import {ApiClient, routes} from "@lodestar/api";
import {ValidatorIndex} from "@lodestar/types";
import {Logger, MapDef, toPubkeyHex} from "@lodestar/utils";
import {Metrics} from "../metrics.js";
import {batchItems} from "../util/index.js";

/**
 * This is to prevent the "Request body is too large" issue for http post.
 * Typical servers accept up to 1MB (2 ** 20 bytes) of request body, for example fastify and nginx.
 * A hex encoded public key with "0x"-prefix has a size of 98 bytes + 2 bytes to account for commas
 * and other JSON padding. `Math.floor(2 ** 20 / 100) == 10485`, we can send up to ~10k keys per request.
 */
const PUBKEYS_PER_REQUEST = 10_000;

// To assist with readability
type PubkeyHex = string;

// To assist with logging statuses, we only log the statuses that are not active_exiting or withdrawal_possible
type SimpleValidatorStatus = "pending" | "active" | "exited" | "withdrawn";

const statusToSimpleStatusMapping = (status: routes.beacon.ValidatorStatus): SimpleValidatorStatus => {
  switch (status) {
    case "active_exiting":
    case "active_slashed":
    case "active_ongoing":
      return "active";

    case "withdrawal_possible":
    case "exited_slashed":
    case "exited_unslashed":
      return "exited";

    case "pending_initialized":
    case "pending_queued":
      return "pending";

    case "withdrawal_done":
      return "withdrawn";
  }
};

export class IndicesService {
  readonly index2pubkey = new Map<ValidatorIndex, PubkeyHex>();
  /** Indexed by pubkey in hex 0x prefixed */
  readonly pubkey2index = new Map<PubkeyHex, ValidatorIndex>();
  // Request indices once
  private pollValidatorIndicesPromise: Promise<ValidatorIndex[]> | null = null;

  constructor(
    private readonly logger: Logger,
    private readonly api: ApiClient,
    private readonly metrics: Metrics | null
  ) {
    if (metrics) {
      metrics.indices.addCollect(() => metrics.indices.set(this.index2pubkey.size));
    }
  }

  get indexCount(): number {
    return this.index2pubkey.size;
  }

  /** Returns the validator index for a given validator pubkey */
  getValidatorIndex(pubKey: PubkeyHex): ValidatorIndex | undefined {
    return this.pubkey2index.get(pubKey);
  }

  /** Return all known indices from the validatorStore pubkeys */
  getAllLocalIndices(): ValidatorIndex[] {
    return Array.from(this.index2pubkey.keys());
  }

  /** Return true if `index` is active part of this validator client */
  hasValidatorIndex(index: ValidatorIndex): boolean {
    return this.index2pubkey.has(index);
  }

  async pollValidatorIndices(pubkeysHex: PubkeyHex[]): Promise<ValidatorIndex[]> {
    // Ensures pollValidatorIndicesInternal() is not called more than once at the same time.
    // AttestationDutiesService, SyncCommitteeDutiesService and DoppelgangerService will call this function at the same time, so this will
    // cache the promise and return it to the second caller, preventing calling the API twice for the same data.
    if (this.pollValidatorIndicesPromise) {
      return this.pollValidatorIndicesPromise;
    }

    this.pollValidatorIndicesPromise = this.pollValidatorIndicesInternal(pubkeysHex).finally(() => {
      // Once the pollValidatorIndicesInternal() resolves or rejects null the cached promise so it can be called again.
      this.pollValidatorIndicesPromise = null;
    });
    return this.pollValidatorIndicesPromise;
  }

  removeForKey(pubkey: PubkeyHex): boolean {
    for (const [index, value] of this.index2pubkey) {
      if (value === pubkey) {
        this.index2pubkey.delete(index);
      }
    }
    return this.pubkey2index.delete(pubkey);
  }

  /** Iterate through all the voting pubkeys in the `ValidatorStore` and attempt to learn any unknown
      validator indices. Returns the new discovered indexes */
  private async pollValidatorIndicesInternal(pubkeysHex: PubkeyHex[]): Promise<ValidatorIndex[]> {
    const pubkeysHexToDiscover = pubkeysHex.filter((pubkey) => !this.pubkey2index.has(pubkey));

    if (pubkeysHexToDiscover.length === 0) {
      return [];
    }

    // Query the remote BN to resolve a pubkey to a validator index.
    // support up to 10k pubkeys per poll
    const pubkeysHexBatches = batchItems(pubkeysHexToDiscover, {batchSize: PUBKEYS_PER_REQUEST});

    const newIndices: number[] = [];
    for (const pubkeysHexBatch of pubkeysHexBatches) {
      const validatorIndicesArr = await this.fetchValidatorIndices(pubkeysHexBatch);
      newIndices.push(...validatorIndicesArr);
    }

    this.metrics?.discoveredIndices.inc(newIndices.length);

    return newIndices;
  }

  private async fetchValidatorIndices(pubkeysHex: string[]): Promise<ValidatorIndex[]> {
    const validators = (await this.api.beacon.postStateValidators({stateId: "head", validatorIds: pubkeysHex})).value();

    const newIndices = [];

    const allValidatorStatuses = new MapDef<SimpleValidatorStatus, number>(() => 0);

    for (const validator of validators) {
      // Group all validators by status
      const status = statusToSimpleStatusMapping(validator.status);
      allValidatorStatuses.set(status, allValidatorStatuses.getOrDefault(status) + 1);

      const pubkeyHex = toPubkeyHex(validator.validator.pubkey);
      if (!this.pubkey2index.has(pubkeyHex)) {
        this.logger.info("Validator seen on beacon chain", {
          validatorIndex: validator.index,
          pubKey: pubkeyHex,
        });
        this.pubkey2index.set(pubkeyHex, validator.index);
        this.index2pubkey.set(validator.index, pubkeyHex);
        newIndices.push(validator.index);
      }
    }

    // The number of validators that are not in the beacon chain
    const pendingCount = pubkeysHex.length - validators.length;

    allValidatorStatuses.set("pending", allValidatorStatuses.getOrDefault("pending") + pendingCount);

    // Retrieve the number of validators for each status
    const statuses = Object.fromEntries(Array.from(allValidatorStatuses.entries()).filter((entry) => entry[1] > 0));

    // The total number of validators
    const total = pubkeysHex.length;

    this.logger.info("Validator statuses", {...statuses, total});

    return newIndices;
  }
}