/*
 This file is part of GNU Taler
 (C) 2024 Taler Systems SA

 GNU Taler is free software; you can redistribute it and/or modify it under the
 terms of the GNU General Public License as published by the Free Software
 Foundation; either version 3, or (at your option) any later version.

 GNU Taler is distributed in the hope that it will be useful, but WITHOUT ANY
 WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
 A PARTICULAR PURPOSE.  See the GNU General Public License for more details.

 You should have received a copy of the GNU General Public License along with
 GNU Taler; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
 */

/**
 * Imports.
 */
import { GlobalIDB } from "@gnu-taler/idb-bridge";
import {
  AbsoluteTime,
  AsyncCondition,
  CancellationToken,
  Duration,
  Logger,
  NotificationType,
  ObservabilityContext,
  ObservabilityEventType,
  TalerErrorDetail,
  TaskThrottler,
  TransactionIdStr,
  TransactionState,
  TransactionType,
  WalletNotification,
  assertUnreachable,
  getErrorDetailFromException,
  j2s,
  safeStringifyException,
} from "@gnu-taler/taler-util";
import { processBackupForProvider } from "./backup/index.js";
import {
  DbRetryInfo,
  PendingTaskType,
  TaskIdStr,
  TaskRunResult,
  TaskRunResultType,
  constructTaskIdentifier,
  getExchangeState,
  parseTaskIdentifier,
} from "./common.js";
import {
  OPERATION_STATUS_ACTIVE_FIRST,
  OPERATION_STATUS_ACTIVE_LAST,
  OperationRetryRecord,
  WalletDbAllStoresReadOnlyTransaction,
  WalletDbReadOnlyTransaction,
  timestampAbsoluteFromDb,
} from "./db.js";
import {
  computeDepositTransactionStatus,
  processDepositGroup,
} from "./deposits.js";
import {
  computeDenomLossTransactionStatus,
  updateExchangeFromUrlHandler,
} from "./exchanges.js";
import {
  computePayMerchantTransactionState,
  computeRefundTransactionState,
  processPurchase,
} from "./pay-merchant.js";
import {
  computePeerPullCreditTransactionState,
  processPeerPullCredit,
} from "./pay-peer-pull-credit.js";
import {
  computePeerPullDebitTransactionState,
  processPeerPullDebit,
} from "./pay-peer-pull-debit.js";
import {
  computePeerPushCreditTransactionState,
  processPeerPushCredit,
} from "./pay-peer-push-credit.js";
import {
  computePeerPushDebitTransactionState,
  processPeerPushDebit,
} from "./pay-peer-push-debit.js";
import { processRecoupGroup } from "./recoup.js";
import {
  computeRefreshTransactionState,
  processRefreshGroup,
} from "./refresh.js";
import {
  constructTransactionIdentifier,
  parseTransactionIdentifier,
} from "./transactions.js";
import {
  InternalWalletState,
  WalletExecutionContext,
  getNormalWalletExecutionContext,
  getObservedWalletExecutionContext,
} from "./wallet.js";
import {
  computeWithdrawalTransactionStatus,
  processWithdrawalGroup,
} from "./withdraw.js";

const logger = new Logger("shepherd.ts");

/**
 * Info about one task being shepherded.
 */
interface ShepherdInfo {
  cts: CancellationToken.Source;
}

/**
 * Check if a task is alive, i.e. whether it prevents
 * the main task loop from exiting.
 */
function taskGivesLiveness(taskId: string): boolean {
  const parsedTaskId = parseTaskIdentifier(taskId);
  switch (parsedTaskId.tag) {
    case PendingTaskType.Backup:
    case PendingTaskType.ExchangeUpdate:
      return false;
    case PendingTaskType.Deposit:
    case PendingTaskType.PeerPullCredit:
    case PendingTaskType.PeerPullDebit:
    case PendingTaskType.PeerPushCredit:
    case PendingTaskType.Refresh:
    case PendingTaskType.Recoup:
    case PendingTaskType.RewardPickup:
    case PendingTaskType.Withdraw:
    case PendingTaskType.PeerPushDebit:
    case PendingTaskType.Purchase:
      return true;
    default:
      assertUnreachable(parsedTaskId);
  }
}

