# Rule for making rules
lua block ".."
    |compiler:defmacro("rule %spec = %body", function(compiler, vars, kind)
    |    if kind == "Expression" then
    |        compiler:error("Cannot use rule definitions as an expression.")
    |    end
    |    local spec = compiler:get_invocations_from_definition(vars.spec, vars)
    |    return ("compiler:def("..compiler.utils.repr(spec,true)..", "..compiler:tree_to_lua(vars.body, vars)..")"), true
    |end)

rule [help %invocation] =:
    lua block ".."
        |local fn_info = compiler.defs[vars.invocation]
        |if not fn_info then
        |    compiler:writeln("Function not found: "..compiler.utils.repr(vars.invocation, true))
        |else
        |    compiler:writeln("rule "..compiler.utils.repr(fn_info.invocations).." ="..(fn_info.src or ":\\n    <unknown source code>"))
        |end

# Macros
lua block ".."
    |local add_macro = function(compiler, vars, kind)
    |    local spec = compiler:get_invocations_from_definition(vars.spec, vars)
    |    local fn = compiler:tree_to_value(vars.body, vars)
    |    compiler:defmacro(spec, fn, vars.body.src)
    |    return "", true
    |end
    |compiler:defmacro("macro %spec = %body", add_macro)
    |
    |local add_macro_block = function(compiler, vars, kind)
    |    local spec = compiler:get_invocations_from_definition(vars.spec, vars)
    |    local fn = compiler:tree_to_value(vars.body, vars)
    |    local wrapper = function(compiler, vars, kind)
    |        if kind == "Expression" then
    |            compiler:error("Macro: "..spec.." was defined to be a block, but is being used as an expression.")
    |        end
    |        return ("do\\n"..fn(compiler, vars, kind).."\\nend"), true
    |    end
    |    compiler:defmacro(spec, wrapper, vars.body.src)
    |    return "", true
    |end
    |compiler:defmacro("macro block %spec = %body", add_macro_block)

# Compiler tools
rule [eval %code, run %code] =:
    lua expr "compiler:run(vars.code)"

rule [source code from tree %tree] =:
    lua block ".."
        |local _,_,leading_space = vars.tree.src:find("\\n(%s*)%S")
        |if leading_space then
        |    local chunk1, chunk2 = vars.tree.src:match(":%s*([^\\n]*)(\\n.*)")
        |    chunk2 = chunk2:gsub("\\n"..leading_space, "\\n")
        |    vars.source = chunk1..chunk2.."\\n"
        |else
        |    vars.source = vars.tree.src:match(":%s*(%S.*)").."\\n"
        |end

    %source

macro [source code %body] =:
    lua expr ".."
        |compiler.utils.repr(compiler:call("source code from tree %", vars.body), true)

rule [run file %filename] =:
    lua block ".."
        |local file = io.open(vars.filename)
        |return compiler:run(file:read("*a"))

# Error functions
rule [error!] =:
    lua block ".."
        |table.remove(compiler.callstack)
        |compiler:error()

rule [error %msg] =:
    lua block ".."
        |table.remove(compiler.callstack)
        |compiler:error(vars.msg)

# TODO: Make useful
macro [as lua %block] =:
    lua expr "compiler.utils.repr(compiler:tree_to_lua(vars.block.value, 'Statement'), true)"

macro block [show generated lua %block] =:
    ".."|compiler:writeln(\lua expr "compiler.utils.repr(compiler:tree_to_lua(vars.block.value, 'Statement'), true)"\)

# Macro helper functions
rule [%tree as value] =:
    lua expr ".."
        |compiler:tree_to_value(vars.tree, vars)

rule [%tree as lua block] =:
    lua block ".."
        |return compiler:tree_to_lua(vars.tree, 'Statement'), true

rule [%tree as lua expr] =:
    lua expr ".."
        |compiler:tree_to_lua(vars.tree, 'Expression')

