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

local load, type, tonumber = load, type, tonumber
local find, gsub = string.find, string.gsub
local concat = table.concat
local utfchar = utf.char
local S, C, P, lpegmatch, lpegtsplitat = lpeg.S, lpeg.C, lpeg.P, lpeg.match, lpeg.tsplitat

local xmath                    = xmath    or math
local xcomplex                 = xcomplex or { }

----- scannext                 = token.scannext
local scancmdchr               = token.scancmdchrexpanded
local scantoken                = token.scantoken
local getcsname                = token.getcsname

local cmd                      = tokens.commands
local letter_code              = cmd.letter
local other_char_code          = cmd.other_char
local spacer_code              = cmd.spacer
local other_char_code          = cmd.other_char
local relax_code               = cmd.relax
local register_int_code        = cmd.register_int
local internal_int_code        = cmd.internal_int
local register_dimen_code      = cmd.register_dimen
local internal_dimen_code      = cmd.internal_dimen
local register_glue_code       = cmd.register_glue
local internal_glue_code       = cmd.internal_glue
local register_toks_code       = cmd.register_toks
local internal_toks_code       = cmd.internal_toks
local char_given_code          = cmd.char_given
local math_given_code          = cmd.math_given
local xmath_given_code         = cmd.xmath_given
local some_item_code           = cmd.some_item

local getdimen                 = tex.getdimen
local getglue                  = tex.getglue
local getcount                 = tex.getcount
local gettoks                  = tex.gettoks
local gettex                   = tex.get

local context                  = context
commands                       = commands or { }
local commands                 = commands
local context                  = context
local implement                = interfaces.implement
local dimenfactors             = number.dimenfactors

local ctx_protected_cs         = context.protected.cs -- more efficient
local ctx_firstoftwoarguments  = context.firstoftwoarguments
local ctx_secondoftwoarguments = context.secondoftwoarguments
local ctx_firstofoneargument   = context.firstofoneargument
local ctx_gobbleoneargument    = context.gobbleoneargument

local values                   = tokens.values
local boolean_code             = values.boolean

implement { -- will be overloaded later
    name      = "writestatus",
    arguments = "2 arguments",
    actions   = logs.status,
}

function commands.doifelse(b)
    if b then
        ctx_firstoftwoarguments()
    else
        ctx_secondoftwoarguments()
    end
end

function commands.doifelsesomething(b)
    if b and b ~= "" then
        ctx_firstoftwoarguments()
    else
        ctx_secondoftwoarguments()
    end
end

function commands.doif(b)
    if b then
        ctx_firstofoneargument()
    else
        ctx_gobbleoneargument()
    end
end

function commands.doifsomething(b)
    if b and b ~= "" then
        ctx_firstofoneargument()
    else
        ctx_gobbleoneargument()
    end
end

function commands.doifnot(b)
    if b then
        ctx_gobbleoneargument()
    else
        ctx_firstofoneargument()
    end
end

function commands.doifnotthing(b)
    if b and b ~= "" then
        ctx_gobbleoneargument()
    else
        ctx_firstofoneargument()
    end
end

commands.testcase = commands.doifelse -- obsolete

function commands.boolcase(b)
    context(b and 1 or 0)
end

function commands.doifelsespaces(str)
    if find(str,"^ +$") then
        ctx_firstoftwoarguments()
    else
        ctx_secondoftwoarguments()
    end
end

local pattern = lpeg.patterns.validdimen

function commands.doifelsedimenstring(str)
    if lpegmatch(pattern,str) then
        ctx_firstoftwoarguments()
    else
        ctx_secondoftwoarguments()
    end
end

local p_first = C((1-P(",")-P(-1))^0)

implement {
    name      = "firstinset",
    arguments = "string",
    actions   = function(str) context(lpegmatch(p_first,str or "")) end,
    public    = true,
}

implement {
    name      = "ntimes",
    arguments = { "string", "integer" },
    actions   = { string.rep, context }
}

implement {
    name      = "execute",
    arguments = "string",
    actions   = os.execute -- wrapped in sandbox
}

implement {
    name      = "doifelsesame",
    arguments = "2 strings",
    actions   = function(a,b)
        if a == b then
            ctx_firstoftwoarguments()
        else
            ctx_secondoftwoarguments()
        end
    end
}

implement {
    name      = "doifsame",
    arguments = "2 strings",
    actions   = function(a,b)
        if a == b then
            ctx_firstofoneargument()
        else
            ctx_gobbleoneargument()
        end
    end
}

implement {
    name      = "doifnotsame",
    arguments = "2 strings",
    actions   = function(a,b)
        if a == b then
            ctx_gobbleoneargument()
        else
            ctx_firstofoneargument()
        end
    end
}

