Implement raster source feature to read data from third-party sources, to be used in lua profiles.

* Adds a data structure, RasterSource, to store parsed + queryable data
* Adds bindings for that and relevant data structures as well as source_function and segment_function
* Adds relevant unit tests and cucumber tests
* Bring-your-own-data feature

profiles/rasterbot-interp.lua

@@ -0,0 +1,46 @@
+-- Rasterbot profile
+
+-- Minimalist node_ and way_functions in order to test source_ and segment_functions
+
+function node_function (node, result)
+end
+
+function way_function (way, result)
+  local highway = way:get_value_by_key("highway")
+  local name = way:get_value_by_key("name")
+
+  if name then
+    result.name = name
+  end
+
+  result.forward_speed = 15
+  result.backward_speed = 15
+end
+
+function source_function ()
+  raster_source = sources:load(
+    "../test/rastersource.asc",
+    0,    -- lon_min
+    0.1,  -- lon_max
+    0,    -- lat_min
+    0.1,  -- lat_max
+    5,    -- nrows
+    4     -- ncols
+  )
+end
+
+function segment_function (source, target, distance, weight)
+  local sourceData = sources:interpolate(raster_source, source.lon, source.lat)
+  local targetData = sources:interpolate(raster_source, target.lon, target.lat)
+  print ("evaluating segment: " .. sourceData.datum .. " " .. targetData.datum)
+  local invalid = sourceData.invalid_data()
+
+  if sourceData.datum ~= invalid and targetData.datum ~= invalid then
+    local slope = math.abs(sourceData.datum - targetData.datum) / distance
+    print ("   slope: " .. slope)
+    print ("   was speed: " .. weight.speed)
+
+    weight.speed = weight.speed * (1 - (slope * 5))
+    print ("   new speed: " .. weight.speed)
+  end
+end

profiles/rasterbot.lua

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+-- Rasterbot profile
+
+-- Minimalist node_ and way_functions in order to test source_ and segment_functions
+
+function node_function (node, result)
+end
+
+function way_function (way, result)
+  local highway = way:get_value_by_key("highway")
+  local name = way:get_value_by_key("name")
+
+  if name then
+    result.name = name
+  end
+
+  result.forward_speed = 15
+  result.backward_speed = 15
+end
+
+function source_function ()
+  raster_source = sources:load(
+    "../test/rastersource.asc",
+    0,    -- lon_min
+    0.1,  -- lon_max
+    0,    -- lat_min
+    0.1,  -- lat_max
+    5,    -- nrows
+    4     -- ncols
+  )
+end
+
+function segment_function (source, target, distance, weight)
+  local sourceData = sources:query(raster_source, source.lon, source.lat)
+  local targetData = sources:query(raster_source, target.lon, target.lat)
+  print ("evaluating segment: " .. sourceData.datum .. " " .. targetData.datum)
+  local invalid = sourceData.invalid_data()
+
+  if sourceData.datum ~= invalid and targetData.datum ~= invalid then
+    local slope = math.abs(sourceData.datum - targetData.datum) / distance
+    print ("   slope: " .. slope)
+    print ("   was speed: " .. weight.speed)
+
+    weight.speed = weight.speed * (1 - (slope * 5))
+    print ("   new speed: " .. weight.speed)
+  end
+end