export interface TaskScheduler {
  ensureRunning(): Promise<void>;
  startShepherdTask(taskId: TaskIdStr): void;
  stopShepherdTask(taskId: TaskIdStr): void;
  resetTaskRetries(taskId: TaskIdStr): Promise<void>;
  reload(): Promise<void>;
  getActiveTasks(): TaskIdStr[];
  isIdle(): boolean;
  shutdown(): Promise<void>;
}

export class TaskSchedulerImpl implements TaskScheduler {
  private sheps: Map<TaskIdStr, ShepherdInfo> = new Map();

  private iterCond = new AsyncCondition();

  private throttler = new TaskThrottler();

  isRunning: boolean = false;

  constructor(private ws: InternalWalletState) {}

  private async loadTasksFromDb(): Promise<void> {
    const activeTasks = await getActiveTaskIds(this.ws);

    logger.info(`active tasks from DB: ${j2s(activeTasks)}`);

    for (const tid of activeTasks.taskIds) {
      this.startShepherdTask(tid);
    }
  }

  getActiveTasks(): TaskIdStr[] {
    return [...this.sheps.keys()];
  }

  async shutdown(): Promise<void> {
    const tasksIds = [...this.sheps.keys()];
    logger.info(`Stopping task shepherd.`);
    for (const taskId of tasksIds) {
      this.stopShepherdTask(taskId);
    }
  }

  async ensureRunning(): Promise<void> {
    if (this.isRunning) {
      return;
    }
    this.isRunning = true;
    try {
      await this.loadTasksFromDb();
    } catch (e) {
      this.isRunning = false;
      throw e;
    }
    this.run()
      .catch((e) => {
        logger.error("error running task loop");
        logger.error(`err: ${e}`);
      })
      .then(() => {
        logger.trace("done running task loop");
        this.isRunning = false;
      });
  }

  isIdle(): boolean {
    let alive = false;
    const taskIds = [...this.sheps.keys()];
    for (const taskId of taskIds) {
      if (taskGivesLiveness(taskId)) {
        alive = true;
        break;
      }
    }
    // We're idle if no task is alive anymore.
    return !alive;
  }

  private async run(): Promise<void> {
    logger.trace("Running task loop.");
    logger.trace(`sheps: ${this.sheps.size}`);
    while (true) {
      if (this.ws.stopped) {
        logger.trace("Breaking out of task loop (wallet stopped).");
        break;
      }

      if (this.isIdle()) {
        this.ws.notify({
          type: NotificationType.Idle,
        });
      }

      await this.iterCond.wait();
    }
    logger.trace("Done with task loop.");
  }

  startShepherdTask(taskId: TaskIdStr): void {
    this.ensureRunning().catch((e) => {
      logger.error(`error running scheduler: ${safeStringifyException(e)}`);
    });
    // Run in the background, no await!
    this.internalStartShepherdTask(taskId);
  }

  /**
   * Stop and re-load all existing tasks.
   *
   * Mostly useful to interrupt all waits when time-travelling.
   */
  async reload(): Promise<void> {
    await this.ensureRunning();
    const tasksIds = [...this.sheps.keys()];
    logger.info(`reloading sheperd with ${tasksIds.length} tasks`);
    for (const taskId of tasksIds) {
      this.stopShepherdTask(taskId);
    }
    for (const taskId of tasksIds) {
      this.startShepherdTask(taskId);
    }
  }

  private async internalStartShepherdTask(taskId: TaskIdStr): Promise<void> {
    logger.trace(`Starting to shepherd task ${taskId}`);
    const oldShep = this.sheps.get(taskId);
    if (oldShep) {
      logger.trace(`Already have a shepherd for ${taskId}`);
      return;
    }
    logger.trace(`Creating new shepherd for ${taskId}`);
    const newShep: ShepherdInfo = {
      cts: CancellationToken.create(),
    };
    this.sheps.set(taskId, newShep);
    try {
      await this.internalShepherdTask(taskId, newShep);
    } finally {
      logger.trace(`Done shepherding ${taskId}`);
      this.sheps.delete(taskId);
      this.iterCond.trigger();
    }
  }

  stopShepherdTask(taskId: TaskIdStr): void {
    logger.trace(`Stopping shepherding of ${taskId}`);
    const oldShep = this.sheps.get(taskId);
    if (oldShep) {
      logger.trace(`Cancelling old shepherd for ${taskId}`);
      oldShep.cts.cancel();
      this.sheps.delete(taskId);
      this.iterCond.trigger();
    }
  }

