import { useCallback, useEffect, useState } from "react";
import type { FormEvent } from "react";
import {
  assignEmployeeToCompany,
  createCompany,
  deleteCompany,
  getCompanyEmployeeNames,
} from "@api/companiesApi";
import { getUsers } from "@api/usersApi";
import { Modal } from "@components/Modal";
import { PageHeader } from "@components/PageHeader";
import type { BackendPreference } from "@/types/backend";
import type { Company } from "@/types/companies";
import type { Employee } from "@/types/users";
import { useCompaniesStore } from "../store/companiesStore";
import styles from "./CompaniesPage.module.scss";

type CompaniesPageProps = {
  backendPreference: BackendPreference;
};

type EmployeeNamesByCompany = Record<number, string[]>;

export function CompaniesPage({ backendPreference }: CompaniesPageProps) {
  const [employeeNamesByCompany, setEmployeeNamesByCompany] = useState<EmployeeNamesByCompany>({});
  const [users, setUsers] = useState<Employee[]>([]);
  const [companyName, setCompanyName] = useState("");
  const [companyToDelete, setCompanyToDelete] = useState<Company | null>(null);
  const [selectedCompany, setSelectedCompany] = useState<Company | null>(null);
  const [selectedEmployeeId, setSelectedEmployeeId] = useState("");
  const [error, setError] = useState("");
  const [isAddCompanyOpen, setIsAddCompanyOpen] = useState(false);
  const [deletingCompanyId, setDeletingCompanyId] = useState<number | null>(null);
  const [isLoading, setIsLoading] = useState(true);
  const [isSaving, setIsSaving] = useState(false);
  const companies = useCompaniesStore((state) => state.companies);
  const refreshCompanies = useCompaniesStore((state) => state.loadCompanies);

  const loadCompanies = useCallback(async () => {
    setError("");
    setIsLoading(true);

    try {
      const [companiesResponse, usersResponse] = await Promise.all([
        refreshCompanies(backendPreference),
        getUsers(backendPreference),
      ]);
      const employeeNameEntries = await Promise.all(
        companiesResponse.map(async (company) => {
          const response = await getCompanyEmployeeNames(backendPreference, company.name);
          return [company.id, response.employees] as const;
        }),
      );

      setUsers(usersResponse);
      setEmployeeNamesByCompany(Object.fromEntries(employeeNameEntries));
    } catch (loadError) {
      setError(loadError instanceof Error ? loadError.message : "Unable to load companies");
    } finally {
      setIsLoading(false);
    }
  }, [backendPreference, refreshCompanies]);

  useEffect(() => {
    void loadCompanies();
  }, [loadCompanies]);

  async function handleCreateCompany(event: FormEvent<HTMLFormElement>) {
    event.preventDefault();
    setIsSaving(true);
    setError("");

    try {
      await createCompany(backendPreference, { name: companyName });
      setCompanyName("");
      setIsAddCompanyOpen(false);
      await loadCompanies();
    } catch (saveError) {
      setError(saveError instanceof Error ? saveError.message : "Unable to create company");
    } finally {
      setIsSaving(false);
    }
  }

  async function handleAssignEmployee(event: FormEvent<HTMLFormElement>) {
    event.preventDefault();

    if (!selectedCompany || !selectedEmployeeId) {
      return;
    }

    setIsSaving(true);
    setError("");

    try {
      await assignEmployeeToCompany(
        backendPreference,
        selectedCompany.id,
        Number(selectedEmployeeId),
      );
      setSelectedCompany(null);
      setSelectedEmployeeId("");
      await loadCompanies();
    } catch (saveError) {
      setError(saveError instanceof Error ? saveError.message : "Unable to assign employee");
    } finally {
      setIsSaving(false);
    }
  }

  async function handleDeleteCompany() {
    if (!companyToDelete) {
      return;
    }

    setDeletingCompanyId(companyToDelete.id);
    setError("");

    try {
      await deleteCompany(backendPreference, companyToDelete.id);
      setCompanyToDelete(null);
      await loadCompanies();
    } catch (deleteError) {
      setError(deleteError instanceof Error ? deleteError.message : "Unable to delete company");
    } finally {
      setDeletingCompanyId(null);
    }
  }

