import { readFile, writeFile, access, constants } from 'fs/promises'

export function createDatabase(path, initialValue) {
    return { path, initialValue }
}

async function withDatabase({ path, initialValue }, fn) {
    try {
        await access(path, constants.R_OK)
    } catch (e) {
        console.log(`Creating empty database into "${path}"`)
        await writeFile(path, JSON.stringify(initialValue, null, 2))
    }

    console.log(`Loading database from "${path}"`)
    const state = JSON.parse(await readFile(path, 'utf-8'))

    const result = await fn(state)

    console.log(`Saving database to "${path}"`)
    await writeFile(path, JSON.stringify(state, null, 2))

    return result
}

function createTable(tableName) {
    return {
        create() {},
        get() {},
        update() {},
        delete() {},
    }
}

export const User = createTable('users')
export const Problem = createTable('problems')

export const getUser = (db, id) =>
    withDatabase(db, state => {
        return state.users[id]
    })

export const createUser = (db, { email, username, password }) =>
    withDatabase(db, state => {
        state.users[email] = {
            username,
            password,
        }
    })

export const updateUser = (db, username, { email, password }) =>
    withDatabase(db, state => {
        state.users[username] = {
            email,
            password,
        }
    })