/* $Id$ */
/** @file elrail.c
  This file deals with displaying wires and pylons for electric railways.
<h2>Basics</h2>

<h3>Tile Types</h3>

We have two different types of tiles in the drawing code:
Normal Railway Tiles (NRTs) which can have more than one track on it, and
Special Railways tiles (SRTs) which have only one track (like crossings, depots
stations, etc).

<h3>Location Categories</h3>

All tiles are categorized into three location groups (TLG):
Group 0: Tiles with both an even X coordinate and an even Y coordinate
Group 1: Tiles with an even X and an odd Y coordinate
Group 2: Tiles with an odd X and an even Y coordinate
Group 3: Tiles with both an odd X and Y coordnate.

<h3>Pylon Points</h3>
<h4>Control Points</h4>
A Pylon Control Point (PCP) is a position where a wire (or rather two)
is mounted onto a pylon.
Each NRT does contain 4 PCPs which are bitmapped to a byte
variable and are represented by the DiagDirection enum

Each track ends on two PCPs and thus requires one pylon on each end. However,
there is one exception: Straight-and-level tracks only have one pylon every
other tile.

Now on each edge there are two PCPs: One from each adjacent tile. Both PCPs
are merged using an OR operation (i. e. if one tile needs a PCP at the postion
in question, both tiles get it).

<h4>Position Points</h4>
A Pylon Position Point (PPP) is a position where a pylon is located on the
ground.  Each PCP owns 8 in (45 degree steps) PPPs that are located around
it. PPPs are represented using the Direction enum. Each track bit has PPPs
that are impossible (because the pylon would be situated on the track) and
some that are preferred (because the pylon would be rectangular to the track).

<img src="../../elrail_tile.png">
<img src="../../elrail_track.png">

  */

#include "stdafx.h"
#include "openttd.h"
#include "station_map.h"
#include "tile.h"
#include "viewport.h"
#include "functions.h" /* We should REALLY get rid of this goddamn file, as it is butt-ugly */
#include "variables.h" /* ... same here */
#include "rail.h"
#include "debug.h"
#include "tunnel_map.h"
#include "road_map.h"
#include "bridge_map.h"
#include "bridge.h"
#include "rail_map.h"
#include "table/sprites.h"
#include "table/elrail_data.h"

static inline TLG GetTLG(TileIndex t)
{
	return (HASBIT(TileX(t), 0) << 1) + HASBIT(TileY(t), 0);
}

/** Finds which Rail Bits are present on a given tile. For bridge tiles,
  * returns track bits under the bridge
  */
static TrackBits GetRailTrackBitsUniversal(TileIndex t, byte *override)
{
	switch (GetTileType(t)) {
		case MP_RAILWAY:
			if (GetRailType(t) != RAILTYPE_ELECTRIC) return 0;
			switch (GetRailTileType(t)) {
				case RAIL_TILE_NORMAL: case RAIL_TILE_SIGNALS:
					return GetTrackBits(t);
				case RAIL_TILE_DEPOT_WAYPOINT:
					if (GetRailTileSubtype(t) == RAIL_SUBTYPE_WAYPOINT) return GetRailWaypointBits(t);
				default:
					return 0;
			}
			break;

		case MP_TUNNELBRIDGE:
			if (IsTunnel(t)) {
				if (GetRailType(t) != RAILTYPE_ELECTRIC) return 0;
				if (override != NULL) *override = 1 << GetTunnelDirection(t);
				return AxisToTrackBits(DiagDirToAxis(GetTunnelDirection(t)));
			} else {
				if (GetRailType(t) != RAILTYPE_ELECTRIC) return 0;
				if (IsBridgeMiddle(t)) {
					if (IsTransportUnderBridge(t) &&
						GetTransportTypeUnderBridge(t) == TRANSPORT_RAIL) {
						return GetRailBitsUnderBridge(t);
					} else {
						return 0;
					}
				} else {
					if (override != NULL && DistanceMax(t, GetOtherBridgeEnd(t)) > 1) *override = 1 << GetBridgeRampDirection(t);

					return AxisToTrackBits(DiagDirToAxis(GetBridgeRampDirection(t)));
				}
			}

		case MP_STREET:
			if (GetRoadTileType(t) != ROAD_TILE_CROSSING) return 0;
			if (GetRailTypeCrossing(t) != RAILTYPE_ELECTRIC) return 0;
			return GetCrossingRailBits(t);

		case MP_STATION:
			if (!IsRailwayStation(t)) return 0;
			if (GetRailType(t) != RAILTYPE_ELECTRIC) return 0;
			if (!IsStationTileElectrifiable(t)) return 0;
			return TrackToTrackBits(GetRailStationTrack(t));

