-- This module defines an "era" class for processing eras in the Japanese calendar. -- It also contains functions to export the class properties to #invoke.

local eras = mw.loadData( 'Module:Japanese calendar/data' ) local halfToFull = require( 'Module:Convert character width' ).full -- Converts half-width characters to full-width characters.


-- Helper functions


local function yearToEraIndex( year )

   year = tonumber( year )
   if type( year ) ~= 'number' then return end
   for i, t in ipairs( eras ) do
       if year > t.startYear then
           return i
       elseif year == t.startYear then
           if eras[ i + 1 ] and eras[ i + 1 ].startYear == t.startYear then -- This checks for occasions when there were more than two eras in the same year. At the moment, that only applies to the year 686.
               return i + 1
           else
               return i
           end
       end
   end

end

local function textToEraIndex( s )

   if not s or s ==  then return end
   for i, t in ipairs( eras ) do
       if s == t.article or s == t.kanji then
           return i
       end
   end

end


-- Era class definition


local era = {} era.__index = era

function era:new( init )

   init = type( init ) == 'table' and init or {}
   local obj = {}
   
   -- Grab the data from the init table.
   obj.gregorianYear = tonumber( init.year )
   local initText = type( init.era ) == 'string' and init.era or nil
   local initIndex = tonumber( init.index )
   if not ( initIndex and initIndex >= 1 and math.floor( initIndex ) == initIndex and initIndex ~= math.huge ) then -- Check that initIndex is a positive integer.
       initIndex = nil
   end
   
   -- Calculate the era data from the input. First we find the era from the era index, although this is only supposed
   -- to be for internal use. Next we find the era from the era name or the kanji if possible, as this allows us to
   -- specify the last year of one era rather than the first year of the next one, if that is the desired behaviour.
   local eraIndex
   if initIndex then
       eraIndex = initIndex
   elseif initText then
       eraIndex = textToEraIndex( initText )
   elseif obj.gregorianYear then
       eraIndex = yearToEraIndex( obj.gregorianYear )
   end
   
   -- If the data entry was found for the era, process it and add it to the object.
   if not eraIndex then return end
   local eraData = eras[ eraIndex ]
   if not eraData or not eraData.article or eraData.article ==  then return end -- Exit if we are not dealing with a valid era.
   
   obj.startYear = eraData.startYear
   obj.endYear = eraData.endYear
   obj.article = eraData.article
   obj.kanji = eraData.kanji
   obj.label = eraData.label
   
   -- Create a link to the era article if possible.
   if obj.label and obj.article then
       obj.link = mw.ustring.format( '%s', obj.article, obj.label )
   elseif obj.article then
       obj.link = mw.ustring.format( '%s', obj.article )
   end
   
   -- Allow matching years to different eras, but only for the first year of the next era. For example, Taisho 15 is also Showa 1, but there is no such thing as Taisho 16.
   -- So, the code era:new{ year = 1926, era = "Taishō" } will return an object with an eraYear of 15, and era:new{ year = 1926 } will return an object with an eraYear of 1.
   local nextEraData = eras[ eraIndex - 1 ]
   local nextStartYear = nextEraData and nextEraData.startYear
   if obj.gregorianYear
       and ( -- If there is a later era, only allow the first year of that era or an earlier year.
           not nextStartYear
           or ( nextStartYear and obj.gregorianYear <= nextStartYear )
       )
       and obj.gregorianYear >= obj.startYear -- Don't allow negative years.
       and obj.article ~=  -- Don't allow periods between named eras.
       and ( obj.endYear and obj.gregorianYear <= obj.endYear or true ) -- If this era has an end year, don't allow years that are greater than the end year.
       then
       obj.eraYear = obj.gregorianYear - obj.startYear + 1
       if obj.eraYear == 1 then
           obj.eraYearKanji = '元'
       else
           obj.eraYearKanji = halfToFull( obj.eraYear )
       end
   end
   -- Make sure obj.label is available even if it is the same as the article name.
   obj.label = obj.label or obj.article
   
