text: /*
  * Copyright (c) 2021 Calvin Rose
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to
  * deal in the Software without restriction, including without limitation the
  * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
  * sell copies of the Software, and to permit persons to whom the Software is
  * furnished to do so, subject to the following conditions:
  *
  * The above copyright notice and this permission notice shall be included in
  * all copies or substantial portions of the Software.
  *
  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  * IN THE SOFTWARE.
  */
  
  #ifndef JANET_AMALG
  #include "features.h"
  #include <janet.h>
  #include "state.h"
  #include "util.h"
  #endif
  
  #include <math.h>
  
  static int janet_rng_get(void *p, Janet key, Janet *out);
  static Janet janet_rng_next(void *p, Janet key);
  
  static void janet_rng_marshal(void *p, JanetMarshalContext *ctx) {
      JanetRNG *rng = (JanetRNG *)p;
      janet_marshal_abstract(ctx, p);
      janet_marshal_int(ctx, (int32_t) rng->a);
      janet_marshal_int(ctx, (int32_t) rng->b);
      janet_marshal_int(ctx, (int32_t) rng->c);
      janet_marshal_int(ctx, (int32_t) rng->d);
      janet_marshal_int(ctx, (int32_t) rng->counter);
  }
  
  static void *janet_rng_unmarshal(JanetMarshalContext *ctx) {
      JanetRNG *rng = janet_unmarshal_abstract(ctx, sizeof(JanetRNG));
      rng->a = (uint32_t) janet_unmarshal_int(ctx);
      rng->b = (uint32_t) janet_unmarshal_int(ctx);
      rng->c = (uint32_t) janet_unmarshal_int(ctx);
      rng->d = (uint32_t) janet_unmarshal_int(ctx);
      rng->counter = (uint32_t) janet_unmarshal_int(ctx);
      return rng;
  }
  
  const JanetAbstractType janet_rng_type = {
      "core/rng",
      NULL,
      NULL,
      janet_rng_get,
      NULL,
      janet_rng_marshal,
      janet_rng_unmarshal,
      NULL, /* tostring */
      NULL, /* compare */
      NULL, /* hash */
      janet_rng_next,
      JANET_ATEND_NEXT
  };
  
  JanetRNG *janet_default_rng(void) {
      return &janet_vm.rng;
  }
  
  void janet_rng_seed(JanetRNG *rng, uint32_t seed) {
      rng->a = seed;
      rng->b = 0x97654321u;
      rng->c = 123871873u;
      rng->d = 0xf23f56c8u;
      rng->counter = 0u;
      /* First several numbers aren't that random. */
      for (int i = 0; i < 16; i++) janet_rng_u32(rng);
  }
  
  void janet_rng_longseed(JanetRNG *rng, const uint8_t *bytes, int32_t len) {
      uint8_t state[16] = {0};
      for (int32_t i = 0; i < len; i++)
          state[i & 0xF] ^= bytes[i];
      rng->a = state[0] + (state[1] << 8) + (state[2] << 16) + (state[3] << 24);
      rng->b = state[4] + (state[5] << 8) + (state[6] << 16) + (state[7] << 24);
      rng->c = state[8] + (state[9] << 8) + (state[10] << 16) + (state[11] << 24);
      rng->d = state[12] + (state[13] << 8) + (state[14] << 16) + (state[15] << 24);
      rng->counter = 0u;
      /* a, b, c, d can't all be 0 */
      if (rng->a == 0) rng->a = 1u;
      for (int i = 0; i < 16; i++) janet_rng_u32(rng);
  }
  
  uint32_t janet_rng_u32(JanetRNG *rng) {
      /* Algorithm "xorwow" from p. 5 of Marsaglia, "Xorshift RNGs" */
      uint32_t t = rng->d;
      uint32_t const s = rng->a;
      rng->d = rng->c;
      rng->c = rng->b;
      rng->b = s;
      t ^= t >> 2;
      t ^= t << 1;
      t ^= s ^ (s << 4);
      rng->a = t;
      rng->counter += 362437;
      return t + rng->counter;
  }
  
  double janet_rng_double(JanetRNG *rng) {
      uint32_t hi = janet_rng_u32(rng);
      uint32_t lo = janet_rng_u32(rng);
      uint64_t big = (uint64_t)(lo) | (((uint64_t) hi) << 32);
      return ldexp((double)(big >> (64 - 52)), -52);
  }
  
