Build a new-member onboarding board

// Hosted Widget server. This app uses only its own database, never the contact API.
const BOARD_KEY = ['member-onboarding', 'board-v1'] as const;
const MAX_CHECKLISTS = 100;
const TASKS = [
    { id: 'details', title: 'Review contact details', detail: 'Check the accepted member’s details in campai.' },
    { id: 'welcome', title: 'Send the welcome information', detail: 'Use your club’s usual communication process.' },
    { id: 'group', title: 'Arrange the right group', detail: 'Confirm the department, team, or introductory session.' },
    { id: 'app', title: 'Offer the Community App invitation', detail: 'Share the invitation through the member’s campai record.' },
    { id: 'meeting', title: 'Confirm the first visit', detail: 'Agree a date and explain who will welcome the member.' },
] as const;
type Checklist = { number: string; name: string; owner: string; due: string; done: string[]; createdAt: string; updatedAt: string };
type Board = { schema: 1; members: Checklist[] };

function text(value: unknown, label: string, max: number) {
    if (typeof value !== 'string' || !value.trim() || value.trim().length > max) throw new Error(`${label} is required (maximum ${max} characters).`);
    return value.trim();
}
function dateOnly(value: unknown) {
    const date = text(value, 'Due date', 10);
    if (!/^\d{4}-\d{2}-\d{2}$/.test(date) || !Number.isFinite(Date.parse(`${date}T00:00:00Z`)) || new Date(`${date}T00:00:00Z`).toISOString().slice(0, 10) !== date) throw new Error('Enter a real due date as YYYY-MM-DD.');
    return date;
}
function parseBoard(value: unknown): Board {
    if (!value || typeof value !== 'object') throw new Error('Unexpected board data. Do not overwrite it; review the saved schema.');
    const board = value as Board;
    if (board.schema !== 1 || !Array.isArray(board.members) || board.members.length > MAX_CHECKLISTS) throw new Error('Unexpected board schema or size.');
    const numbers = new Set<string>();
    for (const member of board.members) {
        if (!member || typeof member !== 'object') throw new Error('Unexpected checklist data.');
        const number = text(member.number, 'Member number', 60);
        text(member.name, 'Member name', 100); text(member.owner, 'Owner', 100); dateOnly(member.due);
        if (numbers.has(number) || !Array.isArray(member.done) || new Set(member.done).size !== member.done.length || member.done.some(id => !TASKS.some(task => task.id === id))) throw new Error('Unexpected duplicate member or task data.');
        if (![member.createdAt, member.updatedAt].every(date => typeof date === 'string' && Number.isFinite(Date.parse(date)))) throw new Error('Unexpected checklist timestamp.');
        numbers.add(number);
    }
    return board;
}
async function read() {
    const entry = await storage.get<unknown>(BOARD_KEY);
    return { version: entry.versionstamp, board: entry.versionstamp === null ? { schema: 1 as const, members: [] } : parseBoard(entry.value) };
}
export async function loadBoard() {
    const current = await read();
    return { ...current, tasks: TASKS, limit: MAX_CHECKLISTS };
}
export async function changeBoard(input: unknown) {
    if (!input || typeof input !== 'object' || Array.isArray(input)) throw new Error('Invalid checklist request.');
    const request = input as Record<string, unknown>;
    if (request.version !== null && (typeof request.version !== 'string' || request.version.length > 100)) throw new Error('Reload the board before saving.');
    const current = await read();
    if (request.version !== current.version) throw new Error('Someone changed the board. Reload and review before saving again.');
    const number = text(request.number, 'Member number', 60);
    const members = current.board.members.map(member => ({ ...member, done: [...member.done] }));
    const index = members.findIndex(member => member.number === number);
    const now = new Date().toISOString();
    if (request.operation === 'add') {
        if (index !== -1) throw new Error('This member number already has a checklist. Open the existing one.');
        if (members.length >= MAX_CHECKLISTS) throw new Error('This board is full. Remove finished checklists before adding another.');
        members.push({ number, name: text(request.name, 'Member name', 100), owner: text(request.owner, 'Owner', 100), due: dateOnly(request.due), done: [], createdAt: now, updatedAt: now });
    } else {
        if (index === -1) throw new Error('This checklist no longer exists. Reload the board.');
        if (request.operation === 'task') {
            if (typeof request.done !== 'boolean' || !TASKS.some(task => task.id === request.task)) throw new Error('Unknown task or state.');
            const taskId = request.task as string;
            members[index].done = members[index].done.filter(id => id !== taskId);
            if (request.done) members[index].done.push(taskId);
            members[index].updatedAt = now;
        } else if (request.operation === 'assign') {
            members[index].owner = text(request.owner, 'Owner', 100);
            members[index].due = dateOnly(request.due);
            members[index].updatedAt = now;
        } else if (request.operation === 'remove') {
            if (request.confirmNumber !== number) throw new Error('Type the member number to remove this checklist.');
            members.splice(index, 1);
        } else throw new Error('Unknown checklist operation.');
    }
    // A single conditional commit protects the complete board from concurrent lost updates.
    let committed: { ok: boolean; versionstamp?: string };
    try {
        committed = await storage.atomic().check({ key: BOARD_KEY, versionstamp: current.version }).set(BOARD_KEY, { schema: 1, members }).commit();
    } catch {
        throw new Error('Save was not confirmed. Reload the board and inspect it before trying again.');
    }
    if (!committed.ok) throw new Error('Someone changed the board while you saved. Reload and review the latest checklist.');
    // Reload also catches changes made by another administrator immediately after our commit.
    try { return await loadBoard(); }
    catch { throw new Error('The save committed, but the board could not be reloaded. Reload before making another change.'); }
}