Modul:URIutil

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--[=[ URIutil 2014-12-29
Utilities for URI etc.
* coreISSN()
* formatISBN()
* formatISSN()
* formatLCCN()
* isDNBvalid()
* isDOI()
* isEscValid()
* isGTINvalid()
* isHandle()
* isISBN()
* isISBNvalid()
* isISSNvalid()
* isLCCN()
* linkDOI()
* linkHandle()
* linkISBN()
* linkISSN()
* linkLCCN()
* mayDOI()
* mayHandle()
* mayISBN()
* mayISSN()
* mayLCCN()
* mayURI()
* mayURN()
* plainISBN()
* uriDOI()
* uriHandle()
* URIutil()
loadData: URIutil/config URIutil/isbn
]=]



-- table for export
local URIutil = {};



local factory = function ( attempt, allowX )
    -- Retrieve plain digits of attempt
    -- Precondition:
    --     attempt  -- string; with digits (+xX) and hyphens, not trimmed
    --     allowX   -- number; of (last) position for permitted xX
    --                 boolean; xX at last position permitted
    -- Postcondition:
    --     Returns   table; success
    --                      [1]...[8]/[10]...[13]  -- digits 0...9
    --                                                10 at last position
    --                      .hyphens  -- number of hyphens
    --                      .type     -- number of digits
    --               number; no string or bad length or data
    --                        0  -- no string
    --                       >0  -- unexpected char at position (trimmed)
    local r;
    if type( attempt ) == "string" then
        local c, i;
        local j = 0;
        local k = 1;
        local s = mw.text.trim( attempt );
        local n = mw.ustring.len( s );
        r = { hyphens = 0 };
        for i = 1, n do
            c = mw.ustring.codepoint( s,  i,  i + 1 );
            if c >= 48  and  c <= 57 then
                j      = j + 1;
                r[ j ] = c - 48;
                k      = false;
            elseif c == 45 then    -- hyphen
                if i > 1  and  i < n then
                    r.hyphens = r.hyphens + 1;
                    k         = i;
                else
                    r = j;
                    break;
                end
            elseif c == 88  or  c == 120 then    -- X x
                j = j + 1;
                if allowX  and  i == n then
                    if allowX == true  or  allowX == j then
                        r[ j ] = 10;
                    else
                        r = j;
                    end
                else
                    r = j;
                end
                break;
            else
                r = j;
                break;
            end
        end -- for i
        if type( r ) == "table" then
            r.type = j;
        end
    else
        r = 0;
    end
    return r;
end -- factory()



local faculty = function ( ask, auto )
    -- Evaluate possible string as boolean signal, if brief
    -- Precondition:
    --    ask   -- trimmed string or nil or other
    --    auto  -- fallback value if nil
    -- Postcondition:
    --     Returns appropriate value, or ask
    local r;
    if type( ask ) == "string" then
        if ask == "1"  or  ask == "" then
            r = true;
        elseif ask == "0"  or  ask == "-" then
            r = false;
        else
            r = ask;
        end
    elseif ask == nil then
        r = auto;
    else
        r = ask;
    end
    return r;
end -- faculty()



local fair = function ( assert )
    -- Compute check digit (11 minus modulo 11) for descending factor
    -- Precondition:
    --     assert  -- table; as of factory()
    --                .type  -- number of digits including check digit
    -- Postcondition:
    --     Returns checksum
    local i;
    local n = assert.type;
    local k = n;
    local r = 0;
    for i = 1,  n - 1 do
        r = r  +  k * assert[ i ];
        k = k - 1;
    end -- for i
    return  ( 11  -  r % 11 );
end -- fair()



local format = function ( assigned, ahead, amount )
    -- Convert part of digit sequence into string
    -- Precondition:
    --     assigned  -- table; as of factory()
    --     ahead     -- index of first digit
    --     amount    -- number of digits to append
    -- Postcondition:
    --     Returns  string with digits and hyphens
    local i, k;
    local r = "";
    for i = ahead,  ahead + amount - 1 do
        k = assigned[ i ];
        if k == 10 then
            r = r .. "X";
        else
            r = r .. tostring( k );
        end
    end -- for i
    return r;
end -- format()



local DNBfaith = function ( assert, ancestor )
    -- Compute DNB (also GND, ZDB) check digit and verify
    -- Precondition:
    --     assert    -- table; as of factory()
    --                  .type  -- until 11 including check digit
    --     ancestor  -- true: 2011 mode
    -- Postcondition:
    --     Returns  true: check digit matches
    -- 2013-09-01
    local k = fair( assert )  %  11;
    if ancestor then
        k  =  11 - k;
    end
    return  ( k == assert[ assert.type ] );
end -- DNBfaith()



local GTINfair = function ( assert )
    -- Compute GTIN check digit
    -- Precondition:
    --     assert  -- table; ~ 13 digits
    --                       .type  -- 13 ...
    -- Postcondition:
    --     Returns  number 0...9
    local i, k;
    local lead = true;
    local r    = 0;
    for i = 1,  assert.type - 1 do
        k   = assert[ i ];
        r = r + k;
        if lead then    -- odd
            lead = false;
        else    -- even
            r  = r + k + k;
            lead = true;
        end
    end -- for i
    r = (10  -  r % 10)   %   10;
    return  r;
end -- GTINfair()