-- This is a bit of a joke as I never really needed floating point expressions (okay,
-- maybe only with scaling because there one can get numbers that are too large for
-- dimensions to deal with). Of course one can write a parser in \TEX\ speak but then
-- one also needs to implement a bunch of functions. It doesn't pay of so we just
-- stick to the next gimmick. It looks inefficient but performance is actually quite
-- efficient.

do

    local result = { "return " }
    local word   = { }
    local r      = 1
    local w      = 0

    local report = logs.reporter("system","expression")

    local function unexpected(c)
        report("unexpected token %a",c)
    end

    local function unexpected(c)
        report("unexpected token %a",c)
    end

    local function expression()
        local w = 0
        local r = 1
        while true do
        local n, i = scancmdchr()
            if n == letter_code then
                w = w + 1 ; word[w] = utfchar(i)
            else
                if w > 0 then
                    -- we could use a metatable for all math, complex and factors
                    local s = concat(word,"",1,w)
                    local d = dimenfactors[s]
                    if d then
                        r = r + 1 ; result[r] = "*"
                        r = r + 1 ; result[r] = 1/d
                    else
                        if xmath[s] then
                            r = r + 1 ; result[r] = "xmath."
                        elseif xcomplex[s] then
                            r = r + 1 ; result[r] = "xcomplex."
                        end
                        r = r + 1 ; result[r] = s
                    end
                    w = 0
                end
                if     n == other_char_code then
                    r = r + 1 ; result[r] = utfchar(i)
                elseif n == spacer_code then
                -- r = r + 1 ; result[r] = " "
                elseif n == relax_code then
                    break
                elseif n == register_int_code or n == internal_int_code then
                    r = r + 1 ; result[r] = getcount(i)
                elseif n == register_dimen_code or n == internal_dimen_code then
                    r = r + 1 ; result[r] = getdimen(i)
                elseif n == register_glue_code or n == n == register_dimen_code_glue_code then
                    r = r + 1 ; result[r] = getglue(i)
                elseif n == register_toks_code or n == n == register_dimen_code_toks_code then
                    r = r + 1 ; result[r] = gettoks(i)
                elseif n == char_given_code or n == math_given_code or n == xmath_given_code then
                    r = r + 1 ; result[r] = i
                elseif n == some_item_code then
                    local n = getcsname(t)
                    if n then
                        local s = gettex(n)
                        if s then
                            r = r + 1 ; result[r] = s
                        else
                            unexpected(c)
                        end
                    else
                        unexpected(c)
                    end
             -- elseif n == call_code then
             --     local n = getcsname(t)
             --     if n then
             --         local s = get_macro(n)
             --         if s then
             --             r = r + 1 ; result[r] = s
             --         else
             --             unexpected(c)
             --         end
             --     else
             --         unexpected(c)
             --     end
             -- elseif n == the_code or n == convert_code or n == lua_expandable_call_code then
             --     put_next(t)
             --     scantoken() -- expands
                else
                    unexpected(c)
                end
            end
        end
        local code = concat(result,"",1,r)
        local func = load(code)
        if type(func) == "function" then
            context(func())
        else
            report("invalid lua %a",code)
        end
    end

    implement {
        public  = true,
        name    = "expression",
        actions = expression,
    }

end

do

    interfaces.implement {
        name      = "iflua",
        public    = true,
        usage     = "condition",
        arguments = "string",
        actions   = function(s)
            local c = load("return(" .. s .. ")")
            return boolean_code, (c and c()) and true or false
        end,
    }

end

do

    -- This is some 20% slower than native but we only provide this for compatibility
    -- reasons so we don't care that much about it. Eventually we can drop the built-in
    -- method.

    local channels = { }
    local lastdone = { }

    local findbinfile = resolvers.findbinfile
    local loadbinfile = resolvers.loadbinfile
    local opentexfile = resolvers.opentexfile

    local scaninteger = tokens.scanners.integer
    local scankeyword = tokens.scanners.keyword
    local scanstring  = tokens.scanners.string
    local scancsname  = tokens.scanners.csname

    local setmacro    = tokens.setters.macro
    local rlncatcodes = tex.rlncatcodes
    local texgetcount = tex.getcount

    local bytes       = string.bytes
    local getcatcode  = tex.getcatcode

    local char, concat = string.char, table.concat

    -- This uses the normal bin lookup method that we also use for other files,
    -- and in principle there is no limit on the amount of files other than the
    -- operating system imposes.

