/**
 * Starts the dev instances of `dev/instances.ts`, for `deno task dev`: for
 * each, an API server that restarts on change and a Vite server, wired to
 * each other and kept apart from the other instances by the rule that module
 * states. Every line they print is prefixed with the instance's name. Ctrl+C
 * stops them all, and so does any of them stopping, such as a Vite server
 * whose port is taken.
 *
 * It runs with the base `.env` loaded, which every server inherits, and starts
 * the instances it is given by name, or all of them. In the devcontainer, each
 * instance's service in `.devcontainer/compose.yaml` runs it for that
 * instance; outside, `deno task dev` runs it.
 *
 * @module
 */

import { type DevInstance, INSTANCES } from "./instances.ts";

/** The colors of the instances' prefixes, in the order of `INSTANCES`. */
const COLORS = [36, 35, 33, 32, 34, 31];

/**
 * Returns the environment of `instance`'s servers, over the inherited one:
 * the rule of `dev/instances.ts`, then the instance's own `env`.
 */
function envOf(instance: DevInstance): Record<string, string> {
  const { name, apiPort, webPort } = instance;
  return {
    GERBEUR_INSTANCE: name,
    GERBEUR_PORT: String(apiPort),
    GERBEUR_PUBLIC_URL: `http://localhost:${apiPort}`,
    GERBEUR_FRONTEND_URL: `http://localhost:${webPort}`,
    GERBEUR_DB_PATH: `api/sql/${name}.db`,
    GERBEUR_UPLOADS_DIR: `api/uploads/${name}`,
    // Every instance is on localhost, over http.
    GERBEUR_FEDERATION_ALLOW_PRIVATE: "1",
    VITE_API_PROTOCOL: "http",
    VITE_API_HOSTNAME: "localhost",
    VITE_API_PORT: String(apiPort),
    ...instance.env,
  };
}

/** Writes each line of `stream` to `out`, after `prefix`. */
async function pipeLines(
  stream: ReadableStream<Uint8Array>,
  out: typeof Deno.stdout,
  prefix: string,
): Promise<void> {
  const encoder = new TextEncoder();
  const decoder = new TextDecoder();
  let rest = "";
  for await (const bytes of stream) {
    const lines = (rest + decoder.decode(bytes, { stream: true })).split("\n");
    rest = lines.pop() ?? "";
    for (const line of lines) {
      await out.write(encoder.encode(`${prefix} ${line}\n`));
    }
  }
  if (rest) await out.write(encoder.encode(`${prefix} ${rest}\n`));
}

/** Returns the instances `names` asks for, all of them when it is empty. */
function pick(names: string[]): readonly DevInstance[] {
  const unknown = names.filter((n) => !INSTANCES.some((i) => i.name === n));
  if (unknown.length > 0) {
    console.error(
      `Unknown instance ${unknown.join(", ")}; dev/instances.ts has ${
        INSTANCES.map((i) => i.name).join(", ")
      }.`,
    );
    Deno.exit(1);
  }
  return names.length === 0
    ? INSTANCES
    : INSTANCES.filter((i) => names.includes(i.name));
}

const chosen = pick(Deno.args);
const width = Math.max(...chosen.map((i) => i.name.length)) + 4;
const children: { label: string; process: Deno.ChildProcess }[] = [];

for (const instance of chosen) {
  const color = COLORS[INSTANCES.indexOf(instance) % COLORS.length];
  const env = envOf(instance);
  for (
    const [role, args] of [
      ["api", ["run", "-A", "--watch", "api/main.ts"]],
      [
        "web",
        [
          "run",
          "-A",
          "npm:vite",
          "--port",
          String(instance.webPort),
          "--strictPort",
        ],
      ],
    ] as const
  ) {
    const label = `${instance.name}:${role}`;
    const prefix = `\x1b[${color}m${label.padEnd(width)}\x1b[0m│`;
    const process = new Deno.Command(Deno.execPath(), {
      args: [...args],
      env,
      stdin: "null",
      stdout: "piped",
      stderr: "piped",
    }).spawn();
    pipeLines(process.stdout, Deno.stdout, prefix);
    pipeLines(process.stderr, Deno.stderr, prefix);
    children.push({ label, process });
  }
}

console.log(
  chosen.map((i) =>
    `${
      i.name.padEnd(width)
    }  http://localhost:${i.webPort}  (API :${i.apiPort}, api/sql/${i.name}.db)`
  ).join("\n"),
);

let stopping = false;
/** Stops every server still running, then exits with `code`. */
async function stopAll(code: number): Promise<never> {
  if (!stopping) {
    stopping = true;
    for (const { process } of children) {
      try {
        process.kill("SIGTERM");
      } catch {
        // Already gone.
      }
    }
    await Promise.allSettled(children.map((c) => c.process.status));
  }
  Deno.exit(code);
}

for (const signal of ["SIGINT", "SIGTERM"] as const) {
  Deno.addSignalListener(signal, () => stopAll(0));
}

const first = await Promise.race(
  children.map(async ({ label, process }) => ({
    label,
    status: await process.status,
  })),
);
if (!stopping) {
  console.error(
    `${first.label} stopped (exit ${first.status.code}); stopping the others.`,
  );
  await stopAll(first.status.code || 1);
}