<?php

namespace App\Services;

use App\Mail\CustomerEmailChangeBlockedMail;
use App\Mail\CustomerEmailChangeMail;
use App\Models\ShoppingUser;
use App\Models\ShoppingUserEmailChange;
use App\Models\UserAbo;
use App\User;
use Illuminate\Support\Collection;
use Illuminate\Support\Facades\DB;
use Illuminate\Support\Facades\Log;
use Illuminate\Support\Facades\Mail;
use Illuminate\Support\Str;

/**
 * Changing a customer's e-mail address. The address is the customer's portal login and
 * the key the portal uses to find their abo, so a consultant may not switch it silently:
 * the new address only becomes active after the customer confirmed it via the link sent
 * to it. On activation all entries of the customer with the old address and their abos
 * move to the new address together.
 */
class CustomerEmailChangeService
{
    public const TTL_HOURS = 168;

    public const STATUS_CONFIRMED = 'confirmed';

    public const STATUS_INVALID = 'invalid';

    public const STATUS_CONFLICT = 'conflict';

    public const CONFLICT_CONSULTANT_ACCOUNT = 'consultant_account';

    public const CONFLICT_OTHER_CONSULTANT = 'other_consultant';

    public function changesAddress(ShoppingUser $shoppingUser, ?string $newEmail): bool
    {
        return filled($newEmail) && ! $this->sameEmail($shoppingUser->billing_email, $newEmail);
    }

    /**
     * A customer without a real address yet (placeholder) has no login to lose, so only
     * replacing a real address needs the customer's confirmation.
     */
    public function requiresConfirmation(ShoppingUser $shoppingUser, ?string $newEmail): bool
    {
        return ! $this->hasPlaceholderEmail($shoppingUser) && $this->changesAddress($shoppingUser, $newEmail);
    }

    /**
     * Customer sovereignty: the e-mail is the main indicator who a customer belongs to. A
     * consultant may not take over an address that already belongs to an active consultant
     * account or to a customer of another consultant.
     *
     * @return self::CONFLICT_*|null
     */
    public function ownershipConflict(ShoppingUser $shoppingUser, string $newEmail): ?string
    {
        $newEmail = trim($newEmail);

        if (User::where('email', $newEmail)->where('active', 1)->exists()) {
            return self::CONFLICT_CONSULTANT_ACCOUNT;
        }

        return $this->customersOfOtherConsultants($shoppingUser, $newEmail)->isNotEmpty()
            ? self::CONFLICT_OTHER_CONSULTANT
            : null;
    }

    /**
     * Records a change rejected because of customer sovereignty, so it stays visible in the
     * admin overview until handled, and informs the customer sovereignty inbox.
     */
    public function reportConflict(ShoppingUser $shoppingUser, string $newEmail, ?int $requestedBy = null, ?ShoppingUserEmailChange $change = null): ShoppingUserEmailChange
    {
        $newEmail = trim($newEmail);
        $owners = $this->customersOfOtherConsultants($shoppingUser, $newEmail)
            ->map(fn (ShoppingUser $customer) => $customer->member?->email)
            ->filter()
            ->unique()
            ->values()
            ->all();

        $attributes = ['token_hash' => null, 'blocked_at' => now()];
        if ($change) {
            $change->forceFill($attributes)->save();
        } else {
            $change = ShoppingUserEmailChange::create($attributes + [
                'shopping_user_id' => $shoppingUser->id,
                'number' => $shoppingUser->number,
                'old_email' => $shoppingUser->billing_email,
                'new_email' => $newEmail,
                'requested_by_user_id' => $requestedBy,
            ]);
        }

        Log::warning('CustomerEmailChange: Änderung wegen Kundenhoheit abgelehnt', [
            'shopping_user_id' => $shoppingUser->id,
            'number' => $shoppingUser->number,
            'new_email' => $newEmail,
            'requested_by_user_id' => $requestedBy,
            'owners' => $owners,
        ]);

        Mail::to(config('app.priority_mail'))->send(new CustomerEmailChangeBlockedMail(
            $shoppingUser,
            $newEmail,
            $requestedBy ? User::find($requestedBy)?->email : null,
            $owners,
        ));

        return $change;
    }

    public function resolveBlocked(ShoppingUserEmailChange $change, ?int $resolvedBy = null): void
    {
        $change->forceFill(['resolved_at' => now(), 'resolved_by_user_id' => $resolvedBy])->save();
    }

    /**
     * Withdraws an open request; the link in the mail stops working.
     */
    public function discard(ShoppingUserEmailChange $change): void
    {
        $change->forceFill(['token_hash' => null, 'expires_at' => now()])->save();
    }

    /**
     * Starts the confirmation for a new address and sends the link to it. Older open
     * requests of the same customer are replaced.
     */
    public function request(ShoppingUser $shoppingUser, string $newEmail, ?int $requestedBy = null): ShoppingUserEmailChange
    {
        $newEmail = trim($newEmail);
        $token = Str::random(48);

        ShoppingUserEmailChange::forCustomer($shoppingUser)->pending()->delete();

        $change = ShoppingUserEmailChange::create([
            'shopping_user_id' => $shoppingUser->id,
            'number' => $shoppingUser->number,
            'old_email' => $shoppingUser->billing_email,
            'new_email' => $newEmail,
            'token_hash' => ShoppingUserEmailChange::hashToken($token),
            'expires_at' => now()->addHours(self::TTL_HOURS),
            'requested_by_user_id' => $requestedBy,
        ]);

