Module:URL

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

local p = {}
 
function trim(s)
    if s == nil then return '' end
    return (s:gsub("^%s*(.-)%s*$", "%1"))
end

function startsWith(s, prefix)
    return (s:find(prefix, 1, true)) == 1
end

function split(s, sep) -- string split function for a single-character separator
    local ret = {}
    local n = 1
    for w in s:gmatch("([^" .. sep .. "]*)") do
        ret[n] = ret[n] or w  -- only set once (so the blank after a string is ignored)
        if w == '' then n = n + 1 end -- step forwards on a blank but not a string
    end
    return ret
end

function rest(tbl, start) -- get the elements of the table beginning at the specified starting index
    local ret = {}
    if start > #tbl then
        return ret
    end
    for i = start, #tbl do
        ret[i - start + 1] = tbl[i]
    end
    return ret
end

function p._url(url, text)
    local lcUrl = url:lower()
    if not startsWith(lcUrl, 'http://') and not startsWith(lcUrl, 'https://') and not startsWith(lcUrl, 'ftp://') then
        url = 'http://' .. url
    end
    
    if text == '' then
        local comps = split(url, '/')
        local host = comps[3]
        local path = table.concat(rest(comps, 4), '/')

        local idx = host:find('?') or host:find('#') -- if there's a query string or anchor directly after the host name, without the default path ("/") in between, its case should be preserved
        if idx == nil then
            host = host:lower() 
        else
            host = host:sub(1, idx - 1):lower() .. host:sub(idx)
        end
        
        text = host
        if path ~= '' then
            text = text .. '/' .. path
        end
    end
    
    return string.format('<span class="url">[%s %s]</span>', url, text)
end

function p.url(frame)
    local url = trim(frame.args[1])
    local text = trim(frame.args[2])

    if url == '' then
        if text == '' then
            return frame:expandTemplate{ title = 'tlx', args = { 'URL', "''example.com''", "''optional display text''" } }
        else
            url = text
        end
    end
    
    return p._url(url, text)
end

return p