  restartShepherdTask(taskId: TaskIdStr): void {
    this.stopShepherdTask(taskId);
    this.startShepherdTask(taskId);
  }

  async resetTaskRetries(taskId: TaskIdStr): Promise<void> {
    const maybeNotification = await this.ws.db.runAllStoresReadWriteTx(
      {},
      async (tx) => {
        await tx.operationRetries.delete(taskId);
        return taskToRetryNotification(this.ws, tx, taskId, undefined);
      },
    );
    this.stopShepherdTask(taskId);
    if (maybeNotification) {
      this.ws.notify(maybeNotification);
    }
    this.startShepherdTask(taskId);
  }

  private async wait(
    taskId: TaskIdStr,
    info: ShepherdInfo,
    delay: Duration,
  ): Promise<void> {
    try {
      await info.cts.token.racePromise(this.ws.timerGroup.resolveAfter(delay));
    } catch (e) {
      logger.info(`waiting for ${taskId} interrupted`);
    }
  }

  private async internalShepherdTask(
    taskId: TaskIdStr,
    info: ShepherdInfo,
  ): Promise<void> {
    while (true) {
      if (this.ws.stopped) {
        logger.trace(`Shepherd for ${taskId} stopping as wallet is stopped`);
        return;
      }
      if (info.cts.token.isCancelled) {
        logger.trace(`Shepherd for ${taskId} got cancelled`);
        return;
      }
      const isThrottled = this.throttler.applyThrottle(taskId);
      if (isThrottled) {
        logger.warn(
          `task ${taskId} throttled, this is very likely a bug in wallet-core, please report`,
        );
        logger.warn("waiting for 60 seconds");
        await this.ws.timerGroup.resolveAfter(
          Duration.fromSpec({ seconds: 60 }),
        );
      }
      const wex = getWalletExecutionContextForTask(
        this.ws,
        taskId,
        info.cts.token,
      );
      const startTime = AbsoluteTime.now();
      logger.trace(`Shepherd for ${taskId} will call handler`);
      let res: TaskRunResult;
      try {
        res = await callOperationHandlerForTaskId(wex, taskId);
      } catch (e) {
        res = {
          type: TaskRunResultType.Error,
          errorDetail: getErrorDetailFromException(e),
        };
      }
      if (info.cts.token.isCancelled) {
        logger.trace("task cancelled, not processing result");
        return;
      }
      if (this.ws.stopped) {
        logger.trace("wallet stopped, not processing result");
        return;
      }
      wex.oc.observe({
        type: ObservabilityEventType.ShepherdTaskResult,
        resultType: res.type,
      });
      switch (res.type) {
        case TaskRunResultType.Error: {
          logger.trace(`Shepherd for ${taskId} got error result.`);
          const retryRecord = await storePendingTaskError(
            this.ws,
            taskId,
            res.errorDetail,
          );
          const t = timestampAbsoluteFromDb(retryRecord.retryInfo.nextRetry);
          const delay = AbsoluteTime.remaining(t);
          logger.trace(`Waiting for ${delay.d_ms} ms`);
          await this.wait(taskId, info, delay);
          break;
        }
        case TaskRunResultType.Backoff: {
          logger.trace(`Shepherd for ${taskId} got backoff result.`);
          const retryRecord = await storePendingTaskPending(this.ws, taskId);
          const t = timestampAbsoluteFromDb(retryRecord.retryInfo.nextRetry);
          const delay = AbsoluteTime.remaining(t);
          logger.trace(`Waiting for ${delay.d_ms} ms`);
          await this.wait(taskId, info, delay);
          break;
        }
        case TaskRunResultType.Progress: {
          logger.trace(
            `Shepherd for ${taskId} got progress result, re-running immediately.`,
          );
          await storeTaskProgress(this.ws, taskId);
          break;
        }
        case TaskRunResultType.ScheduleLater: {
          logger.trace(`Shepherd for ${taskId} got schedule-later result.`);
          await storeTaskProgress(this.ws, taskId);
          const delay = AbsoluteTime.remaining(res.runAt);
          logger.trace(`Waiting for ${delay.d_ms} ms`);
          await this.wait(taskId, info, delay);
          break;
        }
        case TaskRunResultType.Finished:
          logger.trace(`Shepherd for ${taskId} got finished result.`);
          await storePendingTaskFinished(this.ws, taskId);
          return;
        case TaskRunResultType.LongpollReturnedPending: {
          await storeTaskProgress(this.ws, taskId);
          // Make sure that we are waiting a bit if long-polling returned too early.
          const endTime = AbsoluteTime.now();
          const taskDuration = AbsoluteTime.difference(endTime, startTime);
          if (
            Duration.cmp(taskDuration, Duration.fromSpec({ seconds: 20 })) < 0
          ) {
            logger.info(
              `long-poller for ${taskId} returned unexpectedly early (${taskDuration.d_ms} ms), waiting 10 seconds`,
            );
            await this.wait(taskId, info, Duration.fromSpec({ seconds: 10 }));
          } else {
            logger.info(`task ${taskId} will long-poll again`);
          }
          break;
        }
        default:
          assertUnreachable(res);
      }
    }
  }
}

