Ilia Denisov
80 lines
2.4 KiB
Go
80 lines
2.4 KiB
Go
package application
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// Status identifies one lifecycle state of a Game Lobby application record.
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type Status string
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const (
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// StatusSubmitted reports that the application was created by the
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// applicant and awaits admin decision.
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StatusSubmitted Status = "submitted"
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// StatusApproved reports that the admin accepted the application and
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// a membership record was created for the applicant.
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StatusApproved Status = "approved"
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// StatusRejected reports that the admin declined the application.
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// The applicant may submit a new application while enrollment is open.
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StatusRejected Status = "rejected"
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)
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// IsKnown reports whether status belongs to the frozen application status
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// vocabulary.
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func (status Status) IsKnown() bool {
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switch status {
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case StatusSubmitted, StatusApproved, StatusRejected:
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return true
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default:
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return false
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}
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}
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// IsTerminal reports whether status can no longer accept lifecycle
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// transitions.
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func (status Status) IsTerminal() bool {
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switch status {
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case StatusApproved, StatusRejected:
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return true
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default:
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return false
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}
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}
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// transitionKey stores one `(from, to)` pair in the allowed-transitions
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// table.
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type transitionKey struct {
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from Status
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to Status
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}
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// allowedTransitions stores the set of permitted `(from, to)` status pairs.
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// It mirrors the state machine frozen in lobby/README.md Application
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// Lifecycle section.
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var allowedTransitions = map[transitionKey]struct{}{
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{StatusSubmitted, StatusApproved}: {},
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{StatusSubmitted, StatusRejected}: {},
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}
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// AllowedTransitions returns a copy of the `(from, to)` allowed-transitions
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// table used by Transition. The returned map is safe to mutate.
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func AllowedTransitions() map[Status][]Status {
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result := make(map[Status][]Status)
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for key := range allowedTransitions {
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result[key.from] = append(result[key.from], key.to)
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}
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return result
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}
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// Transition reports whether from may transition to next. The function
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// returns nil when the pair is permitted, and an *InvalidTransitionError
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// wrapping ErrInvalidTransition otherwise. It does not touch any store and
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// is safe to call from any layer.
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func Transition(from Status, next Status) error {
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if !from.IsKnown() || !next.IsKnown() {
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return &InvalidTransitionError{From: from, To: next}
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}
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if _, ok := allowedTransitions[transitionKey{from: from, to: next}]; !ok {
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return &InvalidTransitionError{From: from, To: next}
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}
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return nil
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}
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