Rewrite the CLI internals

packages/alfa-cli/bin/alfa.ts

@@ -1,14 +1,62 @@
 #!/usr/bin/env node
 
-import * as command from "@oclif/command";
-import * as errors from "@oclif/errors";
-
-async function alfa() {
-  try {
-    await command.run();
-  } catch (err) {
-    errors.handle(err);
-  }
-}
-
-alfa();
+/// <reference types="node" />
+
+import * as path from "path";
+import * as process from "process";
+import * as tty from "tty";
+
+import { Command, Flag } from "@siteimprove/alfa-command";
+import { None } from "@siteimprove/alfa-option";
+import { Err } from "@siteimprove/alfa-result";
+
+import * as pkg from "../package.json";
+
+import audit from "./alfa/command/audit";
+import scrape from "./alfa/command/scrape";
+
+const {
+  argv: [node, bin],
+  platform,
+  arch,
+  version,
+} = process;
+
+const application = Command.withSubcommands(
+  path.basename(bin),
+  `${pkg.name}/${pkg.version} ${platform}-${arch} node-${version}`,
+  `The tool for all your accessibility needs on the command line.`,
+  {
+    help: Flag.help("Display the help information."),
+    version: Flag.version("Output the current version."),
+  },
+  (self) => ({
+    audit: audit(self),
+    scrape: scrape(self),
+  }),
+  None
+);
+
+application
+  .run(process.argv.slice(2))
+  .catch((err: Error) => Err.of(`${err.message}`))
+  .then((result) => {
+    let stream: tty.WriteStream;
+    let output: string;
+
+    if (result.isOk()) {
+      stream = process.stdout;
+      output = result.get();
+    } else {
+      stream = process.stderr;
+      output = result.getErr();
+    }
+
+    output = output.trimRight();
+
+    if (output.length > 0) {
+      stream.write(output + "\n");
+    }
+
+    process.exit(result.isOk() ? 0 : 1);
+  });

packages/alfa-cli/bin/alfa/command/audit.ts

@@ -0,0 +1,22 @@
+import { Command } from "@siteimprove/alfa-command";
+import { Option } from "@siteimprove/alfa-option";
+
+import { Arguments } from "./audit/arguments";
+import { Flags } from "./audit/flags";
+
+/**
+ * @internal
+ */
+export default (parent: Command) =>
+  Command.withArguments(
+    "audit",
+    parent.version,
+    "Perform an accessibility audit of a page.",
+    Flags,
+    Arguments,
+    Option.of(parent),
+    () => async (...args) => {
+      const { run } = await import("./audit/run");
+      return run(...args);
+    }
+  );

packages/alfa-cli/bin/alfa/command/audit/arguments.ts

@@ -0,0 +1,11 @@
+import { Argument } from "@siteimprove/alfa-command";
+
+export const Arguments = {
+  url: Argument.string(
+    "url",
+    `The URL of the page to audit. Both remote and local protocols are
+    supported so the URL can either be an address of a remote page or a path to
+    a local file. If no URL is provided, an already serialised page will be read
+    from stdin.`
+  ).optional(),
+};

packages/alfa-cli/bin/alfa/command/audit/flags.ts

@@ -0,0 +1,40 @@
+import { Flag } from "@siteimprove/alfa-command";
+
+import * as scrape from "../scrape/flags";
+
+export const Flags = {
+  help: Flag.help("Display the help information."),
+
+  interactive: Flag.boolean(
+    "interactive",
+    "Whether or not to run an interactive audit."
+  )
+    .alias("i")
+    .default(false),
+
+  format: Flag.string("format", "The reporting format to use.")
+    .type("format or package")
+    .alias("f")
+    .default("earl"),
+
+  output: Flag.string(
+    "output",
+    `The path to write results to. If no path is provided, results are written
+    to stdout.`
+  )
+    .type("path")
+    .alias("o")
+    .optional(),
+
+  outcomes: Flag.string(
+    "outcome",
+    `The type of outcome to include in the results. If not provided, all types
+    of outcomes are included. This flag can be repeated to include multiple
+    types of outcomes.`
+  )
+    .choices("passed", "failed", "inapplicable", "cantTell")
+    .repeatable()
+    .optional(),
+
+  ...scrape.Flags,
+};

