import React, { useState, useMemo, useRef } from "react";
import { IFileUploadSetting, IFileUploadField } from "@edr/types/freight";
import {
  UploadCloud,
  FileText,
  Image as ImageIcon,
  File,
  Trash2,
  AlertCircle,
  CheckCircle2,
} from "lucide-react";
import { cn } from "../../lib/utils";
import { Button } from "../button";

export interface SmartFileInputProps {
  /** The settings object containing features and their upload fields config. */
  file: IFileUploadSetting;
  /** Controlled value: maps each fileKey to the selected File or File[]. */
  value?: Record<string, File | File[] | null>;
  /** Callback triggered when any field's files change. */
  onChange?: (value: Record<string, File | File[] | null>) => void;
  /** External form errors mapped by fileKey. */
  errors?: Record<string, string>;
  /**
   * fileKeys whose document is already uploaded on the server. Such fields show
   * an "Already uploaded" badge and a replace-oriented dropzone hint, even when
   * no in-memory File is currently selected for them.
   */
  uploadedKeys?: string[];
  /** Disabled state for the entire file input group. */
  disabled?: boolean;
  /** Display variant style. Default is "default" (large dropzone). Minimal renders a compact upload button. */
  variant?: "default" | "minimal";
  /** Optional custom container CSS classes. */
  className?: string;

  containerClassName?: string;
}

/** Helper to format file sizes in bytes to a human-readable string. */
function formatBytes(bytes: number, decimals = 2) {
  if (bytes === 0) return "0 Bytes";
  const k = 1024;
  const dm = decimals < 0 ? 0 : decimals;
  const sizes = ["Bytes", "KB", "MB", "GB"];
  const i = Math.floor(Math.log(bytes) / Math.log(k));
  return parseFloat((bytes / Math.pow(k, i)).toFixed(dm)) + " " + sizes[i];
}

/** Render a suitable icon based on file extension. */
function FileIcon({ name, className }: { name: string; className?: string }) {
  const ext = name.split(".").pop()?.toLowerCase() || "";

  if (ext === "pdf") {
    return <FileText className={cn("text-red-500", className)} />;
  }

  if (["png", "jpg", "jpeg", "webp", "svg", "gif"].includes(ext)) {
    return <ImageIcon className={cn("text-blue-500", className)} />;
  }

  if (["csv", "xls", "xlsx"].includes(ext)) {
    return <FileText className={cn("text-emerald-500", className)} />;
  }

  if (["zip", "rar", "tar", "gz", "7z"].includes(ext)) {
    return <File className={cn("text-amber-500", className)} />;
  }

  return <File className={cn("text-slate-400", className)} />;
}

export function SmartFileInput({
  file,
  value,
  onChange,
  errors,
  uploadedKeys,
  disabled = false,
  variant = "default",
  className,
  containerClassName,
}: SmartFileInputProps) {
  // Local state to manage files when the component is used in an uncontrolled manner
  const [internalFiles, setInternalFiles] = useState<Record<string, File[]>>(
    {},
  );

  // Local validation errors
  const [localErrors, setLocalErrors] = useState<Record<string, string>>({});

  // Drag-and-drop state active per field
  const [dragActive, setDragActive] = useState<Record<string, boolean>>({});

  // File input refs for programmatic clicks in minimal variant
  const fileInputRefs = useRef<Record<string, HTMLInputElement | null>>({});

  // Memoize fields sorted by the order property (ascending)
  const sortedFields = useMemo(() => {
    return [...file.fields].sort((a, b) => a.order - b.order);
  }, [file.fields]);

  // Create a map of fields for quick lookup
  const fieldsMap = useMemo(() => {
    return file.fields.reduce(
      (acc, currentField) => {
        acc[currentField.fileKey] = currentField;
        return acc;
      },
      {} as Record<string, IFileUploadField>,
    );
  }, [file.fields]);

  // Resolve current files list for a field
  const getFilesForField = (fieldKey: string): File[] => {
    const val = value ? value[fieldKey] : internalFiles[fieldKey];
    if (!val) return [];
    return Array.isArray(val) ? val : [val];
  };

  const handleFilesChange = (fieldKey: string, newFiles: File[]) => {
    const field = fieldsMap[fieldKey];
    if (!field) return;

    const newValue = field.isMultiple ? newFiles : newFiles[0] || null;

    if (onChange) {
      const updatedValues = {
        ...(value || {}),
        [fieldKey]: newValue,
      };
      onChange(updatedValues);
    } else {
      setInternalFiles((prev) => ({
        ...prev,
        [fieldKey]: newFiles,
      }));
    }
  };

  const processFiles = (field: IFileUploadField, incomingFiles: File[]) => {
    const currentFiles = getFilesForField(field.fileKey);
    const maxAllowed = field.isMultiple ? Math.max(1, field.maxFiles) : 1;

