<?php

namespace App\Services;

/**
 * Encapsulates the project lifecycle state machine.
 */
class ProjectStatusService
{
    /**
     * Valid status transitions for the project state machine.
     * Key = from status, Value = array of valid target statuses
     */
    protected array $statusTransitions = [
        'Pre-sales' => ['SOW Approval'],
        'SOW Approval' => ['Estimation', 'Pre-sales'],
        'Estimation' => ['Estimate Approved', 'SOW Approval'],
        'Estimate Approved' => ['Resource Allocation', 'Estimate Rework'],
        'Resource Allocation' => ['Sprint 0', 'Estimate Approved'],
        'Sprint 0' => ['In Progress', 'Resource Allocation'],
        'In Progress' => ['UAT', 'Sprint 0', 'On Hold'],
        'UAT' => ['Handover / Sign-off', 'In Progress', 'On Hold'],
        'Handover / Sign-off' => ['Closed', 'UAT'],
        'Estimate Rework' => ['Estimation'],
        'On Hold' => ['In Progress', 'Cancelled'],
        'Cancelled' => [],
        'Closed' => [],
    ];

    /**
     * Return the valid target statuses for the provided current status.
     */
    public function getValidTransitions(string $currentStatus): array
    {
        return $this->statusTransitions[$currentStatus] ?? [];
    }

    /**
     * Determine if a transition from the current status to the target is allowed.
     */
    public function canTransition(string $currentStatus, string $targetStatus): bool
    {
        return in_array($targetStatus, $this->getValidTransitions($currentStatus), true);
    }

    /**
     * Return statuses that do not allow further transitions.
     */
    public function getTerminalStatuses(): array
    {
        return array_keys(array_filter($this->statusTransitions, static fn (array $targets): bool => $targets === []));
    }

    /**
     * Determine if a status requires an approved estimate before entering.
     */
    public function requiresEstimate(string $statusName): bool
    {
        return $statusName === 'Estimate Approved';
    }
}