// ================================================================
// frontend/src/components/domain/procurement/UnifiedPurchaseOrderModal.tsx
// ================================================================
/**
 * Unified Purchase Order Modal
 * A comprehensive view/edit modal for Purchase Orders that combines the best
 * UI/UX approaches from both dashboard and procurement pages
 */

import React, { useState, useEffect, useMemo } from 'react';
import {
  Package,
  Building2,
  Calendar,
  Euro,
  FileText,
  CheckCircle,
  Edit,
  AlertCircle,
  X
} from 'lucide-react';
import { useTranslation } from 'react-i18next';
import { usePurchaseOrder, useUpdatePurchaseOrder } from '../../../api/hooks/purchase-orders';
import { useUserById } from '../../../api/hooks/user';
import { EditViewModal, EditViewModalSection } from '../../ui/EditViewModal/EditViewModal';
import { Button } from '../../ui/Button';
import type { PurchaseOrderItem } from '../../../api/services/purchase_orders';

interface UnifiedPurchaseOrderModalProps {
  poId: string;
  tenantId: string;
  isOpen: boolean;
  onClose: () => void;
  onApprove?: (poId: string) => void;
  onReject?: (poId: string, reason: string) => void;
  initialMode?: 'view' | 'edit';
  showApprovalActions?: boolean; // Whether to show approve/reject actions
}

export const UnifiedPurchaseOrderModal: React.FC<UnifiedPurchaseOrderModalProps> = ({
  poId,
  tenantId,
  isOpen,
  onClose,
  onApprove,
  onReject,
  initialMode = 'view',
  showApprovalActions = false
}) => {
  const { t, i18n } = useTranslation(['purchase_orders', 'common']);
  const { data: po, isLoading, refetch } = usePurchaseOrder(tenantId, poId);
  const [mode, setMode] = useState<'view' | 'edit'>(initialMode);
  const [showApprovalModal, setShowApprovalModal] = useState(false);
  const [approvalAction, setApprovalAction] = useState<'approve' | 'reject'>('approve');
  const [approvalNotes, setApprovalNotes] = useState('');
  const updatePurchaseOrderMutation = useUpdatePurchaseOrder();

  // Form state for edit mode
  const [formData, setFormData] = useState<Record<string, any>>({});

  // Initialize form data when entering edit mode
  useEffect(() => {
    if (mode === 'edit' && po) {
      setFormData({
        priority: po.priority,
        required_delivery_date: po.required_delivery_date || '',
        notes: po.notes || '',
        items: (po.items || []).map((item: PurchaseOrderItem) => ({
          id: item.id,
          inventory_product_id: item.inventory_product_id,
          product_code: item.product_code || '',
          product_name: item.product_name || '',
          ordered_quantity: item.ordered_quantity,
          unit_of_measure: item.unit_of_measure,
          unit_price: parseFloat(item.unit_price),
        })),
      });
    }
  }, [mode, po]);

  // Field change handler for edit mode
  const handleFieldChange = (sectionIndex: number, fieldIndex: number, value: any) => {
    // Map section/field indices to form field names
    // Section 0 = supplier_info (not editable)
    // Section 1 = order_details: [priority, required_delivery_date, notes]
    // Section 2 = products: [items]

    if (sectionIndex === 1) {
      // Order details section
      const fieldNames = ['priority', 'required_delivery_date', 'notes'];
      const fieldName = fieldNames[fieldIndex];
      if (fieldName) {
        setFormData(prev => ({ ...prev, [fieldName]: value }));
      }
    } else if (sectionIndex === 2 && fieldIndex === 0) {
      // Products section - items field
      setFormData(prev => ({ ...prev, items: value }));
    }
  };

  // Component to display user name with data fetching
  const UserName: React.FC<{ userId: string | undefined | null }> = ({ userId }) => {
    const { data: user, isLoading: userLoading } = useUserById(userId, {
      retry: 1,
      staleTime: 10 * 60 * 1000,
    });

    if (!userId) {
      return <>{t('common:not_available')}</>;
    }

    if (userId === '00000000-0000-0000-0000-000000000001' || userId === '00000000-0000-0000-0000-000000000000') {
      return <>{t('common:system')}</>;
    }

    if (userLoading) {
      return <>{t('common:loading')}</>;
    }

    if (!user) {
      return <>{t('common:unknown_user')}</>;
    }

    return <>{user.full_name || user.email || t('common:user')}</>;
  };

