// This Source Code Form is subject to the terms of the Mozilla Public License
// v. 2.0. If a copy of the MPL was not distributed with this file, You can
// obtain one at http://mozilla.org/MPL/2.0/.
#pragma once

#include <cstdint>
#include <memory>
#include <string>
#include <vector>
#include "elna/source/result.h"

namespace elna
{
namespace source
{
    enum class binary_operator
    {
        sum,
        subtraction,
        multiplication,
        division,
        remainder,
        equals,
        not_equals,
        less,
        greater,
        less_equal,
        greater_equal,
        disjunction,
        conjunction
    };

    enum class unary_operator
    {
        reference,
        negation
    };

    class variable_declaration;
    class constant_definition;
    class procedure_definition;
    class type_definition;
    class call_expression;
    class assign_statement;
    class if_statement;
    class while_statement;
    class return_statement;
    class expression_statement;
    class block;
    class program;
    class binary_expression;
    class unary_expression;
    class basic_type_expression;
    class array_type_expression;
    class pointer_type_expression;
    class record_type_expression;
    class union_type_expression;
    class variable_expression;
    class array_access_expression;
    class field_access_expression;
    class dereference_expression;
    template<typename T>
    class number_literal;
    class char_literal;
    class string_literal;

    /**
     * Interface for AST visitors.
     */
    struct parser_visitor
    {
        virtual void visit(variable_declaration *) = 0;
        virtual void visit(constant_definition *) = 0;
        virtual void visit(procedure_definition *) = 0;
        virtual void visit(type_definition *) = 0;
        virtual void visit(call_expression *) = 0;
        virtual void visit(expression_statement *) = 0;
        virtual void visit(assign_statement *) = 0;
        virtual void visit(if_statement *) = 0;
        virtual void visit(while_statement *) = 0;
        virtual void visit(return_statement *) = 0;
        virtual void visit(block *) = 0;
        virtual void visit(program *) = 0;
        virtual void visit(binary_expression *) = 0;
        virtual void visit(unary_expression *) = 0;
        virtual void visit(basic_type_expression *) = 0;
        virtual void visit(array_type_expression *) = 0;
        virtual void visit(pointer_type_expression *) = 0;
        virtual void visit(record_type_expression *) = 0;
        virtual void visit(union_type_expression *) = 0;
        virtual void visit(variable_expression *) = 0;
        virtual void visit(array_access_expression *) = 0;
        virtual void visit(field_access_expression *is_field_access) = 0;
        virtual void visit(dereference_expression *is_dereference) = 0;
        virtual void visit(number_literal<std::int32_t> *) = 0;
        virtual void visit(number_literal<std::uint32_t> *) = 0;
        virtual void visit(number_literal<double> *) = 0;
        virtual void visit(number_literal<bool> *) = 0;
        virtual void visit(number_literal<unsigned char> *) = 0;
        virtual void visit(string_literal *) = 0;
    };

    /**
     * A visitor which visits all nodes but does nothing.
     */
    struct empty_visitor : parser_visitor
    {
        virtual void visit(variable_declaration *) override;
        virtual void visit(constant_definition *definition) override;
        virtual void visit(procedure_definition *definition) override;
        virtual void visit(type_definition *definition) override;
        virtual void visit(call_expression *statement) override;
        virtual void visit(expression_statement *statement) override;
        virtual void visit(assign_statement *statement) override;
        virtual void visit(if_statement *) override;
        virtual void visit(while_statement *) override;
        virtual void visit(return_statement *) override;
        virtual void visit(block *block) override;
        virtual void visit(program *program) override;
        virtual void visit(binary_expression *expression) override;
        virtual void visit(unary_expression *expression) override;
        virtual void visit(basic_type_expression *) override;
        virtual void visit(array_type_expression *expression) override;
        virtual void visit(pointer_type_expression *) override;
        virtual void visit(record_type_expression *expression) override;
        virtual void visit(union_type_expression *expression) override;
        virtual void visit(variable_expression *) override;
        virtual void visit(array_access_expression *expression) override;
        virtual void visit(field_access_expression *expression) override;
        virtual void visit(dereference_expression *expression) override;
        virtual void visit(number_literal<std::int32_t> *) override;
        virtual void visit(number_literal<std::uint32_t> *) override;
        virtual void visit(number_literal<double> *) override;
        virtual void visit(number_literal<bool> *) override;
        virtual void visit(number_literal<unsigned char> *) override;
        virtual void visit(string_literal *) override;
    };

