<?php

namespace Modules\Core\Privacy\Services;

use Illuminate\Contracts\Auth\Authenticatable;
use Illuminate\Database\Eloquent\Model;
use Illuminate\Support\Facades\Event;
use Illuminate\Support\Facades\Log;
use Lunar\Base\LunarUser;
use Lunar\Models\Customer;
use Modules\Core\Auth\Models\Staff;
use Modules\Core\Privacy\Contracts\PersonalDataProvider;
use Modules\Core\Privacy\DTOs\CustomerSubject;
use Modules\Core\Privacy\DTOs\ErasureReport;
use Modules\Core\Privacy\DTOs\ProviderErasureResult;
use Modules\Core\Privacy\DTOs\UserSubject;
use Modules\Core\Privacy\Enums\ErasureOutcome;
use Modules\Core\Privacy\Enums\ErasureRequestStatus;
use Modules\Core\Privacy\Enums\ExportRequestStatus;
use Modules\Core\Privacy\Events\UserErasureRequested;
use Modules\Core\Privacy\Jobs\ExportDataSubjectJob;
use Modules\Core\Privacy\Models\DataErasureRequest;
use Modules\Core\Privacy\Models\DataExportRequest;
use Throwable;

/**
 * Entry point for right-of-access and right-of-erasure requests, split into two
 * independent scopes — see docs/privacy.md "User-scope vs Customer-scope":
 *
 *   - *ForCustomer(): erases/exports one business account's own data (orders,
 *     addresses, the account record itself). Never touches any linked User's
 *     login or personal identity — a Customer erasure request must not deactivate
 *     or destroy access for anyone who works there.
 *   - *ForUser(): erases/exports one individual's own identity (login, name,
 *     email) wherever it appears, and detaches them from every Customer account
 *     they're linked to as part of erasure — without touching any Customer
 *     account's own data or any other User still linked to it.
 *
 * A Customer (business account) can have many linked Users, and one User can be
 * linked to many Customer accounts (B2B multi-seat access — see docs/modules.md
 * "Customer/User Pairing"), so these are genuinely different operations with
 * different blast radii, not one flow with an optional cascade.
 *
 * Both directions are handled as requests, not immediate synchronous actions:
 * requestExport*() queues the (potentially slow) work of gathering every
 * provider's data and writing a file, rather than blocking whatever triggered it.
 * requestErasure*() opens a cancellable grace-period request (deactivating the
 * account for a User-scoped request only — see below) — the same shape as
 * Shopify's own account-deletion flow: a window where the subject can change
 * their mind before anything is actually erased.
 */
class PrivacyService
{
    public function __construct(private readonly PrivacyManager $manager) {}

    /**
     * Creates a DataExportRequest (fast — one insert) and dispatches
     * ExportDataSubjectJob to do the actual gathering/writing work. The job fires
     * PersonalDataGathered once every provider's data is collected;
     * Modules\Core\Privacy\Listeners\WriteExportToCsvListener turns that into a file
     * and fires PersonalDataExportFileWritten — a consuming app registers its own
     * notification against that event (see docs/privacy.md).
     */
    public function requestExportForCustomer(Customer $customer): DataExportRequest
    {
        return $this->createExportRequest($customer->getMorphClass(), $customer->id, null);
    }

    public function requestExportForUser(Authenticatable&LunarUser $user): DataExportRequest
    {
        return $this->createExportRequest($user->getMorphClass(), $user->id, $user->email);
    }

    private function createExportRequest(string $subjectType, int $subjectId, ?string $email): DataExportRequest
    {
        $request = DataExportRequest::create([
            'subject_type' => $subjectType,
            'subject_id' => $subjectId,
            'email' => $email,
            'status' => ExportRequestStatus::Pending,
        ]);