async function storePendingTaskError(
  ws: InternalWalletState,
  pendingTaskId: string,
  e: TalerErrorDetail,
): Promise<OperationRetryRecord> {
  logger.info(`storing pending task error for ${pendingTaskId}`);
  const res = await ws.db.runAllStoresReadWriteTx({}, async (tx) => {
    let retryRecord = await tx.operationRetries.get(pendingTaskId);
    if (!retryRecord) {
      retryRecord = {
        id: pendingTaskId,
        lastError: e,
        retryInfo: DbRetryInfo.reset(),
      };
    } else {
      retryRecord.lastError = e;
      retryRecord.retryInfo = DbRetryInfo.increment(retryRecord.retryInfo);
    }
    await tx.operationRetries.put(retryRecord);
    return {
      notification: await taskToRetryNotification(ws, tx, pendingTaskId, e),
      retryRecord,
    };
  });
  if (res?.notification) {
    ws.notify(res.notification);
  }
  return res.retryRecord;
}

/**
 * Task made progress, clear error.
 */
async function storeTaskProgress(
  ws: InternalWalletState,
  pendingTaskId: string,
): Promise<void> {
  await ws.db.runReadWriteTx(
    { storeNames: ["operationRetries"] },
    async (tx) => {
      await tx.operationRetries.delete(pendingTaskId);
    },
  );
}

async function storePendingTaskPending(
  ws: InternalWalletState,
  pendingTaskId: string,
): Promise<OperationRetryRecord> {
  const res = await ws.db.runAllStoresReadWriteTx({}, async (tx) => {
    let retryRecord = await tx.operationRetries.get(pendingTaskId);
    let hadError = false;
    if (!retryRecord) {
      retryRecord = {
        id: pendingTaskId,
        retryInfo: DbRetryInfo.reset(),
      };
    } else {
      if (retryRecord.lastError) {
        hadError = true;
      }
      delete retryRecord.lastError;
      retryRecord.retryInfo = DbRetryInfo.increment(retryRecord.retryInfo);
    }
    await tx.operationRetries.put(retryRecord);
    let notification: WalletNotification | undefined = undefined;
    if (hadError) {
      notification = await taskToRetryNotification(
        ws,
        tx,
        pendingTaskId,
        undefined,
      );
    }
    return {
      notification,
      retryRecord,
    };
  });
  if (res.notification) {
    ws.notify(res.notification);
  }
  return res.retryRecord;
}

async function storePendingTaskFinished(
  ws: InternalWalletState,
  pendingTaskId: string,
): Promise<void> {
  await ws.db.runReadWriteTx(
    { storeNames: ["operationRetries"] },
    async (tx) => {
      await tx.operationRetries.delete(pendingTaskId);
    },
  );
}

function getWalletExecutionContextForTask(
  ws: InternalWalletState,
  taskId: TaskIdStr,
  cancellationToken: CancellationToken,
): WalletExecutionContext {
  let oc: ObservabilityContext;
  let wex: WalletExecutionContext;

  if (ws.config.testing.emitObservabilityEvents) {
    oc = {
      observe(evt) {
        if (ws.config.testing.emitObservabilityEvents) {
          ws.notify({
            type: NotificationType.TaskObservabilityEvent,
            taskId,
            event: evt,
          });
        }
      },
    };