    /**
     * Operand representing a subexpression in the 3 address code.
     */
    struct operand
    {
    public:
        virtual ~operand() = 0;
    };

    struct integer_operand final : public operand
    {
        std::int32_t m_value;

    public:
        explicit integer_operand(const std::int32_t value);

        std::int32_t value() const;
    };

    class variable_operand final : public operand
    {
        std::string m_name;

    public:
        explicit variable_operand(const std::string& name);

        const std::string& name() const;
    };

    struct temporary_variable final : public operand
    {
        std::size_t m_counter;

    public:
        explicit temporary_variable(const std::size_t counter);

        std::size_t counter() const;
    };

    struct label_operand final : public operand
    {
        std::size_t m_counter;

    public:
        explicit label_operand(const std::size_t counter);

        std::size_t counter() const;
    };

    /**
     * AST node.
     */
    class node
    {
        const struct position source_position;

    protected:
        /**
         * \param position Source code position.
         */
        explicit node(const position position);

    public:
        virtual ~node() = default;
        virtual void accept(parser_visitor *) = 0;

        /**
         * \return Node position in the source code.
         */
        const struct position& position() const;
    };

    class statement : public node
    {
    protected:
        /**
         * \param position Source code position.
         */
        explicit statement(const struct position position);
    };

    class expression : public node
    {
    public:
        std::shared_ptr<operand> place;

    protected:
        /**
         * \param position Source code position.
         */
        explicit expression(const struct position position);
    };

    /**
     * Symbol definition.
     */
    class definition : public node
    {
        std::string m_identifier;

    protected:
        /**
         * Constructs a definition identified by some name.
         *
         * \param position Source code position.
         * \param identifier Definition name.
         */
        definition(const struct position position, const std::string& identifier);

    public:
        /**
         * \return Definition name.
         */
        std::string& identifier();
    };

    /**
     * Some type expression.
     */
    class type_expression : public node
    {
    public:
        virtual basic_type_expression *is_basic();
        virtual array_type_expression *is_array();
        virtual pointer_type_expression *is_pointer();
        virtual record_type_expression *is_record();
        virtual union_type_expression *is_union();

    protected:
        type_expression(const struct position position);
    };

    /**
     * Expression defining a basic type.
     */
    class basic_type_expression final : public type_expression
    {
        const std::string m_name;

    public:
        /**
         * \param position Source code position.
         * \param name Type name.
         */
        basic_type_expression(const struct position position, const std::string& name);
        virtual void accept(parser_visitor *visitor) override;

        const std::string& base_name();

        basic_type_expression *is_basic() override;
    };

    class array_type_expression final : public type_expression
    {
        type_expression *m_base;

    public:
        const std::uint32_t size;

        array_type_expression(const struct position position, type_expression *base, const std::uint32_t size);
        virtual void accept(parser_visitor *visitor) override;

        type_expression& base();

        array_type_expression *is_array() override;

        virtual ~array_type_expression() override;
    };

    class pointer_type_expression final : public type_expression
    {
        type_expression *m_base;

    public:
        pointer_type_expression(const struct position position, type_expression *base);
        virtual void accept(parser_visitor *visitor) override;

        type_expression& base();

        pointer_type_expression *is_pointer() override;

        virtual ~pointer_type_expression() override;
    };

    using field_t = std::pair<std::string, type_expression *>;
    using fields_t = std::vector<field_t>;

    class composite_type_expression : public type_expression
    {
    protected:
        composite_type_expression(const struct position position, fields_t&& fields);

    public:
        fields_t fields;

        virtual ~composite_type_expression() override;
    };

    class record_type_expression final : public composite_type_expression
    {
    public:
        record_type_expression(const struct position position, fields_t&& fields);

        virtual void accept(parser_visitor *visitor) override;
        record_type_expression *is_record() override;
    };

    class union_type_expression final : public composite_type_expression
    {
    public:
        union_type_expression(const struct position position, fields_t&& fields);

        virtual void accept(parser_visitor *visitor) override;
        union_type_expression *is_union() override;
    };