        ExportDataSubjectJob::dispatch($request);

        return $request;
    }

    /**
     * Opens a grace-period erasure request for the Customer's own data. Deactivates
     * NO User — erasing a business account must not destroy anyone's login access,
     * even the account's own primary contact. Nothing is actually erased until
     * privacy:process-erasure-requests picks this up once scheduled_for has
     * passed, unless cancelErasure() is called first.
     *
     * $requestedBy is the Customer themselves (self-service deletion), a Staff
     * member acting on their behalf, or a User — the User case is for
     * Modules\Core\Privacy\Listeners\CascadeCustomerErasureListener, where erasing
     * a User leaves a Customer with no remaining user: the User is a real,
     * meaningful "who caused this," even though they didn't directly request the
     * Customer's own erasure. $causedByRequestId links a cascade-created request
     * back to the User erasure request that triggered it, so
     * CancelErasureOnLoginListener can revert exactly that cascade on login,
     * without touching an unrelated, independently-requested Customer erasure.
     */
    public function requestErasureForCustomer(
        Customer $customer,
        Customer|Staff|(Authenticatable&LunarUser) $requestedBy,
        ?int $causedByRequestId = null,
    ): DataErasureRequest {
        return DataErasureRequest::create([
            'subject_type' => $customer->getMorphClass(),
            'subject_id' => $customer->id,
            'email' => null,
            'requested_by_type' => $requestedBy->getMorphClass(),
            'requested_by_id' => $requestedBy->getKey(),
            'status' => ErasureRequestStatus::Pending,
            'scheduled_for' => now()->addDays(config('core.privacy.grace_period_days', 30)),
            'caused_by_request_id' => $causedByRequestId,
        ]);
    }

    /**
     * Opens a grace-period erasure request for one individual and deactivates
     * their login immediately (blocks it — see Modules\Core\Auth\Services\
     * UserOtpService — without touching any Customer account's data). $requestedBy
     * is either the User themselves (self-service deletion) or a Staff member
     * acting on their behalf.
     */
    public function requestErasureForUser(Authenticatable&LunarUser $user, (Authenticatable&LunarUser)|Staff $requestedBy): DataErasureRequest
    {
        $request = DataErasureRequest::create([
            'subject_type' => $user->getMorphClass(),
            'subject_id' => $user->id,
            'email' => $user->email,
            'requested_by_type' => $requestedBy->getMorphClass(),
            'requested_by_id' => $requestedBy->getKey(),
            'status' => ErasureRequestStatus::Pending,
            'scheduled_for' => now()->addDays(config('core.privacy.grace_period_days', 30)),
        ]);

        $this->setUserDeactivated($user->id, true);

        // CascadeCustomerErasureListener implements ShouldQueue, so this just
        // enqueues a job rather than running inline — no transaction wrapping
        // needed here, since the cascade check happens as an independent,
        // separately-retryable unit of work after this request is already
        // committed, not as part of this same call.
        Event::dispatch(new UserErasureRequested($request));

        return $request;
    }

    /**
     * Erases a Customer's data right now, bypassing the grace period entirely.
     * Staff-only by construction — $requestedBy is typed to Staff specifically,
     * so a self-service/customer-facing code path cannot reach this method at
     * all, only accidentally call it with the wrong actor type and get a
     * compile-time error. This exists for a formal legal request or regulator
     * inquiry that genuinely requires immediate action — not a convenience
     * option for an impatient customer. The grace period is deliberately not
     * skippable from any customer-facing flow; see docs/privacy.md.
     */
    public function requestImmediateErasureForCustomer(Customer $customer, Staff $requestedBy): ErasureReport
    {
        $request = DataErasureRequest::create([
            'subject_type' => $customer->getMorphClass(),
            'subject_id' => $customer->id,
            'email' => null,
            'requested_by_type' => $requestedBy->getMorphClass(),
            'requested_by_id' => $requestedBy->getKey(),
            'status' => ErasureRequestStatus::Pending,
            'scheduled_for' => now(),
        ]);

        return $this->completeErasure($request);
    }

    /**
     * Erases a User's data right now, bypassing the grace period entirely.
     * Staff-only by construction — see requestImmediateErasureForCustomer().
     *
     * Still fires UserErasureRequested — and deliberately BEFORE completeErasure()
     * runs, not after — so Modules\Core\Privacy\Listeners\
     * CascadeCustomerErasureListener sees the User still linked to their Customers
     * (completeErasure() -> CustomerDataProvider::eraseForUser() is what detaches
     * the pivot). The User's own erasure is immediate, but any Customer left
     * orphaned by it still gets a normal grace-period erasure request, not an
     * immediate one — an orphaned Customer isn't itself the subject of the
     * original urgent request.
     */
    public function requestImmediateErasureForUser(Authenticatable&LunarUser $user, Staff $requestedBy): ErasureReport
    {
        $request = DataErasureRequest::create([
            'subject_type' => $user->getMorphClass(),
            'subject_id' => $user->id,
            'email' => $user->email,
            'requested_by_type' => $requestedBy->getMorphClass(),
            'requested_by_id' => $requestedBy->getKey(),
            'status' => ErasureRequestStatus::Pending,
            'scheduled_for' => now(),
        ]);