local GTINfaith = function ( assert )
    -- Compute GTIN check digit and verify
    -- Precondition:
    --     assert  -- table; ~ 13 digits
    --                       .type  -- 13 ...
    -- Postcondition:
    --     Returns  true: check digit matches
    return  ( GTINfair( assert )  ==  assert[ assert.type ] );
end -- GTINfaith()



local ISBNfactory = function ( attempt )
    -- Retrieve plain digits of ISBN attempt
    -- Precondition:
    --     attempt  -- string with digits (+xX) and hyphens, not trimmed
    -- Postcondition:
    --     Returns   table; success
    --                      [1]...[13]  -- digits 0...9
    --                                     10 at ISBN-10 last position
    --                      .type       -- 10 or 13
    --                      .hyphens    -- 0... number of hyphens
    --               number; no string or bad length or data
    --                        0  -- no string
    --                       >0  -- unexpected char at position (trimmed)
    --                       -1  -- bad digit count
    --                       -2  -- bad bookland
    local r;
    if type( attempt ) == "string" then
        r = factory( attempt, 10 );
        if type( r ) == "table" then
            if r.type == 13 then
                if r[1] ~= 9  or
                   r[2] ~= 7  or
                   r[3] < 8 then
                    r = -2;
                end
            elseif r.type ~= 10 then
                r = -1;
            end
        end
    else
        r = 0;
    end
    return r;
end -- ISBNfactory()



local ISBNfaith = function ( assert )
    -- Compute ISBN check digit and verify
    -- Precondition:
    --     assert  -- table; as of ISBNfactory()
    --                       .type  -- 10 or 13
    -- Postcondition:
    --     Returns  true: check digit matches
    local r;
    if assert.type == 10 then
        local i;
        local k = 0;
        for i = 1, 9 do
            k = k  +  i * assert[ i ];
        end -- for i
        k = k % 11;
        r = ( k == assert[ 10 ] );
    elseif assert.type == 13 then
        r = GTINfaith( assert );
    else
        r = false;
    end
    return r;
end -- ISBNfaith()



local ISBNflat = function ( assigned )
    -- Plain digits of attempt ISBN
    -- Precondition:
    --     assigned  -- table; as of ISBNfactory()
    -- Postcondition:
    --     Returns  string with digits; ISBN-10 with 'X' at last position
    local i;
    local r = "";
    local n = assigned.type;
    if n == 10 then
        if assigned[ assigned.type ] == 10 then
            n = 9;
        end
    end
    for i = 1, n do
        r = r .. tostring( assigned[ i ] );
    end -- for i
    if n == 9 then
        r = r .. "X";
    end
    return r;
end -- ISBNflat()



local ISBNfold = function ( assigned, apply, allocate, already )
    -- Retrieve number of digits for ISBN publisher/group
    -- Precondition:
    --     assigned  -- table; as of ISBNfactory()
    --     apply     -- number; of bookland (978 or 979)
    --     allocate  -- number; of country
    --     already   -- number; position in assigned to inspect
    -- Postcondition:
    --     Returns  number of digits, at least 0
    local r = 0;
    local lucky, def = pcall( mw.loadData, "Module:URIutil/isbn" );
    if type( def ) == "table"  then
        local bookland = def[ apply ];
        if type( bookland ) == "table"  then
            local country = bookland[ allocate ];
            if type( country ) == "table" then
                local e, i, j, k, m, v;
                for i = 1, 4 do
                    v = country[ i ];
                    if type( v ) == "table" then
                        m  =  tonumber( format( assigned, already, i ) );
                        for k, e in pairs( v ) do
                            if m >= e[ 1 ]  and  m <= e[ 2 ] then
                                r = e[ 3 ];
                                break; -- for k
                            end
                        end -- for k
                    end
                    if r > 0 then
                        break; -- for i
                    end
                end -- for i
            end
        end
    end
    return r;
end -- ISBNfold()



local ISBNformat = function ( attempt, assigned )
    -- Hyphen formatting; at least try minimum
    -- Precondition:
    --     attempt   -- string with presumable ISBN
    --     assigned  -- table; as of ISBNfactory()
    --                         .type     -- 10 or 13
    --                         .hyphens  -- 0...4
    -- Postcondition:
    --     Returns  string with digits and hyphens
    local r = false;
    local j, k, m, n;
    if assigned.type == 10 then
        m = 978;
        r = "";
        j = 1;
    else
        m = 970 + assigned[ 3 ];
        r = tostring( m ) .. "-";
        j = 4;
    end
    if assigned[ j ] < 8 then
        k = 1;
    else
        k = 2;
        if assigned[ j + 1 ] > 4 then
            k = 3;
            if assigned[ j + 1 ] > 8 then
                k = 4;
                if assigned[ j + 2 ] > 8 then
                    k = false;    -- invalid
                end
            end
        end
    end
    if k then
        n = format( assigned, j, k );
        r = r .. n .. "-";
        j = j + k;
        n = ISBNfold( assigned,  m,  tonumber( n ),  j );
        if n > 0 then
            r = r .. format( assigned, j, n ) .. "-";
            j = j + n;
        end
    end
    r = r .. format( assigned,  j,  assigned.type - j );
    if assigned[ assigned.type ] == 10 then
        r = r .. "-X";
    else
        r = r .. "-" .. tostring( assigned[ assigned.type ] );
    end
    if not r then
        r = mw.ustring.upper( mw.text.trim( attempt ) );
    end
    return r;
end -- ISBNformat()



