const STABLE_KEY_RE = /^[a-zA-Z][a-zA-Z0-9_]*$/;

/** Local question id from full questionID (hash__q5 → q5). */
export function questionLocalKey(questionID, fallback = '') {
    const id = String(questionID ?? '');
    const sep = id.lastIndexOf('__');
    if (sep >= 0) return id.slice(sep + 2);
    return fallback || id;
}

function parseQuestionConfig(q) {
    if (!q || typeof q !== 'object') return {};
    let cfg = q.configJson;
    if (typeof cfg === 'string') {
        try {
            cfg = JSON.parse(cfg);
        } catch {
            cfg = {};
        }
    }
    return cfg && typeof cfg === 'object' ? cfg : {};
}

/** Stable question key for table headers / CSV (matches server qdb_question_column_label). */
export function questionDisplayKey(q) {
    if (!q) return '';
    if (q.questionKey) return String(q.questionKey);
    const cfg = parseQuestionConfig(q);
    const fromCfg = String(cfg.questionKey || '').trim();
    if (fromCfg && STABLE_KEY_RE.test(fromCfg)) return fromCfg;
    const dt = String(q.defaultText || '').trim();
    if (dt && STABLE_KEY_RE.test(dt)) return dt;
    return questionLocalKey(q.questionID, dt);
}

/** German question text for header tooltips. */
export function questionGermanLabel(q) {
    const dt = String(q?.defaultText || '').trim();
    const key = questionDisplayKey(q);
    if (dt && dt !== key) return dt;
    return '';
}

/** One symptom value from parent glass-scale JSON answer. */
export function glassSymptomAnswerValue(raw, symptomKey) {
    if (!raw || !symptomKey) return '';
    try {
        const o = JSON.parse(raw);
        if (o && typeof o === 'object' && !Array.isArray(o)) {
            const v = o[symptomKey];
            return v != null ? String(v).trim() : '';
        }
    } catch {
        /* ignore */
    }
    return '';
}

/**
 * Flat result/export columns: glass_scale questions → one column per symptom.
 */
export function buildResultColumns(questions) {
    const cols = [];
    for (const q of questions || []) {
        if (q.type === 'last_page') continue;
        const cfg = parseQuestionConfig(q);
        const symptoms = cfg.symptoms;
        if (q.type === 'glass_scale_question' && Array.isArray(symptoms) && symptoms.length > 0) {
            const parentKey = questionDisplayKey(q);
            for (const sk of symptoms) {
                const symptomKey = String(sk).trim();
                if (!symptomKey) continue;
                cols.push({
                    key: `glass_${q.questionID}_${symptomKey}`,
                    questionID: q.questionID,
                    symptomKey,
                    label: symptomKey,
                    title: parentKey && parentKey !== symptomKey
                        ? `${parentKey} · ${symptomKey}`
                        : symptomKey,
                    isGlassSymptom: true,
                    question: q,
                });
            }
            continue;
        }
        const label = questionDisplayKey(q);
        cols.push({
            key: `q_${q.questionID}`,
            questionID: q.questionID,
            symptomKey: null,
            label,
            title: questionGermanLabel(q) || label,
            isGlassSymptom: false,
            question: q,
        });
    }
    return cols;
}

/** Display text for one results table cell. */
export function resultColumnCellValue(col, answer, optionMap = {}) {
    if (!answer) return null;
    if (col.isGlassSymptom) {
        const v = glassSymptomAnswerValue(answer.freeTextValue, col.symptomKey);
        return v || null;
    }
    const q = col.question;
    if (answer.answerOptionID && optionMap[answer.answerOptionID]) {
        return optionMap[answer.answerOptionID];
    }
    if (answer.freeTextValue) return answer.freeTextValue;
    if (answer.numericValue !== null && answer.numericValue !== undefined) {
        return answer.numericValue;
    }
    return null;
}

/** header_order.json column id → question key (questionnaire_x-y → y). */
export function headerColumnQuestionKey(headerId) {
    const id = String(headerId ?? '');
    if (id === 'client_code') return 'client_code';
    const dash = id.indexOf('-');
    if (dash < 0) return id;
    return id.slice(dash + 1);
}