# `DiffoExample.Access.Calculations.ShelfTotalPorts`
[🔗](https://github.com/diffo-dev/diffo_example/blob/v0.4.0/lib/access/calculations/shelf_total_ports.ex#L5)

Sums the `:ports` pool capacity across every card a shelf has assigned
a slot to.

For each outgoing slot-assignment (cards consumer-alias their upstream
Shelf relationship as `:shelf`), looks up the assigned card's
`AssignableCharacteristic` for the `:ports` pool and sums
`(last - first + 1)` across all of them.

Local-to-this-repo for now. Could in time become a more general
diffo-side primitive (`SumPoolCapacityOfAssignees` or similar) once the
pattern repeats; the cleanest path may also be an ash_neo4j aggregate
primitive that walks assignment edges natively. Worth its own yarn.

# `describe`

# `has_calculate?`

# `has_expression?`

# `init`

# `strict_loads?`

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*Consult [api-reference.md](api-reference.md) for complete listing*