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

-- When a sequence of UTF characters enters the application, it may be
-- neccessary to collapse subsequences into their composed variant.
--
-- This module implements methods for collapsing and expanding UTF sequences. We
-- also provide means to deal with characters that are special to TeX as well as
-- 8-bit characters that need to end up in special kinds of output (for instance
-- PDF).
--
-- We implement these manipulations as filters. One can run multiple filters over a
-- string.
--
-- The old code has now been moved to char-obs.lua which we keep around for
-- educational purposes.

local next, type = next, type
local gsub, find = string.gsub, string.find
local concat, sortedhash, keys, sort = table.concat, table.sortedhash, table.keys, table.sort
local utfchar, utfbyte, utfcharacters = utf.char, utf.byte, utf.characters
local P, Cs, Cmt, Ct = lpeg.P, lpeg.Cs, lpeg.Cmt, lpeg.Ct

if not characters        then require("char-def") end
if not characters.blocks then require("char-ini") end

local lpegmatch             = lpeg.match
local lpegpatterns          = lpeg.patterns
local p_utf8character       = lpegpatterns.utf8character
local p_utf8byte            = lpegpatterns.utf8byte
local utfchartabletopattern = lpeg.utfchartabletopattern

local formatters            = string.formatters

local allocate              = utilities.storage.allocate or function() return { } end
local mark                  = utilities.storage.mark     or allocate

local charfromnumber        = characters.fromnumber

characters                  = characters or { }
local characters            = characters

local filters               = allocate()
characters.filters          = filters

local utffilters            = { }
characters.filters.utf      = utffilters

local data                  = characters.data

-- It only makes sense to collapse at runtime, since we don't expect source code to
-- depend on collapsing.

-- for the moment, will be entries in char-def.lua .. this is just a subset that for
-- typographic (font) reasons we want to have split ... if we decompose all, we get
-- problems with fonts

local decomposed = allocate {
    ["Ĳ"] = "IJ",
    ["ĳ"] = "ij",
    ["և"] = "եւ",
    ["ﬀ"] = "ff",
    ["ﬁ"] = "fi",
    ["ﬂ"] = "fl",
    ["ﬃ"] = "ffi",
    ["ﬄ"] = "ffl",
    ["ﬅ"] = "ſt",
    ["ﬆ"] = "st",
    ["ﬓ"] = "մն",
    ["ﬔ"] = "մե",
    ["ﬕ"] = "մի",
    ["ﬖ"] = "վն",
    ["ﬗ"] = "մխ",
}

characters.decomposed = decomposed

local graphemes = characters.graphemes
local collapsed = characters.collapsed
local combined  = characters.combined
local mathlists = characters.mathlists

if graphemes then

    mark(graphemes)
    mark(collapsed)
    mark(combined)
    mark(mathlists)

else

    graphemes = allocate()
    collapsed = allocate()
    combined  = allocate()
    mathlists = allocate()

    characters.graphemes = graphemes
    characters.collapsed = collapsed
    characters.combined  = combined
    characters.mathlists = mathlists

    local function backtrack(v,last,target)
        local vs = v.specials
        if vs and #vs == 3 then
            local kind = vs[1]
            if  kind == "char" or kind == "with" then
                local one = vs[2]
                local two = vs[3]
                local first  = utfchar(one)
                local second = utfchar(two) .. last
                collapsed[first..second] = target
                backtrack(data[one],second,target)
            end
        end
    end

    local function setlist(unicode,list,start,category)
        if list[start] ~= 0x20 then
            local t = mathlists
            for i=start,#list do
                local l = list[i]
                local f = t[l]
                if f then
                    t = f
                else
                    f = { }
                    t[l] = f
                    t = f
                end
            end
            t[category] = unicode
        end
    end

