local util = require("util")

local function save_file_write(filename, data)
    os.rename(filename, filename..".bak")
    local f = io.open(filename, "w")
    if not f then
        return false
    end
    f:write(util.json_enc(data))
    f:close()
    print("[save_file] saved to " .. filename)
    return true
end

local function save_file_read(filename)
    local data
    local f = io.open(filename, "r")
    if f then
        data = util.json_dec(f:read("*all"))
        f:close()
        if not data then
            return nil, "save_corrupted"
        end
        print("[save_file] loaded " .. filename)
    else
        data = {}
    end
    if not save_file_write(filename, data) then
        return nil, "save_failed_write"
    end
    return data
end

return {
    write = save_file_write,
    read = save_file_read,
}