frontend/src/components/ocr/DocumentPreview.jsx

import React, { useState, useEffect, useRef } from "react";
import { motion } from "framer-motion";
import { FileText, ZoomIn, ZoomOut, RotateCw } from "lucide-react";
import { Button } from "@/components/ui/button";

export default function DocumentPreview({ file, isProcessing, isFromHistory = false }) {
  const [previewUrls, setPreviewUrls] = useState([]);
  const [zoom, setZoom] = useState(100);
  const [rotation, setRotation] = useState(0);
  const objectUrlsRef = useRef([]);

  useEffect(() => {
    if (!file) {
      // Cleanup previous URLs
      objectUrlsRef.current.forEach((url) => {
        if (url && url.startsWith("blob:")) {
          URL.revokeObjectURL(url);
        }
      });
      objectUrlsRef.current = [];
      setPreviewUrls([]);
      return;
    }

    const loadPreview = async () => {
      const urls = [];
      const newObjectUrls = [];

      // Check if it's a PDF
      if (file.type === "application/pdf" || file.name?.toLowerCase().endsWith(".pdf")) {
        try {
          // Use pdf.js to render PDF pages
          const pdfjsLib = await import("pdfjs-dist");
          
          // Configure worker - use jsdelivr CDN which is more reliable
          // This will use the same version as the installed package
          const version = pdfjsLib.version || "4.0.379";
          pdfjsLib.GlobalWorkerOptions.workerSrc = `https://cdn.jsdelivr.net/npm/pdfjs-dist@${version}/build/pdf.worker.min.mjs`;

          const arrayBuffer = await file.arrayBuffer();
          const pdf = await pdfjsLib.getDocument({ data: arrayBuffer }).promise;
          const numPages = pdf.numPages;

          for (let pageNum = 1; pageNum <= numPages; pageNum++) {
            const page = await pdf.getPage(pageNum);
            const viewport = page.getViewport({ scale: 2.0 });

            const canvas = document.createElement("canvas");
            const context = canvas.getContext("2d");
            canvas.height = viewport.height;
            canvas.width = viewport.width;

            await page.render({
              canvasContext: context,
              viewport: viewport,
            }).promise;

            urls.push(canvas.toDataURL("image/jpeg", 0.95));
          }
        } catch (error) {
          console.error("Error loading PDF:", error);
          // Fallback: show error message
          urls.push(null);
        }
      } else {
        // For images, create object URL
        const url = URL.createObjectURL(file);
        urls.push(url);
        newObjectUrls.push(url);
      }

      // Cleanup old object URLs
      objectUrlsRef.current.forEach((url) => {
        if (url && url.startsWith("blob:")) {
          URL.revokeObjectURL(url);
        }
      });
      objectUrlsRef.current = newObjectUrls;
      setPreviewUrls(urls);
    };

    loadPreview();

    // Cleanup function - revoke object URLs when component unmounts or file changes
    return () => {
      objectUrlsRef.current.forEach((url) => {
        if (url && url.startsWith("blob:")) {
          URL.revokeObjectURL(url);
        }
      });
      objectUrlsRef.current = [];
    };
  }, [file]);

  return (
    <div className="h-full flex flex-col bg-white rounded-2xl border border-slate-200 overflow-hidden">
      {/* Header */}
      <div className="flex items-center justify-between px-5 py-4 border-b border-slate-100">
        <div className="flex items-center gap-3">
          <div className="h-8 w-8 rounded-lg bg-indigo-50 flex items-center justify-center">
            <FileText className="h-4 w-4 text-indigo-600" />
          </div>
          <div>
            <h3 className="font-semibold text-slate-800 text-sm">Document Preview</h3>
            <p className="text-xs text-slate-400">{file?.name || "No file selected"}</p>
          </div>
        </div>

