Move pathfinders to dedicated files

cpp/src/pathfinder/dijkstra.cpp

@@ -0,0 +1,73 @@
+#include <queue>
+
+#include "dijkstra.hpp"
+
+#include "base.hpp"
+#include "utils.hpp"
+#include "math.hpp"
+#include "map.hpp"
+
+namespace pathfinder {
+
+Path Dijkstra::CalculatePath(WorldPos start_world, WorldPos end_world)
+{
+  using QueueEntry = utils::QueueEntry;
+
+  if (!m_Map) return {};
+
+  const TilePos start = m_Map->WorldToTile(start_world);
+  const TilePos end   = m_Map->WorldToTile(end_world);
+
+  if (!m_Map->IsTilePosValid(start) || !m_Map->IsTilePosValid(end))
+      return {};
+  if (start == end) return {};
+
+  // clear previous run
+  m_CameFrom.clear();
+  m_Cost.clear();
+
+  std::priority_queue<QueueEntry, std::vector<QueueEntry>, std::greater<>> frontier;
+  frontier.push({0.0f, start});
+  m_CameFrom[start] = start;   // sentinel
+  m_Cost[start]     = 0.0f;
+
+  while (!frontier.empty())
+  {
+      const QueueEntry current = frontier.top();
+      frontier.pop();
+
+      if (current.tile == end)          // early exit
+          break;
+
+      for (TilePos next : m_Map->GetNeighbors(current.tile))
+      {
+          // cost of moving to neighbour (uniform 1.0 matches original BFS)
+          const float newCost = m_Cost[current.tile] + m_Map->GetCost(next);
+
+          if (!m_Cost.count(next) || newCost < m_Cost[next])
+          {
+              m_Cost[next]     = newCost;
+              m_CameFrom[next] = current.tile;
+              frontier.push({newCost, next});
+          }
+      }
+  }
+
+  // reconstruct path
+  if (!m_CameFrom.count(end))
+      return {};                   // goal never reached
+
+  Path path;
+  TilePos cur = end;
+  path.push_back(m_Map->TileToWorld(cur));
+
+  while (cur != start)
+  {
+      cur = m_CameFrom[cur];
+      path.push_back(m_Map->TileToWorld(cur));
+  }
+  std::reverse(path.begin(), path.end());
+  return path;
+}
+
+} // pathfinder namespace