Asset holders query

src/model/asset_id.ts

@@ -0,0 +1,2 @@
+// String like USD-GBSTRUSD7IRX73RQZBL3RQUH6KS3O4NYFY3QCALDLZD77XMZOPWAVTUK
+export type AssetID = string;

src/model/balance.ts

@@ -1,6 +1,5 @@
 import { Asset } from "stellar-sdk";
-import { toFloatAmountString } from "../util/stellar";
-import { AccountID } from "./account_id";
+import { AccountID, AssetID } from "./";
 
 export interface IBalanceBase {
   account: AccountID;
@@ -15,6 +14,12 @@ export interface IBalance extends IBalanceBase {
 }
 
 export class Balance implements IBalance {
+  public static parsePagingToken(token: string): [AccountID, AssetID, string] {
+    return Buffer.from(token, "base64")
+      .toString()
+      .split("_") as [AccountID, AssetID, string];
+  }
+
   public account: AccountID;
   public asset: Asset;
   public limit: string;
@@ -24,10 +29,14 @@ export class Balance implements IBalance {
 
   constructor(data: IBalance) {
     this.account = data.account;
-    this.limit = toFloatAmountString(data.limit);
-    this.balance = toFloatAmountString(data.balance);
+    this.limit = data.limit;
+    this.balance = data.balance;
     this.lastModified = data.lastModified;
     this.authorized = data.authorized;
     this.asset = data.asset;
   }
+
+  public get paging_token() {
+    return Buffer.from(`${this.account}_${this.asset.toString()}_${this.balance}`).toString("base64");
+  }
 }

src/model/balance_values.ts

@@ -1,5 +1,4 @@
 import { Asset } from "stellar-sdk";
-import { toFloatAmountString } from "../util/stellar";
 import { IBalanceBase } from "./balance";
 
 export class BalanceValues implements IBalanceBase {
@@ -11,8 +10,8 @@ export class BalanceValues implements IBalanceBase {
 
   constructor(data: IBalanceBase) {
     this.account = data.account;
-    this.limit = toFloatAmountString(data.limit);
-    this.balance = toFloatAmountString(data.balance);
+    this.limit = data.limit;
+    this.balance = data.balance;
     this.authorized = data.authorized;
     this.asset = data.asset;
   }

src/model/index.ts

@@ -4,6 +4,7 @@ export * from "./account_thresholds";
 export * from "./account_flags";
 export * from "./account_values";
 export * from "./account_subscription_payload";
+export * from "./asset_id";
 export * from "./asset_input";
 export * from "./data_entry";
 export * from "./data_entry_subscription_payload";

src/repo/assets.ts

@@ -1,6 +1,10 @@
 import { IDatabase } from "pg-promise";
 import squel from "squel";
-import { Asset } from "stellar-base";
+import { Asset } from "stellar-sdk";
+import { PagingParams } from "../datasource/horizon/base";
+import { Balance } from "../model";
+import { BalanceFactory } from "../model/factories";
+import { parseCursorPagination, properlyOrdered, SortOrder } from "../util/paging";
 
 export default class AssetsRepo {
   private db: IDatabase<any>;
@@ -39,4 +43,31 @@ export default class AssetsRepo {
 
     return res.map(a => new Asset(a.assetcode, a.issuer));
   }
+
+  public async findHolders(asset: Asset, paging: PagingParams) {
+    const { limit, cursor, order } = parseCursorPagination(paging);
+    const queryBuilder = squel
+      .select()
+      .from("trustlines")
+      .where("assetcode = ?", asset.getCode())
+      .where("issuer = ?", asset.getIssuer())
+      .order("balance", order === SortOrder.ASC) // we must order by balance first to support cursor pagination
+      .order("accountid", order !== SortOrder.ASC) // inversion of above
+      .limit(limit);
+
+    if (cursor) {
+      const [accountId, , balance] = Balance.parsePagingToken(cursor);
+
+      if (paging.after) {
+        queryBuilder.where("(balance = ? AND accountid > ?) OR balance < ?", balance, accountId, balance);
+      } else if (paging.before) {
+        queryBuilder.where("(balance = ? AND accountid < ?) OR balance > ?", balance, accountId, balance);
+      }
+    }
+
+    const res = await this.db.manyOrNone(queryBuilder.toString());
+    const balances = res.map(r => BalanceFactory.fromDb(r));
+
+    return properlyOrdered(balances, paging);
+  }
 }

