"""!
@file ui.py
@brief Graphical User Interface for the Calculator application.
@details Uses customtkinter to create a grid-based calculator and connects it to the math_lib module for calculations.
"""

import customtkinter as ctk
import math_lib

def run_gui():

    def can_add_operator():
        """!
        @brief Checks if a mathematical operator can be added to the current expression.
        @details Validates the display text to prevent adding operators to an empty string or chaining multiple operators.
        @return True if an operator can be appended safely, False otherwise.
        """
        text = display.get()

        if text == "":
            return False
        
        forbidden_suffixes = ("+", "-", "*", "/", ".", "^", "sq", "sqrt", "rt", "1/x")
        
        if text.endswith(forbidden_suffixes):
            return False
        
        return True


    def auto_compute():
        """!
        @brief Automatically computes the current expression before appending a new operator.
        @details Allows the user to chain calculations continuously (e.g., typing "5+5+" automatically calculates 10 before adding the next "+").
        """
        text = display.get()
        forbidden_suffixes = ("+", "-", "*", "/", ".", "^", "sq", "sqrt", "rt", "1/x")
        if text.endswith(forbidden_suffixes):
            return
        
        text_to_check = text[1:] if text.startswith("-") else text

        for op in ["+", "-", "*", "/", "^", "sq", "rt", "1/x", "!"]:
            if op in text_to_check:
                button_equals()
                break


    def open_help():  
        """!
        @brief Opens a secondary top-level window containing a help guide.
        @details Displays instructions for the buttons, keyboard shortcuts, and general information about errors.
        """
        help_window = ctk.CTkToplevel(app)
        help_window.title("Hint")
        help_window.geometry("400x500")
        help_window.attributes("-topmost", True)
        
        textbox = ctk.CTkTextbox(help_window, font=("Roboto", 15), wrap="word", fg_color="transparent")
        textbox.pack(fill="both", expand=True, padx=20, pady=20)
        
        help_text = """ WELCOME TO THE CALCULATOR

    Buttons & Functions:
    • xⁿ (Power): Enter the base, press xⁿ, and enter the exponent. (Example: 5 xⁿ 3 = 125)
    • ⁿ√x (N-th Root): Enter the number, press ⁿ√x, and enter the degree of the root. (Example: 27 ⁿ√x 3 = 3)
    • x² (Square): Immediately calculates the square of the current number.
    • √x (Square Root): Immediately calculates the square root of the current number.
    • ¹/x (Inverse): Calculates 1 divided by the current number.
    • ! (Factorial): Calculates the product of all positive integers up to the given number.

    Keyboard Shortcuts:
    You can fully control the calculator using your keyboard.
    • Enter / = : Calculates the result
    • Backspace : Deletes the last character
    • Esc : Clears the entire display (AC)
    """

        textbox.insert("0.0", help_text)
        textbox.configure(state="disabled")

    app = ctk.CTk()
    app.title("Calculator")
    app.geometry("450x700")
    app.resizable(True, True)
    ctk.set_appearance_mode("dark")
    app.configure(fg_color="#121212")

    for i in range(4):
        app.grid_columnconfigure(i, weight=1, uniform="equal_cons")
    for i in range (1, 7):
        app.grid_rowconfigure(i, weight=1, uniform="equal_rows")

    font_display = ("Roboto", 55, "bold")
    font_button = ("Roboto", 24,"bold")

    theme_num = {"fg_color": "#2b2b2b", "hover_color": "#404040", "text_color": "white", "font": font_button}
    theme_op = {"fg_color": "#D32F2F", "hover_color": "#F44336", "text_color": "white", "font": font_button}
    theme_spec = {"fg_color": "#E0E0E0", "hover_color": "#FFFFFF", "text_color": "black", "font": font_button}


    display = ctk.CTkEntry(app, placeholder_text="0", justify="right", state="readonly", font=font_display, height=90, fg_color="#1e1e1e", border_color="#D32F2F")
    display.grid(row=0, column=0, columnspan=4, padx=10, pady=(20, 20), sticky="nsew")


    def key_pressed(event):
        """!
        @brief Binds keyboard inputs to the corresponding calculator functions.
        @param event The Tkinter event object containing information about the pressed key.
        """
        char = event.char
        keysym = event.keysym

        if char == '1' : button1()
        elif char == '2' : button2()
        elif char == '3' : button3()
        elif char == '4' : button4()
        elif char == '5' : button5()
        elif char == '6' : button6()
        elif char == '7' : button7()
        elif char == '8' : button8()
        elif char == '9' : button9()
        elif char == '0' : button0()

