1 files changed, 292 insertions, 0 deletions
diff --git a/lexer.cpp b/lexer.cpp
new file mode 100644
index 0000000..46a38bd
--- /dev/null
+++ b/lexer.cpp
@@ -0,0 +1,292 @@
+#include "lexer.h"
+
+void Tree::clear() {
+ nodes.clear();
+ root = 0;
+ last = 0;
+ node_num = 0;
+}
+
+// Type of lexical token
+std::string Tree::GetType() {
+ if (node_num > 0 && nodes[root].child_names.size() == 1)
+  return nodes[root].child_names[0];
+ return "";
+}
+
+bool Tree::Valid(const std::string& Top) const {
+ // A token is non empty
+ if (node_num == 0)
+  return false;
+
+ // Start symbol on top
+ auto rootNode{nodes.find(root)};
+ if (rootNode == nodes.end())
+  throw std::runtime_error("Node not found: "s + std::to_string(root));
+ 
+ if (rootNode->second.name != Top)
+  return false;
+
+ // All nodes filled (implies all leaves are terminal)
+ for (const auto& [index, node]: nodes) {
+  if (node.childs.size() < node.child_names.size())
+   return false; // node not filled
+ }
+
+ return true;
+}
+
+bool Tree::AddFirstNode(char c, const BNF& bnf, const std::map<std::string, std::set<std::string>>& reverseBNF) {
+ node_num ++;
+ root = node_num;
+ last = node_num;
+ std::string node_name(1, char(c));
+
+ auto reverseRule{reverseBNF.find(node_name)};
+ if (reverseRule == reverseBNF.end())
+  throw std::runtime_error("Reverse rule not found for "s + node_name);
+
+ auto rule{bnf.find(node_name)};
+ if (rule != bnf.end()) { // multiple variants!
+  throw std::runtime_error("BNF rule for terminal symbol "s + node_name + " found."s);
+ }
+ nodes.emplace(root, TreeNode{0, std::vector<index_t>{}, std::vector<std::string>{}, node_name});
+ return true;
+}
+
+std::vector<TreeNode> Tree::getParentTreeNode(const BNF& bnf, const std::map<std::string, std::set<std::string>>& reverseBNF) {
+ std::vector<TreeNode> result; // default: empty
+
+ auto& root_name {nodes[root].name};
+ auto bnfParents {reverseBNF.find(root_name)};
+ if (bnfParents == reverseBNF.end())
+  return result;
+
+ for (const auto& parent_node_name : bnfParents->second) {
+  auto lists {bnf.at(parent_node_name)};
+  for (const auto& list : lists) {
+   if (list.size() > 0 && list[0] == root_name) {
+    TreeNode node{0, std::vector<index_t>{root}, list, parent_node_name};
+    result.push_back(node);
+   }
+  }
+ }
+
+ return result;
+}
+
+index_t Tree::GetLast() {
+ index_t result {root};
+
+ while(result != 0 && nodes[result].childs.size() >= 2) {
+  result = nodes[result].childs[nodes[result].childs.size() - 1];
+ }
+
+ return result;
+}
+
+void Tree::AddRootNode(const TreeNode& newRootNode) {
+ node_num++;
+ nodes[node_num] = newRootNode;
+ root = node_num;
+ last = node_num;
+}
+
+void Tree::RemoveRootNode() {
+ root = nodes[root].childs[0];
+ nodes.erase(node_num);
+ node_num--;
+ last = GetLast();
+}
+
+// Path from leaf to root
+std::vector<std::string> Tree::GetPath(std::string a, std::string b, const BNF& bnf, const std::map<std::string, std::set<std::string>>& reverseBNF) {
+ std::vector<std::string> result;
+
+ while (a != b) {
+  auto parents {reverseBNF.find(a)};
+  if (parents == reverseBNF.end())
+   return {};
+
+  bool hit{false};
+  for (const auto& parent : parents->second) {
+   for (const auto& list : bnf.at(parent)) {
+    if (list.size() > 0 && list[0] == a) {
+     if (!hit) {
+      result.push_back(a);
+      a = parent;
+      hit = true;
+     } else
+      throw std::runtime_error("Double match for "s + parent + "/"s + a);
+    }
+   }
+  }
+ }
+ if (a == b) {
+  result.push_back(a);
+ }
+ return result;
+}
+
+index_t Tree::AddNode(const std::string& name, const std::string& child_name, index_t parent_index, const BNF& bnf, const std::map<std::string, std::set<std::string>>& reverseBNF)
+{
+ TreeNode& parent {nodes[parent_index]};
+ node_num++;
+ index_t index = node_num;
+ parent.childs.push_back(index);
+ std::vector<std::string> child_names;
+ auto rule {bnf.find(name)};
+ if (rule != bnf.end()) {
+  for (auto& list : rule->second) {
+   if (list.size() > 0 && list[0] == child_name)
+    child_names = list;
+  }
+ }
+ nodes.emplace(index, TreeNode{parent_index, {}, child_names, name});
+ //root stays
+ last = GetLast();
+
+ return index;
+}
+
