import React, { useState, useEffect } from "react";
import { motion, AnimatePresence } from "framer-motion";
import { Upload, FileText, Image, FileSpreadsheet, X, Sparkles, AlertCircle } from "lucide-react";
import { cn } from "@/lib/utils";
import { Input } from "@/components/ui/input";

// Allowed file types
const ALLOWED_TYPES = [
  "application/pdf",
  "image/png",
  "image/jpeg",
  "image/jpg",
  "image/tiff",
  "image/tif"
];

// Allowed file extensions (for fallback validation)
const ALLOWED_EXTENSIONS = [".pdf", ".png", ".jpg", ".jpeg", ".tiff", ".tif"];

// Maximum file size: 4 MB
const MAX_FILE_SIZE = 4 * 1024 * 1024; // 4 MB in bytes

export default function UploadZone({ onFileSelect, selectedFile, onClear, keyFields = "", onKeyFieldsChange = () => {} }) {
  const [isDragging, setIsDragging] = useState(false);
  const [error, setError] = useState(null);

  const validateFile = (file) => {
    // Reset error
    setError(null);

    // Check file type
    const fileExtension = "." + file.name.split(".").pop().toLowerCase();
    const isValidType = ALLOWED_TYPES.includes(file.type) || ALLOWED_EXTENSIONS.includes(fileExtension);
    
    if (!isValidType) {
      setError("Only PDF, PNG, JPG, and TIFF files are allowed.");
      return false;
    }

    // Check file size
    if (file.size > MAX_FILE_SIZE) {
      const fileSizeMB = (file.size / 1024 / 1024).toFixed(2);
      setError(`File size exceeds 4 MB limit. Your file is ${fileSizeMB} MB.`);
      return false;
    }

    return true;
  };

  const handleFileSelect = (file) => {
    if (validateFile(file)) {
      setError(null);
      onFileSelect(file);
    }
  };

  const handleDragOver = (e) => {
    e.preventDefault();
    setIsDragging(true);
  };

  const handleDragLeave = () => {
    setIsDragging(false);
  };

  const handleDrop = (e) => {
    e.preventDefault();
    setIsDragging(false);
    const file = e.dataTransfer.files[0];
    if (file) {
      handleFileSelect(file);
    }
  };

  const getFileIcon = (type) => {
    if (type?.includes("image")) return Image;
    if (type?.includes("spreadsheet") || type?.includes("excel")) return FileSpreadsheet;
    return FileText;
  };

  const FileIcon = selectedFile ? getFileIcon(selectedFile.type) : FileText;

  // Clear error when file is cleared
  useEffect(() => {
    if (!selectedFile) {
      setError(null);
    }
  }, [selectedFile]);

  return (
    <div className="w-full">
      <AnimatePresence mode="wait">
        {!selectedFile ? (
          <motion.div
            key="upload"
            initial={{ opacity: 0, y: 10 }}
            animate={{ opacity: 1, y: 0 }}
            exit={{ opacity: 0, y: -10 }}
            transition={{ duration: 0.2 }}
            onDragOver={handleDragOver}
            onDragLeave={handleDragLeave}
            onDrop={handleDrop}
            className={cn(
              "relative group cursor-pointer",
              "border-2 border-dashed rounded-2xl",
              "transition-all duration-300 ease-out",
              isDragging
                ? "border-indigo-400 bg-indigo-50/50"
                : "border-slate-200 hover:border-indigo-300 hover:bg-slate-50/50"
            )}
          >
            <label className="flex flex-col items-center justify-center py-16 px-8 cursor-pointer">
              <motion.div
                animate={isDragging ? { scale: 1.1, y: -5 } : { scale: 1, y: 0 }}
                className={cn(
                  "h-16 w-16 rounded-2xl flex items-center justify-center mb-6 transition-colors duration-300",
                  isDragging
                    ? "bg-indigo-100"
                    : "bg-gradient-to-br from-slate-100 to-slate-50 group-hover:from-indigo-100 group-hover:to-violet-50"
                )}
              >
                <Upload
                  className={cn(
                    "h-7 w-7 transition-colors duration-300",
                    isDragging ? "text-indigo-600" : "text-slate-400 group-hover:text-indigo-500"
                  )}
                />
              </motion.div>

              <div className="text-center">
                <p className="text-lg font-semibold text-slate-700 mb-1">
                  {isDragging ? "Drop your file here" : "Drop your file here, or browse"}
                </p>
                <p className="text-sm text-slate-400">
                  Supports PDF, PNG, JPG, TIFF up to 4MB
                </p>
              </div>