local ISSNfactory = function ( attempt )
    -- Retrieve plain digits of ISSN attempt
    -- Precondition:
    --     attempt  -- string with digits (+xX) and hyphens, not trimmed
    -- Postcondition:
    --     Returns   table; success
    --                      [1]...[13]  -- digits 0...9
    --                                     10 at ISSN-8 last position
    --                      .type       -- 8 or 13
    --                      .hyphens    -- 0... number of hyphens
    --               number; no string or bad length or data
    --                        0  -- no string
    --                       >0  -- unexpected char at position (trimmed)
    --                       -1  -- bad digit count
    --                       -2  -- bad issnland
    local r;
    if type( attempt ) == "string" then
        r = factory( attempt, 8 );
        if type( r ) == "table" then
            if r.type == 13 then
                if r[1] ~= 9  or
                   r[2] ~= 7  or
                   r[3] ~= 7 then
                    r = -2;
                end
            elseif r.type ~= 8 then
                r = -1;
            end
        end
    else
        r = 0;
    end
    return r;
end -- ISSNfactory()



local ISSNfaith = function ( assert )
    -- Compute ISSN check digit and verify
    -- Precondition:
    --     assert  -- table; as of ISSNfactory()
    --                       .type  -- 8 or 13
    -- Postcondition:
    --     Returns  true: check digit matches
    local r;
    if assert.type == 8 then
        r = ( fair( assert )  ==  assert[ 8 ] );
    elseif assert.type == 13 then
        r = GTINfaith( assert );
    else
        r = false;
    end
    return r;
end -- ISSNfaith()



local ISSNformat = function ( assigned, achieve )
    -- Hyphen formatting of ISSN
    -- Precondition:
    --     assigned  -- table; as of ISSNfactory(), and valid
    --     achieve   -- 8 or 13
    -- Postcondition:
    --     Returns  string with digits and hyphens
    local r;
    if achieve == 8 then
        local x;
        if assigned.type == 8 then
            r = format( assigned, 1, 4 ) .. "-" ..
                format( assigned, 5, 3 );
            x = assigned[ 8 ];
        elseif assigned.type == 13 then
            r = format( assigned, 4, 4 ) .. "-" ..
                format( assigned, 8, 3 );
            x = fair( assigned );
        end
        if x == 10 then
            r = r .. "X";
        else
            r = r .. tostring( x );
        end
    elseif achieve == 13 then
        if assigned.type == 8 then
            r = "977-" .. format( assigned, 1, 7 ) .. "-00-"
                .. GTINfair( assigned );
        elseif assigned.type == 13 then
            r = "977-" .. format( assigned, 4, 7 )
                       .. format( assigned, 10, 2 ) .. "-"
                       .. tostring( assigned[ 13 ] );
        end
    end
    return r;
end -- ISSNformat()



local LCCNfactory = function ( attempt, allow )
    -- Retrieve segments of LCCN attempt (format since 2001)
    -- Precondition:
    --     attempt  -- string with presumable LCCN
    --     allow    -- false or string: "/"
    -- Postcondition:
    --     Returns  table; success
    --              false if not correct, bad data
    -- 2014-12-28
    local r   = false;
    local pat = "^%s*(%a*)(/?)(%d%S+)%s*$";
    local pre, sep, s = attempt:match( pat );
    if pre and s then
        local year, serial;
        if pre == "" then
            pre = false;
            if sep ~= "" then
                s = false;
            end
        elseif #pre > 3 then
            s = false;
        else
            pre = pre:lower();
        end
        if s then
            if allow ~= "/"  or  sep == "/" then
                if sep == "/" then
                    year, serial = s:match( "^(%d+)/(%d.+)$" );
                elseif s:find( "-", 2, true ) then
                    year, serial = s:match( "^(%d+)%-(%d.+)$" );
                else
                    year = s:match( "^([%d]+)" );
                    if year then
                        if #year <= 8 then
                            year   = s:sub( 1, 2 );
                            serial = s:sub( 3 );
                        elseif #year <= 10 then
                            year   = s:sub( 1, 4 );
                            serial = s:sub( 5 );
                        else
                            year   = false;
                            serial = s;
                        end
                    elseif tonumber( s ) then
                        serial = s;
                    end
                end
            end
            if year then
                if #year == 4 then
                    local n = tonumber( year );
                    if n <= 2000 then
                        -- 2000 -> "00"
                        serial = false;
                    elseif n > tonumber( os.date( "%Y" ) ) then
                        serial = false;
                    end
                elseif #year ~= 2 then
                    serial = false;
                end
            end
            if serial then
                r = { pre = pre, serial = serial };
                if year then
                    r.year = year;
                end
                if serial:find( "/", 2, true ) then
                    local q;
                    serial, q = serial:lower()
                                      :match( "^(%d+)/([a-z]+)$" );
                    if q == "dc" or
                       q == "mads" or
                       q == "marcxml" or
                       q == "mods" then
                        r.serial    = serial;
                        r.qualifier = q;
                    end
                end
                if serial then
                    serial = serial:match( "^0*([1-9]%d*)$" );
                end
                if not serial then
                    r = false;
                elseif #serial < 6 then
                    r.serial = mw.ustring.format( "%06d",
                                                  tonumber( serial ) );
                elseif #serial > 6 then
                    r = false;
                end
            end
        end
    end
    return r;
end -- LCCNfactory()