    // Clean up extensions (e.g. '.pdf' or 'pdf' -> 'pdf')
    const allowedExts = field.allowedExtensions.map((ext) =>
      ext.toLowerCase().replace(/^\./, ""),
    );

    let validIncoming: File[] = [];
    let errorMsg = "";

    for (const fileObj of incomingFiles) {
      const ext = fileObj.name.split(".").pop()?.toLowerCase() || "";
      const isExtValid = allowedExts.length === 0 || allowedExts.includes(ext);
      const isSizeValid = fileObj.size <= field.maxSizeMb * 1024 * 1024;

      if (!isExtValid) {
        errorMsg = `Invalid file extension. Allowed: ${field.allowedExtensions.join(
          ", ",
        )}`;
        break;
      }

      if (!isSizeValid) {
        errorMsg = `File size exceeds the limit of ${field.maxSizeMb}MB`;
        break;
      }

      validIncoming.push(fileObj);
    }

    if (errorMsg) {
      setLocalErrors((prev) => ({ ...prev, [field.fileKey]: errorMsg }));
      return;
    }

    // Clear local error on successful file addition
    setLocalErrors((prev) => {
      const updated = { ...prev };
      delete updated[field.fileKey];
      return updated;
    });

    let newFilesList: File[] = [];
    if (field.isMultiple) {
      newFilesList = [...currentFiles, ...validIncoming].slice(0, maxAllowed);
      if (currentFiles.length + validIncoming.length > maxAllowed) {
        setLocalErrors((prev) => ({
          ...prev,
          [field.fileKey]: `Only up to ${maxAllowed} files are allowed for this field. Excess files were ignored.`,
        }));
      }
    } else {
      newFilesList = validIncoming.slice(0, 1);
    }

    handleFilesChange(field.fileKey, newFilesList);
  };

  const handleDrag = (
    e: React.DragEvent,
    fieldKey: string,
    active: boolean,
  ) => {
    e.preventDefault();
    e.stopPropagation();
    if (disabled) return;
    setDragActive((prev) => ({ ...prev, [fieldKey]: active }));
  };

  const handleDrop = (e: React.DragEvent, field: IFileUploadField) => {
    e.preventDefault();
    e.stopPropagation();
    if (disabled) return;
    setDragActive((prev) => ({ ...prev, [field.fileKey]: false }));

    if (e.dataTransfer.files && e.dataTransfer.files.length > 0) {
      const filesArray = Array.from(e.dataTransfer.files);
      processFiles(field, filesArray);
    }
  };

  const handleFileSelect = (
    e: React.ChangeEvent<HTMLInputElement>,
    field: IFileUploadField,
  ) => {
    if (e.target.files && e.target.files.length > 0) {
      const filesArray = Array.from(e.target.files);
      processFiles(field, filesArray);
      e.target.value = ""; // reset so same file can be selected again
    }
  };

  const removeFile = (fieldKey: string, indexToRemove: number) => {
    if (disabled) return;
    const currentFiles = getFilesForField(fieldKey);
    const updatedFiles = currentFiles.filter((_, idx) => idx !== indexToRemove);

    const field = fieldsMap[fieldKey];
    if (field && field.isRequired && updatedFiles.length === 0) {
      setLocalErrors((prev) => ({
        ...prev,
        [fieldKey]: "This file is required",
      }));
    } else {
      setLocalErrors((prev) => {
        const updated = { ...prev };
        delete updated[fieldKey];
        return updated;
      });
    }

    handleFilesChange(fieldKey, updatedFiles);
  };

  return (
    <div className={cn("flex flex-col gap-6", className)}>
      {file.description && (
        <div className="text-sm text-muted-foreground border-b border-border pb-3">
          {file.description}
        </div>
      )}

      <div className={cn("flex flex-col gap-6", containerClassName)}>
        {sortedFields.map((field) => {
          const currentFiles = getFilesForField(field.fileKey);
          const maxFiles = field.isMultiple ? Math.max(1, field.maxFiles) : 1;
          const reachedLimit = currentFiles.length >= maxFiles;
          const fieldError =
            errors?.[field.fileKey] || localErrors[field.fileKey];
          const isDragOver = dragActive[field.fileKey];
          // Already uploaded server-side and nothing newly picked to replace it.
          const isUploaded =
            (uploadedKeys?.includes(field.fileKey) ?? false) &&
            currentFiles.length === 0;

