<?php

declare(strict_types=1);

namespace App\Services\Findings;

use App\Models\Finding;
use App\Models\FindingException;
use App\Models\FindingExceptionDecision;
use Carbon\CarbonImmutable;
use Illuminate\Support\Carbon;

final class FindingRiskGovernanceResolver
{
    public function resolveExceptionStatus(FindingException $exception, ?CarbonImmutable $now = null): string
    {
        $now ??= CarbonImmutable::instance(now());

        $status = (string) $exception->status;

        if (in_array($status, [
            FindingException::STATUS_REJECTED,
            FindingException::STATUS_REVOKED,
            FindingException::STATUS_SUPERSEDED,
        ], true)) {
            return $status;
        }

        if ($status === FindingException::STATUS_PENDING) {
            return FindingException::STATUS_PENDING;
        }

        $expiresAt = $exception->expires_at instanceof Carbon
            ? CarbonImmutable::instance($exception->expires_at)
            : null;

        if ($expiresAt instanceof CarbonImmutable && $expiresAt->lessThanOrEqualTo($now)) {
            return FindingException::STATUS_EXPIRED;
        }

        if ($this->isExpiring($exception, $now)) {
            return FindingException::STATUS_EXPIRING;
        }

        return FindingException::STATUS_ACTIVE;
    }

    public function resolveValidityState(FindingException $exception, ?CarbonImmutable $now = null): string
    {
        if ($exception->isPendingRenewal()) {
            return $this->resolveApprovedValidityState($exception, $now);
        }

        return match ($this->resolveExceptionStatus($exception, $now)) {
            FindingException::STATUS_ACTIVE => FindingException::VALIDITY_VALID,
            FindingException::STATUS_EXPIRING => FindingException::VALIDITY_EXPIRING,
            FindingException::STATUS_EXPIRED => FindingException::VALIDITY_EXPIRED,
            FindingException::STATUS_REVOKED => FindingException::VALIDITY_REVOKED,
            FindingException::STATUS_REJECTED => FindingException::VALIDITY_REJECTED,
            default => FindingException::VALIDITY_MISSING_SUPPORT,
        };
    }

    public function resolveFindingState(Finding $finding, ?FindingException $exception = null, ?CarbonImmutable $now = null): string
    {
        $exception ??= $finding->relationLoaded('findingException')
            ? $finding->findingException
            : $finding->findingException()->first();

        $findingIsRiskAccepted = $finding->isRiskAccepted();

        if (! $exception instanceof FindingException) {
            return $findingIsRiskAccepted
                ? 'risk_accepted_without_valid_exception'
                : 'ungoverned';
        }

        if (! $findingIsRiskAccepted) {
            return $exception->isPending()
                ? 'pending_exception'
                : 'ungoverned';
        }

        if ($exception->isPendingRenewal()) {
            return match ($this->resolveApprovedValidityState($exception, $now)) {
                FindingException::VALIDITY_VALID => 'valid_exception',
                FindingException::VALIDITY_EXPIRING => 'expiring_exception',
                FindingException::VALIDITY_EXPIRED => 'expired_exception',
                default => 'pending_exception',
            };
        }

        return match ($this->resolveExceptionStatus($exception, $now)) {
            FindingException::STATUS_PENDING => 'pending_exception',
            FindingException::STATUS_ACTIVE => 'valid_exception',
            FindingException::STATUS_EXPIRING => 'expiring_exception',
            FindingException::STATUS_EXPIRED => 'expired_exception',
            FindingException::STATUS_REVOKED => 'revoked_exception',
            FindingException::STATUS_REJECTED => 'rejected_exception',
            default => $findingIsRiskAccepted
                ? 'risk_accepted_without_valid_exception'
                : 'ungoverned',
        };
    }

    public function isValidGovernedAcceptedRisk(Finding $finding, ?FindingException $exception = null, ?CarbonImmutable $now = null): bool
    {
        return in_array($this->resolveFindingState($finding, $exception, $now), [
            'valid_exception',
            'expiring_exception',
        ], true);
    }

    public function resolveWarningMessage(Finding $finding, ?FindingException $exception = null, ?CarbonImmutable $now = null): ?string
    {
        $exception ??= $finding->relationLoaded('findingException')
            ? $finding->findingException
            : $finding->findingException()->first();

        if (! $exception instanceof FindingException) {
            return $finding->isRiskAccepted()
                ? 'This finding is marked as accepted risk without a valid exception record.'
                : null;
        }

