/* Builtin definitions.
   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 <algorithm>

#include "elna/gcc/elna-builtins.h"
#include "elna/gcc/elna1.h"
#include "stor-layout.h"
#include "stringpool.h"
#include "elna/gcc/elna-tree.h"

namespace elna::gcc
{
    void init_ttree()
    {
        elna_int_type_node = long_integer_type_node;
        elna_word_type_node = size_type_node;
        elna_char_type_node = unsigned_char_type_node;
        elna_pointer_type_node = ptr_type_node;
        elna_float_type_node = double_type_node;

        elna_bool_type_node = boolean_type_node;
        elna_bool_true_node = boolean_true_node;
        elna_bool_false_node = boolean_false_node;

        elna_pointer_nil_node = null_pointer_node;

        elna_string_type_node = make_node(RECORD_TYPE);
        tree string_ptr_type = build_pointer_type_for_mode(elna_char_type_node, VOIDmode, true);

        elna_string_length_field_node = build_field(UNKNOWN_LOCATION,
                elna_string_type_node, "length", build_qualified_type(elna_word_type_node, TYPE_QUAL_CONST));
        elna_string_ptr_field_node = build_field(UNKNOWN_LOCATION,
                elna_string_type_node, "ptr", build_qualified_type(string_ptr_type, TYPE_QUAL_CONST));

        TYPE_FIELDS(elna_string_type_node) = chainon(elna_string_ptr_field_node, elna_string_length_field_node);
        layout_type(elna_string_type_node);
    }

    static
    tree declare_builtin_type(std::shared_ptr<symbol_table> symbol_table, const char *name, tree type)
    {
        tree identifier = get_identifier(name);
        tree type_declaration = build_decl(UNKNOWN_LOCATION, TYPE_DECL, identifier, type);

        TREE_PUBLIC(type_declaration) = 1;

        symbol_table->enter(name, type_declaration);

        return type_declaration;
    }

    std::shared_ptr<symbol_table> builtin_symbol_table()
    {
        std::shared_ptr<elna::gcc::symbol_table> symbol_table = std::make_shared<elna::gcc::symbol_table>();

        declare_builtin_type(symbol_table, "Int", elna_int_type_node);
        declare_builtin_type(symbol_table, "Word", elna_word_type_node);
        declare_builtin_type(symbol_table, "Char", elna_char_type_node);
        declare_builtin_type(symbol_table, "Bool", elna_bool_type_node);
        declare_builtin_type(symbol_table, "Pointer", elna_pointer_type_node);
        declare_builtin_type(symbol_table, "Float", elna_float_type_node);

        tree string_declaration = declare_builtin_type(symbol_table, "String", elna_string_type_node);
        TYPE_NAME(elna_string_type_node) = DECL_NAME(string_declaration);
        TYPE_STUB_DECL(elna_string_type_node) = string_declaration;

        return symbol_table;
    }

    tree build_type_declaration(const std::string& identifier, tree type)
    {
        tree definition_tree = build_decl(UNKNOWN_LOCATION, TYPE_DECL,
                get_identifier(identifier.c_str()), type);

        TREE_PUBLIC(definition_tree) = true;
        if (is_unique_type(type))
        {
            TYPE_NAME(type) = DECL_NAME(definition_tree);
            TYPE_STUB_DECL(type) = definition_tree;
        }
        else
        {
            TYPE_NAME(type) = definition_tree;
        }
        return definition_tree;
    }

    tree build_composite_type(const std::vector<boot::type_field>& fields, tree composite_type_node,
            std::shared_ptr<symbol_table> symbols, std::vector<std::string>& path)
    {
        for (auto& field : fields)
        {
            tree rewritten_field = get_inner_alias(field.second, symbols, path);
            tree field_declaration = build_field(UNKNOWN_LOCATION,
                    composite_type_node, field.first, rewritten_field);
            TYPE_FIELDS(composite_type_node) = chainon(TYPE_FIELDS(composite_type_node), field_declaration);
        }
        layout_type(composite_type_node);
        return composite_type_node;
    }

    tree build_procedure_type(const boot::procedure_type& procedure, std::shared_ptr<symbol_table> symbols,
            std::vector<std::string>& path)
    {
        std::vector<tree> parameter_types(procedure.parameters.size());

        for (std::size_t i = 0; i < procedure.parameters.size(); ++i)
        {
            parameter_types[i] = get_inner_alias(procedure.parameters.at(i), symbols, path);
        }
        tree return_type = void_type_node;

        if (!procedure.return_type.proper_type.empty())
        {
            return_type = get_inner_alias(procedure.return_type.proper_type, symbols, path);
        }
        return build_function_type_array(return_type, procedure.parameters.size(), parameter_types.data());
    }

