operation

type Callbacks interface {

	// AcquireExecutionLock acquires the machine-level execution lock, and
	// returns a func that must be called to unlock it. It's used by all the
	// operations that execute external code.
	AcquireExecutionLock(message string) (unlock func(), err error)

	// PrepareHook and CommitHook exist so that we can defer worrying about how
	// to untangle Uniter.relationers from everything else. They're only used by
	// RunHook operations.
	PrepareHook(info hook.Info) (name string, err error)
	CommitHook(info hook.Info) error

	// UpdateRelations exists so that we can encapsulate it in an operation.
	UpdateRelations(ids []int) error

	// NotifyHook* exist so that we can defer worrying about how to untangle the
	// callbacks inserted for uniter_test. They're only used by RunHook operations.
	NotifyHookCompleted(string, runner.Context)
	NotifyHookFailed(string, runner.Context)

	// InitializeMetricsCollector ensures that the collect-metrics hook timer is
	// up to date given the current deployed charm. It's only used in deploy
	// operations.
	InitializeMetricsCollector() error

	// FailAction marks the supplied action failed. It's only used by
	// RunActions operations.
	FailAction(actionId, message string) error

	// GetArchiveInfo is used to find out how to download a charm archive. It's
	// only used by Deploy operations.
	GetArchiveInfo(charmURL *corecharm.URL) (charm.BundleInfo, error)

	// SetCurrentCharm records intent to deploy a given charm. It must be called
	// *before* recording local state referencing that charm, to ensure there's
	// no path by which the state server can legitimately garbage collect that
	// charm or the service's settings for it. It's only used by Deploy operations.
	SetCurrentCharm(charmURL *corecharm.URL) error

	// ClearResolvedFlag notifies the state server that the uniter has accepted
	// the resolved attempt and is trying to progress. It's only used by Resolved
	// operations (which we generally expect to wrap other operations).
	ClearResolvedFlag() error
}

type CommandArgs struct {
	// Commands is the arbitrary commands to execute on the unit
	Commands string
	// RelationId is the relation context to execute the commands in.
	RelationId int
	// RemoteUnitName is the remote unit for the relation context.
	RemoteUnitName string
	// ForceRemoteUnit skips unit inference and existence validation.
	ForceRemoteUnit bool
}

type CommandResponseFunc func(*utilexec.ExecResponse, error)

type Executor interface {

	// State returns a copy of the executor's current operation state.
	State() State

	// Run will Prepare, Execute, and Commit the supplied operation, writing
	// indicated state changes between steps. If any step returns an unknown
	// error, the run will be aborted and an error will be returned.
	Run(Operation) error

	// Skip will Commit the supplied operation, and write any state change
	// indicated. If Commit returns an error, so will Skip.
	Skip(Operation) error
}

type Factory interface {

	// NewInstall creates an install operation for the supplied charm.
	NewInstall(charmURL *corecharm.URL) (Operation, error)

	// NewUpgrade creates an upgrade operation for the supplied charm.
	NewUpgrade(charmURL *corecharm.URL) (Operation, error)

	// NewRevertUpgrade creates an operation to clear the unit's resolved flag,
	// and execute an upgrade to the supplied charm that is careful to excise
	// remnants of a previously failed upgrade to a different charm.
	NewRevertUpgrade(charmURL *corecharm.URL) (Operation, error)

	// NewResolvedUpgrade creates an operation to clear the unit's resolved flag,
	// and execute an upgrade to the supplied charm that is careful to preserve
	// non-overlapping remnants of a previously failed upgrade to the same charm.
	NewResolvedUpgrade(charmURL *corecharm.URL) (Operation, error)

	// NewRunHook creates an operation to execute the supplied hook.
	NewRunHook(hookInfo hook.Info) (Operation, error)

	// NewRetryHook creates an operation to clear the unit's resolved flag, and
	// re-execute the supplied hook.
	NewRetryHook(hookInfo hook.Info) (Operation, error)

	// NewSkipHook creates an operation to clear the unit's resolved flag, and
	// mark the supplied hook as completed successfully.
	NewSkipHook(hookInfo hook.Info) (Operation, error)

	// NewAction creates an operation to execute the supplied action.
	NewAction(actionId string) (Operation, error)

	// NewCommands creates an operation to execute the supplied script in the
	// indicated relation context, and pass the results back over the supplied
	// func.
	NewCommands(args CommandArgs, sendResponse CommandResponseFunc) (Operation, error)

	// NewUpdateRelations creates an operation to ensure the supplied relation
	// ids are known and tracked.
	NewUpdateRelations(ids []int) (Operation, error)
}

type Kind string

type Operation interface {

	// String returns a short representation of the operation.
	String() string

	// Prepare ensures that the operation is valid and ready to be executed.
	// If it returns a non-nil state, that state will be validated and recorded.
	// If it returns ErrSkipExecute, it indicates that the operation can be
	// committed directly.
	Prepare(state State) (*State, error)

	// Execute carries out the operation. It must not be called without having
	// called Prepare first. If it returns a non-nil state, that state will be
	// validated and recorded.
	Execute(state State) (*State, error)

	// Commit ensures that the operation's completion is recorded. If it returns
	// a non-nil state, that state will be validated and recorded.
	Commit(state State) (*State, error)
}

type State struct {
	// Started indicates whether the start hook has run.
	Started bool `yaml:"started"`

	// Kind indicates the current operation.
	Kind Kind `yaml:"op"`

	// Step indicates the current operation's progression.
	Step Step `yaml:"opstep"`

	// Hook holds hook information relevant to the current operation. If Kind
	// is Continue, it holds the last hook that was executed; if Kind is RunHook,
	// it holds the running hook; if Kind is Upgrade, a non-nil hook indicates
	// that the uniter should return to that hook's Pending state after the
	// upgrade is complete (instead of running an upgrade-charm hook).
	Hook *hook.Info `yaml:"hook,omitempty"`

	// ActionId holds action information relevant to the current operation. If
	// Kind is Continue, it holds the last action that was executed; if Kind is
	// RunAction, it holds the running action.
	ActionId *string `yaml:"action-id,omitempty"`

	// Charm describes the charm being deployed by an Install or Upgrade
	// operation, and is otherwise blank.
	CharmURL *charm.URL `yaml:"charm,omitempty"`

	// CollectMetricsTime records the time the collect metrics hook was last run.
	// It's set to nil if the hook was not run at all. Recording time as int64
	// because the yaml encoder cannot encode the time.Time struct.
	CollectMetricsTime int64 `yaml:"collectmetricstime,omitempty"`
}

type StateFile struct {
	// contains filtered or unexported fields
}

type Step string