   -- Add methods to get the next and previous eras.
   function obj:getNextEra()
       if not eraIndex then return end       
       return era:new{ index = eraIndex - 1, year = obj.gregorianYear }
   end
   
   function obj:getPreviousEra()
       if not eraIndex then return end            
       return era:new{ index = eraIndex + 1, year = obj.gregorianYear }
   end
   -- Gets the era object for the "old" era. In most cases this is the same as the current era object, but
   -- if the era year for the current object is 1, this method will return the era object for the previous
   -- era. If the method can't find a valid previous era it will return the object for the current era.
   function obj:getOldEra()
       if obj.eraYear == 1 then
           local prevEra = obj:getPreviousEra()
           if prevEra then
               return prevEra
           else
               return obj
           end
       else
           return obj
       end
   end
   
   return setmetatable( obj, {
       __index = self
   })

end


-- Interface for old Japanese calendar templates


local function getStartYear( obj )

   return obj.startYear

end

local function getEndYear( obj )

   return obj.endYear

end

local function getEraYear( obj )

   return obj.eraYear

end

local function getEraYearKanji( obj )

   return obj.eraYearKanji

end

local function getArticle( obj )

   return obj.article

end

local function getLabel( obj )

   return obj.label

end

local function getLink( obj )

   return obj.link

end

local function getKanji( obj )

   return obj.kanji

end

local function getLabelAndEraYear( obj, kanji )

   local eraYear = kanji and obj.eraYearKanji or obj.eraYear
   if obj.label and eraYear then
       return mw.ustring.format( '%s %s', obj.label, tostring( eraYear ) )
   end

end

local function getLinkAndEraYear( obj, kanji )

   local eraYear = kanji and obj.eraYearKanji or obj.eraYear
   if obj.link and eraYear then
       return mw.ustring.format( '%s %s', obj.link, tostring( eraYear ) )
   end

end

local function getLabelAndEraYearKanji( obj )

   return getLabelAndEraYear( obj, true )

end

local function getLinkAndEraYearKanji( obj )

   return getLinkAndEraYear( obj, true )

end

-- Process the arguments from #invoke. local function makeWrapper( func )

   return function( frame )
       -- If called via #invoke, use the args passed into the invoking
       -- template, or the args passed to #invoke if any exist. Otherwise
       -- assume args are being passed directly in from the debug console
       -- or from another Lua module.
       local origArgs
       if frame == mw.getCurrentFrame() then
           origArgs = frame:getParent().args
           for k, v in pairs( frame.args ) do
               origArgs = frame.args
               break
           end
       else
           origArgs = frame
       end
       -- Trim whitespace and remove blank arguments.
       local args = {}
       for k, v in pairs( origArgs ) do
           if type( v ) == 'string' then
               v = mw.text.trim( v )
           end
           if v ~=  then
               args[k] = v
           end
       end
       
       local myEra
       local otherEraArgs = {}
       table.insert( otherEraArgs, args.next )
       table.insert( otherEraArgs, args.previous )
       table.insert( otherEraArgs, args.old )
       if #otherEraArgs > 1 then
           return 'Module:Japanese calendar error: you can only specify one parameter out of "next", "previous" and "old".'
       elseif args.next then
           myEra = era:new( args ):getNextEra()
       elseif args.previous then
           myEra = era:new( args ):getPreviousEra()
       elseif args.old then
           myEra = era:new( args ):getOldEra()
       else
           myEra = era:new( args )
       end
       return myEra and func( myEra ) or 
   end

end


-- Return the era class and the template interface


return {

   era = function () return era end, -- Accessor function for getting the era class from other modules.
   baseyear = makeWrapper( getStartYear ),
   endyear = makeWrapper( getEndYear ),
   year = makeWrapper( getEraYear ),
   kanjiyear = makeWrapper( getEraYearKanji ),
   article = makeWrapper( getArticle ),
   label = makeWrapper( getLabel ),
   link = makeWrapper( getLink ),
   kanji = makeWrapper( getKanji ),
   label_year = makeWrapper( getLabelAndEraYear ),
   link_year = makeWrapper( getLinkAndEraYear ),
   label_kanjiyear = makeWrapper( getLabelAndEraYearKanji ),
   link_kanjiyear = makeWrapper( getLinkAndEraYearKanji )

}