import { v4 as uuidv4 } from 'uuid';

// Answer-option coding for questionnaire choice / open-choice questions.
//
// Rudy's original model (a6deac4c, 2025-04-24) is LOINC-first: a choice question is imported from the
// LOINC library and LoincSearch.tsx (convertLoincQToItem) populates answerOption.value.{code,system,
// display} directly -- which is WHY those fields are read-only in the builder. That model is correct
// and stays.
//
// What it never supported is a MANUALLY authored dropdown ("Billing question" / "New patient"), which
// has no code system at all -- while QuestionnaireService serializes choice options as valueCoding and
// DROPS any option lacking a code (QuestionnaireService.tsx:526). So a manual option needs a code, and
// this module derives one under a local Akashic CodeSystem.
//
// A local CodeSystem for an org-specific answer list is legitimate, portable FHIR -- a receiving system
// sees a coded answer with an unambiguous system URI. It is NOT a SNOMED/LOINC-binding violation: that
// convention governs *clinical* concepts, and "Billing question" has no SNOMED equivalent.
//
// See docs/_CLAUDE/2026-07-16-questionnaire-choice-answer-options-design.md.

export const AKASHIC_ANSWER_CODE_SYSTEM =
    'https://akashichealthrecords.com/fhir/CodeSystem/questionnaire-answer';

export const LOINC_SYSTEM = 'http://loinc.org';

/**
 * LOINC owns its answer lists. An imported option's label/code/system stay read-only in the builder so
 * a hand edit cannot corrupt standards-bound data.
 */
export const isLoincOwnedOption = (system?: string | null): boolean => system === LOINC_SYSTEM;

/** lowercase; runs of non-alphanumerics collapse to a single '-'; leading/trailing '-' trimmed. */
export const slugifyAnswerCode = (value: string): string =>
    (value ?? '')
        .toLowerCase()
        .replace(/[^a-z0-9]+/g, '-')
        .replace(/^-+|-+$/g, '');

/**
 * Derive a STABLE code for a manually authored option.
 *
 * Stability is the entire point. The caller MUST only invoke this when the option's code is empty, so
 * relabelling can never change an existing code -- a changed code orphans every QuestionnaireResponse
 * that referenced the old one. See the design doc's Risks table.
 *
 * `takenCodes` are the codes already used by the OTHER options in the SAME question, so two options
 * labelled alike get `billing-question` and `billing-question-2` rather than a duplicate.
 *
 * A label that slugs to nothing (all punctuation/emoji) falls back to a uuid: opaque, but stable and
 * unique, which is what matters.
 */
export const deriveAnswerOptionCode = (display: string, takenCodes: string[]): string => {
    const base = slugifyAnswerCode(display);

    if (base === '') {
        return uuidv4();
    }

    if (!takenCodes.includes(base)) {
        return base;
    }

    let suffix = 2;

    while (takenCodes.includes(`${base}-${suffix}`)) {
        suffix += 1;
    }

    return `${base}-${suffix}`;
};