// vim:fileencoding=utf-8:foldmethod=marker

#include "murmur3.h"
#include "hasher.h"
#include "../../../common/aliases/aliases.h"
#include "../../../common/assert/assert.h"
#include "../../../common/misc/misc_utils.h"
#include "../../../prng/xorshift/xorshift.h"

wp_intern inline void validateMur3HasherCtx(const WpHasherCtx *ctx);
wp_intern inline u64 fmix64(u64 k);

WpHasher wpX64Mur3Hasher(void) {
	WpXor256State state = wpPrngXorshiftInit();
	u32 seed            = (u32)wpPrngXorshift256(&state);
	return wpX64Mur3HasherWithSeed(seed);
}

WpHasher wpX64Mur3HasherWithSeed(u32 seed) {
	return (WpHasher){
		.func = wpX64Mur3GetHash128,
		.ctx  = (WpHasherCtx){
			.type    = WP_HASHER_CTX_MURMUR3,
			.murmur3 = seed,
		},
	};
}

WpU128 wpX64Mur3GetHash128(WpU8Stream *bytes, WpHasherCtx ctx) {
	validateMur3HasherCtx(&ctx);

	const i32 nblocks = (bytes->count * bytes->item_size) / 16;

	u64 h1 = ctx.murmur3;
	u64 h2 = ctx.murmur3;

	const u64 c1 = wpU64Const(0x87c37b91114253d5);
	const u64 c2 = wpU64Const(0x4cf5ad432745937f);

	//----------
	// body

	for(int i = 0; i < nblocks; ++i) {
		u64 k1 = *((u64 *)wpStreamConsumeCount(u8, bytes, sizeof(u64)));
		u64 k2 = *((u64 *)wpStreamConsumeCount(u8, bytes, sizeof(u64)));

		k1 *= c1;
		k1  = wpMiscUtilsRotl64(k1, 31);
		k1 *= c2;
		h1 ^= k1;

		h1  = wpMiscUtilsRotl64(h1, 27);
		h1 += h2;
		h1  = h1 * 5 +0x52dce729;

		k2 *= c2;
		k2  = wpMiscUtilsRotl64(k2, 33);
		k2 *= c1;
		h2 ^= k2;

		h2  = wpMiscUtilsRotl64(h2, 31);
		h2 += h1;
		h2  = h2*5+0x38495ab5;
	}

	//----------
	// tail

	const u8 *tail = wpStreamConsumeCount(u8, bytes, bytes->count - bytes->position);

	u64 k1 = 0;
	u64 k2 = 0;

	u64 len = bytes->count * bytes->item_size;

	switch(len & 15) {
		case 15: k2 ^= ((u64)tail[14]) << 48;
		case 14: k2 ^= ((u64)tail[13]) << 40;
		case 13: k2 ^= ((u64)tail[12]) << 32;
		case 12: k2 ^= ((u64)tail[11]) << 24;
		case 11: k2 ^= ((u64)tail[10]) << 16;
		case 10: k2 ^= ((u64)tail[ 9]) << 8;
		case  9: k2 ^= ((u64)tail[ 8]) << 0;
		         k2 *= c2; k2  = wpMiscUtilsRotl64(k2,33); k2 *= c1; h2 ^= k2;

		case  8: k1 ^= ((u64)tail[ 7]) << 56;
		case  7: k1 ^= ((u64)tail[ 6]) << 48;
		case  6: k1 ^= ((u64)tail[ 5]) << 40;
		case  5: k1 ^= ((u64)tail[ 4]) << 32;
		case  4: k1 ^= ((u64)tail[ 3]) << 24;
		case  3: k1 ^= ((u64)tail[ 2]) << 16;
		case  2: k1 ^= ((u64)tail[ 1]) << 8;
		case  1: k1 ^= ((u64)tail[ 0]) << 0;
		         k1 *= c1; k1  = wpMiscUtilsRotl64(k1,31); k1 *= c2; h1 ^= k1;
	};

	//----------
	// finalization

	h1 ^= len; h2 ^= len;

	h1 += h2;
	h2 += h1;

	h1 = fmix64(h1);
	h2 = fmix64(h2);

	h1 += h2;
	h2 += h1;

	return (WpU128){ .value = { [0] = h1, [1] = h2 } };
}

wp_intern inline void validateMur3HasherCtx(const WpHasherCtx *ctx) {
	wpRuntimeAssert(ctx->type == WP_HASHER_CTX_MURMUR3, "Invalid Murmur3 hash context");
}

wp_intern inline u64 fmix64(u64 k) {
	k ^= k >> 33;
	k *= wpU64Const(0xff51afd7ed558ccd);
	k ^= k >> 33;
	k *= wpU64Const(0xc4ceb9fe1a85ec53);
	k ^= k >> 33;

	return k;
}