tmanager

type Handler interface {
	// HandleTask handler of the task.
	HandleTask(ctx context.Context, data json.RawMessage) error
}

type HandlerCallback interface {
	Handler
	// CallbackTask called after saved task state.
	CallbackTask(ctx context.Context, task Task, handlerErr error)
}

type HandlerCallbackFunc func(ctx context.Context, task Task, handlerErr error)

type HandlerFunc func(ctx context.Context, data json.RawMessage) error

type Storage interface {
	// CreateTasks creates list of the tasks in the storage.
	// Task field ID must be empty.
	CreateTasks(ctx context.Context, tasks ...Task) error

	// CreateOneActiveTask checks that task already exists in storage.
	// If the task does not exist in the storage, a new task is created.
	CreateOneActiveTask(ctx context.Context, task Task) error

	// GetNextTask returns the oldest task that the worker has not yet taken to work.
	// Value of the StartAfter must be less then "now" argument.
	// Returns error ErrTaskNotFound when storage can't found task.
	GetNextTask(ctx context.Context, now time.Time) (Task, error)

	// RestartTask makes the task free to re-taking in GetNextTask method.
	// You have to set time to re-taking.
	RestartTask(ctx context.Context, task Task, restartAfter time.Time) error

	// SaveTaskWithSuccess saves success done task.
	// If the context is canceled, then ctx will be the default context.Background here
	// to be sure to save the task state. See ReplaceCanceledContext method in TaskManager.
	SaveTaskWithSuccess(ctx context.Context, task Task) error
	// SaveTaskWithError saves task with error.
	// If the context is canceled, then ctx will be the default context.Background here
	// to be sure to save the task state. See ReplaceCanceledContext method in TaskManager.
	SaveTaskWithError(ctx context.Context, task Task, taskErr error) error
}

type Task interface {
	GetID() string            // Unique identification of the task.
	GetStartAfter() time.Time // Time after which the task should be started.
	GetHandler() string       // Name of the task handler.
	GetData() json.RawMessage // Data of the handler.
}

type TaskImpl struct {
	ID         string
	StartAfter time.Time
	Handler    string
	Data       json.RawMessage
}

type TaskManager struct {
	Logger  *log.Logger // Writes errors of interaction with the Storage.
	Storage Storage

	WorkersNum          int
	GetNextTaskInterval time.Duration

	// BeforeHandler calls before each task handler.
	// You can use it to add your data to context or to stop handling task.
	// Example:
	//    tm.BeforeHandler = func(ctx context.Context, task *tmanager.Task) (context.Context, error) {
	//    return context.WithValue(ctx, "task", task), nil
	//  }
	BeforeHandler func(ctx context.Context, task Task) (context.Context, error)

	// ReplaceCanceledContext calls before SaveTaskWithSuccess, SaveTaskWithError and CreateTasks
	// methods if current context is canceled.
	// Raplaces current context with context.Background by default to remove cancel function from context.
	// This is necessary to be sure to save the state of tasks after handling them,
	// ignoring the cancellation of the context.
	// You can disable this feature by setting this method to nil.
	// Example:
	//  tm.ReplaceCanceledContext = func(ctx context.Context) context.Context {
	//    return context.WithValue(context.Background(), "old_data", ctx.Value("old_data"))
	//  }
	ReplaceCanceledContext func(ctx context.Context) context.Context
	// contains filtered or unexported fields
}