  JANET_CORE_FN(cfun_rng_make,
                "(math/rng &opt seed)",
                "Creates a Psuedo-Random number generator, with an optional seed. "
                "The seed should be an unsigned 32 bit integer or a buffer. "
                "Do not use this for cryptography. Returns a core/rng abstract type."
               ) {
      janet_arity(argc, 0, 1);
      JanetRNG *rng = janet_abstract(&janet_rng_type, sizeof(JanetRNG));
      if (argc == 1) {
          if (janet_checkint(argv[0])) {
              uint32_t seed = (uint32_t)(janet_getinteger(argv, 0));
              janet_rng_seed(rng, seed);
          } else {
              JanetByteView bytes = janet_getbytes(argv, 0);
              janet_rng_longseed(rng, bytes.bytes, bytes.len);
          }
      } else {
          janet_rng_seed(rng, 0);
      }
      return janet_wrap_abstract(rng);
  }
  
  JANET_CORE_FN(cfun_rng_uniform,
                "(math/rng-uniform rng)",
                "Extract a random number in the range [0, 1) from the RNG."
               ) {
      janet_fixarity(argc, 1);
      JanetRNG *rng = janet_getabstract(argv, 0, &janet_rng_type);
      return janet_wrap_number(janet_rng_double(rng));
  }
  
  JANET_CORE_FN(cfun_rng_int,
                "(math/rng-int rng &opt max)",
                "Extract a random random integer in the range [0, max] from the RNG. If "
                "no max is given, the default is 2^31 - 1."
               ) {
      janet_arity(argc, 1, 2);
      JanetRNG *rng = janet_getabstract(argv, 0, &janet_rng_type);
      if (argc == 1) {
          uint32_t word = janet_rng_u32(rng) >> 1;
          return janet_wrap_integer(word);
      } else {
          int32_t max = janet_optnat(argv, argc, 1, INT32_MAX);
          if (max == 0) return janet_wrap_number(0.0);
          uint32_t modulo = (uint32_t) max;
          uint32_t maxgen = INT32_MAX;
          uint32_t maxword = maxgen - (maxgen % modulo);
          uint32_t word;
          do {
              word = janet_rng_u32(rng) >> 1;
          } while (word > maxword);
          return janet_wrap_integer(word % modulo);
      }
  }
  
  static void rng_get_4bytes(JanetRNG *rng, uint8_t *buf) {
      uint32_t word = janet_rng_u32(rng);
      buf[0] = word & 0xFF;
      buf[1] = (word >> 8) & 0xFF;
      buf[2] = (word >> 16) & 0xFF;
      buf[3] = (word >> 24) & 0xFF;
  }
  
  JANET_CORE_FN(cfun_rng_buffer,
                "(math/rng-buffer rng n &opt buf)",
                "Get n random bytes and put them in a buffer. Creates a new buffer if no buffer is "
                "provided, otherwise appends to the given buffer. Returns the buffer."
               ) {
      janet_arity(argc, 2, 3);
      JanetRNG *rng = janet_getabstract(argv, 0, &janet_rng_type);
      int32_t n = janet_getnat(argv, 1);
      JanetBuffer *buffer = janet_optbuffer(argv, argc, 2, n);
  
      /* Split into first part (that is divisible by 4), and rest */
      int32_t first_part = n & ~3;
      int32_t second_part = n - first_part;
  
      /* Get first part in chunks of 4 bytes */
      janet_buffer_extra(buffer, n);
      uint8_t *buf = buffer->data + buffer->count;
      for (int32_t i = 0; i < first_part; i += 4) rng_get_4bytes(rng, buf + i);
      buffer->count += first_part;
  
      /* Get remaining 0 - 3 bytes */
      if (second_part) {
          uint8_t wordbuf[4] = {0};
          rng_get_4bytes(rng, wordbuf);
          janet_buffer_push_bytes(buffer, wordbuf, second_part);
      }
  
      return janet_wrap_buffer(buffer);
  }
  
  static const JanetMethod rng_methods[] = {
      {"uniform", cfun_rng_uniform},
      {"int", cfun_rng_int},
      {"buffer", cfun_rng_buffer},
      {NULL, NULL}
  };
  
  static int janet_rng_get(void *p, Janet key, Janet *out) {
      (void) p;
      if (!janet_checktype(key, JANET_KEYWORD)) return 0;
      return janet_getmethod(janet_unwrap_keyword(key), rng_methods, out);
  }
  
  static Janet janet_rng_next(void *p, Janet key) {
      (void) p;
      return janet_nextmethod(rng_methods, key);
  }
  
  /* Get a random number */
  JANET_CORE_FN(janet_rand,
                "(math/random)",
                "Returns a uniformly distributed random number between 0 and 1") {
      (void) argv;
      janet_fixarity(argc, 0);
      return janet_wrap_number(janet_rng_double(&janet_vm.rng));
  }
  
