jsondb.lua

local fs = require 'fs'
local json = require 'json'

local Database = {}
Database.__index = Database

function Database.load(path)
    local self = setmetatable({}, Database)

    self.path = path
    self.dirty = false

    if fs.existsSync(path) then
        local data = assert(fs.readFileSync(path))

        if data == '' then
            self.data = {}
        else
            self.data = json.parse(data)

            assert(type(self.data) == 'table', 'invalid data schema')
        end
    else
        self.data = {}
    end
end

function Database:save()
    if not self.dirty then
        return
    end

    local tmpname = self.path .. '.tmp'

    local data = json.stringify(self.data)
    assert(fs.writeFileSync(tmpname, data))
    assert(fs.renameSync(tmpname, self.path))
end

function Database:get(key)
    return self.data[key]
end

function Database:set(key, value)
    self.data[key] = value
    self.dirty = true
end

--[[ Example:

local db = Database.load('/path/to/db.json')

db:set('foo', 'bar')
db:get('foo') --> 'bar'

db:save()

--- db.json
{"foo":"bar"}

]]