if not modules then modules = { } end modules ['toks-scn'] = {
    version   = 1.001,
    author    = "Hans Hagen, PRAGMA-ADE, Hasselt NL",
    copyright = "PRAGMA ADE / ConTeXt Development Team",
    license   = "see context related readme files"
}

-- Writing this kind of code (and completing the newtoken code base) is fun. I did
-- so with the brilliant film music from The Girl with the Dragon Tattoo running in a
-- loop in the background (three cd's by Trent Reznor and Atticus Ross). An alien
-- feeling helps with alien code.

-- todo: more \let's at the tex end

local type, next, tostring, tonumber = type, next, tostring, tonumber

local formatters          = string.formatters
local concat              = table.concat

local scanners            = tokens.scanners
local tokenbits           = tokens.bits

local scanstring          = scanners.string
local scanargument        = scanners.argument
local scandelimited       = scanners.delimited
local scanverbatim        = scanners.verbatim
local scantokenlist       = scanners.tokenlist
local scantoks            = scanners.toks
local scaninteger         = scanners.integer
local scancardinal        = scanners.cardinal
local scannumber          = scanners.number
local scanfloat           = scanners.float
local scankeyword         = scanners.keyword
local scankeywordcs       = scanners.keywordcs
local scanword            = scanners.word
local scanletters         = scanners.letters
local scankey             = scanners.key
local scancode            = scanners.code
local scanboolean         = scanners.boolean
local scandimen           = scanners.dimen
local scanglue            = scanners.glue
local scangluevalues      = scanners.gluevalues
local scangluespec        = scanners.gluespec
local scancsname          = scanners.csname
local scanintegerargument = scanners.integerargument
local scandimenargument   = scanners.dimenargument
local scandetokened       = scanners.detokened

local todimen             = number.todimen
local toboolean           = toboolean

local lpegmatch           = lpeg.match
local p_unquoted          = lpeg.Cs(lpeg.patterns.unquoted)

local trace_compile       = false  trackers.register("tokens.compile", function(v) trace_compile = v end)
local report_compile      = logs.reporter("tokens","compile")
local report_scan         = logs.reporter("tokens","scan")

local open                = tokenbits.open
local close               = tokenbits.close

local function scanopen()
    while true do
        local c = scancode(open)
        if c == 123 then -- {
            return true
     -- elseif c ~= 32 then
        elseif not c then
            return
        end
    end
end

local function scanclose()
    while true do
        local c = scancode(close)
        if c == 125 then -- }
            return true
     -- elseif c ~= 32 then
        elseif not c then
            return
        end
    end
end

scanners.scanopen  = scanopen
scanners.scanclose = scanclose

local function scanlist()
    local wrapped = scanopen()
    local list    = { }
    local size    = 0
    while true do
        local entry = scanstring()
        if entry then
            size = size + 1
            list[size] = entry
        else
            break
        end
    end
    if wrapped then
        scanclose()
    end
    return list
end

local function scanconditional()
    local kw = scanword()
    if kw == "true" then
        return true
    end
    if kw == "false" then
        return false
    end
    local c = scaninteger()
    if c then
        return c == 0 -- with a conditional 0=true
    end
    return nil
end

local function scantable(t,data)
    if not data then
        data = { }
    end
    if t then
        local wrapped = scanopen()
        while true do
            local key = scanword(true)
            if key then
                local get = t[key]
                if get then
                    data[key] = get()
                else
                    -- catch all we can get
                end
            else
                break
            end
        end
        if wrapped then
            scanclose()
        end
    end
    return data
end

function tokens.constant(s)
    if type(s) == "string" then
        return "'" .. s .. "'"
    else
        return s
    end
end

scanners.list        = scanlist
scanners.table       = scantable
scanners.conditional = scanconditional

function scanners.whd()
    local width, height, depth
    while true do
        if scankeyword("width") then
            width = scandimen()
        elseif scankeyword("height") then
            height = scandimen()
        elseif scankeyword("depth") then
            depth = scandimen()
        else
            break
        end
    end
    if width or height or depth then
        return width or 0, height or 0, depth or 0
    else
        -- we inherit
    end
end

local l = utf.byte("[")
local r = utf.byte("]")

local function scanbracketed()
    local s = scandelimited(l, r)
    if s then
        return s
    else
        local readstate = status.getreadstate()
        report_scan("missing argument in line %i of %a", readstate.linenumber, readstate.filename)
        return ""
    end
end

local function scanoptional()
    return scandelimited(l, r) or ""
end

local function scanbracketedasis()
    return scandelimited(l, r, false)
end

local function scanargumentasis()
    return scanargument(false)
end

local function scancsnameunchecked()
    return scancsname(true)
end

scanners.bracketed       = scanbracketed
scanners.optional        = scanoptional
scanners.bracketedasis   = scanbracketedasis
scanners.argumentasis    = scanargumentasis
scanners.csnameunchecked = scancsnameunchecked

