Generalize configuration

There is now a single facility for configuring anything that is
configurable.

And we've stopped using SvelteKit's `env` facilities, as they're pretty
obnoxious: trying to type the environment in your framework is quixotic.
It's up to the application to do that, and so we do it.

.github/workflows/ci.yml

@@ -7,10 +7,6 @@ on:
 jobs:
   build-lint-test:
     runs-on: ubuntu-latest
-    env:
-      # This needs to be defined for the build to succeed, though it is not
-      # actually used for anything.
-      ZOEKT_URL: "https://www.example.com"
     steps:
       - uses: actions/checkout@v3
       - uses: actions/setup-node@v3

.gitignore

@@ -6,3 +6,4 @@ node_modules/
 .svelte-kit
 build/
 .env
+.envrc

README.md

@@ -8,22 +8,43 @@ There is a [demo deployment](./demo) at https://neogrok-demo-web.fly.dev/. This
 deployment's configuration can serve as a guide for your own deployments of
 neogrok; currently there are no packaged distributions.
 
+## Configuration
+
+Neogrok may be [configured](./src/lib/server/configuration.ts) using a JSON
+configuration file, or, where possible, environment variables. Configuration
+options defined in the environment take precedence over those defined in the
+configuration file.
+
+The configuration file is read from `/etc/neogrok/configuration.json` by
+default, but the location may be customized using the environment variable
+`NEOGROK_CONFIG_FILE`. The file is entirely optional, as all of the required
+configuration may be defined in the environment. If it is present, the file's
+contents must be a JSON object with zero or more entires, whose keys correspond
+to the option names tabulated below.
+
+### Configuration options
+
+| Option name               | Environment variable name | Required Y/N | Description                                                                                                                          |
+| :------------------------ | :------------------------ | :----------- | :----------------------------------------------------------------------------------------------------------------------------------- |
+| `zoektUrl`                | `ZOEKT_URL`               | Y            | The base zoekt URL at which neogrok will make API requests, at e.g. `/api/search` and `/api/list`                                    |
+| `openGrokProjectMappings` | N/A                       | N            | An object mapping OpenGrok project names to zoekt repository names; see [below]('#renaming-opengrok-projects-to-zoekt-repositories') |
+
 ## OpenGrok compatibility
 
 As an added bonus, neogrok can serve as a replacement for existing deployments
 of [OpenGrok](https://oracle.github.io/opengrok/), a much older, more intricate,
 slower, and generally jankier code search engine than zoekt. Neogrok strives to
 provide URL compatibility with OpenGrok by redirecting OpenGrok URLs to their
 neogrok equivalents: simply deploy neogrok at the same origin previously hosting
-your OpenGrok instance, and everything will Just Work™. (Perfect compatibility
-is not possible as the feature sets of each search engine do not map
-one-to-one.)
+your OpenGrok instance, and everything will Just Work™. To the best of our
+ability, OpenGrok Lucene queries will be rewritten to the most possibly
+equivalent zoekt queries. (Perfect compatibility is not possible as the feature
+sets of each search engine do not map one-to-one.)
 
-### Renaming OpenGrok projects to zoekt repository
+### Renaming OpenGrok projects to zoekt repositories
 
 If your OpenGrok project names are not identical to their equivalent zoekt
-repository names, you can run `neogrok` with an environment variable
-`OPENGROK_PROJECT_MAPPINGS_FILE` that points at a JSON file whose contents are
-an object mapping OpenGrok project names to zoekt repository names. With this
-data provided, neogrok can rewrite OpenGrok queries that include project names
-appropriately.
+repository names, you can run `neogrok` with the appropriate
+[`openGrokProjectMappings` configuration](#configuration), which maps OpenGrok
+project names to zoekt repository names. With this data provided, neogrok can
+rewrite OpenGrok queries that include project names appropriately.

demo/fly.neogrok.toml

@@ -1,15 +1,12 @@
-# fly.toml file generated for neogrok-demo-web on 2023-01-17T03:13:51-05:00
-
 app = "neogrok-demo-web"
 primary_region = "ewr"
 
 [build]
   dockerfile = "Dockerfile.neogrok"
-[build.args]
-  ZOEKT_URL = "http://neogrok-demo-zoekt.internal:8080"
 
 [env]
   PORT = 8080
+  ZOEKT_URL = "http://neogrok-demo-zoekt.internal:8080"
 