        Mail::to($newEmail)
            ->locale($shoppingUser->language ?: 'de')
            ->send(new CustomerEmailChangeMail($shoppingUser, $token));

        return $change;
    }

    public function findConfirmable(string $token): ?ShoppingUserEmailChange
    {
        $change = ShoppingUserEmailChange::where('token_hash', ShoppingUserEmailChange::hashToken($token))->first();

        return $change && $change->isConfirmable() ? $change : null;
    }

    /**
     * Activates the requested address. Fails when the customer's address was changed in
     * the meantime (an outdated link must not overwrite a newer address) or when the new
     * address has meanwhile been assigned to another consultant (customer sovereignty).
     *
     * @return self::STATUS_*
     */
    public function confirm(ShoppingUserEmailChange $change): string
    {
        $shoppingUser = $change->shopping_user;
        if (! $change->isConfirmable() || ! $shoppingUser || ! $this->sameEmail($shoppingUser->billing_email, $change->old_email)) {
            return self::STATUS_INVALID;
        }

        if ($this->ownershipConflict($shoppingUser, $change->new_email)) {
            $this->reportConflict($shoppingUser, $change->new_email, $change->requested_by_user_id, $change);

            return self::STATUS_CONFLICT;
        }

        DB::transaction(function () use ($change, $shoppingUser) {
            $this->apply($shoppingUser, $change->old_email, $change->new_email);
            $change->forceFill(['confirmed_at' => now(), 'token_hash' => null])->save();
        });

        return self::STATUS_CONFIRMED;
    }

    /**
     * Direct change without confirmation (admin). Logged like a confirmed request.
     */
    public function changeDirectly(ShoppingUser $shoppingUser, string $newEmail, ?int $changedBy = null): void
    {
        $oldEmail = $shoppingUser->billing_email;
        $newEmail = trim($newEmail);

        DB::transaction(function () use ($shoppingUser, $oldEmail, $newEmail, $changedBy) {
            $this->apply($shoppingUser, $oldEmail, $newEmail);
            ShoppingUserEmailChange::forCustomer($shoppingUser)->pending()->delete();
            ShoppingUserEmailChange::create([
                'shopping_user_id' => $shoppingUser->id,
                'number' => $shoppingUser->number,
                'old_email' => $oldEmail,
                'new_email' => $newEmail,
                'confirmed_at' => now(),
                'requested_by_user_id' => $changedBy,
            ]);
        });
    }

    public function pendingFor(ShoppingUser $shoppingUser): ?ShoppingUserEmailChange
    {
        return ShoppingUserEmailChange::forCustomer($shoppingUser)->pending()->latest('id')->first();
    }

    /**
     * Moves all entries of the customer that still carry the old address, plus their
     * customer abos, to the new address.
     *
     * @return array{shopping_users: int, abos: int}
     */
    private function apply(ShoppingUser $shoppingUser, string $oldEmail, string $newEmail): array
    {
        $shoppingUserIds = ShoppingUser::query()
            ->where('billing_email', $oldEmail)
            ->when(
                $shoppingUser->number > 0,
                fn ($query) => $query->where('number', $shoppingUser->number),
                fn ($query) => $query->whereKey($shoppingUser->id),
            )
            ->pluck('id')
            ->push($shoppingUser->id)
            ->unique()
            ->values();

        $updatedShoppingUsers = ShoppingUser::whereIn('id', $shoppingUserIds)->update(['billing_email' => $newEmail]);

        $updatedAbos = UserAbo::query()
            ->whereIn('shopping_user_id', $shoppingUserIds)
            ->where('is_for', 'ot')
            ->where('email', $oldEmail)
            ->update(['email' => $newEmail]);

        $shoppingUser->billing_email = $newEmail;

        Log::info('CustomerEmailChange: E-Mail geändert', [
            'shopping_user_id' => $shoppingUser->id,
            'number' => $shoppingUser->number,
            'old_email' => $oldEmail,
            'new_email' => $newEmail,
            'shopping_users' => $updatedShoppingUsers,
            'abos' => $updatedAbos,
        ]);

        return ['shopping_users' => $updatedShoppingUsers, 'abos' => $updatedAbos];
    }

    /**
     * Customers (with a customer number) of other consultants that use the address.
     *
     * @return Collection<int, ShoppingUser>
     */
    private function customersOfOtherConsultants(ShoppingUser $shoppingUser, string $email): Collection
    {
        return ShoppingUser::query()
            ->with('member')
            ->whereNull('auth_user_id')
            ->whereNotNull('number')
            ->whereNotNull('member_id')
            ->when($shoppingUser->member_id, fn ($query) => $query->where('member_id', '!=', $shoppingUser->member_id))
            ->where('billing_email', $email)
            ->withoutGdprDeleted()
            ->get();
    }

    private function hasPlaceholderEmail(ShoppingUser $shoppingUser): bool
    {
        return (bool) $shoppingUser->faker_mail
            || blank($shoppingUser->billing_email)
            || str_ends_with((string) $shoppingUser->billing_email, '-faker@mivita.care');
    }

    private function sameEmail(?string $a, ?string $b): bool
    {
        return mb_strtolower(trim((string) $a)) === mb_strtolower(trim((string) $b));
    }
}