->tr_time.tv_micro = TIMER_INTERVAL;

  // SendIO is async, it doesn't wait for the IO to complete before continuing
  SendIO((struct IORequest *)TimerIO);

  CloseDevice((struct IORequest *)TimerIO);
}

/**
 * Render the UI.
 */
void renderUI(void) {
  windowGadgets = buildUI();

  // Use -1 for working with all gadgets.
  // You need to add, refresh, and refresh window when adding
  // GadTools gadgets.
  AddGList(window, windowGadgets, -1, -1, NULL);
  RefreshGList(windowGadgets, window, NULL, -1);
  setTimerText();
  GT_RefreshWindow(window, NULL);
}

/**
 * Clear the current UI.
 */
void clearUI(void) {
  RemoveGList(window, windowGadgets, -1);
  FreeGadgets(windowGadgets);
}

/**
 * Get the current system time.
 */
int getSysTime(void) {
  struct Device* TimerBase;

  if (0 != (OpenDevice(TIMERNAME, UNIT_MICROHZ, (struct IORequest *)TimerIO, 0L))) {
    printf("Unable to open timer!");
    return 1;
  }

  TimerBase = TimerIO->tr_node.io_Device;

  GetSysTime(&currentSystemTime);

  CloseDevice((struct IORequest *)TimerIO);

  return 0;
}

/**
 * Toggle the timer between started and stopped.
 */
void handleToggleTimer(void) {
  timerIsRunning = !timerIsRunning;

  if (timerIsRunning) {
    // TODO: handle timer.device not being available
    getSysTime();

    // timers are microsecond resolution
    timerStartTime = currentSystemTime.tv_secs * 1000000 + currentSystemTime.tv_micro;

    priorHours = NULL;
    priorMinutes = NULL;
    priorSeconds = NULL;

    originalUiHours = uiHours;
    originalUiMinutes = uiMinutes;
    originalUiSeconds = uiSeconds;

    timerStarted = TRUE;

    // start the timer
    startTimer();
  } else {
    // put the sliders back.
    // it causes a lot of UI flashing to update these as the timer runs,
    // so only do it once we stop the timer.
    GT_SetGadgetAttrs(
      hourSlider,
      window,
      NULL,
      GTSL_Level, uiHours,
      TAG_DONE
    );

    GT_SetGadgetAttrs(
      minuteSlider,
      window,
      NULL,
      GTSL_Level, uiMinutes,
      TAG_DONE
    );

    GT_SetGadgetAttrs(
      secondSlider,
      window,
      NULL,
      GTSL_Level, uiSeconds,
      TAG_DONE
    );
  }

  clearUI();
  renderUI();
}

/**
 * Reset the timer.
 */
void handleResetTimer(void) {
  uiHours = originalUiHours;
  uiMinutes = originalUiMinutes;
  uiSeconds = originalUiSeconds;

  timerStarted = FALSE;

  setTimerText();
  clearUI();
  renderUI();
}
//
// To keep this simple, the about window will block
int openAboutWindow(void) {
  struct Window *aboutWindow;
  struct NewGadget ng;
  struct Gadget *currentGadget;
  struct Gadget *glist;
  struct IntuiMessage *iMessage;

  ULONG windowSignal;
  BOOL closeAbout = FALSE;

  // Something is causing a small memory leak when I do this and I don't know
  // what it is. CodeWatcher reports a bunch of 40 byte blocks, most likely
  // Intuition messages.
  //
  // nope, false positive, checked with avail before and after running and
  // the used/free counts are exactly the same:
  // https://eab.abime.net/showthread.php?t=104360
  aboutWindow = OpenWindowTags(NULL,
    WA_Left, 40, WA_Top, 40,
    WA_Width, ABOUT_WINDOW_WIDTH, WA_Height, ABOUT_WINDOW_HEIGHT,
    WA_DetailPen, 0, WA_BlockPen, 1,
    WA_IDCMP, IDCMP_CLOSEWINDOW,
    WA_DragBar, TRUE,
    WA_DepthGadget, TRUE,
    WA_CloseGadget, TRUE,
    WA_Activate, TRUE,
    WA_Title, "About Pizza Timer",
    TAG_END
  );

