<?php

declare(strict_types=1);

namespace App\Security;

/**
 * The roles this application knows about, and the policy that assigns them.
 *
 * Roles are stored as plain strings in the User::$roles JSON column and consumed as strings
 * by #[IsGranted], the voters and security.yaml's role_hierarchy, so they are constants
 * rather than an enum.
 *
 * The governing rule: the BusPro CRM is the source of truth. It may nominate, but never grant,
 * an administrative role — a nomination is stored as a marker (ROLE_X_PENDING) that grants
 * nothing until an administrator approves it in /admin/user. The CRM's word alone is enough to
 * take a role away, never to hand it out, and an administrator's word alone is enough for
 * neither.
 *
 * One role is not claimed by the CRM at all: ROLE_EMPLOYEE is derived from the account's own
 * email domain, because BusPro has no selection expressing "works here". It is passed to sync()
 * as a claim alongside the CRM's, so it is granted and revoked by exactly the same machinery.
 * That widens a claim from "what the CRM reports" to "what the CRM reports plus what the account
 * itself implies", and nothing more: ROLE_EMPLOYEE is not administrative, so it cannot reach the
 * nomination path, and the CRM remains the only source for every role that grants privileges.
 */
final class Role
{
    /**
     * The role every account holds implicitly. User::getRoles() prepends it and it is never
     * stored, so it has to be filtered out wherever a role set is written back.
     */
    public const USER = 'ROLE_USER';

    public const ADMIN = 'ROLE_ADMIN';
    public const MANAGER = 'ROLE_MANAGER';
    public const TEAMER = 'ROLE_TEAMER';
    public const CUSTOMER = 'ROLE_CUSTOMER';
    public const HOUSE_MANAGER = 'ROLE_HOUSE_MANAGER';
    public const GROUPS_ADMIN = 'ROLE_GROUPS_ADMIN';
    public const GROUPS_MANAGER = 'ROLE_GROUPS_MANAGER';
    public const EMPLOYEE = 'ROLE_EMPLOYEE';

    /**
     * Appended to an administrative role to mark it as claimed by the CRM but not yet approved.
     * Markers live in the same column as the real roles and are handed to Symfony along with
     * them, but nothing references them: no access_control rule, no role_hierarchy entry and no
     * voter. Always ask effectiveOnly() when the question is what an account may actually do.
     */
    public const PENDING_SUFFIX = '_PENDING';

    /**
     * The roles that are actually assigned to accounts. ROLE_USER is left out because every
     * account has it implicitly (see User::getRoles()) and it is never stored.
     *
     * @var string[]
     */
    public const ALL = [
        self::ADMIN,
        self::MANAGER,
        self::TEAMER,
        self::CUSTOMER,
        self::HOUSE_MANAGER,
        self::GROUPS_ADMIN,
        self::GROUPS_MANAGER,
        self::EMPLOYEE,
    ];

    /**
     * Roles granted outright, without an approval step. ROLE_CUSTOMER is never claimed by BusPro —
     * it is the fallback for an account left without any effective role, and exclusive with the
     * others. ROLE_EMPLOYEE is not claimed by BusPro either: it is derived from the account's own
     * email domain (see EmployeeDomainMatcher) and, being effective, displaces that fallback.
     *
     * @var string[]
     */
    public const UNCONDITIONAL = [
        self::TEAMER,
        self::CUSTOMER,
        self::EMPLOYEE,
    ];

    /**
     * Roles the CRM only nominates for. Many people can edit CRM selections in the BusPro
     * backend, so honouring these directly would let anybody make themselves an administrator.
     *
     * @var string[]
     */
    public const ADMINISTRATIVE = [
        self::ADMIN,
        self::MANAGER,
        self::HOUSE_MANAGER,
        self::GROUPS_ADMIN,
        self::GROUPS_MANAGER,
    ];

    /**
     * Roles nobody may approve for their own account. ROLE_ADMIN outranks every check in this
     * application, including the approval surface itself, so it always takes a second
     * administrator. The remaining administrative roles grant less than what an approver
     * already holds, so requiring a second pair of eyes for them would only lock out the
     * single-administrator case for no gain.
     *
     * @var string[]
     */
    public const SELF_APPROVAL_FORBIDDEN = [
        self::ADMIN,
    ];

    /**
     * The marker standing for a role that the CRM claims but nobody has approved.
     */
    public static function pending(string $role): string
    {
        return $role.self::PENDING_SUFFIX;
    }

    /**
     * The roles actually stored on an account — everything except the implicit ROLE_USER,
     * which User::getRoles() prepends and which is never stored. Markers included.
     *
     * @param string[] $roles
     *
     * @return string[]
     */
    public static function assignedOnly(array $roles): array
    {
        return array_values(array_diff($roles, [self::USER]));
    }

    /**
     * The roles that actually grant something: no ROLE_USER, no markers.
     *
     * @param string[] $roles
     *
     * @return string[]
     */
    public static function effectiveOnly(array $roles): array
    {
        return array_values(array_filter(
            self::assignedOnly($roles),
            static fn (string $role): bool => false === self::isPending($role),
        ));
    }