		default:
			return 0;
	}
}

/** Corrects the tileh for certain tile types. Returns an effective tileh for the track on the tile.
  * @param tile The tile to analyse
  * @param *tileh the tileh
  */
static void AdjustTileh(TileIndex tile, Slope *tileh)
{
	if (IsTileType(tile, MP_TUNNELBRIDGE)) {
		if (IsTunnel(tile)) {
			*tileh = SLOPE_FLAT;
		} else {
			if (IsBridgeRamp(tile)) {
				if (*tileh != SLOPE_FLAT) {
					*tileh = SLOPE_FLAT;
				} else {
					switch (GetBridgeRampDirection(tile)) {
						case DIAGDIR_NE: *tileh = SLOPE_NE; break;
						case DIAGDIR_SE: *tileh = SLOPE_SE; break;
						case DIAGDIR_SW: *tileh = SLOPE_SW; break;
						case DIAGDIR_NW: *tileh = SLOPE_NW; break;
						default: break;
					}
				}
			}
		}
	}
}

/** Draws wires and, if required, pylons on a given tile
  * @param ti The Tileinfo to draw the tile for
  */
static void DrawCatenaryRailway(const TileInfo *ti)
{
	/* Pylons are placed on a tile edge, so we need to take into account
	   the track configuration of 2 adjacent tiles. trackconfig[0] stores the
	   current tile (home tile) while [1] holds the neighbour */
	TrackBits trackconfig[TS_END];
	bool isflat[TS_END];
	/* Note that ti->tileh has already been adjusted for Foundations */
	Slope tileh[TS_END] = { ti->tileh, SLOPE_FLAT };

	TLG tlg = GetTLG(ti->tile);
	byte PCPstatus = 0;
	byte OverridePCP = 0;
	byte PPPpreferred[DIAGDIR_END];
	byte PPPallowed[DIAGDIR_END];
	DiagDirection i;
	Track t;

	/* Find which rail bits are present, and select the override points.
	   We don't draw a pylon:
	   1) INSIDE a tunnel (we wouldn't see it anyway)
	   2) on the "far" end of a bridge head (the one that connects to bridge middle),
	      because that one is drawn on the bridge. Exception is for length 0 bridges
	      which have no middle tiles */
	trackconfig[TS_HOME] = GetRailTrackBitsUniversal(ti->tile, &OverridePCP);
	/* If a track bit is present that is not in the main direction, the track is level */
	isflat[TS_HOME] = trackconfig[TS_HOME] & (TRACK_BIT_HORZ | TRACK_BIT_VERT);

	AdjustTileh(ti->tile, &tileh[TS_HOME]);

	for (i = DIAGDIR_NE; i < DIAGDIR_END; i++) {
		TileIndex neighbour = ti->tile + TileOffsByDir(i);
		uint foundation = 0;
		int k;

		/* Here's one of the main headaches. GetTileSlope does not correct for possibly
		   existing foundataions, so we do have to do that manually later on.*/
		tileh[TS_NEIGHBOUR] = GetTileSlope(neighbour, NULL);
		trackconfig[TS_NEIGHBOUR] = GetRailTrackBitsUniversal(neighbour, NULL);
		if (IsTunnelTile(neighbour) && i != GetTunnelDirection(neighbour)) trackconfig[TS_NEIGHBOUR] = 0;
		isflat[TS_NEIGHBOUR] = trackconfig[TS_NEIGHBOUR] & (TRACK_BIT_HORZ | TRACK_BIT_VERT);

		PPPpreferred[i] = 0xFF; /* We start with preferring everything (end-of-line in any direction) */
		PPPallowed[i] = AllowedPPPonPCP[i];

		/* We cycle through all the existing tracks at a PCP and see what
		   PPPs we want to have, or may not have at all */
		for (k = 0; k < NUM_TRACKS_AT_PCP; k++) {
			/* Next to us, we have a bridge head, don't worry about that one, if it shows away from us */
			if (TrackSourceTile[i][k] == TS_NEIGHBOUR &&
			    IsBridgeTile(neighbour) && IsBridgeRamp(neighbour) &&
			    GetBridgeRampDirection(neighbour) == ReverseDiagDir(i)) {
				continue;
			}