local LCCNformat = function ( assigned, achieve )
    -- Standard or hyphen or slash formatting of LCCN
    -- Precondition:
    --     assigned  -- table; as of LCCNfactory(), and valid
    --     achieve   -- additional formatting desires, like "-" or "/"
    -- Postcondition:
    --     Returns  string with letters, digits and hyphens
    -- 2013-07-14
    local r;
    if assigned.pre then
        r = assigned.pre;
    else
        r = "";
    end
    if assigned.year then
        if achieve == "/"  and  r ~= "" then
            r = r .. "/";
        end
        r = r .. assigned.year;
        if achieve then
            r = r .. achieve;
        end
    end
    if assigned.serial then
        r = r .. assigned.serial;
    end
    if assigned.qualifier then
        r = r .. "/" .. assigned.qualifier;
    end
    return r;
end -- LCCNformat()



local LCCNforward = function ( attempt, achieve )
    -- Retrieve bracketed titled external LCCN permalink
    -- Precondition:
    --     attempt  -- string with presumable LCCN
    --     achieve  -- additional title formatting desires, like "-"
    -- Postcondition:
    --     Returns  link, or plain attempt if bad LCCN
    -- 2013-07-14
    local lccn = LCCNfactory( attempt );
    local r;
    if lccn then
        r = LCCNformat( lccn, false );
        if r then
            if achieve then
                r = r .. " " .. LCCNformat( lccn, achieve );
            else
                r = r .. " " .. r;
            end
            r = "[http://lccn.loc.gov/" .. r .. "]";
        end
    else
        r = attempt;
    end
    return r;
end -- LCCNforward()



local URNnamespace = function ( area, acquire )
    -- Are these parts of a correct URN?
    -- Precondition:
    --     area     -- string with lowercase namespace
    --     acquire  -- string with identification
    -- Postcondition:
    --     Returns  false if no problem
    --              string with violation
    local lucky, r = pcall( mw.loadData, "Module:URIutil/config" );
    if type( r ) == "table" then
        r = r.urn;
        if type( r ) == "table" then
            local s = r.sns;
            if type( s ) == "string" then
                r = ":" .. area .. ":";
                if s:match( r ) then
                    s = "[^%w%(%)%+,%-%.:=@;%$_!%*'].*$";
                    r = acquire:match( s );
                else
                    r = "&#58;" .. area .. ":";
                end
                if not r then
                    r = false;
                    if area == "isbn" then
                        if not URIutil.isISBNvalid( acquire ) then
                            r = acquire;
                        end
                    elseif area == "issn" then
                        if not URIutil.isISSNvalid( acquire ) then
                            r = acquire;
                        end
                    end
                end
            else
                r = "Module:URIutil/config.urn.sns";
            end
        else
            r = "Module:URIutil/config.urn";
        end
    end
    return r;
end -- URNnamespace()



function URIutil.coreISSN( attempt )
    -- Fetch significant ISSN
    -- Precondition:
    --     attempt  -- string with presumable ISSN
    -- Postcondition:
    --     Returns   string with 7 digits, without check digit nor GTIN
    --               unmodified input if wrong
    local r;
    local issn = ISSNfactory( attempt );
    if type( issn ) == "table" then
        if issn.type == 8 then
            r = format( issn, 1, 7 );
        elseif issn.type == 13 then
            r = format( issn, 4, 7 );
        end
    else
        r = mw.ustring.upper( mw.text.trim( attempt ) );
    end
    return r;
end -- URIutil.coreISSN()



function URIutil.formatISBN( attempt, assigned )
    -- Format ISBN, if no hyphens present
    -- Precondition:
    --     attempt   -- string with presumable ISBN
    --     assigned  -- table or false; as of ISBNfactory()
    -- Postcondition:
    --     Returns   string with some hyphens, if not yet
    --               unmodified input if already hyphens or wrong
    local r;
    local isbn;
    if type( assigned ) == "table" then
        isbn = assigned;
    else
        isbn = ISBNfactory( attempt );
    end
    if type( isbn ) == "table" then
        r = ISBNformat( attempt, isbn );
    else
        r = mw.ustring.upper( mw.text.trim( attempt ) );
    end
    return r;
end -- URIutil.formatISBN()



function URIutil.formatISSN( attempt, achieve )
    -- Format ISSN
    -- Precondition:
    --     attempt  -- string with presumable ISSN
    --     achieve  -- false or 8 or 13; requested presentation
    -- Postcondition:
    --     Returns   string with some hyphens, if not yet
    --               unmodified input if already hyphens or wrong
    local r    = false;
    local issn = ISSNfactory( attempt );
    if type( issn ) == "table" then
        if ISSNfaith( issn ) then
            local k, m;
            if type( achieve ) == "string" then
                m = tonumber( achieve );
            else
                m = achieve;
            end
            if m == 8  or m == 13 then
                k = m;
            else
                k = issn.type;
            end
            r = ISSNformat( issn, k );
        end
    end
    if not r then
        r = mw.ustring.upper( mw.text.trim( attempt ) );
    end
    return r;
end -- URIutil.formatISSN()



function URIutil.formatLCCN( attempt, achieve )
    -- Standard or hyphen formatting of LCCN
    -- Precondition:
    --     attempt  -- string with presumable LCCN
    --     achieve   -- additional formatting desires, like "-"
    -- Postcondition:
    --     Returns  string with letters, digits and hyphens
    --              unmodified input if wrong
    local r = LCCNfactory( attempt );
    if r then
        r = LCCNformat( r, achieve );
    end
    return r;
end -- URIutil.formatLCCN()



