"DepotSafety.bist"
package: com.ecodepot.storage;

"DepotSafety class responsibilities:<ul>
<li>allocates storage drums to available storage space,</li>
<li>applies depot safety policies during storage allocation.</li>
</ul><p></p>

@author Copyright 2004 Nikolas S. Boyd. All rights reserved."

Object subclass: DepotSafety
metaclass: [

"allocating storage space"

	"Allocates drums to depot storage buildings that contain hazardous chemicals of a certain kind.
	Returns the resulting allocations."
	allocate: drumCount containing: hazard [

		prospects := StorageAllocation prospectsContaining: hazard.

		allocations := self distribute: drumCount over: prospects. "initial naive allocations"
		allocations isEmpty ifTrue: [ ^allocations ]. "done if no allocations were possible"

		vulnerabilities := self vulnerable: allocations with: prospects.
		vulnerabilities isEmpty ifTrue: [ ^allocations ]. "done if no (new) vulnerabilities exist"

		^self reduce: vulnerabilities using: prospects producing: allocations
	]

	"Distributes drums over some allocations based on their storage capacity.
	Returns the allocations to which drums were assigned."
	distribute: drumCount over: allocations [

		result := OrderedCollection new.
		totalCapacity := StorageAllocation capacityOfBuildings: allocations.

		allocations inject: (drumCount min: totalCapacity)
			into: [ :remainingDrums :allocation |
				remainingDrums = 0 ifTrue: [ ^result ].
				result add: allocation.
				allocation remainderAfterConsumingSome: remainingDrums ].

		^result "should never reach here, but ..."
	]

"reducing vulnerability"

	"Returns those allocations that make the depot vulnerable with other prospects."
	vulnerable: allocations with: prospects [
		^allocations select: [ :allocation |
			allocation makesDepotVulnerableWith: prospects ]
	]

	"Reduces the drums assigned to some vulnerable allocations by transfering a single drum
	from each to another prospective allocation which has some remaining storage capacity.
	Adds each resulting prospect to the final allocations and returns the resulting allocations."
	reduce: vulnerabilities using: prospects producing: allocations [

		availableProspects := self safeStorageProspects: prospects.
		[ availableProspects isEmpty or: [ vulnerabilities isEmpty ]] whileFalse: [
			allocations add: (self reduce: vulnerabilities using: availableProspects removeFirst).
		].
		^allocations
	]

	"Reduces the drums assigned to some full allocations by transfering a single drum 
	from each to another prospective allocation which has some remaining storage capacity.
	Returns the resulting prospective allocation."
	reduce: vulnerabilities using: availableProspect [

		((availableProspect remainingStorageCapacity - 1) min: vulnerabilities size) 
			timesRepeat: [ vulnerabilities removeFirst transferDrums: 1 to: availableProspect ].

		^availableProspect
	]

"ensuring safety"

	"Returns the prospects that have safe storage capacity."
	safeStorageProspects: allocations [
		^allocations select: [ :allocation | allocation fillsBuilding not ]
	]

	"Returns the building vulnerability perimeter distance."
	vulnerabilityPerimeter [
		^Meter distance: 5.0
	]
]

class: [

] "DepotSafety"