inventory v1

Accounts

Account	One for each	Unit	Bounds	What it is
`stock`	`sku`	pcs	at least 0; a transfer that would go below is refused with `out_of_stock`	what is on the shelves
`suppliers`	one account	pcs	outside the book: no bounds, and it may go below 0
`customers`	one account	pcs	outside the book: no bounds, and it may go below 0

How things move

A box is an account, and an arrow a move of a transfer. A rounded, dashed box is an account outside the book, which has no bounds. A dashed arrow belongs to a transfer that holds first, and moves when the hold is posted.

Transfers

receive

Moves qty from suppliers to stock(sku).
Key: once per delivery and sku. The same call again does nothing, and answers done_before; one that differs only in qty is refused with key_conflict.
Moves at once (do).

Operation	May be refused with	When
`receive.do`	`key_conflict`	a call with the same `delivery` and `sku` and other arguments came before

How each refusal comes about

receive.do: key_conflict

 1  receive.do(delivery: delivery-1, sku: sku-2, qty: 1)  done
 2  receive.do(delivery: delivery-1, sku: sku-2, qty: 2)  refused: key_conflict

reserve

posted when the order ships, voided when it is cancelled

Moves qty from stock(sku) to customers.
Key: once per order and sku. The same call again does nothing, and answers done_before; one that differs only in qty is refused with key_conflict; holding again with the same key after the hold has ended answers done_before, and holds nothing.
Holds first: the caller posts or voids the hold. It expires 30 minutes after it was made, and what it holds goes back.

The hold	post	void
held	posts it: the amounts given, or all of it, and the rest goes back; more than it holds is refused with `over_hold`; once 30 minutes have passed since it was held, refused with `expired`	voids it: what it holds goes back; once 30 minutes have passed since it was held, refused with `expired`
posted	`done_before` with the same amounts; refused with `key_conflict` with others	refused with `already_posted`
voided	refused with `already_voided`	`done_before`
expired	refused with `expired`	refused with `expired`
no hold with the key	refused with `no_such_hold`	refused with `no_such_hold`

Operation	May be refused with	When
`reserve.hold`	`out_of_stock`	`stock(sku)` would go below 0
`reserve.hold`	`key_conflict`	a call with the same `order` and `sku` and other arguments came before
`reserve.hold`	`already_refused`	a call with the same `order` and `sku` was refused by a bound before; a key a bound refused stays refused, even once there is enough
`reserve.post`	`key_conflict`	the hold was posted before, for other amounts
`reserve.post`	`already_voided`	the hold is voided already
`reserve.post`	`expired`	the hold has expired
`reserve.post`	`over_hold`	more than the hold holds
`reserve.post`	`no_such_hold`	there is no hold with that `order` and `sku`
`reserve.void`	`already_posted`	the hold is posted already
`reserve.void`	`expired`	the hold has expired
`reserve.void`	`no_such_hold`	there is no hold with that `order` and `sku`

How each refusal comes about

reserve.hold: out_of_stock

 1  reserve.hold(order: order-1, sku: sku-2, qty: 1)  refused: out_of_stock (move 1 takes 1 from stock(sku-2): posted 0, held out 0)

reserve.hold: key_conflict

 1  receive.do(delivery: delivery-1, sku: sku-2, qty: 1)  done
 2  reserve.hold(order: order-3, sku: sku-2, qty: 1)      done
 3  reserve.hold(order: order-3, sku: sku-2, qty: 2)      refused: key_conflict

reserve.hold: already_refused

 1  reserve.hold(order: order-1, sku: sku-2, qty: 1)  refused: out_of_stock (move 1 takes 1 from stock(sku-2): posted 0, held out 0)
 2  reserve.hold(order: order-1, sku: sku-2, qty: 1)  refused: already_refused

reserve.post: key_conflict

 1  receive.do(delivery: delivery-1, sku: sku-2, qty: 2)  done
 2  reserve.hold(order: order-3, sku: sku-2, qty: 2)      done
 3  reserve.post(order: order-3, sku: sku-2)              done
 4  reserve.post(order: order-3, sku: sku-2, qty: 1)      refused: key_conflict

reserve.post: already_voided

 1  receive.do(delivery: delivery-1, sku: sku-2, qty: 2)  done
 2  reserve.hold(order: order-3, sku: sku-2, qty: 2)      done
 3  reserve.void(order: order-3, sku: sku-2)              done
 4  reserve.post(order: order-3, sku: sku-2)              refused: already_voided

reserve.post: expired

 1  receive.do(delivery: delivery-1, sku: sku-2, qty: 2)  done
 2  reserve.hold(order: order-3, sku: sku-2, qty: 2)      done
 3  pass 30 minutes                                       reserve(order-3, sku-2) expired
 4  reserve.post(order: order-3, sku: sku-2)              refused: expired

reserve.post: over_hold

 1  receive.do(delivery: delivery-1, sku: sku-2, qty: 2)  done
 2  reserve.hold(order: order-3, sku: sku-2, qty: 2)      done
 3  reserve.post(order: order-3, sku: sku-2, qty: 3)      refused: over_hold

reserve.post: no_such_hold

 1  reserve.post(order: order-1, sku: sku-2)  refused: no_such_hold

reserve.void: already_posted

 1  receive.do(delivery: delivery-1, sku: sku-2, qty: 2)  done
 2  reserve.hold(order: order-3, sku: sku-2, qty: 2)      done
 3  reserve.post(order: order-3, sku: sku-2)              done
 4  reserve.void(order: order-3, sku: sku-2)              refused: already_posted

reserve.void: expired

 1  receive.do(delivery: delivery-1, sku: sku-2, qty: 2)  done
 2  reserve.hold(order: order-3, sku: sku-2, qty: 2)      done
 3  pass 30 minutes                                       reserve(order-3, sku-2) expired
 4  reserve.void(order: order-3, sku: sku-2)              refused: expired

reserve.void: no_such_hold

 1  reserve.void(order: order-1, sku: sku-2)  refused: no_such_hold

take_back

what a customer sent back, on the shelves again

Moves qty from customers to stock(sku).
Key: once per return_id and sku. The same call again does nothing, and answers done_before; one that differs only in qty is refused with key_conflict.
Moves at once (do).

Operation	May be refused with	When
`take_back.do`	`key_conflict`	a call with the same `return_id` and `sku` and other arguments came before

How each refusal comes about

take_back.do: key_conflict

 1  take_back.do(return_id: return_id-1, sku: sku-2, qty: 1)  done
 2  take_back.do(return_id: return_id-1, sku: sku-2, qty: 2)  refused: key_conflict

Scenarios

21 scenarios, which chobo scenarios makes from the book. Pick one and step through it: after each step come the balances and the holds it left, and on the chart the arrows of the transfers it called light up (red when refused).

Scenario

Account	Posted	Held out	Held in

Hold	State