 [experimental]
   auto_rollback = true

src/hooks.server.ts

@@ -0,0 +1,12 @@
+// Eagerly resolve the configuration on startup, such that startup fails if the
+// configuration is invalid.
+//
+// We don't actually use any of the features of this hooks module, other than
+// that it is evaluated on startup; other modules are not.
+import "$lib/server/configuration";
+
+// TODO we should have prom metrics, on, among other things, HTTP requests
+// handled, and the `handle` hook would be a good way to do that.
+
+// TODO SvelteKit logs an error every time anything requests a URL that does not
+// map to a route. Bonkers. Silence those by implementing `handleError`.

src/lib/server/configuration.ts

@@ -0,0 +1,65 @@
+import * as v from "@badrap/valita";
+import fs from "node:fs";
+
+const zoektUrlSchema = v.string().map((u) => new URL(u));
+const fileConfigurationSchema = v.object({
+  zoektUrl: zoektUrlSchema.optional(),
+  openGrokProjectMappings: v
+    .record(v.string())
+    .map((o) => new Map(Object.entries(o)))
+    .optional(),
+});
+type FileConfiguration = v.Infer<typeof fileConfigurationSchema>;
+
+const environmentConfigurationSchema = v.object({
+  ZOEKT_URL: zoektUrlSchema.optional(),
+});
+
+type Configuration = {
+  readonly zoektUrl: URL;
+  readonly openGrokProjectMappings: ReadonlyMap<string, string>;
+};
+export const configuration: Configuration = await (async function () {
+  const defaultConfigFilePath = "/etc/neogrok/config.json";
+  const configFilePath =
+    process.env.NEOGROK_CONFIG_FILE ?? defaultConfigFilePath;
+  let fileConfig: FileConfiguration | undefined;
+  try {
+    fileConfig = fileConfigurationSchema.parse(
+      JSON.parse(await fs.promises.readFile(configFilePath, "utf8")),
+      { mode: "strict" }
+    );
+  } catch (e) {
+    // Swallow errors related to the default config file being missing.
+    if (
+      !(
+        e &&
+        typeof e === "object" &&
+        "code" in e &&
+        e.code === "ENOENT" &&
+        configFilePath === defaultConfigFilePath
+      )
+    ) {
+      throw new Error(`Configuration file at ${configFilePath} is invalid`, {
+        cause: e,
+      });
+    }
+  }
+
+  const environmentConfig = environmentConfigurationSchema.parse(process.env, {
+    mode: "strip",
+  });
+
+  const zoektUrl = environmentConfig.ZOEKT_URL ?? fileConfig?.zoektUrl;
+  if (zoektUrl === undefined) {
+    throw new Error(
+      `"ZOEKT_URL" must be defined in the environment, or "zoektUrl" must be defined in the configuration file at ${configFilePath}`
+    );
+  }
+
+  return {
+    zoektUrl,
+    openGrokProjectMappings:
+      fileConfig?.openGrokProjectMappings ?? new Map<string, string>(),
+  };
+})();

src/lib/server/search-api.ts

@@ -1,6 +1,6 @@
 import * as v from "@badrap/valita";
 import type { ReadonlyDeep } from "type-fest";
-import { ZOEKT_URL } from "$env/static/private";
+import { configuration } from "./configuration";
 import {
   type ContentToken,
   parseChunkMatch,
@@ -45,7 +45,7 @@ export const search = async (
     },
   });
 
-  const response = await f(new URL("/api/search", ZOEKT_URL), {
+  const response = await f(new URL("/api/search", configuration.zoektUrl), {
     method: "POST",
     headers: {
       "content-type": "application/json",

src/lib/server/zoekt-list-repositories.ts

@@ -1,6 +1,6 @@
 import * as v from "@badrap/valita";
 import type { ReadonlyDeep } from "type-fest";
-import { ZOEKT_URL } from "$env/static/private";
+import { configuration } from "./configuration";
 
 export type ListRepositoriesResponse =
   | {
@@ -18,7 +18,7 @@ export async function listRepositories(
 ): Promise<ListRepositoriesResponse> {
   const body = JSON.stringify({ q: query });
 
-  const response = await f(new URL("/api/list", ZOEKT_URL), {
+  const response = await f(new URL("/api/list", configuration.zoektUrl), {
     method: "POST",
     headers: {
       "content-type": "application/json",

src/routes/(opengrok-compat)/diff/[project]/[...file]/+page.server.ts

@@ -1,5 +1,5 @@
 import { escapeRegExp } from "$lib/regexp";
-import { projectToRepo } from "$lib/server/opengrok-compat";
+import { configuration } from "$lib/server/configuration";
 import { listRepositories } from "$lib/server/zoekt-list-repositories";
 import { error, redirect } from "@sveltejs/kit";
 