--------.detokenize      = function() return scanners.tokenstring(false) end -- needs testing

local shortcuts = {
    tokens              = tokens,
    bits                = tokenbits,
    open                = open,
    close               = close,
    scanners            = scanners,
    scanstring          = scanstring,
    scanargument        = scanargument,
    scantokenstring     = scanners.tokenstring,
 -- scandetokenize      = scanners.detokenize,
    scanverbatim        = scanverbatim,
    scantokenlist       = scantokenlist,
    scantoks            = scantoks,
    scaninteger         = scaninteger,
    scancardinal        = scancardinal,
    scannumber          = scannumber,
    scanfloat           = scanfloat,
    scantable           = scantable, -- not directly useable
    scankeyword         = scankeyword,
    scankeywordcs       = scankeywordcs,
    scanword            = scanword,
    scanletters         = scanletters,
 -- scankey             = scankey,
    scancode            = scancode,
    scanboolean         = scanboolean,
    scanglue            = scanglue, -- list
    scangluespec        = scangluespec,
    scangluevalues      = scangluevalues,
    scandimen           = scandimen,
    scandimension       = scandimen,
    scanbox             = scanners.box,
    scanhbox            = scanners.hbox,
    scanvbox            = scanners.vbox,
    scanvtop            = scanners.vtop,
    scanconditional     = scanconditional,
    scanopen            = scanopen,
    scanclose           = scanclose,
    scanlist            = scanlist,
    scancsname          = scancsname,
    scancsnameunchecked = scancsnameunchecked,
    scandelimited       = scandelimited, -- not directly useable
    scanbracketed       = scanbracketed,
    scanoptional        = scanoptional,
    scanbracketedasis   = scanbracketedasis,
    scanargumentasis    = scanargumentasis,
    scanintegerargument = scanintegerargument,
    scandimenargument   = scandimenargument,
    scandetokened       = scandetokened,
    todimen             = todimen,
    tonumber            = tonumber,
    tostring            = tostring,
    toboolean           = toboolean,
    inspect             = inspect,
    report              = report_scan,
    posit               = posit,
}

tokens.shortcuts = shortcuts

local load = load
local dump = string.dump

local function loadstripped(code)
     return load(code,nil,nil,shortcuts)
  -- return load(dump(load(code),true),nil,nil,shortcuts)
end

tokens.converters = {
    tonumber  = "tonumber",
    tostring  = "tostring",
    toboolean = "toboolean",
    todimen   = "todimen",
    toglue    = "todimen",
}

-- We could just pickup a keyword but then we really need to make sure that no number
-- follows it when that is the assignment and adding an optional = defeats the gain
-- in speed. Currently we have sources with no spaces (\startcontextdefinitioncode
-- ...) so it fails there.
--
-- Another drawback is that we then need to use { } instead of ending with \relax (as
-- we can do now) but that is no big deal. It's just that I then need to check the TeX
-- end. More pain than gain and a bit risky too. Using scanletters works better, but
-- the gain is only some 10 percent but if we don't have keywords with numbers it might
-- make sense in the end, some day.

local f_if           = formatters[    "  if scankeywordcs('%s') then data['%s'] = scan%s()"]
local f_elseif       = formatters["  elseif scankeywordcs('%s') then data['%s'] = scan%s()"]

----- f_if_x         = formatters[    "  if not data['%s'] and scankeywordcs('%s') then data['%s'] = scan%s()"]
----- f_elseif_x     = formatters["  elseif not data['%s'] and scankeywordcs('%s') then data['%s'] = scan%s()"]

