1 files changed, 117 insertions, 5 deletions

diff --git a/src/station_cmd.cpp b/src/station_cmd.cpp
index 2cc60b4ef..0fe4bebf2 100644
--- a/src/station_cmd.cpp
+++ b/src/station_cmd.cpp
@@ -1610,6 +1610,88 @@ static const byte * const _airport_sections[] = {
 	_airport_sections_helistation        // Helistation
 };
 
+/** Recalculate the noise generated by the airports of each town */
+void UpdateAirportsNoise()
+{
+	Town *t;
+	const Station *st;
+
+	FOR_ALL_TOWNS(t) t->noise_reached = 0;
+
+	FOR_ALL_STATIONS(st) {
+		if (IsAirport(st->xy)) {
+			st->town->noise_reached += GetAirportNoiseLevelForTown(GetAirport(st->airport_type), st->town->xy, st->xy);
+		}
+	}
+}
+
+/** Get a possible noise reduction factor based on distance from town center.
+ * The further you get, the less noise you generate.
+ * So all those folks at city council can now happily slee...  work in their offices
+ * @param afc AirportFTAClass pointer of the class being proposed
+ * @param town_tile TileIndex of town's center, the one who will receive the airport's candidature
+ * @param tile TileIndex where the new airport might be built
+ * @return the noise that will be generated, according to distance
+ */
+uint8 GetAirportNoiseLevelForTown(const AirportFTAClass *afc, TileIndex town_tile, TileIndex tile)
+{
+	struct TileIndexDistance {
+		TileIndex index;
+		uint distance;
+	};
+
+	uint distance;
+
+	/* 0 cannot be accounted, and 1 is the lowest that can be reduced from town.
+	 * So no need to go any further*/
+	if (afc->noise_level < 2) return afc->noise_level;
+
+	/* Find the airport-to-be's closest corner to the town */
+	if (afc->size_x == 1 && afc->size_y == 1) {
+		distance = DistanceManhattan(town_tile, tile);  // ont tile, one corner, it's THE corner
+	} else {
+		/* calculate manhattan distance to town of each side of the airport */
+		TileIndexDistance dist[4]; ///< Array that will contain all 4 corners in TileIndex and distance
+		uint min_tile = UINT_MAX;  ///< Sentinel value
+		uint min_indice = 4;
+
+		/* Based on the size of the airport, establish location of each corner*/
+		dist[0].index = tile; // north tile
+		dist[1].index = TileAddWrap(tile, afc->size_x - 1, afc->size_y - 1);  // south tile
+		dist[2].index = TileAddWrap(tile, afc->size_x - 1, 0);  // west tile
+		dist[3].index = TileAddWrap(tile, 0, afc->size_y - 1); //east tile
+
+		/* now, go and find the smallest one, thus the closest to town */
+		for (uint i = 0; i < 4; i++) {
+			dist[i].distance = DistanceManhattan(town_tile, dist[i].index);
+
+			if (dist[i].distance < min_tile) {
+				min_tile = dist[i].distance;  // here's a new candidate
+				min_indice = i;
+			}
+		}
+
+		distance = dist[min_indice].distance;
+	}
+
+	/* The steps for measuring noise reduction are based on the "magical" (and arbitrary) 8 base distance
+	 * adding the town_council_tolerance 4 times, as a way to graduate, depending of the tolerance.
+	 * Basically, it says that the less tolerant a town is, the bigger the distance before
+	 * an actual decrease can be granted */
+	uint8 town_tolerance_distance = 8 + (_opt.diff.town_council_tolerance * 4);
+
+	/* The airport is in the "inner" distance where there is no noise reduction */
+	if (distance < town_tolerance_distance) return afc->noise_level;
+
+	/* now, we want to have the distance segmented using the distance judged bareable by town
+	 * This will give us the coefficient of reduction the distance provides. */
+	uint noise_reduction = min(afc->noise_level, distance / town_tolerance_distance);
+
+	/* If the noise reduction equals the airport noise itself, don't give it for free. Use it all minus 1.
+	 * Otherwise, simply reduce the airport's level. */
+	return max(1U, noise_reduction == afc->noise_level ? afc->noise_level - 1 : afc->noise_level - noise_reduction);
+}
+
 /** Place an Airport.
  * @param tile tile where airport will be built
  * @param flags operation to perform
@@ -1641,12 +1723,25 @@ CommandCost CmdBuildAirport(TileIndex tile, uint32 flags, uint32 p1, uint32 p2)
 	CommandCost cost = CheckFlatLandBelow(tile, w, h, flags, 0, NULL);
 	if (CmdFailed(cost)) return cost;
 