    /**
     * Variable declaration.
     */
    class variable_declaration : public definition
    {
        type_expression *m_type;

    public:
        /**
         * Constructs a declaration with a name and a type.
         *
         * \param position Source code position.
         * \param identifier Definition name.
         * \param type Declared type.
         */
        variable_declaration(const struct position position, const std::string& identifier,
                type_expression *type);
        virtual void accept(parser_visitor *visitor) override;

        type_expression& type();

        virtual ~variable_declaration() override;
    };

    class literal : public expression
    {
    protected:
        explicit literal(const struct position position);
    };

    /**
     * Constant definition.
     */
    class constant_definition : public definition
    {
        literal *m_body;

    public:
        /**
         * \param position Source code position.
         * \param identifier Constant name.
         * \param body Constant value.
         */
        constant_definition(const struct position position, const std::string& identifier,
                literal *body);
        virtual void accept(parser_visitor *visitor) override;

        literal& body();

        virtual ~constant_definition() override;
    };

    /**
     * Procedure definition.
     */
    class procedure_definition : public definition
    {
        type_expression *m_return_type{ nullptr };
        block *m_body{ nullptr };

    public:
        std::vector<variable_declaration *> parameters;

        /**
         * \param position Source code position.
         * \param identifier Procedure name.
         * \param parameters Procedure formal parameters.
         * \param return_type Return type if any.
         * \param body Procedure body.
         */
        procedure_definition(const struct position position, const std::string& identifier,
                std::vector<variable_declaration *>&& parameters,
                type_expression *return_type = nullptr, block *body = nullptr);
        virtual void accept(parser_visitor *visitor) override;

        type_expression *return_type();
        block *body();

        virtual ~procedure_definition() override;
    };

    class type_definition : public definition
    {
        type_expression *m_body;

    public:
        type_definition(const struct position position, const std::string& identifier,
                type_expression *expression);
        virtual void accept(parser_visitor *visitor) override;

        type_expression& body();

        virtual ~type_definition() override;
    };

    /**
     * Call statement.
     */
    class call_expression : public expression
    {
        std::string m_name;
        std::vector<expression *> m_arguments;

    public:
        /**
         * \param position Source code position.
         * \param name Callable's name.
         */
        call_expression(const struct position position, const std::string& name);
        virtual void accept(parser_visitor *visitor) override;

        std::string& name();
        std::vector<expression *>& arguments();

        virtual ~call_expression() override;
    };

    class expression_statement : public statement
    {
        expression *m_body;

    public:
        expression_statement(const struct position position, expression *body);
        virtual void accept(parser_visitor *visitor) override;

        expression& body();

        virtual ~expression_statement() override;
    };

    /**
     * List of statements paired with a condition.
     */
    class conditional_statements
    {
        expression *m_prerequisite;

    public:
        std::vector<statement *> statements;

        conditional_statements(expression *prerequisite);

        expression& prerequisite();

        virtual ~conditional_statements();
    };

    class return_statement : public statement
    {
        expression *m_return_expression{ nullptr };

    public:
        return_statement(const struct position position, expression *return_expression);
        virtual void accept(parser_visitor *visitor) override;

        expression *return_expression();

        virtual ~return_statement() override;
    };

    class designator_expression : public expression
    {
    public:
        virtual variable_expression *is_variable();
        virtual array_access_expression *is_array_access();
        virtual field_access_expression *is_field_access();
        virtual dereference_expression *is_dereference();

    protected:
        designator_expression(const struct position position);
    };

    class variable_expression : public designator_expression
    {
        std::string m_name;

    public:
        variable_expression(const struct position position, const std::string& name);
        virtual void accept(parser_visitor *visitor) override;

        const std::string& name() const;

        variable_expression *is_variable() override;
    };

    class array_access_expression : public designator_expression
    {
        designator_expression *m_base;
        expression *m_index;

    public:
        array_access_expression(const struct position position, designator_expression *base, expression *index);
        virtual void accept(parser_visitor *visitor) override;

        designator_expression& base();
        expression& index();

        array_access_expression *is_array_access() override;