packages/alfa-cli/bin/alfa/command/audit/run.ts

@@ -0,0 +1,97 @@
+/// <reference types="node" />
+
+import * as fs from "fs";
+
+import { Audit, Outcome } from "@siteimprove/alfa-act";
+import { Command } from "@siteimprove/alfa-command";
+import { Node } from "@siteimprove/alfa-dom";
+import { Formatter } from "@siteimprove/alfa-formatter";
+import { Iterable } from "@siteimprove/alfa-iterable";
+import { None } from "@siteimprove/alfa-option";
+import { Ok } from "@siteimprove/alfa-result";
+import { Rules, Question } from "@siteimprove/alfa-rules";
+import { Page } from "@siteimprove/alfa-web";
+
+import { Oracle } from "../../oracle";
+
+import type { Arguments } from "./arguments";
+import type { Flags } from "./flags";
+
+import * as scrape from "../scrape/run";
+
+type Input = Page;
+type Target = Node | Iterable<Node>;
+
+export const run: Command.Runner<typeof Flags, typeof Arguments> = async ({
+  flags,
+  args: { url: target },
+}) => {
+  const formatter = Formatter.load<Input, Target, Question>(flags.format);
+
+  if (formatter.isErr()) {
+    return formatter;
+  }
+
+  let json: string;
+
+  if (target.isNone()) {
+    json = fs.readFileSync(0, "utf-8");
+  } else {
+    const result = await scrape.run({
+      flags: {
+        ...flags,
+        output: None,
+      },
+      args: {
+        url: target.get(),
+      },
+    });
+
+    if (result.isErr()) {
+      return result;
+    }
+
+    json = result.get();
+  }
+
+  const page = Page.from(JSON.parse(json));
+
+  const audit = Rules.reduce(
+    (audit, rule) => audit.add(rule),
+    Audit.of<Input, Target, Question>(
+      page,
+      flags.interactive ? Oracle(page) : undefined
+    )
+  );
+
+  let outcomes = await audit.evaluate();
+
+  if (flags.outcomes.isSome()) {
+    const filter = new Set(flags.outcomes.get());
+
+    outcomes = Iterable.filter(outcomes, (outcome) => {
+      if (Outcome.isPassed(outcome)) {
+        return filter.has("passed");
+      }
+
+      if (Outcome.isFailed(outcome)) {
+        return filter.has("failed");
+      }
+
+      if (Outcome.isInapplicable(outcome)) {
+        return filter.has("inapplicable");
+      }
+
+      return filter.has("cantTell");
+    });
+  }
+
+  const output = formatter.get()(page, outcomes);
+
+  if (flags.output.isNone()) {
+    return Ok.of(output);
+  } else {
+    fs.writeFileSync(flags.output.get() + "\n", output);
+    return Ok.of("");
+  }
+};

packages/alfa-cli/bin/alfa/command/scrape.ts

@@ -0,0 +1,22 @@
+import { Command } from "@siteimprove/alfa-command";
+import { Option } from "@siteimprove/alfa-option";
+
+import { Arguments } from "./scrape/arguments";
+import { Flags } from "./scrape/flags";
+
+/**
+ * @internal
+ */
+export default (parent: Command) =>
+  Command.withArguments(
+    "scrape",
+    parent.version,
+    "Scrape a page and output it in a serialisable format.",
+    Flags,
+    Arguments,
+    Option.of(parent),
+    () => async (...args) => {
+      const { run } = await import("./scrape/run");
+      return run(...args);
+    }
+  );

packages/alfa-cli/bin/alfa/command/scrape/arguments.ts

@@ -0,0 +1,10 @@
+import { Argument } from "@siteimprove/alfa-command";
+
+export const Arguments = {
+  url: Argument.string(
+    "url",
+    `The URL of the page to scrape. Both remote and local protocols are
+    supported so the URL can either be an address of a remote page or a path to
+    a local file.`
+  ),
+};