function URIutil.isDNBvalid( attempt, also )
    -- Is this DNB (also GND, ZDB) formally correct (check digit)?
    -- Precondition:
    --     attempt  -- string with any presumable DNB code
    --     also     -- string or nil; optional requirement DMA GND SWD
    --                 currently not implemented
    --                 DMA starting with 3 and no hyphen
    --                 GND not DNB2011
    --                 SWD DNB2011 starting with 4 or 7 and no X check
    -- Postcondition:
    --     Returns  number of digits or 2011, if valid
    --              false if not correct, bad data or check digit wrong
    -- 2013-09-01
    local s = mw.text.trim( attempt );
    local j = s:find( "/", 5, true );
    local r = false;
    local dnb;
    if j then
        s = attempt:sub( 1,  j - 1 );
    end
    j = s:find( "-", 2, true );
    if j then
        if j > 3  and  j <= 8 then
            if s:match( "^[0-9]+-[0-9xX]$" ) then
                dnb = factory( s, #s );
            end
        end
    elseif #s > 7 then
        if s:match( "^[0-9]+[0-9xX]$" ) then
            dnb = factory( s, #s );
        end
    end
    if type( dnb ) == "table" then
        if j then
            if DNBfaith( dnb, true ) then
                r = 2011;
            end
        else
            if DNBfaith( dnb, false ) then
                r = dnb.type;
            end
        end
    end
    return r;
end -- URIutil.isDNBvalid()



function URIutil.isDOI( attempt )
    -- Is this a syntactically correct DOI?
    -- Precondition:
    --     attempt  -- string with presumable DOI code
    -- Postcondition:
    --     Returns  number of organization, if valid
    --              false if not correct, bad character or syntax
    local r = false;
    local k, s = attempt:match( "^%s*10%.([1-9][0-9]+)/(.+)%s*$" );
    if k then
        k = tonumber( k );
        if k >= 1000  and  k < 100000000 then
            local pc = "^[0-9A-Za-z%(%[<%./]"
                       .. "[%-0-9/A-Z%.a-z%(%)_%[%];:<>%+]*"
                       .. "[0-9A-Za-z%)%]>%+#]$"
            s = mw.uri.decode( mw.text.decode( s ), "PATH" );
            if s:match( pc ) then
                r = k;
            end
        end
    end
    return r;
end -- URIutil.isDOI()



function URIutil.isEscValid( attempt )
    -- Are bad percent escapings in attempt?
    -- Precondition:
    --     attempt  -- string with possible percent escapings
    -- Postcondition:
    --     Returns  string with violating sequence
    --              false if correct
    local i = 0;
    local r = false;
    local h, s;
    while i do
        i = attempt:find( "%", i, true );
        if i then
            s = attempt:sub( i + 1,  i + 2 );
            h = s:match( "%x%x" );
            if h then
                if h == "00" then
                    r = "%00";
                    break; -- while i
                end
                i = i + 2;
            else
                r = "%" .. s;
                break; -- while i
            end
        end
    end -- while i
    return r;
end -- URIutil.isEscValid()



function URIutil.isGTINvalid( attempt )
    -- Is this GTIN (EAN) formally correct (check digit)?
    -- Precondition:
    --     attempt  -- string with presumable GTIN
    -- Postcondition:
    --     Returns  GTIN length
    --              false if not correct, bad data or check digit wrong
    local r;
    local gtin = factory( attempt, false );
    if type( gtin ) == "table" then
        if gtin.type == 13 then
            if GTINfaith( gtin ) then
                r = gtin.type;
            end
        else
            r = false;
        end
    else
        r = false;
    end
    return r;
end -- URIutil.isGTINvalid()



function URIutil.isHandle( attempt )
    -- Is this a meaningful handle for handle.net?
    -- Precondition:
    --     attempt  -- string with presumable handle code
    -- Postcondition:
    --     Returns  number of primary authority, if valid
    --              false if not correct, bad character or syntax
    local r = attempt:match( "^%s*([^/%s]+)/%S+%s*$" );
    if r then
        local k = r:find( ".", 1, true );
        if k then
            if k == 1  or  r:match( "%.$" ) then
                r = false;
            else
                r = r:sub( 1,  k - 1 );
            end
        end
        if r then
            if r:match( "^[1-9][0-9]+$" ) then
                r = tonumber( r );
            else
                r = false;
            end
        end
    else
        r = false;
    end
    return r;
end -- URIutil.isHandle()



function URIutil.isISBN( attempt )
    -- Is this a syntactically correct ISBN?
    -- Precondition:
    --     attempt  -- string with presumable ISBN
    -- Postcondition:
    --     Returns
    --        1  -- 10 if 10 digits and hyphens; also X at end of ISBN-10
    --              13 if 13 digits and hyphens; beginning with bookland
    --              false if not an ISBN
    --        2  -- internal table, if (1)
    local r;
    local isbn = ISBNfactory( attempt );
    if type( isbn ) == "table" then
        r = isbn.type;
    else
        r = false;
    end
    return r, isbn;
end -- URIutil.isISBN()