    wex = getObservedWalletExecutionContext(ws, cancellationToken, oc);
  } else {
    oc = {
      observe(evt) {},
    };
    wex = getNormalWalletExecutionContext(ws, cancellationToken, oc);
  }
  return wex;
}

async function callOperationHandlerForTaskId(
  wex: WalletExecutionContext,
  taskId: TaskIdStr,
): Promise<TaskRunResult> {
  const pending = parseTaskIdentifier(taskId);
  switch (pending.tag) {
    case PendingTaskType.ExchangeUpdate:
      return await updateExchangeFromUrlHandler(wex, pending.exchangeBaseUrl);
    case PendingTaskType.Refresh:
      return await processRefreshGroup(wex, pending.refreshGroupId);
    case PendingTaskType.Withdraw:
      return await processWithdrawalGroup(wex, pending.withdrawalGroupId);
    case PendingTaskType.Purchase:
      return await processPurchase(wex, pending.proposalId);
    case PendingTaskType.Recoup:
      return await processRecoupGroup(wex, pending.recoupGroupId);
    case PendingTaskType.Deposit:
      return await processDepositGroup(wex, pending.depositGroupId);
    case PendingTaskType.Backup:
      return await processBackupForProvider(wex, pending.backupProviderBaseUrl);
    case PendingTaskType.PeerPushDebit:
      return await processPeerPushDebit(wex, pending.pursePub);
    case PendingTaskType.PeerPullCredit:
      return await processPeerPullCredit(wex, pending.pursePub);
    case PendingTaskType.PeerPullDebit:
      return await processPeerPullDebit(wex, pending.peerPullDebitId);
    case PendingTaskType.PeerPushCredit:
      return await processPeerPushCredit(wex, pending.peerPushCreditId);
    case PendingTaskType.RewardPickup:
      throw Error("not supported anymore");
    default:
      return assertUnreachable(pending);
  }
  throw Error(`not reached ${pending.tag}`);
}

/**
 * Generate an appropriate error transition notification
 * for applicable tasks.
 *
 * Namely, transition notifications are generated for:
 * - exchange update errors
 * - transactions
 */
async function taskToRetryNotification(
  ws: InternalWalletState,
  tx: WalletDbAllStoresReadOnlyTransaction,
  pendingTaskId: string,
  e: TalerErrorDetail | undefined,
): Promise<WalletNotification | undefined> {
  const parsedTaskId = parseTaskIdentifier(pendingTaskId);

  switch (parsedTaskId.tag) {
    case PendingTaskType.ExchangeUpdate:
      return makeExchangeRetryNotification(ws, tx, pendingTaskId, e);
    case PendingTaskType.PeerPullCredit:
    case PendingTaskType.PeerPullDebit:
    case PendingTaskType.Withdraw:
    case PendingTaskType.PeerPushCredit:
    case PendingTaskType.Deposit:
    case PendingTaskType.Refresh:
    case PendingTaskType.RewardPickup:
    case PendingTaskType.PeerPushDebit:
    case PendingTaskType.Purchase:
      return makeTransactionRetryNotification(ws, tx, pendingTaskId, e);
    case PendingTaskType.Backup:
    case PendingTaskType.Recoup:
      return undefined;
  }
}