  return (
    <>
      <PageHeader
        title="Companies"
        description="Create companies, view company names, and see the users assigned to each company."
        actions={
          <button className={styles.primaryButton} onClick={() => setIsAddCompanyOpen(true)}>
            Add company
          </button>
        }
      />
      {error ? <p className={styles.error}>{error}</p> : null}
      {isLoading ? <p className={styles.muted}>Loading companies...</p> : null}
      <section className={styles.companyGrid} aria-label="Company list">
        {companies.map((company) => (
          <article className={styles.companyCard} key={company.id}>
            <div className={styles.companyHeader}>
              <div>
                <h3>{company.name}</h3>
                <p>Created {new Date(company.date_created).toLocaleDateString()}</p>
              </div>
              <button
                className={styles.deleteButton}
                disabled={deletingCompanyId === company.id}
                onClick={() => setCompanyToDelete(company)}
                type="button"
                aria-label={`Delete ${company.name}`}
              >
                <svg aria-hidden="true" viewBox="0 0 24 24" focusable="false">
                  <path d="M9 3h6l1 2h4v2H4V5h4l1-2Zm1 6h2v9h-2V9Zm4 0h2v9h-2V9ZM7 9h2v10h6V9h2v12H7V9Z" />
                </svg>
              </button>
            </div>
            <div className={styles.employeeList} aria-label={`${company.name} users`}>
              {(employeeNamesByCompany[company.id] ?? []).length > 0 ? (
                employeeNamesByCompany[company.id].map((user) => (
                  <span className={styles.pill} key={user}>
                    {user}
                  </span>
                ))
              ) : (
                <span className={styles.muted}>No users assigned</span>
              )}
            </div>
            <button className={styles.secondaryButton} onClick={() => setSelectedCompany(company)}>
              Add users
            </button>
          </article>
        ))}
      </section>

      {isAddCompanyOpen ? (
        <Modal title="Add company" onClose={() => setIsAddCompanyOpen(false)}>
          <form className={styles.form} onSubmit={handleCreateCompany}>
            <label>
              Company name
              <input
                value={companyName}
                onChange={(event) => setCompanyName(event.target.value)}
                required
              />
            </label>
            <button className={styles.primaryButton} disabled={isSaving} type="submit">
              {isSaving ? "Saving..." : "Create company"}
            </button>
          </form>
        </Modal>
      ) : null}

      {selectedCompany
        ? (() => {
            const assignedNames = new Set(employeeNamesByCompany[selectedCompany.id] ?? []);
            const availableUsers = users.filter(
              (user) => !assignedNames.has(`${user.name} ${user.last_name}`),
            );

            return (
              <Modal
                title={`Add users to ${selectedCompany.name}`}
                onClose={() => setSelectedCompany(null)}
              >
                <form className={styles.form} onSubmit={handleAssignEmployee}>
                  {availableUsers.length === 0 ? (
                    <p className={styles.muted}>All users are in a company</p>
                  ) : (
                    <label>
                      Existing user
                      <select
                        value={selectedEmployeeId}
                        onChange={(event) => setSelectedEmployeeId(event.target.value)}
                        required
                      >
                        <option value="">Select a user</option>
                        {availableUsers.map((user) => (
                          <option key={user.id} value={user.id}>
                            {user.name} {user.last_name}
                          </option>
                        ))}
                      </select>
                    </label>
                  )}
                  <button
                    className={styles.primaryButton}
                    disabled={isSaving || availableUsers.length === 0}
                    type="submit"
                  >
                    {isSaving ? "Saving..." : "Assign user"}
                  </button>
                </form>
              </Modal>
            );
          })()
        : null}

      {companyToDelete ? (
        <Modal title="Delete company" onClose={() => setCompanyToDelete(null)}>
          <div className={styles.confirmation}>
            <p>
              Delete <strong>{companyToDelete.name}</strong>? This action cannot be undone.
            </p>
            <div className={styles.confirmationActions}>
              <button
                className={styles.secondaryButton}
                onClick={() => setCompanyToDelete(null)}
                type="button"
              >
                Cancel
              </button>
              <button
                className={styles.dangerButton}
                disabled={deletingCompanyId === companyToDelete.id}
                onClick={() => void handleDeleteCompany()}
                type="button"
              >
                {deletingCompanyId === companyToDelete.id ? "Deleting..." : "Delete company"}
              </button>
            </div>
          </div>
        </Modal>
      ) : null}
    </>
  );
}