Accept initial stationary TILL destinations

2 files changed, 61 insertions, 7 deletions

diff --git a/lua/clever_f/destination_engine.lua b/lua/clever_f/destination_engine.lua
index 0ae2314..e3a7fc1 100644
--- a/lua/clever_f/destination_engine.lua
+++ b/lua/clever_f/destination_engine.lua
@@ -100,14 +100,22 @@ local function strict_destination(descriptor, destination, origin)
   return comparison < 0
 end
 
-local function acceptable_destination(request, destination, origin)
-  if request.plan.descriptor.family == domain.Family.FIND then
-    return strict_destination(request.plan.descriptor, destination, origin)
+local function acceptable_destination(
+  request,
+  destination,
+  origin,
+  allow_till_equality
+)
+  local descriptor = request.plan.descriptor
+  if strict_destination(descriptor, destination, origin) then
+    return true
   end
-  return true
+  return descriptor.family == domain.Family.TILL
+    and allow_till_equality
+    and domain.Position.equal(destination, origin)
 end
 
-local function next_destination(request, origin)
+local function next_destination(request, origin, allow_till_equality)
   local candidates = candidate_starts(request, origin)
 
   while true do
@@ -122,7 +130,12 @@ local function next_destination(request, origin)
     ) then
       local destination = target_destination(request, target_position)
       if destination ~= nil
-        and acceptable_destination(request, destination, origin)
+        and acceptable_destination(
+          request,
+          destination,
+          origin,
+          allow_till_equality
+        )
       then
         return destination
       end
@@ -132,7 +145,11 @@ end
 
 function DestinationEngine:calculate(view, origin, plan, count, first_move)
   local request = calculation_inputs(view, origin, plan, count, first_move)
-  local destination = next_destination(request, request.origin)
+  local destination = next_destination(
+    request,
+    request.origin,
+    request.first_move
+  )
   if destination == nil then
     return domain.SearchOutcome.boundary_before_any(request.origin)
   end
diff --git a/tests/run.lua b/tests/run.lua
index 1f9b9da..fc89801 100644
--- a/tests/run.lua
+++ b/tests/run.lua
@@ -2618,6 +2618,43 @@ test("FIND requires destinations on the strict motion side", function()
   )
 end)
 
+test("First TILL moves accept an adjacent stationary destination", function()
+  local engine = destination_engine.new()
+  local forward_view = text_topology.new({ "ab" }, "utf-8")
+  local forward = motion_plan.build(
+    target_plan.build(target("b"), matching_policy()),
+    "t"
+  )
+  local forward_origin = domain.Position.new(1, 1)
+  local forward_outcome = engine:calculate(
+    forward_view,
+    forward_origin,
+    forward,
+    1,
+    true
+  )
+  same(domain.SearchStatus.COMPLETE, forward_outcome.status)
+  same(forward_origin, forward_outcome.endpoint)
+  same(1, forward_outcome.successful_steps)
+
+  local backward_view = text_topology.new({ "ba" }, "utf-8")
+  local backward = motion_plan.build(
+    target_plan.build(target("b"), matching_policy()),
+    "T"
+  )
+  local backward_origin = domain.Position.new(1, 2)
+  local backward_outcome = engine:calculate(
+    backward_view,
+    backward_origin,
+    backward,
+    1,
+    true
+  )
+  same(domain.SearchStatus.COMPLETE, backward_outcome.status)
+  same(backward_origin, backward_outcome.endpoint)
+  same(1, backward_outcome.successful_steps)
+end)
+
 for _, item in ipairs(tests) do
   local ok, failure = xpcall(item.body, debug.traceback)
   if not ok then