if not modules then modules = { } end modules ["extralibs"] = {
    version   = "2.4",
    comment   = "companion to luaotfload.lua",
    author    = "Hans Hagen, Philipp Gesang",
    copyright = "PRAGMA ADE / ConTeXt Development Team",
    license   = "GPL v.2.0",
}

-- extralibs: set up an emulation layer to load additional Context
--            libraries

--===================================================================--
---                             PREPARE
--===================================================================--

local getmetatable    = getmetatable
local require         = require
local select          = select
local setmetatable    = setmetatable
local tonumber        = tonumber

local texattribute    = tex.attribute

local new_node        = node.new
local copy_node       = node.copy
local otffeatures     = fonts.constructors.newfeatures "otf"

-----------------------------------------------------------------------
--- namespace
-----------------------------------------------------------------------

--- The “typesetters” namespace isn’t bad at all; there is no need
--- to remove it after loading.

typesetters              = typesetters or { }
local typesetters        = typesetters
typesetters.kerns        = typesetters.kerns or { }
local kerns              = typesetters.kerns
kerns.mapping            = kerns.mapping or { }
kerns.factors            = kerns.factors or { }

local kern_callback      = "typesetters.kerncharacters"

typesetters.kernfont     = typesetters.kernfont or { }
local kernfont           = typesetters.kernfont

-----------------------------------------------------------------------
--- node-ini
-----------------------------------------------------------------------

nodes              = nodes or { } --- should be present with luaotfload
local bothways     = function (t) return table.swapped (t, t) end

local kerncodes = bothways({
  [0] = "fontkern",
  [1] = "userkern",
  [2] = "accentkern",
})

kerncodes.kerning = kerncodes.fontkern --- idiosyncrasy

nodes.kerncodes = kerncodes

nodes.skipcodes = bothways({
  [  0] = "userskip",
  [  1] = "lineskip",
  [  2] = "baselineskip",
  [  3] = "parskip",
  [  4] = "abovedisplayskip",
  [  5] = "belowdisplayskip",
  [  6] = "abovedisplayshortskip",
  [  7] = "belowdisplayshortskip",
  [  8] = "leftskip",
  [  9] = "rightskip",
  [ 10] = "topskip",
  [ 11] = "splittopskip",
  [ 12] = "tabskip",
  [ 13] = "spaceskip",
  [ 14] = "xspaceskip",
  [ 15] = "parfillskip",
  [ 16] = "thinmuskip",
  [ 17] = "medmuskip",
  [ 18] = "thickmuskip",
  [100] = "leaders",
  [101] = "cleaders",
  [102] = "xleaders",
  [103] = "gleaders",
})

-----------------------------------------------------------------------
--- node-res
-----------------------------------------------------------------------

nodes.pool        = nodes.pool or { }
local pool        = nodes.pool

local kern        = new_node("kern", nodes.kerncodes.userkern)
local glue_spec   = new_node "glue_spec"

pool.kern = function (k)
  local n = copy_node(kern)
  n.kern = k
  return n
end

pool.gluespec = function (width, stretch, shrink, 
                          stretch_order, shrink_order)
  local s = copy_node(glue_spec)
  if width         then s.width         = width         end
  if stretch       then s.stretch       = stretch       end
  if shrink        then s.shrink        = shrink        end
  if stretch_order then s.stretch_order = stretch_order end
  if shrink_order  then s.shrink_order  = shrink_order  end
  return s
end

pool.glue = function (width, stretch, shrink,
                      stretch_order, shrink_order)
  local n = new_node"glue"
  if not width then
    -- no spec
  elseif width == false or tonumber(width) then
    local s = copy_node(glue_spec)
    if width         then s.width         = width         end
    if stretch       then s.stretch       = stretch       end
    if shrink        then s.shrink        = shrink        end
    if stretch_order then s.stretch_order = stretch_order end
    if shrink_order  then s.shrink_order  = shrink_order  end
    n.spec = s
  else
    -- shared
    n.spec = copy_node(width)
  end
  return n
end

-----------------------------------------------------------------------
--- font-hsh
-----------------------------------------------------------------------
--- some initialization resembling font-hsh
local fonthashes         = fonts.hashes
local identifiers        = fonthashes.identifiers --- was: fontdata
local chardata           = fonthashes.characters
local quaddata           = fonthashes.quads
local markdata           = fonthashes.marks
local parameters         = fonthashes.parameters

