#light

namespace Internal.Utilities.Collections
  
  /// Simple aging lookup table. When a member is accessed it's
  /// moved to the top of the list and when there are too many elements
  /// the least-recently-accessed element falls of the end.
  type internal AgedLookup<'TKey,'TValue> = 
    new : keepStrongly:int
            * ?areSame:('TKey * 'TKey -> bool) 
            -> AgedLookup<'TKey,'TValue>
    /// Lookup the value without making it the most recent.
    /// Returns the original key value because the areSame function
    /// may have unified two different keys.
    member TryPeekKeyValue : key:'TKey -> ('TKey*'TValue) option
    /// Lookup a value and make it the most recent.
    /// Returns the original key value because the areSame function
    /// may have unified two different keys.
    member TryGetKeyValue : key:'TKey -> ('TKey*'TValue) option    
    /// Lookup a value and make it the most recent. Return None if it wasn't there.
    member TryGet : key:'TKey -> 'TValue option        
    /// Add an element to the collection. Make it the most recent.
    member Put : 'TKey*'TValue -> unit
    /// Remove the given value from the collection.
    member Remove : key:'TKey -> unit
    /// Get the most recent item if there is one.
    member MostRecent : ('TKey * 'TValue) option  
    /// Remove all elements.
    member Clear : unit -> unit
    
  /// Simple priority caching for a small number of key\value associations.
  /// This cache may age-out results that have been Set by the caller.
  /// Because of this, the caller must be able to tolerate values 
  /// that aren't what was originally passed to the Set function.         
  type internal MruCache<'TKey,'TValue> =
    new : n:int 
            * compute:('TKey -> 'TValue) 
            * ?areSame:('TKey * 'TKey -> bool) 
            * ?isStillValid:('TKey * 'TValue -> bool)
            * ?areSameForSubsumption:('TKey * 'TKey -> bool) 
            * ?logComputedNewValue:('TKey -> unit)
            * ?logUsedCachedValue:('TKey -> unit)
            -> MruCache<'TKey,'TValue>
    /// Clear out the cache.
    member Clear : unit -> unit
    /// Get the value for the given key. Compute if necessary.
    member Get : key:'TKey -> 'TValue
    /// Get the value for the given key or None if not already available
    member GetAvailable : key:'TKey -> 'TValue option
    /// Remove the given value from the mru cache.
    member Remove : key:'TKey -> unit
    /// Set the value for the given key. This value does not have to agree with computed value.           
    member SetAlternate : key:'TKey * value:'TValue -> unit
    /// Get the most recent item if there is one.
    member MostRecent : ('TKey * 'TValue) option