if not modules then modules = { } end modules ['util-tab'] = {
    version   = 1.001,
    comment   = "companion to luat-lib.mkiv",
    author    = "Hans Hagen, PRAGMA-ADE, Hasselt NL",
    copyright = "PRAGMA ADE / ConTeXt Development Team",
    license   = "see context related readme files"
}

utilities        = utilities or {}
utilities.tables = utilities.tables or { }
local tables     = utilities.tables

local format, gmatch, gsub, sub = string.format, string.gmatch, string.gsub, string.sub
local concat, insert, remove = table.concat, table.insert, table.remove
local setmetatable, getmetatable, tonumber, tostring = setmetatable, getmetatable, tonumber, tostring
local type, next, rawset, tonumber, tostring, load, select = type, next, rawset, tonumber, tostring, load, select
local lpegmatch, P, Cs, Cc = lpeg.match, lpeg.P, lpeg.Cs, lpeg.Cc
local sortedkeys, sortedpairs = table.sortedkeys, table.sortedpairs
local formatters = string.formatters
local utftoeight = utf.toeight

local splitter = lpeg.tsplitat(".")

function utilities.tables.definetable(target,nofirst,nolast) -- defines undefined tables
    local composed, t = nil, {  }
    local snippets = lpegmatch(splitter,target)
    for i=1,#snippets - (nolast and 1 or 0) do
        local name = snippets[i]
        if composed then
            composed = composed .. "." .. name
                t[#t+1] = formatters["if not %s then %s = { } end"](composed,composed)
        else
            composed = name
            if not nofirst then
                t[#t+1] = formatters["%s = %s or { }"](composed,composed)
            end
        end
    end
    if composed then
        if nolast then
            composed = composed .. "." .. snippets[#snippets]
        end
        return concat(t,"\n"), composed -- could be shortcut
    else
        return "", target
    end
end

-- local t = tables.definedtable("a","b","c","d")

function tables.definedtable(...)
    local t = _G
    for i=1,select("#",...) do
        local li = select(i,...)
        local tl = t[li]
        if not tl then
            tl = { }
            t[li] = tl
        end
        t = tl
    end
    return t
end

function tables.accesstable(target,root)
    local t = root or _G
    for name in gmatch(target,"([^%.]+)") do
        t = t[name]
        if not t then
            return
        end
    end
    return t
end

function tables.migratetable(target,v,root)
    local t = root or _G
    local names = lpegmatch(splitter,target)
    for i=1,#names-1 do
        local name = names[i]
        t[name] = t[name] or { }
        t = t[name]
        if not t then
            return
        end
    end
    t[names[#names]] = v
end

function tables.removevalue(t,value) -- todo: n
    if value then
        for i=1,#t do
            if t[i] == value then
                remove(t,i)
                -- remove all, so no: return
            end
        end
    end
end

function tables.replacevalue(t,oldvalue,newvalue)
    if oldvalue and newvalue then
        for i=1,#t do
            if t[i] == oldvalue then
                t[i] = newvalue
                -- replace all, so no: return
            end
        end
    end
end

function tables.insertbeforevalue(t,value,extra)
    for i=1,#t do
        if t[i] == extra then
            remove(t,i)
        end
    end
    for i=1,#t do
        if t[i] == value then
            insert(t,i,extra)
            return
        end
    end
    insert(t,1,extra)
end

function tables.insertaftervalue(t,value,extra)
    for i=1,#t do
        if t[i] == extra then
            remove(t,i)
        end
    end
    for i=1,#t do
        if t[i] == value then
            insert(t,i+1,extra)
            return
        end
    end
    insert(t,#t+1,extra)
end

-- experimental

local escape = Cs(Cc('"') * ((P('"')/'""' + P(1))^0) * Cc('"'))

function table.tocsv(t,specification)
    if t and #t > 0 then
        local result = { }
        local r = { }
        specification = specification or { }
        local fields = specification.fields
        if type(fields) ~= "string" then
            fields = sortedkeys(t[1])
        end
        local separator = specification.separator or ","
        if specification.preamble == true then
            for f=1,#fields do
                r[f] = lpegmatch(escape,tostring(fields[f]))
            end
            result[1] = concat(r,separator)
        end
        for i=1,#t do
            local ti = t[i]
            for f=1,#fields do
                local field = ti[fields[f]]
                if type(field) == "string" then
                    r[f] = lpegmatch(escape,field)
                else
                    r[f] = tostring(field)
                end
            end
            result[#result+1] = concat(r,separator)
        end
        return concat(result,"\n")
    else
        return ""
    end
end