function URIutil.isISBNvalid( attempt )
    -- Is this ISBN formally correct (check digit)?
    -- Precondition:
    --     attempt  -- string with presumable ISBN
    -- Postcondition:
    --     Returns
    --        1  -- 10 if 10 digits and hyphens; also X at end of ISBN-10
    --              13 if 13 digits and hyphens; beginning with bookland
    --              false if not correct, bad data or check digit wrong
    --        2  -- internal table, if (1)
    local r    = false;
    local isbn = ISBNfactory( attempt );
    if type( isbn ) == "table" then
        if ISBNfaith( isbn ) then
            r = isbn.type;
        end
    end
    return r, isbn;
end -- URIutil.isISBNvalid()



function URIutil.isISSNvalid( attempt )
    -- Is this ISSN formally correct (check digit)?
    -- Precondition:
    --     attempt  -- string with presumable ISSN
    -- Postcondition:
    --     Returns  8 if 8 digits and up to 1 hyphen; also X at end
    --              13 if 13 digits and hyphens; beginning with 977
    --              false if not correct, bad data or check digit wrong
    local r    = false;
    local issn = ISSNfactory( attempt );
    if type( issn ) == "table" then
        if ISSNfaith( issn ) then
            r = issn.type;
        end
    end
    return r;
end -- URIutil.isISSNvalid()



function URIutil.isLCCN( attempt, allow )
    -- Is this a syntactically correct LCCN?
    -- Precondition:
    --     attempt  -- string with presumable LCCN
    --     allow    -- false or string: "/"
    -- Postcondition:
    --     Returns  string with LCCN formatted aa9999-99999999
    --              false if not correct, bad data
    local r    = false;
    local lccn = LCCNfactory( attempt, allow );
    if lccn then
        r = LCCNformat( lccn, "-" );
    end
    return r;
end -- URIutil.isLCCN()



function URIutil.linkDOI( attempt )
    -- Retrieve bracketed titled external link on DOI resolver
    -- Precondition:
    --     attempt  -- string with presumable DOI
    -- Postcondition:
    --     Returns  external link, or false
    local r = URIutil.isDOI( attempt );
    if r then
        r = mw.text.decode( mw.text.trim( attempt ),  "PATH" );
        r = string.format( "[%s%s %s]",
                           "http://dx.doi.org/",
                           mw.uri.encode( r ),
                           mw.text.encode( r, "<>&%]" ) );
    end
    return r;
end -- URIutil.linkDOI()



function URIutil.linkHandle( attempt )
    -- Retrieve bracketed titled external link on handle resolver
    -- Precondition:
    --     attempt  -- string with presumable handle
    -- Postcondition:
    --     Returns  external link, or false
    local r = URIutil.isHandle( attempt );
    if r then
        r = mw.text.decode( mw.text.trim( attempt ),  "PATH" );
        r = string.format( "[%s%s %s]",
                           "http://hdl.handle.net/",
                           mw.uri.encode( r ),
                           mw.text.encode( r, "<>&%]" ) );
    end
    return r;
end -- URIutil.linkHandle()



function URIutil.linkISBN( attempt, allow, abbr, adhere )
    -- Retrieve bracketed titled wikilink on booksources page with "ISBN"
    -- Precondition:
    --     attempt  -- string with presumable ISBN
    --     allow    -- true: permit invalid check digit
    --     abbr     -- true or string: link ISBN abbreviation
    --     adhere   -- true: use &nbsp;  else: use simple space;
    -- Postcondition:
    --     Returns  link
    local lapsus;
    local source = mw.text.trim( attempt );
    local r      = "[[Special:Booksources/" .. source .. "|";
    local isbn   = ISBNfactory( source );
    if type( isbn ) == "table" then
        local lenient;
        if type( allow ) == "string" then
            lenient = ( allow ~= "0" );
        else
            lenient = allow;
        end
        if lenient then
            lapsus = false;
        else
            lapsus = ( not ISBNfaith( isbn ) );
        end
        r = r .. ISBNformat( attempt, isbn );
    else
        lapsus = true;
        r      = r .. source;
    end
    r = r .. "]]";
    if lapsus then
        r = "<span class='invalid-ISBN'>"
            .. r
            .. "</span><span class=\"error\">(?!?!)</span>";
    end
    if adhere then
        r = "&nbsp;" .. r;
    else
        r = " " .. r;
    end
    if abbr then
        local s;
        if type( abbr ) == "string" then
            s = abbr;
        else
            s = "International Standard Book Number";
        end
        r = string.format( "[[%s|ISBN]]%s", s, r );
    else
        r = "ISBN" .. r;
    end
    return r;
end -- URIutil.linkISBN()



function URIutil.linkISSN( attempt, allow, abbr, adhere )
    -- Retrieve bracketed titled external link on ISSN DB with "ISSN"
    -- Precondition:
    --     attempt  -- string with presumable ISSN
    --     allow    -- true: permit invalid check digit
    --     abbr     -- true or string: link ISSN abbreviation
    --     adhere   -- true: use &nbsp;  else: use simple space;
    -- Postcondition:
    --     Returns  link
    local issn   = ISSNfactory( attempt );
    local lapsus;
    local r;
    if type( issn ) == "table" then
        local lucky, cnf = pcall( mw.loadData, "Module:URIutil/config" );
        local lenient;
        if type( allow ) == "string" then
            lenient = ( allow ~= "0" );
        else
            lenient = allow;
        end
        if lenient then
            lapsus = false;
        else
            lapsus = ( not ISSNfaith( issn ) );
        end
        r = ISSNformat( issn, issn.type );
        if type( cnf ) == "table" then
            if type( cnf.issn ) == "string" then
                r = string.format( "[%s %s]",
                                   cnf.issn:gsub( "%$1", r ),
                                   r );
            end
        end
    else
        lapsus = true;
        r      = attempt;
    end
    if lapsus then
        r = "<span class='invalid-ISSN'>"
            .. r
            .. "</span><span class=\"error\">(?!?!)</span>";
    end
    if adhere then
        r = "&nbsp;" .. r;
    else
        r = " " .. r;
    end
    if abbr then
        local s;
        if type( abbr ) == "string" then
            s = abbr;
        else
            s = "International Standard Serial Number";
        end
        r = string.format( "[[%s|ISSN]]%s", s, r );
    else
        r = "ISSN" .. r;
    end
    return r;
end -- URIutil.linkISSN()