  // Component to display PO items
  const PurchaseOrderItemsTable: React.FC<{ items: PurchaseOrderItem[] }> = ({ items }) => {
    if (!items || items.length === 0) {
      return (
        <div className="text-center py-8 text-[var(--text-secondary)] border-2 border-dashed border-[var(--border-secondary)] rounded-lg">
          <Package className="h-12 w-12 mx-auto mb-2 opacity-50" />
          <p>{t('no_items')}</p>
        </div>
      );
    }

    const totalAmount = items.reduce((sum, item) => {
      const price = parseFloat(item.unit_price) || 0;
      const quantity = item.ordered_quantity || 0;
      return sum + (price * quantity);
    }, 0);

    return (
      <div className="space-y-3">
        {items.map((item: PurchaseOrderItem, index: number) => {
          const unitPrice = parseFloat(item.unit_price) || 0;
          const quantity = item.ordered_quantity || 0;
          const itemTotal = unitPrice * quantity;
          const productName = item.product_name || `${t('product')} ${index + 1}`;

          return (
            <div
              key={item.id || index}
              className="p-4 border border-[var(--border-secondary)] rounded-lg bg-[var(--bg-secondary)]/50 space-y-3"
            >
              <div className="flex justify-between items-start">
                <div className="flex-1">
                  <h4 className="font-semibold text-[var(--text-primary)]">{productName}</h4>
                  {item.product_code && (
                    <p className="text-sm text-[var(--text-secondary)]">
                      {t('sku')}: {item.product_code}
                    </p>
                  )}
                </div>
                <div className="text-right">
                  <p className="font-bold text-lg text-[var(--color-primary-600)]">
                    €{itemTotal.toFixed(2)}
                  </p>
                </div>
              </div>
              <div className="grid grid-cols-2 gap-4 text-sm">
                <div>
                  <p className="text-[var(--text-secondary)]">{t('quantity')}</p>
                  <p className="font-medium text-[var(--text-primary)]">
                    {quantity} {item.unit_of_measure}
                  </p>
                </div>
                <div>
                  <p className="text-[var(--text-secondary)]">{t('unit_price')}</p>
                  <p className="font-medium text-[var(--text-primary)]">€{unitPrice.toFixed(2)}</p>
                </div>
              </div>
              {item.quality_requirements && (
                <div className="pt-2 border-t border-[var(--border-secondary)]">
                  <p className="text-xs text-[var(--text-secondary)]">{t('quality_requirements')}</p>
                  <p className="text-sm text-[var(--text-primary)]">{item.quality_requirements}</p>
                </div>
              )}
              {item.item_notes && (
                <div className="pt-2 border-t border-[var(--border-secondary)]">
                  <p className="text-xs text-[var(--text-secondary)]">{t('common:notes')}</p>
                  <p className="text-sm text-[var(--text-primary)]">{item.item_notes}</p>
                </div>
              )}
            </div>
          );
        })}
        <div className="flex justify-between items-center pt-4 border-t-2 border-[var(--border-primary)]">
          <span className="font-semibold text-lg text-[var(--text-primary)]">{t('total')}</span>
          <span className="font-bold text-2xl text-[var(--color-primary-600)]">€{totalAmount.toFixed(2)}</span>
        </div>
      </div>
    );
  };

  // Priority and unit options for edit mode
  const priorityOptions = [
    { value: 'urgent', label: t('priority_urgent') },
    { value: 'high', label: t('priority_high') },
    { value: 'normal', label: t('priority_normal') },
    { value: 'low', label: t('priority_low') }
  ];

  const unitOptions = [
    { value: 'kg', label: t('unit_kg') },
    { value: 'g', label: t('unit_g') },
    { value: 'l', label: t('unit_l') },
    { value: 'ml', label: t('unit_ml') },
    { value: 'units', label: t('unit_units') },
    { value: 'boxes', label: t('unit_boxes') },
    { value: 'bags', label: t('unit_bags') }
  ];

