"""
Calculate digits of pi. This module can be run interactively with

    python pidigits.py

"""

import math
import sys
from time import perf_counter

from mpmath.libmp.libelefun import pi_fixed
from mpmath.libmp.libintmath import bin_to_radix, numeral


def display_fraction(digits, skip=0, colwidth=10, columns=5):
    perline = colwidth * columns
    printed = 0
    for linecount in range((len(digits)-skip) // (colwidth * columns)):
        line = digits[skip+linecount*perline:skip+(linecount+1)*perline]
        for i in range(columns):
            print(line[i*colwidth : (i+1)*colwidth], end=' ')
        print(":", (linecount+1)*perline)
        if (linecount+1) % 10 == 0:
            print()
        printed += colwidth*columns
    rem = (len(digits)-skip) % (colwidth * columns)
    if rem:
        buf = digits[-rem:]
        s = ""
        for i in range(columns):
            s += buf[:colwidth].ljust(colwidth+1, " ")
            buf = buf[colwidth:]
        print(s + ":", printed + colwidth*columns)

def calculateit(base, n, tofile):
    intpart = numeral(3, base)
    skip = 1
    if base <= 3:
        skip = 2

    prec = int(n*math.log(base,2))+10

    print("Step 1 of 2: calculating binary value...")
    t = perf_counter()
    a = pi_fixed(prec, verbose=True, verbose_base=base)
    step1_time = perf_counter() - t

    print("Step 2 of 2: converting to specified base...")
    t = perf_counter()
    d = bin_to_radix(a, prec, base, n)
    d = numeral(d, base, n)
    step2_time = perf_counter() - t

    print("\nWriting output...\n")

    if tofile:
        out_ = sys.stdout
        sys.stdout = tofile
    print("%i base-%i digits of pi:\n" % (n, base))
    print(intpart, ".\n")

    display_fraction(d, skip, colwidth=10, columns=5)
    if tofile:
        sys.stdout = out_
    print("\nFinished in %f seconds (%f calc, %f convert)" % \
        ((step1_time + step2_time), step1_time, step2_time))

def interactive():
    print("Compute digits of pi with mpmath\n")
    base = input("Which base? (2-36, 10 for decimal) \n> ")
    digits = input("How many digits? (enter a big number, say, 10000)\n> ")
    tofile = input("Output to file? (enter a filename, or just press " \
        "enter\nto print directly to the screen) \n> ")
    if tofile:
        tofile = open(tofile, "w")

    calculateit(int(base), int(digits), tofile)
    input("\nPress enter to close this script.")

if __name__ == "__main__":
    interactive()