-	/* Check if local auth refuses a new airport */
-	uint num = 0;
-	FOR_ALL_STATIONS(st) {
-		if (st->town == t && st->facilities & FACIL_AIRPORT && st->airport_type != AT_OILRIG) num++;
+	/* Go get the final noise level, that is base noise minus factor from distance to town center */
+	uint newnoise_level = GetAirportNoiseLevelForTown(afc, t->xy, tile);
+
+	/* Check if local auth would allow a new airport */
+	bool autority_refused;
+
+	if (_patches.station_noise_level) {
+		/* do not allow to build a new airport if this raise the town noise over the maximum allowed by town */
+		autority_refused = (t->noise_reached + newnoise_level) > t->MaxTownNoise();
+	} else {
+		uint num = 0;
+		const Station *st;
+		FOR_ALL_STATIONS(st) {
+			if (st->town == t && st->facilities & FACIL_AIRPORT && st->airport_type != AT_OILRIG) num++;
+		}
+		autority_refused = (num >= 2);
 	}
-	if (num >= 2) {
+
+	if (autority_refused) {
 		SetDParam(0, t->index);
 		return_cmd_error(STR_2035_LOCAL_AUTHORITY_REFUSES);
 	}
@@ -1693,6 +1788,9 @@ CommandCost CmdBuildAirport(TileIndex tile, uint32 flags, uint32 p1, uint32 p2)
 	cost.AddCost(_price.build_airport * w * h);
 
 	if (flags & DC_EXEC) {
+		/* Always add the noise, so there will be no need to recalculate when option toggles */
+		st->town->noise_reached += newnoise_level;
+
 		st->airport_tile = tile;
 		st->AddFacility(FACIL_AIRPORT, tile);
 		st->airport_type = (byte)p1;
@@ -1722,6 +1820,10 @@ CommandCost CmdBuildAirport(TileIndex tile, uint32 flags, uint32 p1, uint32 p2)
 		UpdateStationAcceptance(st, false);
 		InvalidateWindowData(WC_STATION_LIST, st->owner, 0);
 		InvalidateWindowWidget(WC_STATION_VIEW, st->index, SVW_PLANES);
+
+		if (_patches.station_noise_level) {
+			InvalidateWindow(WC_TOWN_VIEW, st->town->index);
+		}
 	}
 
 	return cost;
@@ -1764,12 +1866,22 @@ static CommandCost RemoveAirport(Station *st, uint32 flags)
 			);
 		}
 
+		/* Go get the final noise level, that is base noise minus factor from distance to town center.
+		 * And as for construction, always remove it, even if the patch is not set, in order to avoid the
+		 * need of recalculation */
+		st->town->noise_reached -= GetAirportNoiseLevelForTown(afc, st->town->xy, tile);
+
 		st->rect.AfterRemoveRect(st, tile, w, h);
 
 		st->airport_tile = 0;
 		st->facilities &= ~FACIL_AIRPORT;
 
 		InvalidateWindowWidget(WC_STATION_VIEW, st->index, SVW_PLANES);
+
+		if (_patches.station_noise_level) {
+			InvalidateWindow(WC_TOWN_VIEW, st->town->index);
+		}
+
 		UpdateStationVirtCoordDirty(st);
 		DeleteStationIfEmpty(st);
 	}