1 files changed, 90 insertions, 0 deletions
diff --git a/advtrains_trackmap/grid.lua b/advtrains_trackmap/grid.lua
new file mode 100644
index 0000000..9f367cb
--- /dev/null
+++ b/advtrains_trackmap/grid.lua
@@ -0,0 +1,90 @@
+-- grid.lua
+-- routines taking the tracks and building a grid out of them
+
+local tm = advtrains.trackmap
+
+-- Maximum scan length for track iterator
+local TS_MAX_SCAN = 1000
+
+-- Get a character matching the class requested by chr, in the correct orientation for conndir
+-- The characters will be chosen from the unicode frame set if appropriate
+-- valid character classes -, =, |
+local char_equiv = {
+	["-"] = {"│", "/", "─", "\\"}, -- single-line
+	["="] = {"║", "/", "═", "\\"}, -- double-line
+	["|"] = {"─", "\\", "│", "/"}, -- break (i.e. TCB, perpendicular to orientation)
+}
+local dir_to_charmap = {
+	[15] = 1,
+	[ 0] = 1,
+	[ 1] = 1,
+	[ 2] = 2,
+	[ 3] = 3,
+	[ 4] = 3,
+	[ 5] = 3,
+	[ 6] = 4,
+	[ 7] = 1,
+	[ 8] = 1,
+	[ 9] = 1,
+	[10] = 2,
+	[11] = 3,
+	[12] = 3,
+	[13] = 3,
+	[14] = 4,
+}
+function tm.rotate_char_class_by_conn(chr, conndir)
+	return char_equiv[chr][dir_to_charmap[conndir]]
+end
+
+-- Generate a grid map by walking tracks starting from the given position start_pos
+-- For every track that is visited, node_callback is called.
+-- signature: node_callback(pos, conns, connid)
+-- should return a table as follows:
+-- {
+--   char = "X" -- the character to use in this place, defaults to guessing a fitting frame character
+--   stop = false -- if true, the iterator will stop following this branch
+-- }
+-- Returning nil will assume defaults.
+-- return value: a table:
+-- {
+--   grid = <grid> - access abs_grid[x][y] - contains one character per cell
+--   min_pos = <pos> - the minimum pos contained in this grid
+--   max_pos = <pos> - the maximum pos
+-- }
+function tm.generate_grid_map(start_pos, node_callback)
+	local ti = advtrains.get_track_iterator(start_pos, nil, TS_MAX_SCAN, true)
+	local grid = {} -- grid[x][y]
+	local gminx, gmaxx, gminz, gmaxz = start_pos.x, start_pos.x, start_pos.z, start_pos.z
+	
+	while ti:has_next_branch() do
+		pos, connid = ti:next_branch()
+		repeat
+			local ok, conns = advtrains.get_rail_info_at(pos)
+			local c = node_callback(pos, conns, connid)
+			local chr = c and c.char
+			if not chr then
+				chr = tm.rotate_char_class_by_conn("=", conns[connid])
+			end
+			
+			-- add the char to the grid
+			if not grid[pos.x] then
+				grid[pos.x] = {}
+			end
+			grid[pos.x][pos.z] = chr
+			
+			gminx = math.min(gminx, pos.x)
+			gmaxx = math.max(gmaxx, pos.x)
+			gminz = math.min(gminz, pos.z)
+			gmaxz = math.max(gmaxz, pos.z)
+			
+			if c and c.stop then break end
+			pos, connid = ti:next_track()
+		until not pos
+	end
+	return {
+		grid = grid,
+		min_pos = {x=gminx, z=gminz},
+		max_pos = {x=gmaxx, z=gmaxz},
+	}
+end
+