        elif char == '+': button_add()
        elif char == '-': button_sub()
        elif char == '*': button_mul()
        elif char == '/': button_div()
        elif char == '!': button_factorial()
        elif char == '.' or char == ',': button_point()

        elif keysym == 'Return' or keysym == 'KP_Enter' or char == '=': button_equals()
        elif keysym == 'BackSpace': button_rm()
        elif keysym == 'Escape': button_ac()
        
    app.bind('<Key>', key_pressed)


    def button_equals():
        """!
        @brief Evaluates the mathematical expression currently shown on the display.
        @details Parses the string, identifies the operation, sends it to the math_lib module, and updates the display. Also handles dynamic error formatting.
        """
        expression = display.get()

        forbidden_suffixes = ("+", "-", "*", "/", ".", "^", "rt")
        if expression.endswith(forbidden_suffixes):
            return
        
        try:
            expression = expression.replace("--", "+")
            expression = expression.replace("+-", "-")

            if "+" in expression:
                numbers = expression.split("+")
                result = math_lib.add(float(numbers[0]), float(numbers[1]))

            elif "*" in expression:
                numbers = expression.split("*")
                result = math_lib.mul(float(numbers[0]), float(numbers[1]))

            elif "ˇ2" in expression:
                numbers = expression.split("ˇ2")       
                result = math_lib.square(float(numbers[0]))

            elif "^" in expression:
                numbers = expression.split("^")
                result = math_lib.power(float(numbers[0]), float(numbers[1]))

            elif "rt" in expression:
                numbers = expression.split("rt")
                result = math_lib.root(float(numbers[1]), float(numbers[0]))

            elif "/" in expression:
                numbers = expression.split("/")
                result = math_lib.div(float(numbers[0]), float(numbers[1]))

            elif "-" in expression:
                numbers = expression.rsplit("-", 1)
                result = math_lib.sub(float(numbers[0]), float(numbers[1]))
            
            else:
                result = expression
            
            display.configure(state="normal")
            display.delete(0, "end")
            display.insert("end", str(result))
            display.configure(state="readonly")

        except Exception as e:
            display.configure(state="normal")
            display.delete(0,"end")

            error_msg = str(e)

            if error_msg == "":
                error_msg = type(e).__name__

            if len(error_msg) > 12:
                display.configure(font=("Roboto", 20, "bold"))
            elif len(error_msg) > 8:
                display.configure(font=("Roboto", 38, "bold"))
            else:
                display.configure(font=("Roboto", 55, "bold"))

            display.insert("end", error_msg)
            display.configure(state="readonly")

    button = ctk.CTkButton(app, text="=", command=button_equals, **theme_op)
    button.grid(row=6, column=3, padx=5, pady=5, sticky="nsew")


    def button_inverse():
        """!
        @brief Immediately calculates the inverse (1/x) of the last entered number.
        """
        text = display.get()
        if text == "":
            return
        
        last_number = text
        for operator in ["+", "-", "*", "/", "^", "rt"]:
            if operator in last_number:
                last_number = last_number.split(operator)[-1]

        if last_number != "":
            try:
                number = float(last_number)
                result = math_lib.inverse(number)

                new_text = text[:-len(last_number)] + str(result)

                display.configure(state="normal")
                display.delete(0, "end")
                display.insert("end", new_text)
                display.configure(state="readonly")
            except Exception:
                pass

    button = ctk.CTkButton(app, text="1/x", command=button_inverse, **theme_spec)
    button.grid(row=2, column=2, padx=5, pady=5, sticky="nsew")


    def button_sq():
        """!
        @brief Immediately calculates the square root of the last entered number.
        @details Includes frontend validation to block operations on negative numbers ending in a minus sign.
        """
        text = display.get()
        if text == "":
            return
        
        last_number = text
        for operator in ["+", "-", "*", "/", "^", "rt"]:
            if operator in last_number:
                last_number = last_number.split(operator)[-1]

        if last_number != "":
            if text.endswith("-" + last_number):
                prefix = text[:-(len(last_number) + 1)]
                if prefix == "" or prefix.endswith(("+", "-", "*", "/", "^", "rt")):
                    return
            try:
                number = float(last_number)
                result = math_lib.sqrt(number)

                new_text = text[:-len(last_number)] + str(result)

                display.configure(state="normal")
                display.delete(0, "end")
                display.insert("end", new_text)
                display.configure(state="readonly")
            except Exception:
                pass

    button = ctk.CTkButton(app, text="√x", command=button_sq, **theme_spec)
    button.grid(row=2, column=1, padx=5, pady=5, sticky="nsew")


    def button_square():
        """!
        @brief Immediately calculates the square of the last entered number.
        """
        text = display.get()
        if text == "":
            return
        