# Moonscript!
macro block [moonscript block %moonscript_code] =:
    lua block ".."
        |local parse, compile = require('moonscript.parse'), require('moonscript.compile')
        |local moon_code = compiler:tree_to_value(vars.moonscript_code, vars)
        |local tree, err = parse.string(moon_code)
        |if not tree then
        |    compiler:error("Failed to parse moonscript: "..err)
        |end
        |local lua_code, err, pos = compile.tree(tree)
        |if not lua_code then
        |    compiler:error(compile.format_error(err, pos, moon_code))
        |end
        |return "do\\n"..lua_code.."\\nend"

macro [moonscript %moonscript_code] =:
    lua block ".."
        |local parse, compile = require('moonscript.parse'), require('moonscript.compile')
        |local moon_code = compiler:tree_to_value(vars.moonscript_code, vars)
        |local tree, err = parse.string(moon_code)
        |if not tree then
        |    compiler:error("Failed to parse moonscript: "..err)
        |end
        |local lua_code, err, pos = compile.tree(tree)
        |if not lua_code then
        |    compiler:error(compile.format_error(err, pos, moon_code))
        |end
        |return "(function(compiler, vars)\\n"..lua_code.."\\nend)(compiler, vars)"

# String functions
rule [join %strs] =:
    lua block ".."
        |local str_bits = {}
        |for i,bit in ipairs(vars.strs) do str_bits[i] = compiler.utils.repr(bit) end
        |return table.concat(str_bits)

rule [join %strs with glue %glue] =:
    lua block ".."
        |local str_bits = {}
        |for i,bit in ipairs(vars.strs) do str_bits[i] = compiler.utils.repr(bit) end
        |return table.concat(str_bits, vars.glue)

rule [capitalize %str, %str capitalized] =:
    lua expr ".."|vars.str:gsub("%l", string.upper, 1)

# Variable assignment
#..
    macro block [%var = %value] =:
        lua block ".."
            |if vars.var.type ~= "Var" then
            |    compiler:error("Assignment operation has the wrong type for the left hand side. "
            |        .."Expected Var, but got: "..vars.var.type)
            |end
        ".."|\%var as lua expr\ = \%value as lua expr\

lua block ".."
    |local function helper(callback)
    |    return function(compiler, vars, kind)
    |        if kind == "Expression" then
    |            compiler:error("Cannot use an assignment operation as an expression value.")
    |        end
    |        if vars.var.type ~= "Var" then
    |            compiler:error("Assignment operation has the wrong type for the left hand side. "
    |                .."Expected Var, but got: "..vars.var.type)
    |        end
    |        if vars.rhs.type ~= "Thunk" then
    |            compiler:error("Assignment operation has the wrong type for the right hand side. "
    |                .."Expected Thunk, but got: "..vars.rhs.type.."\\nMaybe you used '=' instead of '=:'?")
    |        end
    |        if #vars.rhs.value.value == 1 then
    |            return callback(compiler:tree_to_lua(vars.var, "Expression"),
    |                compiler:tree_to_lua(vars.rhs.value.value[1].value, "Expression")), true
    |        else
    |            local ret = "do\\n    local ret"
    |            ret = ret .. "\\n    "..compiler:tree_to_lua(vars.rhs.value, "Statement")
    |            ret = ret .. "\\n    "..callback(compiler:tree_to_lua(vars.var, "Expression"), "ret")
    |            return (ret.."\\nend"), true
    |        end
    |    end
    |end
    |compiler:defmacro("%var = %rhs", helper(function(var,result) return var.." = "..result end))
    |compiler:defmacro("%var += %rhs", helper(function(var,result) return var.." = "..var.." + "..result end))
    |compiler:defmacro("%var -= %rhs", helper(function(var,result) return var.." = "..var.." - "..result end))
    |compiler:defmacro("%var *= %rhs", helper(function(var,result) return var.." = "..var.." * "..result end))
    |compiler:defmacro("%var /= %rhs", helper(function(var,result) return var.." = "..var.." / "..result end))
    |compiler:defmacro("%var ^= %rhs", helper(function(var,result) return var.." = "..var.." ^ "..result end))
    |compiler:defmacro("%var and= %rhs", helper(function(var,result) return var.." = "..var.." and "..result end))
    |compiler:defmacro("%var or= %rhs", helper(function(var,result) return var.." = "..var.." or "..result end))
    |compiler:defmacro("%var concat= %rhs", helper(function(var,result) return var.." = "..var.." .. "..result end))
    |compiler:defmacro("%var mod= %rhs", helper(function(var,result) return var.." = "..var.." % "..result end))