			/* We check whether the track in question (k) is present in the tile
			   (TrackSourceTile) */
			if (HASBIT(trackconfig[TrackSourceTile[i][k]], TracksAtPCP[i][k])) {
				/* track found, if track is in the neighbour tile, adjust the number
				   of the PCP for preferred/allowed determination*/
				DiagDirection PCPpos = (TrackSourceTile[i][k] == TS_HOME) ? i : ReverseDiagDir(i);
				SETBIT(PCPstatus, i); /* This PCP is in use */

				PPPpreferred[i] &= PreferredPPPofTrackAtPCP[TracksAtPCP[i][k]][PCPpos];
				PPPallowed[i] &= ~DisallowedPPPofTrackAtPCP[TracksAtPCP[i][k]][PCPpos];
			}
		}

		/* Deactivate all PPPs if PCP is not used */
		PPPpreferred[i] *= HASBIT(PCPstatus, i);
		PPPallowed[i] *= HASBIT(PCPstatus, i);

		/* A station is always "flat", so adjust the tileh accordingly */
		if (IsTileType(neighbour, MP_STATION)) tileh[TS_NEIGHBOUR] = SLOPE_FLAT;

		/* Read the foundataions if they are present, and adjust the tileh */
		if (IsTileType(neighbour, MP_RAILWAY)) foundation = GetRailFoundation(tileh[TS_NEIGHBOUR], trackconfig[TS_NEIGHBOUR]);
		if (IsBridgeTile(neighbour) && IsBridgeRamp(neighbour)) {
			foundation = GetBridgeFoundation(tileh[TS_NEIGHBOUR], DiagDirToAxis(GetBridgeRampDirection(neighbour)));
		}

		if (foundation != 0) {
			if (foundation < 15) {
				tileh[TS_NEIGHBOUR] = SLOPE_FLAT;
			} else {
				tileh[TS_NEIGHBOUR] = _inclined_tileh[foundation - 15];
			}
		}

		AdjustTileh(neighbour, &tileh[TS_NEIGHBOUR]);

		/* If we have a straight (and level) track, we want a pylon only every 2 tiles
		   Delete the PCP if this is the case. */
		/* Level means that the slope is the same, or the track is flat */
		if (tileh[TS_HOME] == tileh[TS_NEIGHBOUR] || (isflat[TS_HOME] && isflat[TS_NEIGHBOUR])) {
			for (k = 0; k < NUM_IGNORE_GROUPS; k++)
				if (PPPpreferred[i] == IgnoredPCP[k][tlg][i]) CLRBIT(PCPstatus, i);
		}

		/* Now decide where we draw our pylons. First try the preferred PPPs, but they may not exist.
		   In that case, we try the any of the allowed ones. if they don't exist either, don't draw
		   anything. Note that the preferred PPPs still contain the end-of-line markers.
		   Remove those (simply by ANDing with allowed, since these markers are never allowed) */
		if ((PPPallowed[i] & PPPpreferred[i]) != 0) PPPallowed[i] &= PPPpreferred[i];

		if (PPPallowed[i] != 0 && HASBIT(PCPstatus, i) && !HASBIT(OverridePCP, i)) {
			for (k = 0; k < DIR_END; k++) {
				byte temp = PPPorder[i][GetTLG(ti->tile)][k];

				if (HASBIT(PPPallowed[i], temp)) {
					uint x  = ti->x + x_pcp_offsets[i] + x_ppp_offsets[temp];
					uint y  = ti->y + y_pcp_offsets[i] + y_ppp_offsets[temp];

					/* Don't build the pylon if it would be outside the tile */
					if (!HASBIT(OwnedPPPonPCP[i], temp)) {
						/* We have a neighour that will draw it, bail out */
						if (trackconfig[TS_NEIGHBOUR] != 0) break;
						continue; /* No neighbour, go looking for a better position */
					}

					AddSortableSpriteToDraw(pylons_normal[temp], x, y, 1, 1, 10,
							GetSlopeZ(ti->x + x_pcp_offsets[i], ti->y + y_pcp_offsets[i]));
					break; /* We already have drawn a pylon, bail out */
				}
			}
		}
	}

	/* Drawing of pylons is finished, now draw the wires */
	for (t = 0; t < TRACK_END; t++) {
		if (HASBIT(trackconfig[TS_HOME], t)) {

			byte PCPconfig = HASBIT(PCPstatus, PCPpositions[t][0]) +
				(HASBIT(PCPstatus, PCPpositions[t][1]) << 1);

			const SortableSpriteStruct *sss;
			int tileh_selector = !(tileh[TS_HOME] % 3) * tileh[TS_HOME] / 3; /* tileh for the slopes, 0 otherwise */

			if ( /* We are not drawing a wire under a low bridge */
					IsBridgeTile(ti->tile) &&
					IsBridgeMiddle(ti->tile) &&
					!(_display_opt & DO_TRANS_BUILDINGS) &&
					GetBridgeHeight(ti->tile) <= TilePixelHeight(ti->tile) + TILE_HEIGHT
			   ) return;

			assert(PCPconfig != 0); /* We have a pylon on neither end of the wire, that doesn't work (since we have no sprites for that) */
			assert(!IsSteepSlope(tileh[TS_HOME]));
			sss = &CatenarySpriteData[Wires[tileh_selector][t][PCPconfig]];

