"""
Null/headless display backend.
"""

import time


class NullDisplay:
    """Headless/null display - discards all output.

    This display does nothing - useful for headless benchmarking
    or when no display output is needed. Captures last buffer
    for testing purposes.
    """

    width: int = 80
    height: int = 24
    _last_buffer: list[str] | None = None

    def __init__(self):
        self._last_buffer = None

    def init(self, width: int, height: int, reuse: bool = False) -> None:
        """Initialize display with dimensions.

        Args:
            width: Terminal width in characters
            height: Terminal height in rows
            reuse: Ignored for NullDisplay (no resources to reuse)
        """
        self.width = width
        self.height = height
        self._last_buffer = None

    def show(self, buffer: list[str], border: bool = False) -> None:
        from engine.display import get_monitor, render_border

        # Get FPS for border (if available)
        fps = 0.0
        frame_time = 0.0
        monitor = get_monitor()
        if monitor:
            stats = monitor.get_stats()
            avg_ms = stats.get("pipeline", {}).get("avg_ms", 0) if stats else 0
            frame_count = stats.get("frame_count", 0) if stats else 0
            if avg_ms and frame_count > 0:
                fps = 1000.0 / avg_ms
                frame_time = avg_ms

        # Apply border if requested (same as terminal display)
        if border:
            buffer = render_border(buffer, self.width, self.height, fps, frame_time)

        self._last_buffer = buffer
        if monitor:
            t0 = time.perf_counter()
            chars_in = sum(len(line) for line in buffer)
            elapsed_ms = (time.perf_counter() - t0) * 1000
            monitor.record_effect("null_display", elapsed_ms, chars_in, chars_in)

    def clear(self) -> None:
        pass

    def cleanup(self) -> None:
        pass

    def get_dimensions(self) -> tuple[int, int]:
        """Get current dimensions.

        Returns:
            (width, height) in character cells
        """
        return (self.width, self.height)

    def is_quit_requested(self) -> bool:
        """Check if quit was requested (optional protocol method)."""
        return False

    def clear_quit_request(self) -> None:
        """Clear quit request (optional protocol method)."""
        pass