    local mlists = { }

    for unicode, v in next, data do
        local vs = v.specials
        if vs then
            local kind = vs[1]
            local size = #vs
            if kind == "char" or char == "with" then -- with added
                if size == 3 then
                    local one = vs[2]
                    local two = vs[3]
                    local first       = utfchar(one)
                    local second      = utfchar(two)
                    local combination = utfchar(unicode)
                    --
                    collapsed[first..second] = combination
                    backtrack(data[one],second,combination)
                    -- sort of obsolete:
                    local cgf = graphemes[first]
                    if not cgf then
                        cgf = { [second] = combination }
                        graphemes[first] = cgf
                    else
                        cgf[second] = combination
                    end
                end
                if size > 2 and (v.mathclass or v.mathspec) then
                    setlist(unicode,vs,2,"specials")
                end
            elseif kind == "with" then
                if size == 3 then
                    combined[utfchar(vs[2])..utfchar(vs[3])] = utfchar(unicode)
                end
            elseif kind == "compat" then
                if size == 3 then
                    combined[utfchar(vs[2])..utfchar(vs[3])] = utfchar(unicode)
                end
                if size > 2 and (v.mathclass or v.mathspec) then
                    setlist(unicode,vs,2,"specials")
                end
            end
        end
        local ml = v.mathlist
        if ml then
            mlists[unicode] = ml
        end
    end

    -- these win:

    for unicode, ml in next, mlists do
        setlist(unicode,ml,1,"mathlist")
    end

    mlists = nil

    if storage then
        storage.register("characters/graphemes", graphemes, "characters.graphemes")
        storage.register("characters/collapsed", collapsed, "characters.collapsed")
        storage.register("characters/combined",  combined,  "characters.combined")
        storage.register("characters/mathlists", mathlists, "characters.mathlists")
    end

end

function characters.initialize() end -- dummy

local skippable  = { }
local filesuffix = file.suffix

function utffilters.setskippable(suffix,value)
    if value == nil then
        value = true
    end
    if type(suffix) == "table" then
        for i=1,#suffix do
            skippable[suffix[i]] = value
        end
    else
        skippable[suffix] = value
    end
end

local p_collapse = nil -- so we can reset if needed

local function prepare()
    local tree = utfchartabletopattern(collapsed)
 -- p_collapse = Cs((tree/collapsed + p_utf8character)^0 * P(-1))
    p_collapse = Cs((tree/collapsed + p_utf8character)^0)
end

function utffilters.collapse(str,filename)
    if not p_collapse then
        prepare()
    end
    if not str or str == "" or #str == 1 then
        return str
    elseif filename and skippable[filesuffix(filename)] then -- we could hash the collapsables or do a quicker test
        return str
    else
        return lpegmatch(p_collapse,str) or str
    end
end

local p_combine = nil -- only for tex

local function prepare()
    local tree = utfchartabletopattern(combined)
    p_combine = Cs((tree/combined + p_utf8character)^0)
end

function utffilters.combine(str) -- not in files
    -- we could merge collapse into combine ... maybe
    if not p_combine then
        prepare()
    end
    if not str or str == "" or #str == 1 then
        return str
    else
        return lpegmatch(p_combine,str) or str
    end
end

local p_decompose = nil

local function prepare()
    local tree = utfchartabletopattern(decomposed)
    p_decompose = Cs((tree/decomposed + p_utf8character)^0 * P(-1))
end

function utffilters.decompose(str,filename) -- 3 to 4 times faster than the above
    if not p_decompose then
        prepare()
    end
    if str and str ~= "" and #str > 1 then
        return lpegmatch(p_decompose,str)
    end
    if not str or str == "" or #str < 2 then
        return str
    elseif filename and skippable[filesuffix(filename)] then
        return str
    else
        return lpegmatch(p_decompose,str) or str
    end
    return str
end

-- utffilters.addgrapheme(utfchar(318),'l','\string~')
-- utffilters.addgrapheme('c','a','b')

function utffilters.addgrapheme(result,first,second) -- can be U+ 0x string or utf or number
    local result = charfromnumber(result)
    local first  = charfromnumber(first)
    local second = charfromnumber(second)
    if not graphemes[first] then
        graphemes[first] = { [second] = result }
    else
        graphemes[first][second] = result
    end
    local pair = first .. second
    if not collapsed[pair] then
        collapsed[pair] = result
        p_composed = nil
    end
end

if interfaces then -- eventually this goes to char-ctx.lua

    interfaces.implement {
        name      = "addgrapheme",
        actions   = utffilters.addgrapheme,
        arguments = "3 strings",
    }

end

-- --

local p_reorder = nil

-- local sorter = function(a,b) return b[2] < a[2] end
--
-- local function swapper(s,p,t)
--     local old = { }
--     for i=1,#t do
--         old[i] = t[i][1]
--     end
--     old = concat(old)
--     sort(t,sorter)
--     for i=1,#t do
--         t[i] = t[i][1]
--     end
--     local new = concat(t)
--     if old ~= new then
--         print("reordered",old,"->",new)
--     end
--     return p, new
-- end

