Add iterator for PossibleOperations data structure

src/operation/iterate.jl

@@ -0,0 +1,36 @@
+import Base.iterate
+
+const _POSSIBLE_OPERATIONS_FIELDS = fieldnames(PossibleOperations)
+
+function iterate(possibleOperations::PossibleOperations)
+    for fieldname in _POSSIBLE_OPERATIONS_FIELDS
+        iterator = iterate(getfield(possibleOperations, fieldname))
+        if (!isnothing(iterator))
+            return (result = iterator[1], state = (fieldname, iterator[2]))
+        end
+    end
+
+    return nothing
+end
+
+function iterate(possibleOperations::PossibleOperations, state)
+    newStateSym = state[1]
+    newStateIt = iterate(getfield(possibleOperations, newStateSym), state[2])
+    if !isnothing(newStateIt)
+        return (result = newStateIt[1], state = (newStateSym, newStateIt[2]))
+    end
+
+    # cycle to next field
+    index = findfirst(x -> x == newStateSym, _POSSIBLE_OPERATIONS_FIELDS) + 1
+
+    while index <= length(_POSSIBLE_OPERATIONS_FIELDS)
+        newStateSym = _POSSIBLE_OPERATIONS_FIELDS[index]
+        newStateIt = iterate(getfield(possibleOperations, newStateSym))
+        if !isnothing(newStateIt)
+            return (result = newStateIt[1], state = (newStateSym, newStateIt[2]))
+        end
+        index += 1
+    end
+
+    return nothing
+end