+void Tree::AddPath(const std::vector<std::string>& path, index_t current_index, const BNF& bnf, const std::map<std::string, std::set<std::string>>& reverseBNF) {
+ for (int i = path.size() - 1; i >= 0; i--) {
+  std::string child_name;
+  if (i > 0)
+   child_name = path[i - 1];
+  current_index = AddNode(path[i], child_name, current_index, bnf, reverseBNF);
+ }
+}
+
+// try to add character to tree
+bool Tree::Add(char c, const BNF& bnf, const std::map<std::string, std::set<std::string>>& reverseBNF) {
+ if (nodes.empty()) { // first node
+  return AddFirstNode(c, bnf, reverseBNF);
+ } else { // at least one character is already present
+  // Traverse tree until partially filled node found
+  // or new node can be added
+  index_t current_index{last};
+
+  while (current_index != 0) {
+   TreeNode& node {nodes[current_index]};
+   if (node.childs.size() < node.child_names.size()) { // partially filled node
+    std::vector<std::string> list = GetPath(std::string(1, c), node.child_names[node.childs.size()], bnf, reverseBNF);
+    if (list.size() > 0) {
+     AddPath(list, current_index, bnf, reverseBNF);
+     return true;
+    } else {
+     return false; // The path a->b is not available via bnf
+    }
+   }
+   current_index = node.parent;
+  }
+
+  // Add node at root
+
+  std::vector<TreeNode> parent_nodes = getParentTreeNode(bnf, reverseBNF);
+  if (parent_nodes.size() == 0)
+   throw std::runtime_error("Couldn't add new parent node.");
+
+  for (const auto &i : parent_nodes) {
+   AddRootNode(i);
+   if (Add(c, bnf, reverseBNF))
+    return true;
+   RemoveRootNode();
+  }
+
+ }
+ return false;
+}
+
+// add path to start symbol
+void Tree::Resolve(const BNF& bnf, const std::map<std::string, std::set<std::string>>& reverseBNF) {
+ if (nodes.empty()) // only handle non-empty trees
+  return;
+
+ while (true) {
+  std::string& old_root_name { nodes[root].name }; // current root node name
+
+  auto parents {reverseBNF.find(old_root_name)};
+  if (parents != reverseBNF.end()) { // parents in bnf available
+   bool hit{false};
+   for (auto& parent : parents->second) {
+    for (const auto& list : bnf.at(parent)) {
+     if (list.size() == 1 && list[0] == old_root_name) {
+      if (!hit) {
+       const std::string& new_root_name {parent};
+       // Add new TreeNode in the direction to root:
+       // New root with 1 child (old root)
+       nodes.emplace(++node_num,
+                    TreeNode{0, // parent
+                             std::vector<index_t>{root}, // child indices
+                             std::vector<std::string>{old_root_name}, // child names
+                             new_root_name // name
+                    });
+       nodes[root].parent = node_num;
+       root = node_num;
+       // this->last stays
+       hit = true;
+      } else
+       throw std::runtime_error("Error: Multiple resolve nodes for "s + old_root_name);
+     }
+    }
+   }
+   if (!hit)
+    break;
+  } else
+   break;
+ }
+}
+
+void Lexer::FinalizeTree(Tree& tree, std::string& token, std::vector<Token>& result)
+{
+ tree.Resolve(bnf, ReverseBNF);
+ if (tree.Valid(Top)) {
+  result.emplace_back(Token{tree.GetType(), token, Location{location.line, location.column - token.size()}});
+  token.clear();
+ }
+ tree.clear();
+}
+
+Lexer::Lexer(const BNF& bnf, const std::string& Top): bnf(bnf), Top(Top), ReverseBNF{Reverse(bnf)}
+{
+}
+
+std::vector<Token> Lexer::Lex(const std::string& s)
+{
+ std::vector<Token> result;
+ std::string token;
+
+ std::string Whitespace{"\t \n\r"};
+ Tree tree;
+
+ for (size_t pos{0}; pos < s.size(); pos++) {
+  char c{s[pos]};
+  if (c == '\n') {
+   location.column = 0;
+   location.line++;
+  } else if (std::isprint(c)) {
+   location.column++;
+  }
+
+  //std::cout << "Char: |" << c << "|" << std::endl;
+  if (Whitespace.find(c) != std::string::npos) { // found whitespace character
+   // evaluate token up to now and skip whitespace
+   FinalizeTree(tree, token, result);
+  } else { // no whitespace: try to add to tree
+   if (!tree.Add(c, bnf, ReverseBNF)) {
+    FinalizeTree(tree, token, result);
+    if (!tree.Add(c, bnf, ReverseBNF))
+     throw std::runtime_error("Parse error");
+   }
+
+   token.push_back(c);
+  }
+ }
+
+ // Final evaluation of last token
+ FinalizeTree(tree, token, result);
+
+ return result;
+}
+