/*
   * This file is part of the MicroPython project, http://micropython.org/
   *
   * The MIT License (MIT)
   *
   * Copyright (c) 2016 Paul Sokolovsky
   *
   * 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.
   */
  
  #include <assert.h>
  #include <string.h>
  
  #include "py/runtime.h"
  
  #if MICROPY_PY_URANDOM
  
  // Yasmarang random number generator
  // by Ilya Levin
  // http://www.literatecode.com/yasmarang
  // Public Domain
  
  STATIC uint32_t yasmarang_pad = 0xeda4baba, yasmarang_n = 69, yasmarang_d = 233;
  STATIC uint8_t yasmarang_dat = 0;
  
  STATIC uint32_t yasmarang(void)
  {
     yasmarang_pad += yasmarang_dat + yasmarang_d * yasmarang_n;
     yasmarang_pad = (yasmarang_pad<<3) + (yasmarang_pad>>29);
     yasmarang_n = yasmarang_pad | 2;
     yasmarang_d ^= (yasmarang_pad<<31) + (yasmarang_pad>>1);
     yasmarang_dat ^= (char) yasmarang_pad ^ (yasmarang_d>>8) ^ 1;
  
     return (yasmarang_pad^(yasmarang_d<<5)^(yasmarang_pad>>18)^(yasmarang_dat<<1));
  }  /* yasmarang */
  
  // End of Yasmarang
  
  #if MICROPY_PY_URANDOM_EXTRA_FUNCS
  
  // returns an unsigned integer below the given argument
  // n must not be zero
  STATIC uint32_t yasmarang_randbelow(uint32_t n) {
      uint32_t mask = 1;
      while ((n & mask) < n) {
          mask = (mask << 1) | 1;
      }
      uint32_t r;
      do {
          r = yasmarang() & mask;
      } while (r >= n);
      return r;
  }
  
  #endif
  
  STATIC mp_obj_t mod_urandom_getrandbits(mp_obj_t num_in) {
      int n = mp_obj_get_int(num_in);
      if (n > 32 || n == 0) {
          mp_raise_ValueError(NULL);
      }
      uint32_t mask = ~0;
      // Beware of C undefined behavior when shifting by >= than bit size
      mask >>= (32 - n);
      return mp_obj_new_int_from_uint(yasmarang() & mask);
  }
  STATIC MP_DEFINE_CONST_FUN_OBJ_1(mod_urandom_getrandbits_obj, mod_urandom_getrandbits);
  
  STATIC mp_obj_t mod_urandom_seed(mp_obj_t seed_in) {
      mp_uint_t seed = mp_obj_get_int_truncated(seed_in);
      yasmarang_pad = seed;
      yasmarang_n = 69;
      yasmarang_d = 233;
      yasmarang_dat = 0;
      return mp_const_none;
  }
  STATIC MP_DEFINE_CONST_FUN_OBJ_1(mod_urandom_seed_obj, mod_urandom_seed);
  
  #if MICROPY_PY_URANDOM_EXTRA_FUNCS
  
  STATIC mp_obj_t mod_urandom_randrange(size_t n_args, const mp_obj_t *args) {
      mp_int_t start = mp_obj_get_int(args[0]);
      if (n_args == 1) {
          // range(stop)
          if (start > 0) {
              return mp_obj_new_int(yasmarang_randbelow(start));
          } else {
              goto error;
          }
      } else {
          mp_int_t stop = mp_obj_get_int(args[1]);
          if (n_args == 2) {
              // range(start, stop)
              if (start < stop) {
                  return mp_obj_new_int(start + yasmarang_randbelow(stop - start));
              } else {
                  goto error;
              }
          } else {
              // range(start, stop, step)
              mp_int_t step = mp_obj_get_int(args[2]);
              mp_int_t n;
              if (step > 0) {
                  n = (stop - start + step - 1) / step;
              } else if (step < 0) {
                  n = (stop - start + step + 1) / step;
              } else {
                  goto error;
              }
              if (n > 0) {
                  return mp_obj_new_int(start + step * yasmarang_randbelow(n));
              } else {
                  goto error;
              }
          }
      }
  
  error:
      mp_raise_ValueError(NULL);
  }
  STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mod_urandom_randrange_obj, 1, 3, mod_urandom_randrange);
  
  STATIC mp_obj_t mod_urandom_randint(mp_obj_t a_in, mp_obj_t b_in) {
      mp_int_t a = mp_obj_get_int(a_in);
      mp_int_t b = mp_obj_get_int(b_in);
      if (a <= b) {
          return mp_obj_new_int(a + yasmarang_randbelow(b - a + 1));
      } else {
          mp_raise_ValueError(NULL);
      }
  }
  STATIC MP_DEFINE_CONST_FUN_OBJ_2(mod_urandom_randint_obj, mod_urandom_randint);
  
