UserScript/src/generator.cpp

#include <ranges>

#include "UserScript/interpreter.h"

namespace scripting {

// Replace with constexpr vector & find ?
	static const std::map<ast::operator_t, ByteCodeInterpreter::operator_t> mappings = {
		{ast::operator_t::logical_not,           ByteCodeInterpreter::operator_t::logical_not},
		{ast::operator_t::binary_not,            ByteCodeInterpreter::operator_t::binary_not},
		{ast::operator_t::divide,                ByteCodeInterpreter::operator_t::divide},
		{ast::operator_t::modulo,                ByteCodeInterpreter::operator_t::modulo},
		{ast::operator_t::multiply,              ByteCodeInterpreter::operator_t::multiply},
		{ast::operator_t::subtract,              ByteCodeInterpreter::operator_t::subtract},
		{ast::operator_t::add,                   ByteCodeInterpreter::operator_t::add},
		{ast::operator_t::bitshift_left,         ByteCodeInterpreter::operator_t::bitshift_left},
		{ast::operator_t::bitshift_right,        ByteCodeInterpreter::operator_t::bitshift_right},
		{ast::operator_t::rotate_left,           ByteCodeInterpreter::operator_t::rotate_left},
		{ast::operator_t::rotate_right,          ByteCodeInterpreter::operator_t::rotate_right},
		{ast::operator_t::less_than,             ByteCodeInterpreter::operator_t::less_than},
		{ast::operator_t::greater_than,          ByteCodeInterpreter::operator_t::greater_than},
		{ast::operator_t::less_or_equal_than,    ByteCodeInterpreter::operator_t::less_or_equal_than},
		{ast::operator_t::greater_or_equal_than, ByteCodeInterpreter::operator_t::greater_or_equal_than},
		{ast::operator_t::equals,                ByteCodeInterpreter::operator_t::equals},
		{ast::operator_t::different,             ByteCodeInterpreter::operator_t::different},
		{ast::operator_t::binary_and,            ByteCodeInterpreter::operator_t::binary_and},
		{ast::operator_t::binary_or,             ByteCodeInterpreter::operator_t::binary_or},
		{ast::operator_t::binary_xor,            ByteCodeInterpreter::operator_t::binary_xor},
		{ast::operator_t::logical_and,           ByteCodeInterpreter::operator_t::logical_and},
		{ast::operator_t::logical_or,            ByteCodeInterpreter::operator_t::logical_or},
	};

/// GENERATION HANDLERS DECLARATIONS
	
	template<typename T>
	void handle(std::vector<ByteCodeInterpreter::operand> &, std::vector<script_error> &, T &);
	
	template<>
	void handle<ast::block>(std::vector<ByteCodeInterpreter::operand> &ctx, std::vector<script_error> &errors,
	                        ast::block &block);
	
	template<>
	void
	handle<ast::command_expression>(std::vector<ByteCodeInterpreter::operand> &ctx, std::vector<script_error> &errors,
	                                ast::command_expression &cmd);
	
	template<>
	void handle<ast::binary_algebraic_expression>(std::vector<ByteCodeInterpreter::operand> &ctx,
	                                              std::vector<script_error> &errors,
	                                              ast::binary_algebraic_expression &cmd);
	
	template<>
	void handle<ast::unary_algebraic_expression>(std::vector<ByteCodeInterpreter::operand> &ctx,
	                                             std::vector<script_error> &errors,
	                                             ast::unary_algebraic_expression &cmd);
	
	template<>
	void
	handle<ast::paren_expression>(std::vector<ByteCodeInterpreter::operand> &ctx, std::vector<script_error> &errors,
	                              ast::paren_expression &cmd);
	
	template<>
	void handle<ast::conditional>(std::vector<ByteCodeInterpreter::operand> &ctx, std::vector<script_error> &errors,
	                              ast::conditional &cmd);
	
	template<>
	void handle<ast::while_loop>(std::vector<ByteCodeInterpreter::operand> &ctx, std::vector<script_error> &errors,
	                             ast::while_loop &cmd);
	
