'''
Owner: AerospaceResearch.net
About: This module hosts the functions used for finding roots of a cubic equation
Note: Please try to maintain proper documentation
Logic Description:
'''

import math
import copy
from visma.io.checks import getVariables
from visma.io.parser import tokensToString
from visma.functions.structure import Expression
from visma.functions.constant import Constant, Zero
from visma.functions.variable import Variable
from visma.functions.operator import Binary, Plus, Minus, Sqrt
from visma.simplify.simplify import simplifyEquation, moveRTokensToLTokens
from visma.config.values import ROUNDOFF


def getRootsCubic(coeffs):
    """ Applies an implementation of Cardano's Method (https://en.wikipedia.org/wiki/Cubic_function) on the coefficients
        of the cubic equation roots

        Arguments:
            coeffs {list} -- list of coefficients of the equation

        Returns:
            roots {list} -- list of roots of cubic equation
            (each element of roots {list} is a list of two elements, where 1st one denotes real part & second part shows imaginary part)
            animation {list} -- list of equation solving process
            comments {list} -- list of comments in equation solving process
    """
    from visma.solvers.polynomial.roots import cubeRoot
    roots = []
    animations = []
    comments = []
    a = coeffs[3]
    b = coeffs[2]
    c = coeffs[1]
    d = coeffs[0]

    f = ((3*c/a) - (b**2/a**2))/3
    g = ((2*(b**3)/(a**3)) - (9*b*c/(a**2)) + (27*d/a))/27
    h = ((g**2)/4) + ((f**3)/27)
    animations += [[]]
    comments += [['Value of determinants [f, g, h] are ' + str(f) + ', ' + str(g) + ', ' + str(h)]]
    if h <= 0:
        if h == 0 and g == 0 and f == 0:
            # All three (real) roots exist and are equal
            animations += [[]]
            comments += [['Hence, three equal real roots exist.']]
            res = cubeRoot(d/a)
            valueX1 = [-res, 0]
            valueX2 = [-res, 0]
            valueX3 = [-res, 0]
            roots.append(valueX1)
        else:
            # All three (real) roots exist
            animations += [[]]
            comments += [['Hence, three equal non-equal real roots exist.']]
            i = (((g**2)/4) - h) ** (1./2.)
            j = cubeRoot(i)
            k = math.acos(-g/(2*i))
            L = j * (-1)
            M = math.cos(k/3)
            N = math.sqrt(3) * (math.sin(k/3))
            P = -(b/(3*a))
            valueX1 = [2*j*(math.cos(k/3)) - (b/(3*a)), 0]
            valueX2 = [L*(M + N) + P, 0]
            valueX3 = [L*(M - N) + P, 0]
            roots.extend([valueX1, valueX2, valueX3])
    else:
        # Only one (real) root exists
        animations += [[]]
        comments += [['Hence, one real root exists']]
        R = -(g/2) + h ** (1./2.)
        S = cubeRoot(R)
        T = -(g/2) - (h ** (1./2.))
        U = cubeRoot(T)
        valueX1 = [(S + U) - (b/(3*a)), 0]

        valueRealX2 = -(S + U)/2 - (b/(3*a))
        valueImagX2 = (S - U)*(3 ** (1./2.))/2
        valueX2 = [valueRealX2, valueImagX2]

        valueRealX3 = -(S + U)/2 - (b/(3*a))
        valueImagX3 = -(S - U)*(3 ** (1./2.))/2
        valueX3 = [valueRealX3, valueImagX3]
        roots.extend([valueX1, valueX2, valueX3])

    return roots, animations, comments


def cubicRoots(lTokens, rTokens):
    '''Used to get roots of a cubic equation
    This functions also translates roots {list} into final result of solution

    Argument:
        lTokens {list} -- list of LHS tokens
        rTokens {list} -- list of RHS tokens

    Returns:
        lTokens {list} -- list of LHS tokens
        rTokens {list} -- list of RHS tokens
        {empty list}
        token_string {string} -- final result stored in a string
        animation {list} -- list of equation solving process
        comments {list} -- list of comments in equation solving process
    '''
    from visma.solvers.polynomial.roots import getCoefficients

    animations = []
    comments = []
    lTokens, rTokens, _, token_string, animNew1, commentNew1 = simplifyEquation(lTokens, rTokens)
    animations.extend(animNew1)
    comments.extend(commentNew1)
    if len(rTokens) > 0:
        lTokens, rTokens = moveRTokensToLTokens(lTokens, rTokens)
    coeffs = getCoefficients(lTokens, rTokens, 3)
    var = getVariables(lTokens)
    roots, animNew2, commentNew2 = getRootsCubic(coeffs)
    animations.extend(animNew2)
    comments.extend(commentNew2)
    tokens1 = []
    expression1 = Expression(coefficient=1, power=3)
    variable = Variable(1, var[0], 1)
    tokens1.append(variable)
    if roots[0][1] == 0:
        binary = Binary()
        if roots[0][0] < 0:
            roots[0][0] *= -1
            binary.value = '+'
        else:
            binary.value = '-'
        tokens1.append(binary)
    constant = Constant(round(roots[0][0], ROUNDOFF), 1)
    tokens1.append(constant)

    expression1.tokens = tokens1
    lTokens = [expression1, Binary('*')]

    if len(roots) > 1:
        expression1.power = 1
        for _, root in enumerate(roots[1:]):
            tokens2 = []
            expression2 = Expression(coefficient=1, power=1)
            variable = Variable(1, var[0], 1)
            tokens2.append(variable)
            binary = Binary()
            if root[1] == 0:
                if root[0] < 0:
                    root[0] *= -1
                    binary.value = '+'
                else:
                    binary.value = '-'
                tokens2.append(binary)
                constant = Constant(round(root[0], ROUNDOFF), 1)
                tokens2.append(constant)
            else:
                binary.value = '-'
                tokens2.append(binary)
                expressionResult = Expression(coefficient=1, power=1)
                tokensResult = []
                real = Constant(round(root[0], ROUNDOFF), 1)
                tokensResult.append(real)
                imaginary = Constant(round(root[1], ROUNDOFF), 1)
                if imaginary.value < 0:
                    tokensResult.append(Minus())
                    imaginary.value = abs(imaginary.value)
                    tokensResult.append(imaginary)
                else:
                    tokensResult.extend([Plus(), imaginary])
                sqrt = Sqrt(Constant(2, 1), Constant(-1, 1))
                tokensResult.append(Binary('*'))
                tokensResult.append(sqrt)
                expressionResult.tokens = tokensResult
                tokens2.append(expressionResult)
            expression2.tokens = tokens2
            lTokens.extend([expression2, Binary('*')])
    lTokens.pop()
    rTokens = [Zero()]
    tokenToStringBuilder = copy.deepcopy(lTokens)
    tokLen = len(lTokens)
    equalTo = Binary()
    equalTo.scope = [tokLen]
    equalTo.value = '='
    tokenToStringBuilder.append(equalTo)
    tokenToStringBuilder.extend(rTokens)
    token_string = tokensToString(tokenToStringBuilder)
    animations.append(copy.deepcopy(tokenToStringBuilder))
    comments.append([])
    return lTokens, rTokens, [], token_string, animations, comments