// deno-lint-ignore-file no-explicit-any
// import 'https://cdn.skypack.dev/@cloudflare/workers-types@3.11.0?dts'
import type { StorageArea, AllowedKey, Key } from 'https://ghuc.cc/qwtel/kv-storage-interface/index.d.ts';

import { encodeKey, decodeKey, throwForDisallowedKey } from 'https://cdn.skypack.dev/idb-key-to-string?dts';

import { KVPacker, StructuredPacker } from './packer.ts';

const OLD_DEFAULT_KV_NAMESPACE_KEY = 'CF_STORAGE_AREA__DEFAULT_KV_NAMESPACE';
const DEFAULT_KV_NAMESPACE_KEY = 'DEFAULT_KV_NAMESPACE';
const DEFAULT_STORAGE_AREA_NAME = 'default';
const DIV = '/';

const getProcessEnv = (k: string) => Reflect.get(Reflect.get(Reflect.get(self, 'process') || {}, 'env') || {}, k);

/**
 * An implementation of the `StorageArea` interface wrapping Cloudflare Worker's KV store.
 * 
 * The goal of this class is ease of use and compatibility with other Storage Area implementations, 
 * such as <https://github.com/GoogleChromeLabs/kv-storage-polyfill>.
 * 
 * While work on [the specification](https://wicg.github.io/kv-storage/) itself has stopped, 
 * it's still a good interface for asynchronous data access that feels native to JavaScript.
 * 
 * Note that efficiency is not a goal. Specifically, if you have sizable `ArrayBuffer`s,
 * it's much better to use Cloudflare's KV directly.
 */
export class CloudflareStorageArea implements StorageArea {
  // @ts-ignore: deno only
  #kv: KVNamespace;
  #packer: KVPacker;
  #encodeKey: typeof encodeKey;
  #decodeKey: typeof decodeKey;
  #paginationHelper: typeof paginationHelper;

  // @ts-ignore: deno only
  static defaultKVNamespace?: KVNamespace;

  constructor(name?: string, opts?: KVOptions);
  // @ts-ignore: deno only
  constructor(name?: KVNamespace, opts?: Omit<KVOptions, 'namespace'>);
  // @ts-ignore: deno only
  constructor(name: string | KVNamespace = DEFAULT_STORAGE_AREA_NAME, options: KVOptions = {}) {
    let { namespace, packer = new StructuredPacker() } = options;

    namespace = namespace
      || CloudflareStorageArea.defaultKVNamespace
      || Reflect.get(self, Reflect.get(self, DEFAULT_KV_NAMESPACE_KEY))
      || Reflect.get(self, Reflect.get(self, OLD_DEFAULT_KV_NAMESPACE_KEY))
      || Reflect.get(self, getProcessEnv(DEFAULT_KV_NAMESPACE_KEY));

    this.#kv = namespace
      ? namespace
      : typeof name === 'string'
        ? Reflect.get(self, name)
        : name;

    if (!this.#kv) {
      throw Error('KV binding missing. Consult Workers documentation for details');
    }

    this.#encodeKey = !namespace
      ? encodeKey
      : k => `${name}${DIV}${encodeKey(k)}`;

    this.#decodeKey = !namespace
      ? decodeKey
      : k => decodeKey(k.substring((name as string).length + 1));

    this.#paginationHelper = !namespace
      ? paginationHelper
      : (kv, { prefix, ...opts } = {}) => paginationHelper(kv, {
        prefix: `${name}${DIV}${prefix ?? ''}`,
        ...opts,
      });

    this.#packer = packer;
  }

  get<T>(key: AllowedKey, opts?: unknown): Promise<T> {
    throwForDisallowedKey(key);
    return this.#packer.get(this.#kv, this.#encodeKey(key), opts);
  }

  async set<T>(key: AllowedKey, value: T | undefined, opts?: KVPutOptions): Promise<void> {
    throwForDisallowedKey(key);
    if (value === undefined)
      await this.#kv.delete(this.#encodeKey(key));
    else {
      await this.#packer.set(this.#kv, this.#encodeKey(key), value, opts);
    }
  }

  delete(key: AllowedKey) {
    throwForDisallowedKey(key);
    return this.#kv.delete(this.#encodeKey(key));
  }

  async clear(opts?: KVListOptions) {
    for await (const key of this.#paginationHelper(this.#kv, opts)) {
      await this.#kv.delete(key)
    }
  }

  async *keys(opts?: KVListOptions): AsyncGenerator<Key> {
    for await (const key of this.#paginationHelper(this.#kv, opts)) {
      yield this.#decodeKey(key);
    }
  }

  async *values<T>(opts?: KVListOptions): AsyncGenerator<T> {
    for await (const key of this.#paginationHelper(this.#kv, opts)) {
      yield this.#packer.get(this.#kv, key, opts);
    }
  }

  async *entries<T>(opts?: KVListOptions): AsyncGenerator<[Key, T]> {
    for await (const key of this.#paginationHelper(this.#kv, opts)) {
      yield [this.#decodeKey(key), await this.#packer.get(this.#kv, key, opts)];
    }
  }

  backingStore() {
    return this.#kv;
  }
}

export interface KVOptions {
  // @ts-ignore: deno only
  namespace?: KVNamespace;
  /** @deprecated This feature is not stable yet. */
  packer?: KVPacker;
  [k: string]: any;
}

export interface KVPutOptions {
  expiration?: string | number;
  expirationTtl?: string | number;
  [k: string]: any;
}

export interface KVListOptions {
  prefix?: string
  [k: string]: any;
}

/** Abstracts Cloudflare KV's cursor-based pagination with async iteration. */
// @ts-ignore: deno only
async function* paginationHelper(kv: KVNamespace, opts: KVListOptions = {}) {
  let keys: { name: string; expiration?: number; metadata?: unknown }[];
  let done: boolean;
  let cursor: string | undefined;
  do {
    ({ keys, list_complete: done, cursor } = await kv.list({ ...cursor ? { ...opts, cursor } : opts }));
    for (const { name } of keys) yield name;
  } while (!done);
}

/** @deprecated for backwards compat with v0.2.0 */
export class KVStorageArea extends CloudflareStorageArea { }

export type { AllowedKey, Key };
export { CloudflareStorageArea as CFStorageArea };
export { CloudflareStorageArea as StorageArea };