local p = {}
-- Create a table t to hold the data from Module:Appear/data
local t = mw.loadData('Module:Appear/data')
-- Create a table to see which seasons have been written and which haven't
local seasons = {}
local writeAll, writeSeason, writeEpisode, writeSidenote
 
-- Sends the arguments given to the template to the write function
-- and returns everything put together into a string
function p.main(frame)
    local text = ""
    local args = frame:getParent().args
    for i, v in ipairs(args) do
        if v ~= '' then
            if i ~= 1 then
                text = text .. '\n'
            end
            text = text .. writeAll(v)
        end
    end
    return text
end
 
-- Splits the argument into pieces and sends the right pieces to
-- writeSeason, writeEpisode, and writeSidenote
-- They are then put together and returned
writeAll = function (arg)
    local seasoncode = ""
    local episodecode = ""
    local sidenotecode = ""
    -- "gtest" is for first 2 characters of arg to see if input is a game, intro, or all.
    local gtest = arg:sub(1, 2)
    -- Tested in this order: game, all, intro, single episodes
    if gtest == 'DP' or gtest == 'NU' or gtest == 'NB' or gtest == 'NI' then
        local lowerIndex = arg:find( '%l' )
        seasoncode = 'game'
        if lowerIndex then
            episodecode = arg:sub(1, lowerIndex - 1)
            sidenotecode = arg:sub(lowerIndex)
        else
            episodecode = arg
        end
    elseif gtest == 'al' then
        seasoncode = arg:sub(4)
        episodecode = arg
    elseif gtest == 'in' then
        episodecode = 'intro'
    else
        --Episodecode and Sidenotecode
        --testing to see if lowercase is actually a sidenotecode since
        --lowercase 'a,' 'i,' 'o,' 't' exist in episode abbreviations
        local cftest = arg:find('f', -3) -- to test for sidenotecodes 'f' and 'fnl'
        local cnltest = arg:find('nl', -3) -- to test for sidenotecode 'nl'
        local cutest = arg:find('u', -3) -- to test for sidenotecode 'u'
        local cmtest = arg:find('m', -3) -- to test for sidenotecode 'm'
        local cptest = arg:find('p', -3) -- to test for sidenotecode 'p'
        local cltest = arg:find('l', -3) -- to test for sidenotecode 'l'
        
        --line below checks if sidenotecode was found
        if cftest or cnltest or cutest or cmtest or cptest or cltest then
            --testing for which sidenotecode
            --WARNING: do NOT change order!
            if cftest then
                episodecode = arg:sub(1, cftest - 1)
                sidenotecode = arg:sub(cftest)
            elseif cnltest then
                episodecode = arg:sub(1, cnltest - 1)
                sidenotecode = arg:sub(cnltest)
            elseif cutest then
                episodecode = arg:sub(1, cutest - 1)
                sidenotecode = arg:sub(cutest)
            elseif cmtest then
                episodecode = arg:sub(1, cmtest - 1)
                sidenotecode = arg:sub(cmtest)
            elseif cptest then
                episodecode = arg:sub(1, cptest - 1)
                sidenotecode = arg:sub(cptest)
            elseif cltest then
                episodecode = arg:sub(1, cltest - 1)
                sidenotecode = arg:sub(cltest)
            end
        else
            episodecode = arg --if there is no sidenotecode
        end
        --Seasoncode
        local epseason = t[episodecode]
        local snumber = epseason:sub(1, 1) --writing as extra step to show process
        seasoncode = snumber
    end
 
    local season = writeSeason(seasoncode)
    local episode = writeEpisode(episodecode)
    local sidenote = writeSidenote(sidenotecode)
    return season .. episode .. sidenote
end
 
writeSeason = function (season)
    if not seasons[season] and t[season] then
        seasons[season] = true
        return '===' .. t[season] .. '===\n'
    else
        return ''
    end
end
 
writeEpisode = function (episode)
    return '*' .. t[episode]
end
 
writeSidenote = function (sidenote)
    if t[sidenote] then
        return ' <sup>(' .. t[sidenote] .. ')</sup>'
    else
        return ''
    end
end
 
return p