feat: workspace view for schedules (#991)

Summary:

This adds the client-side implementation to match the types introduced
in #879 and #844 as well as a card in the Workspaces page to present
workspace the data.

Details:

* Added a convenient line break in the example schedule.Weekly
* Added missing `json:""` annotations in codersdk/workspaces.go
* Installed cronstrue for displaying human-friendly cron strings
* Adjusted/Added client-side types to match codersdk/workspaces.go
* Added new component WorkspaceSchedule.tsx

Next Steps:

The WorkspaceSchedule.tsx card only presents data (on purpose). In order
to make it PUT/modify data, a few changes will be made:

- a form for updating workspace schedule will be created
- the form will wrapped in a dialog or modal
- the WorkspaceSchedule card will have a way of opening the modal which
will likely be generalized up to WorkspaceSection.tsx

Impact:

This is user-facing

This does not fully resolve either #274 or #275 (I may further decompose
that work to reflect reality and keep things in small deliverable
increments), but adds significant progress towards both.

site/src/util/schedule.test.ts

@@ -0,0 +1,33 @@
+import { expandScheduleCronString, extractTimezone, stripTimezone } from "./schedule"
+
+describe("util/schedule", () => {
+  describe("stripTimezone", () => {
+    it.each<[string, string]>([
+      ["CRON_TZ=Canada/Eastern 30 9 1-5", "30 9 1-5"],
+      ["CRON_TZ=America/Central 0 8 1,2,4,5", "0 8 1,2,4,5"],
+      ["30 9 1-5", "30 9 1-5"],
+    ])(`stripTimezone(%p) returns %p`, (input, expected) => {
+      expect(stripTimezone(input)).toBe(expected)
+    })
+  })
+
+  describe("extractTimezone", () => {
+    it.each<[string, string]>([
+      ["CRON_TZ=Canada/Eastern 30 9 1-5", "Canada/Eastern"],
+      ["CRON_TZ=America/Central 0 8 1,2,4,5", "America/Central"],
+      ["30 9 1-5", "UTC"],
+    ])(`extractTimezone(%p) returns %p`, (input, expected) => {
+      expect(extractTimezone(input)).toBe(expected)
+    })
+  })
+
+  describe("expandScheduleCronString", () => {
+    it.each<[string, string]>([
+      ["CRON_TZ=Canada/Eastern 30 9 1-5", "30 9 * * 1-5"],
+      ["CRON_TZ=America/Central 0 8 1,2,4,5", "0 8 * * 1,2,4,5"],
+      ["30 9 1-5", "30 9 * * 1-5"],
+    ])(`expandScheduleCronString(%p) returns %p`, (input, expected) => {
+      expect(expandScheduleCronString(input)).toBe(expected)
+    })
+  })
+})

site/src/util/schedule.ts

@@ -0,0 +1,54 @@
+/**
+ * @fileoverview Client-side counterpart of the coderd/autostart/schedule Go
+ * package. This package is a variation on crontab that uses minute, hour and
+ * day of week.
+ */
+
+/**
+ * DEFAULT_TIMEZONE is the default timezone that crontab assumes unless one is
+ * specified.
+ */
+const DEFAULT_TIMEZONE = "UTC"
+
+/**
+ * stripTimezone strips a leading timezone from a schedule string
+ */
+export const stripTimezone = (raw: string): string => {
+  return raw.replace(/CRON_TZ=\S*\s/, "")
+}
+
+/**
+ * extractTimezone returns a leading timezone from a schedule string if one is
+ * specified; otherwise DEFAULT_TIMEZONE
+ */
+export const extractTimezone = (raw: string): string => {
+  const matches = raw.match(/CRON_TZ=\S*\s/g)
+
+  if (matches && matches.length) {
+    return matches[0].replace(/CRON_TZ=/, "").trim()
+  } else {
+    return DEFAULT_TIMEZONE
+  }
+}
+
+/**
+ * expandScheduleCronString ensures a Schedule is expanded to a valid 5-value
+ * cron string by inserting '*' in month and day positions. If there is a
+ * leading timezone, it is removed.
+ *
+ * @example
+ * expandScheduleCronString("30 9 1-5") // -> "30 9 * * 1-5"
+ */
+export const expandScheduleCronString = (schedule: string): string => {
+  const prepared = stripTimezone(schedule).trim()
+
+  const parts = prepared.split(" ")
+
+  while (parts.length < 5) {
+    // insert '*' in the second to last position
+    // ie [a, b, c] --> [a, b, *, c]
+    parts.splice(parts.length - 1, 0, "*")
+  }
+
+  return parts.join(" ")
+}