Module:Diff

-----------------------------------------------------------------------------
-- Provides functions for diffing text.
--
-- (c) 2007, 2008  Yuri Takhteyev (yuri@freewisdom.org)
-- (c) 2007 Hisham Muhammad
-- Adapted to MediaWiki Lua originally by User:Ebrahim
--
-- License: MIT/X, see http://sputnik.freewisdom.org/en/License
-----------------------------------------------------------------------------

local SKIP_SEPARATOR = true  -- a constant

-- token statuses
local IN   = "in"
local OUT  = "out"
local SAME = "same"

-----------------------------------------------------------------------------
-- Split a string into tokens.  (Adapted from Gavin Kistner's split on
-- http://lua-users.org/wiki/SplitJoin.
--
-- @param text           A string to be split.
-- @param separator      [optional] the separator pattern (defaults to any
--                       whitespace - %s+).
-- @param skip_separator [optional] don't include the separator in the results.
-- @return               A list of tokens.
-----------------------------------------------------------------------------
local function split(text, separator, skip_separator)
	separator = separator or "%s+"
	local parts = {}
	local start = 1
	local split_start, split_end = mw.ustring.find(text, separator, start)
	while split_start do
		table.insert(parts, mw.ustring.sub(text, start, split_start-1))
		if not skip_separator then
			table.insert(parts, mw.ustring.sub(text, split_start, split_end))
		end
		start = split_end + 1
		split_start, split_end = mw.ustring.find(text, separator, start)
	end
	if mw.ustring.sub(text, start) ~= "" then
		table.insert(parts, mw.ustring.sub(text, start))
	end
	return parts
end


-----------------------------------------------------------------------------
-- Derives the longest common subsequence of two strings.  This is a faster
-- implementation than one provided by stdlib.  Submitted by Hisham Muhammad.
-- The algorithm was taken from:
-- http://en.wikibooks.org/wiki/Algorithm_implementation/Strings/Longest_common_subsequence
--
-- @param t1             the first string.
-- @param t2             the second string.
-- @return               the least common subsequence as a matrix.
-----------------------------------------------------------------------------
local function quick_LCS(t1, t2)
	local m = #t1
	local n = #t2

	-- Build matrix on demand
	local C = {}
	local setmetatable = setmetatable
	local mt_tbl = {
		__index = function(t, k)
			t[k] = 0
			return 0
		end
	}
	local mt_C = {
		__index = function(t, k)
			local tbl = {}
			setmetatable(tbl, mt_tbl)
			t[k] = tbl
			return tbl
		end
	}
	setmetatable(C, mt_C)
	local max = math.max
	for i = 1, m+1 do
		local ci1 = C[i+1]
		local ci = C[i]
		for j = 1, n+1 do
			if t1[i-1] == t2[j-1] then
				ci1[j+1] = ci[j] + 1
			else
				ci1[j+1] = max(ci1[j], ci[j+1])
			end
		end
	end
	return C
end



-----------------------------------------------------------------------------
-- Formats an inline diff as HTML, with <ins> and <del> tags.
--
-- @param tokens         a table of {token, status} pairs.
-- @return               an HTML string.
-----------------------------------------------------------------------------
local function format_as_html(tokens)
	local diff_buffer = ""
	local token, status
	for i, token_record in ipairs(tokens) do
		token = mw.text.nowiki(token_record[1])
		status = token_record[2]
		if status == "in" then
			diff_buffer = diff_buffer..'<ins>'..token..'</ins>'
		elseif status == "out" then
			diff_buffer = diff_buffer..'<del>'..token..'</del>'
		else
			diff_buffer = diff_buffer..token
		end
	end
	return diff_buffer
end

-----------------------------------------------------------------------------
-- Returns a diff of two strings as a list of pairs, where the first value
-- represents a token and the second the token's status ("same", "in", "out").
--
-- @param old             The "old" text string
-- @param new             The "new" text string
-- @param separator      [optional] the separator pattern (defaults to any
--                       whitespace).
-- @return               A list of annotated tokens.
-----------------------------------------------------------------------------
local function diff(old, new, separator)
	assert(old); assert(new)
	new = split(new, separator); old = split(old, separator)

	-- First, compare the beginnings and ends of strings to remove the common
	-- prefix and suffix.  Chances are, there is only a small number of tokens
	-- in the middle that differ, in which case  we can save ourselves a lot
	-- in terms of LCS computation.
	local prefix = "" -- common text in the beginning
	local suffix = "" -- common text in the end
	while old[1] and old[1] == new[1] do
		local token = table.remove(old, 1)
		table.remove(new, 1)
		prefix = prefix..token
	end
	while old[#old] and old[#old] == new[#new] do
		local token = table.remove(old)
		table.remove(new)
		suffix = token..suffix
	end