        last_number = text
        for operator in ["+", "-", "*", "/", "^", "rt"]:
            if operator in last_number:
                last_number = last_number.split(operator)[-1]

        if last_number != "":
            try:
                number = float(last_number)
                result = math_lib.square(number)

                new_text = text[:-len(last_number)] + str(result)
                display.configure(state="normal")
                display.delete(0, "end")
                display.insert("end", new_text)
                display.configure(state="readonly")
            except Exception:
                pass

    button = ctk.CTkButton(app, text="x²", command=button_square, **theme_spec)
    button.grid(row=1, column=1, padx=5, pady=5, sticky="nsew")


    def button_root():
        """!
        @brief Appends the N-th root operator ('rt') to the current expression.
        """
        auto_compute()
        if can_add_operator() == True:
            display.configure(state="normal")
            display.insert("end", "rt")
            display.configure(state="readonly")

    button = ctk.CTkButton(app, text="ⁿ√x", command=button_root, **theme_spec)
    button.grid(row=2, column=0, padx=5, pady=5, sticky="nsew")


    def button_power():
        """!
        @brief Appends the power operator ('^') to the current expression.
        """
        auto_compute()
        if can_add_operator() == True:
            display.configure(state="normal")
            display.insert("end", "^")
            display.configure(state="readonly")

    button = ctk.CTkButton(app, text="xⁿ", command=button_power, **theme_spec)
    button.grid(row=1, column=0, padx=5, pady=5, sticky="nsew")


    def button_add():
        """!
        @brief Appends the addition operator ('+') to the display.
        """
        auto_compute()
        if can_add_operator() == True:
            display.configure(state="normal")
            display.insert("end", "+")
            display.configure(state="readonly")

    button = ctk.CTkButton(app, text="+", command=button_add, **theme_op)
    button.grid(row=5, column=3, padx=5, pady=5, sticky="nsew")


    def button_sub():
        """!
        @brief Appends the subtraction operator ('-') to the display.
        @details Contains logic to handle appending negative signs to empty expressions or after other operators.
        """
        auto_compute()
        text = display.get()

        if text == "":
            display.configure(state="normal")
            display.insert("end", "-")
            display.configure(state="readonly")
        
        elif text.endswith(("+", "-", "*", "/", "^", "rt", "sq", "sqrt", "1/x")):
            if not text.endswith("--"):
                display.configure(state="normal")
                display.insert("end", "-")
                display.configure(state="readonly")
        
        elif can_add_operator() == True:
            display.configure(state="normal")
            display.insert("end", "-")
            display.configure(state="readonly")

    button = ctk.CTkButton(app, text="-", command=button_sub, **theme_op)
    button.grid(row=4, column=3, padx=5, pady=5, sticky="nsew")


    def button_rm():
        """!
        @brief Removes the last character from the display, acting as a backspace.
        """
        current_text = display.get()
        if len(current_text) > 0:
            display.configure(state="normal")
    
        display.delete(len(current_text) - 1, "end")
        display.configure(state="readonly")

    button = ctk.CTkButton(app, text="⌫", command=button_rm, **theme_spec)
    button.grid(row=1, column=3, padx=5, pady=5, sticky="nsew")


    def button_div():
        """!
        @brief Appends the division operator ('/') to the display.
        """
        auto_compute()
        if can_add_operator() == True:
            display.configure(state="normal")
            display.insert("end", "/")
            display.configure(state="readonly")

    button = ctk.CTkButton(app, text="÷", command=button_div, **theme_op)
    button.grid(row=2, column=3, padx=5, pady=5, sticky="nsew")


    def button_mul():
        """!
        @brief Appends the multiplication operator ('*') to the display.
        """
        auto_compute()
        if can_add_operator() == True:
            display.configure(state="normal")
            display.insert("end", "*")
            display.configure(state="readonly")

    button = ctk.CTkButton(app, text="×", command=button_mul, **theme_op)
    button.grid(row=3, column=3, padx=5, pady=5, sticky="nsew")


    def button_ac():
        """!
        @brief Clears the entire display, acting as an All Clear (AC) function.
        """
        display.configure(state="normal")
        display.delete(0, "end")
        display.configure(state="readonly")

    button = ctk.CTkButton(app, text="AC", command=button_ac, **theme_spec)
    button.grid(row=1, column=2, padx=5, pady=5, sticky="nsew")


    def button_factorial():
        """!
        @brief Immediately calculates the factorial (!) of the last entered number.
        """
        text = display.get()
        if text == "":
            return
        
        last_number = text
        for operator in ["+", "-", "*", "/", "^", "rt"]:
            if operator in last_number:
                last_number = last_number.split(operator)[-1]