# Operators
macro [true, yes] =: "true"
macro [false, no] =: "false"
macro [nil, null] =: "nil"
macro block [nop, pass] =: ""
macro [%a + %b] =: ".."|(\%a as lua expr\ + \%b as lua expr\)
macro [%a + %b + %c] =: ".."|(\%a as lua expr\ + \%b as lua expr\ + \%c as lua expr\)
macro [%a + %b + %c + %d] =: ".."|(\%a as lua expr\ + \%b as lua expr\ + \%c as lua expr\ + \%d as lua expr\)
macro [%a - %b] =: ".."|(\%a as lua expr\ - \%b as lua expr\)
macro [%a * %b] =: ".."|(\%a as lua expr\ * \%b as lua expr\)
macro [%a * %b * %c] =: ".."|(\%a as lua expr\ * \%b as lua expr\ * \%c as lua expr\)
macro [%a * %b * %c * %d] =: ".."|(\%a as lua expr\ * \%b as lua expr\ * \%c as lua expr\ * \%d as lua expr\)
macro [%a / %b] =: ".."|(\%a as lua expr\ / \%b as lua expr\)
macro [%a === %b] =: ".."|(\%a as lua expr\ == \%b as lua expr\)
macro [%a !== %b] =: ".."|(\%a as lua expr\ ~= \%b as lua expr\)
macro [%a < %b] =: ".."|(\%a as lua expr\ < \%b as lua expr\)
macro [%a < %b < %c] =: ".."|((\%a as lua expr\ < \%b as lua expr\) and (\%b as lua expr\ < \%c as lua expr\))
macro [%a <= %b < %c] =: ".."|((\%a as lua expr\ <= \%b as lua expr\) and (\%b as lua expr\ < \%c as lua expr\))
macro [%a <= %b <= %c] =: ".."|((\%a as lua expr\ <= \%b as lua expr\) and (\%b as lua expr\ <= \%c as lua expr\))
macro [%a < %b <= %c] =: ".."|((\%a as lua expr\ < \%b as lua expr\) and (\%b as lua expr\ <= \%c as lua expr\))
macro [%a > %b > %c] =: ".."|((\%a as lua expr\ > \%b as lua expr\) and (\%b as lua expr\ > \%c as lua expr\))
macro [%a >= %b > %c] =: ".."|((\%a as lua expr\ >= \%b as lua expr\) and (\%b as lua expr\ > \%c as lua expr\))
macro [%a >= %b >= %c] =: ".."|((\%a as lua expr\ >= \%b as lua expr\) and (\%b as lua expr\ >= \%c as lua expr\))
macro [%a > %b >= %c] =: ".."|((\%a as lua expr\ > \%b as lua expr\) and (\%b as lua expr\ >= \%c as lua expr\))
macro [%a <= %b] =: ".."|(\%a as lua expr\ <= \%b as lua expr\)
macro [%a > %b] =: ".."|(\%a as lua expr\ > \%b as lua expr\)
macro [%a >= %b] =: ".."|(\%a as lua expr\ >= \%b as lua expr\)
macro [%a ^ %b] =: ".."|(\%a as lua expr\ ^ \%b as lua expr\)
macro [%a and %b] =: ".."|(\%a as lua expr\ and \%b as lua expr\)
macro [%a and %b and %c] =:
    ".."|(\%a as lua expr\ and \%b as lua expr\ and \%c as lua expr\)
macro [%a and %b and %c and %d] =:
    ".."|(\%a as lua expr\ and \%b as lua expr\ and \%c as lua expr\ and \%d as lua expr\)
macro [%a or %b] =: ".."|(\%a as lua expr\ or \%b as lua expr\)
macro [%a or %b or %c] =:
    ".."|(\%a as lua expr\ or \%b as lua expr\ or \%c as lua expr\)
macro [%a or %b or %c or %d] =:
    ".."|(\%a as lua expr\ or \%b as lua expr\ or \%c as lua expr\ or \%d as lua expr\)
macro [%a mod %b] =: ".."|(\%a as lua expr\ mod \%b as lua expr\)
macro [- %a] =: ".."|-(\%a as lua expr\)
macro [not %a] =: ".."|not (\%a as lua expr\)