-- -- the next one into stable for similar weights

local sorter = function(a,b)
    return b[2] < a[2]
end

local function swapper(s,p,t)
    sort(t,sorter)
    for i=1,#t do
        t[i] = t[i][1]
    end
    return p, concat(t)
end

-- -- the next one keeps similar weights in the original order
--
-- local sorter = function(a,b)
--     local b2, a2 = b[2], a[2]
--     if a2 == b2 then
--         return b[3] > a[3]
--     else
--         return b2 < a2
--     end
-- end
--
-- local function swapper(s,p,t)
--     for i=1,#t do
--         t[i][3] = i
--     end
--     sort(t,sorter)
--     for i=1,#t do
--         t[i] = t[i][1]
--     end
--     return p, concat(t)
-- end

-- at some point exceptions will become an option, for now it's an experiment
-- to overcome bugs (that have become features) in unicode .. or we might decide
-- for an extra ordering key in char-def that takes precedence over combining

local exceptions = {
    -- frozen unicode bug
    ["َّ"] = "َّ", -- U+64E .. U+651 => U+651 .. U+64E
}

local function prepare()
    local hash = { }
    for k, v in sortedhash(characters.data) do
        local combining = v.combining -- v.ordering or v.combining
        if combining then
            local u = utfchar(k)
            hash[u] = { u, combining, 0 } -- slot 3 can be used in sort
        end
    end
    local e = utfchartabletopattern(exceptions)
    local p = utfchartabletopattern(hash)
    p_reorder = Cs((e/exceptions + Cmt(Ct((p/hash)^2),swapper) + p_utf8character)^0) * P(-1)
end

function utffilters.reorder(str,filename)
    if not p_reorder then
        prepare()
    end
    if not str or str == "" or #str < 2 then
        return str
    elseif filename and skippable[filesuffix(filename)] then
        return str
    else
        return lpegmatch(p_reorder,str) or str
    end
    return str
end

-- local collapse   = utffilters.collapse
-- local decompose  = utffilters.decompose
-- local reorder    = utffilters.reorder
--
-- local c1, c2, c3 = "a", "̂", "̃"
-- local r2, r3 = "â", "ẫ"
-- local l1 = "ﬄ"
--
-- local str  = c1..c2..c3 .. " " .. c1..c2 .. " " .. l1
-- local res  = r3 .. " " .. r2 .. " " .. "ffl"
--
-- local text  = io.loaddata("t:/sources/tufte.tex")
--
-- local function test(n)
--     local data = text .. string.rep(str,100) .. text
--     local okay = text .. string.rep(res,100) .. text
--     local t = os.clock()
--     for i=1,10000 do
--         collapse(data)
--         decompose(data)
--      -- reorder(data)
--     end
--     print(os.clock()-t,decompose(collapse(data))==okay,decompose(collapse(str)))
-- end
--
-- test(050)
-- test(150)
--
-- local old = "foo" .. string.char(0xE1) .. "bar"
-- local new = collapse(old)
-- print(old,new)

-- local one_old = "فَأَصَّدَّقَ دَّ" local one_new = utffilters.reorder(one_old)
-- local two_old = "فَأَصَّدَّقَ دَّ" local two_new = utffilters.reorder(two_old)
--
-- print(one_old,two_old,one_old==two_old,false)
-- print(one_new,two_new,one_new==two_new,true)
--
-- local test = "foo" .. utf.reverse("ؚ" .. "ً" .. "ٌ" .. "ٍ" .. "َ" .. "ُ" .. "ِ" .. "ّ" .. "ْ" ) .. "bar"
-- local done = utffilters.reorder(test)
--
-- print(test,done,test==done,false)

local f_default     = formatters["[%U] "]
local f_description = formatters["[%s] "]

local function convert(n)
    local d = data[n]
    d = d and d.description
    if d then
        return f_description(d)
    else
        return f_default(n)
    end
end

local pattern = Cs((p_utf8byte / convert)^1)

function utffilters.verbose(data)
    return data and lpegmatch(pattern,data) or ""
end

return characters
