Basic operations to track virtual merge on EHRs

ehr_mege.groovy

//ehrs = ['A', 'B', 'C', 'D', 'E', 'F']

// TODO: the canonical should be initialized with the identities: A: A, ... so when asking for the canonical of an unmerged EHR, it gives the same EHR back
canonical = [:]
history = []

// A => B : [A: B]
// C => B : [C: B, A: B]
// B => E : [C: E, A: E, B: E]
// merge secondaryEhr into primaryEhr
def merge(secondaryEhr, primaryEhr)
{
   // check the secondary isn't an already merged secondary to another primary
   if (canonical[secondaryEhr])
   {
      throw new Exception("Can't merge the secondary "+ secondaryEhr +" to "+ primaryEhr +", it's already merged to "+ canonical[secondaryEhr])
   }
   
   // if the primary is a secondary of another merge, can't merge because that "branch" isn't active, only can merge to the primary of another merge or to an independent "branch"
   if (canonical[primaryEhr])
   {
      throw new Exception("Can't merge into primary "+ primaryEhr +" because it's merged to another EHR already: "+ canonical[primaryEhr])
   }
   
   // if secondary is canonical (value) of previous merges, change those entries with the new primary
   def secondarySecondaries = canonical.findAll { it.value == secondaryEhr }
   
   if (secondarySecondaries)
   {
     secondarySecondaries.each { entry ->
       canonical[entry.key] = primaryEhr
     }
   }
   
   canonical[secondaryEhr] = primaryEhr
   history << [action: 'MERGE', secondary: secondaryEhr, primary: primaryEhr]
}

// unmerges secondaryEhr from primaryEhr
def unmerge(secondaryEhr)
{
   // check the secondary was the last merge into the primary
   def lastMerge = history.find { it.secondary == secondaryEhr }

   if (!lastMerge)
   {
      throw new Exception("EHR "+ secondaryEhr +" isn't merged")
   }
   
   println lastMerge
   
   
   // secondaryEhr can be the last merge into lastMerge.primary, though that primary can be merged to another primary, so can't unmerge either
   def mergedPrimary = history.findAll{ it.secondary == lastMerge.primary }
   
   println mergedPrimary
   
   if (mergedPrimary)
   {
      throw new Exception("Can't unmerge "+ secondaryEhr +" from "+ lastMerge.primary +": that EHR is merged into another ("+ mergedPrimary[0].primary +"), try unmerging that first")
   }
   
   
   // merges into primaryEhr
   def mergeHistory = history.findAll{ it.primary == lastMerge.primary }
   
   println mergeHistory
   
   
   def lastMergeIntoPrimary = mergeHistory.get(mergeHistory.size() -1)
   
   if (lastMergeIntoPrimary.secondary != secondaryEhr)
   {
      throw new Exception("Can't unmerge "+ secondaryEhr +": it's not the last merge into "+ lastMerge.primary +", it's "+ lastMergeIntoPrimary.secondary +", try unmerging that first")
   }
   
   // removes the canonical for secondaryEhr, keeping it as independent from the primary.
   canonical.remove(secondaryEhr)
   
   history << [action: 'UNMERGE', secondary: secondaryEhr, primary: lastMerge.primary]
}

merge('A', 'B')
merge('C', 'B')
merge('B', 'E')
//merge('B', 'F') // can't merge, secondary is a secondary of a previous merge, we can only merge an independent or primary into another primary
merge('E', 'D')
merge('F', 'D')
//merge('D', 'F') // can't merge, primary is a secondary of another merge, we can only merge into an independent or primary EHR

println canonical
println history


unmerge('F')

println canonical
println history