  if (!aboutWindow) {
    return 1;
  }

  currentGadget = CreateContext(&glist);

  ng.ng_LeftEdge = WINDOW_CHROME_WIDTH + 4;
  ng.ng_TopEdge = 15;
  ng.ng_Height = 10;
  ng.ng_Width = 0;
  ng.ng_GadgetText = NULL;
  ng.ng_TextAttr = &Topaz80;
  ng.ng_VisualInfo = visualInfo;

  ng.ng_GadgetID = NULL;
  ng.ng_Flags = PLACETEXT_IN;

  currentGadget = CreateGadget(
    TEXT_KIND,
    currentGadget,
    &ng,
    GTTX_Text, "Topaz's Pizza Timer",
    GTTX_CopyText, TRUE,
    TAG_DONE
  );

  ng.ng_TopEdge += 10;
  currentGadget = CreateGadget(
    TEXT_KIND,
    currentGadget,
    &ng,
    GTTX_Text, "By John Bintz",
    GTTX_CopyText, TRUE,
    TAG_DONE
  );

  ng.ng_TopEdge += 10;
  currentGadget = CreateGadget(
    TEXT_KIND,
    currentGadget,
    &ng,
    GTTX_Text, "theindustriousrabbit.com",
    GTTX_CopyText, TRUE,
    TAG_DONE
  );

  ng.ng_TopEdge += 15;
  currentGadget = CreateGadget(
    TEXT_KIND,
    currentGadget,
    &ng,
    GTTX_Text, "Sound: Reception bell by cdrk (CC-BY 4.0)",
    GTTX_CopyText, TRUE,
    TAG_DONE
  );

  ng.ng_TopEdge += 10;
  currentGadget = CreateGadget(
    TEXT_KIND,
    currentGadget,
    &ng,
    GTTX_Text, "freesound.org/people/cdrk/sounds/264594/",
    GTTX_CopyText, TRUE,
    TAG_DONE
  );

  AddGList(aboutWindow, glist, -1, -1, NULL);
  RefreshGList(glist, aboutWindow, NULL, -1);
  GT_RefreshWindow(aboutWindow, NULL);

  windowSignal = 1L << aboutWindow->UserPort->mp_SigBit;

  while (!closeAbout) {
    Wait(windowSignal);

    while (iMessage = GT_GetIMsg(aboutWindow->UserPort)) {
      if (!closeAbout) {
        switch (iMessage->Class) {
          case IDCMP_CLOSEWINDOW:
            closeAbout = TRUE;
            break;
          case IDCMP_REFRESHWINDOW:
            GT_BeginRefresh(window);
            GT_EndRefresh(window, TRUE);
            break;
        }
      }

      // ensure messages are garbage collected
      GT_ReplyIMsg(iMessage);
    }
  }

  RemoveGList(aboutWindow, glist, -1);
  FreeGadgets(glist);
  CloseWindow(aboutWindow);

  return 0;
}

/**
 * Process a single Intuition message.
 */
void handleIntuitionMessage(struct IntuiMessage *iMessage) {
  struct Gadget *targetGadget;
  struct Menu *targetMenu;
  struct MenuData *menuData;

  BOOL rerenderTimer = FALSE;

  switch (iMessage->Class) {
    // We've released a button.
    case IDCMP_GADGETUP:
      targetGadget = (struct Gadget *)iMessage->IAddress;

      switch (targetGadget->GadgetID) {
        case START_STOP_BUTTON_ID:
          handleToggleTimer();

          break;
        case RESET_BUTTON_ID:
          handleResetTimer();
          rerenderTimer = TRUE;

          break;
      }
      break;

