Module:LangSwitcher

Documentation for this module may be created at Module:LangSwitcher/doc

-- Module:LangSwitcher
-- Robust wikitext language switcher for Base and Base/xx pages.

local p = {}

local function trim(s)
    return (s or ""):gsub("^%s+", ""):gsub("%s+$", "")
end

local function splitCSV(s)
    local t = {}
    if not s or s == "" then
        return t
    end
    for part in s:gmatch("([^,]+)") do
        local v = trim(part):lower()
        if v ~= "" then
            table.insert(t, v)
        end
    end
    return t
end

local function parseKVList(s)
    local out = {}
    if not s or s == "" then
        return out
    end
    for pair in s:gmatch("([^,]+)") do
        local k, v = pair:match("^%s*([^=]+)%s*=%s*(.-)%s*$")
        if k and v then
            out[trim(k):lower()] = trim(v)
        end
    end
    return out
end

-- Return base title text and current language code if page looks like Base/xx
local function getTitleParts()
    local title = mw.title.getCurrentTitle()

    -- If the page has a subpage segment and it looks like a language code, split it
    if title.subpageText ~= title.text then
        local last = title.subpageText
        local code = last:match("^([A-Za-z%-][A-Za-z%-][A-Za-z%-]*)$")
        if code then
            local baseTitle = mw.title.new(title.baseText, title.namespace)
            return baseTitle.fullText, code:lower(), title
        end
    end

    -- Otherwise, this is the base page
    return title.fullText, nil, title
end

-- Safely build the target page title for a given language code
local function makeTarget(baseFullText, code, defaultLang)
    if code == defaultLang then
        return baseFullText
    end
    -- Use title objects to preserve namespace and special chars
    local baseTitle = mw.title.new(baseFullText)
    if not baseTitle then
        return baseFullText .. "/" .. code
    end
    local targetTitle = mw.title.new(baseTitle.fullText .. "/" .. code, baseTitle.namespace)
    return (targetTitle and targetTitle.fullText) or (baseFullText .. "/" .. code)
end

local function pageExists(fullTitleText)
    local t = mw.title.new(fullTitleText)
    return t and t.exists
end

local function wikilink(page, label)
    return string.format('[[%s|%s]]', page, label)
end

local builtinNames = {
    en = "English",
    sv = "Svenska",
    da = "Dansk",
    nb = "Norsk bokmål",
    nn = "Nynorsk",
    no = "Norsk",
    fi = "Suomi",
    de = "Deutsch",
    fr = "Français",
    es = "Español",
    pt = "Português",
    ["pt-br"] = "Português (Brasil)",
    it = "Italiano",
    nl = "Nederlands",
    pl = "Polski",
    ru = "Русский",
    ja = "日本語",
    zh = "中文",
    ["zh-hans"] = "中文（简体）",
    ["zh-hant"] = "中文（繁體）",
    ko = "한국어",
}

function p.render(frame)
    local args = frame:getParent() and frame:getParent().args or frame.args

    local langs = splitCSV(args.langs or args.languages or "en")
    local labels = parseKVList(args.labels or "")
    local showMissing = (args.show_missing or ""):lower() == "yes"
    local icon = args.icon or ""
    local debug = (args.debug or ""):lower() == "yes"

    local base, currentLang = getTitleParts()
    local defaultLang = trim(args.default or (langs[1] or "en")):lower()

    local function labelFor(code)
        code = (code or ""):lower()
        return labels[code] or builtinNames[code] or code
    end

    -- Order: defaultLang first, then the rest uniquely
    local seen, ordered = {}, {}
    local function add(code)
        code = (code or ""):lower()
        if code ~= "" and not seen[code] then
            table.insert(ordered, code)
            seen[code] = true
        end
    end
    add(defaultLang)
    for _, code in ipairs(langs) do
        add(code)
    end

    local links, debugLines = {}, {}
    for _, code in ipairs(ordered) do
        local target = makeTarget(base, code, defaultLang)
        local exists = pageExists(target)
        if debug then
            table.insert(debugLines, string.format("code=%s target=%s exists=%s", code, target, tostring(exists)))
        end
        if exists or showMissing then
            local link = wikilink(target, labelFor(code))
            local isActive = currentLang and (currentLang == code) or (code == defaultLang)
            if isActive then
                link = "'''" .. link .. "'''"
            end
            table.insert(links, link)
        end
    end

    if #links == 0 then
        if debug then
            return "LangSwitcher: no links; base=" .. base .. (currentLang and (" current=" .. currentLang) or " current=(none)")
        end
        return ""
    end

    local pieces = {}
    if icon ~= "" then
        table.insert(pieces, "''" .. icon .. "'' ")
    end
    table.insert(pieces, table.concat(links, " • "))

    if debug and #debugLines > 0 then
        table.insert(pieces, "\n\n<small>" .. table.concat(debugLines, " • ") .. "</small>")
    end

    return table.concat(pieces)
end

return p