	template<>
	void handle<ast::expression>(std::vector<ByteCodeInterpreter::operand> &ctx, std::vector<script_error> &errors,
	                             ast::expression &cmd);
	
	template<>
	void
	handle<ast::variable_expression>(std::vector<ByteCodeInterpreter::operand> &ctx, std::vector<script_error> &errors,
	                                 ast::variable_expression &cmd);
	
	template<>
	void handle<ast::literal_int_expression>(std::vector<ByteCodeInterpreter::operand> &ctx,
	                                         std::vector<script_error> &errors, ast::literal_int_expression &cmd);
	
	template<>
	void handle<ast::literal_string_expression>(std::vector<ByteCodeInterpreter::operand> &ctx,
	                                            std::vector<script_error> &errors, ast::literal_string_expression &cmd);

/// GENERATION HANDLERS DEFINITIONS
	
	template<>
	void handle<ast::block>(std::vector<ByteCodeInterpreter::operand> &ctx, std::vector<script_error> &errors,
	                        ast::block &block) {
		for (auto &elem: block.contents) {
			std::visit([&](auto &v) { handle(ctx, errors, *v); }, elem.contents);
			ctx.push_back(ByteCodeInterpreter::operand{.element = ByteCodeInterpreter::operator_t::INTERNAL_stack_cls});
		}
	}
	
	template<>
	void
	handle<ast::command_expression>(std::vector<ByteCodeInterpreter::operand> &ctx, std::vector<script_error> &errors,
	                                ast::command_expression &cmd) {
		for (auto& argument : std::ranges::reverse_view(cmd.arguments)) {
			std::visit([&](auto &v) { handle(ctx, errors, *v); }, argument->contents);
		}
		ctx.push_back(
			ByteCodeInterpreter::operand{.element = ByteCodeInterpreter::function_tag{.name = cmd.name.value, .arity = cmd.arguments.size()}, .location = cmd.location});
	}
	
	template<>
	void
	handle<ast::paren_expression>(std::vector<ByteCodeInterpreter::operand> &ctx, std::vector<script_error> &errors,
	                              ast::paren_expression &expr) {
		std::visit([&](auto &v) { handle(ctx, errors, *v); }, expr.content);
	}
	
	template<>
	void handle<ast::expression>(std::vector<ByteCodeInterpreter::operand> &ctx, std::vector<script_error> &errors,
	                             ast::expression &expr) {
		std::visit([&](auto &v) { handle(ctx, errors, *v); }, expr.contents);
	}
	
	template<>
	void handle<ast::binary_algebraic_expression>(std::vector<ByteCodeInterpreter::operand> &ctx,
	                                              std::vector<script_error> &errors,
	                                              ast::binary_algebraic_expression &expr) {
		handle(ctx, errors, *expr.lhs);
		handle(ctx, errors, *expr.rhs);
		ctx.push_back(ByteCodeInterpreter::operand{.element = mappings.at(expr.op), .location = expr.location});
	}
	
	template<>
	void handle<ast::unary_algebraic_expression>(std::vector<ByteCodeInterpreter::operand> &ctx,
	                                             std::vector<script_error> &errors,
	                                             ast::unary_algebraic_expression &expr) {
		handle(ctx, errors, *expr.content);
		ctx.push_back(ByteCodeInterpreter::operand{.element = mappings.at(expr.op), .location = expr.location});
	}
	
	template<>
	void
	handle<ast::variable_expression>(std::vector<ByteCodeInterpreter::operand> &ctx, std::vector<script_error> &errors,
	                                 ast::variable_expression &expr) {
		ctx.push_back(ByteCodeInterpreter::operand{
			ByteCodeInterpreter::variable_tag{.name = expr.name.value, .location = expr.location}});
	}
	
	template<>
	void handle<ast::literal_int_expression>(std::vector<ByteCodeInterpreter::operand> &ctx,
	                                         std::vector<script_error> &errors, ast::literal_int_expression &expr) {
		ctx.push_back(ByteCodeInterpreter::operand{script_value{expr.value}});
	}
	