    local t = { }
    local l = 0

    implement {
        name    = "openin",
        public  = true,
        usage   = "value",
        actions = function()
            local n = scaninteger()
                      scankeyword("=")
            local s = scanstring(true)
            local c = channels[n]
            if c then
                c:close()
            end
            local f = findbinfile(s,"tex")
            if f then
                channels[n] = opentexfile(f)
                lastdone[n] = false
            else
                channels[n] = false
                lastdone[n] = true
            end
        end,
    }

    implement {
        name    = "closein",
        public  = true,
        usage   = "value",
        actions = function()
            local n = scaninteger()
            local c = channels[n]
            if c then
                c:close()
            end
            channels[n] = false
            t = { }
        end,
    }

    -- This is not the fastest routine but hardly used, occasionally for line by line
    -- input in e.g. tikz which is not that fast anyway so I'll deal with it when it
    -- really is a bottleneck.

    local readerror = function(what,n)
        tex.error(string.formatters["too many %s brace tokens in read from channel %i"](what,n))
    end

    interfaces.implement {
        name    = "read",
        public  = true,
        usage   = "value",
        actions = function(prefix)
            local n = scaninteger()
            local c = channels[n]
            if scankeyword("line") and c then
                c:gotoline(scaninteger())
            end
            scankeyword("to")
            local m = scancsname(true)
            local g = 0
            local s
            l = 0
            if c then
                while true do
                    local s = c and c:reader()
                    if s then
                        l = l + 1
                        s = gsub(s," *$","")
                        t[l] = s
                        for c in bytes(s) do
                            local cc = getcatcode(c)
                            if cc == 1 then
                                g = g + 1
                            elseif cc == 2 then
                                g = g - 1
                            end
                        end
                        if g <= 0 then
                            break
                        end
                    else
                        break
                    end
                end
                if g > 0 then
                    readerror("left",n)
                    s = ""
                elseif g < 0 then
                    readerror("right",n)
                    s = ""
                elseif l == 0 then
                    if c:endoffile() then
                        lastdone[n] = true
                        s = "\\par"
                    else
                        s = ""
                    end
                    channels[n] = false
                else
                    local e = texgetcount("endlinechar") -- we can have tex.endline if needed
                    if e < 0 or e > 127 then
                        e = ""
                    else
                        e = " "
                        l = l + 1
                        t[l] = ""
                    end
                    s = concat(t, e, 1, l)
                end
            else
                s = ""
            end
            setmacro(m, s, prefix) -- checks for frozen
        end,
    }

    -- This is an etex extension. All characters become catcode 12 but a space gets code
    -- 10. The etex manual specifies a lineending of catcode 12 too. Should we strip spaces
    -- at the end? A bit weird command that we never use anyway.

    implement {
        name      = "readline",
        public    = true,
        usage     = "value",
        actions   = function(prefix)
            local n = scaninteger()
            local c = channels[n]
            if scankeyword("line") and c then
                c:gotoline(scaninteger())
            end
            scankeyword("to")
            local m = scancsname(true)
            local s = c and c:reader()
            if s then
                local e = texgetcount("endlinechar") -- we can have tex.endline if needed
                if e > 0 then -- forget about 0
                    s = s .. char(e)
                end
            else
                channels[n] = false
                s = ""
            end
            setmacro(rlncatcodes, m, s, prefix) -- checks for frozen
        end,
    }

    implement {
        name      = "readlinedirect",
        public    = true,
        untraced  = true,
        actions   = function(prefix)
            local n = scaninteger()
            local c = channels[n]
            if scankeyword("line") and c then
                c:gotoline(scaninteger())
            end
            local s = c and c:reader()
            if s then
                local e = texgetcount("endlinechar") -- we can have tex.endline if needed
                if e > 0 then -- forget about 0
                    s = s .. char(e)
                end
                context(s)
            else
                channels[n] = false
            end
        end,
    }

    -- This one uses the special lua condition option which is kind of experimental
    -- but seems to work fine.

    local boolean_value = tokens.values.boolean

    implement {
        name      = "ifeof",
        public    = true,
        usage     = "condition",
        actions   = function()
            local n = scaninteger()
            return boolean_value, not channels[n]
        end,
    }

    -- This one doesn't belong here and it might become a real primitive if we need it
    -- frequently. So, for the moment we keep it in this file.

    local getnest = tex.getnest

    implement {
        name      = "ifmvl",
        public    = true,
        usage     = "condition",
        actions   = function()
            return boolean_value, getnest("ptr") == 0
        end,
    }

end