#include "elna/gcc/elna-generic.h"
#include "elna/gcc/elna-diagnostic.h"

#include "input.h"
#include "cgraph.h"
#include "gimplify.h"
#include "stringpool.h"
#include "diagnostic.h"
#include "realmpfr.h"

namespace elna
{
namespace gcc
{
    void generic_visitor::visit(source::call_statement *statement)
    {
        if (statement->name() != "writei")
        {
            error_at(get_location(&statement->position()),
                    "procedure '%s' not declared",
                    statement->name().c_str());
            return;
        }
        if (statement->arguments().size() != 1)
        {
            error_at(get_location(&statement->position()),
                    "procedure '%s' expects 1 argument, %lu given",
                    statement->name().c_str(), statement->arguments().size());
            return;
        }
        auto& argument = statement->arguments().at(0);
        argument->accept(this);
        auto argument_type = TREE_TYPE(this->current_expression);

        const char *format_number{ nullptr };
        if (argument_type == integer_type_node)
        {
            format_number = "%d\n";
        }
        else if (argument_type == double_type_node)
        {
            format_number = "%f\n";
        }
        else if (argument_type == elna_char_type_node)
        {
            format_number = "%c\n";
        }
        else if (is_string_type(argument_type))
        {
            format_number = "%s\n";
        }
        else
        {
            error_at(get_location(&argument->position()),
                    "invalid argument of type %s for procedure %s",
                    print_type(argument_type), statement->name().c_str());
            this->current_expression = error_mark_node;
            return;
        }
        tree args[] = {
            build_string_literal(strlen(format_number) + 1, format_number),
            this->current_expression
        };
        tree fndecl_type_param[] = {
            build_pointer_type(build_qualified_type(char_type_node, TYPE_QUAL_CONST)) /* const char* */
        };
        tree fndecl_type = build_varargs_function_type_array(integer_type_node, 1, fndecl_type_param);

        tree printf_fn_decl = build_fn_decl("printf", fndecl_type);
        DECL_EXTERNAL(printf_fn_decl) = 1;

        tree printf_fn = build1(ADDR_EXPR, build_pointer_type(fndecl_type), printf_fn_decl);

        tree stmt = build_call_array(integer_type_node, printf_fn, 2, args);

        append_to_statement_list(stmt, &this->current_statements);
        this->current_expression = NULL_TREE;
    }

    void generic_visitor::visit(source::program *program)
    {
        tree main_fndecl_type_param[] = {
            integer_type_node,
            build_pointer_type(build_pointer_type(char_type_node))
        };
        tree main_fndecl_type = build_function_type_array(integer_type_node, 2, main_fndecl_type_param);
        this->main_fndecl = build_fn_decl("main", main_fndecl_type);
        tree resdecl = build_decl(UNKNOWN_LOCATION, RESULT_DECL, NULL_TREE, integer_type_node);
        DECL_CONTEXT(resdecl) = this->main_fndecl;
        DECL_RESULT(this->main_fndecl) = resdecl;
        tree set_result = build2(INIT_EXPR, void_type_node, DECL_RESULT(main_fndecl),
                build_int_cst_type(integer_type_node, 0));
        tree return_stmt = build1(RETURN_EXPR, void_type_node, set_result);
       
        enter_scope();

        empty_visitor::visit(program);
        append_to_statement_list(return_stmt, &this->current_statements);

        tree_symbol_mapping mapping = leave_scope();
       
        BLOCK_SUPERCONTEXT(mapping.block()) = this->main_fndecl;
        DECL_INITIAL(this->main_fndecl) = mapping.block();
        DECL_SAVED_TREE(this->main_fndecl) = mapping.bind_expression();
       
