nomsu/core/metaprogramming.nom

#..
    This File contains actions for making actions and compile-time actions and some helper
    functions to make that easier.

# Compile-time action to make compile-time actions:
immediately:
    lua> ".."
        nomsu:define_compile_action("compile %actions to %lua", \(!! code location !!), function(\%actions, \%lua)
            local signature = {};
            for i, action in ipairs(\%actions.value) do signature[i] = action:get_src(); end
            local stubs = nomsu:get_stubs_from_signature(signature);
            local stub_args = nomsu:get_args_from_signature(signature);
            local arg_set = {};
            for i, arg in ipairs(stub_args[1]) do arg_set[arg] = true; end
            if \%lua.type == "Text" then
                error("Invalid type for 'compile % to %', expected a dict with expr/statements, but got text.", 0);
            end
            local body_lua = nomsu:tree_to_lua(\%lua);
            local body_code = body_lua.statements or ("return "..body_lua.expr..";");
            local undeclared_locals = {};
            for i, body_local in ipairs(body_lua.locals or {}) do
                if not arg_set[body_local] then
                    table.insert(undeclared_locals, body_local);
                end
            end
            if #undeclared_locals > 0 then
                body_code = "local "..table.concat(undeclared_locals, ", ")..";\\n"..body_code;
            end
            local lua_fn_args = table.concat(stub_args[1], ", ");
            local def_tree = nomsu.compilestack[#nomsu.compilestack];
            local code_location = ("%s:%s,%s"):format(def_tree.filename, def_tree.start, def_tree.stop);
            return {statements=([[
        nomsu:define_compile_action(]]..repr(signature)..[[, ]]..repr(code_location)..[[, function(]]..lua_fn_args..[[)
            ]]..body_code.."\\n"..[[
        end);
        ]])};
        end);

# Compile-time action to make actions
immediately:
    compile [action %actions %body] to:
        lua> ".."
            local signature = {};
            for i, action in ipairs(\%actions.value) do signature[i] = action:get_src(); end
            local stubs = nomsu:get_stubs_from_signature(signature);
            local stub_args = nomsu:get_args_from_signature(signature);
            local arg_set = {};
            for i, arg in ipairs(stub_args[1]) do arg_set[arg] = true; end
            local body_lua = nomsu:tree_to_lua(\%body);
            local body_code = body_lua.statements or ("return "..body_lua.expr..";");
            local undeclared_locals = {};
            for i, body_local in ipairs(body_lua.locals or {}) do
                if not arg_set[body_local] then
                    table.insert(undeclared_locals, body_local);
                end
            end
            if #undeclared_locals > 0 then
                body_code = "local "..table.concat(undeclared_locals, ", ")..";\\n"..body_code;
            end
            local lua_fn_args = table.concat(stub_args[1], ", ");
            local def_tree = nomsu.compilestack[#nomsu.compilestack];
            local code_location = ("%s:%s,%s"):format(def_tree.filename, def_tree.start, def_tree.stop);
            return {statements=[[
            nomsu:define_action(]]..repr(signature)..[[, ]]..repr(code_location)..[[, function(]]..lua_fn_args..[[)
                ]]..body_code.."\\n"..[[
            end);
            ]]};

# Macro to make nomsu macros:
immediately:
    compile [parse %shorthand as %longhand] to:
        lua> ".."
            local signature = {};
            for i, action in ipairs(\%shorthand.value) do signature[i] = action:get_src(); end
            local stubs = nomsu:get_stubs_from_signature(signature);
            local stub_args = nomsu:get_args_from_signature(signature);
            local lua_fn_args = table.concat(stub_args[1], ", ");
            local template;
            if \%longhand.type == "Block" then
                local lines = {};
                for i, line in ipairs(\%longhand.value) do lines[i] = nomsu:dedent(line:get_src()); end
                template = repr(table.concat(lines, "\\n"));
            else
                template = repr(nomsu:dedent(\%longhand:get_src()));
            end
            local replacements = {};
            for i, a in ipairs(stub_args[1]) do replacements[i] = a.."="..a; end
            replacements = "{"..table.concat(replacements, ", ").."}";
            local def_tree = nomsu.compilestack[#nomsu.compilestack];
            local code_location = ("%s:%s,%s"):format(def_tree.filename, def_tree.start, def_tree.stop);
            return {statements=[[
            nomsu:define_compile_action(]]..repr(signature)..[[, ]]..repr(code_location)..[[, function(]]..lua_fn_args..[[)
                local template = nomsu:parse(]]..template..[[, ]]..repr(def_tree.filename)..[[);
                local replacement = nomsu:tree_with_replaced_vars(template, ]]..replacements..[[);
                return nomsu:tree_to_lua(replacement);
            end);
            ]]};

