from flask import current_app
from flask_login import current_user


def format_currency(amount, symbol=None, show_sign=False):
    """Format a number as currency using the app's configured symbol."""
    if amount is None:
        return '—'
    try:
        amount = float(amount)
    except (TypeError, ValueError):
        return '—'

    if symbol is None:
        try:
            symbol = current_user.currency_symbol if current_user.is_authenticated \
                else current_app.config.get('APP_CURRENCY_SYMBOL', '$')
        except Exception:
            symbol = '$'

    formatted = f"{symbol}{abs(amount):,.2f}"
    if show_sign:
        if amount < 0:
            formatted = f"-{formatted}"
        elif amount > 0:
            formatted = f"+{formatted}"
    elif amount < 0:
        formatted = f"-{formatted}"
    return formatted


def format_percent(value, decimals=1):
    if value is None:
        return '—'
    return f"{float(value):.{decimals}f}%"


def format_large_number(value):
    """Abbreviate large numbers: 1,500,000 → 1.5M"""
    if value is None:
        return '—'
    value = float(value)
    if abs(value) >= 1_000_000:
        return f"{value / 1_000_000:.1f}M"
    if abs(value) >= 1_000:
        return f"{value / 1_000:.1f}K"
    return f"{value:.2f}"