  STATIC mp_obj_t mod_urandom_choice(mp_obj_t seq) {
      mp_int_t len = mp_obj_get_int(mp_obj_len(seq));
      if (len > 0) {
          return mp_obj_subscr(seq, mp_obj_new_int(yasmarang_randbelow(len)), MP_OBJ_SENTINEL);
      } else {
          nlr_raise(mp_obj_new_exception(&mp_type_IndexError));
      }
  }
  STATIC MP_DEFINE_CONST_FUN_OBJ_1(mod_urandom_choice_obj, mod_urandom_choice);
  
  #if MICROPY_PY_BUILTINS_FLOAT
  
  // returns a number in the range [0..1) using Yasmarang to fill in the fraction bits
  STATIC mp_float_t yasmarang_float(void) {
      #if MICROPY_FLOAT_IMPL == MICROPY_FLOAT_IMPL_DOUBLE
      typedef uint64_t mp_float_int_t;
      #elif MICROPY_FLOAT_IMPL == MICROPY_FLOAT_IMPL_FLOAT
      typedef uint32_t mp_float_int_t;
      #endif
      union {
          mp_float_t f;
          #if MP_ENDIANNESS_LITTLE
          struct { mp_float_int_t frc:MP_FLOAT_FRAC_BITS, exp:MP_FLOAT_EXP_BITS, sgn:1; } p;
          #else
          struct { mp_float_int_t sgn:1, exp:MP_FLOAT_EXP_BITS, frc:MP_FLOAT_FRAC_BITS; } p;
          #endif
      } u;
      u.p.sgn = 0;
      u.p.exp = (1 << (MP_FLOAT_EXP_BITS - 1)) - 1;
      if (MP_FLOAT_FRAC_BITS <= 32) {
          u.p.frc = yasmarang();
      } else {
          u.p.frc = ((uint64_t)yasmarang() << 32) | (uint64_t)yasmarang();
      }
      return u.f - 1;
  }
  
  STATIC mp_obj_t mod_urandom_random(void) {
      return mp_obj_new_float(yasmarang_float());
  }
  STATIC MP_DEFINE_CONST_FUN_OBJ_0(mod_urandom_random_obj, mod_urandom_random);
  
  STATIC mp_obj_t mod_urandom_uniform(mp_obj_t a_in, mp_obj_t b_in) {
      mp_float_t a = mp_obj_get_float(a_in);
      mp_float_t b = mp_obj_get_float(b_in);
      return mp_obj_new_float(a + (b - a) * yasmarang_float());
  }
  STATIC MP_DEFINE_CONST_FUN_OBJ_2(mod_urandom_uniform_obj, mod_urandom_uniform);
  
  #endif
  
  #endif // MICROPY_PY_URANDOM_EXTRA_FUNCS
  
  STATIC const mp_rom_map_elem_t mp_module_urandom_globals_table[] = {
      { MP_ROM_QSTR(MP_QSTR___name__), MP_ROM_QSTR(MP_QSTR_urandom) },
      { MP_ROM_QSTR(MP_QSTR_getrandbits), MP_ROM_PTR(&mod_urandom_getrandbits_obj) },
      { MP_ROM_QSTR(MP_QSTR_seed), MP_ROM_PTR(&mod_urandom_seed_obj) },
      #if MICROPY_PY_URANDOM_EXTRA_FUNCS
      { MP_ROM_QSTR(MP_QSTR_randrange), MP_ROM_PTR(&mod_urandom_randrange_obj) },
      { MP_ROM_QSTR(MP_QSTR_randint), MP_ROM_PTR(&mod_urandom_randint_obj) },
      { MP_ROM_QSTR(MP_QSTR_choice), MP_ROM_PTR(&mod_urandom_choice_obj) },
      #if MICROPY_PY_BUILTINS_FLOAT
      { MP_ROM_QSTR(MP_QSTR_random), MP_ROM_PTR(&mod_urandom_random_obj) },
      { MP_ROM_QSTR(MP_QSTR_uniform), MP_ROM_PTR(&mod_urandom_uniform_obj) },
      #endif
      #endif
  };
  
  STATIC MP_DEFINE_CONST_DICT(mp_module_urandom_globals, mp_module_urandom_globals_table);
  
  const mp_obj_module_t mp_module_urandom = {
      .base = { &mp_type_module },
      .globals = (mp_obj_dict_t*)&mp_module_urandom_globals,
  };
  
  #endif //MICROPY_PY_URANDOM