    tree get_inner_alias(const boot::type& type, std::shared_ptr<symbol_table> symbols, std::vector<std::string>& path)
    {
        if (auto reference = type.get<boot::primitive_type>())
        {
            auto looked_up = symbols->lookup(reference->identifier);
            gcc_assert(looked_up != NULL_TREE);

            return TREE_TYPE(looked_up);
        }
        else if (auto reference = type.get<boot::record_type>())
        {
            tree composite_type_node = make_node(RECORD_TYPE);

            build_composite_type(reference->fields, composite_type_node, symbols, path);

            return composite_type_node;
        }
        else if (auto reference = type.get<boot::union_type>())
        {
            tree composite_type_node = make_node(UNION_TYPE);

            build_composite_type(reference->fields, composite_type_node, symbols, path);

            return composite_type_node;
        }
        else if (auto reference = type.get<boot::enumeration_type>())
        {
            return build_enumeration_type(reference->members);
        }
        else if (auto reference = type.get<boot::pointer_type>())
        {
            return build_global_pointer_type(get_inner_alias(reference->base, symbols, path));
        }
        else if (auto reference = type.get<boot::array_type>())
        {
            tree base = get_inner_alias(reference->base, symbols, path);

            return build_static_array_type(base, reference->size);
        }
        else if (auto reference = type.get<boot::procedure_type>())
        {
            auto procedure = build_procedure_type(*reference, symbols, path);

            return build_global_pointer_type(procedure);
        }
        else if (auto reference = type.get<boot::alias_type>())
        {
            return handle_symbol(reference->name, reference, symbols, path);
        }
        return error_mark_node;
    }

    tree handle_symbol(const std::string& symbol_name, std::shared_ptr<boot::alias_type> reference,
            std::shared_ptr<symbol_table> symbols, std::vector<std::string>& path)
    {
        path.push_back(symbol_name);
        std::vector<std::string>::const_iterator head_peace = std::cbegin(path);

        if (std::find(std::next(head_peace), std::cend(path), *head_peace) != std::cend(path))
        {
            return error_mark_node;
        }
        tree looked_up = symbols->lookup(symbol_name);

        if (looked_up == NULL_TREE)
        {
            looked_up = get_inner_alias(reference->reference, symbols, path);

            symbols->enter(symbol_name, build_type_declaration(symbol_name, looked_up));
        }
        else
        {
            looked_up = TREE_TYPE(looked_up);
        }
        return looked_up;
    }

    void declare_procedure(const std::string& name, const boot::procedure_info& info,
            std::shared_ptr<symbol_table> symbols)
    {
        std::vector<std::string> path;
        tree declaration_type = gcc::build_procedure_type(info.symbol, symbols, path);
        tree fndecl = build_fn_decl(name.c_str(), declaration_type);
        symbols->enter(name, fndecl);

        if (info.symbol.return_type.no_return)
        {
            TREE_THIS_VOLATILE(fndecl) = 1;
        }
        tree resdecl = build_decl(UNKNOWN_LOCATION, RESULT_DECL, NULL_TREE, TREE_TYPE(declaration_type));
        DECL_CONTEXT(resdecl) = fndecl;
        DECL_RESULT(fndecl) = resdecl;

        tree argument_chain = NULL_TREE;
        function_args_iterator parameter_type;
        function_args_iter_init(&parameter_type, declaration_type);

        std::vector<std::string>::const_iterator parameter_name = info.names.cbegin();

        for (boot::type parameter : info.symbol.parameters)
        {
            tree declaration_tree = build_decl(UNKNOWN_LOCATION, PARM_DECL,
                get_identifier(parameter_name->c_str()), function_args_iter_cond(&parameter_type));
            DECL_CONTEXT(declaration_tree) = fndecl;
            DECL_ARG_TYPE(declaration_tree) = function_args_iter_cond(&parameter_type);

            argument_chain = chainon(argument_chain, declaration_tree);
            function_args_iter_next(&parameter_type);
            ++parameter_name;
        }
        DECL_ARGUMENTS(fndecl) = argument_chain;
        TREE_ADDRESSABLE(fndecl) = 1;
        DECL_EXTERNAL(fndecl) = info.symbols == nullptr;
    }

    void do_semantic_analysis(std::shared_ptr<boot::symbol_table> info_table, std::shared_ptr<symbol_table> symbols)
    {
        for (auto& [symbol_name, symbol_info] : *info_table)
        {
            std::vector<std::string> type_path;

            if (auto type_info = symbol_info->is_type())
            {
                // The top level symbol table has basic (builtin) types in it which are not aliases.
                if (auto alias_type = type_info->symbol.get<boot::alias_type>())
                {
                    handle_symbol(symbol_name, alias_type, symbols, type_path);
                }
            }
            else if (auto procedure_info = symbol_info->is_procedure())
            {
                declare_procedure(symbol_name, *procedure_info, symbols);
            }
        }
    }
}