fastGraph_tpl.h

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 *   Copyright (c) 2005-2026 by                                             *
 *       - Pierre-Henri WUILLEMIN(_at_LIP6)                                 *
 *       - Christophe GONZALES(_at_AMU)                                     *
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 *       - Pierre-Henri WUILLEMIN(_at_LIP6)                                 *
 *       - Christophe GONZALES(_at_AMU)                                     *
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#pragma once
 
#include <algorithm>
#include <cstdint>
#include <string>
#include <utility>
#include <vector>
 
#include <agrum/base/graphs/fastGraph.h>
 
#include <agrum/base/core/utils_string.h>
 
namespace gum {
 
  namespace detail {

    enum class FastGraphOp : std::uint8_t { None, Arc, RevArc, Edge };

    inline std::size_t fastGraphFindDash(std::string_view chain, std::size_t from) {
      int depth = 0;
      for (std::size_t i = from; i < chain.size(); ++i) {
        const char c = chain[i];
        if (c == '[' || c == '{') {
          ++depth;
        } else if (c == ']' || c == '}') {
          if (depth > 0) --depth;
        } else if ((c == '-') && (depth == 0)) {
          return i;
        }
      }
      return std::string_view::npos;
    }

    inline std::vector< std::pair< std::string, FastGraphOp > >
        fastGraphTokenize(std::string_view chain) {
      std::vector< std::pair< std::string, FastGraphOp > > tokens;
      std::size_t                                          pos       = 0;
      FastGraphOp                                          pendingOp = FastGraphOp::None;
 
      while (pos <= chain.size()) {
        const auto dashPos = fastGraphFindDash(chain, pos);
 
        std::size_t opStart = dashPos;
        std::size_t opLen   = 1;
        FastGraphOp op      = FastGraphOp::Edge;
 
        if (dashPos != std::string_view::npos) {
          if ((dashPos + 1 < chain.size()) && (chain[dashPos + 1] == '>')) {
            opLen = 2;
            op    = FastGraphOp::Arc;
          } else if ((dashPos > pos) && (chain[dashPos - 1] == '<')) {
            opStart = dashPos - 1;
            opLen   = 2;
            op      = FastGraphOp::RevArc;
          }
        }
 
        const auto tokEnd = (dashPos == std::string_view::npos) ? chain.size() : opStart;
 
        tokens.emplace_back(trim_copy(chain.substr(pos, tokEnd - pos)), pendingOp);
 
        if (dashPos == std::string_view::npos) { break; }
        pendingOp = op;
        pos       = opStart + opLen;
      }
      return tokens;
    }

    inline bool fastGraphIsNodeIdToken(const std::string& token) {
      int value = 0;
      return isIntegerWithResult(token, &value) && (value >= 0);
    }

    template < typename GRAPH_TYPE >
    NodeId fastGraphBuildNode(GRAPH_TYPE& g, const std::string& token, bool useIds) {
      if (useIds) {
        int value = 0;
        isIntegerWithResult(token, &value);
        const auto id = static_cast< NodeId >(value);
        if (!g.existsNode(id)) { g.addNodeWithId(id); }
        return id;
      }
 
      if (const auto id = g.idFromName(token)) { return *id; }
      const NodeId id = g.addNode();
      g.setName(id, token);
      return id;
    }

    template < typename Resolve, typename AddArc, typename AddEdge >
    void fastGraphWalkTokens(const std::vector< std::pair< std::string, FastGraphOp > >& tokens,
                             std::string_view                                            desc,
                             Resolve                                                     resolve,
                             AddArc                                                      addArc,
                             AddEdge                                                     addEdge) {
      NodeId lastId = 0;
      bool   first  = true;
 
      for (const auto& [token, op]: tokens) {
        if (token.empty()) {
          GUM_ERROR(InvalidArc,
                    "fastGraph: malformed description '" << desc
                                                         << "' (operator without a node token)")
        }
        const NodeId id = resolve(token);
 
        if (!first) {
          if (op == FastGraphOp::Arc) {
            addArc(lastId, id, token);
          } else if (op == FastGraphOp::RevArc) {
            addArc(id, lastId, token);
          } else {
            addEdge(lastId, id, token);
          }
        }
 
        lastId = id;
        first  = false;
      }
    }
 
  }   // namespace detail
 
  template < GUM_NodeGraphable GRAPH_TYPE >
  GRAPH_TYPE fastGraph(std::string_view desc) {
    using namespace detail;
 
    std::vector< std::vector< std::pair< std::string, FastGraphOp > > > chains;
    bool                                                                useIds = true;
 
    for (const auto& chainStr: split(remove_newline(desc), ";")) {
      if (trim_copy(chainStr).empty()) { continue; }
 
      auto tokens = fastGraphTokenize(chainStr);
      for (const auto& [token, op]: tokens) {
        if (token.empty()) {
          GUM_ERROR(InvalidArc,
                    "fastGraph: malformed description '" << desc
                                                         << "' (operator without a node token)")
        }
        if (!fastGraphIsNodeIdToken(token)) { useIds = false; }
      }
      chains.push_back(std::move(tokens));
    }
 
    GRAPH_TYPE g;
 
    auto resolve = [&](const std::string& token) { return fastGraphBuildNode(g, token, useIds); };
    auto addArc  = [&](NodeId tail, NodeId head, const std::string& token) {
      if constexpr (GUM_DiGraphable< GRAPH_TYPE >) {
        g.addArc(tail, head);
      } else {
        GUM_ERROR(InvalidArc,
                  "fastGraph: '" << token << "' is preceded by an arc operator but the "
                                 << "requested graph type does not support arcs")
      }
    };
    auto addEdge = [&](NodeId a, NodeId b, const std::string& token) {
      if constexpr (GUM_UndiGraphable< GRAPH_TYPE >) {
        g.addEdge(a, b);
      } else {
        GUM_ERROR(InvalidEdge,
                  "fastGraph: '" << token << "' is preceded by '-' but the "
                                 << "requested graph type does not support edges")
      }
    };
 
    for (const auto& tokens: chains) {
      fastGraphWalkTokens(tokens, desc, resolve, addArc, addEdge);
    }
 
    return g;
  }
 
}   // namespace gum