        {file && (
          <div className="flex items-center gap-1">
            <Button
              variant="ghost"
              size="icon"
              className="h-8 w-8 text-slate-400 hover:text-slate-600"
              onClick={() => setZoom(Math.max(50, zoom - 25))}
            >
              <ZoomOut className="h-4 w-4" />
            </Button>
            <span className="text-xs text-slate-500 w-12 text-center">{zoom}%</span>
            <Button
              variant="ghost"
              size="icon"
              className="h-8 w-8 text-slate-400 hover:text-slate-600"
              onClick={() => setZoom(Math.min(200, zoom + 25))}
            >
              <ZoomIn className="h-4 w-4" />
            </Button>
            <div className="w-px h-4 bg-slate-200 mx-2" />
            <Button
              variant="ghost"
              size="icon"
              className="h-8 w-8 text-slate-400 hover:text-slate-600"
              onClick={() => setRotation((rotation + 90) % 360)}
            >
              <RotateCw className="h-4 w-4" />
            </Button>
          </div>
        )}
      </div>

      {/* Preview Area */}
      <div className="flex-1 p-6 bg-slate-50/50 overflow-auto">
        {!file ? (
          <div className="h-full flex items-center justify-center">
            <div className="text-center">
              <div className="h-20 w-20 mx-auto rounded-2xl bg-slate-100 flex items-center justify-center mb-4">
                <FileText className="h-10 w-10 text-slate-300" />
              </div>
              <p className="text-slate-400 text-sm">Upload a document to preview</p>
            </div>
          </div>
        ) : previewUrls.length === 0 ? (
          <div className="h-full flex items-center justify-center">
            <div className="text-center">
              <div className="h-20 w-20 mx-auto rounded-2xl bg-slate-100 flex items-center justify-center mb-4">
                <FileText className="h-10 w-10 text-slate-300" />
              </div>
              <p className="text-slate-400 text-sm">Loading preview...</p>
            </div>
          </div>
        ) : (
          <div className="space-y-4">
            {previewUrls.map((url, index) => (
              <motion.div
                key={index}
                initial={{ opacity: 0, y: 20 }}
                animate={{ opacity: 1, y: 0 }}
                transition={{ delay: index * 0.1 }}
                className="relative bg-white rounded-xl shadow-sm border border-slate-200 overflow-hidden flex items-center justify-center"
                style={{
                  minHeight: "400px",
                }}
              >
                {url ? (
                  <img
                    src={url}
                    alt={`Page ${index + 1}`}
                    className="w-full h-auto"
                    style={{
                      transform: `scale(${zoom / 100}) rotate(${rotation}deg)`,
                      maxWidth: "100%",
                      objectFit: "contain",
                      transition: "transform 0.2s ease",
                    }}
                  />
                ) : (
                  <div className="p-8 text-center">
                    <p className="text-slate-400 text-sm">
                      {isFromHistory 
                        ? "Original document not available for historical extractions" 
                        : "Unable to load preview"}
                    </p>
                  </div>
                )}

                {/* Processing overlay */}
                {isProcessing && (
                  <motion.div
                    initial={{ opacity: 0 }}
                    animate={{ opacity: 1 }}
                    className="absolute inset-0 bg-indigo-600/5 backdrop-blur-[1px] pointer-events-none"
                  >
                    <motion.div
                      initial={{ top: 0 }}
                      animate={{ top: "100%" }}
                      transition={{
                        duration: 2,
                        repeat: Infinity,
                        ease: "linear",
                      }}
                      className="absolute left-0 right-0 h-1 bg-gradient-to-r from-transparent via-indigo-500 to-transparent"
                    />
                  </motion.div>
                )}

                {/* Page number */}
                {previewUrls.length > 1 && (
                  <div className="absolute bottom-3 right-3 text-xs text-slate-400 bg-white/90 px-2 py-1 rounded">
                    Page {index + 1}
                  </div>
                )}
              </motion.div>
            ))}
          </div>
        )}
      </div>
    </div>
  );
}