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library GroupUtils
//******************************************************************************
//* BY: Rising_Dusk
//* 
//* This library is a simple implementation of a stack for groups that need to
//* be in the user's control for greater than an instant of time. Additionally,
//* this library provides a single, global group variable for use with user-end
//* enumerations. It is important to note that users should not be calling
//* DestroyGroup() on the global group, since then it may not exist for when it
//* it is next needed.
//*
//* The group stack removes the need for destroying groups and replaces it with
//* a recycling method.
//*     function NewGroup takes nothing returns group
//*     function ReleaseGroup takes group g returns boolean
//*     function GroupRefresh takes group g returns nothing
//* 
//* NewGroup grabs a currently unused group from the stack or creates one if the
//* stack is empty. You can use this group however you'd like, but always
//* remember to call ReleaseGroup on it when you are done with it. If you don't
//* release it, it will 'leak' and your stack may eventually overflow if you
//* keep doing that.
//* 
//* GroupRefresh cleans a group of any shadow references which may be clogging
//* its hash table. If you remove a unit from the game who is a member of a unit
//* group, it will 'effectively' remove the unit from the group, but leave a
//* shadow in its place. Calling GroupRefresh on a group will clean up any
//* shadow references that may exist within it.
//* 
globals
    //* Group for use with all instant enumerations
    group ENUM_GROUP = CreateGroup()
    
    //* Temporary references for GroupRefresh
    private boolean Flag                                              = false
    private group Refr                                                = null
    
    //* Assorted constants
    private constant integer MAX_HANDLE_COUNT                         = 408000
    private constant integer MIN_HANDLE_ID                            = 0x100000
    
    //* Arrays and counter for the group stack
    private group array Groups
    private integer array Status[MAX_HANDLE_COUNT]
    private integer Count                                             = 0
endglobals

private function AddEx takes nothing returns nothing
    if Flag then
        call GroupClear(Refr)
        set Flag = false
    endif
    call GroupAddUnit(Refr, GetEnumUnit())
endfunction
    
function GroupRefresh takes group g returns nothing
    set Flag = true
    set Refr = g
    call ForGroup(Refr, function AddEx)
    if Flag then
        call GroupClear(g)
    endif
endfunction

function NewGroup takes nothing returns group
    if Count == 0 then
        set Groups[0] = CreateGroup()
    else
        set Count = Count - 1
    endif
    set Status[GetHandleId(Groups[Count])-MIN_HANDLE_ID] = 1
    return Groups[Count]
endfunction

function ReleaseGroup takes group g returns boolean
    local integer stat = Status[GetHandleId(g)-MIN_HANDLE_ID]
    local boolean b    = true
    if g == null then
        debug call BJDebugMsg(SCOPE_PREFIX+" Error: Null groups cannot be released")
        set b = false
    elseif stat == 0 then
        debug call BJDebugMsg(SCOPE_PREFIX+" Error: Group not part of stack")
        set b = false
    elseif stat == 2 then
        debug call BJDebugMsg(SCOPE_PREFIX+" Error: Groups cannot be multiply released")
        set b = false
    elseif Count == 8191 then
        debug call BJDebugMsg(SCOPE_PREFIX+" Error: Max groups achieved, destroying group")
        call DestroyGroup(g)
        set b = false
    else
        call GroupClear(g)
        set Groups[Count]                = g
        set Count                        = Count + 1
        set Status[GetHandleId(g)-MIN_HANDLE_ID] = 2
    endif
    return b
endfunction
endlibrary