Module:Wayback

local p = {}

--[[--------------------------< inline_error >-----------------------

Render red error message inline (as opposed to the system error() in large font) Add article to tracking category.

]]

function p.inline_error(arg, msg)

 return ''

end

--[[--------------------------< trimArg >-----------------------

trimArg returns nil if arg is "" while trimArg2 returns 'true' if arg is "" trimArg2 is for args that might accept an empty value, as an on/off switch like nolink=

]]

function p.trimArg(arg)

 if arg == "" or arg == nil then
   return nil
 else
   return mw.text.trim(arg)
 end

end function p.trimArg2(arg)

 if arg == nil then
   return nil
 else
   return mw.text.trim(arg)
 end

end

--[[--------------------------< isdf >-----------------------

Given df argument, return "yes" or "no" confirming what it is Default is "no". If df is nil or "", return "no".

]]

function isdf(df)

 if df == "yes" or df == "Yes" or df == "YES" or df == "y" or df == "Y" or df == "dmy" or df == "DMY" then
   return "yes"
 elseif df == "iso" or df == "ISO" then
    return "iso"
 end
 return "no"

end

--[[--------------------------< makedate >-----------------------

Given a year, month and day, convert into a full date while respecting df (dmy or mdy)

]]

function p.makedate(year, month, day, df)

 local nmonth, zmonth, zday

 if not year or year == "" or not month or month == "" or not day or day == "" then
   return nil
 end

 zmonth = month
 month = month:match("0*(%d+)")                                      -- strip leading 0
 if tonumber(month) < 1 or tonumber(month) > 12 then
   return year
 end
 nmonth = os.date("%B", os.time{year=2000, month=month, day=1} )     -- Month in name form       
 if not nmonth then
   return year
 end

 zday = day
 day = day:match("0*(%d+)")
 if tonumber(day) < 1 or tonumber(day) > 31 then
   return nmonth .. " " .. year
 end                                       

 if df == "yes" then
   return day .. " " .. nmonth .. " " .. year
 elseif df == "iso" then
   return year .. "-" .. zmonth .. "-" .. zday
 else
   return nmonth .. " " .. day .. ", " .. year
 end

end

--[[--------------------------< wayback >-----------------------

Main function for Template:wayback

]]

function p.wayback(frame)

 local pframe = frame:getParent()
 local args = pframe.args

 local tname = "Wayback"                                 -- name of calling template. Change if template rename.

 local url = nil                                         -- source url (not archive.org url)
 local title = nil                                       -- title argument
 local df = nil                                          -- df argument
 local comma = nil                                       -- "," for mdy or "" for dmy
 local snapdate = nil                                    -- eg. "20160520000000"
 local snapdatelong = nil                                -- 14-digit 0-padded version of snapdate if it is truncated
 local fulldate = nil                                    -- eg. "May 20, 2016"
 local currdate = nil                                    -- today's date
 local urlhead = "https://web.archive.org/web/"
 local tail = nil 
 local nolink = nil
 
                                                         -- URL argument (positional #1)

 url = p.trimArg(args[1]) or p.trimArg(args.url) or p.trimArg(args.site)                -- "site" for Template:Waybackdate
 if not url then
   return p.inline_error("url", "Empty.")
 end
 local safe = url
 local l, count = string.gsub(safe, "archive.org/?w?e?b?/[0-9]+/http", "")              -- Count number of "archive.org" 
 if count > 0 then 
   return p.inline_error("url", "Should be the original URL not an archive.org URL.")
 end 
 
                                                         -- Title argument (positional #2)

 title = p.trimArg(args[2]) or p.trimArg(args.title)

                                                         -- Date argument (positional #3)

 snapdate = p.trimArg(args[3]) or p.trimArg(args.date)
 if not snapdate or snapdate == "*" then
   snapdate = "*"
 else
   local safe = snapdate
   local starcount = 0
   snapdate = string.gsub(safe, "[a-z][a-z]_[0-9]?$", "")              -- Remove any trailing "re_" from date 
   safe = snapdate
   snapdate = string.gsub(safe, "[-]", "")                             -- Remove dashes from date eg. 2015-01-01 
   safe = snapdate
   snapdate, starcount = string.gsub(safe, "[*]$", "")                 -- Remove trailing "*" and re-add below after processing
   if not tonumber(snapdate) then
     return p.inline_error("date", "Should be 14-digit snapshot ID in form YYYYMMDDhhmmss (error code 1)")
   end
   local dlen = string.len(snapdate)
   if dlen < 4 then
     return p.inline_error("date", "Should be 14-digit snapshot ID in form YYYYMMDDhhmmss (error code 2)")
   end
   if dlen < 14 then
     snapdatelong = snapdate .. string.rep("0", 14 - dlen)
   else
     snapdatelong = snapdate
   end
   local year = string.sub(snapdatelong, 1, 4)
   local month = string.sub(snapdatelong, 5, 6)
   local day = string.sub(snapdatelong, 7, 8)
   if not tonumber(year) or not tonumber(month) or not tonumber(day) then
     return p.inline_error("date", "Should be 14-digit snapshot ID in form YYYYMMDDhhmmss (error code 3)")
   end
   if tonumber(month) > 12 or tonumber(day) > 31 or tonumber(month) < 1 then
     return p.inline_error("date", "Date has invalid day or month. (error code 4)")
   end
   currdate = os.date("%Y")
   if tonumber(year) > tonumber(currdate) or tonumber(year) < 1900 then
     return p.inline_error("date", "Date has invalid year. (error code 5)")
   end

   if starcount == 1 then
     snapdate = snapdate .. "*"
   end

   df = isdf( p.trimArg(args.df) )
   if df == "yes" then
     comma = ""
   else
     comma = ","
   end

   fulldate = p.makedate(year, month, day, df)

   if not fulldate then
     return p.inline_error("date", "(error code 6)")
   end

 end
                                                         -- Nolink argument 

 nolink = p.trimArg2(args.nolink)
 if not nolink then
   tail = " at the Wayback Machine"
 else
   tail = " at the Wayback Machine"
 end

                                                         -- Render 

 if not title and not fulldate then  -- No title. No date
   return "[" .. urlhead .. snapdate .. "/" .. url .. " Archive copy]" .. tail
 elseif not title and fulldate then  -- No title. Date.
   return "[" .. urlhead .. snapdate .. "/" .. url .. " Archived] " .. fulldate .. comma ..  tail .. "."
 elseif title and not fulldate then  -- Title. No date.
   return "[" .. urlhead .. snapdate .. "/" .. url .. " " .. title .. "]" .. tail
 elseif title and fulldate then          -- Title. Date.
   return "[" .. urlhead .. snapdate .. "/" .. url .. " " .. title .. "]" .. tail .. " (archived " .. fulldate .. ")"
 end

 error("Error in Template:"..tname..": Unknown problem. Please report on template talk page (code 7)")

end

return p