        $this->setUserDeactivated($user->id, true);

        // Queued (see requestErasureForUser()) — the cascade job may run before
        // or after completeErasure() below detaches the pivot. Either is fine:
        // CascadeCustomerErasureListener re-reads $user->customers fresh when it
        // runs, so it only cascades if this User is still linked at that point.
        // If completeErasure() detaches first, the queued job simply finds no
        // Customers left to check and no-ops — never a wrong cascade, at worst a
        // missed one on a race that immediate (staff-triggered, rare) erasure
        // doesn't need to guard against as tightly as the grace-period path.
        Event::dispatch(new UserErasureRequested($request));

        return $this->completeErasure($request);
    }

    /**
     * Cancels a pending request. For a User-scoped request, reactivates the
     * account (see requestErasureForUser()). A Customer-scoped request never
     * deactivated anything, so there's nothing to reactivate for it. No-op
     * (returns false) if the request isn't pending — e.g. already completed or
     * cancelled.
     */
    public function cancelErasure(DataErasureRequest $request): bool
    {
        if (! $request->isPending()) {
            return false;
        }

        $request->update([
            'status' => ErasureRequestStatus::Cancelled,
            'cancelled_at' => now(),
        ]);

        if (! $request->isForCustomer()) {
            $this->setUserDeactivated($request->subject_id, false);
        }

        return true;
    }

    /**
     * Actually erases the data for a due request: runs every registered
     * provider's *ForCustomer() or *ForUser() method (whichever matches the
     * request's subject), records the outcome on the request, and marks it
     * completed. Called by privacy:process-erasure-requests — not meant to be
     * called directly for a request that hasn't passed its grace period, since
     * that defeats the point of the window; ProcessErasureRequestsCommand
     * enforces isDue() before calling this.
     *
     * Each provider call is caught individually — a provider throwing (a bug,
     * an unexpected DB state) converts to ErasureOutcome::Failed rather than
     * aborting the whole array_map, so one broken provider never discards
     * every OTHER provider's already-completed erasure for this same request.
     * Without this, the $request->update() below would never run at all on a
     * throw, silently leaving providers that already succeeded unrecorded and
     * the request stuck Pending forever. Logged via Log::error() so a thrown
     * provider is still visible to staff, not just swallowed into "Failed."
     */
    public function completeErasure(DataErasureRequest $request): ErasureReport
    {
        if ($request->isForCustomer()) {
            $subject = new CustomerSubject(customerId: $request->subject_id);
            $results = array_map(
                fn (PersonalDataProvider $provider) => $this->safeErase($provider, 'eraseForCustomer', $subject),
                $this->manager->providers()
            );
        } else {
            $subject = new UserSubject(userId: $request->subject_id, email: $request->email);
            $results = array_map(
                fn (PersonalDataProvider $provider) => $this->safeErase($provider, 'eraseForUser', $subject),
                $this->manager->providers()
            );
        }

        $report = new ErasureReport($subject, $results);

        $request->update([
            'status' => ErasureRequestStatus::Completed,
            'completed_at' => now(),
            'report' => array_map(
                fn (ProviderErasureResult $result) => [
                    'provider' => $result->provider,
                    'outcome' => $result->outcome->value,
                    'reason' => $result->reason,
                ],
                $results
            ),
        ]);

        return $report;
    }

    private function setUserDeactivated(int $userId, bool $deactivated): void
    {
        $model = config('auth.providers.users.model');

        /** @var class-string<Model> $model */
        $model::where('id', $userId)->update([
            'deactivated_at' => $deactivated ? now() : null,
        ]);
    }

    /**
     * @param  'eraseForCustomer'|'eraseForUser'  $method
     */
    private function safeErase(PersonalDataProvider $provider, string $method, CustomerSubject|UserSubject $subject): ProviderErasureResult
    {
        try {
            return $provider->{$method}($subject);
        } catch (Throwable $e) {
            Log::error("Privacy provider {$provider->name()}::{$method}() threw during erasure", [
                'provider' => $provider->name(),
                'exception' => $e,
            ]);

            return new ProviderErasureResult($provider->name(), ErasureOutcome::Failed, $e->getMessage());
        }
    }
}