import { identify } from "./identify.ts";
import { handleMessage } from "./handleMessage.ts";
import {
  DEFAULT_HEARTBEAT_INTERVAL,
  GATEWAY_RATE_LIMIT_RESET_INTERVAL,
  MAX_GATEWAY_REQUESTS_PER_INTERVAL,
  Shard,
  ShardEvents,
  ShardGatewayConfig,
  ShardHeart,
  ShardSocketCloseCodes,
  ShardSocketRequest,
  ShardState,
} from "./types.ts";
import { startHeartbeating } from "./startHeartbeating.ts";
import { stopHeartbeating } from "./stopHeartbeating.ts";
import { resume } from "./resume.ts";
import { createLeakyBucket, LeakyBucket } from "../../util/bucket.ts";
import { calculateSafeRequests } from "./calculateSafeRequests.ts";
import { send } from "./send.ts";
import { handleClose } from "./handleClose.ts";
import { connect } from "./connect.ts";
import { close } from "./close.ts";
import { shutdown } from "./shutdown.ts";
import { isOpen } from "./isOpen.ts";
import { DiscordGatewayPayload, DiscordStatusUpdate } from "../../types/discord.ts";
import { GatewayIntents, PickPartial } from "../../types/shared.ts";
import { API_VERSION } from "../../util/constants.ts";

// TODO: debug
// TODO: function overwrite
// TODO: improve shard event resolving

/** */
export function createShard(
  options: CreateShard,
) {
  // This is done for performance reasons
  const calculateSafeRequestsOverwritten = options.calculateSafeRequests ?? calculateSafeRequests;
  const closeOverwritten = options.close ?? close;
  const connectOverwritten = options.connect ?? connect;
  const identifyOverwritten = options.identify ?? identify;
  const sendOverwritten = options.send ?? send;
  const shutdownOverwritten = options.shutdown ?? shutdown;
  const resumeOverwritten = options.resume ?? resume;
  const handleCloseOverwritten = options.handleClose ?? handleClose;
  const handleMessageOverwritten = options.handleMessage ?? handleMessage;
  const isOpenOverwritten = options.isOpen ?? isOpen;
  const startHeartbeatingOverwritten = options.startHeartbeating ?? startHeartbeating;
  const stopHeartbeatingOverwritten = options.stopHeartbeating ?? stopHeartbeating;

  return {
    // ----------
    // PROPERTIES
    // ----------

    /** The gateway configuration which is used to connect to Discord. */
    gatewayConfig: {
      compress: options.gatewayConfig.compress ?? false,
      intents: options.gatewayConfig.intents ?? 0,
      properties: {
        os: options.gatewayConfig?.properties?.os ?? Deno.build.os,
        browser: options.gatewayConfig?.properties?.browser ?? "Discordeno",
        device: options.gatewayConfig?.properties?.device ?? "Discordeno",
      },
      token: options.gatewayConfig.token,
      url: options.gatewayConfig.url ?? "wss://gateway.discord.gg",
      version: options.gatewayConfig.version ?? API_VERSION,
    } as ShardGatewayConfig,
    /** This contains all the heartbeat information */
    heart: {
      acknowledged: false,
      interval: DEFAULT_HEARTBEAT_INTERVAL,
    } as ShardHeart,
    /** Id of the shard. */
    id: options.id,
    /** The maximum of requests which can be send to discord per rate limit tick.
     * Typically this value should not be changed.
     */
    maxRequestsPerRateLimitTick: MAX_GATEWAY_REQUESTS_PER_INTERVAL,
    /** The previous payload sequence number. */
    previousSequenceNumber: options.previousSequenceNumber || null,
    /** In which interval (in milliseconds) the gateway resets it's rate limit. */
    rateLimitResetInterval: GATEWAY_RATE_LIMIT_RESET_INTERVAL,
    /** Current session id of the shard if present. */
    sessionId: undefined as string | undefined,
    /** This contains the WebSocket connection to Discord, if currently connected. */
    socket: undefined as WebSocket | undefined,
    /** Current internal state of the shard. */
    state: ShardState.Offline,
    /** The total amount of shards which are used to communicate with Discord. */
    totalShards: options.totalShards,

    // ----------
    // METHODS
    // ----------

    /** The shard related event handlers. */
    events: options.events ?? {} as ShardEvents,

    /** Calculate the amount of requests which can safely be made per rate limit interval,
     * before the gateway gets disconnected due to an exceeded rate limit.
     */
    calculateSafeRequests: function () {
      return calculateSafeRequestsOverwritten(this);
    },

    /** Close the socket connection to discord if present. */
    close: function (code: number, reason: string) {
      return closeOverwritten(this, code, reason);
    },

    /** Connect the shard with the gateway and start heartbeating.
     * This will not identify the shard to the gateway.
     */
    connect: async function () {
      return await connectOverwritten(this);
    },

    /** Identify the shard to the gateway.
     * If not connected, this will also connect the shard to the gateway.
     */
    identify: async function () {
      return await identifyOverwritten(this);
    },

    /** Check whether the connection to Discord is currently open. */
    isOpen: function () {
      return isOpenOverwritten(this);
    },

    /** Function which can be overwritten in order to get the shards presence. */
    // This function allows to be async, in case the devs create the presence based on eg. database values.
    // Passing the shard's id there to make it easier for the dev to use this function.
    makePresence: options.makePresence,

    /** Attempt to resume the previous shards session with the gateway. */
    resume: async function () {
      return await resumeOverwritten(this);
    },

    /** Send a message to Discord.
     * @param {boolean} [highPriority=false] - Whether this message should be send asap.
     */
    send: async function (message: ShardSocketRequest, highPriority: boolean = false) {
      return await sendOverwritten(this, message, highPriority);
    },