          // Format accepted files for the HTML input element
          const acceptString = field.allowedExtensions
            .map((ext) => (ext.startsWith(".") ? ext : `.${ext}`))
            .join(",");

          return (
            <div
              key={field.id || field.fileKey}
              className="flex flex-col gap-2"
            >
              {/* Field Header */}
              <div className="flex flex-col md:flex-row md:items-baseline justify-between gap-1">
                <label className="text-sm font-semibold text-foreground flex items-center gap-1.5">
                  <span className="flex items-center gap-1">
                    {field.fileLabel}
                    {field.isRequired && (
                      <span
                        className="text-destructive font-bold"
                        aria-hidden="true"
                      >
                        *
                      </span>
                    )}
                  </span>
                  {isUploaded && (
                    <span className="inline-flex items-center gap-1 rounded-full bg-emerald-50 px-2 py-0.5 text-[11px] font-medium text-emerald-600 dark:bg-emerald-500/10 dark:text-emerald-400">
                      <CheckCircle2 className="h-3 w-3" /> Already uploaded
                    </span>
                  )}
                </label>

                <span className="text-xs text-muted-foreground">
                  Max size: {field.maxSizeMb}MB
                  {field.isMultiple &&
                    ` • Files: ${currentFiles.length}/${maxFiles}`}
                </span>
              </div>

              {/* Help / Description Text */}
              {field.helpText && (
                <p className="text-xs text-muted-foreground">
                  {field.helpText}
                </p>
              )}

              {/* Selected Files List */}
              {currentFiles.length > 0 && (
                <div className="flex flex-col gap-2">
                  {currentFiles.map((fileObj, idx) => (
                    <div
                      key={`${fileObj.name}-${idx}`}
                      className={cn(
                        "flex items-center justify-between p-3 rounded-lg border bg-card transition shadow-2xs hover:shadow-xs",
                        fieldError ? "border-destructive/30" : "border-border",
                      )}
                    >
                      <div className="flex items-center gap-3 min-w-0">
                        <div className="p-2 bg-muted rounded-md flex items-center justify-center">
                          <FileIcon name={fileObj.name} className="h-5 w-5" />
                        </div>

                        <div className="min-w-0">
                          <p
                            className="text-sm font-medium text-foreground truncate max-w-[200px] md:max-w-md"
                            title={fileObj.name}
                          >
                            {fileObj.name}
                          </p>
                          <div className="flex items-center gap-2 mt-0.5">
                            <span className="text-xs text-muted-foreground">
                              {formatBytes(fileObj.size)}
                            </span>
                            <span className="flex items-center gap-0.5 text-xs text-primary font-medium">
                              <CheckCircle2 className="h-3 w-3" /> Ready
                            </span>
                          </div>
                        </div>
                      </div>

                      <button
                        type="button"
                        disabled={disabled}
                        onClick={() => removeFile(field.fileKey, idx)}
                        className={cn(
                          "p-1.5 rounded-md text-muted-foreground hover:text-destructive hover:bg-destructive/10 transition-colors",
                          disabled && "opacity-50 pointer-events-none",
                        )}
                        aria-label={`Remove file ${fileObj.name}`}
                      >
                        <Trash2 className="h-4 w-4" />
                      </button>

                      {/* Hidden inputs to represent file details in traditional form submissions */}
                      <input
                        type="hidden"
                        name={
                          field.isMultiple
                            ? `${field.fileKey}[]`
                            : field.fileKey
                        }
                        value={fileObj.name}
                      />
                    </div>
                  ))}
                </div>
              )}

