"""Overlay Widget — transparent layer rendered above the video preview."""

from __future__ import annotations

from PySide6.QtCore import QRect, Qt, Slot
from PySide6.QtGui import QColor, QFont, QPainter, QPen
from PySide6.QtWidgets import QWidget

from app.config import (
    OVERLAY_BG_COLOR,
    OVERLAY_FONT_SIZE,
    OVERLAY_MARGIN,
    OVERLAY_PADDING,
    OVERLAY_TEXT_COLOR,
)
from app.telemetry.telemetry_collector import TelemetrySnapshot


class OverlayWidget(QWidget):
    """
    Semi-transparent performance metrics overlay.

    Sits on top of the video widget (same parent, raised).
    Does NOT intercept mouse events — clicks pass through to the video widget.

    Usage:
        overlay = OverlayWidget(parent=main_window)
        telemetry_collector.metrics_updated.connect(overlay.update_metrics)
    """

    def __init__(self, parent: QWidget | None = None) -> None:
        super().__init__(parent)

        # Make widget transparent to mouse and visual background
        self.setAttribute(Qt.WidgetAttribute.WA_TransparentForMouseEvents, True)
        self.setAttribute(Qt.WidgetAttribute.WA_NoSystemBackground, True)
        self.setAttribute(Qt.WidgetAttribute.WA_TranslucentBackground, True)
        self.setWindowFlags(Qt.WindowType.FramelessWindowHint)

        self._snapshot: TelemetrySnapshot | None = None
        self._visible_overlay: bool = True

        # Font
        self._font = QFont("Monospace")
        self._font.setStyleHint(QFont.StyleHint.TypeWriter)
        self._font.setPointSize(OVERLAY_FONT_SIZE)
        self._font.setBold(False)

    # ------------------------------------------------------------------
    # Public API
    # ------------------------------------------------------------------

    @Slot(object)
    def update_metrics(self, snapshot: TelemetrySnapshot) -> None:
        """Receive a new telemetry snapshot and trigger a repaint."""
        self._snapshot = snapshot
        if self._visible_overlay:
            self.update()

    def set_overlay_visible(self, visible: bool) -> None:
        self._visible_overlay = visible
        self.update()

    def toggle_overlay(self) -> None:
        self.set_overlay_visible(not self._visible_overlay)

    # ------------------------------------------------------------------
    # Qt painting
    # ------------------------------------------------------------------

    def paintEvent(self, event) -> None:  # noqa: N802
        if not self._visible_overlay or self._snapshot is None:
            return

        lines = self._format_lines(self._snapshot)
        if not lines:
            return

        painter = QPainter(self)
        painter.setRenderHint(QPainter.RenderHint.Antialiasing, False)
        painter.setFont(self._font)

        fm = painter.fontMetrics()
        line_height = fm.height()
        max_width = max(fm.horizontalAdvance(line) for line in lines)

        box_w = max_width + OVERLAY_PADDING * 2
        box_h = line_height * len(lines) + OVERLAY_PADDING * 2

        x = OVERLAY_MARGIN
        y = OVERLAY_MARGIN

        # Background rectangle
        bg = QColor(*OVERLAY_BG_COLOR)
        painter.setBrush(bg)
        painter.setPen(Qt.PenStyle.NoPen)
        painter.drawRoundedRect(QRect(x, y, box_w, box_h), 6, 6)

        # Text
        text_color = QColor(*OVERLAY_TEXT_COLOR)
        painter.setPen(QPen(text_color))

        text_x = x + OVERLAY_PADDING
        text_y = y + OVERLAY_PADDING + fm.ascent()

        for line in lines:
            painter.drawText(text_x, text_y, line)
            text_y += line_height

        painter.end()

    # ------------------------------------------------------------------
    # Private
    # ------------------------------------------------------------------

    @staticmethod
    def _format_lines(snap: TelemetrySnapshot) -> list[str]:
        lines = [
            f"FPS    {snap.fps:>6.1f}",
            f"Frame  {snap.frame_time_ms:>6.1f} ms",
            f"Drop   {snap.dropped_frames:>6d}",
            f"CPU    {snap.cpu_percent:>5.1f} %",
        ]
        if snap.memory_mb is not None:
            lines.append(f"Mem    {snap.memory_mb:>5.0f} MB")
        return lines