histutil

type Cursor interface {
	// Prev moves the cursor to the previous command.
	Prev()
	// Next moves the cursor to the next command.
	Next()
	// Get returns the command the cursor is currently at, or any error if the
	// cursor is in an invalid state. If the cursor is "over the edge", the
	// error is ErrEndOfHistory.
	Get() (store.Cmd, error)
}

type DB interface {
	NextCmdSeq() (int, error)
	AddCmd(cmd string) (int, error)
	CmdsWithSeq(from, upto int) ([]store.Cmd, error)
	PrevCmd(upto int, prefix string) (store.Cmd, error)
	NextCmd(from int, prefix string) (store.Cmd, error)
}

type FaultyInMemoryDB interface {
	DB
	// SetOneOffError causes the next operation on the database to return the
	// given error.
	SetOneOffError(err error)
}

type Store interface {
	// AddCmd adds a new command history entry and returns its sequence number.
	// Depending on the implementation, the Store might respect cmd.Seq and
	// return it as is, or allocate another sequence number.
	AddCmd(cmd store.Cmd) (int, error)
	// AllCmds returns all commands kept in the store.
	AllCmds() ([]store.Cmd, error)
	// Cursor returns a cursor that iterating through commands with the given
	// prefix. The cursor is initially placed just after the last command in the
	// store.
	Cursor(prefix string) Cursor
}