#include "elna/source/parser.hpp"
#include <stdexcept>

namespace elna::source
{
    /**
     * AST node.
     */
    void node::accept(parser_visitor *)
    {
    }

    definition::definition(std::string&& identifier, std::unique_ptr<integer_literal>&& body)
        : m_identifier(std::move(identifier)), m_body(std::move(body))
    {
    }

    void definition::accept(parser_visitor *visitor)
    {
        visitor->visit(this);
    }

    std::string& definition::identifier() noexcept
    {
        return m_identifier;
    }

    integer_literal& definition::body()
    {
        return *m_body;
    }

    block::block(std::vector<std::unique_ptr<definition>>&& definitions, std::unique_ptr<statement>&& body)
        : m_definitions(std::move(definitions)), m_body(std::move(body))
    {
    }

    void block::accept(parser_visitor *visitor)
    {
        visitor->visit(this);
    }

    statement& block::body()
    {
        return *m_body;
    }

    std::vector<std::unique_ptr<definition>>& block::definitions() noexcept
    {
        return m_definitions;
    }

    integer_literal::integer_literal(const std::int32_t value)
        : m_number(value)
    {
    }

    void integer_literal::accept(parser_visitor *visitor)
    {
        visitor->visit(this);
    }

    std::int32_t integer_literal::number() const noexcept
    {
        return m_number;
    }

    variable_expression::variable_expression(const std::string& name)
        : m_name(name)
    {
    }

    void variable_expression::accept(parser_visitor *visitor)
    {
        visitor->visit(this);
    }

    const std::string& variable_expression::name() const noexcept
    {
        return m_name;
    }

    binary_expression::binary_expression(std::unique_ptr<expression>&& lhs,
            std::unique_ptr<expression>&& rhs, const unsigned char operation)
        : m_lhs(std::move(lhs)), m_rhs(std::move(rhs))
    {
        switch (operation)
        {
            case '+':
                this->m_operator = binary_operator::sum;
                break;
            case '-': 
                this->m_operator = binary_operator::subtraction;
                break;
            case '*':
                this->m_operator = binary_operator::multiplication;
                break;
            case '/':
                this->m_operator = binary_operator::division;
                break;
            default:
                throw std::logic_error("Invalid binary operator");
        }
    }

    void binary_expression::accept(parser_visitor *visitor)
    {
        visitor->visit(this);
    }

    expression& binary_expression::lhs()
    {
        return *m_lhs;
    }

    expression& binary_expression::rhs()
    {
        return *m_rhs;
    }

    binary_operator binary_expression::operation() const noexcept
    {
        return m_operator;
    }

    bang_statement::bang_statement(std::unique_ptr<expression>&& body)
        : m_body(std::move(body))
    {
    }

    void bang_statement::accept(parser_visitor *visitor)
    {
        visitor->visit(this);
    }

    expression& bang_statement::body()
    {
        return *m_body;
    }

    parser::parser(const std::vector<token>& tokens)
        : tokens(tokens.cbegin()), end(tokens.cend())
    {
    }

    std::unique_ptr<block> parser::parse()
    {
        return parse_block();
    }

    std::unique_ptr<expression> parser::parse_factor()
    {
        if (tokens->of() == source::token::type::identifier)
        {
            auto result = std::make_unique<variable_expression>(tokens->identifier());
            ++tokens;
            return result;
        }
        else if (tokens->of() == source::token::token::type::number)
        {
            auto result = std::make_unique<integer_literal>(tokens->number());
            ++tokens;
            return result;
        }
        else if (tokens->of() == source::token::type::left_paren)
        {
            ++tokens;

            auto expression = parse_expression();

            ++tokens;

            return expression;
        }
        return nullptr;
    }

    std::unique_ptr<expression> parser::parse_term()
    {
        auto lhs = parse_factor();
        if (lhs == nullptr || tokens == end || tokens->of() != source::token::type::factor_operator)
        {
            return lhs;
        }
        while (tokens->of() == source::token::type::factor_operator)
        {
            auto _operator = tokens->identifier()[0];
            ++tokens;

            auto rhs = parse_factor();
            lhs = std::make_unique<binary_expression>(std::move(lhs),
                    std::move(rhs), _operator);
        }
        return lhs;
    }

    std::unique_ptr<expression> parser::parse_expression()
    {
        auto term = parse_term();
        if (term == nullptr || tokens == end || tokens->of() != source::token::type::term_operator)
        {
            return term;
        }
        while (tokens->of() == source::token::type::term_operator)
        {
            auto _operator = tokens->identifier()[0];
            ++tokens;

            auto rhs = parse_term();
            term = std::make_unique<binary_expression>(std::move(term),
                    std::move(rhs), _operator);
        }
        return term;
    }

    std::unique_ptr<definition> parser::parse_definition()
    {
        std::string definition_identifier = tokens->identifier(); // Copy.

        ++tokens;
        ++tokens; // Skip the equals sign.

        if (tokens->of() == source::token::type::number)
        {
            auto result = std::make_unique<definition>(std::move(definition_identifier),
                    std::make_unique<integer_literal>(tokens->number()));
            ++tokens;
            return result;
        }
        return nullptr;
    }

    std::unique_ptr<statement> parser::parse_bang_statement()
    {
        if (tokens->of() == source::token::type::bang)
        {
            ++tokens;
            auto bang_body = parse_expression();
            if (bang_body != nullptr)
            {
                return std::make_unique<bang_statement>(std::move(bang_body));
            }
        }
        return nullptr;
    }

    std::vector<std::unique_ptr<definition>> parser::parse_definitions()
    {
        ++tokens; // Skip const.

        std::vector<std::unique_ptr<definition>> definitions;

        while (tokens != end)
        {
            auto parsed_definition = parse_definition();
            if (parsed_definition == nullptr)
            {
                return definitions;
            }
            definitions.push_back(std::move(parsed_definition));

            if (tokens->of() == source::token::type::semicolon)
            {
                break;
            }
            if (tokens->of() == source::token::type::comma)
            {
                ++tokens;
            }
        }

        return definitions;
    }

    std::unique_ptr<block> parser::parse_block()
    {
        std::vector<std::unique_ptr<definition>> definitions;
        if (tokens->of() == source::token::type::let)
        {
            definitions = parse_definitions();
            ++tokens;
        }
        auto parsed_statement = parse_bang_statement();
        if (parsed_statement == nullptr)
        {
            return nullptr;
        }
        return std::make_unique<block>(std::move(definitions), std::move(parsed_statement));
    }
}