Compiler_Module_Linker.H

/*
                          Aleph_w

  Data structures & Algorithms
  version 2.0.0b
  https://github.com/lrleon/Aleph-w

  This file is part of Aleph-w library

  Copyright (c) 2002-2026 Leandro Rabindranath Leon

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  of this software and associated documentation files (the "Software"), to deal
  in the Software without restriction, including without limitation the rights
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  copies of the Software, and to permit persons to whom the Software is
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*/

/** @file Compiler_Module_Linker.H
 *  @brief Reusable linking helpers for module surfaces and direct imports.
 *
 *  This header links `Compiler_Module_Descriptor` and `Compiler_Module_Metadata`
 *  into a direct-import view showing which top-level declarations are visible to
 *  each module from itself and its immediate imports. It also reports duplicate
 *  visible names across the current value or type namespace.
 *
 *  @ingroup Utilities
 */

#ifndef COMPILER_MODULE_LINKER_H
#define COMPILER_MODULE_LINKER_H

#include <sstream>
#include <string>

#include <tpl_dynMapTree.H>
#include <Compiler_Module_Metadata.H>
#include <Compiler_Module_Resolver.H>

namespace Aleph {
/** @brief One visible top-level declaration in a linked module surface. */
struct Compiler_Module_Visible_Export
{
  Compiler_Module_Export_Kind kind = Compiler_Module_Export_Kind::Global;
  std::string name;
  size_t source_module_index = static_cast<size_t>(-1);  ///< Index in the descriptor/module array.
  std::string source_module_name;
  Source_Span declaration_span;
  bool imported = false;  ///< `false` for local exports, `true` for direct-imported exports.
};

/** @brief One linked module view under direct-import surface rules. */
struct Compiler_Module_Linkage
{
  std::string module_name;
  size_t module_index = static_cast<size_t>(-1);
  size_t order_index = static_cast<size_t>(-1);
  DynArray<size_t> direct_import_indexes;
  DynArray<Compiler_Module_Visible_Export> visible_exports;
};

/** @brief Structural issues emitted while linking module surfaces. */
enum class Compiler_Module_Linkage_Issue_Kind
{
  Missing_Metadata,
  Duplicate_Value_Export,
  Duplicate_Type_Export
};

/** @brief One structural issue reported by the reusable module linker. */
struct Compiler_Module_Linkage_Issue
{
  Compiler_Module_Linkage_Issue_Kind kind = Compiler_Module_Linkage_Issue_Kind::Missing_Metadata;
  size_t module_index = static_cast<size_t>(-1);
  std::string module_name;
  std::string export_name;
  std::string first_provider_module;
  std::string second_provider_module;
  Source_Span span;
};

/** @brief Link result over module descriptors and module metadata. */
struct Compiler_Module_Link_Result
{
  bool valid = true;
  DynArray<Compiler_Module_Linkage> modules;
  DynArray<Compiler_Module_Linkage_Issue> issues;
};

/** @brief Returns the stable debug name for one linkage issue kind. */
inline const char *compiler_module_linkage_issue_name(const Compiler_Module_Linkage_Issue_Kind kind) noexcept
{
  switch (kind)
    {
    case Compiler_Module_Linkage_Issue_Kind::Missing_Metadata:
      return "Missing_Metadata";
    case Compiler_Module_Linkage_Issue_Kind::Duplicate_Value_Export:
      return "Duplicate_Value_Export";
    case Compiler_Module_Linkage_Issue_Kind::Duplicate_Type_Export:
      return "Duplicate_Type_Export";
    }

  return "Unknown";
}

namespace Compiler_Module_Linker_Detail {
inline size_t find_metadata_index(const DynArray<Compiler_Module_Metadata> &metadata,
                                  const std::string &name) noexcept
{
  for (size_t i = 0; i < metadata.size(); ++i)
    if (metadata.access(i).name == name)
      return i;
  return static_cast<size_t>(-1);
}

inline int export_namespace_bucket(const Compiler_Module_Export_Kind kind) noexcept
{
  return kind == Compiler_Module_Export_Kind::Type ? 1 : 0;
}
}  // namespace Compiler_Module_Linker_Detail

/** @brief Links direct-import module surfaces into visible top-level views. */
inline Compiler_Module_Link_Result compiler_link_module_surfaces(
  const DynArray<Compiler_Module_Descriptor> &descriptors,
  const DynArray<Compiler_Module_Metadata> &metadata,
  const DynArray<size_t> &order)
{
  Compiler_Module_Link_Result result;

  for (size_t order_pos = 0; order_pos < order.size(); ++order_pos)
    {
      const auto module_index = order.access(order_pos);
      if (module_index >= descriptors.size())
        continue;

      const auto &descriptor = descriptors.access(module_index);
      Compiler_Module_Linkage linkage;
      linkage.module_name = descriptor.name;
      linkage.module_index = module_index;
      linkage.order_index = order_pos;