rule [%a == %b] =:
    lua expr "((vars.a == vars.b) or compiler.utils.equivalent(vars.a, vars.b))"
rule [%a != %b] =:
    lua expr "((vars.a ~= vars.b) or not compiler.utils.equivalent(vars.a, vars.b))"

macro [repr %obj] =:
    ".."|compiler.utils.repr(\%obj as lua expr\, true)

macro [say %str] =:
    ".."|compiler:writeln(compiler.utils.repr(\%str as lua expr\))

# Control flow
rule [do %action] =:
    lua expr "vars.action(compiler, setmetatable({}, {__index=vars}))"

macro block [return %return_value] =:
    lua block ".."
        |if vars.return_value.type ~= "Thunk" then
        |    compiler:error("Assignment operation has the wrong type for the right hand side. "
        |        .."Expected Thunk, but got: "..vars.return_value.type.."\\nMaybe you used '=' instead of '=:'?")
        |end
    ".."|do
        |    local ret
        |    \lua expr "compiler:tree_to_lua(vars.return_value.value, 'Statement')"\
        |    return ret
        |end

macro block [return] =:
    "return nil"

# Conditionals
macro block [if %condition %if_body] =:
    ".."|if \%condition as lua expr\ then
        |    \(lua expr "vars.if_body.value") as lua block\
        |end

macro block [if %condition %if_body else %else_body] =:
    ".."|if \%condition as lua expr\ then
        |    \(lua expr "vars.if_body.value") as lua block\
        |else
        |    \(lua expr "vars.else_body.value") as lua block\
        |end

# Ternary operator
macro [%if_expr if %condition else %else_expr] =:
    ".."|(function(compiler, vars)
        |    if \%condition as lua expr\ then
        |        return \%if_expr as lua expr\
        |    else
        |        return \%else_expr as lua expr\
        |    end
        |end)(compiler, vars)


# Loop control flow
macro block [break] =: "break"
macro block [continue] =: "continue"
# TODO: add labeled break/continue?

# GOTOs
lua block ".."
    |local function lua_label(label)
    |    if label.type ~= "Var" then
    |        compiler:error("Goto label has the wrong type for the label. Expected Var, but got: "..label.type)
    |    end
    |    local bits = "abcdefghijklmnop"
    |    local lua_identifier = "label_"
    |    for i=1,#label.value do
    |        local byte = string.byte(label.value, i)
    |        local low = byte % 16
    |        local high = (byte - low) / 16
    |        lua_identifier = lua_identifier .. bits:sub(low+1,low+1) .. bits:sub(high+1,high+1)
    |    end
    |    return lua_identifier
    |end
    |
    |compiler:defmacro("-> %label", function(compiler, vars, kind)
    |    return "::"..lua_label(vars.label).."::", true
    |end)
    |compiler:defmacro("go to %label", function(compiler, vars, kind)
    |    return "goto "..lua_label(vars.label), true
    |end)

# While loops
macro block [repeat %body] =:
    ".."|while true do
        |    \(lua expr "vars.body.value") as lua block\
        |end
macro block [repeat while %condition %body] =:
    ".."|while \%condition as lua expr\ do
        |    \(lua expr "vars.body.value") as lua block\
        |end
macro block [repeat until %condition %body] =:
    ".."|while not (\%condition as lua expr\) do
        |    \(lua expr "vars.body.value") as lua block\
        |end

