monitor.status-page

export function statusPage(components: readonly Component[]): StatusSummary

/** One row of a status page. */
export interface Component {
  readonly name: string;
  readonly state: ComponentState;
}

/** The banner at the top of the page. */
export interface StatusSummary {
  /** the worst component state */
  readonly state: ComponentState;
  /** "All systems operational", "Degraded performance", "Partial outage", "Major outage" or "Scheduled maintenance" */
  readonly headline: string;
  /** names of the components not operational, in input order */
  readonly affected: readonly string[];
}

import { statusPage } from "#fune/monitor.status-page@^1";

import { type ComponentState } from "./monitor_component_state.ts";  ← from monitor.component-state ^1.0.0 · built alongside by fune
import { type Component, type StatusSummary } from "./monitor_status_page_types.ts";

// Worst first. Maintenance ranks below every real problem: an outage elsewhere
// during planned work is still the headline.
const RANK: readonly ComponentState[] = ["operational", "maintenance", "degraded", "partial-outage", "major-outage"];
const HEADLINE: Readonly<Record<ComponentState, string>> = {
  "operational": "All systems operational",
  "maintenance": "Scheduled maintenance",
  "degraded": "Degraded performance",
  "partial-outage": "Partial outage",
  "major-outage": "Major outage",
};

/** The banner for a whole status page: the worst component state wins. */
export function statusPage(components: readonly Component[]): StatusSummary {
  if (components.length === 0) throw new RangeError("components must not be empty");
  const seen = new Set<string>();
  let worst = 0;
  const affected: string[] = [];
  for (const c of components) {
    if (c.name === "") throw new RangeError("component name must not be empty");
    if (seen.has(c.name)) throw new RangeError(`duplicate component name: ${c.name}`);
    seen.add(c.name);
    const rank = RANK.indexOf(c.state);
    if (rank < 0) throw new RangeError(`unknown component state: ${String(c.state)}`);
    if (rank > worst) worst = rank;
    if (rank > 0) affected.push(c.name);
  }
  return { state: RANK[worst], headline: HEADLINE[RANK[worst]], affected };
}

Install

fune build

With that line in your source, in a TypeScript project (language typescript in fune.project), fune build resolves it and its 1 dependency, pins them in fune.lock, downloads only the TypeScript package of each, and builds the code above into your project’s .fune/build, one readable file per capability with a header linking back here. Or pin a range in fune.project and build in one step:

fune add monitor.status-page

The manifest, vectors and README with only the TypeScript implementation. Install it without the registry with fune add ./monitor.status-page-1.0.0-typescript.fune, or fetch it from a terminal with fune pull monitor.status-page@1.0.0:typescript.

The whole function, every language, is one file too: monitor.status-page-1.0.0.fune, 13,298 bytes, sha256 d9db4b93cf50e564dd970817a68ff904dff2740c164187a2bb320660670351ae. It installs into a project of any language.

// fune: before monitor.status-page

// fune: after monitor.status-page

// fune: replace monitor.component-state in monitor.status-page

// fune: step monitor.status-page after <n|label>

More from the author

major-outage > partial-outage > degraded > maintenance > operational

| state | headline | | --- | --- | | `major-outage` | Major outage | | `partial-outage` | Partial outage | | `degraded` | Degraded performance | | `maintenance` | Scheduled maintenance | | `operational` | All systems operational |

Maintenance ranks below every real problem: a component that is degraded while another is under planned maintenance is the news. It still ranks above operational, and a component under maintenance is listed in `affected`, so readers know it may be unavailable.

`affected` is in input order (the order the page lists its components), not sorted by severity, so it matches the page.

## Decisions

- **No components is an error**, not "All systems operational": a page with nothing on it is a configuration mistake, and claiming all is well would hide it. - **Names must be unique and non-empty.** Duplicates would make `affected` ambiguous. Names are compared exactly, so `api` and `API` are different. - States use the registry's kebab-case (`major-outage`); Statuspage's API spelling (`major_outage`) is refused rather than guessed at.

## Errors

- `components must not be empty` - `component name must not be empty` - `duplicate component name: X` - `unknown component state: X`

## Sources

- Atlassian Support, "Show service status with components": https://support.atlassian.com/statuspage/docs/show-service-status-with-components/ - Statuspage Status API, page status and component statuses: https://metastatuspage.com/api. Statuspage's own overall indicator is `none | minor | major | critical`; this capability reports the worst component state instead, which says more and maps onto it directly.

Files