  /* Seed the random number generator */
  JANET_CORE_FN(janet_srand,
                "(math/seedrandom seed)",
                "Set the seed for the random number generator. seed should be "
                "an integer or a buffer."
               ) {
      janet_fixarity(argc, 1);
      if (janet_checkint(argv[0])) {
          uint32_t seed = (uint32_t)(janet_getinteger(argv, 0));
          janet_rng_seed(&janet_vm.rng, seed);
      } else {
          JanetByteView bytes = janet_getbytes(argv, 0);
          janet_rng_longseed(&janet_vm.rng, bytes.bytes, bytes.len);
      }
      return janet_wrap_nil();
  }
  
  #define JANET_DEFINE_MATHOP(name, fop, doc)\
  JANET_CORE_FN(janet_##name, "(math/" #name " x)", doc) {\
      janet_fixarity(argc, 1); \
      double x = janet_getnumber(argv, 0); \
      return janet_wrap_number(fop(x)); \
  }
  
  JANET_DEFINE_MATHOP(acos, acos, "Returns the arccosize of x.")
  JANET_DEFINE_MATHOP(asin, asin, "Returns the arcsin of x.")
  JANET_DEFINE_MATHOP(atan, atan, "Returns the arctangent of x.")
  JANET_DEFINE_MATHOP(cos, cos, "Returns the cosine of x.")
  JANET_DEFINE_MATHOP(cosh, cosh, "Returns the hyperbolic cosine of x.")
  JANET_DEFINE_MATHOP(acosh, acosh, "Returns the hyperbolic arccosine of x.")
  JANET_DEFINE_MATHOP(sin, sin, "Returns the sine of x.")
  JANET_DEFINE_MATHOP(sinh, sinh, "Returns the hyperbolic sine of x.")
  JANET_DEFINE_MATHOP(asinh, asinh, "Returns the hypberbolic arcsine of x.")
  JANET_DEFINE_MATHOP(tan, tan, "Returns the tangent of x.")
  JANET_DEFINE_MATHOP(tanh, tanh, "Returns the hyperbolic tangent of x.")
  JANET_DEFINE_MATHOP(atanh, atanh, "Returns the hyperbolic arctangent of x.")
  JANET_DEFINE_MATHOP(exp, exp, "Returns e to the power of x.")
  JANET_DEFINE_MATHOP(exp2, exp2, "Returns 2 to the power of x.")
  JANET_DEFINE_MATHOP(expm1, expm1, "Returns e to the power of x minus 1.")
  JANET_DEFINE_MATHOP(log, log, "Returns the natural logarithm of x.")
  JANET_DEFINE_MATHOP(log10, log10, "Returns the log base 10 of x.")
  JANET_DEFINE_MATHOP(log2, log2, "Returns the log base 2 of x.")
  JANET_DEFINE_MATHOP(sqrt, sqrt, "Returns the square root of x.")
  JANET_DEFINE_MATHOP(cbrt, cbrt, "Returns the cube root of x.")
  JANET_DEFINE_MATHOP(ceil, ceil, "Returns the smallest integer value number that is not less than x.")
  JANET_DEFINE_MATHOP(fabs, fabs, "Return the absolute value of x.")
  JANET_DEFINE_MATHOP(floor, floor, "Returns the largest integer value number that is not greater than x.")
  JANET_DEFINE_MATHOP(trunc, trunc, "Returns the integer between x and 0 nearest to x.")
  JANET_DEFINE_MATHOP(round, round, "Returns the integer nearest to x.")
  JANET_DEFINE_MATHOP(gamma, lgamma, "Returns gamma(x).")
  JANET_DEFINE_MATHOP(log1p, log1p, "Returns (log base e of x) + 1 more accurately than (+ (math/log x) 1)")
  JANET_DEFINE_MATHOP(erf, erf, "Returns the error function of x.")
  JANET_DEFINE_MATHOP(erfc, erfc, "Returns the complementary error function of x.")
  
  #define JANET_DEFINE_MATH2OP(name, fop, signature, doc)\
  JANET_CORE_FN(janet_##name, signature, doc) {\
      janet_fixarity(argc, 2); \
      double lhs = janet_getnumber(argv, 0); \
      double rhs = janet_getnumber(argv, 1); \
      return janet_wrap_number(fop(lhs, rhs)); \
  }
  
  JANET_DEFINE_MATH2OP(atan2, atan2, "(math/atan2 y x)", "Returns the arctangent of y/x. Works even when x is 0.")
  JANET_DEFINE_MATH2OP(pow, pow, "(math/pow a x)", "Returns a to the power of x.")
  JANET_DEFINE_MATH2OP(hypot, hypot, "(math/hypot a b)", "Returns c from the equation c^2 = a^2 + b^2.")
  JANET_DEFINE_MATH2OP(nextafter, nextafter,  "(math/next x y)", "Returns the next representable floating point vaue after x in the direction of y.")
  
