import { utf8ToBytes } from '@ethereumjs/util'

import type { DB, ValueEncoding } from '@ethereumjs/util'

/** Options for {@link createBinaryTree} and {@link BinaryTree}. */
export interface BinaryTreeOpts {
  /**
   * A database instance.
   */
  db: DB<string, string | Uint8Array>

  /**
   * A `Uint8Array` for the root of a previously stored tree
   */
  root?: Uint8Array

  /**
   * Store the root inside the database after every `write` operation
   */
  useRootPersistence: boolean

  /**
   * LRU cache for tree nodes to allow for faster node retrieval.
   *
   * Default: 0 (deactivated)
   */
  cacheSize: number

  /**
   * Hash function used for hashing the tree nodes.
   */
  hashFunction: (msg: Uint8Array) => Uint8Array
}

export interface CheckpointDBOpts {
  /**
   * A database instance.
   */
  db: DB<string, string | Uint8Array>

  /**
   * ValueEncoding of the database (the values which are `put`/`get` in the db are of this type). Defaults to `string`
   */
  valueEncoding?: ValueEncoding

  /**
   * Cache size (default: 0)
   */
  cacheSize?: number
}

export type Checkpoint = {
  // We cannot use a Uint8Array => Uint8Array map directly. If you create two Uint8Arrays with the same internal value,
  // then when setting a value on the Map, it actually creates two indices.
  keyValueMap: Map<string, Uint8Array | undefined>
  root: Uint8Array
}

/** Internal DB key used when `useRootPersistence` stores the tree root. */
export const ROOT_DB_KEY = utf8ToBytes('__root__')