App 03 - Date and Time

--# Main
-- App 03 - Date and Time

-- Bruce Elliott
-- April 2013

-- A tutorial on using time and date

-- os.time() - number argument to os.date or os.difftime
-- os.date() - string or table with date and time
-- os.clock() - approx. time in seconds of CPU time used by program

-- os.difftime() - number of seconds from t2 to t1
-- os.setlocale() - set locale of the program

-- Some information from Programming in Lua Chap. 22.1

function setup()

    time1 = os.clock()


    parameter.action("os.Time", osTime)
    parameter.action("os.Date", osDate)
    parameter.action("os.Date(param)", osDate2)
    parameter.action("os.clock", osClock)

    print("Date and Time functions")
    print(" ")
    print("Press a button to see that action")
    print("Read comments for explanations")
    print("Scroll Output window text up and down")

end

function osClock()

    --os.clock and os.difftime

    -- os.clock returns approx. CPU time used
    -- os.difftime returns difference in approx. seconds

    output.clear()

    --
    print("clock 1: "..time1)

    -- Capture end time
    time2 = os.clock()

    print("clock 2: "..time2)

    -- Compute CPU time used
    diftime = os.difftime(time2, time1)

    -- Display results
    print("time2: "..time2.. " minus time1:"..time1)
    print("CPU time used:".. diftime.." seconds")

end

function osDate()

    -- os.date( )
    -- Field name, meanings
    --    hour    24 hr format
    --    min
    --    wday    1 is Sunday
    --    day
    --    month
    --    year
    --    sec
    --    yday    1 is January 1
    --    isdst   is daylight saving time


    ----
    -- The date function, despite its name, is a kind of a
    -- reverse of the time function: It converts a number
    -- representing the date and time back to some higher-level
    -- representation. Its first parameter is a format string,
    -- describing the representation we want. The second is the
    -- numeric date-time; it defaults to the current date and time.
    -- Programming in Lua

    output.clear()

    -- os.date()
    -- no parameter returns current date time value
    print("os.date Examples")
    daytime = os.date()
    print("daytime = os.date()")
    print("print(daytime)")
    print()
    print("output: ")
    print(daytime)


    -- To produce a date table, we use the format string "*t".
    -- For instance, the following code

    print("")
    print("dval = os.time()")
    print("temp = os.date(\"*t\", dval)")
    -- Use os.time to get date time number
    dval = os.time()
    -- Use os.date to build table temp
    temp = os.date("*t", dval)

    -- creates the table we use to display the os.time() data
    -- We can display the table useing this code
    -- The isdst fiels is boolean and boolean data can not
    -- be concatenated.
    print("")
    print("temp Table Value output")
    for k, v in pairs(temp) do
        -- Check for isdst ~= means not equal
        if k ~= "isdst" then
            print("Key: "..k .." Value: ".. v)
        end
    end

    -- Display last value from table
    if temp["isdst"] == true then
        print("isdst is true")
    else
        print("isdst is false")
    end

end


function osTime()

    output.clear()

    -- os.time()

    -- os.time returns a number that represents
    -- date and time information

    -- os.time() no parameter
    -- Store os.time as number

    print("ostime = os.time()")
    ostime = os.time()

    -- Print result
    print("os.time value: "..ostime)

    -- Display os.time as os.date table fields
    osTimeOutput:output(ostime)

    -- os.time(table)
    -- Convert table data to number
    -- table requires at least three fields year, month, day
    -- field order does not appear to matter
    -- os.time{} and os.time({}) both appear to work
    -- try each format and order:

    --newtime = os.time({year = 2013, month = 4, day = 23})
    --newtime = os.time({month = 4, day = 23, year = 2013})
    print("newtime =")
    print("os.time{day=23, year=2013, month=4}")
    newtime = os.time{day = 23, year = 2013, month = 4}

    print("newtime value: "..newtime)

    print("Output os.time data")
    osTimeOutput:output(newtime)

    -- Notice that returned time data may not be accurate
    -- supply hour, min, sec, isdst if important
    --    newtime = os.time{day = 23, year = 2013, month = 4, hour = 10}
    -- osTimeOutput:output(newtime)


end

function osDate2()

    -- os.date("*t", dval) produces the table
    -- {year = 1998, month = 9, day = 16,
    --    yday = 259, wday = 4, hour = 23, min = 48,
    --    sec = 10, isdst = false}
    -- The actual values differ based on current date and time

    -- Notice that, besides the fields used by os.time, the table
    -- created by os.date also gives the week day (wday, 1 is Sunday)
    -- and the year day (yday, 1 is January 1).

    -- For other format strings, os.date formats the date as a string,
    -- which is a copy of the format string where specific tags
    -- are replaced by information about time and date.
    -- All tags are represented by a `%´ followed by a letter,
    -- as in the next examples: (from Programming in Lua )

    output.clear()

    print("print(os.date(\"today is \%A, in \%B\")")
    print(os.date("today is %A, in %B"))
      -- example output--> today is Tuesday, in May
    print("print(os.date(\"\%x\", 906000490))")
    print(os.date("%x", 906000490))
      --> 09/16/1998

    -- Here is the Programming in Lua table of format characters:

    --    %a    abbreviated weekday name (e.g., Wed)
    --    %A    full weekday name (e.g., Wednesday)
    --    %b    abbreviated month name (e.g., Sep)
    --    %B    full month name (e.g., September)
    --    %c    date and time (e.g., 09/16/98 23:48:10)
    --    %d    day of the month (16) [01-31]
    --    %H    hour, using a 24-hour clock (23) [00-23]
    --    %I    hour, using a 12-hour clock (11) [01-12]
    --    %M    minute (48) [00-59]
    --    %m    month (09) [01-12]
    --    %p    either "am" or "pm" (pm)
    --    %S    second (10) [00-61]
    --    %w    weekday (3) [0-6 = Sunday-Saturday]
    --    %x    date (e.g., 09/16/98)
    --    %X    time (e.g., 23:48:10)
    --    %Y    full year (1998)
    --    %y    two-digit year (98) [00-99]
    --    %%    the character `%´

    -- These can be used in various combinations
    -- For instance to get two digit year, month, day,
    -- hour, minute, and second as a single string:

    print("thisdate = os.date(\"\%y\%m\%d\%H\%M\%S\")")
    thisdate = os.date("%y%m%d%H%M%S")
    print("Formatted date: ".. thisdate)

    --Here are the codes used
    -- %y two digit year   %m two digit month
    -- %d two digit day    %H 24 hour hour
    -- %M two digit minute %S two digit sec

    -- Notice that %H formatted the hour in 24 hour format
    -- %I would give 12 hour format

    -- This investigation started because I wanted to create
    -- a unique filename for storing camera shots

end




--# osTimeOutput
osTimeOutput = class()

function osTimeOutput:output(ostime)
    -- Convert ostime to a table

    -- Convert os.time data to a table
    timeTab = os.date("*t", ostime)

    -- Display table keys and values
    -- Note: The last value is a boolean value. An attempt to
    -- concatenate boolean results in error
    for k, v in pairs(timeTab) do
        if k ~= "isdst" then
            p2 = "Key: "..k .." ".. "Value: "..v
            print(p2)
        end
    end

    -- Display last value from table
    if timeTab["isdst"] == true then
        print("isdst is true")
    else
        print("isdst is false")
    end
end