CCalendar

--[[
Author: TheOriginalBIT
Version: 1.1
Created: 03 Feb 2013
Last Update: 10 Mar 2013

License:

COPYRIGHT NOTICE
Copyright © 2013 Joshua Asbury a.k.a TheOriginalBIT [theoriginalbit@gmail.com]

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and
associated documentation files (the "Software"), to deal in the Software without restriction,
including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense,
copies of the Software, and to permit persons to whom the Software is furnished to do so,
subject to the following conditions:

-The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
-Visible credit is given to the original author.
-The software is distributed in a non-profit way.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
]]--

if not os.day then
  print("Sorry but you don't seem to be running the version of ComputerCraft that this program requires (1.48+)")
  return
end

local useShorthand = false
local useAmPm = false
local refreshRate = 0.05

-- argument override
local argv = {...}

local ignoreNext = false
for i = 1, #argv do
  local v = argv[i]
  if v == '-ds' then
    useShorthand = true
  elseif v == '-ts' then
    useAmPm = true
  elseif v == '-rr' then
    refreshRate = tonumber(argv[i+1])
    ignoreNext = true
  elseif not ignoreNext then
    printError("Error: Invalid runtime parameter, "..v)
    error()
  elseif ignoreNext then
    ignoreNext = false
  end
end

-- initialise variables
local currentYear = 1
local currentMonth = 1
local currentDay = 1
local isLeapYear = (currentYear % 4 == 0 and (currentYear % 100 > 0 or  currentYear % 400 == 0))
local yearPrefix = "AS (After Spawn)"

local monthsTable = {
  {month="January", days=31, shorthand="JAN"},
  {month="February", days=28, shorthand="FEB"},
  {month="March", days=31, shorthand="MAR"},
  {month="April", days=30, shorthand="APR"},
  {month="May", days=31, shorthand="MAY"},
  {month="June", days=30, shorthand="JUNE"},
  {month="July", days=31, shorthand="JULY"},
  {month="August", days=31, shorthand="AUG"},
  {month="September", days=30, shorthand="SEPT"},
  {month="October", days=31, shorthand="OCT"},
  {month="November", days=30, shorthand="NOV"},
  {month="December", days=31, shorthand="DEC"},
}

local daysTable = {
  {day="Monday", shorthand="MON"},
  {day="Tuesday", shorthand="TUE"},
  {day="Wednesday", shorthand="WED"},
  {day="Thursday", shorthand="THU"},
  {day="Friday", shorthand="FRI"},
  {day="Saturday", shorthand="SAT"},
  {day="Sunday", shorthand="SUN"},
}

local function updateLeapYear(year)
  isLeapYear = (currentYear % 4 == 0 and (currentYear % 100 > 0 or  currentYear % 400 == 0))
end

local function updateYear(days)
  currentYear = math.floor(days/(isLeapYear and 366 or 365)+1)
  updateLeapYear(year)
end

local function updateMonth(days)
  local shiftedDays = days%366
  local d = 0
  for i = 1, #monthsTable do
    local before = d
    if i == 2 and isLeapYear then
      d = d + 29
    else
      d = d + monthsTable[i].days
    end
    if shiftedDays >= before and shiftedDays <= d then
      currentMonth = i
      return
    end
  end
end

local function updateDay(days)
  local shiftedDays = days%366
  for i = 1, currentMonth - 1 do
    shiftedDays = shiftedDays - monthsTable[i].days
  end
  currentDay = shiftedDays
end

local function hexToCol(hex)
  local num = tonumber(hex, 16)
  return num ~= nil and 2^num or nil
end

local function cwrite(msg, y, offset)
  local sw,sh=term.getSize()
  term.setCursorPos(sw/2-#msg/2, y or sh/2 + offset or 0)
  write(msg)
end

while true do
  term.clear()
  local dayCount = os.day()
  updateYear(dayCount)
  updateMonth(dayCount)
  updateDay(dayCount)
  cwrite("The time is: "..textutils.formatTime(os.time(), not useAmPm),nil,-2)
  cwrite("The date is: "..currentDay.." "..(useShorthand and monthsTable[currentMonth].shorthand or monthsTable[currentMonth].month).." "..string.format("%.4d",currentYear),nil,2)

  os.startTimer(refreshRate)
  os.pullEvent("timer")
end