    /** Shutdown the shard.
     * Forcefully disconnect the shard from Discord.
     * The shard may not attempt to reconnect with Discord.
     */
    shutdown: async function () {
      return await shutdownOverwritten(this);
    },

    /** @private Internal shard bucket.
     * Only access this if you know what you are doing.
     *
     * Bucket for handling shard request rate limits.
     */
    bucket: createLeakyBucket({
      max: MAX_GATEWAY_REQUESTS_PER_INTERVAL,
      refillInterval: GATEWAY_RATE_LIMIT_RESET_INTERVAL,
      refillAmount: MAX_GATEWAY_REQUESTS_PER_INTERVAL,
    }),

    /** @private Internal shard function.
     * Only use this function if you know what you are doing.
     *
     * Handle a gateway connection close.
     */
    handleClose: async function (close: CloseEvent) {
      return await handleCloseOverwritten(this, close);
    },

    /** @private Internal shard function.
     * Only use this function if you know what you are doing.
     *
     * Handle an incoming gateway message.
     */
    handleMessage: async function (message: MessageEvent<any>) {
      return await handleMessageOverwritten(this, message);
    },

    /** This function communicates with the management process, in order to know whether its free to identify. */
    requestIdentify: async function () {
      return await options.requestIdentify(this.id);
    },

    /** @private Internal state.
     * Only use this if you know what you are doing.
     *
     * Cache for pending gateway requests which should have been send while the gateway went offline.
     */
    offlineSendQueue: [] as ((_?: unknown) => void)[],

    /** @private Internal shard map.
     * Only use this map if you know what you are doing.
     *
     * This is used to resolve internal waiting states.
     * Mapped by SelectedEvents => ResolveFunction
     */
    resolves: new Map<"READY" | "RESUMED" | "INVALID_SESSION", (payload: DiscordGatewayPayload) => void>(),

    /** @private Internal shard function.
     * Only use this function if you know what you are doing.
     *
     * Start sending heartbeat payloads to Discord in the provided interval.
     */
    startHeartbeating: function (interval: number) {
      return startHeartbeatingOverwritten(this, interval);
    },

    /** @private Internal shard function.
     * Only use this function if you know what you are doing.
     *
     * Stop the heartbeating process with discord.
     */
    stopHeartbeating: function () {
      return stopHeartbeatingOverwritten(this);
    },
  };
}

export interface CreateShard {
  /** Id of the shard which should be created. */
  id: number;

  /** Gateway configuration for the shard. */
  gatewayConfig: PickPartial<ShardGatewayConfig, "token">;

  /** The total amount of shards which are used to communicate with Discord. */
  totalShards: number;

  /** This function communicates with the management process, in order to know whether its free to identify.
   * When this function resolves, this means that the shard is allowed to send an identify payload to discord.
   */
  requestIdentify: (shardId: number) => Promise<void>;

  /** Calculate the amount of requests which can safely be made per rate limit interval,
   * before the gateway gets disconnected due to an exceeded rate limit.
   */
  calculateSafeRequests?: typeof calculateSafeRequests;

  /** Close the socket connection to discord if present. */
  close?: typeof close;

  /** Connect the shard with the gateway and start heartbeating.
   * This will not identify the shard to the gateway.
   */
  connect?: typeof connect;

  /** @private Internal shard function.
   * Only use this function if you know what you are doing.
   *
   * Handle a gateway connection close.
   */
  handleClose?: typeof handleClose;

  /** @private Internal shard function.
   * Only use this function if you know what you are doing.
   *
   * Handle an incoming gateway message.
   */
  handleMessage?: typeof handleMessage;

  /** Identify the shard to the gateway.
   * If not connected, this will also connect the shard to the gateway.
   */
  identify?: typeof identify;

  /** Check whether the connection to Discord is currently open. */
  isOpen?: typeof isOpen;

  /** Function which can be overwritten in order to get the shards presence. */
  makePresence?(shardId: number): Promise<DiscordStatusUpdate> | DiscordStatusUpdate;

  /** The maximum of requests which can be send to discord per rate limit tick.
   * Typically this value should not be changed.
   */
  maxRequestsPerRateLimitTick?: number;

  /** The previous payload sequence number. */
  previousSequenceNumber?: number;

  /** In which interval (in milliseconds) the gateway resets it's rate limit. */
  rateLimitResetInterval?: number;

  /** Attempt to resume the previous shards session with the gateway. */
  resume?: typeof resume;

  /** Send a message to Discord.
   * @param {boolean} [highPriority=false] - Whether this message should be send asap.
   */
  send?: typeof send;

  /** Shutdown the shard.
   * Forcefully disconnect the shard from Discord.
   * The shard may not attempt to reconnect with Discord.
   */
  shutdown?: typeof shutdown;

  /** @private Internal shard function.
   * Only use this function if you know what you are doing.
   *
   * Start sending heartbeat payloads to Discord in the provided interval.
   */
  startHeartbeating?: typeof startHeartbeating;

  /** Current internal state of the shard. */
  state?: ShardState;

  /** @private Internal shard function.
   * Only use this function if you know what you are doing.
   *
   * Stop the heartbeating process with discord.
   */
  stopHeartbeating?: typeof stopHeartbeating;

  /** The shard related event handlers. */
  events?: ShardEvents;
  /** This contains all the heartbeat information */
  heart?: ShardHeart;
  /** Bucket for handling shard request rate limits. */
  bucket?: LeakyBucket;
  /** Cache for pending gateway requests which should have been send while the gateway went offline. */
  offlineSendQueue?: ShardSocketRequest[];
  /** This is used to resolve internal waiting states.
   * Mapped by SelectedEvents => ResolveFunction
   */
  resolves?: Shard["resolves"];
}