src/schema/assets.ts

@@ -14,6 +14,8 @@ export const typeDefs = gql`
     issuer: Account
     "Asset's code"
     code: AssetCode!
+    "All accounts that trust this asset, ordered by balance"
+    balances(first: Int, last: Int, after: String, before: String): BalanceConnection
   }
 
   "Represents single [asset](https://www.stellar.org/developers/guides/concepts/assets.html) on Stellar network with additional statistics, provided by Horizon"
@@ -30,6 +32,8 @@ export const typeDefs = gql`
     numAccounts: Int
     "Asset's issuer account flags"
     flags: AccountFlags
+    "All accounts that trust this asset, ordered by balance"
+    balances(first: Int, last: Int, after: String, before: String): BalanceConnection
   }
 
   "A list of assets"
@@ -50,6 +54,8 @@ export const typeDefs = gql`
   }
 
   type Query {
+    "Get single asset"
+    asset(id: AssetID): Asset
     "Get list of assets"
     assets(
       code: AssetCode

src/schema/resolvers/asset.ts

@@ -1,12 +1,25 @@
+import { Asset } from "stellar-sdk";
+import { db } from "../../database";
 import { IHorizonAssetData } from "../../datasource/types";
 import { IApolloContext } from "../../graphql_server";
+import { AssetID } from "../../model";
+import { AssetFactory } from "../../model/factories";
 import * as resolvers from "./shared";
 import { makeConnection } from "./util";
 
+const holdersResolver = async (root: Asset, args: any, ctx: IApolloContext, info: any) => {
+  const balances = await db.assets.findHolders(root, args);
+
+  return makeConnection(balances);
+};
+
 export default {
-  Asset: { issuer: resolvers.account },
-  AssetWithInfo: { issuer: resolvers.account },
+  Asset: { issuer: resolvers.account, balances: holdersResolver },
+  AssetWithInfo: { issuer: resolvers.account, balances: holdersResolver },
   Query: {
+    asset: async (root: any, args: { id: AssetID }, ctx: IApolloContext, info: any) => {
+      return AssetFactory.fromId(args.id);
+    },
     assets: async (root: any, args: any, ctx: IApolloContext, info: any) => {
       const { code, issuer } = args;
       const records: IHorizonAssetData[] = await ctx.dataSources.assets.all(

src/schema/resolvers/balance.ts

@@ -1,7 +1,8 @@
 import { withFilter } from "graphql-subscriptions";
 import { IApolloContext } from "../../graphql_server";
-import { BalanceSubscriptionPayload } from "../../model";
+import { Balance, BalanceSubscriptionPayload } from "../../model";
 import { BALANCE, pubsub } from "../../pubsub";
+import { toFloatAmountString } from "../../util/stellar";
 import * as resolvers from "./shared";
 import { eventMatches } from "./util";
 
@@ -24,15 +25,19 @@ export default {
   Balance: {
     account: resolvers.account,
     ledger: resolvers.ledger,
-    asset: resolvers.asset
+    asset: resolvers.asset,
+    limit: (root: Balance) => toFloatAmountString(root.limit),
+    balance: (root: Balance) => toFloatAmountString(root.balance)
   },
   BalanceSubscriptionPayload: {
     account: resolvers.account,
     asset: resolvers.asset
   },
   BalanceValues: {
     account: resolvers.account,
-    asset: resolvers.asset
+    asset: resolvers.asset,
+    limit: (root: Balance) => toFloatAmountString(root.limit),
+    balance: (root: Balance) => toFloatAmountString(root.balance)
   },
   Subscription: { balance: balanceSubscription(BALANCE) }
 };

src/schema/resolvers/util.ts

@@ -22,10 +22,10 @@ export function idOnlyRequested(info: any): boolean {
   return false;
 }
 