    /**
     * The markers on an account: administrative roles the CRM claims, awaiting approval.
     *
     * @param string[] $roles
     *
     * @return string[]
     */
    public static function pendingOnly(array $roles): array
    {
        return array_values(array_filter($roles, static fn (string $role): bool => self::isPending($role)));
    }

    /**
     * The roles behind those markers, labelled — what an approver acts on.
     *
     * @param string[] $roles
     *
     * @return array<string, string> role => label
     */
    public static function nominatedFrom(array $roles): array
    {
        $labels = self::labels();
        $nominated = [];

        foreach (self::pendingOnly($roles) as $marker) {
            $role = self::realRole($marker);

            if (\in_array($role, self::ADMINISTRATIVE, true)) {
                $nominated[$role] = $labels[$role];
            }
        }

        return $nominated;
    }

    /**
     * The whole policy, applied on every login.
     *
     * 1. revoke everything the CRM no longer claims — granted roles and markers alike, which is
     *    what makes BusPro the source of truth;
     * 2. grant the unconditional roles it claims;
     * 3. mark every administrative role it claims that is not granted already. This runs after
     *    the revocation, so a role just revoked is not immediately marked again, and an approved
     *    role is never marked a second time;
     * 4. fall back to ROLE_CUSTOMER when nothing effective is left.
     *
     * Nothing here can raise a privilege: step 3 only ever produces markers.
     *
     * @param string[] $storedRoles
     * @param string[] $claimedRoles what the CRM reports, plus the roles derived from the account
     *                               itself (ROLE_EMPLOYEE); anything outside self::ALL is ignored
     *
     * @return string[]
     */
    public static function sync(array $storedRoles, array $claimedRoles): array
    {
        $claimed = array_values(array_intersect(self::ALL, array_unique($claimedRoles)));

        $roles = array_values(array_filter(
            self::assignedOnly($storedRoles),
            static fn (string $role): bool => \in_array(self::realRole($role), $claimed, true),
        ));

        foreach (array_intersect($claimed, self::UNCONDITIONAL) as $role) {
            $roles[] = $role;
        }

        foreach (array_intersect($claimed, self::ADMINISTRATIVE) as $role) {
            if (false === \in_array($role, $roles, true)) {
                $roles[] = self::pending($role);
            }
        }

        return self::withCustomerFallback(array_values(array_unique($roles)));
    }

    /**
     * Turns a marker into the role it stands for. Refuses anything the account is not nominated
     * for, so neither a hand-crafted request nor a claim revoked while the confirmation dialog
     * was open can grant a role the CRM never reported.
     *
     * @param string[] $storedRoles
     *
     * @return string[]
     *
     * @throws \InvalidArgumentException when $role is not pending on this account
     */
    public static function approve(array $storedRoles, string $role): array
    {
        $roles = self::assignedOnly($storedRoles);

        if (false === \in_array(self::pending($role), $roles, true)) {
            throw new \InvalidArgumentException(sprintf('The role "%s" is not pending approval.', $role));
        }

        $roles = array_diff($roles, [self::pending($role)]);
        $roles[] = $role;

        return self::withCustomerFallback(array_values(array_unique($roles)));
    }

    /**
     * Everybody without an effective role is a customer, and nobody with one is. The fallback is
     * a fallback, not a baseline — ROLE_CUSTOMER and ROLE_TEAMER are mutually exclusive on
     * purpose.
     *
     * @param string[] $roles
     *
     * @return string[]
     */
    private static function withCustomerFallback(array $roles): array
    {
        if ([] === array_diff(self::effectiveOnly($roles), [self::CUSTOMER])) {
            return array_values(array_unique([...$roles, self::CUSTOMER]));
        }

        return array_values(array_diff($roles, [self::CUSTOMER]));
    }

    private static function isPending(string $role): bool
    {
        return str_ends_with($role, self::PENDING_SUFFIX);
    }

    private static function realRole(string $role): string
    {
        return self::isPending($role)
            ? substr($role, 0, -\strlen(self::PENDING_SUFFIX))
            : $role;
    }

    /**
     * @return array<string, string> role => label
     */
    public static function labels(): array
    {
        $labels = [
            self::ADMIN => 'Administration',
            self::MANAGER => 'Manager:in',
            self::TEAMER => 'Teamer:in',
            self::CUSTOMER => 'Kund:in',
            self::HOUSE_MANAGER => 'Hausleitung',
            self::GROUPS_ADMIN => 'Preisrechner Admin',
            self::GROUPS_MANAGER => 'Preisrechner',
            self::EMPLOYEE => 'Mitarbeiter:in',
        ];

        foreach (self::ADMINISTRATIVE as $role) {
            $labels[self::pending($role)] = $labels[$role].' (nicht freigeschaltet)';
        }

        return $labels;
    }
}