import {routes, ServerApi} from "@lodestar/api";
import {ProofType, Tree} from "@chainsafe/persistent-merkle-tree";
import {ApiModules} from "../types.js";
import {resolveStateId} from "../beacon/state/utils.js";
import {IApiOptions} from "../../options.js";

export function getProofApi(
  opts: IApiOptions,
  {chain, config, db}: Pick<ApiModules, "chain" | "config" | "db">
): ServerApi<routes.proof.Api> {
  // It's currently possible to request gigantic proofs (eg: a proof of the entire beacon state)
  // We want some some sort of resistance against this DoS vector.
  const maxGindicesInProof = opts.maxGindicesInProof ?? 512;

  return {
    async getStateProof(stateId, jsonPaths) {
      const {state} = await resolveStateId(config, chain, db, stateId);

      // Commit any changes before computing the state root. In normal cases the state should have no changes here
      state.commit();
      const stateNode = state.node;
      const tree = new Tree(stateNode);

      const gindexes = state.type.tree_createProofGindexes(stateNode, jsonPaths);
      // TODO: Is it necessary to de-duplicate?
      //       It's not a problem if we overcount gindexes
      const gindicesSet = new Set(gindexes);

      if (gindicesSet.size > maxGindicesInProof) {
        throw new Error("Requested proof is too large.");
      }

      return {
        data: tree.getProof({
          type: ProofType.treeOffset,
          gindices: Array.from(gindicesSet),
        }),
      };
    },
  };
}