from datetime import date, timedelta

THEMES: dict[str, dict[str, str | list[str]]] = {
    "light": {
        "bg": "#ffffff",
        "text": "#24292f",
        "muted": "#57606a",
        "empty": "#ebedf0",
        "levels": ["#ebedf0", "#9be9a8", "#40c463", "#30a14e", "#216e39"],
    },
    "dark": {
        "bg": "#0d1117",
        "text": "#c9d1d9",
        "muted": "#8b949e",
        "empty": "#161b22",
        "levels": ["#161b22", "#0e4429", "#006d32", "#26a641", "#39d353"],
    },
}


def _intensity_level(value: int, max_value: int) -> int:
    if value <= 0 or max_value <= 0:
        return 0
    ratio = value / max_value
    if ratio < 0.25:
        return 1
    if ratio < 0.5:
        return 2
    if ratio < 0.75:
        return 3
    return 4


def _build_calendar_days(from_date: date, to_date: date) -> list[date]:
    days: list[date] = []
    current = from_date
    while current <= to_date:
        days.append(current)
        current += timedelta(days=1)
    return days


def render_activity_svg(
    daily_totals: dict[str, int],
    from_date: date,
    to_date: date,
    days_count: int,
    total_contributions: int,
    theme: str,
) -> str:
    palette = THEMES[theme if theme in THEMES else "light"]
    levels = palette["levels"]

    day_size = 11
    gap = 3
    left_padding = 42
    top_padding = 30
    month_label_height = 14
    grid_top = top_padding + month_label_height

    start = from_date - timedelta(days=(from_date.weekday() + 1) % 7)
    end = to_date + timedelta(days=(5 - to_date.weekday()) % 7 + 1)
    all_days = _build_calendar_days(start, end)
    week_count = max(1, len(all_days) // 7)

    grid_width = week_count * (day_size + gap)
    grid_height = 7 * (day_size + gap)
    width = left_padding + grid_width + 20
    height = grid_top + grid_height + 34

    max_value = max(daily_totals.values(), default=0)

    lines: list[str] = []
    lines.append(f'<svg xmlns="http://www.w3.org/2000/svg" width="{width}" height="{height}" role="img" aria-label="Contribution graph">')
    lines.append(f'<rect width="100%" height="100%" fill="{palette["bg"]}" />')
    lines.append(
        f'<text x="{left_padding}" y="16" fill="{palette["text"]}" font-family="-apple-system,BlinkMacSystemFont,Segoe UI,Helvetica,Arial,sans-serif" font-size="12">{total_contributions} contributions in the last {days_count} days</text>'
    )

    month_x_positions: dict[str, int] = {}
    for idx, day in enumerate(all_days):
        if day.day == 1:
            month_x_positions[day.strftime("%b")] = left_padding + (idx // 7) * (day_size + gap)
    for label, x in month_x_positions.items():
        lines.append(
            f'<text x="{x}" y="{top_padding + 10}" fill="{palette["muted"]}" font-family="-apple-system,BlinkMacSystemFont,Segoe UI,Helvetica,Arial,sans-serif" font-size="10">{label}</text>'
        )

    weekday_labels = {1: "Mon", 3: "Wed", 5: "Fri"}
    for row, label in weekday_labels.items():
        y = grid_top + row * (day_size + gap) + 9
        lines.append(
            f'<text x="8" y="{y}" fill="{palette["muted"]}" font-family="-apple-system,BlinkMacSystemFont,Segoe UI,Helvetica,Arial,sans-serif" font-size="10">{label}</text>'
        )

    for idx, day in enumerate(all_days):
        week = idx // 7
        row = (day.weekday() + 1) % 7
        x = left_padding + week * (day_size + gap)
        y = grid_top + row * (day_size + gap)

        value = daily_totals.get(day.isoformat(), 0)
        level = _intensity_level(value, max_value)
        fill = levels[level]

        lines.append(
            f'<rect x="{x}" y="{y}" width="{day_size}" height="{day_size}" rx="2" ry="2" fill="{fill}" />'
        )

    legend_y = grid_top + grid_height + 16
    legend_x = left_padding + grid_width - 120
    lines.append(
        f'<text x="{legend_x}" y="{legend_y}" fill="{palette["muted"]}" font-family="-apple-system,BlinkMacSystemFont,Segoe UI,Helvetica,Arial,sans-serif" font-size="10">Less</text>'
    )
    for i, color in enumerate(levels):
        lx = legend_x + 26 + i * (day_size + 2)
        lines.append(
            f'<rect x="{lx}" y="{legend_y - 9}" width="{day_size}" height="{day_size}" rx="2" ry="2" fill="{color}" />'
        )
    lines.append(
        f'<text x="{legend_x + 26 + len(levels) * (day_size + 2) + 4}" y="{legend_y}" fill="{palette["muted"]}" font-family="-apple-system,BlinkMacSystemFont,Segoe UI,Helvetica,Arial,sans-serif" font-size="10">More</text>'
    )

    lines.append("</svg>")
    return "".join(lines)