import { useRef } from "react";
import { StyleSheet, View, Text, Pressable } from "react-native";
import { CameraView, useCameraPermissions } from "expo-camera";
import { theme } from "../lib/theme";

export interface QRScannerProps {
  onScan: (code: string) => void;
  active: boolean;
}

/** Native (Android/iOS) scanner using expo-camera. */
export default function QRScanner({ onScan, active }: QRScannerProps) {
  const [permission, requestPermission] = useCameraPermissions();
  const lastScan = useRef<{ code: string; at: number }>({ code: "", at: 0 });

  if (!permission) {
    return <View style={styles.fill} />;
  }
  if (!permission.granted) {
    return (
      <View style={[styles.fill, styles.center]}>
        <Text style={styles.msg}>Camera access is needed to scan tickets.</Text>
        <Pressable style={styles.btn} onPress={requestPermission}>
          <Text style={styles.btnText}>Grant camera permission</Text>
        </Pressable>
      </View>
    );
  }

  return (
    <CameraView
      style={styles.fill}
      facing="back"
      barcodeScannerSettings={{ barcodeTypes: ["qr"] }}
      onBarcodeScanned={
        active
          ? ({ data }) => {
              const now = Date.now();
              // Debounce repeated frames of the same code.
              if (data === lastScan.current.code && now - lastScan.current.at < 3000) return;
              lastScan.current = { code: data, at: now };
              onScan(data);
            }
          : undefined
      }
    />
  );
}

const styles = StyleSheet.create({
  fill: { flex: 1, width: "100%", height: "100%" },
  center: { alignItems: "center", justifyContent: "center", padding: 24, backgroundColor: theme.bg },
  msg: { color: theme.text, fontSize: 16, textAlign: "center", marginBottom: 20 },
  btn: { backgroundColor: theme.primary, paddingHorizontal: 20, paddingVertical: 12, borderRadius: 10 },
  btnText: { color: "#fff", fontSize: 16, fontWeight: "600" },
});