import React, { useEffect, useMemo, useState } from "react";
import { useNavigate } from "react-router-dom";
import { Button, Modal, Spinner } from "react-bootstrap";
import { AuthService, EmployeeService, EventsService } from "../../services";
import { EMPLOYEE_PERMISSION_GROUPS } from "../../shared";

const SYSTEM_ACCESS_PERMISSION = "System Access";

const ExternalEmployeesImport = () => {
  const navigate = useNavigate();
  const [loading, setLoading] = useState(false);
  const [saving, setSaving] = useState(false);
  const [employees, setEmployees] = useState([]);
  const [siteFilter, setSiteFilter] = useState(EventsService.site || 3);
  const [keyword, setKeyword] = useState("");
  const [showPermissionModal, setShowPermissionModal] = useState(false);
  const [selectedEmployee, setSelectedEmployee] = useState(undefined);
  const [selectedPermissions, setSelectedPermissions] = useState([SYSTEM_ACCESS_PERMISSION]);
  const [selectedAllowSite, setSelectedAllowSite] = useState(EventsService.site || 3);

  useEffect(() => {
    if (!AuthService.canAddOrEditEmployees()) {
      window.alert("You haven't login yet OR this user does not have access to this page. Please change an admin account to login.");
      AuthService.logout();
      navigate("/login");
      return;
    }
    loadExternalEmployees();
  }, []);

  const loadExternalEmployees = () => {
    setLoading(true);
    EmployeeService.getExternalEmployeesList()
      .then((response) => {
        setEmployees(Array.isArray(response?.data) ? response.data : []);
      })
      .catch((error) => {
        window.alert(error?.response?.data?.message || "Failed to load employees from HR system.");
      })
      .finally(() => {
        setLoading(false);
      });
  };

  const filteredEmployees = useMemo(() => {
    return (employees || [])
      .filter((item) => siteFilter === 'all' || Number(item?.site) === Number(siteFilter))
      .filter((item) => {
        if (!keyword) return true;
        const key = keyword.toLowerCase();
        return (
          (item?.username || "").toLowerCase().includes(key) ||
          (item?.name || "").toLowerCase().includes(key) ||
          (item?.title || "").toLowerCase().includes(key)
        );
      });
  }, [employees, siteFilter, keyword]);

  const openPermissionModal = (employee) => {
    const allowSite = siteFilter === 'all'
      ? (Number(employee?.site) || EventsService.site || 3)
      : Number(siteFilter);
    setSelectedEmployee(employee);
    setSelectedAllowSite(allowSite);
    setSelectedPermissions([SYSTEM_ACCESS_PERMISSION]);
    setShowPermissionModal(true);
    EmployeeService.getExternalUserPermission(employee?.employee_id, allowSite)
      .then((response) => {
        const existingPermissions = Array.isArray(response?.data?.permissions) ? response.data.permissions : [];
        const nextPermissions = Array.from(new Set([SYSTEM_ACCESS_PERMISSION, ...existingPermissions]));
        setSelectedPermissions(nextPermissions);
      })
      .catch(() => {
        setSelectedPermissions([SYSTEM_ACCESS_PERMISSION]);
      });
  };

  const closePermissionModal = () => {
    if (saving) return;
    setShowPermissionModal(false);
    setSelectedEmployee(undefined);
    setSelectedPermissions([SYSTEM_ACCESS_PERMISSION]);
    setSelectedAllowSite(EventsService.site || 3);
  };

  const togglePermission = (permissionKey) => {
    if (permissionKey === SYSTEM_ACCESS_PERMISSION) return;
    setSelectedPermissions((prev) => {
      if (prev.includes(permissionKey)) {
        return prev.filter((item) => item !== permissionKey);
      }
      return [...prev, permissionKey];
    });
  };

  const savePermissions = () => {
    if (!selectedEmployee?.employee_id) return;
    setSaving(true);
    EmployeeService.saveExternalUserPermission({
      external_user_id: selectedEmployee.employee_id,
      username: selectedEmployee.username || "",
      name: selectedEmployee.name || "",
      email: selectedEmployee.email || "",
      allow_site: Number(selectedAllowSite),
      permissions: selectedPermissions
    })
      .then(() => {
        closePermissionModal();
      })
      .catch((error) => {
        window.alert(error?.response?.data?.message || "Failed to save external user permissions.");
      })
      .finally(() => {
        setSaving(false);
      });
  };

  return (
    <>
      <div className="list row mb-4">
        <div className="col-md-12 text-primary">
          <h5>
            Add New Employee From HR System
            <button className="btn btn-link btn-sm" onClick={() => navigate("/employees/list")}>Back</button>
          </h5>
        </div>
      </div>

