-- This module implements {{British regnal year}}. It converts a year in the Gregorian

-- calendar to the equivalent English or British regnal year.



local data = mw.loadData( 'Module:British regnal year/data' )



local p = {}



function p.main( frame )

    -- If we are being called from #invoke, then the year is the first positional

    -- argument. If not, it is the frame parameter.

    local inputYear

    if frame == mw.getCurrentFrame() then

        inputYear = frame:getParent().args 1 

        local frameArgsYear = frame.args 1 

        if frameArgsYear then

            inputYear = frameArgsYear

        end

    else

        inputYear = frame

    end



    -- Convert the input to an integer if possible. Return "N/A" if the input could

    -- not be converted, or if the converted input is too big or too small.

    if type( inputYear ) ~= 'number' then

        inputYear = tonumber( inputYear )

    end

    if not inputYear then

        return "''N/A''"

    end

    local currentYear = tonumber( mw.language.getContentLanguage():formatDate( 'Y' ) )

    -- The year 1066 is significant because it is when the Norman conquest of England occurred.

    if inputYear < 1066 or inputYear > currentYear then

        return "''N/A''"

    end

    

    -- Find the year in the data page and display the output.

    for _, t in ipairs( data ) do

        local dataYear = t.year

        if inputYear >= dataYear then

            -- Get data values from the data page.

            local startYear = t.startYear

            local currentRegnalYear = inputYear - dataYear + startYear

            local linkCurrent = t.linkCurrent

            local prevEndYear = t.prevEndYear

            local linkPrev = t.linkPrev

            local note = t.note



            if inputYear > dataYear then

                -- Years with the same monarch.

                return mw.ustring.format(

                    '%d&nbsp;%s&nbsp;–&nbsp;%d&nbsp;%s%s',

                    currentRegnalYear - 1, linkCurrent, currentRegnalYear, linkCurrent, note or ''

                )

            elseif inputYear == dataYear and prevEndYear and linkPrev then

                -- Years with a different monarch.

                return mw.ustring.format(

                    '%d&nbsp;%s&nbsp;–&nbsp;%d&nbsp;%s%s',

                    prevEndYear, linkPrev, currentRegnalYear, linkCurrent, note or ''

                )

            else

                -- This should only match the year 1066.

                return mw.ustring.format(

                    '%d&nbsp;%s%s',

                    currentRegnalYear, linkCurrent, note or ''

                )

            end

        end

    end

end



return p