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import std.bigint;
import std.digest.crc;
import std.random : unpredictableSeed;
import std.range;
import lru : LRUCache;
import deimos.ncurses;
private BigInt positive(BigInt n)
{
if (n >= 0)
return n * 2;
else
return -n * 2 - 1;
}
private BigInt pair(BigInt n, BigInt m)
{
// https://stackoverflow.com/a/919661
return (positive(n) + positive(m)) * (positive(n) + positive(m) + 1) / 2 + positive(m);
}
struct Spot
{
private char _contents;
this(char c)
{
_contents = c;
}
@property contents()
{
return _contents;
}
bool opEqual(const Spot s)
{
return s._contents == _contents;
}
bool isRock()
{
return _contents == '*';
}
}
interface SpotSource
{
Spot opIndex(BigInt y, BigInt x);
}
class RandomSource : SpotSource
{
uint seed;
double density = .0025;
private LRUCache!(BigInt[2], Spot) cache;
this()
{
seed = unpredictableSeed;
cache = new LRUCache!(BigInt[2], Spot)(50000);
}
this(uint seed)
{
this.seed = seed;
}
this(uint seed, double density)
{
this.density = density;
this(seed);
}
private uint hash(BigInt n)
{
CRC32 crc;
crc.start();
crc.put((cast(ubyte*)&seed)[0 .. seed.sizeof]);
foreach (i; iota(n.ulongLength))
{
auto digit = n.getDigit(i);
crc.put((cast(ubyte*)&digit)[0 .. digit.sizeof]);
}
auto result = crc.finish();
auto hash = *(cast(uint*)&result);
return hash;
}
public Spot opIndex(BigInt y, BigInt x)
{
if ([y, x] in cache)
return cache[[y, x]];
auto roll = cast(double) hash(pair(y, x)) / uint.max;
Spot ret;
if (roll < density)
ret = Spot('*');
else
ret = Spot(' ');
cache[[y, x]] = ret;
return ret;
}
}
class OverlaySource : SpotSource
{
private SpotSource _base;
private Spot[BigInt[2]] _overlay;
this(SpotSource base)
{
_base = base;
}
void opIndexAssign(Spot spot, BigInt y, BigInt x)
{
Spot* p = [y, x] in _overlay;
if (p !is null && spot == _base[y, x])
{
_overlay.remove([y, x]);
}
else
{
_overlay[[y, x]] = spot;
}
}
Spot opIndex(BigInt y, BigInt x)
{
Spot* p = [y, x] in _overlay;
if (p !is null)
return *p;
else
return _base[y, x];
}
unittest
{
auto base = new RandomSource(0, 0.0);
auto src = new OverlaySource(base);
src[BigInt(0), BigInt(0)] = Spot('*');
src[BigInt(0), BigInt(1)] = Spot('*');
assert(src[BigInt(0), BigInt(0)] == Spot('*'));
assert(src[BigInt(0), BigInt(1)] == Spot('*'));
}
}
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