<?php

namespace Modules\Core\Order\Services;

use Lunar\Models\Order;
use Modules\Core\Payment\Models\PaymentMethod;

/**
 * Two status sequences — carrier, pickup (Order::isStorePickupOrder()) —
 * NOT four. Payment method (prepaid vs. cash-on-delivery) does not affect
 * the status SEQUENCE at all; it only affects Order::paid, an entirely
 * separate field this class also offers a transition for (see
 * canMarkPaid()). `status` never includes a "paid" step — COD
 * reconciliation can happen at any point in, or after, the fulfillment
 * journey (same-day to months later), so it cannot occupy a fixed slot in
 * a linear sequence.
 */
class OrderStatusFlow
{
    private const FLOW_CARRIER = [
        'awaiting_payment', 'processing', 'ready_for_dispatch', 'dispatched',
        'delivered', 'completed', 'return_requested', 'returned',
    ];

    private const FLOW_PICKUP = [
        'awaiting_payment', 'processing', 'ready_for_pickup', 'picked_up',
        'completed', 'return_requested', 'returned',
    ];

    private const REFUND_OPTIONS = ['partially_refunded', 'refunded'];

    private const RETURN_ELIGIBLE_FROM = ['delivered', 'picked_up', 'completed'];

    public function resolveFlow(Order $order): array
    {
        return $order->isStorePickupOrder() ? self::FLOW_PICKUP : self::FLOW_CARRIER;
    }

    /**
     * Order.meta['payment_method'] (written by
     * Modules\Core\Checkout\Services\CheckoutService::initiatePayment())
     * is the durable source of truth. Falls back to the most recent
     * Transaction.driver (a payment TYPE slug) only if meta is missing —
     * e.g. an order placed before this field existed.
     */
    public function isCod(Order $order): bool
    {
        $type = $order->meta['payment_method'] ?? $order->transactions()->latest('id')->value('driver');

        if ($type === null) {
            return false;
        }

        return PaymentMethod::where('type', $type)->value('driver') === 'cash-on-delivery';
    }

    /**
     * @return array<string, string> value => label — every status in the
     *   order's own branch (carrier or pickup), plus the refund options,
     *   for a manual-override "New status" select. Deliberately not
     *   filtered to nextOptions()'s guided next-step(s) — staff can jump
     *   to any status in their branch, including reverting to an earlier
     *   one (e.g. undoing a mistaken click). transitionTo() still
     *   validates $to is actually a member of this set server-side.
     */
    public function allOptions(Order $order): array
    {
        $statuses = [...$this->resolveFlow($order), ...self::REFUND_OPTIONS, 'delivery_failed'];

        return collect($statuses)
            ->unique()
            ->mapWithKeys(fn (string $status) => [$status => $this->label($status)])
            ->all();
    }

    /**
     * @return array<string, string> value => label — status-sequence
     *   transitions offered as the guided next step(s). Does not include
     *   the "mark paid" pseudo-option — see canMarkPaid().
     */
    public function nextOptions(Order $order): array
    {
        $flow = $this->resolveFlow($order);
        $current = $order->status;
        $position = array_search($current, $flow, true);

        $options = [];

        if ($position !== false && isset($flow[$position + 1])) {
            $options[] = $flow[$position + 1];
        }

        // delivery_failed — a possible outcome of any delivery attempt,
        // carrier flow only, checked on $current directly (not on the
        // flow's literal next value) since it's a branch on the attempt
        // itself, not on sequence position.
        if ($current === 'dispatched') {
            $options[] = 'delivery_failed';
        }

        // From delivery_failed: retry dispatch, or give up and treat as
        // a return.
        if ($current === 'delivery_failed') {
            array_push($options, 'dispatched', 'return_requested');
        }

        if (in_array($current, self::RETURN_ELIGIBLE_FROM, true)) {
            $options[] = 'return_requested';
        }

        if ($current === 'return_requested') {
            $options[] = 'returned';
        }

        if ($current === 'returned') {
            array_push($options, ...self::REFUND_OPTIONS);
        }

        return collect($options)
            ->unique()
            ->mapWithKeys(fn (string $status) => [$status => $this->label($status)])
            ->all();
    }

    /**
     * Whether the "mark paid" option should be offered right now —
     * entirely independent of $order->status. True whenever this is a
     * cash-on-delivery order and payment hasn't been recorded yet,
     * regardless of fulfillment progress (before OR after completed).
     */
    public function canMarkPaid(Order $order): bool
    {
        return ! $order->paid && $this->isCod($order);
    }

    /**
     * Whether moving $order to $to is a valid transition from its CURRENT
     * status — the single source of truth for "is this a legal next step,"
     * so a caller reacting to an external event (a carrier tracking
     * checkpoint, a staff action) doesn't need to hardcode its own "only
     * fire from status X" guard duplicating what nextOptions() already
     * knows. See e.g. Modules\Core\Order\Listeners\
     * AdvanceFulfillmentOnCarrierCheckpoint, which used to compare
     * $order->status to a literal 'ready_for_dispatch' inline instead of
     * asking this class.
     */
    public function isValidTransition(Order $order, string $to): bool
    {
        return array_key_exists($to, $this->nextOptions($order));
    }

    private function label(string $status): string
    {
        return (string) str($status)->replace('_', ' ')->title();
    }
}