# For loops
macro block [for %var in %iterable %body] =:
    %var-type =: lua expr "vars.var.type"
    if (%var-type != "Var"):
        error ".."
            |For loop has the wrong type for the loop variable. Expected Var, but got: \%var-type\
    %var-code =: %var as lua expr
    ".."|local old_loopval = \%var-code\
        |for i,value in ipairs(\%iterable as lua expr\) do
        |    \%var-code\ = value
        |    \(lua expr "vars.body.value") as lua block\
        |end
        |\%var-code\ = old_loopval

macro block [for all %iterable %body] =:
    ".."|local old_loopval = vars.it
        |for i,value in ipairs(\%iterable as lua expr\) do
        |    vars.it = value
        |    \(lua expr "vars.body.value") as lua block\
        |end
        |vars.it = old_loopval

# Switch statement/multi-branch if
macro block [when %body] =:
    %result =: ""
    for %statement in (lua expr "vars.body.value.value"):
        %func-call =: lua expr "vars.statement.value"
        if ((lua expr "vars['func-call'].type") != "FunctionCall"):
            error "Invalid format for 'when' statement"
        %tokens =: lua expr "vars['func-call'].value"
        %star =: lua expr "vars.tokens[1]"
        if (((lua expr "vars.star.type") != "Word") or ((lua expr "vars.star.value") != "*")):
            error "Invalid format for 'when' statement"
        %thunk =: lua expr "vars.tokens[#vars.tokens]"
        if ((lua expr "vars.thunk.type") != "Thunk"):
            error "Invalid format for 'when' statement"
        %condition-bits =: []
        for %i in (2 up to (lua expr "#vars.tokens")):
            lua block "table.insert(vars['condition-bits'], vars.tokens[vars.i])"
        %condition =: dict [..]
            ["type",lua expr "vars['func-call'].type"]
            ["src",lua expr "vars['func-call'].src"]
            ["value", %condition-bits]
        if ((lua expr "#vars.condition.value") == 0):
            %result concat=: ".."
                |
                |do
                |    local ret
                |    \(lua expr "vars.thunk.value") as lua block\
                |    return ret
                |end
        ..else:
            %result concat=: ".."
                |
                |if \%condition as lua expr\ then
                |    local ret
                |    \(lua expr "vars.thunk.value") as lua block\
                |    return ret
                |end
    %result

# List Comprehension
# TODO: maybe make this lazy, or a lazy version?
macro [%expression for %var in %iterable] =:
    %var-type =: lua expr "vars.var.type"
    if (%var-type != "Var"):
        error ".."
            |List comprehension has the wrong type for the loop variable. Expected Var, but got: \%var-type\
    %var-code =: %var as lua expr
    ".."|(function(game, vars)
        |    local comprehension = {}
        |    for i,value in ipairs(\%iterable as lua expr\) do
        |        \%var-code\ = value
        |        comprehension[i] = \%expression as lua expr\
        |    end
        |    return comprehension
        |end)(game, setmetatable({}, {__index=vars}))

macro [%expression for all %iterable] =:
    ".."|(function(game, vars)
        |    local comprehension = {}
        |    for i,value in ipairs(\%iterable as lua expr\) do
        |        vars.it = value
        |        comprehension[i] = \%expression as lua expr\
        |    end
        |    return comprehension
        |end)(game, setmetatable({}, {__index=vars}))

# Dict comprehension
macro [%key -> %value for %var in %iterable] =:
    %var-type =: lua expr "vars.var.type"
    if (%var-type != "Var"):
        error ".."
            |Dict comprehension has the wrong type for the loop variable. Expected Var, but got: \%var-type\
    %var-code =: %var as lua expr
    ".."|(function(game, vars)
        |    local comprehension = {}
        |    for i,value in ipairs(\%iterable as lua expr\) do
        |        \%var-code\ = value
        |        comprehension[\%key as lua expr\] = \%value as lua expr\
        |    end
        |    return comprehension
        |end)(game, setmetatable({}, {__index=vars}))

macro [%key -> %value for all %iterable] =:
    ".."|(function(game, vars)
        |    local comprehension = {}
        |    for i,value in ipairs(\%iterable as lua expr\) do
        |        vars.it = value
        |        comprehension[\%key as lua expr\] = \%value as lua expr\
        |    end
        |    return comprehension
        |end)(game, setmetatable({}, {__index=vars}))