function URIutil.linkLCCN( attempt, achieve )
    -- Retrieve bracketed titled external LCCN permalink
    -- Precondition:
    --     attempt  -- string with presumable LCCN
    --     achieve  -- additional title formatting desires, like "-"
    -- Postcondition:
    --     Returns  link, or false if bad LCCN
    return LCCNforward( attempt, achieve );
end -- URIutil.linkLCCN()



function URIutil.mayDOI( attempt )
    -- Is this a syntactically correct DOI, or empty?
    -- Precondition:
    --     attempt  -- string with presumable DOI
    -- Postcondition:
    --     Returns  number of organization
    --              0  if empty
    --              false if not empty and not a DOI
    local r;
    if type( attempt ) == "string" then
        local s = mw.text.trim( attempt );
        if #s >= 10 then
            r = URIutil.isDOI( attempt );
        elseif #s == 0 then
            r = 0;
        else
            r = false;
        end
    else
        r = false;
    end
    return r;
end -- URIutil.mayDOI()



function URIutil.mayHandle( attempt )
    -- Is this a meaningful handle, or empty?
    -- Precondition:
    --     attempt  -- string with presumable handle
    -- Postcondition:
    --     Returns  number of organization
    --              0  if empty
    --              false if not empty and not a DOI
    local r;
    if type( attempt ) == "string" then
        local s = mw.text.trim( attempt );
        if #s > 5 then
            r = URIutil.isHandle( attempt );
        elseif #s == 0 then
            r = 0;
        else
            r = false;
        end
    else
        r = false;
    end
    return r;
end -- URIutil.mayHandle()



function URIutil.mayISBN( attempt )
    -- Is this a syntactically correct ISBN, or empty?
    -- Precondition:
    --     attempt  -- string with presumable ISBN
    -- Postcondition:
    --     Returns  10 if 10 digits and hyphens; also X at end of ISBN-10
    --              13 if 13 digits and hyphens; beginning with bookland
    --              0  if empty
    --              false if not empty and not an ISBN
    local r;
    if type( attempt ) == "string" then
        local s = mw.text.trim( attempt );
        if #s >= 10 then
            r = URIutil.isISBN( attempt );
        elseif #s == 0 then
            r = 0;
        else
            r = false;
        end
    else
        r = false;
    end
    return r;
end -- URIutil.mayISBN()



function URIutil.mayISSN( attempt )
    -- Is this a correct ISSN, or empty?
    -- Precondition:
    --     attempt  -- string with presumable ISSN
    -- Postcondition:
    --     Returns  8 if 8 digits and hyphens; also X at end
    --              13 if 13 digits and hyphens; beginning with issnland
    --              0  if empty
    --              false if not empty and not an ISSN
    local r;
    if type( attempt ) == "string" then
        local s = mw.text.trim( attempt );
        if #s >= 8 then
            r = URIutil.isISSNvalid( attempt );
        elseif #s == 0 then
            r = 0;
        else
            r = false;
        end
    else
        r = false;
    end
    return r;
end -- URIutil.mayISSN()



function URIutil.mayLCCN( attempt )
    -- Is this a syntactically correct LCCN?
    -- Precondition:
    --     attempt  -- string with presumable LCCN
    -- Postcondition:
    --     Returns  string with LCCN formatted aa9999-99999999
    --              0  if empty
    --              false if not recognized
    if type( attempt ) == "string" then
        local s = mw.text.trim( attempt );
        if  s == "" then
            r = 0;
        else
            r = URIutil.isLCCN( s );
        end
    else
        r = false;
    end
    return r;
end -- URIutil.mayLCCN()



function URIutil.mayURI( attempt, ascii )
    -- Is this a syntactically correct URI, or empty?
    -- Precondition:
    --     attempt  -- string with presumable URI
    --     ascii    -- limit to ASCII (no IRI)
    -- Postcondition:
    --     Returns  false if no problem
    --              string with violation
    local r = URIutil.isEscValid( attempt );
    if not r then
        local s = mw.text.trim( attempt );
        r = s:match( "%s(.+)$" );
        if not r then
            r = s:match( "#(.*)$" );
            if r then
                r = "&#35;" .. r;
            elseif ascii then
                local pat = mw.ustring.char( 128,45,255 );
                pat = "[" .. pat .. "].+$";
                r   = mw.ustring.match( s, pat );
            end
        end
    end
    return r;
end -- URIutil.mayURI()