        if last_number != "":
            try:
                number = int(float(last_number))
                result = math_lib.factorial(number)

                new_text = text[:-len(last_number)] + str(result)

                display.configure(state="normal")
                display.delete(0, "end")
                display.insert("end", new_text)
                display.configure(state="readonly")
            except Exception:
                pass

    button = ctk.CTkButton(app, text="n!", command=button_factorial, **theme_spec)
    button.grid(row=6, column=0, padx=5, pady=5, sticky="nsew")


    def button_point():
        """!
        @brief Appends a decimal point to the current number being typed.
        """
        current_text = display.get()
        last_number = current_text
        for operator in ["+", "-", "*", "/", "^", "rt"]:
            if operator in last_number:
                last_number = last_number.split(operator)[-1]
        
        if "." not in last_number:
            display.configure(state="normal")

            if last_number == "":
                display.insert("end", "0.")
            else:
                display.insert("end", ".")

        display.configure(state="readonly")

    button = ctk.CTkButton(app, text=".", command=button_point, **theme_num)
    button.grid(row=6, column=2, padx=5, pady=5, sticky="nsew")


    def button0():
        """!
        @brief Appends the number '0' to the display.
        """
        display.configure(state="normal")
        display.insert("end", "0")
        display.configure(state="readonly")

    button = ctk.CTkButton(app, text="0", command=button0, **theme_num)
    button.grid(row=6, column=1, padx=5, pady=5, sticky="nsew")


    def button1():
        """!
        @brief Appends the number '1' to the display.
        """
        display.configure(state="normal")
        display.insert("end", "1")
        display.configure(state="readonly")

    button = ctk.CTkButton(app, text="1", command=button1, **theme_num)
    button.grid(row=5, column=0, padx=5, pady=5, sticky="nsew")


    def button2():
        """!
        @brief Appends the number '2' to the display.
        """
        display.configure(state="normal")
        display.insert("end", "2")
        display.configure(state="readonly")

    button = ctk.CTkButton(app, text="2", command=button2, **theme_num)
    button.grid(row=5, column=1, padx=5, pady=5, sticky="nsew")


    def button3():
        """!
        @brief Appends the number '3' to the display.
        """
        display.configure(state="normal")
        display.insert("end", "3")
        display.configure(state="readonly")

    button = ctk.CTkButton(app, text="3", command=button3, **theme_num)
    button.grid(row=5, column=2, padx=5, pady=5, sticky="nsew")


    def button4():
        """!
        @brief Appends the number '4' to the display.
        """
        display.configure(state="normal")
        display.insert("end", "4")
        display.configure(state="readonly")

    button = ctk.CTkButton(app, text="4", command=button4, **theme_num)
    button.grid(row=4, column=0, padx=5, pady=5, sticky="nsew")


    def button5():
        """!
        @brief Appends the number '5' to the display.
        """
        display.configure(state="normal")
        display.insert("end", "5")
        display.configure(state="readonly")

    button = ctk.CTkButton(app, text="5", command=button5, **theme_num)
    button.grid(row=4, column=1, padx=5, pady=5, sticky="nsew")


    def button6():
        """!
        @brief Appends the number '6' to the display.
        """
        display.configure(state="normal")
        display.insert("end", "6")
        display.configure(state="readonly")

    button = ctk.CTkButton(app, text="6", command=button6, **theme_num)
    button.grid(row=4, column=2, padx=5, pady=5, sticky="nsew")


    def button7():
        """!
        @brief Appends the number '7' to the display.
        """
        display.configure(state="normal")
        display.insert("end", "7")
        display.configure(state="readonly")

    button = ctk.CTkButton(app, text="7", command=button7, **theme_num)
    button.grid(row=3, column=0, padx=5, pady=5, sticky="nsew")


    def button8():
        """!
        @brief Appends the number '8' to the display.
        """
        display.configure(state="normal")
        display.insert("end", "8")
        display.configure(state="readonly")

    button = ctk.CTkButton(app, text="8", command=button8, **theme_num)
    button.grid(row=3, column=1, padx=5, pady=5, sticky="nsew")


    def button9():
        """!
        @brief Appends the number '9' to the display.
        """
        display.configure(state="normal")
        display.insert("end", "9")
        display.configure(state="readonly")

    button = ctk.CTkButton(app, text="9", command=button9, **theme_num)
    button.grid(row=3, column=2, padx=5, pady=5, sticky="nsew")


    help_button = ctk.CTkButton(app, text="?", width=15, height=15, font=("Roboto", 14, "bold"), fg_color="#7a7a7a", hover_color="#333333", command=open_help)

    help_button.place(x=20, y=30)

    app.mainloop()