    // We picked a menu item.
    case IDCMP_MENUPICK:
      // https://en.wikibooks.org/wiki/Aros/Developer/Docs/Libraries/GadTools
      targetMenu = (struct Menu *)ItemAddress(menu, iMessage->Code);

      menuData = GTMENUITEM_USERDATA(targetMenu);

      switch (menuData->id) {
        // I originally tried to use MENU_QUIT.id here
        // https://stackoverflow.com/questions/14069737/switch-case-error-case-label-does-not-reduce-to-an-integer-constant
        // This is why there's a bunch more overhead for building
        // the menu userdata.
        case MENU_QUIT_ID:
          terminated = TRUE;
          break;
        case MENU_ABOUT_ID:
          openAboutWindowNext = TRUE;
          break;
      }
      break;

    // We've moved the mouse. In slider gadget talk, we've changed
    // the value of the slider.
    case IDCMP_MOUSEMOVE:
      targetGadget = (struct Gadget *)iMessage->IAddress;

      switch (targetGadget->GadgetID) {
        case HOURS_SLIDER_ID:
          uiHours = iMessage->Code;
          rerenderTimer = TRUE;
          break;
        case MINUTES_SLIDER_ID:
          uiMinutes = iMessage->Code;
          rerenderTimer = TRUE;
          break;
        case SECONDS_SLIDER_ID:
          uiSeconds = iMessage->Code;
          rerenderTimer = TRUE;
          break;
      }

      if (rerenderTimer) setTimerText();
      break;

    case IDCMP_CLOSEWINDOW:
      // bye bye
      terminated = TRUE;
      break;

      // this is required if your window is refreshable and you're using gadtools.
      // http://amigadev.elowar.com/read/ADCD_2.1/Libraries_Manual_guide/node026F.html
    case IDCMP_REFRESHWINDOW:
      GT_BeginRefresh(window);
      GT_EndRefresh(window, TRUE);
      break;
  }
}

struct dtTrigger myTrigger;

/**
 * Start playing a bell sound, then wait for it to finish.
 */
void startBellSound(void) {
  ULONG soundPlayResult;

  if (!DataTypesBase) return;
  // https://amigaworld.net/modules/newbb/viewtopic.php?forum=15&topic_id=39094&post_id=735120&viewmode=thread&order=0#735120

  // TODO: something in NewDTObject is causing a lock to be created that
  // CodeWatcher declares was not freed. Commenting this down to just
  // the GroupID tag does not make that warning go away. Each time this
  // is called, a new lock is created.
  //
  // CodeWatcher also seems to think this is being kept around in memory,
  // but running avail before and after getting the bell to ring indicate
  // otherwise.
  if (bellSound = NewDTObject(
        BELL_FILENAME,
        DTA_GroupID, GID_SOUND,
        // ourselves
        SDTA_SignalTask, (ULONG)FindTask(NULL),
        // ideally we should use this, but my headers aren't new enough?
        // SDTA_SignalBitNumber, waitForSoundSignalNumber,
        // so we'll do it this way
        SDTA_SignalBit, 1 << waitForSoundSignalNumber,
        TAG_END)) {
    myTrigger.MethodID = DTM_TRIGGER;
    myTrigger.dtt_GInfo = NULL;
    myTrigger.dtt_Function = STM_PLAY;
    myTrigger.dtt_Data = NULL;

    // https://github.com/khval/AmosKittens/blob/79f00ba3b81805b54fd4e437f667ea2eecab740d/OS/AmigaOS/animation.cpp#L128
    soundPlayResult = DoDTMethodA(bellSound, NULL, NULL, (Msg) &myTrigger);
  }
}

/**
 * Tear down the bell once the timer runs out.
 */
void waitForBellToFinish(void) {
  if (bellSound) {
    Wait(1 << waitForSoundSignalNumber);