async function getTransactionState(
  ws: InternalWalletState,
  tx: WalletDbReadOnlyTransaction<
    [
      "depositGroups",
      "withdrawalGroups",
      "purchases",
      "refundGroups",
      "peerPullCredit",
      "peerPullDebit",
      "peerPushDebit",
      "peerPushCredit",
      "rewards",
      "refreshGroups",
      "denomLossEvents",
    ]
  >,
  transactionId: string,
): Promise<TransactionState | undefined> {
  const parsedTxId = parseTransactionIdentifier(transactionId);
  if (!parsedTxId) {
    throw Error("invalid tx identifier");
  }
  switch (parsedTxId.tag) {
    case TransactionType.Deposit: {
      const rec = await tx.depositGroups.get(parsedTxId.depositGroupId);
      if (!rec) {
        return undefined;
      }
      return computeDepositTransactionStatus(rec);
    }
    case TransactionType.InternalWithdrawal:
    case TransactionType.Withdrawal: {
      const rec = await tx.withdrawalGroups.get(parsedTxId.withdrawalGroupId);
      if (!rec) {
        return undefined;
      }
      return computeWithdrawalTransactionStatus(rec);
    }
    case TransactionType.Payment: {
      const rec = await tx.purchases.get(parsedTxId.proposalId);
      if (!rec) {
        return;
      }
      return computePayMerchantTransactionState(rec);
    }
    case TransactionType.Refund: {
      const rec = await tx.refundGroups.get(parsedTxId.refundGroupId);
      if (!rec) {
        return undefined;
      }
      return computeRefundTransactionState(rec);
    }
    case TransactionType.PeerPullCredit: {
      const rec = await tx.peerPullCredit.get(parsedTxId.pursePub);
      if (!rec) {
        return undefined;
      }
      return computePeerPullCreditTransactionState(rec);
    }
    case TransactionType.PeerPullDebit: {
      const rec = await tx.peerPullDebit.get(parsedTxId.peerPullDebitId);
      if (!rec) {
        return undefined;
      }
      return computePeerPullDebitTransactionState(rec);
    }
    case TransactionType.PeerPushCredit: {
      const rec = await tx.peerPushCredit.get(parsedTxId.peerPushCreditId);
      if (!rec) {
        return undefined;
      }
      return computePeerPushCreditTransactionState(rec);
    }
    case TransactionType.PeerPushDebit: {
      const rec = await tx.peerPushDebit.get(parsedTxId.pursePub);
      if (!rec) {
        return undefined;
      }
      return computePeerPushDebitTransactionState(rec);
    }
    case TransactionType.Refresh: {
      const rec = await tx.refreshGroups.get(parsedTxId.refreshGroupId);
      if (!rec) {
        return undefined;
      }
      return computeRefreshTransactionState(rec);
    }
    case TransactionType.Recoup:
      throw Error("not yet supported");
    case TransactionType.DenomLoss: {
      const rec = await tx.denomLossEvents.get(parsedTxId.denomLossEventId);
      if (!rec) {
        return undefined;
      }
      return computeDenomLossTransactionStatus(rec);
    }
    default:
      assertUnreachable(parsedTxId);
  }
}

async function makeTransactionRetryNotification(
  ws: InternalWalletState,
  tx: WalletDbAllStoresReadOnlyTransaction,
  pendingTaskId: string,
  e: TalerErrorDetail | undefined,
): Promise<WalletNotification | undefined> {
  const txId = convertTaskToTransactionId(pendingTaskId);
  if (!txId) {
    return undefined;
  }
  const txState = await getTransactionState(ws, tx, txId);
  if (!txState) {
    return undefined;
  }
  const notif: WalletNotification = {
    type: NotificationType.TransactionStateTransition,
    transactionId: txId,
    oldTxState: txState,
    newTxState: txState,
  };
  if (e) {
    notif.errorInfo = {
      code: e.code as number,
      hint: e.hint,
    };
  }
  return notif;
}

async function makeExchangeRetryNotification(
  ws: InternalWalletState,
  tx: WalletDbAllStoresReadOnlyTransaction,
  pendingTaskId: string,
  e: TalerErrorDetail | undefined,
): Promise<WalletNotification | undefined> {
  logger.info("making exchange retry notification");
  const parsedTaskId = parseTaskIdentifier(pendingTaskId);
  if (parsedTaskId.tag !== PendingTaskType.ExchangeUpdate) {
    throw Error("invalid task identifier");
  }
  const rec = await tx.exchanges.get(parsedTaskId.exchangeBaseUrl);

  if (!rec) {
    logger.info(`exchange ${parsedTaskId.exchangeBaseUrl} not found`);
    return undefined;
  }

  const notif: WalletNotification = {
    type: NotificationType.ExchangeStateTransition,
    exchangeBaseUrl: parsedTaskId.exchangeBaseUrl,
    oldExchangeState: getExchangeState(rec),
    newExchangeState: getExchangeState(rec),
  };
  if (e) {
    notif.errorInfo = {
      code: e.code as number,
      hint: e.hint,
    };
  }
  return notif;
}

