###########################################################
# RapydScript Standard Library
# Author: Alexander Tsepkov
# Copyright 2013 Pyjeon Software LLC
# License: Apache License    2.0
# This library is covered under Apache license, so that
# you can distribute it with your RapydScript applications.
###########################################################


# basic implementation of Python's 'random' library

# JavaScript's Math.random() does not allow seeding its random generator, to bypass that, this module implements its own
# version that can be seeded. I decided on RC4 algorithm for this.

_$rapyd$_seed_state = {
    key: [],
    key_i: 0,
    key_j: 0
}
_$rapyd$_get_random_byte = def():
    _$rapyd$_seed_state.key_i = (_$rapyd$_seed_state.key_i + 1) % 256
    _$rapyd$_seed_state.key_j = (_$rapyd$_seed_state.key_j + _$rapyd$_seed_state.key[_$rapyd$_seed_state.key_i]) % 256
    _$rapyd$_seed_state.key[_$rapyd$_seed_state.key_i], _$rapyd$_seed_state.key[_$rapyd$_seed_state.key_j] = \
            _$rapyd$_seed_state.key[_$rapyd$_seed_state.key_j], _$rapyd$_seed_state.key[_$rapyd$_seed_state.key_i]
    return _$rapyd$_seed_state.key[(_$rapyd$_seed_state.key[_$rapyd$_seed_state.key_i] + \
            _$rapyd$_seed_state.key[_$rapyd$_seed_state.key_j]) % 256]

def seed(x=Date().getTime()):
    if JS('typeof x') is 'number':
        x = x.toString()
    elif JS('typeof x') is not 'string':
        raise TypeError("unhashable type: '" + JS('typeof x') + "'")
    for i in range(256):
        _$rapyd$_seed_state.key[i] = i
    j = 0
    for i in range(256):
        j = (j + _$rapyd$_seed_state.key[i] + x.charCodeAt(i % x.length)) % 256
        _$rapyd$_seed_state.key[i], _$rapyd$_seed_state.key[j] = _$rapyd$_seed_state.key[j], _$rapyd$_seed_state.key[i]
seed()

def random():
    n = 0
    m = 1
    for i in range(8):
        n += _$rapyd$_get_random_byte() * m
        m *= 256
    return n / 18446744073709551616

# unlike the python version, this DOES build a range object, feel free to reimplement
def randrange():
    return choice(range.apply(this, arguments))

def randint(a, b):
    return int(random()*(b-a+1) + a)

def uniform(a, b):
    return random()*(b-a) + a

def choice(seq):
    if seq.length > 0:
        return seq[Math.floor(random()*seq.length)]
    else:
        raise IndexError()

# uses Fisher-Yates algorithm to shuffle an array
def shuffle(x, random_f=random):
    for i in range(x.length):
        j = Math.floor(random_f() * (i+1))
        x[i], x[j] = x[j], x[i]
    return x

# similar to shuffle, but only shuffles a subset and creates a copy
def sample(population, k):
    x = population.slice()
    for i in range(population.length-1, population.length-k-1, -1):
        j = Math.floor(random() * (i+1))
        x[i], x[j] = x[j], x[i]
    return x.slice(population.length-k)


#import stdlib
#a = range(50)
#random.seed(5)
#print(random.choice(a))
#print(random.shuffle(a))
#print(random.randrange(10))
#print(random.randint(1,5))
#print(random.uniform(1,5))
#print(random.sample(range(20),5))