@@ -14,7 +14,7 @@ export const load: import("./$types").PageServerLoad = async ({
     throw error(404);
   }
   const revision = url.searchParams.get("r");
-  const convertedRepo = projectToRepo.get(project);
+  const convertedRepo = configuration.openGrokProjectMappings.get(project);
 
   const result = await listRepositories(
     {

src/routes/(opengrok-compat)/download/[project]/[...file]/+page.server.ts

@@ -1,5 +1,5 @@
 import { escapeRegExp } from "$lib/regexp";
-import { projectToRepo } from "$lib/server/opengrok-compat";
+import { configuration } from "$lib/server/configuration";
 import { listRepositories } from "$lib/server/zoekt-list-repositories";
 import { error, redirect } from "@sveltejs/kit";
 
@@ -14,7 +14,7 @@ export const load: import("./$types").PageServerLoad = async ({
     throw error(404);
   }
   const revision = url.searchParams.get("r");
-  const convertedRepo = projectToRepo.get(project);
+  const convertedRepo = configuration.openGrokProjectMappings.get(project);
 
   const result = await listRepositories(
     {

src/routes/(opengrok-compat)/history/[project]/[...file]/+page.server.ts

@@ -1,5 +1,5 @@
 import { escapeRegExp } from "$lib/regexp";
-import { projectToRepo } from "$lib/server/opengrok-compat";
+import { configuration } from "$lib/server/configuration";
 import { listRepositories } from "$lib/server/zoekt-list-repositories";
 import { redirect } from "@sveltejs/kit";
 
@@ -9,7 +9,7 @@ export const load: import("./$types").PageServerLoad = async ({
   setHeaders,
   fetch,
 }) => {
-  const convertedRepo = projectToRepo.get(project);
+  const convertedRepo = configuration.openGrokProjectMappings.get(project);
 
   const result = await listRepositories(
     {

src/routes/(opengrok-compat)/raw/[project]/[...file]/+page.server.ts

@@ -1,5 +1,5 @@
 import { escapeRegExp } from "$lib/regexp";
-import { projectToRepo } from "$lib/server/opengrok-compat";
+import { configuration } from "$lib/server/configuration";
 import { listRepositories } from "$lib/server/zoekt-list-repositories";
 import { error, redirect } from "@sveltejs/kit";
 
@@ -14,7 +14,7 @@ export const load: import("./$types").PageServerLoad = async ({
     throw error(404);
   }
   const revision = url.searchParams.get("r");
-  const convertedRepo = projectToRepo.get(project);
+  const convertedRepo = configuration.openGrokProjectMappings.get(project);
 
   const result = await listRepositories(
     {

src/routes/(opengrok-compat)/search/+page.server.ts

@@ -5,7 +5,7 @@ import {
 } from "./opengrok-lucene.server";
 import { redirect } from "@sveltejs/kit";
 import { listRepositories } from "$lib/server/zoekt-list-repositories";
-import { projectToRepo } from "$lib/server/opengrok-compat";
+import { configuration } from "$lib/server/configuration";
 
 export const load: import("./$types").PageServerLoad = async ({
   url,
@@ -46,7 +46,7 @@ export const load: import("./$types").PageServerLoad = async ({
   };
 
   const { luceneQuery, zoektQuery, warnings } = await toZoekt(params, {
-    projectToRepo,
+    projectToRepo: configuration.openGrokProjectMappings,
     queryUnknownRepos,
   });
 

src/routes/(opengrok-compat)/xref/[project]/[...file]/+page.server.ts

@@ -1,5 +1,5 @@
 import { escapeRegExp } from "$lib/regexp";
-import { projectToRepo } from "$lib/server/opengrok-compat";
+import { configuration } from "$lib/server/configuration";
 import { listRepositories } from "$lib/server/zoekt-list-repositories";
 import { redirect } from "@sveltejs/kit";
 
@@ -11,7 +11,7 @@ export const load: import("./$types").PageServerLoad = async ({
   fetch,
 }) => {
   const revision = url.searchParams.get("r");
-  const convertedRepo = projectToRepo.get(project);
+  const convertedRepo = configuration.openGrokProjectMappings.get(project);
 
   const result = await listRepositories(
     {