  // Build sections for EditViewModal
  const buildViewSections = (): EditViewModalSection[] => {
    if (!po) return [];

    const formatCurrency = (value: any) => {
      const num = Number(value);
      return isNaN(num) ? '0.00' : num.toFixed(2);
    };

    const sections: EditViewModalSection[] = [
      {
        title: t('general_information'),
        icon: FileText,
        fields: [
          {
            label: t('po_number'),
            value: po.po_number,
            type: 'text' as const
          },
          {
            label: t('status_label'),
            value: t(`status.${po.status}`),
            type: 'status' as const
          },
          {
            label: t('priority'),
            value: t(`priority_${po.priority}` as any) || po.priority,
            type: 'text' as const
          },
          {
            label: t('created'),
            value: new Date(po.created_at).toLocaleDateString(i18n.language, {
              year: 'numeric',
              month: 'long',
              day: 'numeric',
              hour: '2-digit',
              minute: '2-digit'
            }),
            type: 'text' as const
          }
        ]
      },
      {
        title: t('supplier_info'),
        icon: Building2,
        fields: [
          {
            label: t('supplier_name'),
            value: po.supplier?.name || t('common:unknown'),
            type: 'text' as const
          },
          ...(po.supplier?.supplier_code ? [{
            label: t('supplier_code'),
            value: po.supplier.supplier_code,
            type: 'text' as const
          }] : []),
          ...(po.supplier?.email ? [{
            label: t('email'),
            value: po.supplier.email,
            type: 'text' as const
          }] : []),
          ...(po.supplier?.phone ? [{
            label: t('phone'),
            value: po.supplier.phone,
            type: 'text' as const
          }] : [])
        ]
      },
      {
        title: t('financial_summary'),
        icon: Euro,
        fields: [
          ...(po.subtotal !== undefined ? [{
            label: t('subtotal'),
            value: `€${formatCurrency(po.subtotal)}`,
            type: 'text' as const
          }] : []),
          ...(po.tax_amount !== undefined ? [{
            label: t('tax'),
            value: `€${formatCurrency(po.tax_amount)}`,
            type: 'text' as const
          }] : []),
          ...(po.discount_amount !== undefined ? [{
            label: t('discount'),
            value: `€${formatCurrency(po.discount_amount)}`,
            type: 'text' as const
          }] : []),
          {
            label: t('total_amount'),
            value: `€${formatCurrency(po.total_amount)}`,
            type: 'text' as const,
            highlight: true
          }
        ]
      },
      {
        title: t('items'),
        icon: Package,
        fields: [
          {
            label: '',
            value: <PurchaseOrderItemsTable items={po.items || []} />,
            type: 'component' as const,
            span: 2
          }
        ]
      },
      {
        title: t('delivery'),
        icon: Calendar,
        fields: [
          ...(po.required_delivery_date ? [{
            label: t('required_delivery_date'),
            value: new Date(po.required_delivery_date).toLocaleDateString(i18n.language, {
              year: 'numeric',
              month: 'short',
              day: 'numeric'
            }),
            type: 'text' as const
          }] : []),
          ...(po.estimated_delivery_date ? [{
            label: t('expected_delivery'),
            value: new Date(po.estimated_delivery_date).toLocaleDateString(i18n.language, {
              year: 'numeric',
              month: 'short',
              day: 'numeric'
            }),
            type: 'text' as const
          }] : []),
          ...(po.actual_delivery_date ? [{
            label: t('actual_delivery'),
            value: new Date(po.actual_delivery_date).toLocaleDateString(i18n.language, {
              year: 'numeric',
              month: 'short',
              day: 'numeric'
            }),
            type: 'text' as const
          }] : [])
        ]
      }
    ];

    // Add approval section if approval data exists
    if (po.approved_by || po.approved_at || po.approval_notes) {
      sections.push({
        title: t('approval'),
        icon: CheckCircle,
        fields: [
          ...(po.approved_by ? [{
            label: t('approved_by'),
            value: <UserName userId={po.approved_by} />,
            type: 'component' as const
          }] : []),
          ...(po.approved_at ? [{
            label: t('approved_at'),
            value: new Date(po.approved_at).toLocaleDateString(i18n.language, {
              year: 'numeric',
              month: 'short',
              day: 'numeric',
              hour: '2-digit',
              minute: '2-digit'
            }),
            type: 'text' as const
          }] : []),
          ...(po.approval_notes ? [{
            label: t('approval_notes'),
            value: po.approval_notes,
            type: 'text' as const
          }] : [])
        ]
      });
    }

