Enforce strict FIND destinations

2 files changed, 88 insertions, 19 deletions

diff --git a/lua/clever_f/destination_engine.lua b/lua/clever_f/destination_engine.lua
index 836d190..0ae2314 100644
--- a/lua/clever_f/destination_engine.lua
+++ b/lua/clever_f/destination_engine.lua
@@ -68,20 +68,6 @@ local function candidate_starts(request, origin)
   )
 end
 
-local function next_matching_start(request, origin)
-  local candidates = candidate_starts(request, origin)
-
-  while true do
-    local position, character = candidates()
-    if position == nil then
-      return nil
-    end
-    if request.plan.target_plan:matches(character, position, request.view) then
-      return position
-    end
-  end
-end
-
 local function regular_destination(request, target_position)
   local descriptor = request.plan.descriptor
   if descriptor.family == domain.Family.FIND then
@@ -106,13 +92,47 @@ local function target_destination(request, target_position)
   return regular_destination(request, target_position)
 end
 
+local function strict_destination(descriptor, destination, origin)
+  local comparison = domain.Position.compare(destination, origin)
+  if descriptor.direction == domain.Direction.FORWARD then
+    return comparison > 0
+  end
+  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)
+  end
+  return true
+end
+
+local function next_destination(request, origin)
+  local candidates = candidate_starts(request, origin)
+
+  while true do
+    local target_position, character = candidates()
+    if target_position == nil then
+      return nil
+    end
+    if request.plan.target_plan:matches(
+      character,
+      target_position,
+      request.view
+    ) then
+      local destination = target_destination(request, target_position)
+      if destination ~= nil
+        and acceptable_destination(request, destination, origin)
+      then
+        return destination
+      end
+    end
+  end
+end
+
 function DestinationEngine:calculate(view, origin, plan, count, first_move)
   local request = calculation_inputs(view, origin, plan, count, first_move)
-  local target_position = next_matching_start(request, request.origin)
-  if target_position == nil then
-    return domain.SearchOutcome.boundary_before_any(request.origin)
-  end
-  local destination = target_destination(request, target_position)
+  local destination = next_destination(request, request.origin)
   if destination == nil then
     return domain.SearchOutcome.boundary_before_any(request.origin)
   end
diff --git a/tests/run.lua b/tests/run.lua
index 60d6b5b..1f9b9da 100644
--- a/tests/run.lua
+++ b/tests/run.lua
@@ -2569,6 +2569,55 @@ test("MotionPlanFactory limits exclusive policy to character and line Visual", f
   )
 end)
 
+test("FIND requires destinations on the strict motion side", function()
+  local view = text_topology.new({ "axa" }, "utf-8")
+  local engine = destination_engine.new()
+  local target_match = target_plan.build(target("a"), matching_policy())
+  local forward = motion_plan.build(target_match, "f")
+  local backward = motion_plan.build(target_match, "F")
+
+  same(
+    domain.Position.new(1, 3),
+    engine:calculate(
+      view,
+      domain.Position.new(1, 1),
+      forward,
+      1,
+      true
+    ).endpoint
+  )
+  same(
+    domain.Position.new(1, 1),
+    engine:calculate(
+      view,
+      domain.Position.new(1, 3),
+      backward,
+      1,
+      true
+    ).endpoint
+  )
+  same(
+    domain.SearchStatus.BOUNDARY_BEFORE_ANY,
+    engine:calculate(
+      view,
+      domain.Position.new(1, 3),
+      forward,
+      1,
+      false
+    ).status
+  )
+  same(
+    domain.SearchStatus.BOUNDARY_BEFORE_ANY,
+    engine:calculate(
+      view,
+      domain.Position.new(1, 1),
+      backward,
+      1,
+      false
+    ).status
+  )
+end)
+
 for _, item in ipairs(tests) do
   local ok, failure = xpcall(item.body, debug.traceback)
   if not ok then