----- f_if           = formatters["  local key = scanletters() if key == '' then break elseif key == '%s' then data['%s'] = scan%s()"]
----- f_elseif       = formatters["  elseif key == '%s' then data['%s'] = scan%s()"]

local f_local        = formatters["local scan%s = scanners.%s"]
local f_scan         = formatters["scan%s()"]
local f_shortcut     = formatters["local %s = scanners.converters.%s"]

local f_if_c         = formatters[    "  if scankeywordcs('%s') then data['%s'] = %s(scan%s())"]
local f_elseif_c     = formatters["  elseif scankeywordcs('%s') then data['%s'] = %s(scan%s())"]
local f_scan_c       = formatters["%s(scan%s())"]

-- see above

----- f_if_c         = formatters["  local key = scanletters() if key == '' then break elseif key == '%s' then data['%s'] = %s(scan%s())"]
----- f_elseif_c     = formatters["  elseif k == '%s' then data['%s'] = %s(scan%s())"]

local f_any          = formatters["  else local key = scanword(true) if key then data[key] = scan%s() else break end end"]
local f_any_c        = formatters["  else local key = scanword(true) if key then data[key] = %s(scan%s()) else break end end"]
local s_done <const> = "  else break end"

local f_any_all      = formatters["  local key = scanword(true) if key then data[key] = scan%s() else break end"]
local f_any_all_c    = formatters["  local key = scanword(true) if key then data[key] = %s(scan%s()) else break end"]

local f_table        = formatters["%\nt\nreturn function()\n  local data = { }\n%s\n  return %s\nend\n"]
local f_sequence     = formatters["%\nt\n%\nt\n%\nt\nreturn function()\n    return %s\nend\n"]
local f_singular     = formatters["%\nt\n%\nt\n\nreturn function(%s)\n    return %s\nend\n"]
local f_simple       = formatters["%\nt\nreturn function()\n    return %s\nend\n"]
local f_string       = formatters["%q"]
local f_action_f     = formatters["action%s(%s)"]
local f_action_s     = formatters["local action%s = tokens._action[%s]"]
local f_nested       = formatters["local function scan%s()\n  local data = { }\n%s\n  return data\nend\n"]

local f_check = formatters[ [[
  local wrapped = scanopen()
  while true do
    ]] .. "%\nt\n" .. [[
    %s
  end
  if wrapped then
    scanclose()
  end
]] ]

-- using these shortcuts saves temporary small tables (okay, it looks uglier)

local presets = {
    ["1 string" ] = { "string" },
    ["2 strings"] = { "string", "string" },
    ["3 strings"] = { "string", "string", "string" },
    ["4 strings"] = { "string", "string", "string", "string" },
    ["5 strings"] = { "string", "string", "string", "string", "string" },
    ["6 strings"] = { "string", "string", "string", "string", "string", "string" },
    ["7 strings"] = { "string", "string", "string", "string", "string", "string", "string" },
    ["8 strings"] = { "string", "string", "string", "string", "string", "string", "string", "string" },

    ["1 argument" ] = { "argument" },
    ["2 arguments"] = { "argument", "argument" },
    ["3 arguments"] = { "argument", "argument", "argument" },
    ["4 arguments"] = { "argument", "argument", "argument", "argument" },

    ["1 integer"]  = { "integer" },
    ["2 integers"] = { "integer", "integer" },
    ["3 integers"] = { "integer", "integer", "integer" },
    ["4 integers"] = { "integer", "integer", "integer", "integer" },

    ["1 optional"]  = { "optional" },
    ["2 optionals"] = { "optional", "optional" },
    ["3 optionals"] = { "optional", "optional", "optional" },
    ["4 optionals"] = { "optional", "optional", "optional", "optional" },
}

