Preferences module

local json = require "json"

local function decodeFile(path)
    local file = io.open(path)
    if file then
        local body = file:read('a*')
        file:close()
        return json.decode(body)
    end
end

local function encodeFile(path, object)
    local file = io.open(path, 'w')
    if file then
        file:write(json.encode(object))
        file:close()
    end
end

local defaults = {
    name = 'Settings';
    Sound = {
        Volume = 1
    },
    Music = {
        Volume = 1
    },
    Guides = {
        Show = true
    }
}

local storagePath = system.pathForFile("Scrapyard.preferences", system.DocumentsDirectory)
local valid, preferences = pcall(decodeFile, storagePath)
if not valid then preferences = {} end

setmetatable(preferences, {__index = defaults})
Runtime:dispatchEvent(preferences)

Runtime:addEventListener('Settings',
    function(event)
        for name, value in pairs(event) do
            if name ~= 'name' then
                preferences[name] = value
            end
        end
        encodeFile(storagePath, preferences)
    end
)

return preferences