        DECL_EXTERNAL(this->main_fndecl) = 0;
        DECL_PRESERVE_P(this->main_fndecl) = 1;
       
        gimplify_function_tree(this->main_fndecl);
       
        cgraph_node::finalize_function(this->main_fndecl, true);
    }

    void generic_visitor::enter_scope()
    {
        this->current_statements = alloc_stmt_list();
        this->variable_chain = tree_chain();
    }

    tree_symbol_mapping generic_visitor::leave_scope()
    {
        tree new_block = build_block(variable_chain.head(),
                NULL_TREE, NULL_TREE, NULL_TREE);
        tree bind_expr = build3(BIND_EXPR, void_type_node, variable_chain.head(),
                this->current_statements, new_block);

        return tree_symbol_mapping{ bind_expr, new_block };
    }

    void generic_visitor::visit(source::number_literal<std::int32_t> *literal)
    {
        this->current_expression = build_int_cst_type(integer_type_node, literal->number());
    }

    void generic_visitor::visit(source::number_literal<double> *literal)
    {
        REAL_VALUE_TYPE real_value1;

        mpfr_t number;
        mpfr_init2(number, SIGNIFICAND_BITS);
        mpfr_set_d(number, literal->number(), MPFR_RNDN);

        real_from_mpfr(&real_value1, number, double_type_node, MPFR_RNDN);

        this->current_expression = build_real(double_type_node, real_value1);

        mpfr_clear(number);
    }

    void generic_visitor::visit(source::number_literal<bool> *boolean)
    {
        this->current_expression = build_int_cst_type(boolean_type_node, boolean->number());
    }

    void generic_visitor::visit(source::char_literal *character)
    {
        this->current_expression = build_int_cstu(elna_char_type_node, character->character());
    }

    void generic_visitor::visit(source::string_literal *string)
    {
        this->current_expression = build_string_literal(string->string().size() + 1, string->string().c_str());
    }

    void generic_visitor::visit(source::binary_expression *expression)
    {
        expression->lhs().accept(this);
        auto left = this->current_expression;
        auto left_type = TREE_TYPE(left);

        expression->rhs().accept(this);
        auto right = this->current_expression;
        auto right_type = TREE_TYPE(right);

        auto expression_location = get_location(&expression->position());
        tree_code operator_code = ERROR_MARK;
        tree target_type = error_mark_node;

        if (left_type != right_type)
        {
            error_at(expression_location,
                    "invalid operands of type %s and %s for operator %s",
                    print_type(left_type), print_type(right_type),
                    elna::source::print_binary_operator(expression->operation()));
            this->current_expression = error_mark_node;
            return;
        }
        switch (expression->operation())
        {
            case source::binary_operator::sum:
                operator_code = PLUS_EXPR;
                target_type = left_type;
                break;
            case source::binary_operator::subtraction:
                operator_code = MINUS_EXPR;
                target_type = left_type;
                break;
            case source::binary_operator::division:
                operator_code = TRUNC_DIV_EXPR;
                target_type = left_type;
                break;
            case source::binary_operator::multiplication:
                operator_code = MULT_EXPR;
                target_type = left_type;
                break;
            default:
                break;
        }
        if (operator_code != ERROR_MARK) // An arithmetic operation.
        {
            if (target_type != integer_type_node && target_type != double_type_node)
            {
                error_at(expression_location,
                        "invalid operands of type %s and %s for operator %s",
                        print_type(left_type), print_type(right_type),
                        elna::source::print_binary_operator(expression->operation()));
                this->current_expression = error_mark_node;
                return;
            }
        }
        switch (expression->operation())
        {
            case source::binary_operator::equals:
                operator_code = EQ_EXPR;
                target_type = boolean_type_node;
                break;
            case source::binary_operator::not_equals:
                operator_code = NE_EXPR;
                target_type = boolean_type_node;
                break;
            case source::binary_operator::less:
                operator_code = LT_EXPR;
                target_type = boolean_type_node;
                break;
            case source::binary_operator::greater:
                operator_code = GT_EXPR;
                target_type = boolean_type_node;
                break;
            case source::binary_operator::less_equal:
                operator_code = LE_EXPR;
                target_type = boolean_type_node;
                break;
            case source::binary_operator::greater_equal:
                operator_code = GE_EXPR;
                target_type = boolean_type_node;
                break;
            default:
                break;
        }
        gcc_assert(operator_code != ERROR_MARK);
        gcc_assert(target_type != error_mark_node);

        this->current_expression = build2_loc(expression_location,
                operator_code, target_type, left, right);
    }

    void generic_visitor::visit(source::constant_definition *definition)
    {
        location_t definition_location = get_location(&definition->position());
        tree definition_tree = build_decl(definition_location, CONST_DECL,
                get_identifier(definition->identifier().c_str()), integer_type_node);
        auto result = this->symbol_map.insert({ definition->identifier(), definition_tree });

        if (result.second)
        {
            definition->body().accept(this);