tokens.presets = presets

function tokens.compile(specification)
    local f = { }
    local n = 0
    local c = { }
    local t = specification.arguments or specification
    local a = specification.actions or nil
    if type(a) == "function" then
        a = { a }
    end
    local code
    local args
    local function compile(t,nested)
        local done = s_done
        local r = { }
        local m = 0
        for i=1,#t do
            local ti = t[i]
            if ti == "*" and i == 1 then
                done = f_any_all("string")
            else
                local t1 = ti[1]
                local t2 = ti[2] or "string"
                if type(t2) == "table" then
                    n = n + 1
                    f[n] = compile(t2,n)
                    t2 = n
                end
                local t3 = ti[3]
                if type(t3) == "function" then
                    -- todo: also create shortcut
                elseif t3 then
                    c[t3] = f_shortcut(t3,t3)
                    if t1 == "*" then
                        if i == 1 then
                            done = f_any_all_c(t3,t2)
                            break
                        else
                            done = f_any_c(t3,t2)
                        end
                    else
                        m = m + 1
                        r[m] = (m > 1 and f_elseif_c or f_if_c)(t1,t1,t3,t2)
                    end
                else
                    if t1 == "*" then
                        if i == 1 then
                            done = f_any_all(t2)
                            break
                        else
                            done = f_any(t2)
                        end
                    else
                        m = m + 1
                        r[m] = (m > 1 and f_elseif   or f_if  )(t1,t1,t2)
                     -- r[m] = (m > 1 and f_elseif_x or f_if_x)(t1,t1,t1,t2)
                    end
                end
            end
        end
        local c = f_check(r,done)
        if nested then
            return f_nested(nested,c)
        else
            return c
        end
    end
    local p = t and presets[t] -- already done in implement
    if p then
        t = p
    end
    local tt = type(t)
    if tt == "string" then
        if a then
            local s = lpegmatch(p_unquoted,t)
            if s and t ~= s then
                code = t
            else
                code = f_scan(t)
            end
            tokens._action = a
            for i=1,#a do
                code = f_action_f(i,code)
                n    = n + 1
                f[n] = f_action_s(i,i)
            end
            code = f_simple(f,code)
        else
            return scanners[t]
        end
    elseif tt ~= "table" then
        return
    elseif #t == 1 then
        local ti = t[1]
        if type(ti) == "table" then
            ti = compile(ti)
            code = "data"
            if a then
                tokens._action = a
                for i=1,#a do
                    code = f_action_f(i,code)
                    n    = n + 1
                    f[n] = f_action_s(i,i)
                end
            end
            code = f_table(f,ti,code)
        elseif a then
            code = f_scan(ti)
            tokens._action = a
            for i=1,#a do
                code = f_action_f(i,code)
                n    = n + 1
                f[n] = f_action_s(i,i)
            end
            code = f_simple(f,code)
        else
            return scanners[ti]
        end
    elseif #t == 0 then
        if specification.usage == "value" then
            code = "b"
            args = "_,b"
        else
            code = ""
            args = ""
        end
        if a then
            tokens._action = a
            for i=1,#a do
                code = f_action_f(i,code)
                n    = n + 1
                f[n] = f_action_s(i,i)
            end
        end
        code = f_singular(c,f,args,code)
    else
        local r = { }
        local p = { }
        local m = 0
        for i=1,#t do
            local ti = t[i]
            local tt = type(ti)
            if tt == "table" then
                if ti[1] == "_constant_" then
                    local v = ti[2]
                    if type(v) == "string" then
                        r[i] = f_string(v)
                    else
                        r[i] = tostring(v)
                    end
                else
                    m = m + 1
                    p[m] = compile(ti,100+m)
                    r[i] = f_scan(100+m)
                end
            elseif tt == "number" then
                r[i] = tostring(ti)
            elseif tt == "boolean" then
                r[i] = tostring(ti)
            else
                local s = lpegmatch(p_unquoted,ti)
                if s and ti ~= s then
                    r[i] = ti -- a string, given as "'foo'" or '"foo"'
                elseif scanners[ti] then
                    r[i] = f_scan(ti)
                else
                    report_compile("unknown scanner %a",ti)
                    r[i] = ti
                end
            end
        end
        code = concat(r,",")
        if a then
            tokens._action = a
            for i=1,#a do
                code = f_action_f(i,code)
                n    = n + 1
                f[n] = f_action_s(i,i)
            end
        end
        code = f_sequence(c,f,p,code)
    end
    if not code then
        return
    end
    if trace_compile then
        report_compile("code: %s",code)
    end
    local code, message = loadstripped(code)
    if code then
        code = code() -- sets action
    else
        report_compile("error in code: %s",code)
        report_compile("error message: %s",message)
    end
    if a then
        tokens._action = nil
    end
    if code then
        return code
    end
end

-- local fetch = tokens.compile {
--     "string",
--     "string",
--     {
--         { "data",    "string" },
--         { "tab",     "string" },
--         { "method",  "string" },
--         { "foo", {
--             { "method", "integer" },
--             { "compact", "number" },
--             { "nature" },
--             { "*" }, -- any key
--         } },
--         { "compact", "string", "tonumber" },
--         { "nature",  "boolean" },
--         { "escape",  "string" },
--         { "escape"  },
--     },
--     "boolean",
-- }
--
-- os.exit()