from __future__ import annotations

from datetime import datetime, timezone
from typing import Any

from fastapi.templating import Jinja2Templates


def format_datetime(value: Any) -> str:
    """Render datetime values consistently for templates."""
    if not isinstance(value, datetime):
        return ""
    if value.tzinfo is None:
        value = value.replace(tzinfo=timezone.utc)
    return value.strftime("%Y-%m-%d %H:%M UTC")


def currency_display(value: Any, currency_code: str | None) -> str:
    """Format numeric values with currency context."""
    if value is None:
        return "—"
    if isinstance(value, (int, float)):
        formatted_value = f"{value:,.2f}"
    else:
        formatted_value = str(value)
    if currency_code:
        return f"{currency_code} {formatted_value}"
    return formatted_value


def format_metric(value: Any, metric_name: str, currency_code: str | None = None) -> str:
    """Format metrics according to their semantic type."""
    if value is None:
        return "—"

    currency_metrics = {
        "npv",
        "inflows",
        "outflows",
        "net",
        "total_inflows",
        "total_outflows",
        "total_net",
    }
    if metric_name in currency_metrics and currency_code:
        return currency_display(value, currency_code)

    percentage_metrics = {"irr", "payback_period"}
    if metric_name in percentage_metrics:
        if isinstance(value, (int, float)):
            return f"{value:.2f}%"
        return f"{value}%"

    if isinstance(value, (int, float)):
        return f"{value:,.2f}"

    return str(value)


def percentage_display(value: Any) -> str:
    """Format numeric values as percentages."""
    if value is None:
        return "—"
    if isinstance(value, (int, float)):
        return f"{value:.2f}%"
    return f"{value}%"


def period_display(value: Any) -> str:
    """Format period values in years."""
    if value is None:
        return "—"
    if isinstance(value, (int, float)):
        if value == int(value):
            return f"{int(value)} years"
        return f"{value:.1f} years"
    return str(value)


def register_common_filters(templates: Jinja2Templates) -> None:
    templates.env.filters["format_datetime"] = format_datetime
    templates.env.filters["currency_display"] = currency_display
    templates.env.filters["format_metric"] = format_metric
    templates.env.filters["percentage_display"] = percentage_display
    templates.env.filters["period_display"] = period_display


__all__ = [
    "format_datetime",
    "currency_display",
    "format_metric",
    "percentage_display",
    "period_display",
    "register_common_filters",
]