  JANET_CORE_FN(janet_not, "(not x)", "Returns the boolean inverse of x.") {
      janet_fixarity(argc, 1);
      return janet_wrap_boolean(!janet_truthy(argv[0]));
  }
  
  
  /* Module entry point */
  void janet_lib_math(JanetTable *env) {
      JanetRegExt math_cfuns[] = {
          JANET_CORE_REG("not", janet_not),
          JANET_CORE_REG("math/random", janet_rand),
          JANET_CORE_REG("math/seedrandom", janet_srand),
          JANET_CORE_REG("math/cos", janet_cos),
          JANET_CORE_REG("math/sin", janet_sin),
          JANET_CORE_REG("math/tan", janet_tan),
          JANET_CORE_REG("math/acos", janet_acos),
          JANET_CORE_REG("math/asin", janet_asin),
          JANET_CORE_REG("math/atan", janet_atan),
          JANET_CORE_REG("math/exp", janet_exp),
          JANET_CORE_REG("math/log", janet_log),
          JANET_CORE_REG("math/log10", janet_log10),
          JANET_CORE_REG("math/log2", janet_log2),
          JANET_CORE_REG("math/sqrt", janet_sqrt),
          JANET_CORE_REG("math/cbrt", janet_cbrt),
          JANET_CORE_REG("math/floor", janet_floor),
          JANET_CORE_REG("math/ceil", janet_ceil),
          JANET_CORE_REG("math/pow", janet_pow),
          JANET_CORE_REG("math/abs", janet_fabs),
          JANET_CORE_REG("math/sinh", janet_sinh),
          JANET_CORE_REG("math/cosh", janet_cosh),
          JANET_CORE_REG("math/tanh", janet_tanh),
          JANET_CORE_REG("math/atanh", janet_atanh),
          JANET_CORE_REG("math/asinh", janet_asinh),
          JANET_CORE_REG("math/acosh", janet_acosh),
          JANET_CORE_REG("math/atan2", janet_atan2),
          JANET_CORE_REG("math/rng", cfun_rng_make),
          JANET_CORE_REG("math/rng-uniform", cfun_rng_uniform),
          JANET_CORE_REG("math/rng-int", cfun_rng_int),
          JANET_CORE_REG("math/rng-buffer", cfun_rng_buffer),
          JANET_CORE_REG("math/hypot", janet_hypot),
          JANET_CORE_REG("math/exp2", janet_exp2),
          JANET_CORE_REG("math/log1p", janet_log1p),
          JANET_CORE_REG("math/gamma", janet_gamma),
          JANET_CORE_REG("math/erfc", janet_erfc),
          JANET_CORE_REG("math/erf", janet_erf),
          JANET_CORE_REG("math/expm1", janet_expm1),
          JANET_CORE_REG("math/trunc", janet_trunc),
          JANET_CORE_REG("math/round", janet_round),
          JANET_CORE_REG("math/next", janet_nextafter),
          JANET_REG_END
      };
      janet_core_cfuns_ext(env, NULL, math_cfuns);
      janet_register_abstract_type(&janet_rng_type);
  #ifdef JANET_BOOTSTRAP
      JANET_CORE_DEF(env, "math/pi", janet_wrap_number(3.1415926535897931),
                     "The value pi.");
      JANET_CORE_DEF(env, "math/e", janet_wrap_number(2.7182818284590451),
                     "The base of the natural log.");
      JANET_CORE_DEF(env, "math/inf", janet_wrap_number(INFINITY),
                     "The number representing positive infinity");
      JANET_CORE_DEF(env, "math/-inf", janet_wrap_number(-INFINITY),
                     "The number representing negative infinity");
      JANET_CORE_DEF(env, "math/int32-min", janet_wrap_number(INT32_MIN),
                     "The minimum contiguous integer representable by a 32 bit signed integer");
      JANET_CORE_DEF(env, "math/int32-max", janet_wrap_number(INT32_MAX),
                     "The maximum contiguous integer represtenable by a 32 bit signed integer");
      JANET_CORE_DEF(env, "math/int-min", janet_wrap_number(JANET_INTMIN_DOUBLE),
                     "The minimum contiguous integer representable by a double (2^53)");
      JANET_CORE_DEF(env, "math/int-max", janet_wrap_number(JANET_INTMAX_DOUBLE),
                     "The maximum contiguous integer represtenable by a double (-(2^53))");
  #ifdef NAN
      JANET_CORE_DEF(env, "math/nan", janet_wrap_number(NAN), "Not a number (IEEE-754 NaN)");
  #else
      JANET_CORE_DEF(env, "math/nan", janet_wrap_number(0.0 / 0.0), "Not a number (IEEE-754 NaN)");
  #endif
  #endif
  }
  