# Module:Japanese calendar

-- 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
-- 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 == mw.getCurrentFrame then
origArgs = :getParent.args
for k, v in pairs( .args ) do
origArgs = .args
break
end
else
origArgs =
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 '<strong>Module:Japanese calendar error: you can only specify one parameter out of "next", "previous" and "old".</strong>'
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 )
}