      const auto self_metadata_index
        = Compiler_Module_Linker_Detail::find_metadata_index(metadata, descriptor.name);
      if (self_metadata_index == static_cast<size_t>(-1))
        {
          result.valid = false;
          result.issues.append({Compiler_Module_Linkage_Issue_Kind::Missing_Metadata,
                                module_index,
                                descriptor.name,
                                "",
                                "",
                                descriptor.name,
                                {}});
          result.modules.append(std::move(linkage));
          continue;
        }

      const auto &self_metadata = metadata.access(self_metadata_index);
      for (size_t i = 0; i < self_metadata.exports.size(); ++i)
        {
          const auto &item = self_metadata.exports.access(i);
          linkage.visible_exports.append(
            {item.kind, item.name, module_index, self_metadata.name, item.declaration_span, false});
        }

      for (size_t i = 0; i < descriptor.imports.size(); ++i)
        {
          const auto &dep = descriptor.imports.access(i);
          const auto dep_index = [&descriptors, &dep]() {
            for (size_t descriptor_index = 0; descriptor_index < descriptors.size(); ++descriptor_index)
              if (descriptors.access(descriptor_index).name == dep.module_name)
                return descriptor_index;
            return static_cast<size_t>(-1);
          }();
          if (dep_index == static_cast<size_t>(-1))
            continue;
          linkage.direct_import_indexes.append(dep_index);

          const auto dep_metadata_index
            = Compiler_Module_Linker_Detail::find_metadata_index(metadata, dep.module_name);
          if (dep_metadata_index == static_cast<size_t>(-1))
            {
              result.valid = false;
              result.issues.append({Compiler_Module_Linkage_Issue_Kind::Missing_Metadata,
                                    module_index,
                                    descriptor.name,
                                    dep.module_name,
                                    "",
                                    dep.module_name,
                                    dep.span});
              continue;
            }

          const auto &dep_metadata = metadata.access(dep_metadata_index);
          for (size_t j = 0; j < dep_metadata.exports.size(); ++j)
            {
              const auto &item = dep_metadata.exports.access(j);
              linkage.visible_exports.append(
                {item.kind, item.name, dep_index, dep_metadata.name, item.declaration_span, true});
            }
        }

      {
        // Single-pass O(N) duplicate detection keyed by (bucket, name).
        // bucket 1 = Type namespace, bucket 0 = Value namespace.
        DynMapTree<std::string, size_t> first_seen; // key -> index into visible_exports
        for (size_t i = 0; i < linkage.visible_exports.size(); ++i)
          {
            const auto &exp = linkage.visible_exports.access(i);
            const std::string key = std::to_string(
              Compiler_Module_Linker_Detail::export_namespace_bucket(exp.kind)) + ":" + exp.name;
            const auto *prev_idx = first_seen.search(key);
            if (prev_idx == nullptr)
              {
                first_seen[key] = i;
                continue;
              }
            const auto &prev = linkage.visible_exports.access(prev_idx->second);
            if (prev.source_module_name == exp.source_module_name and prev.imported == exp.imported)
              continue;
            result.valid = false;
            result.issues.append({exp.kind == Compiler_Module_Export_Kind::Type
                                    ? Compiler_Module_Linkage_Issue_Kind::Duplicate_Type_Export
                                    : Compiler_Module_Linkage_Issue_Kind::Duplicate_Value_Export,
                                  module_index,
                                  descriptor.name,
                                  exp.name,
                                  prev.source_module_name,
                                  exp.source_module_name,
                                  exp.declaration_span});
          }
      }

      result.modules.append(std::move(linkage));
    }

  return result;
}

/** @brief Renders one deterministic text artifact for linked module surfaces. */
inline std::string compiler_render_module_linkage(const Compiler_Module_Link_Result &result)
{
  std::ostringstream out;
  out << "ModuleLinkage\n";
  for (size_t i = 0; i < result.modules.size(); ++i)
    {
      const auto &module = result.modules.access(i);
      out << "  Module(" << module.module_name << ") order=" << module.order_index << '\n';
      for (size_t j = 0; j < module.visible_exports.size(); ++j)
        {
          const auto &item = module.visible_exports.access(j);
          out << "    Visible(" << compiler_module_export_kind_name(item.kind) << "(" << item.name
              << ")) from " << item.source_module_name << (item.imported ? " imported" : " local")
              << '\n';
        }
    }

  if (not result.issues.is_empty())
    {
      out << "  Issues\n";
      for (size_t i = 0; i < result.issues.size(); ++i)
        {
          const auto &issue = result.issues.access(i);
          out << "    " << compiler_module_linkage_issue_name(issue.kind)
              << " module=" << issue.module_name;
          if (not issue.export_name.empty())
            out << " export=" << issue.export_name;
          if (not issue.first_provider_module.empty())
            out << " first=" << issue.first_provider_module;
          if (not issue.second_provider_module.empty())
            out << " second=" << issue.second_provider_module;
          out << '\n';
        }
    }

  return out.str();
}
}  // namespace Aleph

#endif