import { Questionnaire, QuestionnaireItem } from 'fhir/r4';
import { COLUMN_GRID, COLUMN_SPAN_EXTENSION_URL, normalizeColumnSpan } from './questionnaireLayout';
import { EMAIL_ADDRESS_REGEX, REGEX_EXTENSION_URL } from './questionnaireEmailField';

// Sanitized, author-side snapshot of a Questionnaire's structure sent to the AWS
// `public-form/register` endpoint. Only the fields an anonymous public form renderer needs to
// display + validate the form survive here - server-authoring fields (code, initial, prefix,
// readOnly, repeats, etc.) are intentionally dropped.
//
// Extensions are dropped as a rule, with TWO deliberate exceptions, each decoded into a flat field: the
// column-span layout hint into `columnSpan`, because the public form must render the layout the author
// built, and the email rule into `inputKind`, because the visitor's entry must be checked as an address. See docs/_CLAUDE/2026-07-16-questionnaire-grid-columns-design.md.
export interface PublicFormItem {
    linkId: string;
    text?: string;
    type: string;
    required?: boolean;
    columnSpan?: number;
    inputKind?: 'email';
    answerOption?: any[];
    enableWhen?: any[];
    item?: PublicFormItem[];
}

// Mirrors the `_help` synthetic-child filter used elsewhere (see
// QuestionnaireService.tsx's `transformFromFhirQuestionnaireItem`): help-text display items are
// synthesized server/client-side as a child with linkId `${parent.linkId}_help` and are not
// real authored questions, so they're excluded from the public snapshot.
const isHelpChild = (parentLinkId: string, childLinkId: string): boolean =>
    childLinkId === `${parentLinkId}_help`;

const buildPublicFormItem = (item: QuestionnaireItem): PublicFormItem => {
    const children = (item.item ?? []).filter((childItem) => !isHelpChild(item.linkId, childItem.linkId));
    const columnSpan = normalizeColumnSpan(
        item.extension?.find((extension) => extension.url === COLUMN_SPAN_EXTENSION_URL)?.valueInteger
    );

    const isEmail = item.type === 'string'
        && item.extension?.some((extension) => extension.url === REGEX_EXTENSION_URL && extension.valueString === EMAIL_ADDRESS_REGEX);

    return {
        linkId: item.linkId,
        ...(item.text !== undefined && { text: item.text }),
        type: item.type,
        ...(item.required !== undefined && { required: item.required }),
        // Full width is the renderer's default, so only a non-default span is worth the bytes.
        ...(columnSpan !== COLUMN_GRID && { columnSpan }),
        ...(isEmail && { inputKind: 'email' as const }),
        ...(item.answerOption && item.answerOption.length !== 0 && { answerOption: item.answerOption }),
        ...(item.enableWhen && item.enableWhen.length !== 0 && { enableWhen: item.enableWhen }),
        ...(children.length !== 0 && { item: children.map(buildPublicFormItem) })
    };
};

export function buildPublicFormSnapshot(questionnaire: Questionnaire): { title: string; description?: string; items: PublicFormItem[] } {
    const description = questionnaire.description?.trim();
    return {
        title: questionnaire.title ?? '',
        ...(description && { description }),
        items: (questionnaire.item ?? []).map(buildPublicFormItem)
    };
}