local p = {}



local function advance_pos_if_starts_with(str, pattern, pos)

	local i, j = mw.ustring.find(str, pattern, pos)

	if i == pos and j >= i then

		return j + 1

	else

		return pos

	end

end



local function advance_by_prefixes(str, prefixes, pos)

	for _, prefix in ipairs(prefixes) do

		pos = advance_pos_if_starts_with(str, prefix, pos)

	end

	

	return pos

end



-- [[d:Property:P428#P1793]]

-- ('t )?(d')?(de )?(la )?(van (der )?)?(Ma?c)?(De)?(Di)?\p{Lu}?C?['\p{Ll}]*([-'. ]*(van )?(y )?(d[ae][nr]?[- ])?(Ma?c)?[\p{Lu}bht]?C?['\p{Ll}]*)*\.? ?f?\.?

function p.find_end_of_author_citation(str, i, j)

	local pos = i or 1

	pos = advance_by_prefixes(str, {

		"'t ", "d'", "de ", "la ", "van der ", "van ", "Ma?c", "De", "Di", "%u?C?['%l]*",

	}, pos)

	

	repeat

		local orig_pos = pos

		pos = advance_by_prefixes(str, {

			"Ma?c", "[%ubht]?C?", "['%l]*", "[-'. ]*", "d[ae][nr]?[- ]", "van ", "y "

		}, pos)

	until orig_pos == pos

	

	pos = advance_pos_if_starts_with(str, "%.? ?f?%.?", pos)

	

	local last_char = mw.ustring.sub(str, pos - 1, pos - 1)

	if last_char == " " or last_char == "-" or last_char == "'" then

		pos = pos - 1

	end

	

	if pos and (not j or pos <= j) then

		return pos - 1

	end

end



-- Does not attempt to validate form of author citation. Returns successfully if

-- the citation is composed of valid author citations separated by

-- single commas, parentheses, or ampersands with optional whitespace around

-- them.

function p.transform_author_abbrevs(citation, func)

	local pos = 1

	local output = {}

	local remaining = citation

	while #remaining > 0 do

		local orig_pos = pos

		pos = advance_pos_if_starts_with(remaining, "%s*[(),&]%s*", pos)

		if orig_pos == pos and #output > 0 then

			return nil

		end

		local author_end = p.find_end_of_author_citation(remaining, pos)

		if not author_end then

			return nil

		end

		local author = mw.ustring.sub(remaining, pos, author_end)

		table.insert(output, mw.ustring.sub(remaining, 1, pos - 1))

		table.insert(output, func(author) or author)

		remaining = mw.ustring.sub(remaining, author_end + 1)

		pos = 1

	end

	

	if remaining == "" then

		return table.concat(output)

	end

end



-- Currently using IPNI convention of no spaces after initials.

local author_abbrevs = {

	"L." = "Carl Linnaeus",

	"Schldl." = "Diederich Franz Leonhard von Schlechtendal",

    "Cham." = "Adelbert von Chamisso",

    "B.Boivin" = "Joseph Robert Bernard Boivin",

    "A.J.Eames" = "Arthur Johnson Eames",

}



function p.standardize_abbrev(abbrev)

	return (abbrev:gsub("%.%s+", "."))

end



-- Adapted from getBotanicalAuthorityFromWikiData in [[Module:Taxon authority]].

function p.get_botanist_author_abbreviation(name)

	local wikidata_id = mw.wikibase.getEntityIdForTitle(name)



    if not (wikidata_id and mw.wikibase.isValidEntityId(wikidata_id)) then

    	local title_obj = mw.title.new(name).redirectTarget

		if title_obj and title_obj.text then

			wikidata_id = mw.wikibase.getEntityIdForTitle(name)

		end

    end



	if wikidata_id and mw.wikibase.isValidEntityId(wikidata_id) then -- valid Wikidata id

    	local item = mw.wikibase.getEntity(wikidata_id)

    	local statements = item:getBestStatements('P428')[1 -- botanist author abbreviation

        if statements ~= nil then

	    	return statements.mainsnak.datavalue.value

        end

    end

    return nil

end



function p.link_author_citation(citation)

	return p.transform_author_abbrevs(

		citation,

		function (author)

			local full_name = author_abbrevsp.standardize_abbrev(author)]

			if full_name then

				return "[[" .. full_name .. "|" .. author .. "]]"

			elseif p.get_botanist_author_abbreviation(author) then

				return "[[" .. author .. "]]"

			end

		end)

end



return p