import matplotlib.pyplot as plt
from matplotlib.ticker import MultipleLocator, AutoMinorLocator
from math import *
from exprParser import *

parser = ExprParser()

def plotFunction(
    f,
    xmin = -8., xmax = 8., 
    ymin = -6., ymax = 6.,
    pictureWidth_cm = 16.,
    dpi = 100
):
    fig = plt.figure()
    aspect = (ymax - ymin)/(xmax - xmin)
    pictureHeight_cm = pictureWidth_cm*aspect
    fig.set_size_inches(pictureWidth_cm/2.54, pictureHeight_cm/2.54)
    fig.set_dpi(dpi)
    ax = fig.add_subplot(1, 1, 1)
    ax.set_aspect(1.)
    ax.set_xlim(xmin, xmax)
    ax.set_ylim(ymin, ymax)

    ax.xaxis.set_major_locator(MultipleLocator(5))
    ax.xaxis.set_minor_locator(AutoMinorLocator(5))
    ax.yaxis.set_major_locator(MultipleLocator(5))
    ax.yaxis.set_minor_locator(AutoMinorLocator(5))

    ax.axhline(0, color="black")
    ax.axvline(0, color="black")
    ax.grid(which='major')
    ax.grid(which='minor', linestyle=":")

    x = []
    y = []
    xx = xmin
    dx = (xmax - xmin)/1000
    yCenter = (ymin + ymax)/2.
    dy = abs(ymax - ymin)
    yMinBorder = yCenter - dy*0.75
    yMaxBorder = yCenter + dy*0.75
    while xx <= xmax:
        try:
            yy = f(xx)
            if yy > yMaxBorder:
                yy = inf
            elif yy < yMinBorder:
                yy = -inf
        except Exception:
            yy = None
        x.append(xx)
        y.append(yy)
        xx += dx
    ax.plot(x, y)

    plt.show()

def plotExpression(
    funcText,
    xmin = -8., xmax = 8., 
    ymin = -6., ymax = 6.,
    pictureWidth_cm = 16.
):
    try:
        parser.parse(funcText)
        plotFunction(
            parserFunction, 
            xmin, xmax, ymin, ymax,
            pictureWidth_cm
        )
    except SyntaxError as e:
        print("Parse error: " + str(e))

def parserFunction(x):
    return parser.evaluate(x)

def main():
    while True:
        f = input("Input a function: ");
        if f == "":
            break;
        try:
            plotExpression(f)
        except SyntaxError as e:
            print("Syntax error: " + str(e))

if __name__ == "__main__":
    main()