/* Final validation after constant folding.
   Copyright (C) 2025 Free Software Foundation, Inc.

GCC is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3, or (at your option)
any later version.

GCC is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with GCC; see the file COPYING3.  If not see
<http://www.gnu.org/licenses/>.  */

#include "elna/boot/validation.h"

#include <unordered_map>

namespace elna::boot
{
    validation_error::validation_error(const source_position position, source_position first)
        : diagnostic(position), first(first)
    {
    }

    std::string validation_error::what() const
    {
        return "Duplicate case label";
    }

    std::optional<diagnostic_note> validation_error::note() const
    {
        return previous_declaration_note(this->first, "Previous label here");
    }

    validation_visitor::validation_visitor(symbol_bag& bag, const target_info& target)
        : bag(bag), constant_evaluator(this->bag, target)
    {
    }

    void validation_visitor::visit_statements(const std::vector<statement *>& statements)
    {
        for (statement *const body_statement : statements)
        {
            body_statement->accept(this);
        }
    }

    void validation_visitor::visit(unit *unit)
    {
        for (declaration *unit_declaration : unit->declarations)
        {
            unit_declaration->accept(this);
        }
        if (unit->entry_point.has_value())
        {
            auto entry_point = this->bag.lookup("")->is_procedure();

            this->bag.enter(entry_point->scope);
            visit_statements(unit->entry_point->statements);
            this->bag.leave();
        }
    }

    void validation_visitor::visit(type_declaration *)
    {
    }

    void validation_visitor::visit(variable_declaration *)
    {
    }

    void validation_visitor::visit(procedure_declaration *declaration)
    {
        if (declaration->body.has_value())
        {
            auto procedure = this->bag.lookup(declaration->identifier.name())->is_procedure();
            this->bag.enter(procedure->scope);
            visit_statements(declaration->body.value().statements);
            this->bag.leave();
        }
    }

    void validation_visitor::visit(case_statement *statement)
    {
        for (const switch_case& case_block : statement->cases)
        {
            visit_statements(case_block.statements);
        }
        if (statement->alternative != nullptr)
        {
            visit_statements(*statement->alternative);
        }

        std::unordered_map<constant_value, source_position, constant_value_hash> seen;
        for (const auto& case_block : statement->cases)
        {
            for (auto *label : case_block.labels)
            {
                auto value = this->constant_evaluator.evaluate(*label);
                if (!value.has_value())
                {
                    add_error<non_constant_expression_error>(label->position(),
                            non_constant_expression_error::case_label{});
                    continue;
                }
                auto [case_position, inserted] = seen.try_emplace(value.value(), label->position());
                if (!inserted)
                {
                    add_error<validation_error>(label->position(), case_position->second);
                }
            }
        }
    }

    void validation_visitor::visit(assign_statement *)
    {
    }

    void validation_visitor::visit(if_statement *statement)
    {
        visit_statements(statement->branch().statements);
        for (const conditional_statements *branch : statement->branches)
        {
            visit_statements(branch->statements);
        }
        if (statement->alternative != nullptr)
        {
            visit_statements(*statement->alternative);
        }
    }

    void validation_visitor::visit(while_statement *statement)
    {
        visit_statements(statement->branch().statements);
        for (const conditional_statements *branch : statement->branches)
        {
            visit_statements(branch->statements);
        }
    }

    void validation_visitor::visit(repeat_statement *statement)
    {
        visit_statements(statement->body);
    }

    void validation_visitor::visit(for_statement *statement)
    {
        visit_statements(statement->body);
    }

    void validation_visitor::visit(defer_statement *statement)
    {
        visit_statements(statement->statements);
    }

    void validation_visitor::visit(empty_statement *)
    {
    }

    void validation_visitor::visit(procedure_call *)
    {
    }
}