      <div className="list row mb-4">
        <div className="col-md-12">
          <div className="mb-3 d-flex align-items-center" style={{ gap: "12px", flexWrap: "wrap" }}>
            <label>
              Filter By Site:
              <select
                className="ms-2"
                value={siteFilter}
                onChange={(e) => setSiteFilter(e.currentTarget.value)}
              >
                <option value="all">All Sites</option>
                <option value={1}>Site 1</option>
                <option value={2}>Site 2</option>
                <option value={3}>Site 3</option>
                <option value={4}>Site 4</option>
                <option value={5}>Site 5</option>
              </select>
            </label>
            <label>
              Filter By Username/Name:
              <input
                className="ms-2"
                type="text"
                value={keyword}
                onChange={(e) => setKeyword(e.currentTarget.value)}
              />
            </label>
            <button className="btn btn-primary btn-sm" onClick={loadExternalEmployees} disabled={loading}>
              {loading ? "Loading..." : "Refresh"}
            </button>
          </div>

          {loading ? (
            <div className="py-4"><Spinner size="sm" className="me-2" />Loading employees...</div>
          ) : (
            <table className="personnel-info-table">
              <thead>
                <tr>
                  <th>Username</th>
                  <th>Name</th>
                  <th>Title</th>
                  <th>Site</th>
                  <th></th>
                </tr>
              </thead>
              <tbody>
                {filteredEmployees.map((item) => (
                  <tr key={`${item?.employee_id}-${item?.site}`}>
                    <td>{item?.username}</td>
                    <td>{item?.name}</td>
                    <td>{item?.title}</td>
                    <td>{item?.site}</td>
                    <td>
                      <button
                        className="btn btn-primary btn-sm"
                        onClick={() => openPermissionModal(item)}
                      >
                        Add
                      </button>
                    </td>
                  </tr>
                ))}
                {filteredEmployees.length === 0 && (
                  <tr>
                    <td colSpan={5} style={{ textAlign: "center" }}>No active employees found for selected site.</td>
                  </tr>
                )}
              </tbody>
            </table>
          )}
        </div>
      </div>

      <Modal show={showPermissionModal} onHide={closePermissionModal} size="lg">
        <Modal.Header closeButton>
          <Modal.Title>Set Permissions - {selectedEmployee?.username}</Modal.Title>
        </Modal.Header>
        <Modal.Body>
          <div className="mb-3">
            <strong>Allow Site:</strong> {selectedAllowSite}
          </div>
          {Object.entries(EMPLOYEE_PERMISSION_GROUPS).map(([groupName, permissionItems]) => (
            <div key={groupName} className="mb-3">
              <div className="text-primary mb-1">{groupName}</div>
              <div style={{ display: "flex", flexWrap: "wrap", gap: "10px 18px" }}>
                {permissionItems.map((permissionKey) => (
                  <label key={permissionKey} style={{ minWidth: "280px" }}>
                    <input
                      type="checkbox"
                      className="me-2"
                      checked={selectedPermissions.includes(permissionKey)}
                      onChange={() => togglePermission(permissionKey)}
                      disabled={permissionKey === SYSTEM_ACCESS_PERMISSION}
                    />
                    {permissionKey}
                    {permissionKey === SYSTEM_ACCESS_PERMISSION ? " (required)" : ""}
                  </label>
                ))}
              </div>
            </div>
          ))}
        </Modal.Body>
        <Modal.Footer>
          <Button variant="secondary" onClick={closePermissionModal} disabled={saving}>
            Cancel
          </Button>
          <Button variant="primary" onClick={savePermissions} disabled={saving}>
            {saving ? <><Spinner size="sm" className="me-2" />Saving...</> : "Done"}
          </Button>
        </Modal.Footer>
      </Modal>
    </>
  );
};

export default ExternalEmployeesImport;