<?php

namespace App\Services\Care;

use App\Models\Assessment;
use App\Models\AssessmentQuestion;
use Illuminate\Support\Str;

/**
 * Export a Care assessment as FHIR R4 Questionnaire + QuestionnaireResponse (JSON).
 * Not a full FHIR server — interchange export for completed/draft assessments.
 */
class FhirAssessmentExporter
{
    public const FHIR_VERSION = '4.0.1';

    /**
     * Bundle containing Questionnaire and QuestionnaireResponse.
     *
     * @return array<string, mixed>
     */
    public function exportBundle(Assessment $assessment): array
    {
        $assessment->loadMissing(['template.questions', 'answers.question', 'patient', 'score']);

        $questionnaire = $this->questionnaire($assessment);
        $response = $this->questionnaireResponse($assessment, $questionnaire['url']);

        return [
            'resourceType' => 'Bundle',
            'type' => 'collection',
            'timestamp' => now()->toIso8601String(),
            'meta' => [
                'tag' => [[
                    'system' => 'https://care.ladill.com/fhir/tags',
                    'code' => 'ladill-care-assessment-export',
                ]],
            ],
            'entry' => [
                ['fullUrl' => $questionnaire['url'], 'resource' => $questionnaire],
                ['fullUrl' => $response['id'] ? 'urn:uuid:'.$response['id'] : 'QuestionnaireResponse/'.$assessment->uuid, 'resource' => $response],
            ],
        ];
    }

    /**
     * @return array<string, mixed>
     */
    public function questionnaire(Assessment $assessment): array
    {
        $template = $assessment->template;
        $url = 'https://care.ladill.com/fhir/Questionnaire/'.($template?->code ?? 'unknown').'/v'.($template?->version ?? 1);

        $items = [];
        foreach ($template?->questions ?? [] as $question) {
            $items[] = $this->questionItem($question);
        }

        return [
            'resourceType' => 'Questionnaire',
            'id' => ($template?->code ?? 'unknown').'-v'.($template?->version ?? 1),
            'url' => $url,
            'version' => (string) ($template?->version ?? 1),
            'name' => Str::studly($template?->code ?? 'Assessment'),
            'title' => $template?->name ?? 'Assessment',
            'status' => ($template?->is_active ?? true) ? 'active' : 'retired',
            'description' => $template?->description,
            'item' => $items,
        ];
    }

    /**
     * @return array<string, mixed>
     */
    public function questionnaireResponse(Assessment $assessment, ?string $questionnaireUrl = null): array
    {
        $assessment->loadMissing(['template.questions', 'answers.question', 'patient', 'score']);
        $questionnaireUrl ??= $this->questionnaire($assessment)['url'];

        $answersByQ = $assessment->answers->keyBy('question_id');
        $items = [];
        foreach ($assessment->template?->questions ?? [] as $question) {
            $answer = $answersByQ->get($question->id);
            if (! $answer) {
                continue;
            }
            $value = $answer->authoritativeValue($question->answer_type);
            if ($value === null || $value === '') {
                continue;
            }
            $items[] = [
                'linkId' => $question->code,
                'text' => $question->label,
                'answer' => $this->fhirAnswers($question, $value),
            ];
        }

        $status = match ($assessment->status) {
            Assessment::STATUS_COMPLETED => 'completed',
            Assessment::STATUS_CANCELLED => 'entered-in-error',
            default => 'in-progress',
        };

        $resource = [
            'resourceType' => 'QuestionnaireResponse',
            'id' => $assessment->uuid,
            'questionnaire' => $questionnaireUrl,
            'status' => $status,
            'authored' => ($assessment->assessed_at ?? $assessment->completed_at ?? $assessment->created_at)?->toIso8601String(),
            'subject' => [
                'reference' => 'Patient/'.($assessment->patient?->uuid ?? $assessment->patient_id),
                'display' => $assessment->patient?->fullName(),
            ],
            'item' => $items,
        ];

        if ($assessment->score) {
            $resource['extension'] = [[
                'url' => 'https://care.ladill.com/fhir/StructureDefinition/assessment-score',
                'extension' => array_values(array_filter([
                    ['url' => 'total', 'valueDecimal' => (float) $assessment->score->total_score],
                    $assessment->score->max_score !== null
                        ? ['url' => 'max', 'valueDecimal' => (float) $assessment->score->max_score]
                        : null,
                    $assessment->score->severity_label
                        ? ['url' => 'severity', 'valueString' => $assessment->score->severity_label]
                        : null,
                    ['url' => 'templateCode', 'valueString' => $assessment->score->template_code],
                ])),
            ]];
        }

        return $resource;
    }

    /**
     * @return array<string, mixed>
     */
    protected function questionItem(AssessmentQuestion $question): array
    {
        $type = match ($question->answer_type) {
            AssessmentQuestion::TYPE_BOOLEAN => 'boolean',
            AssessmentQuestion::TYPE_INTEGER => 'integer',
            AssessmentQuestion::TYPE_NUMBER,
            AssessmentQuestion::TYPE_SCALE,
            AssessmentQuestion::TYPE_SCORE_ITEM,
            AssessmentQuestion::TYPE_CALCULATED => 'decimal',
            AssessmentQuestion::TYPE_DATE => 'date',
            AssessmentQuestion::TYPE_DATETIME => 'dateTime',
            AssessmentQuestion::TYPE_MULTI_CHOICE => 'choice',
            AssessmentQuestion::TYPE_SINGLE_CHOICE => 'choice',
            default => 'string',
        };

        $item = [
            'linkId' => $question->code,
            'text' => $question->label,
            'type' => $type,
            'required' => (bool) $question->is_required,
        ];

        if ($question->help_text) {
            $item['prefix'] = $question->help_text;
        }

        $choices = $question->options['choices'] ?? null;
        if (is_array($choices) && $choices !== []) {
            $item['answerOption'] = array_map(function ($c) {
                $code = (string) ($c['code'] ?? '');
                $label = (string) ($c['label'] ?? $code);

                return [
                    'valueCoding' => [
                        'code' => $code,
                        'display' => $label,
                    ],
                ];
            }, $choices);
        }

        return $item;
    }

    /**
     * @return list<array<string, mixed>>
     */
    protected function fhirAnswers(AssessmentQuestion $question, mixed $value): array
    {
        return match ($question->answer_type) {
            AssessmentQuestion::TYPE_BOOLEAN => [['valueBoolean' => (bool) $value]],
            AssessmentQuestion::TYPE_INTEGER => [['valueInteger' => (int) $value]],
            AssessmentQuestion::TYPE_NUMBER,
            AssessmentQuestion::TYPE_SCALE,
            AssessmentQuestion::TYPE_SCORE_ITEM,
            AssessmentQuestion::TYPE_CALCULATED => [['valueDecimal' => (float) $value]],
            AssessmentQuestion::TYPE_DATE => [['valueDate' => $value instanceof \Carbon\Carbon
                ? $value->toDateString()
                : (string) $value]],
            AssessmentQuestion::TYPE_DATETIME => [['valueDateTime' => $value instanceof \Carbon\Carbon
                ? $value->toIso8601String()
                : (string) $value]],
            AssessmentQuestion::TYPE_MULTI_CHOICE => collect(is_array($value) ? $value : [$value])
                ->map(fn ($v) => ['valueString' => (string) $v])
                ->values()
                ->all(),
            AssessmentQuestion::TYPE_SINGLE_CHOICE => [['valueString' => (string) $value]],
            default => [['valueString' => is_scalar($value) ? (string) $value : json_encode($value)]],
        };
    }
}