        $exceptionStatus = $exception->isPendingRenewal()
            ? match ($this->resolveApprovedValidityState($exception, $now)) {
                FindingException::VALIDITY_EXPIRED => FindingException::STATUS_EXPIRED,
                FindingException::VALIDITY_EXPIRING => FindingException::STATUS_EXPIRING,
                FindingException::VALIDITY_VALID => FindingException::STATUS_ACTIVE,
                default => FindingException::STATUS_PENDING,
            }
        : $this->resolveExceptionStatus($exception, $now);

        if ($finding->isRiskAccepted()) {
            return match ($this->resolveFindingState($finding, $exception, $now)) {
                'risk_accepted_without_valid_exception' => 'This finding is marked as accepted risk without a valid exception record.',
                'expired_exception' => 'The linked exception has expired and no longer governs accepted risk.',
                'revoked_exception' => 'The linked exception was revoked and no longer governs accepted risk.',
                'rejected_exception' => 'The linked exception was rejected and does not govern accepted risk.',
                default => null,
            };
        }

        if ($exception->requiresFreshDecisionForFinding($finding)) {
            return 'This finding changed after the earlier exception decision; a fresh decision is required.';
        }

        return match ($exceptionStatus) {
            FindingException::STATUS_EXPIRED => 'The linked exception has expired and no longer governs accepted risk.',
            FindingException::STATUS_REVOKED => 'The linked exception was revoked and no longer governs accepted risk.',
            FindingException::STATUS_REJECTED => 'The linked exception was rejected and does not govern accepted risk.',
            default => null,
        };
    }

    public function syncExceptionState(FindingException $exception, ?CarbonImmutable $now = null): FindingException
    {
        $resolvedStatus = $this->resolveExceptionStatus($exception, $now);
        $resolvedValidityState = $this->resolveValidityState($exception, $now);

        if ((string) $exception->status === $resolvedStatus && (string) $exception->current_validity_state === $resolvedValidityState) {
            return $exception;
        }

        $exception->forceFill([
            'status' => $resolvedStatus,
            'current_validity_state' => $resolvedValidityState,
        ])->save();

        return $exception->refresh();
    }

    private function resolveApprovedValidityState(FindingException $exception, ?CarbonImmutable $now = null): string
    {
        $now ??= CarbonImmutable::instance(now());

        $expiresAt = $this->renewalAwareDate(
            $exception,
            'previous_expires_at',
            $exception->expires_at,
        );

        if ($expiresAt instanceof CarbonImmutable && $expiresAt->lessThanOrEqualTo($now)) {
            return FindingException::VALIDITY_EXPIRED;
        }

        if ($this->isExpiring($exception, $now, renewalAware: true)) {
            return FindingException::VALIDITY_EXPIRING;
        }

        return FindingException::VALIDITY_VALID;
    }

    private function isExpiring(FindingException $exception, CarbonImmutable $now, bool $renewalAware = false): bool
    {
        $reviewDueAt = $renewalAware
            ? $this->renewalAwareDate($exception, 'previous_review_due_at', $exception->review_due_at)
            : ($exception->review_due_at instanceof Carbon ? CarbonImmutable::instance($exception->review_due_at) : null);

        if ($reviewDueAt instanceof CarbonImmutable && $reviewDueAt->lessThanOrEqualTo($now)) {
            return true;
        }

        $expiresAt = $renewalAware
            ? $this->renewalAwareDate($exception, 'previous_expires_at', $exception->expires_at)
            : ($exception->expires_at instanceof Carbon ? CarbonImmutable::instance($exception->expires_at) : null);

        if (! $expiresAt instanceof CarbonImmutable) {
            return false;
        }

        return $expiresAt->lessThanOrEqualTo($now->addDays(7));
    }

    private function renewalAwareDate(FindingException $exception, string $metadataKey, mixed $fallback): ?CarbonImmutable
    {
        $currentDecision = $exception->relationLoaded('currentDecision')
            ? $exception->currentDecision
            : $exception->currentDecision()->first();

        if ($currentDecision instanceof FindingExceptionDecision && is_string($currentDecision->metadata[$metadataKey] ?? null)) {
            return CarbonImmutable::parse((string) $currentDecision->metadata[$metadataKey]);
        }

        return $fallback instanceof Carbon
            ? CarbonImmutable::instance($fallback)
            : null;
    }
}