function URIutil.mayURN( attempt )
    -- Is this a syntactically correct URN, or empty?
    -- Precondition:
    --     attempt  -- string with presumable URN
    -- Postcondition:
    --     Returns  false if no problem
    --              string with violation
    local r = URIutil.mayURI( attempt, true );
    if not r then
        local s = attempt:match( "^%s*[uU][rR][nN]:(.+)$" );
        if s then
            local ns, id = s:match( "^(%w+):(.+)$" );
            if ns then
                r = URNnamespace( ns:lower(), id );
            else
                r = s;
            end
        elseif mw.text.trim( attempt ) == "" then
            r = false;
        else
            r = "urn:";
        end
    end
    return r;
end -- URIutil.mayURN()



function URIutil.plainISBN( attempt )
    -- Format ISBN as digits (and 'X') only string
    -- Precondition:
    --     attempt  -- string with presumable ISBN
    -- Postcondition:
    --     Returns  string with 10 or 13 chars
    --              false if not empty and not an ISBN
    local r;
    local isbn = ISBNfactory( attempt );
    if type( isbn ) == "table" then
        r = ISBNflat( isbn );
    else
        r = false;
    end
    return r;
end -- URIutil.plainISBN()



function URIutil.uriDOI( attempt, anything, abbr )
    -- Retrieve linked URI on DOI resolver
    -- Precondition:
    --     attempt   -- string with presumable DOI
    --     anything  -- intentionally dummy parameter
    --     abbr      -- true or string: link doi: abbreviation
    local r = URIutil.linkDOI( attempt );
    if r then
        if abbr then
            local s;
            if type( abbr ) == "string" then
                s = abbr;
            else
                s = "Digital Object Identifier";
            end
            r = string.format( "[[%s|doi]]:%s", s, r );
        else
            r = "doi:" .. r;
        end
    end
    return r;
end -- URIutil.uriDOI()



function URIutil.uriHandle( attempt, anything, abbr )
    -- Retrieve linked URI on handle resolver
    -- Precondition:
    --     attempt   -- string with presumable handle
    --     anything  -- intentionally dummy parameter
    --     abbr      -- true or string: link hdl: abbreviation
    local r = URIutil.linkHandle( attempt );
    if r then
        local s;
        if type( abbr ) == "string" then
            s = abbr;
        end
        if s then
            r = string.format( "[[%s|hdl]]:%s", s, r );
        else
            r = "hdl:" .. r;
        end
    end
    return r;
end -- URIutil.uriHandle()



local Template = function ( frame, action )
    -- Retrieve library result for template access
    -- Precondition:
    --     frame   -- object
    --     action  -- string; function name
    -- Postcondition:
    --     Returns  appropriate string, or error message (development)
    local lucky, r = pcall( URIutil[ action ],
                            frame.args[ 1 ] or "",
                            frame.args[ 2 ],
                            faculty( frame.args.link, true ),
                            faculty( frame.args.nbsp, true ) );
    if lucky then
        if r then
            r = tostring( r );
        else
            r = "";
        end
    else
        r = "<span class=\"error\">" .. r .. "</span>";
    end
    return r;
end -- Template()



-- Provide template access and expose URIutil table to require()

local p = {};

function p.coreISSN( frame )
    return Template( frame, "coreISSN" );
end
function p.formatISBN( frame )
    return Template( frame, "formatISBN" );
end
function p.formatISSN( frame )
    return Template( frame, "formatISSN" );
end
function p.formatLCCN( frame )
    return Template( frame, "formatLCCN" );
end
function p.isDNBvalid( frame )
    return Template( frame, "isDNBvalid" );
end
function p.isDOI( frame )
    return Template( frame, "isDOI" );
end
function p.isEscValid( frame )
    return Template( frame, "isEscValid" );
end
function p.isGTINvalid( frame )
    return Template( frame, "isGTINvalid" );
end
function p.isHandle( frame )
    return Template( frame, "isHandle" );
end
function p.isISBN( frame )
    return Template( frame, "isISBN" );
end
function p.isISBNvalid( frame )
    return Template( frame, "isISBNvalid" );
end
function p.isISSNvalid( frame )
    return Template( frame, "isISSNvalid" );
end
function p.isLCCN( frame )
    return Template( frame, "isLCCN" );
end
function p.linkDOI( frame )
    return Template( frame, "linkDOI" );
end
function p.linkHandle( frame )
    return Template( frame, "linkHandle" );
end
function p.linkISBN( frame )
    return Template( frame, "linkISBN" );
end
function p.linkISSN( frame )
    return Template( frame, "linkISSN" );
end
function p.linkLCCN( frame )
    return Template( frame, "linkLCCN" );
end
function p.mayDOI( frame )
    return Template( frame, "mayDOI" );
end
function p.mayHandle( frame )
    return Template( frame, "mayHandle" );
end
function p.mayISBN( frame )
    return Template( frame, "mayISBN" );
end
function p.mayISSN( frame )
    return Template( frame, "mayISSN" );
end
function p.mayLCCN( frame )
    return Template( frame, "mayLCCN" );
end
function p.mayURI( frame )
    return Template( frame, "mayURI" );
end
function p.mayURN( frame )
    return Template( frame, "mayURN" );
end
function p.plainISBN( frame )
    return Template( frame, "plainISBN" );
end
function p.uriDOI( frame )
    return Template( frame, "uriDOI" );
end
function p.uriHandle( frame )
    return Template( frame, "uriHandle" );
end
function p.URIutil()
    return URIutil;
end

return p;