    // Add notes section if present
    if (po.notes || po.internal_notes) {
      const notesFields = [];
      if (po.notes) {
        notesFields.push({
          label: t('order_notes'),
          value: po.notes,
          type: 'text' as const
        });
      }
      if (po.internal_notes) {
        notesFields.push({
          label: t('internal_notes'),
          value: po.internal_notes,
          type: 'text' as const
        });
      }

      sections.push({
        title: t('notes'),
        icon: FileText,
        fields: notesFields
      });
    }

    // Add audit trail section if audit data exists
    if (po.created_by || po.updated_at) {
      const auditFields = [];
      if (po.created_by) {
        auditFields.push({
          label: t('created_by'),
          value: <UserName userId={po.created_by} />,
          type: 'component' as const
        });
      }
      if (po.updated_at) {
        auditFields.push({
          label: t('last_updated'),
          value: new Date(po.updated_at).toLocaleDateString(i18n.language, {
            year: 'numeric',
            month: 'short',
            day: 'numeric',
            hour: '2-digit',
            minute: '2-digit'
          }),
          type: 'text' as const
        });
      }

      sections.push({
        title: t('audit_trail'),
        icon: FileText,
        fields: auditFields
      });
    }

    return sections;
  };

  // Component to edit PO items
  const EditablePurchaseOrderItems: React.FC<{ value: any; onChange?: (value: any) => void }> = ({ value: items, onChange }) => {
    const handleItemChange = (index: number, field: string, value: any) => {
      if (!items || !onChange) return;
      const updatedItems = [...items];
      updatedItems[index] = {
        ...updatedItems[index],
        [field]: value
      };
      onChange(updatedItems);
    };

    if (!items || items.length === 0) {
      return (
        <div className="text-center py-8 text-[var(--text-secondary)] border-2 border-dashed border-[var(--border-secondary)] rounded-lg">
          <Package className="h-12 w-12 mx-auto mb-2 opacity-50" />
          <p>{t('no_items')}</p>
        </div>
      );
    }

    const totalAmount = items.reduce((sum, item) => {
      const price = parseFloat(item.unit_price) || 0;
      const quantity = item.ordered_quantity || 0;
      return sum + (price * quantity);
    }, 0);

    return (
      <div className="space-y-3">
        {items.map((item: any, index: number) => {
          const unitPrice = parseFloat(item.unit_price) || 0;
          const quantity = item.ordered_quantity || 0;
          const itemTotal = unitPrice * quantity;
          const productName = item.product_name || `${t('product')} ${index + 1}`;

          return (
            <div
              key={item.id || index}
              className="p-4 border border-[var(--border-secondary)] rounded-lg bg-[var(--bg-secondary)]/50 space-y-3"
            >
              <div className="flex justify-between items-start">
                <div className="flex-1">
                  <h4 className="font-semibold text-[var(--text-primary)]">{productName}</h4>
                  {item.product_code && (
                    <p className="text-sm text-[var(--text-secondary)]">
                      {t('sku')}: {item.product_code}
                    </p>
                  )}
                </div>
                <div className="text-right">
                  <p className="font-bold text-lg text-[var(--color-primary-600)]">
                    €{itemTotal.toFixed(2)}
                  </p>
                </div>
              </div>

