#include <AppKit/AppKit.h>

static char tab2[6] = { 'a', 'b', 'c', 'd', '0', '?' };
static NSButton *tab1[sizeof(tab2)];

static char name_of(id v)
{
  int i;
  tab1[sizeof(tab2) - 1] = v;

  for (i = 0; ; ++i)
    if (tab1[i] == v)
      return tab2[i];
}

static void vkv(NSButton *v)
{
  NSButton *nv = [v nextValidKeyView];
  NSButton *pv = [v previousValidKeyView];
  NSLog(@"valid key views: %c <- %c(%d) -> %c",
    name_of(pv), name_of(v), [v acceptsFirstResponder], name_of(nv));
  if (nv && ![nv isEnabled])
    NSLog(@"next valid key view is disabled?");
  if (pv && ![pv isEnabled])
    NSLog(@"previous valid key view is disabled?");
}

static void enb(NSButton *v, BOOL f)
{
  NSLog(@"%@able: %c", (f ? @"en" : @"dis"), name_of(v));
  [v setEnabled:f];
}

int main(int argc, char *argv[])
{
  CREATE_AUTORELEASE_POOL(pool);
  NSButton *a = tab1[0] = [NSButton new];
  NSButton *b = tab1[1] = [NSButton new];
  NSButton *c = tab1[2] = [NSButton new];
  NSButton *d = tab1[3] = [NSButton new];

  [a setNextKeyView:b];
  [a setNextKeyView:c];
  [b setNextKeyView:d];
  [c setNextKeyView:d];
  [d setNextKeyView:a];
  enb(b, YES); enb(c, YES);
  vkv(a); vkv(b); vkv(c); vkv(d);
  enb(b, YES); enb(c, NO);
  vkv(a); vkv(b); vkv(c); vkv(d);
  enb(b, NO); enb(c, YES);
  vkv(a); vkv(b); vkv(c); vkv(d);
  enb(b, NO); enb(c, NO);
  vkv(a); vkv(b); vkv(c); vkv(d);
  enb(a, NO); enb(d, NO);
  NSLog(@"is your program caught in an infinite loop?");
  vkv(a); vkv(b); vkv(c); vkv(d);
  NSLog(@"This is the end.");
  RELEASE(pool);
  return 0;
}