/*************************************************************************/
/*  expression.h                                                         */
/*************************************************************************/
/*                       This file is part of:                           */
/*                           GODOT ENGINE                                */
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/* Copyright (c) 2007-2021 Juan Linietsky, Ariel Manzur.                 */
/* Copyright (c) 2014-2021 Godot Engine contributors (cf. AUTHORS.md).   */
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/* "Software"), to deal in the Software without restriction, including   */
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/*************************************************************************/

#ifndef EXPRESSION_H
#define EXPRESSION_H

#include "core/object/ref_counted.h"

class Expression : public RefCounted {
	GDCLASS(Expression, RefCounted);

private:
	struct Input {
		Variant::Type type = Variant::NIL;
		String name;

		Input() {}
	};

	Vector<Input> inputs;
	Variant::Type output_type = Variant::NIL;

	String expression;

	bool sequenced = false;
	int str_ofs = 0;
	bool expression_dirty = false;

	bool _compile_expression();

	enum TokenType {
		TK_CURLY_BRACKET_OPEN,
		TK_CURLY_BRACKET_CLOSE,
		TK_BRACKET_OPEN,
		TK_BRACKET_CLOSE,
		TK_PARENTHESIS_OPEN,
		TK_PARENTHESIS_CLOSE,
		TK_IDENTIFIER,
		TK_BUILTIN_FUNC,
		TK_SELF,
		TK_CONSTANT,
		TK_BASIC_TYPE,
		TK_COLON,
		TK_COMMA,
		TK_PERIOD,
		TK_OP_IN,
		TK_OP_EQUAL,
		TK_OP_NOT_EQUAL,
		TK_OP_LESS,
		TK_OP_LESS_EQUAL,
		TK_OP_GREATER,
		TK_OP_GREATER_EQUAL,
		TK_OP_AND,
		TK_OP_OR,
		TK_OP_NOT,
		TK_OP_ADD,
		TK_OP_SUB,
		TK_OP_MUL,
		TK_OP_DIV,
		TK_OP_MOD,
		TK_OP_SHIFT_LEFT,
		TK_OP_SHIFT_RIGHT,
		TK_OP_BIT_AND,
		TK_OP_BIT_OR,
		TK_OP_BIT_XOR,
		TK_OP_BIT_INVERT,
		TK_INPUT,
		TK_EOF,
		TK_ERROR,
		TK_MAX
	};

	static const char *token_name[TK_MAX];
	struct Token {
		TokenType type;
		Variant value;
	};

	void _set_error(const String &p_err) {
		if (error_set) {
			return;
		}
		error_str = p_err;
		error_set = true;
	}

	Error _get_token(Token &r_token);

	String error_str;
	bool error_set = true;

	struct ENode {
		enum Type {
			TYPE_INPUT,
			TYPE_CONSTANT,
			TYPE_SELF,
			TYPE_OPERATOR,
			TYPE_INDEX,
			TYPE_NAMED_INDEX,
			TYPE_ARRAY,
			TYPE_DICTIONARY,
			TYPE_CONSTRUCTOR,
			TYPE_BUILTIN_FUNC,
			TYPE_CALL
		};

		ENode *next = nullptr;

		Type type = TYPE_INPUT;

		ENode() {}
		virtual ~ENode() {
			if (next) {
				memdelete(next);
			}
		}
	};

	struct ExpressionNode {
		bool is_op = false;
		union {
			Variant::Operator op;
			ENode *node;
		};
	};

	ENode *_parse_expression();

	struct InputNode : public ENode {
		int index = 0;
		InputNode() {
			type = TYPE_INPUT;
		}
	};

	struct ConstantNode : public ENode {
		Variant value = Variant::NIL;
		ConstantNode() {
			type = TYPE_CONSTANT;
		}
	};

	struct OperatorNode : public ENode {
		Variant::Operator op = Variant::Operator::OP_ADD;

		ENode *nodes[2] = { nullptr, nullptr };

		OperatorNode() {
			type = TYPE_OPERATOR;
		}
	};

	struct SelfNode : public ENode {
		SelfNode() {
			type = TYPE_SELF;
		}
	};

	struct IndexNode : public ENode {
		ENode *base = nullptr;
		ENode *index = nullptr;

		IndexNode() {
			type = TYPE_INDEX;
		}
	};

	struct NamedIndexNode : public ENode {
		ENode *base = nullptr;
		StringName name;

		NamedIndexNode() {
			type = TYPE_NAMED_INDEX;
		}
	};

	struct ConstructorNode : public ENode {
		Variant::Type data_type = Variant::Type::NIL;
		Vector<ENode *> arguments;

		ConstructorNode() {
			type = TYPE_CONSTRUCTOR;
		}
	};

	struct CallNode : public ENode {
		ENode *base = nullptr;
		StringName method;
		Vector<ENode *> arguments;

		CallNode() {
			type = TYPE_CALL;
		}
	};

	struct ArrayNode : public ENode {
		Vector<ENode *> array;
		ArrayNode() {
			type = TYPE_ARRAY;
		}
	};

	struct DictionaryNode : public ENode {
		Vector<ENode *> dict;
		DictionaryNode() {
			type = TYPE_DICTIONARY;
		}
	};

	struct BuiltinFuncNode : public ENode {
		StringName func;
		Vector<ENode *> arguments;
		BuiltinFuncNode() {
			type = TYPE_BUILTIN_FUNC;
		}
	};

	template <class T>
	T *alloc_node() {
		T *node = memnew(T);
		node->next = nodes;
		nodes = node;
		return node;
	}

	ENode *root = nullptr;
	ENode *nodes = nullptr;

	Vector<String> input_names;

	bool execution_error = false;
	bool _execute(const Array &p_inputs, Object *p_instance, Expression::ENode *p_node, Variant &r_ret, String &r_error_str);

protected:
	static void _bind_methods();

public:
	Error parse(const String &p_expression, const Vector<String> &p_input_names = Vector<String>());
	Variant execute(Array p_inputs = Array(), Object *p_base = nullptr, bool p_show_error = true);
	bool has_execute_failed() const;
	String get_error_text() const;

	Expression() {}
	~Expression();
};

#endif // EXPRESSION_H