--- ('a, 'a) hash -> (('a, 'a) hash -> 'a -> 'a) -> ('a, 'a) hash
local setmetatableindex = function (t, f)
  local mt = getmetatable(t)
  if mt then
    mt.__index = f
  else
    setmetatable(t, { __index = f })
  end
  return t
end

if not parameters then
  parameters = { }
  setmetatableindex(parameters, function(t, k)
    if k == true then
      return parameters[currentfont()]
    else
      local parameters = identifiers[k].parameters
      t[k] = parameters
      return parameters
    end
  end)
  fonthashes.parameters = parameters
end

if not chardata then
  chardata = { }
  setmetatableindex(chardata, function(t, k)
    if k == true then
      return chardata[currentfont()]
    else
      local tfmdata = identifiers[k]
      if not tfmdata then --- unsafe
        tfmdata = font.fonts[k]
      end
      if tfmdata then
        local characters = tfmdata.characters
        t[k] = characters
        return characters
      end
    end
  end)
  fonthashes.characters = chardata
end

if not quaddata then
  quaddata = { }
  setmetatableindex(quaddata, function(t, k)
    if k == true then
      return quads[currentfont()]
    else
      local parameters = parameters[k]
      local quad = parameters and parameters.quad or 0
      t[k] = quad
      return quad
    end
  end)
  fonthashes.quads = quaddata
end

if not markdata then
  markdata = { }
  setmetatableindex(markdata, function(t, k)
    if k == true then
      return marks[currentfont()]
    else
      local resources = { }

      if identifiers[k] then
        resources = identifiers[k].resources or { }
      end

      local marks = resources.marks or { }
      t[k] = marks
      return marks
    end
  end)
  fonthashes.marks = markdata
end

--- next stems from the multilingual interface
interfaces                = interfaces or { }
interfaces.variables      = interfaces.variables or { }
interfaces.variables.max  = "max"

-----------------------------------------------------------------------
--- attr-ini
-----------------------------------------------------------------------

attributes = attributes or { } --- to be removed with cleanup

local hidden = {
  a_kerns     = luatexbase.new_attribute("typo-krn:a_kerns",    true),
  a_fontkern  = luatexbase.new_attribute("typo-krn:a_fontkern", true),
}

attributes.private = attributes.private or function (attr_name)
  local res = hidden[attr_name]
  if not res then
    res = luatexbase.new_attribute(attr_name)
  end
  return res
end

if luatexbase.get_unset_value then
  attributes.unsetvalue = luatexbase.get_unset_value()
else -- old luatexbase
  attributes.unsetvalue = (luatexbase.luatexversion < 37) and -1
                       or -2147483647
end

-----------------------------------------------------------------------
--- luat-sto
-----------------------------------------------------------------------

--- Storage is so ridiculously well designed in Context it’s a pity
--- we can’t just force every package author to use it.

storage           = storage or { }
storage.register  = storage.register or function (...)
  local t = { ... }
  --- sorry
  return t
end

-----------------------------------------------------------------------
--- node-fin
-----------------------------------------------------------------------

local plugin_store = { }

local installattributehandler = function (plugin)
  --- Context has some load() magic here.
  plugin_store[plugin.name] = plugin.processor
end

nodes.installattributehandler = installattributehandler

-----------------------------------------------------------------------
--- node-tsk
-----------------------------------------------------------------------

nodes.tasks               = nodes.tasks or { }
nodes.tasks.enableaction  = function () end

-----------------------------------------------------------------------
--- core-ctx
-----------------------------------------------------------------------

commands = commands or { }

--===================================================================--
---                              LOAD
--===================================================================--

--- we should be ready at this moment to insert the libraries

require "luaotfload-typo-krn"    --- typesetters.kerns
require "luaotfload-letterspace" --- typesetters.kernfont

--===================================================================--
---                              CLEAN
--===================================================================--
--- interface
-----------------------------------------------------------------------

local factors           = kerns.factors
local mapping           = kerns.mapping
local unsetvalue        = attributes.unset_value
local process_kerns     = plugin_store.kern

--- kern_callback     : normal
--- · callback:     process_kerns
--- · enabler:      enablecharacterkerning
--- · disabler:     disablecharacterkerning
--- · interface:    kerns.set

--- kernfont_callback : fontwise
--- · callback:     kernfont.handler
--- · enabler:      enablefontkerning
--- · disabler:     disablefontkerning

--- callback wrappers

--- (node_t -> node_t) -> string -> string list -> bool
local registered_as = { } --- procname -> callbacks
local add_processor = function (processor, name, ...)
  local callbacks = { ... }
  for i=1, #callbacks do
    luatexbase.add_to_callback(callbacks[i], processor, name)
  end
  registered_as[name] = callbacks --- for removal
  return true
end

--- string -> bool
local remove_processor = function (name)
  local callbacks = registered_as[name]
  if callbacks then
    for i=1, #callbacks do
      luatexbase.remove_from_callback(callbacks[i], name)
    end
    return true
  end
  return false --> unregistered
end