# Number ranges
rule [%start up to %stop] =:
    lua expr "compiler.utils.range(vars.start,vars.stop-1)"

rule [%start thru %stop, %start through %stop] =:
    lua expr "compiler.utils.range(vars.start,vars.stop)"

rule [%start down to %stop] =:
    lua expr "compiler.utils.range(vars.start,vars.stop+1,-1)"

rule [%start down thru %stop, %start down through %stop] =:
    lua expr "compiler.utils.range(vars.start,vars.stop,-1)"

rule [%start up to %stop via %step] =:
    lua expr "compiler.utils.range(vars.start,vars.stop-1,vars.step)"

rule [%start thru %stop via %step, %start through %stop via %step] =:
    lua expr "compiler.utils.range(vars.start,vars.stop,vars.step)"

rule [%start down to %stop via %step] =:
    lua expr "compiler.utils.range(vars.start,vars.stop+1,-vars.step)"

rule [%start down thru %stop via %step, %start down through %stop via %step] =:
    lua expr "compiler.utils.range(vars.start,vars.stop,-vars.step)"

# Common utility functions
rule [random number] =: lua expr "math.random()"
rule [sum of %items] =: lua expr "compiler.utils.sum(vars.items)"
rule [product of %items] =: lua expr "compiler.utils.product(vars.items)"
rule [all of %items] =: lua expr "compiler.utils.all(vars.items)"
rule [any of %items] =: lua expr "compiler.utils.any(vars.items)"
rule [avg of %items, average of %items] =:
    lua expr "(compiler.utils.sum(vars.items)/#vars.items)"
rule [min of %items, smallest of %items, lowest of %items] =:
    lua expr "compiler.utils.min(vars.items)"
rule [max of %items, biggest of %items, largest of %items, highest of %items] =:
    lua expr "compiler.utils.min(vars.items)"

rule [min of %items with respect to %keys] =:
    lua expr "compiler.utils.min(vars.items, vars.keys)"
rule [max of %items with respect to %keys] =:
    lua expr "compiler.utils.max(vars.items, vars.keys)"

# List/dict functions
macro [..]
    %list's %index, %index st in %list, %index nd in %list, %index rd in %list
    %index th in %list, %index in %list, %list -> %index
..=:
    ".."|\%list as lua expr\[\%index as lua expr\]
    ".."|\%list as lua expr\[\%index as lua expr\]
macro [first in %list] =:
    ".."|\%list as lua expr\[1]

macro [..]
    %index st to last in %list, %index nd to last in %list, %index rd to last in %list
    %index th to last in %list
..=:
    ".."|compiler.utils.nth_to_last(\%list as lua expr\, \%index as lua expr\)
macro [last in %list] =:
    ".."|compiler.utils.nth_to_last(\%list as lua expr\, 1)

macro block [..]
    %list's %index = %new_value, %index st in %list = %new_value, %index nd in %list = %new_value
    %index rd in %list = %new_value, %index th in %list = %new_value, %index in %list = %new_value
    %list -> %index = %new_value
..=:
    lua block ".."
        |if vars.new_value.type ~= "Thunk" then
        |    compiler:error("Dict assignment operation has the wrong type for the right hand side. "
        |        .."Expected Thunk, but got: "..vars.new_value.type.."\\nMaybe you used '=' instead of '=:'?")
        |end
    ".."|do
        |    local ret
        |    \lua expr "compiler:tree_to_lua(vars.new_value.value, 'Statement')"\
        |    \%list as lua expr\[\%index as lua expr\] = ret
        |end

macro [append %item to %list, add %item to %list] =:
    ".."|table.insert(\%list as lua expr\, \%item as lua expr\)

