#!/usr/bin/python3
# -*- coding: utf-8 -*-
"""
Efficiency discusion using fibonacci sequence:

f(n) = f(n - 2) + f(n - 1)
     = 1 if n == 0 or n == 1
"""


# fibonacci using a loop
def fib_loop(n: int) -> int:
    "Computes first n fib numbers, using loop"
    a, b = 0, 1  # the first and second Fibonacci numbers
    for i in range(n):
        a, b = b, a + b
    return a


print(fib_loop(10))


# recursive Fibonacci (inefficient)
def fib_rec(n: int) -> int:
    """Return Fibonacci of x, where x is a non-negative int"""
    if n < 2:
        return n  # or 1
    else:
        return fib_rec(n - 1) + fib_rec(n - 2)


print(fib_rec(10))

# %% Tail recursion


# %% tail recursive fibonacci (efficient)
def fib_rec_tail(n: int, previous: int = 0, current: int = 1, i: int = 0) -> int:
    """
    Computes first n fib numbers, using tail recursion
    Another way of defaulting values.
    This is both more sensible and more dangerous,
    since the user can break it.
    """
    if i < n:
        return fib_rec_tail(n, current, previous + current, i + 1)
    else:
        return previous


print(fib_rec_tail(10))


# %% tail recursive fibonacci (efficient)
def fib_rec_tail_wrapped(n: int) -> int:
    """
    Computes first n fib numbers, using tail recursion
    One way of defaulting values, which hides the values.
    """

    def go(previous: int, current: int, i: int) -> int:
        if i < n:
            return go(current, previous + current, i + 1)
        else:
            return previous

    return go(0, 1, 0)


print(fib_rec_tail_wrapped(10))