-- local nspaces = utilities.strings.newrepeater(" ")
-- local escape  = Cs((P("<")/"&lt;" + P(">")/"&gt;" + P("&")/"&amp;" + P(1))^0)
--
-- local function toxml(t,d,result,step)
--     for k, v in sortedpairs(t) do
--         local s = nspaces[d]
--         local tk = type(k)
--         local tv = type(v)
--         if tv == "table" then
--             if tk == "number" then
--                 result[#result+1] = format("%s<entry n='%s'>",s,k)
--                 toxml(v,d+step,result,step)
--                 result[#result+1] = format("%s</entry>",s,k)
--             else
--                 result[#result+1] = format("%s<%s>",s,k)
--                 toxml(v,d+step,result,step)
--                 result[#result+1] = format("%s</%s>",s,k)
--             end
--         elseif tv == "string" then
--             if tk == "number" then
--                 result[#result+1] = format("%s<entry n='%s'>%s</entry>",s,k,lpegmatch(escape,v),k)
--             else
--                 result[#result+1] = format("%s<%s>%s</%s>",s,k,lpegmatch(escape,v),k)
--             end
--         elseif tk == "number" then
--             result[#result+1] = format("%s<entry n='%s'>%s</entry>",s,k,tostring(v),k)
--         else
--             result[#result+1] = format("%s<%s>%s</%s>",s,k,tostring(v),k)
--         end
--     end
-- end
--
-- much faster

local nspaces = utilities.strings.newrepeater(" ")

local function toxml(t,d,result,step)
    for k, v in sortedpairs(t) do
        local s = nspaces[d] -- inlining this is somewhat faster but gives more formatters
        local tk = type(k)
        local tv = type(v)
        if tv == "table" then
            if tk == "number" then
                result[#result+1] = formatters["%s<entry n='%s'>"](s,k)
                toxml(v,d+step,result,step)
                result[#result+1] = formatters["%s</entry>"](s,k)
            else
                result[#result+1] = formatters["%s<%s>"](s,k)
                toxml(v,d+step,result,step)
                result[#result+1] = formatters["%s</%s>"](s,k)
            end
        elseif tv == "string" then
            if tk == "number" then
                result[#result+1] = formatters["%s<entry n='%s'>%!xml!</entry>"](s,k,v,k)
            else
                result[#result+1] = formatters["%s<%s>%!xml!</%s>"](s,k,v,k)
            end
        elseif tk == "number" then
            result[#result+1] = formatters["%s<entry n='%s'>%S</entry>"](s,k,v,k)
        else
            result[#result+1] = formatters["%s<%s>%S</%s>"](s,k,v,k)
        end
    end
end

-- function table.toxml(t,name,nobanner,indent,spaces)
--     local noroot = name == false
--     local result = (nobanner or noroot) and { } or { "<?xml version='1.0' standalone='yes' ?>" }
--     local indent = rep(" ",indent or 0)
--     local spaces = rep(" ",spaces or 1)
--     if noroot then
--         toxml( t, inndent, result, spaces)
--     else
--         toxml( { [name or "root"] = t }, indent, result, spaces)
--     end
--     return concat(result,"\n")
-- end

function table.toxml(t,specification)
    specification = specification or { }
    local name   = specification.name
    local noroot = name == false
    local result = (specification.nobanner or noroot) and { } or { "<?xml version='1.0' standalone='yes' ?>" }
    local indent = specification.indent or 0
    local spaces = specification.spaces or 1
    if noroot then
        toxml( t, indent, result, spaces)
    else
        toxml( { [name or "data"] = t }, indent, result, spaces)
    end
    return concat(result,"\n")
end

-- also experimental

-- encapsulate(table,utilities.tables)
-- encapsulate(table,utilities.tables,true)
-- encapsulate(table,true)

function tables.encapsulate(core,capsule,protect)
    if type(capsule) ~= "table" then
        protect = true
        capsule = { }
    end
    for key, value in next, core do
        if capsule[key] then
            print(formatters["\ninvalid %s %a in %a"]("inheritance",key,core))
            os.exit()
        else
            capsule[key] = value
        end
    end
    if protect then
        for key, value in next, core do
            core[key] = nil
        end
        setmetatable(core, {
            __index = capsule,
            __newindex = function(t,key,value)
                if capsule[key] then
                    print(formatters["\ninvalid %s %a' in %a"]("overload",key,core))
                    os.exit()
                else
                    rawset(t,key,value)
                end
            end
        } )
    end
end

