<?php
namespace App\Services;

/**
 * Class FhirService
 * HL7 FHIR R4 Interoperability Engine (Patient, Encounter, Observation, Procedure)
 *
 * @package App\Services
 */
class FhirService
{
    private string $serverUrl;
    private string $facilityId;

    public function __construct()
    {
        $config = require __DIR__ . '/../../config/integration.php';
        $fhir = $config['fhir'];
        $this->serverUrl = rtrim($fhir['server_url'], '/');
        $this->facilityId = $fhir['facility_id'] ?? 'THAI_MED_CENTER';
    }

    /**
     * Build FHIR R4 Patient Resource
     */
    public function buildPatientResource(array $patient): array
    {
        return [
            'resourceType' => 'Patient',
            'id' => (string)$patient['id'],
            'identifier' => [
                [
                    'use' => 'official',
                    'system' => 'https://www.dopa.go.th/cid',
                    'value' => $patient['cid'],
                ],
                [
                    'use' => 'usual',
                    'system' => "https://his.hospital.local/hn/{$this->facilityId}",
                    'value' => $patient['hn'],
                ]
            ],
            'active' => true,
            'name' => [
                [
                    'use' => 'official',
                    'text' => trim(($patient['first_name_th'] ?? '') . ' ' . ($patient['last_name_th'] ?? '')),
                    'family' => $patient['last_name_th'] ?? '',
                    'given' => [$patient['first_name_th'] ?? ''],
                ]
            ],
            'gender' => strtolower($patient['gender'] ?? 'unknown'),
            'birthDate' => $patient['birth_date'] ?? null,
            'telecom' => [
                [
                    'system' => 'phone',
                    'value' => $patient['phone'] ?? '',
                    'use' => 'mobile',
                ]
            ],
        ];
    }

    /**
     * Build FHIR R4 Observation Resource for Pain Score (VAS 0-10)
     */
    public function buildPainScoreObservation(int $patientId, int $encounterId, int $painScore, string $type = 'Pre-treatment'): array
    {
        return [
            'resourceType' => 'Observation',
            'status' => 'final',
            'category' => [
                [
                    'coding' => [
                        [
                            'system' => 'http://terminology.hl7.org/CodeSystem/observation-category',
                            'code' => 'exam',
                            'display' => 'Exam',
                        ]
                    ]
                ]
            ],
            'code' => [
                'coding' => [
                    [
                        'system' => 'http://loinc.org',
                        'code' => '72514-3',
                        'display' => 'Pain severity - 0-10 verbal numeric rating [Score] - Reported',
                    ]
                ],
                'text' => "VAS Pain Score ({$type})",
            ],
            'subject' => [
                'reference' => "Patient/{$patientId}",
            ],
            'encounter' => [
                'reference' => "Encounter/{$encounterId}",
            ],
            'effectiveDateTime' => date('c'),
            'valueInteger' => $painScore,
        ];
    }

    /**
     * Export complete bundle to FHIR Server
     */
    public function exportEncounterBundle(array $queue, array $soapNote): array
    {
        $patientRes = $this->buildPatientResource(['id' => $queue['patient_id'], 'cid' => $queue['cid'] ?? '', 'hn' => $queue['hn'] ?? '', 'first_name_th' => $queue['patient_name'] ?? '']);
        
        $bundle = [
            'resourceType' => 'Bundle',
            'type' => 'transaction',
            'entry' => [
                [
                    'resource' => $patientRes,
                    'request' => ['method' => 'PUT', 'url' => "Patient/{$queue['patient_id']}"],
                ]
            ],
        ];

        if (isset($soapNote['pre_pain_score'])) {
            $obsPre = $this->buildPainScoreObservation((int)$queue['patient_id'], (int)$queue['id'], (int)$soapNote['pre_pain_score'], 'Pre-treatment');
            $bundle['entry'][] = [
                'resource' => $obsPre,
                'request' => ['method' => 'POST', 'url' => "Observation"],
            ];
        }

        if (isset($soapNote['post_pain_score'])) {
            $obsPost = $this->buildPainScoreObservation((int)$queue['patient_id'], (int)$queue['id'], (int)$soapNote['post_pain_score'], 'Post-treatment');
            $bundle['entry'][] = [
                'resource' => $obsPost,
                'request' => ['method' => 'POST', 'url' => "Observation"],
            ];
        }

        return $bundle;
    }
}