presets.py

"""Output size presets and resolution handling."""

from dataclasses import dataclass

MAX_PIXELS_PER_SIDE = 12000
DEFAULT_DPI = 300
DEFAULT_WIDTH_IN = 12.0
DEFAULT_HEIGHT_IN = 16.0

# name: (width_px, height_px) at DEFAULT_DPI
PRESETS = {
    "mobile": (1080, 1920),
    "hd": (1920, 1080),
    "4k": (3840, 2160),
    "4k-portrait": (2160, 3840),
    "square": (2048, 2048),
    "instagram-post": (1080, 1350),
    "instagram-story": (1080, 1920),
    "a4": (2480, 3508),
    "a3": (3508, 4961),
    "a2": (4961, 7016),
    "18x24": (5400, 7200),
    "24x36": (7200, 10800),
}


@dataclass(frozen=True)
class SizeSpec:
    """Resolved output size. exact_pixels=True means save without tight bbox."""

    width_in: float
    height_in: float
    dpi: int
    exact_pixels: bool


def parse_pixels(value: str) -> tuple[int, int]:
    """Parse a 'WIDTHxHEIGHT' pixel string, e.g. '1920x1080'."""
    parts = value.lower().replace("×", "x").split("x")
    if len(parts) != 2:
        raise ValueError(
            f"Invalid --pixels value '{value}'. Expected WIDTHxHEIGHT, e.g. 1920x1080."
        )
    try:
        width, height = int(parts[0]), int(parts[1])
    except ValueError as exc:
        raise ValueError(
            f"Invalid --pixels value '{value}'. Expected WIDTHxHEIGHT, e.g. 1920x1080."
        ) from exc
    if width <= 0 or height <= 0:
        raise ValueError(f"--pixels dimensions must be positive, got '{value}'.")
    return width, height


def _apply_orientation(width, height, orientation):
    if orientation == "portrait" and width > height:
        return height, width
    if orientation == "landscape" and height > width:
        return height, width
    return width, height


def resolve_size(
    preset=None,
    pixels=None,
    width_in=DEFAULT_WIDTH_IN,
    height_in=DEFAULT_HEIGHT_IN,
    dpi=DEFAULT_DPI,
    orientation=None,
) -> SizeSpec:
    """Resolve output size. Precedence: pixels > preset > explicit inches."""
    if pixels:
        px_w, px_h = parse_pixels(pixels)
    elif preset:
        if preset not in PRESETS:
            raise ValueError(
                f"Unknown preset '{preset}'. Available: {', '.join(sorted(PRESETS))}"
            )
        px_w, px_h = PRESETS[preset]
    else:
        w, h = _apply_orientation(width_in, height_in, orientation)
        return SizeSpec(w, h, dpi, exact_pixels=False)

    px_w, px_h = _apply_orientation(px_w, px_h, orientation)
    if px_w > MAX_PIXELS_PER_SIDE or px_h > MAX_PIXELS_PER_SIDE:
        raise ValueError(
            f"Pixel size {px_w}x{px_h} exceeds the maximum of {MAX_PIXELS_PER_SIDE} px per side."
        )
    return SizeSpec(px_w / dpi, px_h / dpi, dpi, exact_pixels=True)