-- best keep [%q] keys (as we have some in older applications i.e. saving user data

local f_hashed_string   = formatters["[%q]=%q,"]
local f_hashed_number   = formatters["[%q]=%s,"]
local f_hashed_boolean  = formatters["[%q]=%l,"]
local f_hashed_table    = formatters["[%q]="]

local f_indexed_string  = formatters["[%s]=%q,"]
local f_indexed_number  = formatters["[%s]=%s,"]
local f_indexed_boolean = formatters["[%s]=%l,"]
local f_indexed_table   = formatters["[%s]="]

local f_ordered_string  = formatters["%q,"]
local f_ordered_number  = formatters["%s,"]
local f_ordered_boolean = formatters["%l,"]

function table.fastserialize(t,prefix)

    -- prefix should contain the =
    -- not sorted
    -- only number and string indices (currently)

    local r = { type(prefix) == "string" and prefix or "return" }
    local m = 1

    local function fastserialize(t,outer) -- no mixes
        local n = #t
        m = m + 1
        r[m] = "{"
        if n > 0 then
            for i=0,n do
                local v  = t[i]
                local tv = type(v)
                if tv == "string" then
                    m = m + 1 r[m] = f_ordered_string(v)
                elseif tv == "number" then
                    m = m + 1 r[m] = f_ordered_number(v)
                elseif tv == "table" then
                    fastserialize(v)
                elseif tv == "boolean" then
                    m = m + 1 r[m] = f_ordered_boolean(v)
                end
            end
        end
        for k, v in next, t do
            local tk = type(k)
            if tk == "number" then
                if k > n or k < 0 then
                    local tv = type(v)
                    if tv == "string" then
                        m = m + 1 r[m] = f_indexed_string(k,v)
                    elseif tv == "number" then
                        m = m + 1 r[m] = f_indexed_number(k,v)
                    elseif tv == "table" then
                        m = m + 1 r[m] = f_indexed_table(k)
                        fastserialize(v)
                    elseif tv == "boolean" then
                        m = m + 1 r[m] = f_indexed_boolean(k,v)
                    end
                end
            else
                local tv = type(v)
                if tv == "string" then
                    m = m + 1 r[m] = f_hashed_string(k,v)
                elseif tv == "number" then
                    m = m + 1 r[m] = f_hashed_number(k,v)
                elseif tv == "table" then
                    m = m + 1 r[m] = f_hashed_table(k)
                    fastserialize(v)
                elseif tv == "boolean" then
                    m = m + 1 r[m] = f_hashed_boolean(k,v)
                end
            end
        end
        m = m + 1
        if outer then
            r[m] = "}"
        else
            r[m] = "},"
        end
        return r
    end
    return concat(fastserialize(t,true))
end

function table.deserialize(str)
    if not str or str == "" then
        return
    end
    local code = load(str)
    if not code then
        return
    end
    code = code()
    if not code then
        return
    end
    return code
end

-- inspect(table.fastserialize { a = 1, b = { 4, { 5, 6 } }, c = { d = 7, e = 'f"g\nh' } })

function table.load(filename,loader)
    if filename then
        local t = (loader or io.loaddata)(filename)
        if t and t ~= "" then
            local t = utftoeight(t)
            t = load(t)
            if type(t) == "function" then
                t = t()
                if type(t) == "table" then
                    return t
                end
            end
        end
    end
end

function table.save(filename,t,n,...)
    io.savedata(filename,table.serialize(t,n == nil and true or n,...)) -- no frozen table.serialize
end

local f_key_value    = formatters["%s=%q"]
local f_add_table    = formatters[" {%t},\n"]
local f_return_table = formatters["return {\n%t}"]

local function slowdrop(t) -- maybe less memory (intermediate concat)
    local r = { }
    local l = { }
    for i=1,#t do
        local ti = t[i]
        local j = 0
        for k, v in next, ti do
            j = j + 1
            l[j] = f_key_value(k,v)
        end
        r[i] = f_add_table(l)
    end
    return f_return_table(r)
end

local function fastdrop(t)
    local r = { "return {\n" }
    local m = 1
    for i=1,#t do
        local ti = t[i]
        m = m + 1 r[m] = " {"
        for k, v in next, ti do
            m = m + 1 r[m] = f_key_value(k,v)
        end
        m = m + 1 r[m] = "},\n"
    end
    m = m + 1
    r[m] = "}"
    return concat(r)
end

function table.drop(t,slow) -- only { { a=2 }, {a=3} } -- for special cases
    if #t == 0 then
        return "return { }"
    elseif slow == true then
        return slowdrop(t) -- less memory
    else
        return fastdrop(t) -- some 15% faster
    end
end