action [remove action %stub]:
    lua> ".."
        local fn = ACTIONS[\%stub];
        local metadata = ACTION_METADATA[fn];
        for i=#metadata.aliases,1,-1 do
            metadata.arg_orders[metadata.aliases[i]] = nil;
            table.remove(metadata.aliases, i);
        end
        ACTIONS[\%stub] = nil;

immediately:
    action [%tree as lua]:
        =lua "nomsu:tree_to_lua(\%tree)"

    action [%tree as lua expr]:
        lua> ".."
            local lua = nomsu:tree_to_lua(\%tree);
            if lua.locals or not lua.expr then
                error("Invalid thing to convert to lua expr: "..\%tree:get_src());
            end
            return lua.expr;

    action [%tree as lua statements]:
        lua> ".."
            local lua = nomsu:tree_to_lua(\%tree);
            local code = lua.statements or (lua.expr..";");
            if lua.locals then
                code = "local "..table.concat(lua.locals, ", ")..";\\n"..code;
            end
            return code;

    action [%tree as value]:
        =lua "nomsu:tree_to_value(\%tree)"
    
immediately:
    compile [%tree's source code, %tree' source code] to {expr:"\(%tree as lua expr):get_src()"}

    compile [repr %obj] to {expr:"repr(\(%obj as lua expr))"}
    compile [type of %obj] to {expr:"type(\(%obj as lua expr))"}

immediately:
    compile [nomsu] to {expr:"nomsu"}
    compile [%var as lua identifier] to {expr:"nomsu:var_to_lua_identifier(\(%var as lua expr))"}

action [action %names metadata]:
    =lua "ACTION_METADATA[ACTIONS[\%names]]"

# Get the source code for a function
action [help %action]:
    lua> ".."
        local metadata = \(action %action metadata);
        if not metadata then
            print("Action not found: "..repr(\%action));
        else
            print(metadata.src or "<unknown source code>");
        end

# Compiler tools
immediately:
    compile [run %code] to {expr: "nomsu:run(\(%code as lua expr), '\(!! code location !!)')"}
    parse [enable debugging] as: lua> "nomsu.debug = true;"
    parse [disable debugging] as: lua> "nomsu.debug = false;"

immediately:
    compile [show lua %block] to:
        lua> ".."
            local \%lua = nomsu:tree_to_lua(\%block);
            return {statements = "print("..repr(\%lua.statements or \%lua.expr)..");"};

immediately:
    compile [say %message] to:
        lua> ".."
            if \%message.type == "Text" then
                return {statements="print("..\(%message as lua expr)..");"};
            else
                return {statements="print(stringify("..\(%message as lua expr).."));"};
            end

# Return
immediately:
    #.. Return statement is wrapped in a do..end block because Lua is unhappy if you
        put code after a return statement, unless you wrap it in a block.
    compile [return] to {statements:"do return; end"}
    compile [return %return_value] to {statements:"do return \(%return_value as lua expr); end"}

# Error functions
immediately:
    compile [barf] to {statements:"error(nil, 0);"}
    compile [barf %msg] to {statements:"error(\(%msg as lua expr), 0);"}
    compile [assume %condition] to:
        lua> "local \%assumption = 'Assumption failed: '..\%condition:get_src();"
        return {..}
            statements:".."
                if not \(%condition as lua expr) then
                    error(\(repr %assumption), 0);
                end
    compile [assume %condition or barf %msg] to {..}
        statements:".."
            if not \(%condition as lua expr) then
                error(\(%msg as lua expr), 0);
            end

# Literals
immediately:
    compile [yes] to {expr:"true"}
    compile [no] to {expr:"false"}
    compile [nothing, nil, null] to {expr:"nil"}