              {/* Editable fields */}
              <div className="grid grid-cols-2 gap-4">
                <div>
                  <label className="block text-xs text-[var(--text-secondary)] mb-1">
                    {t('quantity')}
                  </label>
                  <div className="flex gap-2">
                    <input
                      type="number"
                      value={quantity}
                      onChange={(e) => handleItemChange(index, 'ordered_quantity', parseFloat(e.target.value) || 0)}
                      min="0"
                      step="0.01"
                      className="flex-1 px-3 py-2 border border-[var(--border-secondary)] rounded-md focus:outline-none focus:ring-2 focus:ring-[var(--color-primary)] bg-[var(--bg-primary)]"
                    />
                    <select
                      value={item.unit_of_measure}
                      onChange={(e) => handleItemChange(index, 'unit_of_measure', e.target.value)}
                      className="px-3 py-2 border border-[var(--border-secondary)] rounded-md focus:outline-none focus:ring-2 focus:ring-[var(--color-primary)] bg-[var(--bg-primary)]"
                    >
                      {unitOptions.map(opt => (
                        <option key={opt.value} value={opt.value}>{opt.label}</option>
                      ))}
                    </select>
                  </div>
                </div>
                <div>
                  <label className="block text-xs text-[var(--text-secondary)] mb-1">
                    {t('unit_price')}
                  </label>
                  <input
                    type="number"
                    value={unitPrice}
                    onChange={(e) => handleItemChange(index, 'unit_price', e.target.value)}
                    min="0"
                    step="0.01"
                    className="w-full px-3 py-2 border border-[var(--border-secondary)] rounded-md focus:outline-none focus:ring-2 focus:ring-[var(--color-primary)] bg-[var(--bg-primary)]"
                  />
                </div>
              </div>
            </div>
          );
        })}
        <div className="flex justify-between items-center pt-4 border-t-2 border-[var(--border-primary)]">
          <span className="font-semibold text-lg text-[var(--text-primary)]">{t('total')}</span>
          <span className="font-bold text-2xl text-[var(--color-primary-600)]">€{totalAmount.toFixed(2)}</span>
        </div>
      </div>
    );
  };

  // Build sections for edit mode
  const buildEditSections = (): EditViewModalSection[] => {
    if (!po) return [];

    return [
      {
        title: t('supplier_info'),
        icon: Building2,
        fields: [
          {
            label: t('supplier'),
            value: po.supplier?.name || t('common:unknown'),
            type: 'text' as const,
            editable: false,
            helpText: t('supplier_cannot_modify')
          }
        ]
      },
      {
        title: t('order_details'),
        icon: Calendar,
        fields: [
          {
            label: t('priority'),
            value: formData.priority || po.priority,
            type: 'select' as const,
            editable: true,
            options: priorityOptions,
            helpText: t('adjust_priority')
          },
          {
            label: t('required_delivery_date'),
            value: formData.required_delivery_date || po.required_delivery_date || '',
            type: 'date' as const,
            editable: true,
            helpText: t('delivery_deadline')
          },
          {
            label: t('notes'),
            value: formData.notes !== undefined ? formData.notes : (po.notes || ''),
            type: 'textarea' as const,
            editable: true,
            placeholder: t('special_instructions'),
            span: 2,
            helpText: t('additional_info')
          }
        ]
      },
      {
        title: t('products'),
        icon: Package,
        fields: [
          {
            label: t('products'),
            value: formData.items || (po.items || []).map((item: PurchaseOrderItem) => ({
              id: item.id,
              inventory_product_id: item.inventory_product_id,
              product_code: item.product_code || '',
              product_name: item.product_name || '',
              ordered_quantity: item.ordered_quantity,
              unit_of_measure: item.unit_of_measure,
              unit_price: parseFloat(item.unit_price),
            })),
            type: 'component' as const,
            component: EditablePurchaseOrderItems,
            span: 2,
            helpText: t('modify_quantities')
          }
        ]
      }
    ];
  };

  // Save handler for edit mode
  const handleSave = async () => {
    try {
      const items = formData.items || [];

      if (items.length === 0) {
        throw new Error(t('at_least_one_product'));
      }

      // Validate quantities
      const invalidQuantities = items.some((item: any) => item.ordered_quantity <= 0);
      if (invalidQuantities) {
        throw new Error(t('quantities_greater_zero'));
      }

      // Validate required fields
      const invalidProducts = items.some((item: any) => !item.product_name);
      if (invalidProducts) {
        throw new Error(t('products_need_names'));
      }

      // Prepare the update data
      const updateData: any = {
        notes: formData.notes || undefined,
        priority: formData.priority || undefined,
      };

      // Add delivery date if changed
      if (formData.required_delivery_date) {
        updateData.required_delivery_date = formData.required_delivery_date;
      }

      // Update purchase order
      await updatePurchaseOrderMutation.mutateAsync({
        tenantId,
        poId,
        data: updateData
      });

      // Refetch data and switch back to view mode
      await refetch();
      setMode('view');
    } catch (error) {
      console.error('Error modifying purchase order:', error);
      throw error;
    }
  };

