from tkinter import *
import all_constant as c


class Converter:

    def __init__(self):
        """
        Multi-currency converter GUI - shows currency selection buttons.
        Conversion logic not yet implemented.
        """

        self.all_calculations_list = []

        # Tracks which currency is selected as From and To
        self.from_currency = None
        self.to_currency = None

        self.main_frame = Frame(padx=10, pady=10)
        self.main_frame.grid()

        self.heading = Label(self.main_frame,
                             text="Currency Converter",
                             font=("Arial", "16", "bold"))
        self.heading.grid(row=0)

        instructions = ("Select a FROM currency, then a TO currency, "
                        "enter an amount and press Convert.")
        self.instructions = Label(self.main_frame,
                                  text=instructions,
                                  wraplength=300, width=45,
                                  justify="left")
        self.instructions.grid(row=1)

        # Currency selection buttons frame
        self.currency_frame = Frame(self.main_frame)
        self.currency_frame.grid(row=2, pady=5)

        # List of supported currencies
        self.currencies = c.CURRENCIES

        # Build one button per currency - store refs in dict for easy access
        self.currency_buttons = {}
        for i, currency in enumerate(self.currencies):
            btn = Button(self.currency_frame,
                         text=currency,
                         bg="#AAAAAA",
                         fg="#FFFFFF",
                         font=("Arial", "12", "bold"),
                         width=6,
                         command=lambda cur=currency: self.select_currency(cur))
            btn.grid(row=0, column=i, padx=4, pady=4)
            self.currency_buttons[currency] = btn

        # Label showing current From / To selection
        self.selection_label = Label(self.main_frame,
                                     text="From: —    To: —",
                                     font=("Arial", "11"),
                                     fg="#004C99")
        self.selection_label.grid(row=3)

        # Amount entry
        self.amount_entry = Entry(self.main_frame,
                                  font=("Arial", "14"))
        self.amount_entry.grid(row=4, padx=10, pady=10)

        # Answer / error label
        self.answer_error = Label(self.main_frame,
                                  text="Select currencies above to begin",
                                  fg="#004C99",
                                  font=("Arial", "13", "bold"))
        self.answer_error.grid(row=5)

        # Bottom buttons frame
        self.button_frame = Frame(self.main_frame)
        self.button_frame.grid(row=6)

        # button list (button text | bg colour | command | row | column)
        button_details_list = [
            ["Convert", "#009900", "", 0, 0],
            ["Help / Info", "#CC6600", "", 0, 1],
            ["History / Export", "#004C99", "", 0, 2]
        ]

        self.button_ref_list = []

        for item in button_details_list:
            btn = Button(self.button_frame,
                         text=item[0], bg=item[1],
                         fg="#FFFFFF", font=("Arial", "12", "bold"),
                         width=14, command=item[2])
            btn.grid(row=item[3], column=item[4], padx=5, pady=5)
            self.button_ref_list.append(btn)

        # Disable history and convert until ready
        self.convert_button = self.button_ref_list[0]
        self.convert_button.config(state=DISABLED)

        self.to_history_button = self.button_ref_list[2]
        self.to_history_button.config(state=DISABLED)

    def select_currency(self, currency):
        """
        Handles currency button selection logic.
        First click sets From, second click sets To.
        If both already selected, resets and sets new From.
        Prevents selecting same currency for both From and To.
        """

        # If both already selected, reset and start again
        if self.from_currency and self.to_currency:
            self.reset_selection()

        # If nothing selected yet, set as From
        if self.from_currency is None:
            self.from_currency = currency
            self.currency_buttons[currency].config(bg="#2D6A4F")  # green = From
            self.update_selection_label()

        # If From already selected and user picks a different currency, set as To
        elif self.to_currency is None and currency != self.from_currency:
            self.to_currency = currency
            self.currency_buttons[currency].config(bg="#004C99")  # blue = To
            self.update_selection_label()
            self.convert_button.config(state=NORMAL)

    def reset_selection(self):
        """
        Clears From / To selections and resets all button colours.
        """
        self.from_currency = None
        self.to_currency = None
        self.convert_button.config(state=DISABLED)

        # Reset all currency buttons to grey
        for btn in self.currency_buttons.values():
            btn.config(bg="#AAAAAA")

        self.update_selection_label()

    def update_selection_label(self):
        """
        Updates the From / To display label based on current selection.
        """
        from_text = self.from_currency if self.from_currency else "—"
        to_text = self.to_currency if self.to_currency else "—"
        self.selection_label.config(text=f"From: {from_text}    To: {to_text}")


# main routine
if __name__ == "__main__":
    root = Tk()
    root.title("Currency Converter")
    Converter()
    root.mainloop()