-- inspect(table.drop({ { a=2 }, {a=3} }))
-- inspect(table.drop({ { a=2 }, {a=3} },true))

function table.autokey(t,k)
    local v = { }
    t[k] = v
    return v
end

local selfmapper = { __index = function(t,k) t[k] = k return k end }

function table.twowaymapper(t)
    if not t then
        t = { }
    else
        for i=0,#t do
            local ti = t[i]       -- t[1]     = "one"
            if ti then
                local i = tostring(i)
                t[i]    = ti      -- t["1"]   = "one"
                t[ti]   = i       -- t["one"] = "1"
            end
        end
        t[""] = t[0] or ""
    end
 -- setmetatableindex(t,"key")
    setmetatable(t,selfmapper)
    return t
end

-- The next version is somewhat faster, although in practice one will seldom
-- serialize a lot using this one. Often the above variants are more efficient.
-- If we would really need this a lot, we could hash q keys, or just not used
-- indented code.

-- char-def.lua : 0.53 -> 0.38
-- husayni.tma  : 0.28 -> 0.19

local f_start_key_idx     = formatters["%w{"]
local f_start_key_num     = formatters["%w[%s]={"]
local f_start_key_str     = formatters["%w[%q]={"]
local f_start_key_boo     = formatters["%w[%l]={"]
local f_start_key_nop     = formatters["%w{"]

local f_stop              = formatters["%w},"]

local f_key_num_value_num = formatters["%w[%s]=%s,"]
local f_key_str_value_num = formatters["%w[%q]=%s,"]
local f_key_boo_value_num = formatters["%w[%l]=%s,"]

local f_key_num_value_str = formatters["%w[%s]=%q,"]
local f_key_str_value_str = formatters["%w[%q]=%q,"]
local f_key_boo_value_str = formatters["%w[%l]=%q,"]

local f_key_num_value_boo = formatters["%w[%s]=%l,"]
local f_key_str_value_boo = formatters["%w[%q]=%l,"]
local f_key_boo_value_boo = formatters["%w[%l]=%l,"]

local f_key_num_value_not = formatters["%w[%s]={},"]
local f_key_str_value_not = formatters["%w[%q]={},"]
local f_key_boo_value_not = formatters["%w[%l]={},"]

local f_key_num_value_seq = formatters["%w[%s]={ %, t },"]
local f_key_str_value_seq = formatters["%w[%q]={ %, t },"]
local f_key_boo_value_seq = formatters["%w[%l]={ %, t },"]

local f_val_num           = formatters["%w%s,"]
local f_val_str           = formatters["%w%q,"]
local f_val_boo           = formatters["%w%l,"]
local f_val_not           = formatters["%w{},"]
local f_val_seq           = formatters["%w{ %, t },"]

local f_table_return      = formatters["return {"]
local f_table_name        = formatters["%s={"]
local f_table_direct      = formatters["{"]
local f_table_entry       = formatters["[%q]={"]
local f_table_finish      = formatters["}"]

----- f_string            = formatters["%q"]

local spaces = utilities.strings.newrepeater(" ")

local serialize = table.serialize -- the extensive one, the one we started with

-- there is still room for optimization: index run, key run, but i need to check with the
-- latest lua for the value of #n (with holes) .. anyway for tracing purposes we want
-- indices / keys being sorted, so it will never be real fast

function table.serialize(root,name,specification)

    if type(specification) == "table" then
        return serialize(root,name,specification) -- the original one
    end

    local t -- = { }
    local n = 1

    local function simple_table(t)
        if #t > 0 then
            local n = 0
            for _, v in next, t do
                n = n + 1
                if type(v) == "table" then
                    return nil
                end
            end
            if n == #t then
                local tt = { }
                local nt = 0
                for i=1,#t do
                    local v = t[i]
                    local tv = type(v)
                    nt = nt + 1
                    if tv == "number" then
                        tt[nt] = v
                    elseif tv == "string" then
                        tt[nt] = format("%q",v) -- f_string(v)
                    elseif tv == "boolean" then
                        tt[nt] = v and "true" or "false"
                    else
                        return nil
                    end
                end
                return tt
            end
        end
        return nil
    end

