from pyscript import document
import math


def log_base(value, base):
    return math.log(value) / math.log(base)


def show_fields(fields_to_show):
    all_fields = [
        "field_g",
        "field_a",
        "field_b",
        "field_n",
        "field_p",
        "field_y",
    ]
    for field_id in all_fields:
        el = document.getElementById(field_id)
        if field_id in fields_to_show:
            el.classList.add("show")
        else:
            el.classList.remove("show")


def on_rule_change(event=None):
    rule = document.getElementById("rule_select").value
    if rule in ("1", "2"):
        show_fields({"field_g", "field_a", "field_b"})
    elif rule == "3":
        show_fields({"field_g", "field_a", "field_n"})
    elif rule == "4":
        show_fields({"field_g", "field_y"})
    elif rule in ("5"):
        show_fields({"field_g", "field_a"})

    document.getElementById("formula").innerText = "Kies een regel en vul de waarden in."
    document.getElementById("output").innerText = ""


def read_float(input_id, label):
    raw = document.getElementById(input_id).value
    if raw is None or raw == "":
        raise ValueError(f"Vul {label} in.")
    try:
        return float(raw)
    except ValueError as exc:
        raise ValueError(f"{label} moet een getal zijn.") from exc


def set_result(formula_html, output_text):
    document.getElementById("formula").innerHTML = formula_html
    document.getElementById("output").innerText = output_text


def bereken(event):
    rule = document.getElementById("rule_select").value

    try:
        if rule == "1":
            g = read_float("g_input", "g")
            a = read_float("a_input", "a")
            b = read_float("b_input", "b")
            if g <= 0 or g == 1 or a <= 0 or b <= 0:
                raise ValueError("g > 0 en g ≠ 1, a > 0, b > 0.")
            lhs = log_base(a, g) + log_base(b, g)
            rhs = log_base(a * b, g)
            set_result(
                f"log<sub>g</sub>({a}) + log<sub>g</sub>({b}) = log<sub>g</sub>({a * b})",
                f"Links = {lhs:.6g}, rechts = {rhs:.6g}",
            )

        elif rule == "2":
            g = read_float("g_input", "g")
            a = read_float("a_input", "a")
            b = read_float("b_input", "b")
            if g <= 0 or g == 1 or a <= 0 or b <= 0:
                raise ValueError("g > 0 en g ≠ 1, a > 0, b > 0.")
            lhs = log_base(a, g) - log_base(b, g)
            rhs = log_base(a / b, g)
            set_result(
                f"log<sub>g</sub>({a}) - log<sub>g</sub>({b}) = log<sub>g</sub>({a / b})",
                f"Links = {lhs:.6g}, rechts = {rhs:.6g}",
            )

        elif rule == "3":
            g = read_float("g_input", "g")
            a = read_float("a_input", "a")
            n = read_float("n_input", "n")
            if g <= 0 or g == 1 or a <= 0:
                raise ValueError("g > 0 en g ≠ 1, a > 0.")
            lhs = log_base(a ** n, g)
            rhs = n * log_base(a, g)
            set_result(
                f"log<sub>g</sub>({a}<sup>{n}</sup>) = {n} · log<sub>g</sub>({a})",
                f"Links = {lhs:.6g}, rechts = {rhs:.6g}",
            )

        elif rule == "4":
            g = read_float("g_input", "g")
            y = read_float("y_input", "y")
            if g <= 0 or g == 1:
                raise ValueError("g > 0 en g ≠ 1.")
            x = g ** y
            set_result(
                f"log<sub>g</sub>(x) = {y} geeft x = {g}<sup>{y}</sup>",
                f"x = {x:.6g}",
            )

        elif rule == "5":
            g = read_float("g_input", "g")
            a = read_float("a_input", "a")
            if g <= 0 or g == 1:
                raise ValueError("g > 0 en g ≠ 1.")
            value = log_base(g ** a, g)
            set_result(
                f"log<sub>g</sub>({g}<sup>{a}</sup>) = {a}",
                f"Uitkomst = {value:.6g}",
            )


    except ValueError as exc:
        document.getElementById("formula").innerText = "Controleer je invoer."
        document.getElementById("output").innerText = str(exc)


on_rule_change()