            DECL_INITIAL(definition_tree) = build_int_cst_type(integer_type_node, definition->body().number());
            TREE_CONSTANT(definition_tree) = 1;
            TREE_READONLY(definition_tree) = 1;

            auto declaration_statement = build1_loc(definition_location, DECL_EXPR,
                    void_type_node, definition_tree);
            append_to_statement_list(declaration_statement, &this->current_statements);
        }
        else
        {
            error_at(definition_location,
                    "variable '%s' already declared in this scope",
                    definition->identifier().c_str());
        }
        this->current_expression = NULL_TREE;
    }

    void generic_visitor::visit(source::declaration *declaration)
    {
        tree declaration_type = error_mark_node;
        source::basic_type_expression *basic_type = declaration->type().is_basic();

        gcc_assert(basic_type != nullptr);

        if (basic_type->base() == "Int")
        {
            declaration_type = integer_type_node;
        }
        else if (basic_type->base() == "Bool")
        {
            declaration_type = boolean_type_node;
        }
        else if (basic_type->base() == "Float")
        {
            declaration_type = double_type_node;
        }
        else if (basic_type->base() == "Char")
        {
            declaration_type = elna_char_type_node;
        }
        else if (basic_type->base() == "String")
        {
            declaration_type = elna_string_type_node;
        }
        else
        {
            error_at(get_location(&declaration->type().position()),
                    "type '%s' not declared", basic_type->base().c_str());
            return;
        }
        auto declaration_location = get_location(&declaration->position());
        tree declaration_tree = build_decl(declaration_location, VAR_DECL,
                get_identifier(declaration->identifier().c_str()), declaration_type);
        auto result = this->symbol_map.insert({ declaration->identifier(), declaration_tree });

        if (result.second)
        {
            DECL_CONTEXT(declaration_tree) = this->main_fndecl;
            variable_chain.append(declaration_tree);

            auto declaration_statement = build1_loc(declaration_location, DECL_EXPR,
                    void_type_node, declaration_tree);
            append_to_statement_list(declaration_statement, &this->current_statements);
        }
        else
        {
            error_at(declaration_location,
                    "variable '%s' already declared in this scope",
                    declaration->identifier().c_str());
        }
    }

    void generic_visitor::visit(source::variable_expression *expression)
    {
        auto symbol = this->symbol_map.find(expression->name());

        if (symbol == this->symbol_map.end())
        {
            error_at(get_location(&expression->position()),
                    "variable '%s' not declared in the current scope",
                    expression->name().c_str());
            this->current_expression = error_mark_node;
            return;
        }
        this->current_expression = symbol->second;
    }

    void generic_visitor::visit(source::assign_statement *statement)
    {
        auto lvalue = this->symbol_map.find(statement->lvalue());
        auto statement_location = get_location(&statement->position());

        if (lvalue == this->symbol_map.end())
        {
            error_at(statement_location,
                    "variable '%s' not declared in the current scope",
                    statement->lvalue().c_str());
            return;
        }
        statement->rvalue().accept(this);

        if (TREE_CODE(lvalue->second) == CONST_DECL)
        {
            error_at(statement_location, "cannot modify constant '%s'",
                    statement->lvalue().c_str());
            this->current_expression = error_mark_node;
            return;
        }
        if (TREE_TYPE(this->current_expression) != TREE_TYPE(lvalue->second))
        {
            error_at(statement_location,
                    "cannot assign value of type %s to variable '%s' of type %s",
                    print_type(TREE_TYPE(this->current_expression)),
                    statement->lvalue().c_str(),
                    print_type(TREE_TYPE(lvalue->second)));
            this->current_expression = error_mark_node;
            return;
        }
        auto assignment = build2_loc(statement_location, MODIFY_EXPR,
                void_type_node, lvalue->second, this->current_expression);

        append_to_statement_list(assignment, &this->current_statements);
        this->current_expression = NULL_TREE;
    }

    void generic_visitor::visit(source::if_statement *statement)
    {
        statement->prerequisite().accept(this);