export function listTaskForTransactionId(transactionId: string): TaskIdStr[] {
  const tid = parseTransactionIdentifier(transactionId);
  if (!tid) {
    throw Error("invalid task ID");
  }
  switch (tid.tag) {
    case TransactionType.Deposit:
      return [
        constructTaskIdentifier({
          tag: PendingTaskType.Deposit,
          depositGroupId: tid.depositGroupId,
        }),
      ];
    case TransactionType.InternalWithdrawal:
      return [
        constructTaskIdentifier({
          tag: PendingTaskType.Withdraw,
          withdrawalGroupId: tid.withdrawalGroupId,
        }),
      ];
    case TransactionType.Payment:
      return [
        constructTaskIdentifier({
          tag: PendingTaskType.Purchase,
          proposalId: tid.proposalId,
        }),
      ];
    case TransactionType.PeerPullCredit:
      return [
        constructTaskIdentifier({
          tag: PendingTaskType.PeerPullCredit,
          pursePub: tid.pursePub,
        }),
      ];
    case TransactionType.PeerPullDebit:
      return [
        constructTaskIdentifier({
          tag: PendingTaskType.PeerPullDebit,
          peerPullDebitId: tid.peerPullDebitId,
        }),
      ];
    case TransactionType.PeerPushCredit:
      return [
        constructTaskIdentifier({
          tag: PendingTaskType.PeerPullCredit,
          pursePub: tid.peerPushCreditId,
        }),
      ];
    case TransactionType.PeerPushDebit:
      return [
        constructTaskIdentifier({
          tag: PendingTaskType.PeerPullCredit,
          pursePub: tid.pursePub,
        }),
      ];
    case TransactionType.Recoup:
      return [
        constructTaskIdentifier({
          tag: PendingTaskType.Recoup,
          recoupGroupId: tid.recoupGroupId,
        }),
      ];
    case TransactionType.Refresh:
      return [
        constructTaskIdentifier({
          tag: PendingTaskType.Refresh,
          refreshGroupId: tid.refreshGroupId,
        }),
      ];
    case TransactionType.Refund:
      return [];
    case TransactionType.Withdrawal:
      return [
        constructTaskIdentifier({
          tag: PendingTaskType.Withdraw,
          withdrawalGroupId: tid.withdrawalGroupId,
        }),
      ];
    case TransactionType.DenomLoss:
      return [];
    default:
      assertUnreachable(tid);
  }
}

/**
 * Convert the task ID for a task that processes a transaction int
 * the ID for the transaction.
 */
export function convertTaskToTransactionId(
  taskId: string,
): TransactionIdStr | undefined {
  const parsedTaskId = parseTaskIdentifier(taskId);
  switch (parsedTaskId.tag) {
    case PendingTaskType.PeerPullCredit:
      return constructTransactionIdentifier({
        tag: TransactionType.PeerPullCredit,
        pursePub: parsedTaskId.pursePub,
      });
    case PendingTaskType.PeerPullDebit:
      return constructTransactionIdentifier({
        tag: TransactionType.PeerPullDebit,
        peerPullDebitId: parsedTaskId.peerPullDebitId,
      });
    // FIXME: This doesn't distinguish internal-withdrawal.
    // Maybe we should have a different task type for that as well?
    // Or maybe transaction IDs should be valid task identifiers?
    case PendingTaskType.Withdraw:
      return constructTransactionIdentifier({
        tag: TransactionType.Withdrawal,
        withdrawalGroupId: parsedTaskId.withdrawalGroupId,
      });
    case PendingTaskType.PeerPushCredit:
      return constructTransactionIdentifier({
        tag: TransactionType.PeerPushCredit,
        peerPushCreditId: parsedTaskId.peerPushCreditId,
      });
    case PendingTaskType.Deposit:
      return constructTransactionIdentifier({
        tag: TransactionType.Deposit,
        depositGroupId: parsedTaskId.depositGroupId,
      });
    case PendingTaskType.Refresh:
      return constructTransactionIdentifier({
        tag: TransactionType.Refresh,
        refreshGroupId: parsedTaskId.refreshGroupId,
      });
    case PendingTaskType.PeerPushDebit:
      return constructTransactionIdentifier({
        tag: TransactionType.PeerPushDebit,
        pursePub: parsedTaskId.pursePub,
      });
    case PendingTaskType.Purchase:
      return constructTransactionIdentifier({
        tag: TransactionType.Payment,
        proposalId: parsedTaskId.proposalId,
      });
    default:
      return undefined;
  }
}

export interface ActiveTaskIdsResult {
  taskIds: TaskIdStr[];
}

export async function getActiveTaskIds(
  ws: InternalWalletState,
): Promise<ActiveTaskIdsResult> {
  const res: ActiveTaskIdsResult = {
    taskIds: [],
  };
  await ws.db.runReadWriteTx(
    {
      storeNames: [
        "exchanges",
        "refreshGroups",
        "withdrawalGroups",
        "purchases",
        "depositGroups",
        "recoupGroups",
        "peerPullCredit",
        "peerPushDebit",
        "peerPullDebit",
        "peerPushCredit",
      ],
    },
    async (tx) => {
      const active = GlobalIDB.KeyRange.bound(
        OPERATION_STATUS_ACTIVE_FIRST,
        OPERATION_STATUS_ACTIVE_LAST,
      );

