import { isSupported, recognizeText } from "expo-mlkit-ocr";

import { parseReceiptText, type ReceiptParseResult } from "@/lib/receipt-parse";

export type ReceiptOcrResult = ReceiptParseResult & {
  rawText: string;
};

export function mlKitOcrAvailable(): boolean {
  try {
    return isSupported();
  } catch {
    return false;
  }
}

function normalizeImageUri(uri: string): string {
  if (uri.startsWith("file://") || uri.startsWith("content://")) {
    return uri;
  }
  return `file://${uri}`;
}

/** Run on-device ML Kit OCR and parse receipt fields from recognized text. */
export async function recognizeReceiptFromImage(uri: string): Promise<ReceiptOcrResult> {
  if (!mlKitOcrAvailable()) {
    throw new Error("On-device OCR is not supported on this device.");
  }

  const result = await recognizeText(normalizeImageUri(uri));
  const rawText = result.text?.trim() ?? "";
  const parsed = parseReceiptText(rawText);

  return {
    ...parsed,
    rawText,
  };
}

export function applyReceiptOcrToForm(
  ocr: ReceiptParseResult,
  current: { description: string; amountText: string; date: Date },
): { description: string; amountText: string; date: Date; ocrText: string } {
  return {
    description: ocr.vendor?.trim() || current.description,
    amountText: ocr.amount != null ? String(ocr.amount) : current.amountText,
    date: ocr.date ?? current.date,
    ocrText: ocr.rawLines.join("\n"),
  };
}