			AddSortableSpriteToDraw( sss->image, ti->x + sss->x_offset, ti->y + sss->y_offset,
				sss->x_size, sss->y_size, sss->z_size, GetSlopeZ(ti->x + min(sss->x_offset, TILE_SIZE - 1), ti->y + min(sss->y_offset, TILE_SIZE - 1)) + sss->z_offset);
		}
	}
}

static void DrawCatenaryOnBridge(const TileInfo *ti)
{
	TileIndex end = GetSouthernBridgeEnd(ti->tile);
	TileIndex start = GetOtherBridgeEnd(end);

	uint length = GetBridgeLength(start, end);
	uint num = DistanceMax(ti->tile, start);
	uint height;

	const SortableSpriteStruct *sss;
	Axis axis = GetBridgeAxis(ti->tile);
	TLG tlg = GetTLG(ti->tile);

	CatenarySprite offset = axis == AXIS_X ? 0 : WIRE_Y_FLAT_BOTH - WIRE_X_FLAT_BOTH;

	if ((length % 2) && num == length) {
		/* Draw the "short" wire on the southern end of the bridge
		 * only needed if the length of the bridge is odd */
		sss = &CatenarySpriteData[WIRE_X_FLAT_BOTH + offset];
	} else {
		/* Draw "long" wires on all other tiles of the bridge (one pylon every two tiles) */
		sss = &CatenarySpriteData[WIRE_X_FLAT_SW + (num % 2) + offset];
	}

	height = GetBridgeHeight(ti->tile);

	AddSortableSpriteToDraw( sss->image, ti->x + sss->x_offset, ti->y + sss->y_offset,
		sss->x_size, sss->y_size, sss->z_size, height + sss->z_offset
	);

	/* Finished with wires, draw pylons */
	/* every other tile needs a pylon on the northern end */
	if (num % 2) {
		if (axis == AXIS_X) {
			AddSortableSpriteToDraw(pylons_bridge[0 + HASBIT(tlg, 0)], ti->x, ti->y + 4 + 8 * HASBIT(tlg, 0), 1, 1, 10, height);
		} else {
			AddSortableSpriteToDraw(pylons_bridge[2 + HASBIT(tlg, 1)], ti->x + 4 + 8 * HASBIT(tlg, 1), ti->y, 1, 1, 10, height);
		}
	}

	/* need a pylon on the southern end of the bridge */
	if (DistanceMax(ti->tile, start) == length) {
		if (axis == AXIS_X) {
			AddSortableSpriteToDraw(pylons_bridge[0 + HASBIT(tlg, 0)], ti->x + 16, ti->y + 4 + 8 * HASBIT(tlg, 0), 1, 1, 10, height);
		} else {
			AddSortableSpriteToDraw(pylons_bridge[2 + HASBIT(tlg, 1)], ti->x + 4 + 8 * HASBIT(tlg, 1), ti->y + 16, 1, 1, 10, height);
		}
	}
}

void DrawCatenary(const TileInfo *ti)
{
	switch (GetTileType(ti->tile)) {
		case MP_RAILWAY:
			if (IsRailDepot(ti->tile)) {
				const SortableSpriteStruct *sss = &CatenarySpriteData[WIRE_DEPOT_SW + ReverseDiagDir(GetRailDepotDirection(ti->tile))];
				AddSortableSpriteToDraw( sss->image, ti->x + sss->x_offset, ti->y + sss->y_offset,
					sss->x_size, sss->y_size, sss->z_size, GetSlopeZ(ti->x, ti->y) + sss->z_offset);
				return;
			}
			break;

		case MP_TUNNELBRIDGE:
			if (IsBridge(ti->tile) && IsBridgeMiddle(ti->tile) && GetRailTypeOnBridge(ti->tile) == RAILTYPE_ELECTRIC) DrawCatenaryOnBridge(ti);
			break;

		case MP_STREET:  break;
		case MP_STATION: break;

		default: return;
	}
	DrawCatenaryRailway(ti);
}