      // Withdrawals

      {
        const activeRecs =
          await tx.withdrawalGroups.indexes.byStatus.getAll(active);
        for (const rec of activeRecs) {
          const taskId = constructTaskIdentifier({
            tag: PendingTaskType.Withdraw,
            withdrawalGroupId: rec.withdrawalGroupId,
          });
          res.taskIds.push(taskId);
        }
      }

      // Deposits

      {
        const activeRecs =
          await tx.depositGroups.indexes.byStatus.getAll(active);
        for (const rec of activeRecs) {
          const taskId = constructTaskIdentifier({
            tag: PendingTaskType.Deposit,
            depositGroupId: rec.depositGroupId,
          });
          res.taskIds.push(taskId);
        }
      }

      // Refreshes

      {
        const activeRecs =
          await tx.refreshGroups.indexes.byStatus.getAll(active);
        for (const rec of activeRecs) {
          const taskId = constructTaskIdentifier({
            tag: PendingTaskType.Refresh,
            refreshGroupId: rec.refreshGroupId,
          });
          res.taskIds.push(taskId);
        }
      }

      // Purchases

      {
        const activeRecs = await tx.purchases.indexes.byStatus.getAll(active);
        for (const rec of activeRecs) {
          const taskId = constructTaskIdentifier({
            tag: PendingTaskType.Purchase,
            proposalId: rec.proposalId,
          });
          res.taskIds.push(taskId);
        }
      }

      // peer-push-debit

      {
        const activeRecs =
          await tx.peerPushDebit.indexes.byStatus.getAll(active);
        for (const rec of activeRecs) {
          const taskId = constructTaskIdentifier({
            tag: PendingTaskType.PeerPushDebit,
            pursePub: rec.pursePub,
          });
          res.taskIds.push(taskId);
        }
      }

      // peer-push-credit

      {
        const activeRecs =
          await tx.peerPushCredit.indexes.byStatus.getAll(active);
        for (const rec of activeRecs) {
          const taskId = constructTaskIdentifier({
            tag: PendingTaskType.PeerPushCredit,
            peerPushCreditId: rec.peerPushCreditId,
          });
          res.taskIds.push(taskId);
        }
      }

      // peer-pull-debit

      {
        const activeRecs =
          await tx.peerPullDebit.indexes.byStatus.getAll(active);
        for (const rec of activeRecs) {
          const taskId = constructTaskIdentifier({
            tag: PendingTaskType.PeerPullDebit,
            peerPullDebitId: rec.peerPullDebitId,
          });
          res.taskIds.push(taskId);
        }
      }

      // peer-pull-credit

      {
        const activeRecs =
          await tx.peerPullCredit.indexes.byStatus.getAll(active);
        for (const rec of activeRecs) {
          const taskId = constructTaskIdentifier({
            tag: PendingTaskType.PeerPullCredit,
            pursePub: rec.pursePub,
          });
          res.taskIds.push(taskId);
        }
      }

      // recoup

      {
        const activeRecs =
          await tx.recoupGroups.indexes.byStatus.getAll(active);
        for (const rec of activeRecs) {
          const taskId = constructTaskIdentifier({
            tag: PendingTaskType.Recoup,
            recoupGroupId: rec.recoupGroupId,
          });
          res.taskIds.push(taskId);
        }
      }

      // exchange update

      {
        const exchanges = await tx.exchanges.getAll();
        for (const rec of exchanges) {
          const taskIdUpdate = constructTaskIdentifier({
            tag: PendingTaskType.ExchangeUpdate,
            exchangeBaseUrl: rec.baseUrl,
          });
          res.taskIds.push(taskIdUpdate);
        }
      }

      // FIXME: Recoup!
    },
  );

  return res;
}