<?php
/**
 * Branching walk for questionnaire exports/results (matches app all-in-one logic).
 * Only questions on the active path from current answers are "reachable".
 */

function qrb_load_path_questions(PDO $pdo, string $questionnaireId): array {
    $stmt = $pdo->prepare("
        SELECT questionID, defaultText, type, orderIndex, configJson
        FROM question
        WHERE questionnaireID = :qn
        ORDER BY orderIndex
    ");
    $stmt->execute([':qn' => $questionnaireId]);
    $path = [];

    foreach ($stmt->fetchAll(PDO::FETCH_ASSOC) as $row) {
        $parts = explode('__', $row['questionID']);
        $shortId = end($parts);
        $config = json_decode($row['configJson'] ?? '{}', true) ?: [];

        $options = [];
        $ao = $pdo->prepare("
            SELECT defaultText, nextQuestionId
            FROM answer_option
            WHERE questionID = :qid
            ORDER BY orderIndex
        ");
        $ao->execute([':qid' => $row['questionID']]);
        foreach ($ao->fetchAll(PDO::FETCH_ASSOC) as $opt) {
            $options[] = [
                'text'           => $opt['defaultText'],
                'nextQuestionId' => $opt['nextQuestionId'] ?? '',
            ];
        }

        $symptoms = [];
        if (!empty($config['symptoms']) && is_array($config['symptoms'])) {
            $symptoms = $config['symptoms'];
        }

        $path[] = [
            'questionID' => $row['questionID'],
            'shortId'    => $shortId,
            'type'       => $row['type'] ?? '',
            'storageKey' => $row['defaultText'] !== '' ? $row['defaultText'] : $shortId,
            'options'    => $options,
            'symptoms'   => $symptoms,
            'isLastPage' => ($row['type'] ?? '') === 'last_page',
        ];
    }

    return $path;
}

/**
 * @param array<string, array> $answerMap keyed by full questionID
 * @return array<string, bool> reachable full questionIDs
 */
function qrb_reachable_question_ids(PDO $pdo, string $questionnaireId, array $answerMap, array $optionTextMap): array {
    $path = qrb_load_path_questions($pdo, $questionnaireId);
    $reachable = [];
    $shortToIndex = [];
    foreach ($path as $idx => $q) {
        $shortToIndex[$q['shortId']] = $idx;
    }

    $i = 0;
    $count = count($path);
    while ($i < $count) {
        $q = $path[$i];
        if ($q['isLastPage']) {
            $i++;
            continue;
        }

        $reachable[$q['questionID']] = true;

        $nextTarget = qrb_resolve_next_target($q, $answerMap, $optionTextMap);
        if ($nextTarget !== null) {
            foreach ($path as $pq) {
                if ($pq['isLastPage'] && $pq['shortId'] === $nextTarget) {
                    break 2;
                }
            }
            if (isset($shortToIndex[$nextTarget])) {
                $i = $shortToIndex[$nextTarget];
            } else {
                $i++;
            }
        } elseif (qrb_has_branching_options($q) && !qrb_has_branch_answer($q, $answerMap, $optionTextMap)) {
            break;
        } else {
            $i++;
        }
    }

    return $reachable;
}

function qrb_resolve_next_target(array $q, array $answerMap, array $optionTextMap): ?string {
    $answer = $answerMap[$q['questionID']] ?? null;
    if ($answer === null) {
        return null;
    }

    $selectedText = qrb_answer_display_value($answer, $optionTextMap);
    if ($selectedText === null || $selectedText === '') {
        return null;
    }

    foreach ($q['options'] as $opt) {
        if ($opt['text'] === $selectedText && $opt['nextQuestionId'] !== '') {
            return $opt['nextQuestionId'];
        }
    }

    return null;
}

function qrb_has_branching_options(array $q): bool {
    foreach ($q['options'] as $opt) {
        if ($opt['nextQuestionId'] !== '') {
            return true;
        }
    }
    return false;
}

function qrb_has_branch_answer(array $q, array $answerMap, array $optionTextMap): bool {
    $answer = $answerMap[$q['questionID']] ?? null;
    if ($answer === null) {
        return false;
    }
    $v = qrb_answer_display_value($answer, $optionTextMap);
    return $v !== null && $v !== '';
}

function qrb_answer_display_value(array $answer, array $optionTextMap): ?string {
    if (!empty($answer['answerOptionID']) && isset($optionTextMap[$answer['answerOptionID']])) {
        return $optionTextMap[$answer['answerOptionID']];
    }
    if (isset($answer['freeTextValue']) && $answer['freeTextValue'] !== '') {
        return (string)$answer['freeTextValue'];
    }
    if (isset($answer['numericValue']) && $answer['numericValue'] !== null && $answer['numericValue'] !== '') {
        return (string)$answer['numericValue'];
    }
    return null;
}

function qrb_format_cell(array $answer, array $optionTextMap): string {
    $v = qrb_answer_display_value($answer, $optionTextMap);
    return $v ?? '';
}