import { useCallback, useEffect, useRef, useState } from 'react';
import { Pressable, StyleSheet, Text, View } from 'react-native';

import { SPLAT_VIEWER_HTML, type ViewerMessage } from './viewer-html';

// expo-sensors' DeviceMotion web shim does not emit `rotation`, so on web we
// read the browser's own OS-fused attitude directly. Chrome/Android exposes
// the magnetometer-referenced fusion on `deviceorientationabsolute`; other
// browsers (incl. iOS Safari, which fuses via CoreMotion) use
// `deviceorientation`.
const ORIENTATION_EVENT =
  typeof window !== 'undefined' && 'ondeviceorientationabsolute' in window
    ? 'deviceorientationabsolute'
    : 'deviceorientation';

// iOS Safari 13+ gates motion events behind a user-gesture permission prompt.
const orientationEventStatics =
  typeof DeviceOrientationEvent !== 'undefined'
    ? (DeviceOrientationEvent as unknown as { requestPermission?: () => Promise<'granted' | 'denied'> })
    : {};

const DEG2RAD = Math.PI / 180;

/**
 * Web splat viewer host: same Spark viewer page as native, hosted in an
 * iframe and fed rotation samples via postMessage. Camera position is fixed.
 */
export function SplatViewer() {
  const frameRef = useRef<HTMLIFrameElement>(null);
  const [status, setStatus] = useState('Loading Spark renderer…');
  const [needsPermission, setNeedsPermission] = useState(false);

  const onOrientation = useCallback((event: DeviceOrientationEvent) => {
    if (event.alpha == null || event.beta == null || event.gamma == null) return;
    frameRef.current?.contentWindow?.postMessage(
      {
        type: 'rotation',
        alpha: event.alpha * DEG2RAD,
        beta: event.beta * DEG2RAD,
        gamma: event.gamma * DEG2RAD,
        orientation: (typeof screen !== 'undefined' && screen.orientation?.angle) || 0,
      },
      '*',
    );
  }, []);

  useEffect(() => {
    const onViewerMessage = (event: MessageEvent) => {
      if (event.source !== frameRef.current?.contentWindow) return;
      const message = event.data as ViewerMessage;
      switch (message?.type) {
        case 'progress':
          setStatus(`Downloading scene… ${Math.round((100 * message.loaded) / message.total)}%`);
          break;
        case 'ready':
          setStatus(`${message.numSplats.toLocaleString()} splats — rotate the device to look around, tap to re-center.`);
          break;
        case 'error':
          setStatus(`Viewer error: ${message.message}`);
          break;
      }
    };
    window.addEventListener('message', onViewerMessage);

    const listener = onOrientation as EventListener;
    if (typeof orientationEventStatics.requestPermission === 'function') {
      setNeedsPermission(true);
    } else {
      window.addEventListener(ORIENTATION_EVENT, listener);
    }
    return () => {
      window.removeEventListener('message', onViewerMessage);
      window.removeEventListener(ORIENTATION_EVENT, listener);
    };
  }, [onOrientation]);

  const requestMotionAccess = useCallback(async () => {
    try {
      const response = await orientationEventStatics.requestPermission?.();
      if (response === 'granted') {
        window.addEventListener(ORIENTATION_EVENT, onOrientation as EventListener);
        setNeedsPermission(false);
      } else {
        setStatus('Motion access denied — showing a static view.');
        setNeedsPermission(false);
      }
    } catch (error) {
      setStatus(`Motion permission failed: ${error instanceof Error ? error.message : error}`);
    }
  }, [onOrientation]);

  return (
    <View style={styles.container}>
      <iframe
        ref={frameRef}
        title="Spark splat viewer"
        srcDoc={SPLAT_VIEWER_HTML}
        style={iframeStyle}
        allow="accelerometer; gyroscope; magnetometer"
      />
      {needsPermission && (
        <Pressable style={styles.permissionButton} onPress={requestMotionAccess}>
          <Text style={styles.permissionLabel}>Enable motion control</Text>
        </Pressable>
      )}
      <Text style={styles.status}>{status}</Text>
    </View>
  );
}

const iframeStyle: React.CSSProperties = {
  position: 'absolute',
  inset: 0,
  width: '100%',
  height: '100%',
  border: 0,
  background: '#000',
};

const styles = StyleSheet.create({
  container: {
    flex: 1,
    backgroundColor: '#000',
  },
  permissionButton: {
    position: 'absolute',
    top: '45%',
    alignSelf: 'center',
    backgroundColor: 'rgba(10, 126, 164, 0.9)',
    borderRadius: 10,
    paddingVertical: 12,
    paddingHorizontal: 20,
  },
  permissionLabel: {
    color: '#fff',
    fontSize: 15,
    fontWeight: '600',
  },
  status: {
    position: 'absolute',
    bottom: 12,
    left: 12,
    right: 12,
    color: '#fff',
    fontSize: 12,
    textAlign: 'center',
    backgroundColor: 'rgba(0,0,0,0.55)',
    borderRadius: 8,
    paddingVertical: 6,
    paddingHorizontal: 10,
    overflow: 'hidden',
  },
});