	template<>
	void handle<ast::literal_string_expression>(std::vector<ByteCodeInterpreter::operand> &ctx,
	                                            std::vector<script_error> &errors,
	                                            ast::literal_string_expression &expr) {
		ctx.push_back(ByteCodeInterpreter::operand{script_value{expr.value}});
	}
	
	template<>
	void handle<ast::conditional>(std::vector<ByteCodeInterpreter::operand> &ctx, std::vector<script_error> &errors,
	                              ast::conditional &cond) {
		/// some basic documentation (from before the reference stability bug but things are the same):
		/// https://app.excalidraw.com/s/hxPegpAmTX/2c8KKzinqeg
		std::visit([&](auto &v) { handle(ctx, errors, *v); }, cond.condition->contents);
		ctx.push_back(ByteCodeInterpreter::operand{.element = script_value{}, .location = cond.location});
		/// As you can see, being smart is dumb, be a fucking monkey that comes from the 70s and use 70s technology:tm: to your advantage
		/// More seriously, WTF (?) we do this because we used to have a bug with unreliable references to these locations, which makes sense since we
		/// don't have reference stability
		auto else_side_idx = ctx.size() - 1;
		ctx.push_back(
			ByteCodeInterpreter::operand{.element = ByteCodeInterpreter::operator_t::INTERNAL_jump_if, .location = cond.location});
		handle(ctx, errors, *cond.on_condition);
		if (cond.otherwise) {
			ctx.push_back(ByteCodeInterpreter::operand{.element = script_value{}, .location = cond.location});
			auto end_side_idx = ctx.size() - 1;
			ctx.push_back(
				ByteCodeInterpreter::operand{.element = ByteCodeInterpreter::operator_t::INTERNAL_jump, .location = cond.location});
			ctx[else_side_idx].element = static_cast<int32_t>(ctx.size()) - 1;
			ctx[else_side_idx].location = cond.location;
			handle(ctx, errors, *cond.otherwise);
			ctx[end_side_idx].element = static_cast<int32_t>(ctx.size()) - 1;
			ctx[end_side_idx].location = cond.location;
		} else {
			ctx[else_side_idx].element = static_cast<int32_t>(ctx.size()) - 1;
			ctx[else_side_idx].location = cond.location;
		}
	}
	
	template<>
	void handle<ast::while_loop>(std::vector<ByteCodeInterpreter::operand> &ctx, std::vector<script_error> &errors,
	                             ast::while_loop &cond) {
		auto beforewhile_side_idx = static_cast<int32_t>(ctx.size()) - 1;
		std::visit([&](auto &v) { handle(ctx, errors, *v); }, cond.condition->contents);
		ctx.push_back(ByteCodeInterpreter::operand{.element = script_value{}, .location = cond.location});
		auto endwhile_side_idx = ctx.size() - 1;
		ctx.push_back(
			ByteCodeInterpreter::operand{.element = ByteCodeInterpreter::operator_t::INTERNAL_jump_if, .location = cond.location});
		handle(ctx, errors, *cond.on_condition);
		ctx.push_back(
			ByteCodeInterpreter::operand{.element = script_value{beforewhile_side_idx}, .location = cond.location});
		ctx.push_back(
			ByteCodeInterpreter::operand{.element = ByteCodeInterpreter::operator_t::INTERNAL_jump, .location = cond.location});
		ctx[endwhile_side_idx].element = static_cast<int32_t>(ctx.size()) - 1;
		ctx[endwhile_side_idx].location = cond.location;
	}
	
	std::vector<ByteCodeInterpreter::operand>
	ByteCodeInterpreter::generate(std::vector<script_error> &errors, ast::block &tree, bool loop) {
		std::vector<operand> code;
		
		handle(code, errors, tree);
		if (loop) {
			// Here we have to deal with the quirks of jumping before the increments happens again
			code.push_back(ByteCodeInterpreter::operand{.element = script_value{-1}, .location = tree.location});
			code.push_back(
				ByteCodeInterpreter::operand{.element = ByteCodeInterpreter::operator_t::INTERNAL_jump, .location = tree.location});
		}
		return code;
	}
}