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

local format, insert = string.format, table.insert
local type, next = type, next
local lpegmatch = lpeg.match

-- we assume that the other otf stuff is loaded already

local trace_loading       = false  trackers.register("otf.loading", function(v) trace_loading = v end)
local report_otf          = logs.reporter("fonts","otf loading")

local fonts               = fonts
local otf                 = fonts.handlers.otf
local otffeatures         = fonts.constructors.newfeatures("otf")
local registerotffeature  = otffeatures.register
local setmetatableindex   = table.setmetatableindex

-- In the userdata interface we can not longer tweak the loaded font as
-- conveniently as before. For instance, instead of pushing extra data in
-- in the table using the original structure, we now have to operate on
-- the mkiv representation. And as the fontloader interface is modelled
-- after fontforge we cannot change that one too much either.

local types = {
    substitution = "gsub_single",
    ligature     = "gsub_ligature",
    alternate    = "gsub_alternate",
}

setmetatableindex(types, function(t,k) t[k] = k return k end) -- "key"

local everywhere = { ["*"] = { ["*"] = true } } -- or: { ["*"] = { "*" } }
local noflags    = { }

local function addfeature(data,feature,specifications)
    local descriptions = data.descriptions
    local resources    = data.resources
    local lookups      = resources.lookups
    local gsubfeatures = resources.features.gsub
    if gsubfeatures and gsubfeatures[feature] then
        -- already present
    else
        local sequences    = resources.sequences
        local fontfeatures = resources.features
        local unicodes     = resources.unicodes
        local lookuptypes  = resources.lookuptypes
        local splitter     = lpeg.splitter(" ",unicodes)
        local done = 0
        if not specifications[1] then
            -- so we accept a one entry specification
            specifications = { specifications }
        end
        -- subtables are tables themselves but we also accept flattened singular subtables
        for s=1,#specifications do
            local specification = specifications[s]
            local askedfeatures = specification.features or everywhere
            local subtables     = specification.subtables or { specification.data } or { }
            local featuretype   = types[specification.type or "substitution"]
            local featureflags  = specification.flags or noflags
            local added         = false
            local featurename   = format("ctx_%s_%s",feature,s)
            local st = { }
            for t=1,#subtables do
                local list = subtables[t]
                local full = format("%s_%s",featurename,t)
                st[t] = full
                if featuretype == "gsub_ligature" then
                    lookuptypes[full] = "ligature"
                    for code, ligature in next, list do
                        local unicode = tonumber(code) or unicodes[code]
                        local description = descriptions[unicode]
                        if description then
                            local slookups = description.slookups
                            if type(ligature) == "string" then
                                ligature = { lpegmatch(splitter,ligature) }
                            end
                            if slookups then
                                slookups[full] = ligature
                            else
                                description.slookups = { [full] = ligature }
                            end
                            done, added = done + 1, true
                        end
                    end
                elseif featuretype == "gsub_single" then
                    lookuptypes[full] = "substitution"
                    for code, replacement in next, list do
                        local unicode = tonumber(code) or unicodes[code]
                        local description = descriptions[unicode]
                        if description then
                            local slookups = description.slookups
                            replacement = tonumber(replacement) or unicodes[replacement]
                            if slookups then
                                slookups[full] = replacement
                            else
                                description.slookups = { [full] = replacement }
                            end
                            done, added = done + 1, true
                        end
                    end
                end
            end
            if added then
                -- script = { lang1, lang2, lang3 } or script = { lang1 = true, ... }
                for k, v in next, askedfeatures do
                    if v[1] then
                        askedfeatures[k] = table.tohash(v)
                    end
                end
                sequences[#sequences+1] = {
                    chain     = 0,
                    features  = { [feature] = askedfeatures },
                    flags     = featureflags,
                    name      = featurename,
                    subtables = st,
                    type      = featuretype,
                }
                -- register in metadata (merge as there can be a few)
                if not gsubfeatures then
                    gsubfeatures  = { }
                    fontfeatures.gsub = gsubfeatures
                end
                local k = gsubfeatures[feature]
                if not k then
                    k = { }
                    gsubfeatures[feature] = k
                end
                for script, languages in next, askedfeatures do
                    local kk = k[script]
                    if not kk then
                        kk = { }
                        k[script] = kk
                    end
                    for language, value in next, languages do
                        kk[language] = value
                    end
                end
            end
        end
        if done > 0 and trace_loading then
            report_otf("enhance: registering %s feature (%s glyphs affected)",feature,done)
        end
    end
end

otf.enhancers.addfeature = addfeature

local extrafeatures = { }

function otf.addfeature(name,specification)
    extrafeatures[name] = specification
end

local function enhance(data,filename,raw)
    for feature, specification in next, extrafeatures do
        addfeature(data,feature,specification)
    end
end

otf.enhancers.register("check extra features",enhance)

-- tlig --

local tlig = {
    endash        = "hyphen hyphen",
    emdash        = "hyphen hyphen hyphen",
 -- quotedblleft  = "quoteleft quoteleft",
 -- quotedblright = "quoteright quoteright",
 -- quotedblleft  = "grave grave",
 -- quotedblright = "quotesingle quotesingle",
 -- quotedblbase  = "comma comma",
}

local tlig_specification = {
    type     = "ligature",
    features = everywhere, -- { ["*"] = { ["*"] = true } },
    data     = tlig,
    flags    = noflags, -- { },
}

otf.addfeature("tlig",tlig_specification)

registerotffeature {
    name        = 'tlig',
    description = 'tex ligatures',
}

-- trep

local trep = {
 -- [0x0022] = 0x201D,
    [0x0027] = 0x2019,
 -- [0x0060] = 0x2018,
}

local trep_specification = {
    type      = "substitution",
    features  = everywhere, -- { ["*"] = { ["*"] = true } },
    data      = trep,
    flags     = noflags, -- { },
}

otf.addfeature("trep",trep_specification)

registerotffeature {
    name        = 'trep',
    description = 'tex replacements',
}

-- anum

local anum_arabic = {
    [0x0030] = 0x0660,
    [0x0031] = 0x0661,
    [0x0032] = 0x0662,
    [0x0033] = 0x0663,
    [0x0034] = 0x0664,
    [0x0035] = 0x0665,
    [0x0036] = 0x0666,
    [0x0037] = 0x0667,
    [0x0038] = 0x0668,
    [0x0039] = 0x0669,
}

local anum_persian = {
    [0x0030] = 0x06F0,
    [0x0031] = 0x06F1,
    [0x0032] = 0x06F2,
    [0x0033] = 0x06F3,
    [0x0034] = 0x06F4,
    [0x0035] = 0x06F5,
    [0x0036] = 0x06F6,
    [0x0037] = 0x06F7,
    [0x0038] = 0x06F8,
    [0x0039] = 0x06F9,
}

local anum_specification = {
    {
        type     = "substitution",
        features = { arab = { URD = true, dflt = true } },
        data     = anum_arabic,
        flags    = noflags, -- { },
    },
    {
        type     = "substitution",
        features = { arab = { URD = true } },
        data     = anum_persian,
        flags    = noflags, -- { },
    },
}

otf.addfeature("anum",anum_specification)

registerotffeature {
    name        = 'anum',
    description = 'arabic digits',
}