        ~array_access_expression() override;
    };

    class field_access_expression : public designator_expression
    {
        designator_expression *m_base;
        std::string m_field;

    public:
        field_access_expression(const struct position position, designator_expression *base,
                const std::string& field);
        virtual void accept(parser_visitor *visitor) override;

        designator_expression& base();
        std::string& field();

        field_access_expression *is_field_access() override;

        ~field_access_expression() override;
    };

    class dereference_expression : public designator_expression
    {
        designator_expression *m_base;

    public:
        dereference_expression(const struct position position, designator_expression *base);
        virtual void accept(parser_visitor *visitor) override;

        designator_expression& base();

        dereference_expression *is_dereference() override;

        ~dereference_expression() override;
    };

    class assign_statement : public statement
    {
        designator_expression *m_lvalue;
        expression *m_rvalue;

    public:
        /**
         * \param position Source code position.
         * \param lvalue Left-hand side.
         * \param rvalue Assigned expression.
         */
        assign_statement(const struct position position, designator_expression *lvalue,
                expression *rvalue);
        virtual void accept(parser_visitor *visitor) override;

        designator_expression& lvalue();
        expression& rvalue();

        virtual ~assign_statement() override;
    };

    /**
     * If-statement.
     */
    class if_statement : public statement
    {
        conditional_statements *m_body;
        std::vector<statement *> *m_alternative;

    public:
        if_statement(const struct position position, conditional_statements *body,
                std::vector<statement *> *alternative = nullptr);
        virtual void accept(parser_visitor *visitor) override;

        conditional_statements& body();
        std::vector<statement *> *alternative();

        virtual ~if_statement() override;
    };

    /**
     * While-statement.
     */
    class while_statement : public statement
    {
        conditional_statements *m_body;

    public:
        while_statement(const struct position position, conditional_statements *body);
        virtual void accept(parser_visitor *visitor) override;

        conditional_statements& body();

        virtual ~while_statement() override;
    };

    class block : public node
    {
    public:
        std::vector<definition *> value_definitions;
        std::vector<statement *> body;

        block(const struct position position, std::vector<definition *>&& value_definitions,
                std::vector<statement *>&& body);
        virtual void accept(parser_visitor *visitor) override;

        virtual ~block() override;
    };

    class program : public block
    {
    public:
        std::vector<definition *> type_definitions;

        program(const struct position position, std::vector<definition *>&& type_definitions,
                std::vector<definition *>&& value_definitions, std::vector<statement *>&& body);
        virtual void accept(parser_visitor *visitor) override;

        virtual ~program() override;
    };

    template<typename T>
    class number_literal : public literal
    {
        T m_number;

    public:
        number_literal(const struct position position, const T value)
            : literal(position), m_number(value)
        {
        }

        virtual void accept(parser_visitor *visitor) override
        {
            visitor->visit(this);
        }

        T number() const
        {
            return m_number;
        }
    };

    class string_literal : public literal
    {
        std::string m_string;

    public:
        string_literal(const struct position position, const std::string& value);
        virtual void accept(parser_visitor *visitor) override;

        const std::string& string() const;
    };

    class binary_expression : public expression
    {
        expression *m_lhs;
        expression *m_rhs;
        binary_operator m_operator;

    public:
        binary_expression(const struct position position, expression *lhs,
                expression *rhs, const binary_operator operation);

        virtual void accept(parser_visitor *visitor) override;
        expression& lhs();
        expression& rhs();
        binary_operator operation() const;

        virtual ~binary_expression() override;
    };

    class unary_expression : public expression
    {
        expression *m_operand;
        unary_operator m_operator;

    public:
        unary_expression(const struct position position, expression *operand,
                const unary_operator operation);

        virtual void accept(parser_visitor *visitor) override;
        expression& operand();
        unary_operator operation() const;

        virtual ~unary_expression() override;
    };

    const char *print_binary_operator(const binary_operator operation);
}
}