-export function makeConnection<T extends IWithPagingToken, R>(records: T[], nodeBuilder: (r: T) => R) {
+export function makeConnection<T extends IWithPagingToken, R>(records: T[], nodeBuilder?: (r: T) => R) {
   const edges = records.map(record => {
     return {
-      node: nodeBuilder(record),
+      node: nodeBuilder ? nodeBuilder(record) : record,
       cursor: record.paging_token
     };
   });

src/schema/type_defs.ts

@@ -72,6 +72,17 @@ export const typeDefs = gql`
     ledger: Ledger!
   }
 
+  type BalanceConnection {
+    pageInfo: PageInfo!
+    nodes: [Balance]
+    edges: [BalanceEdge]
+  }
+
+  type BalanceEdge {
+    cursor: String!
+    node: Balance
+  }
+
   "Represents a current [trustline](https://www.stellar.org/developers/guides/concepts/assets.html#trustlines) state, which is broadcasting to subscribers"
   type BalanceValues implements IBalance {
     account: Account

src/util/paging.ts

@@ -1,3 +1,5 @@
+import { PagingParams } from "../datasource/horizon/base";
+
 export enum SortOrder {
   DESC = "desc",
   ASC = "asc"
@@ -10,3 +12,21 @@ export function invertSortOrder(order: SortOrder) {
 
   return SortOrder.DESC;
 }
+
+export function parseCursorPagination(args: PagingParams) {
+  const { first, after, last, before, order = SortOrder.DESC } = args;
+
+  if (!first && !last) {
+    throw new Error("Missing paging parameters");
+  }
+
+  return {
+    limit: first || last,
+    order: last ? invertSortOrder(order) : order,
+    cursor: last ? before : after
+  };
+}
+
+export function properlyOrdered(records: any[], pagingParams: PagingParams): any[] {
+  return pagingParams.last ? records.reverse() : records;
+}

tests/unit/model/balance.test.ts

@@ -2,7 +2,6 @@ import { Asset } from "stellar-sdk";
 import { Balance } from "../../../src/model";
 import { BalanceFactory } from "../../../src/model/factories";
 import { MAX_INT64 } from "../../../src/util";
-import { toFloatAmountString } from "../../../src/util/stellar";
 import AccountFactory from "../../factories/account";
 
 const data = {
@@ -25,8 +24,8 @@ describe("constructor", () => {
 
   it("sets account id", () => expect(subject.account).toEqual(data.accountid));
   it("sets lastModified", () => expect(subject.lastModified).toEqual(data.lastmodified));
-  it("formats limit", () => expect(subject.limit).toEqual("922337203685.4775807"));
-  it("formats balance", () => expect(subject.balance).toEqual("960.0000000"));
+  it("sets limit", () => expect(subject.limit).toEqual("9223372036854775807"));
+  it("sets balance", () => expect(subject.balance).toEqual("9600000000"));
   it("sets authorized", () => expect(subject.authorized).toBe(true));
   it("sets asset", () => {
     expect(subject.asset).toBeInstanceOf(Asset);
@@ -42,8 +41,8 @@ describe("static buildFakeNative(account)", () => {
 
     expect(fake).toMatchObject({
       account: account.id,
-      balance: toFloatAmountString(account.balance),
-      limit: toFloatAmountString(MAX_INT64),
+      balance: account.balance,
+      limit: MAX_INT64,
       authorized: true,
       lastModified: account.lastModified
     });