  // Build actions for modal footer - only Approve button for pending approval POs
  const buildActions = () => {
    if (!po) return undefined;

    const actions = [];

    // Show Approve/Reject actions only if explicitly enabled and status is pending approval
    if (showApprovalActions && po.status === 'pending_approval') {
      actions.push(
        {
          label: t('actions.approve'),
          icon: CheckCircle,
          onClick: () => {
            setApprovalAction('approve');
            setApprovalNotes('');
            setShowApprovalModal(true);
          },
          variant: 'primary' as const
        },
        {
          label: t('actions.reject'),
          icon: X,
          onClick: () => {
            setApprovalAction('reject');
            setApprovalNotes('');
            setShowApprovalModal(true);
          },
          variant: 'outline' as const,
          destructive: true
        }
      );
    }

    return actions.length > 0 ? actions : undefined;
  };

  const sections = useMemo(() => {
    return mode === 'view' ? buildViewSections() : buildEditSections();
  }, [mode, po, formData, i18n.language]);

  // Handle approval/rejection
  const handleApprovalAction = async () => {
    if (!poId) return;

    try {
      if (approvalAction === 'approve') {
        onApprove?.(poId);
      } else {
        if (!approvalNotes.trim()) {
          throw new Error(t('reason_required'));
        }
        onReject?.(poId, approvalNotes);
      }
      setShowApprovalModal(false);
      onClose(); // Close the main modal after approval action
    } catch (error) {
      console.error('Error in approval action:', error);
    }
  };

  return (
    <>
      <EditViewModal
        isOpen={isOpen}
        onClose={() => {
          setMode('view');
          onClose();
        }}
        mode={mode}
        onModeChange={setMode}
        title={po?.po_number || t('purchase_order')}
        subtitle={po ? new Date(po.created_at).toLocaleDateString(i18n.language, {
          year: 'numeric',
          month: 'long',
          day: 'numeric'
        }) : undefined}
        sections={sections}
        actions={buildActions()}
        loading={isLoading}
        size="lg"
        // Enable edit mode via standard Edit button (only for pending approval)
        onEdit={po?.status === 'pending_approval' ? () => setMode('edit') : undefined}
        // Disable edit mode for POs that are approved, cancelled, or completed
        disableEdit={po?.status === 'approved' || po?.status === 'cancelled' || po?.status === 'completed'}
        onSave={mode === 'edit' ? handleSave : undefined}
        onCancel={mode === 'edit' ? () => setMode('view') : undefined}
        onFieldChange={handleFieldChange}
        saveLabel={t('actions.save')}
        cancelLabel={t('actions.cancel')}
      />

      {/* Approval Modal */}
      {showApprovalModal && (
        <div className="fixed inset-0 bg-black bg-opacity-50 flex items-center justify-center z-50">
          <div className="bg-white rounded-lg shadow-xl max-w-md w-full mx-4">
            <div className="p-6">
              <h3 className="text-lg font-semibold mb-4">
                {approvalAction === 'approve' ? t('actions.approve') : t('actions.reject')} {t('purchase_order')}
              </h3>
              <div className="mb-4">
                <label className="block text-sm font-medium text-gray-700 mb-2">
                  {approvalAction === 'approve' 
                    ? t('approval_notes_optional') 
                    : t('rejection_reason_required')}
                </label>
                <textarea
                  className="w-full px-3 py-2 border border-gray-300 rounded-md focus:outline-none focus:ring-2 focus:ring-primary-500"
                  rows={4}
                  value={approvalNotes}
                  onChange={(e) => setApprovalNotes(e.target.value)}
                  placeholder={approvalAction === 'approve'
                    ? t('approval_notes_placeholder')
                    : t('rejection_reason_placeholder')}
                />
              </div>
              <div className="flex justify-end gap-2">
                <Button
                  variant="outline"
                  onClick={() => {
                    setShowApprovalModal(false);
                    setApprovalNotes('');
                  }}
                >
                  {t('actions.cancel')}
                </Button>
                <Button
                  onClick={handleApprovalAction}
                  disabled={updatePurchaseOrderMutation.isPending}
                >
                  {approvalAction === 'approve' ? t('actions.approve') : t('actions.reject')}
                </Button>
              </div>
            </div>
          </div>
        </div>
      )}
    </>
  );
};