diff --git a/src/Assurance/Cabal.idr b/src/Assurance/Cabal.idr
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+++ b/src/Assurance/Cabal.idr
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+module Assurance.Cabal
+
+%default total
+
+||| Evidence from the runner that will perform dependency resolution.
+public export
+data IndexState = Unknown | Available | Missing
+
+||| A cache restore alone cannot establish index availability.
+public export
+data BuildPlan = RefreshThenResolve | Resolve
+
+public export
+planOnlineBuild : IndexState -> BuildPlan
+planOnlineBuild Available = Resolve
+planOnlineBuild Missing = RefreshThenResolve
+planOnlineBuild Unknown = RefreshThenResolve
+
+missingRefreshes : planOnlineBuild Missing = RefreshThenResolve
+missingRefreshes = Refl
+
+unknownRefreshes : planOnlineBuild Unknown = RefreshThenResolve
+unknownRefreshes = Refl
+
+availableResolves : planOnlineBuild Available = Resolve
+availableResolves = Refl