--- we use the same callbacks as a node processor in Context
--- unit -> bool
local enablecharacterkerning = function ( )
  return add_processor(function (head)
      return process_kerns("kerns", hidden.a_kerns, head)
    end,
    "typesetters.kerncharacters",
    "pre_linebreak_filter", "hpack_filter"
  )
end

--- unit -> bool
local disablecharacterkerning = function ( )
  return remove_processor "typesetters.kerncharacters"
end

kerns.enablecharacterkerning     = enablecharacterkerning
kerns.disablecharacterkerning    = disablecharacterkerning

--- now for the simplistic variant
--- unit -> bool
local enablefontkerning = function ( )
  return add_processor( kernfont.handler
                      , "typesetters.kernfont"
                      , "pre_linebreak_filter"
                      , "hpack_filter")
end

--- unit -> bool
local disablefontkerning = function ( )
  return remove_processor "typesetters.kernfont"
end

--- fontwise kerning uses a font property for passing along the
--- letterspacing factor

local fontkerning_enabled = false --- callback state

--- fontobj -> float -> unit
local initializefontkerning = function (tfmdata, factor)
  if factor ~= "max" then
    factor = tonumber(factor) or 0
  end
  if factor == "max" or factor ~= 0 then
    local fontproperties = tfmdata.properties
    if fontproperties then
      --- hopefully this field stays unused otherwise
      fontproperties.kerncharacters = factor
    end
    if not fontkerning_enabled then
      fontkerning_enabled = enablefontkerning()
    end
  end
end

--- like the font colorization, fontwise kerning is hooked into the
--- feature mechanism

otffeatures.register {
  name        = "kernfactor",
  description = "kernfactor",
  initializers = {
    base = initializefontkerning,
    node = initializefontkerning,
  }
}

--[[doc--

  The “letterspace” feature is essentially identical with the above
  “kernfactor” method, but scales the factor to percentages to match
  Xetex’s behavior. (See the Xetex reference, page 5, section 1.2.2.)

  Since Xetex doesn’t appear to have a (documented) “max” keyword, we
  assume all input values are numeric.

--doc]]--

local initializecompatfontkerning = function (tfmdata, percentage)
  local factor = tonumber (percentage)
  if not factor then
    logs.names_report ("both", 0, "letterspace",
                       "Invalid argument to letterspace: %s (type %q), " ..
                       "was expecting percentage as Lua number instead.",
                       percentage, type (percentage))
    return
  end
  return initializefontkerning (tfmdata, factor * 0.01)
end

otffeatures.register {
  name        = "letterspace",
  description = "letterspace",
  initializers = {
    base = initializecompatfontkerning,
    node = initializecompatfontkerning,
  }
}

kerns.set = nil

local characterkerning_enabled = false

kerns.set = function (factor)
    if factor ~= "max" then
        factor = tonumber(factor) or 0
    end
    if factor == "max" or factor ~= 0 then
        if not characterkerning_enabled then
            enablecharacterkerning()
            characterkerning_enabled = true
        end
        local a = factors[factor]
        if not a then
            a = #mapping + 1
            factors[factors], mapping[a] = a, factor
        end
        factor = a
    else
        factor = unsetvalue
    end
    texattribute[hidden.a_kerns] = factor
    return factor
end



-----------------------------------------------------------------------
--- options
-----------------------------------------------------------------------

kerns   .keepligature     = false --- supposed to be of type function
kerns   .keeptogether     = false --- supposed to be of type function
kernfont.keepligature     = false --- supposed to be of type function
kernfont.keeptogether     = false --- supposed to be of type function

-----------------------------------------------------------------------
--- erase fake Context layer
-----------------------------------------------------------------------

attributes     = nil
--commands       = nil  --- used in lualibs
storage        = nil    --- not to confuse with utilities.storage
nodes.tasks    = nil

collectgarbage"collect"

--[[example--

\input luaotfload.sty
\def\setcharacterkerning#1{% #1 factor : float
  \directlua{typesetters.kerns.set(0.618)}%
}
%directlua{typesetters.kerns.enablecharacterkerning()}

\font\iwona       = "name:Iwona:mode=node"                at 42pt
\font\lmregular   = "name:Latin Modern Roman:mode=node"   at 42pt

{\iwona
 foo
 {\setcharacterkerning{0.618}%
  bar}
 baz}

{\lmregular
 foo {\setcharacterkerning{0.125}ff fi ffi fl Th} baz}

{\lmregular
 \directlua{ %% I’m not exactly sure how those work
    typesetters.kerns.keepligature = function (start)
      print("[liga]", start)
      return true
    end
    typesetters.kerns.keeptogether = function (start)
      print("[keeptogether]", start)
      return true
    end}%
 foo {\setcharacterkerning{0.125}ff fi ffi fl Th} baz}

\bye
--example]]--

-- vim:ts=2:sw=2:expandtab