(core) move home server into core

Summary: This moves enough server material into core to run a home server.  The data engine is not yet incorporated (though in manual testing it works when ported).

Test Plan: existing tests pass

Reviewers: dsagal

Reviewed By: dsagal

Differential Revision: https://phab.getgrist.com/D2552

app/server/lib/ServerColumnGetters.ts

@@ -0,0 +1,41 @@
+import {ColumnGetters} from 'app/common/ColumnGetters';
+import * as gristTypes from 'app/common/gristTypes';
+
+/**
+ *
+ * An implementation of ColumnGetters for the server, currently
+ * drawing on the data and metadata prepared for CSV export.
+ *
+ */
+export class ServerColumnGetters implements ColumnGetters {
+  private _rowIndices: Map<number, number>;
+  private _colIndices: Map<number, string>;
+
+  constructor(rowIds: number[], private _dataByColId: {[colId: string]: any}, private _columns: any[]) {
+    this._rowIndices = new Map<number, number>(rowIds.map((rowId, r) => [rowId, r] as [number, number]));
+    this._colIndices = new Map<number, string>(_columns.map(col => [col.id, col.colId] as [number, string]));
+  }
+
+  public getColGetter(colRef: number): ((rowId: number) => any) | null {
+    const colId = this._colIndices.get(colRef);
+    if (colId === undefined) {
+      return null;
+    }
+    const col = this._dataByColId[colId];
+    return rowId => {
+      const idx = this._rowIndices.get(rowId);
+      if (idx === undefined) {
+        return null;
+      }
+      return col[idx];
+    };
+  }
+
+  public getManualSortGetter(): ((rowId: number) => any) | null {
+    const manualSortCol = this._columns.find(c => c.colId === gristTypes.MANUALSORT);
+    if (!manualSortCol) {
+      return null;
+    }
+    return this.getColGetter(manualSortCol.id);
+  }
+}