    local function do_serialize(root,name,depth,level,indexed)
        if level > 0 then
            n = n + 1
            if indexed then
                t[n] = f_start_key_idx(depth)
            else
                local tn = type(name)
                if tn == "number" then
                    t[n] = f_start_key_num(depth,name)
                elseif tn == "string" then
                    t[n] = f_start_key_str(depth,name)
                elseif tn == "boolean" then
                    t[n] = f_start_key_boo(depth,name)
                else
                    t[n] = f_start_key_nop(depth)
                end
            end
            depth = depth + 1
        end
        -- we could check for k (index) being number (cardinal)
        if root and next(root) ~= nil then
            local first = nil
            local last  = 0
            last = #root
            for k=1,last do
                if root[k] == nil then
                    last = k - 1
                    break
                end
            end
            if last > 0 then
                first = 1
            end
            local sk = sortedkeys(root) -- inline fast version?
            for i=1,#sk do
                local k  = sk[i]
                local v  = root[k]
                local tv = type(v)
                local tk = type(k)
                if first and tk == "number" and k >= first and k <= last then
                    if tv == "number" then
                        n = n + 1 t[n] = f_val_num(depth,v)
                    elseif tv == "string" then
                        n = n + 1 t[n] = f_val_str(depth,v)
                    elseif tv == "table" then
                        if next(v) == nil then
                            n = n + 1 t[n] = f_val_not(depth)
                        else
                            local st = simple_table(v)
                            if st then
                                n = n + 1 t[n] = f_val_seq(depth,st)
                            else
                                do_serialize(v,k,depth,level+1,true)
                            end
                        end
                    elseif tv == "boolean" then
                        n = n + 1 t[n] = f_val_boo(depth,v)
                    end
                elseif tv == "number" then
                    if tk == "number" then
                        n = n + 1 t[n] = f_key_num_value_num(depth,k,v)
                    elseif tk == "string" then
                        n = n + 1 t[n] = f_key_str_value_num(depth,k,v)
                    elseif tk == "boolean" then
                        n = n + 1 t[n] = f_key_boo_value_num(depth,k,v)
                    end
                elseif tv == "string" then
                    if tk == "number" then
                        n = n + 1 t[n] = f_key_num_value_str(depth,k,v)
                    elseif tk == "string" then
                        n = n + 1 t[n] = f_key_str_value_str(depth,k,v)
                    elseif tk == "boolean" then
                        n = n + 1 t[n] = f_key_boo_value_str(depth,k,v)
                    end
                elseif tv == "table" then
                    if next(v) == nil then
                        if tk == "number" then
                            n = n + 1 t[n] = f_key_num_value_not(depth,k,v)
                        elseif tk == "string" then
                            n = n + 1 t[n] = f_key_str_value_not(depth,k,v)
                        elseif tk == "boolean" then
                            n = n + 1 t[n] = f_key_boo_value_not(depth,k,v)
                        end
                    else
                        local st = simple_table(v)
                        if not st then
                            do_serialize(v,k,depth,level+1)
                        elseif tk == "number" then
                            n = n + 1 t[n] = f_key_num_value_seq(depth,k,st)
                        elseif tk == "string" then
                            n = n + 1 t[n] = f_key_str_value_seq(depth,k,st)
                        elseif tk == "boolean" then
                            n = n + 1 t[n] = f_key_boo_value_seq(depth,k,st)
                        end
                    end
                elseif tv == "boolean" then
                    if tk == "number" then
                        n = n + 1 t[n] = f_key_num_value_boo(depth,k,v)
                    elseif tk == "string" then
                        n = n + 1 t[n] = f_key_str_value_boo(depth,k,v)
                    elseif tk == "boolean" then
                        n = n + 1 t[n] = f_key_boo_value_boo(depth,k,v)
                    end
                end
            end
        end
        if level > 0 then
            n = n + 1 t[n] = f_stop(depth-1)
        end
    end

    local tname = type(name)

    if tname == "string" then
        if name == "return" then
            t = { f_table_return() }
        else
            t = { f_table_name(name) }
        end
    elseif tname == "number" then
        t = { f_table_entry(name) }
    elseif tname == "boolean" then
        if name then
            t = { f_table_return() }
        else
            t = { f_table_direct() }
        end
    else
        t = { f_table_name("t") }
    end

    if root then
        -- The dummy access will initialize a table that has a delayed initialization
        -- using a metatable. (maybe explicitly test for metatable)
        if getmetatable(root) then -- todo: make this an option, maybe even per subtable
            local dummy = root._w_h_a_t_e_v_e_r_
            root._w_h_a_t_e_v_e_r_ = nil
        end
        -- Let's forget about empty tables.
        if next(root) ~= nil then
            do_serialize(root,name,1,0)
        end
    end
    n = n + 1
    t[n] = f_table_finish()
    return concat(t,"\n")
end