rule [flatten %lists] =:
    %flat =: []
    for %list in %lists:
        for %item in %list:
            add %item to %flat
    %flat

macro [%item is in %list, %list contains %item] =:
    ".."|(\%list as lua expr\[\%index as lua expr\] ~= nil)

macro [length of %list, size of %list, number of %list] =:
    ".."|#(\%list as lua expr\)

rule [dict %items] =:
    %dict =: []
    for %pair in %items:
        lua block "vars.dict[vars.pair[1]] = vars.pair[2]"
    return: %dict

rule [entries in %dict] =:
    lua block ".."
        |local items = {}
        |for k,v in pairs(vars.dict) do
        |    table.insert(items, {key=k,value=v})
        |end
        |return items

# Permission functions
rule [restrict %fn to within %whitelist] =:
    lua block ".."
        |local fns = compiler:get_invocations(vars.fn)
        |local whitelist = compiler:get_invocations(vars.whitelist)
        |local whiteset = {}
        |for _,w in ipairs(whitelist) do
        |    if not compiler.defs[w] then
        |        compiler:error("Undefined function: "..tostring(w))
        |    else whiteset[w] = true
        |    end
        |end
        |for _,fn in ipairs(fns) do
        |    local fn_info = compiler.defs[fn]
        |    if fn_info == nil then
        |        compiler:error("Undefined function: "..tostring(fn))
        |    elseif not compiler:check_permission(fn) then
        |        compiler:writeln("You do not have permission to restrict function: "..tostring(fn))
        |    else
        |        compiler.defs[fn].whiteset = whiteset
        |    end
        |end

rule [allow %whitelist to use %fn] =:
    lua block ".."
        |local fns = compiler:get_invocations(vars.fn)
        |local whitelist = compiler:get_invocations(vars.whitelist)
        |for _,w in ipairs(whitelist) do
        |    if not compiler.defs[w] then
        |        compiler:error("Undefined function: "..tostring(w))
        |    end
        |end
        |for _,fn in ipairs(fns) do
        |    local fn_info = compiler.defs[fn]
        |    if fn_info == nil then
        |        compiler:error("Undefined function: "..tostring(fn))
        |    elseif fn_info.whiteset == nil then
        |        compiler:writeln("Function is already allowed by everyone: "..tostring(fn))
        |    elseif not compiler:check_permission(fn) then
        |        compiler:writeln("You do not have permission to grant permissions for function: "..tostring(fn))
        |    else
        |        for _,w in ipairs(whitelist) do
        |            fn_info.whiteset[w] = true
        |        end
        |    end
        |end

rule [forbid %blacklist to use %fn] =:
    lua block ".."
        |local fns = compiler:get_invocations(vars.fn)
        |local blacklist = compiler:get_invocations(vars.blacklist)
        |for _,b in ipairs(blacklist) do
        |    if not compiler.defs[b] then
        |        compiler:error("Undefined function: "..tostring(b))
        |    end
        |end
        |for _,fn in ipairs(fns) do
        |    local fn_info = compiler.defs[fn]
        |    if fn_info == nil then
        |        compiler:error("Undefined function: "..tostring(fn))
        |    elseif fn_info.whiteset == nil then
        |        compiler:writeln("Cannot remove items from a whitelist when there is no whitelist on function: "..tostring(fn))
        |    elseif not compiler:check_permission(fn) then
        |        compiler:writeln("You do not have permission to restrict function: "..tostring(fn))
        |    else
        |        for _,b in ipairs(blacklist) do fn_info.whiteset[b] = nil end
        |    end
        |end

# For unit testing
macro [parse tree %code] =:
    lua expr "compiler.utils.repr(compiler:stringify_tree(vars.code.value), true)"

macro block [test %code yields %expected] =:
    %generated =: lua expr "compiler.utils.repr(compiler:stringify_tree(vars.code.value), true)"
    %expected =: %expected as lua expr
    if (%generated != %expected):
        say "Test failed!"
        say "Expected:"
        say %expected
        say "But got:"
        say %generated
        error!
    return: ""