<?php

namespace Modules\ApprovalWorkflow\Services;

use App\Models\User;
use Illuminate\Database\Eloquent\Model;
use Modules\ApprovalWorkflow\Enums\ApprovalChainStatus;
use Modules\ApprovalWorkflow\Enums\ApprovalStepStatus;
use Modules\ApprovalWorkflow\Events\ApprovalCompleted;
use Modules\ApprovalWorkflow\Events\ApprovalRequired;
use Modules\ApprovalWorkflow\Events\StepApproved;
use Modules\ApprovalWorkflow\Events\StepRejected;
use Modules\ApprovalWorkflow\Models\ApprovalChain;
use Modules\ApprovalWorkflow\Models\ApprovalStep;

class ApprovalService
{
    /**
     * Create a new approval chain for any morphable model.
     *
     * @param array<int, int> $approverIds — ordered list of user IDs
     */
    public function createChain(
        Model $approvable,
        array $approverIds,
        string $type = 'general',
        ?int $initiatedBy = null,
        ?string $notes = null,
    ): ApprovalChain {
        $chain = ApprovalChain::create([
            'approvable_type' => $approvable->getMorphClass(),
            'approvable_id' => $approvable->getKey(),
            'type' => $type,
            'status' => ApprovalChainStatus::Pending,
            'initiated_by' => $initiatedBy,
            'notes' => $notes,
        ]);

        foreach ($approverIds as $order => $userId) {
            ApprovalStep::create([
                'approval_chain_id' => $chain->id,
                'approver_id' => $userId,
                'order' => $order,
                'status' => ApprovalStepStatus::Pending,
            ]);
        }

        // Auto-transition to InReview and notify first approver
        $chain->transitionTo(ApprovalChainStatus::InReview);
        $firstStep = $chain->currentStep();
        if ($firstStep) {
            ApprovalRequired::dispatch($chain, $firstStep);
        }

        return $chain->load('steps.approver');
    }

    /**
     * Approve the current pending step.
     */
    public function approve(ApprovalChain $chain, User $approver, ?string $notes = null): ApprovalChain
    {
        $step = $this->getCurrentStepForApprover($chain, $approver);

        $step->update([
            'status' => ApprovalStepStatus::Approved,
            'notes' => $notes,
            'acted_at' => now(),
        ]);

        StepApproved::dispatch($chain, $step);

        // Check if all steps are approved
        if ($chain->isFullyApproved()) {
            $chain->transitionTo(ApprovalChainStatus::Approved);
            ApprovalCompleted::dispatch($chain);
        } else {
            // Notify next approver
            $nextStep = $chain->currentStep();
            if ($nextStep) {
                ApprovalRequired::dispatch($chain, $nextStep);
            }
        }

        return $chain->fresh('steps.approver');
    }

    /**
     * Reject the current pending step (rejects the entire chain).
     */
    public function reject(ApprovalChain $chain, User $approver, ?string $notes = null): ApprovalChain
    {
        $step = $this->getCurrentStepForApprover($chain, $approver);

        $step->update([
            'status' => ApprovalStepStatus::Rejected,
            'notes' => $notes,
            'acted_at' => now(),
        ]);

        // Skip remaining steps
        $chain->steps()
            ->where('order', '>', $step->order)
            ->where('status', 'pending')
            ->update(['status' => ApprovalStepStatus::Skipped->value]);

        $chain->transitionTo(ApprovalChainStatus::Rejected);

        StepRejected::dispatch($chain, $step);
        ApprovalCompleted::dispatch($chain);

        return $chain->fresh('steps.approver');
    }

    public function getNextApprover(ApprovalChain $chain): ?User
    {
        $step = $chain->currentStep();
        return $step?->approver;
    }

    private function getCurrentStepForApprover(ApprovalChain $chain, User $approver): ApprovalStep
    {
        $step = $chain->currentStep();

        if (!$step) {
            throw new \InvalidArgumentException('No pending step found in this approval chain.');
        }

        if ($step->approver_id !== $approver->id) {
            throw new \InvalidArgumentException('You are not the current approver for this step.');
        }

        return $step;
    }
}