Adding endpoint to only get locations visible to character

microservices/CharacterApi/Controllers/CharactersController.cs

@@ -66,7 +66,7 @@ public class CharactersController : ControllerBase
         if (character is null)
             return NotFound();
 
-        var locations = await _characters.GetVisibleLocationsAsync(character);
+        var locations = await _characters.GetOrCreateVisibleLocationsAsync(character);
         return Ok(locations);
     }
 

microservices/CharacterApi/DOCUMENTS.md

@@ -41,3 +41,4 @@ Outbound JSON documents
     }
   ]
   ```
+  Missing locations within the character's vision window are created automatically before this response is returned.

microservices/CharacterApi/README.md

@@ -6,5 +6,5 @@ See `DOCUMENTS.md` for request payloads and stored document shapes.
 ## Endpoints
 - `POST /api/characters` Create a character.
 - `GET /api/characters` List characters for the current user.
-- `GET /api/characters/{id}/visible-locations` List locations visible to that owned character.
+- `GET /api/characters/{id}/visible-locations` Ensure and list locations visible to that owned character.
 - `DELETE /api/characters/{id}` Delete a character owned by the current user.

microservices/CharacterApi/Services/CharacterStore.cs

@@ -1,4 +1,5 @@
 using CharacterApi.Models;
+using MongoDB.Bson;
 using MongoDB.Driver;
 
 namespace CharacterApi.Services;
@@ -41,6 +42,17 @@ public class CharacterStore
     }
 
     public Task<List<VisibleLocation>> GetVisibleLocationsAsync(Character character)
+    {
+        return GetVisibleLocationsInternalAsync(character, ensureGenerated: false);
+    }
+
+    public async Task<List<VisibleLocation>> GetOrCreateVisibleLocationsAsync(Character character)
+    {
+        await EnsureVisibleLocationsExistAsync(character);
+        return await GetVisibleLocationsInternalAsync(character, ensureGenerated: true);
+    }
+
+    private Task<List<VisibleLocation>> GetVisibleLocationsInternalAsync(Character character, bool ensureGenerated)
     {
         var radius = character.VisionRadius > 0 ? character.VisionRadius : 3;
         var minX = character.Coord.X - radius;
@@ -58,6 +70,44 @@ public class CharacterStore
         return _locations.Find(filter).ToListAsync();
     }
 
+    private async Task EnsureVisibleLocationsExistAsync(Character character)
+    {
+        var radius = character.VisionRadius > 0 ? character.VisionRadius : 3;
+
+        for (var x = character.Coord.X - radius; x <= character.Coord.X + radius; x++)
+        {
+            for (var y = character.Coord.Y - radius; y <= character.Coord.Y + radius; y++)
+            {
+                var filter = Builders<VisibleLocation>.Filter.And(
+                    Builders<VisibleLocation>.Filter.Eq(l => l.Coord.X, x),
+                    Builders<VisibleLocation>.Filter.Eq(l => l.Coord.Y, y)
+                );
+
+                var update = Builders<VisibleLocation>.Update
+                    .SetOnInsert(l => l.Name, DefaultLocationName(x, y))
+                    .SetOnInsert(l => l.Coord, new Coord { X = x, Y = y })
+                    .SetOnInsert(l => l.Id, ObjectId.GenerateNewId().ToString())
+                    .SetOnInsert("createdUtc", DateTime.UtcNow);
+
+                try
+                {
+                    await _locations.UpdateOneAsync(filter, update, new UpdateOptions { IsUpsert = true });
+                }
+                catch (MongoWriteException ex) when (ex.WriteError.Category == ServerErrorCategory.DuplicateKey)
+                {
+                    // Another request or service instance created it first.
+                }
+            }
+        }
+    }
+
+    private static string DefaultLocationName(int x, int y)
+    {
+        if (x == 0 && y == 0)
+            return "Origin";
+        return $"Location {x},{y}";
+    }
+
     public async Task<bool> DeleteForOwnerAsync(string id, string ownerUserId, bool allowAnyOwner)
     {
         var filter = Builders<Character>.Filter.Eq(c => c.Id, id);