import { BulkColValues, ColValues, DocAction, isSchemaAction,
         TableDataAction, UserAction } from 'app/common/DocActions';

const ACTION_TYPES = new Set([
  'AddRecord', 'BulkAddRecord', 'UpdateRecord', 'BulkUpdateRecord',
  'RemoveRecord', 'BulkRemoveRecord'
]);

/**
 * The result of processing a UserAction.
 */
export interface ProcessedAction {
  stored: DocAction[];
  undo: DocAction[];
  retValues: any;
}

/**
 * A minimal interface for interpreting UserActions in the context of
 * some current state. We need to know the next free rowId for each
 * table, and also the current state of cells. This interface was
 * abstracted from the initial implementation of on-demand tables.
 */
export interface AlternateStorage {
  getNextRowId(tableId: string): Promise<number>;
  fetchActionData(tableId: string, rowIds: number[],
                  colIds?: string[]): Promise<TableDataAction>;
}

/**
 * Handle converting UserActions to DocActions for tables stored
 * in some way that is not handled by the regular data engine.
 */
export class AlternateActions {

  constructor(private _storage: AlternateStorage) {}

  /**
   * This may be overridden to allow mixing two different storage mechanisms.
   * The implementation of on-demand tables does this.
   */
  public usesAlternateStorage(tableId: string): boolean {
    return true;
  }

  /**
   * Convert a UserAction into stored and undo DocActions as well as return values.
   */
  public processUserAction(action: UserAction): Promise<ProcessedAction> {
    const a = action.map(item => item as any);
    switch (a[0]) {
      case "ApplyUndoActions": return this._doApplyUndoActions(a[1]);
      case "AddRecord":        return this._doAddRecord       (a[1], a[2], a[3]);
      case "BulkAddRecord":    return this._doBulkAddRecord   (a[1], a[2], a[3]);
      case "UpdateRecord":     return this._doUpdateRecord    (a[1], a[2], a[3]);
      case "BulkUpdateRecord": return this._doBulkUpdateRecord(a[1], a[2], a[3]);
      case "RemoveRecord":     return this._doRemoveRecord    (a[1], a[2]);
      case "BulkRemoveRecord": return this._doBulkRemoveRecord(a[1], a[2]);
      default: throw new Error(`Received unknown action ${action[0]}`);
    }
  }

  /**
   * Splits an array of UserActions into two separate arrays of normal and onDemand actions.
   */
  public splitByStorage(actions: UserAction[]): [UserAction[], UserAction[]] {
    const normal: UserAction[] = [];
    const onDemand: UserAction[] = [];
    actions.forEach(a => {
      // Check that the actionType can be applied without the sandbox and also that the action
      // is on a data table.
      const isOnDemandAction = ACTION_TYPES.has(a[0] as string);
      const isDataTableAction = typeof a[1] === 'string' && !a[1].startsWith('_grist_');
      if (a[0] === 'ApplyUndoActions') {
        // Split actions inside the undo action array.
        const [undoNormal, undoOnDemand] = this.splitByStorage(a[1] as UserAction[]);
        if (undoNormal.length > 0) {
          normal.push(['ApplyUndoActions', undoNormal]);
        }
        if (undoOnDemand.length > 0) {
          onDemand.push(['ApplyUndoActions', undoOnDemand]);
        }
      } else if (isDataTableAction && isOnDemandAction && this.usesAlternateStorage(a[1] as string)) {
        // Check whether the tableId belongs to an onDemand table.
        onDemand.push(a);
      } else {
        normal.push(a);
      }
    });
    return [normal, onDemand];
  }

  /**
   * Check if an action represents a schema change on an onDemand table.
   */
  public isSchemaAction(docAction: DocAction): boolean {
   return isSchemaAction(docAction) && this.usesAlternateStorage(docAction[1]);
  }

  private async _doApplyUndoActions(actions: DocAction[]) {
    const undo: DocAction[] = [];
    for (const a of actions) {
      const converted = await this.processUserAction(a);
      undo.concat(converted.undo);
    }
    return {
      stored: actions,
      undo,
      retValues: null
    };
  }

  private async _doAddRecord(
    tableId: string,
    rowId: number|null,
    colValues: ColValues
  ): Promise<ProcessedAction> {
    if (rowId === null) {
      rowId = await this._storage.getNextRowId(tableId);
    }
    // Set the manualSort to be the same as the rowId. This forces new rows to always be added
    // at the end of the table.
    colValues.manualSort = rowId;
    return {
      stored: [['AddRecord', tableId, rowId, colValues]],
      undo: [['RemoveRecord', tableId, rowId]],
      retValues: rowId
    };
  }

  private async _doBulkAddRecord(
    tableId: string,
    rowIds: Array<number|null>,
    colValues: BulkColValues
  ): Promise<ProcessedAction> {

    // When unset, we will set the rowId values to count up from the greatest
    // values already in the table.
    if (rowIds[0] === null) {
      const nextRowId = await this._storage.getNextRowId(tableId);
      for (let i = 0; i < rowIds.length; i++) {
        rowIds[i] = nextRowId + i;
      }
    }
    // Set the manualSort values to be the same as the rowIds. This forces new rows to always be
    // added at the end of the table.
    colValues.manualSort = rowIds;
    return {
      stored: [['BulkAddRecord', tableId, rowIds as number[], colValues]],
      undo: [['BulkRemoveRecord', tableId, rowIds as number[]]],
      retValues: rowIds
    };
  }

  private async _doUpdateRecord(
    tableId: string,
    rowId: number,
    colValues: ColValues
  ): Promise<ProcessedAction> {
    const [, , oldRowIds, oldColValues] =
      await this._storage.fetchActionData(tableId, [rowId], Object.keys(colValues));
    return {
      stored: [['UpdateRecord', tableId, rowId, colValues]],
      undo: [['BulkUpdateRecord', tableId, oldRowIds, oldColValues]],
      retValues: null
    };
  }

  private async _doBulkUpdateRecord(
    tableId: string,
    rowIds: number[],
    colValues: BulkColValues
  ): Promise<ProcessedAction> {
    const [, , oldRowIds, oldColValues] =
      await this._storage.fetchActionData(tableId, rowIds, Object.keys(colValues));
    return {
      stored: [['BulkUpdateRecord', tableId, rowIds, colValues]],
      undo: [['BulkUpdateRecord', tableId, oldRowIds, oldColValues]],
      retValues: null
    };
  }

  private async _doRemoveRecord(tableId: string, rowId: number): Promise<ProcessedAction> {
    const [, , oldRowIds, oldColValues] = await this._storage.fetchActionData(tableId, [rowId]);
    return {
      stored: [['RemoveRecord', tableId, rowId]],
      undo: [['BulkAddRecord', tableId, oldRowIds, oldColValues]],
      retValues: null
    };
  }

  private async _doBulkRemoveRecord(tableId: string, rowIds: number[]): Promise<ProcessedAction> {
    const [, , oldRowIds, oldColValues] = await this._storage.fetchActionData(tableId, rowIds);
    return {
      stored: [['BulkRemoveRecord', tableId, rowIds]],
      undo: [['BulkAddRecord', tableId, oldRowIds, oldColValues]],
      retValues: null
    };
  }
}