              <div className="flex items-center gap-2 mt-6">
                <div className="flex -space-x-1">
                  {[
                    "bg-red-100 text-red-600",
                    "bg-blue-100 text-blue-600",
                    "bg-green-100 text-green-600",
                    "bg-amber-100 text-amber-600",
                  ].map((color, i) => (
                    <div
                      key={i}
                      className={`h-8 w-8 rounded-lg ${color.split(" ")[0]} flex items-center justify-center border-2 border-white`}
                    >
                      <FileText className={`h-4 w-4 ${color.split(" ")[1]}`} />
                    </div>
                  ))}
                </div>
                <span className="text-xs text-slate-400 ml-2">Multiple formats supported</span>
              </div>

              <input
                type="file"
                className="hidden"
                accept=".pdf,.png,.jpg,.jpeg,.tiff,.tif"
                onChange={(e) => {
                  const file = e.target.files[0];
                  if (file) {
                    handleFileSelect(file);
                  }
                  // Reset input so same file can be selected again after error
                  e.target.value = "";
                }}
              />
            </label>

            {/* Decorative gradient border on hover */}
            <div className="absolute inset-0 -z-10 rounded-2xl bg-gradient-to-r from-indigo-500 via-violet-500 to-purple-500 opacity-0 group-hover:opacity-10 blur-xl transition-opacity duration-500" />
          </motion.div>
        ) : (
          <motion.div
            key="selected"
            initial={{ opacity: 0, scale: 0.95 }}
            animate={{ opacity: 1, scale: 1 }}
            exit={{ opacity: 0, scale: 0.95 }}
            className="grid grid-cols-1 lg:grid-cols-2 gap-3"
          >
            {/* File Info Box */}
            <div className="relative bg-gradient-to-br from-indigo-50 to-violet-50 rounded-xl p-3 border border-indigo-100">
              <div className="flex items-center gap-3">
                <div className="h-10 w-10 rounded-lg bg-white shadow-sm flex items-center justify-center flex-shrink-0">
                  <FileIcon className="h-5 w-5 text-indigo-600" />
                </div>
                <div className="flex-1 min-w-0">
                  <p className="font-medium text-slate-800 truncate text-sm">{selectedFile.name}</p>
                  <div className="flex items-center gap-2 text-xs text-slate-500">
                    <span>{(selectedFile.size / 1024 / 1024).toFixed(2)} MB</span>
                    <span className="text-indigo-500">•</span>
                    <span className="text-indigo-600 flex items-center gap-1">
                      <Sparkles className="h-3 w-3" />
                      Ready for extraction
                    </span>
                  </div>
                </div>
                <button
                  onClick={onClear}
                  className="h-8 w-8 rounded-lg bg-white hover:bg-red-50 border border-slate-200 hover:border-red-200 flex items-center justify-center text-slate-400 hover:text-red-500 transition-colors"
                >
                  <X className="h-4 w-4" />
                </button>
              </div>
            </div>

            {/* Key Fields Box */}
            <div className="relative bg-white rounded-xl p-3 border border-slate-200">
              <label className="block text-xs font-medium text-slate-600 mb-1.5">
                <span className="font-bold">Key Fields</span> <span className="font-normal">(if required)</span>
              </label>
              <Input
                type="text"
                value={keyFields || ""}
                onChange={(e) => {
                  if (onKeyFieldsChange) {
                    onKeyFieldsChange(e.target.value);
                  }
                }}
                placeholder="Invoice Number, Invoice Date, PO Number, Supplier Name, Total Amount, Payment terms, Additional Notes"
                className="h-8 text-xs border-slate-200 focus:border-indigo-300 focus:ring-indigo-200"
              />
            </div>
          </motion.div>
        )}
      </AnimatePresence>
      
      {/* Error Message */}
      {error && (
        <motion.div
          initial={{ opacity: 0, y: -10 }}
          animate={{ opacity: 1, y: 0 }}
          exit={{ opacity: 0, y: -10 }}
          className="mt-3 p-3 bg-red-50 border border-red-200 rounded-xl flex items-start gap-2"
        >
          <AlertCircle className="h-4 w-4 text-red-600 flex-shrink-0 mt-0.5" />
          <p className="text-sm text-red-700 flex-1">{error}</p>
          <button
            onClick={() => setError(null)}
            className="text-red-600 hover:text-red-800 transition-colors"
          >
            <X className="h-4 w-4" />
          </button>
        </motion.div>
      )}
    </div>
  );
}