package store

import dbm "github.com/cosmos/cosmos-db"

// KVStore describes the basic interface for interacting with key-value stores.
type KVStore = interface {
	// Get returns nil iff key doesn't exist. Errors on nil key.
	Get(key []byte) ([]byte, error)

	// Has checks if a key exists. Errors on nil key.
	Has(key []byte) (bool, error)

	// Set sets the key. Errors on nil key or value.
	Set(key, value []byte) error

	// Delete deletes the key. Errors on nil key.
	Delete(key []byte) error

	// Iterator iterates over a domain of keys in ascending order. End is exclusive.
	// Start must be less than end, or the Iterator is invalid.
	// Iterator must be closed by caller.
	// To iterate over entire domain, use store.Iterator(nil, nil)
	// CONTRACT: No writes may happen within a domain while an iterator exists over it.
	// Exceptionally allowed for cachekv.Store, safe to write in the modules.
	Iterator(start, end []byte) (Iterator, error)

	// ReverseIterator iterates over a domain of keys in descending order. End is exclusive.
	// Start must be less than end, or the Iterator is invalid.
	// Iterator must be closed by caller.
	// CONTRACT: No writes may happen within a domain while an iterator exists over it.
	// Exceptionally allowed for cachekv.Store, safe to write in the modules.
	ReverseIterator(start, end []byte) (Iterator, error)
}

// Iterator is an alias db's Iterator for convenience.
type Iterator = dbm.Iterator
