fileutil.lua

local base64 = require('packages.base64')

FileUtil = {}

local path_to_this_file = debug.getinfo(1).source
local base_directory = path_to_this_file:match("^@(.*)fileutil%.lua$")
local webcache_directory = base_directory..'webcache/'

local base64encoder = base64.makeencoder('+','-','_')

local function get_directory(file_path)
    local _, _, directory = file_path:find("^(.*/)[^/]*$")
    return directory or ''
end

function FileUtil.read_local_file(path, current_file_path)
    if path == '' then
        error("Path must be nonempty")
    end

    local directory = ""
    if current_file_path and path:sub(1,1) ~= '/' then
        directory = get_directory(current_file_path)
    end

    local f = io.open(directory..path)
    if f then
        return f:read('*a')
    else
        error('Could not open file "'..directory..path..'"')
    end
end

local function write_into_webcache(url, text)
    local filename = webcache_directory..base64.encode(url, base64encoder)
    local file = io.open(filename, 'w')
    if not file then
        error('Could not open "'..filename..'"')
    end

    file:write(text)
    file:close()
end

local function read_from_webcache(url)
    local filename = webcache_directory..base64.encode(url, base64encoder)
    local file = io.open(filename, 'r')
    if not file then
        return nil
    end

    local text = file:read('a')
    file:close()
    return text
end

local function process_url(url)
    local documentId = url:match('^https://docs%.google%.com/document/d/([%w%-_]+)')
    if documentId then
        return 'https://docs.google.com/document/d/'..documentId..'/export?format=txt'
    end

    return url
end

function FileUtil.read_web_file(url)
    if not http then
        error('Internet files only work from ComputerCraft, and with the http variable non-nil')
    end

    if url == '' then
        error('URL cannot be empty')
    end

    url = process_url(url)

    local result = http.get(url)
    local text
    if result then
        text = result.readAll()
        result.close()
        write_into_webcache(url, text)
    else
        print('Warning: Cannot connect to ' .. url .. '. Attempting to reach from webcache...')
        text = read_from_webcache(url)
        if not text then
            error('Unable to retrieve webpage from webcache')
        end
        print('Retrived webpage from webcache')
    end

    -- Some files (like the ones downloaded from google docs) start with this byte order mark
    -- We need to remove it so that the file processes properly

    -- This first string doesn't seem to work with my local version of lua but does with
    -- ComputerCraft. My local lua converts \239 into an intersect symbol, which isn't correct.
    local utf8_byte_order_mark_computercraft = '\239\187\191'
    local utf8_byte_order_mark_local_lua = '\139\175\168'
    if text:match("^"..utf8_byte_order_mark_computercraft) then
        text = text:match("^"..utf8_byte_order_mark_computercraft.."(.*)$")
    end

    return text
end