from js import document
import math

def extract_abc(expr):
    expr = expr.replace(" ", "")
    expr = expr.replace("-", "+-")
    if expr.startswith("+"):
        expr = expr[1:]

    terms = expr.split("+")
    a = 0
    b = 0
    c = 0

    for term in terms:
        if term == "":
            continue

        if "x^2" in term:
            coef = term.replace("x^2", "")
            if coef in ["", "+"]:
                coef = "1"
            elif coef == "-":
                coef = "-1"
            a = int(coef)

        elif "x" in term:
            coef = term.replace("x", "")
            if coef in ["", "+"]:
                coef = "1"
            elif coef == "-":
                coef = "-1"
            b = int(coef)

        else:
            c = int(term)

    return a, b, c


def bereken(event=None):
    expr = document.querySelector("#formula_input").value

    if expr.strip() == "":
        document.querySelector("#abc-output").innerHTML = "Vul een formule in."
        return

    try:
        a, b, c = extract_abc(expr)
    except:
        document.querySelector("#abc-output").innerHTML = "Ongeldige formule."
        return

    D = b*b - 4*a*c

    if D < 0:
        document.querySelector("#abc-output").innerHTML = (
            f"Discriminant: Δ = {D}<br><br>"
            "De vergelijking heeft geen reële oplossingen."
        )
        return

    sqrtD = math.sqrt(D)

    x1 = (-b + sqrtD) / (2*a)
    x2 = (-b - sqrtD) / (2*a)

    # exacte wortelvorm als tekst
    exact_x1 = f"(-{b} + √{D}) / {2*a}"
    exact_x2 = f"(-{b} - √{D}) / {2*a}"

    output = f"""
    <b>Stap 1: Coëfficiënten</b><br>
    a = {a}, b = {b}, c = {c}<br><br>

    <b>Stap 2: Discriminant</b><br>
    Δ = {b}² - 4·{a}·{c} = {D}<br><br>

    <b>Stap 3: Wortel van de discriminant</b><br>
    √Δ = √{D} = {sqrtD:.4f}<br><br>

    <b>Stap 4: Oplossingen</b><br>
    x₁ = {x1:.4f}<br>
    Exact: {exact_x1}<br><br>

    x₂ = {x2:.4f}<br>
    Exact: {exact_x2}<br>
    """

    document.querySelector("#abc-output").innerHTML = output