	-- Setup a table that will store the diff (an upvalue for get_diff). We'll
	-- store it in the reverse order to allow for tail calls.  We'll also keep
	-- in this table functions to handle different events.
	local rev_diff = {
		put  = function(self, token, type) table.insert(self, {token,type}) end,
		ins  = function(self, token) self:put(token, IN) end,
		del  = function(self, token) self:put(token, OUT) end,
		same = function(self, token) if token then self:put(token, SAME) end end,
	}

	-- Put the suffix as the first token (we are storing the diff in the
	-- reverse order)

	rev_diff:same(suffix)

	-- Define a function that will scan the LCS matrix backwards and build the
	-- diff output recursively.
	local function get_diff(C, old, new, i, j)
		local old_i = old[i]
		local new_j = new[j]
		if i >= 1 and j >= 1 and old_i == new_j then
			rev_diff:same(old_i)
			return get_diff(C, old, new, i-1, j-1)
		else
			local Cij1 = C[i][j-1]
			local Ci1j = C[i-1][j]
			if j >= 1 and (i == 0 or Cij1 >= Ci1j) then
				rev_diff:ins(new_j)
				return get_diff(C, old, new, i, j-1)
			elseif i >= 1 and (j == 0 or Cij1 < Ci1j) then
				rev_diff:del(old_i)
				return get_diff(C, old, new, i-1, j)
			end
		end
	end
	-- Then call it.
	get_diff(quick_LCS(old, new), old, new, #old + 1, #new + 1)

	-- Put the prefix in at the end
	rev_diff:same(prefix)

	-- Reverse the diff.
	local diff = {}

	for i = #rev_diff, 1, -1 do
		table.insert(diff, rev_diff[i])
	end
	diff.to_html = format_as_html
	return diff
end

-----------------------------------------------------------------------------
-- Wiki diff style, currently just for a line
-----------------------------------------------------------------------------
local function wikiDiff(old, new, separator)
	local tokens = diff(old, new, separator)
	local root = mw.html.create('')

	local token, status

	local plusMinusStyle = 'width: 2%; padding: 0.25em; font-weight: bold;' ..
		'font-size: 1.25em; text-align: end;'
	local tdDivStyle = 'word-wrap: break-word; direction: ltr;'

	local tdSharedStyle = 'vertical-align:top; width: 48%; border-style: solid; border-radius: 0.33em; ' ..
		'padding: 0.33em 0.5em; color: inherit; font-size: 1em; font-family: monospace; white-space: pre-wrap; border-width: 1px 1px 1px 4px; ' ..
		'-webkit-border-end-width: 1px; -webkit-border-start-width: 4px; ' ..
		'-moz-border-end-width: 1px; -moz-border-start-width: 4px;' -- these override default border-width for browsers that support them, needed for RTL UI on commons
	local insDelSharedStyle = 'padding: 0.25em 0; font-weight: bold; text-decoration: initial;'


	local tr = root:tag('table'):addClass('diff'):css('width', '100%'):tag('tr')

	tr:tag('td')
		:addClass('diff-marker')
		:cssText(plusMinusStyle)
		:wikitext('−')

	local deleted = tr
		:tag('td')
			:cssText('border-color: var(--background-color-content-removed,#ffe49c); ' .. tdSharedStyle)
			:addClass('diff-deletedline')
			:tag('div')
				:cssText(tdDivStyle)

	for i, token_record in ipairs(tokens) do
		token = mw.text.nowiki(token_record[1]):gsub("\n", "&#10;") -- Force all newlines to encode to avoid linter issues
		status = token_record[2]
		if status == OUT then
			deleted
				:tag('del')
					:cssText('background: var(--background-color-content-removed,#ffe49c); color: inherit; ' .. insDelSharedStyle)
					:addClass('diffchange')
					:addClass('diffchange-inline')
					:wikitext(token)
		elseif status == SAME then
			deleted:wikitext(token)
		end
	end

	tr:tag('td')
		:cssText(plusMinusStyle)
		:wikitext('+')

	local inserted = tr
		:tag('td')
			:cssText('border-color: var(--background-color-content-added,#a3d3ff); ' .. tdSharedStyle)
			:addClass('diff-addedline')
			:tag('div')
				:cssText(tdDivStyle)

	for i, token_record in ipairs(tokens) do
		token = mw.text.nowiki(token_record[1]):gsub("\n", "&#10;") -- Force all newlines to encode to avoid linter issues
		status = token_record[2]
		if status == IN then
			inserted
				:tag('ins')
					:cssText('background: var(--background-color-content-added,#a3d3ff); color: inherit; ' .. insDelSharedStyle)
					:addClass('diffchange')
					:addClass('diffchange-inline')
					:wikitext(token)
		elseif status == SAME then
			inserted:wikitext(token)
		end
	end

	return tostring(root)
end

local function main(frame)
	return wikiDiff(mw.text.decode(mw.text.unstrip(frame.args[1])), mw.text.decode(mw.text.unstrip(frame.args[2])), frame.args[3] or '[%s%.:-]+')
end

return {
	diff = diff,
	wikiDiff = wikiDiff,
	main = main
}
Module:Diff

Usage

Difference in words

Difference in characters

Example with invoke
