(core) Download as CSV button on sections

Summary: Adding "Download as CSV" button that exports filtred section data to csv

Test Plan: Browser tests

Reviewers: paulfitz, dsagal

Reviewed By: paulfitz

Differential Revision: https://phab.getgrist.com/D2830

app/common/ColumnFilterFunc.ts

@@ -0,0 +1,18 @@
+import { CellValue } from "app/common/DocActions";
+import { FilterState, makeFilterState } from "app/common/FilterState";
+
+export type ColumnFilterFunc = (value: CellValue) => boolean;
+
+// Returns a filter function for a particular column: the function takes a cell value and returns
+// whether it's accepted according to the given FilterState.
+export function makeFilterFunc({ include, values }: FilterState): ColumnFilterFunc {
+  // NOTE: This logic results in complex values and their stringified JSON representations as equivalent.
+  // For example, a TypeError in the formula column and the string '["E","TypeError"]' would be seen as the same.
+  // TODO: This narrow corner case seems acceptable for now, but may be worth revisiting.
+  return (val: CellValue) => (values.has(Array.isArray(val) ? JSON.stringify(val) : val) === include);
+}
+
+// Given a JSON string, returns a ColumnFilterFunc
+export function buildColFilter(filterJson: string | undefined): ColumnFilterFunc | null {
+  return filterJson ? makeFilterFunc(makeFilterState(filterJson)) : null;
+}

app/common/FilterState.ts

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+import { CellValue } from "app/common/DocActions";
+
+// Filter object as stored in the db
+export interface FilterSpec {
+  included?: CellValue[];
+  excluded?: CellValue[];
+}
+
+// A more efficient representation of filter state for a column than FilterSpec.
+export interface FilterState {
+  include: boolean;
+  values: Set<CellValue>;
+}
+
+// Creates a FilterState. Accepts spec as a json string or a FilterSpec.
+export function makeFilterState(spec: string | FilterSpec): FilterState {
+  if (typeof (spec) === 'string') {
+    return makeFilterState((spec && JSON.parse(spec)) || {});
+  }
+  return {
+    include: Boolean(spec.included),
+    values: new Set(spec.included || spec.excluded || []),
+  };
+}
+
+// Returns true if state and spec are equivalent, false otherwise.
+export function isEquivalentFilter(state: FilterState, spec: FilterSpec): boolean {
+  const other = makeFilterState(spec);
+  if (state.include !== other.include) { return false; }
+  if (state.values.size !== other.values.size) { return false; }
+  for (const val of other.values) { if (!state.values.has(val)) { return false; } }
+  return true;
+}

app/common/RowFilterFunc.ts

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+import { CellValue } from "app/common/DocActions";
+import { ColumnFilterFunc } from "app/common/ColumnFilterFunc";
+
+export type RowFilterFunc<T> = (row: T) => boolean;
+
+// Builds RowFilter for a single column
+export function buildRowFilter<T>(
+  getter: RowValueFunc<T> | null,
+  filterFunc: ColumnFilterFunc | null): RowFilterFunc<T> {
+  if (!getter || !filterFunc) {
+    return () => true;
+  }
+  return (rowId: T) => filterFunc(getter(rowId));
+}
+
+export type RowValueFunc<T> = (rowId: T) => CellValue;