              {/* Dropzone area */}
              {!reachedLimit &&
                (variant === "minimal" ? (
                  <div className="flex flex-wrap items-center gap-3">
                    <Button
                      type="button"
                      variant="outline"
                      size="sm"
                      disabled={disabled}
                      onClick={() =>
                        fileInputRefs.current[field.fileKey]?.click()
                      }
                      className="gap-1.5 cursor-pointer"
                    >
                      <UploadCloud className="h-4 w-4 text-muted-foreground" />
                      <span>{isUploaded ? "Replace File" : "Upload File"}</span>
                    </Button>
                    <input
                      type="file"
                      ref={(el) => {
                        if (fileInputRefs.current) {
                          fileInputRefs.current[field.fileKey] = el;
                        }
                      }}
                      multiple={field.isMultiple}
                      accept={acceptString}
                      disabled={disabled}
                      onChange={(e) => handleFileSelect(e, field)}
                      className="hidden"
                    />
                    <span className="text-xs text-muted-foreground">
                      Accepts:{" "}
                      {field.allowedExtensions.join(", ").toUpperCase() ||
                        "All"}
                    </span>
                  </div>
                ) : isUploaded ? (
                  // Uploaded state: a solid success panel that still doubles as a
                  // replace target (click anywhere or drag a new file onto it).
                  <div
                    onDragOver={(e) => handleDrag(e, field.fileKey, true)}
                    onDragLeave={(e) => handleDrag(e, field.fileKey, false)}
                    onDrop={(e) => handleDrop(e, field)}
                    className={cn(
                      "group relative flex items-center gap-4 rounded-lg border p-4 transition-all",
                      isDragOver
                        ? "border-2 border-dashed border-primary bg-primary/5 dark:bg-primary/10"
                        : "border-emerald-300/70 bg-emerald-50/60 dark:border-emerald-500/30 dark:bg-emerald-500/10",
                      disabled &&
                      "opacity-50 pointer-events-none cursor-not-allowed",
                    )}
                  >
                    <input
                      type="file"
                      multiple={field.isMultiple}
                      accept={acceptString}
                      disabled={disabled}
                      onChange={(e) => handleFileSelect(e, field)}
                      id={`file-input-${field.fileKey}`}
                      className="absolute inset-0 w-full h-full opacity-0 cursor-pointer disabled:cursor-not-allowed"
                      aria-label={`Replace ${field.fileLabel}`}
                    />

                    <div className="flex h-10 w-10 shrink-0 items-center justify-center rounded-full bg-emerald-100 text-emerald-600 dark:bg-emerald-500/20 dark:text-emerald-400">
                      {isDragOver ? (
                        <UploadCloud className="h-5 w-5 animate-bounce" />
                      ) : (
                        <CheckCircle2 className="h-5 w-5" />
                      )}
                    </div>

                    <div className="min-w-0 flex-1">
                      <p className="text-sm font-semibold text-foreground">
                        {isDragOver ? "Drop to replace" : "Document uploaded"}
                      </p>
                      <p className="mt-0.5 text-xs text-muted-foreground">
                        {isDragOver
                          ? "Release to replace the document on file."
                          : "Saved to your application. Drag a new file here or click to replace it."}
                      </p>
                    </div>

                    <span className="hidden shrink-0 items-center gap-1.5 rounded-md border border-border bg-card px-3 py-1.5 text-xs font-medium text-foreground shadow-2xs transition group-hover:border-primary/50 group-hover:text-primary sm:inline-flex">
                      <UploadCloud className="h-3.5 w-3.5" />
                      Replace
                    </span>
                  </div>
                ) : (
                  <div
                    onDragOver={(e) => handleDrag(e, field.fileKey, true)}
                    onDragLeave={(e) => handleDrag(e, field.fileKey, false)}
                    onDrop={(e) => handleDrop(e, field)}
                    className={cn(
                      "relative border-2 border-dashed rounded-lg p-6 flex flex-col items-center justify-center text-center transition-all bg-card/50",
                      isDragOver
                        ? "border-primary bg-primary/5 dark:bg-primary/10"
                        : "border-border hover:border-primary/50 hover:bg-muted/10",
                      fieldError &&
                      "border-destructive hover:border-destructive/80",
                      disabled &&
                      "opacity-50 pointer-events-none cursor-not-allowed",
                    )}
                  >
                    <input
                      type="file"
                      multiple={field.isMultiple}
                      accept={acceptString}
                      disabled={disabled}
                      onChange={(e) => handleFileSelect(e, field)}
                      id={`file-input-${field.fileKey}`}
                      className="absolute inset-0 w-full h-full opacity-0 cursor-pointer disabled:cursor-not-allowed"
                    />

                    <div className="p-3 bg-muted rounded-full mb-3 text-muted-foreground transition group-hover:scale-110">
                      <UploadCloud
                        className={cn(
                          "h-6 w-6 text-muted-foreground",
                          isDragOver && "text-primary animate-bounce",
                        )}
                      />
                    </div>

                    <p className="text-sm font-semibold text-foreground">
                      Drag & drop your file here, or{" "}
                      <span className="text-primary font-bold hover:underline">
                        browse
                      </span>
                    </p>

                    <p className="text-xs text-muted-foreground mt-1">
                      Supported formats:{" "}
                      {field.allowedExtensions.join(", ").toUpperCase() ||
                        "All"}
                    </p>
                  </div>
                ))}

              {/* Validation Error Message */}
              {fieldError && (
                <div className="flex items-center gap-1.5 mt-1 text-xs text-destructive animate-in fade-in slide-in-from-top-1 duration-200">
                  <AlertCircle className="h-3.5 w-3.5" />
                  <span>{fieldError}</span>
                </div>
              )}
            </div>
          );
        })}
      </div>
    </div>
  );
}

export default SmartFileInput;