Devicemeasurements.tsx

import { Dimensions, Platform, PixelRatio } from 'react-native';
import * as Device from 'expo-device';

interface DeviceSpec {
  model: string;
  widthMM: number;
  screenWidthDP: number;
}

// Your original catalog — unchanged
const DEVICE_CATALOG: DeviceSpec[] = [
  // (your full list exactly as provided)
  // --- iPhone models ---
  { model: 'iPhone 15 Pro Max', widthMM: 76.7, screenWidthDP: 430 },
  { model: 'iPhone 15 Pro', widthMM: 70.6, screenWidthDP: 393 },
  // ... rest of your catalog ...
];

const FALLBACK_DEVICE: DeviceSpec = {
  model: 'Fallback',
  widthMM: 71.5,      // e.g., iPhone 13
  screenWidthDP: 390,
};

function findDeviceSpec(): { spec: DeviceSpec; isFallback: boolean } {
  const runtimeModel = (Device.modelName || '').trim();
  if (!runtimeModel) {
    return { spec: FALLBACK_DEVICE, isFallback: true };
  }

  const cleanRuntime = runtimeModel.toLowerCase();

  for (const spec of DEVICE_CATALOG) {
    const catalogModel = spec.model.toLowerCase();
    if (cleanRuntime.includes(catalogModel) || catalogModel.includes(cleanRuntime)) {
      return { spec, isFallback: false };
    }
  }

  return { spec: FALLBACK_DEVICE, isFallback: true };
}

// NEW: Apply empirical calibration only to fallback
const FALLBACK_MM_OFFSET = 1.0; // +1 mm to correct consistent error

export function mmToPx(mm: number): number {
  if (Platform.OS === 'web') {
    return (mm / 25.4) * 96;
  }

  const { spec, isFallback } = findDeviceSpec();
  let adjustedMM = mm;
  if (isFallback) {
    adjustedMM += FALLBACK_MM_OFFSET; // compensate for known –1mm bias
  }

  const percentageOfWidth = adjustedMM / spec.widthMM;
  return percentageOfWidth * spec.screenWidthDP;
}

export function pxToMM(px: number): number {
  if (Platform.OS === 'web') {
    return (px * 25.4) / 96;
  }

  const { spec, isFallback } = findDeviceSpec();
  const percentageOfScreen = px / spec.screenWidthDP;
  let mm = percentageOfScreen * spec.widthMM;

  if (isFallback) {
    mm -= FALLBACK_MM_OFFSET; // reverse the offset
  }

  return mm;
}

export function getPhysicalScreenWidth(): number {
  const { spec, isFallback } = findDeviceSpec();
  let width = spec.widthMM;
  if (isFallback) {
    width += FALLBACK_MM_OFFSET;
  }
  return width;
}