        if (TREE_TYPE(this->current_expression) != boolean_type_node)
        {
            error_at(get_location(&statement->prerequisite().position()),
                    "expected expression of boolean type but its type is %s",
                    print_type(TREE_TYPE(this->current_expression)));
            this->current_expression = error_mark_node;
            return;
        }
        auto then_location = get_location(&statement->body().position());
        auto prerequisite_location = get_location(&statement->prerequisite().position());

        auto then_label_decl = build_label_decl("then", then_location);
        auto endif_label_decl = build_label_decl("end_if", then_location);

        auto goto_then = build1_loc(prerequisite_location, GOTO_EXPR,
                void_type_node, then_label_decl);
        auto goto_endif = build1_loc(prerequisite_location, GOTO_EXPR,
                void_type_node, endif_label_decl);

        tree else_label_decl = NULL_TREE;
        tree goto_else_or_endif = NULL_TREE;
        if (statement->alternative() != nullptr)
        {
            auto else_location = get_location(&statement->alternative()->position());
            else_label_decl = build_label_decl("else", else_location);
            goto_else_or_endif = build1_loc(else_location, GOTO_EXPR, void_type_node, else_label_decl);
        }
        else
        {
            goto_else_or_endif = goto_endif;
        }

        auto cond_expr = build3_loc(prerequisite_location, COND_EXPR,
                void_type_node, this->current_expression, goto_then, goto_else_or_endif);
        append_to_statement_list(cond_expr, &this->current_statements);

        auto then_label_expr = build1_loc(then_location, LABEL_EXPR,
                void_type_node, then_label_decl);
        append_to_statement_list(then_label_expr, &this->current_statements);

        statement->body().accept(this);

        if (statement->alternative() != nullptr)
        {
            auto else_label_expr = build1(LABEL_EXPR, void_type_node, else_label_decl);
            append_to_statement_list(else_label_expr, &this->current_statements);

            statement->alternative()->accept(this);
        }
        auto endif_label_expr = build1(LABEL_EXPR, void_type_node, endif_label_decl);
        append_to_statement_list(endif_label_expr, &this->current_statements);

        this->current_expression = NULL_TREE;
    }

    tree generic_visitor::build_label_decl(const char *name, location_t loc)
    {
        auto label_decl = build_decl(loc,
                LABEL_DECL, get_identifier(name), void_type_node);

        DECL_CONTEXT(label_decl) = this->main_fndecl;

        return label_decl;
    }

    void generic_visitor::visit(source::while_statement *statement)
    {
        statement->prerequisite().accept(this);

        if (TREE_TYPE(this->current_expression) != boolean_type_node)
        {
            error_at(get_location(&statement->prerequisite().position()),
                    "expected expression of boolean type but its type is %s",
                    print_type(TREE_TYPE(this->current_expression)));
            this->current_expression = error_mark_node;
            return;
        }
        auto prerequisite_location = get_location(&statement->prerequisite().position());
        auto body_location = get_location(&statement->body().position());

        auto prerequisite_label_decl = build_label_decl("while_check", prerequisite_location);
        auto prerequisite_label_expr = build1_loc(prerequisite_location, LABEL_EXPR,
                void_type_node, prerequisite_label_decl);
        append_to_statement_list(prerequisite_label_expr, &this->current_statements);

        auto body_label_decl = build_label_decl("while_body", body_location);
        auto end_label_decl = build_label_decl("end_while", UNKNOWN_LOCATION);

        auto goto_body = build1_loc(prerequisite_location, GOTO_EXPR,
                void_type_node, body_label_decl);
        auto goto_end = build1_loc(prerequisite_location, GOTO_EXPR,
                void_type_node, end_label_decl);

        auto cond_expr = build3_loc(prerequisite_location, COND_EXPR,
                void_type_node, this->current_expression, goto_body, goto_end);
        append_to_statement_list(cond_expr, &this->current_statements);

        auto body_label_expr = build1_loc(body_location, LABEL_EXPR,
                void_type_node, body_label_decl);
        append_to_statement_list(body_label_expr, &this->current_statements);

        statement->body().accept(this);

        auto goto_check = build1(GOTO_EXPR, void_type_node, prerequisite_label_decl);
        append_to_statement_list(goto_check, &this->current_statements);

        auto endif_label_expr = build1(LABEL_EXPR, void_type_node, end_label_decl);
        append_to_statement_list(endif_label_expr, &this->current_statements);

        this->current_expression = NULL_TREE;
    }
}
}