    DisposeDTObject(bellSound);
  }
}

/**
 * Handle the timer running out of time.
 */
void endTimer(void) {
  startBellSound();
  DisplayBeep(screen);

  uiHours = uiMinutes = uiSeconds = 0;
  setTimerText();

  waitForBellToFinish();

  timerIsRunning = FALSE;
  timerStarted = FALSE;

  clearUI();
  renderUI();
}

void handleTimerMessage(void) {
  // TODO: handle timer.device not being available
  getSysTime();

  timerDistance = ((currentSystemTime.tv_secs * 1000000 + currentSystemTime.tv_micro) - timerStartTime) / 1000000;
  timerBuild = (originalUiHours * 3600 + originalUiMinutes * 60 + originalUiSeconds) - timerDistance;

  if (timerBuild <= 0) {
    endTimer();
  } else {
    uiHours = timerBuild / 3600;
    uiMinutes = timerBuild / 60 % 60;
    uiSeconds = timerBuild % 60;
    setTimerText();

    // this is like a setTimeout loop in JavaScript. keep re-running
    // the same timer until we don't need it anymore.
    startTimer();
  }
}

// https://wiki.amigaos.net/wiki/GadTools_Menus
void buildMenu(void) {
  menu = CreateMenus(
    appMenu, TAG_END
  );

  LayoutMenus(menu, visualInfo, TAG_END);
  SetMenuStrip(window, menu);
}

void clearMenu(void) {
  ClearMenuStrip(window);
  FreeMenus(menu);
}

int main() {
  struct IntuiMessage *iMessage;
  struct MsgPort *TimerPort;
  ULONG windowSignal, timerSignal, foundSignals;

  if (0 == setup()) {
    teardown();
    return 1;
  }

  // get our timer message port so we can await on timer events
  TimerPort = TimerIO->tr_node.io_Message.mn_ReplyPort;

  // business logic setup
  timerIsRunning = FALSE;

  // open the empty window
  window = OpenWindowTags(NULL,
    WA_Left, 20, WA_Top, 20,
    WA_Width, WINDOW_WIDTH, WA_Height, WINDOW_HEIGHT,
    WA_DetailPen, 0, WA_BlockPen, 1,
    WA_IDCMP, IDCMP_REFRESHWINDOW | IDCMP_CLOSEWINDOW | BUTTONIDCMP | SLIDERIDCMP | IDCMP_MENUPICK, // IDCMP flags
    WA_SmartRefresh, TRUE,
    WA_DragBar, TRUE,
    WA_DepthGadget, TRUE,
    WA_CloseGadget, TRUE,
    WA_Activate, TRUE,
    WA_Title, WINDOW_TITLE,
    TAG_END
  );

  if (!window) {
    teardown();
    return 1;
  }

  // http://amigadev.elowar.com/read/ADCD_2.1/Includes_and_Autodocs_3._guide/node03F8.html
  SetWindowTitles(window, (UBYTE *) ~0, "Topaz's Pizza Timer - theindustriousrabbit.com");
  buildMenu();

  // these create the bit mask for Wait() to listen to events on
  windowSignal = 1L << window->UserPort->mp_SigBit;
  timerSignal = 1L << TimerPort->mp_SigBit;

  renderUI();

  while (!terminated) {
    // http://amigadev.elowar.com/read/ADCD_2.1/Libraries_Manual_guide/node02EB.html
    // http://www.amigadev.elowar.com/read/ADCD_2.1/Includes_and_Autodocs_2._guide/node038A.html
    foundSignals = Wait(windowSignal | timerSignal);

    if (foundSignals & windowSignal) {
      // drain the window event queue
      while (iMessage = GT_GetIMsg(window->UserPort)) {
        if (!terminated) {
          handleIntuitionMessage(iMessage);
        }

        // if we don't reply, the event won't be garbage collected.
        // we still have to drain any other messages that show up
        GT_ReplyIMsg(iMessage);
      }
    }

    if ((foundSignals & timerSignal) && timerIsRunning) {
      handleTimerMessage();
    }

    // open up the about menu outside of event handling
    if (openAboutWindowNext) {
      if (openAboutWindow()) terminated = TRUE;

      openAboutWindowNext = FALSE;
    }
  }

  clearUI();
  clearMenu();
  CloseWindow(window);

  teardown();

  return 0;
}