Specify the plugin contract (todo §2); typed manifest + version/conflict rules in src/plugin.ts, authoritative docs/plugin-contract.md

src/plugin.ts

@@ -0,0 +1,159 @@
+// The plugin contract (todo §2) — the product's main API surface. This module is the
+// authoritative, machine-readable shape; `docs/plugin-contract.md` is the prose reference.
+// It only declares types + pure rules; the §2 discovery/router wire them to the filesystem
+// and HTTP. Philosophy: a powerful, predictable, overload-friendly API that fails loud at
+// boot/discovery rather than sandboxing at runtime.
+
+import type { RequestContext } from "./context.ts";
+import type { NavNode } from "./nav.ts";
+
+// Host contract major version. Bump on a breaking manifest/handler change; a plugin pins the
+// version it targets via `apiVersion` and the host refuses/warns on mismatch (checkApiVersion).
+export const HOST_API_VERSION = 1;
+
+export type HttpMethod = "DELETE" | "GET" | "HEAD" | "PATCH" | "POST" | "PUT";
+
+// A handler's return value; the host turns it into the HTTP response. Returning void is the
+// escape hatch — the handler wrote to `ctx.res` itself (streaming, custom headers, etc.).
+export type RouteResult =
+  | { headers?: Record<string, string>; html: string; status?: number }
+  | { headers?: Record<string, string>; json: unknown; status?: number } // for opt-in JS enhancement
+  | { data?: Record<string, unknown>; headers?: Record<string, string>; status?: number; view: string }
+  | { redirect: string; status?: number };
+
+export type RouteHandler = (ctx: RequestContext) => Promise<RouteResult | void> | RouteResult | void;
+
+export interface Route {
+  handler: RouteHandler;
+  method: HttpMethod;
+  path: string; // relative to basePath; ":name" segments become ctx.params.name
+  permission?: string; // coarse gate (a role token); checked before the handler runs
+}
+
+// A permission token this plugin introduces — declared for docs/seeding. Tokens are a shared
+// global namespace (so an operator grants them in Keto); namespace as `<id>:<action>`.
+export interface PermissionDecl {
+  description?: string;
+  token: string;
+}
+
+// Optional hooks on system actions. Crash-isolation is a non-goal — a throwing hook fails loud.
+export interface PluginHooks {
+  onBoot?: () => Promise<void> | void; // after discovery, before the server listens
+  onRequest?: (ctx: RequestContext) => Promise<RouteResult | void> | RouteResult | void; // may short-circuit
+  onResponse?: (ctx: RequestContext, result: RouteResult | null) => Promise<void> | void;
+}
+
+export interface Plugin {
+  apiVersion: number; // host contract version this plugin targets (= HOST_API_VERSION)
+  basePath: string; // unique mount prefix, e.g. "/scheduling"; must not overlap another plugin's
+  hooks?: PluginHooks;
+  id: string; // globally unique; namespaces views, /public/<id>/, and nav/permission tokens
+  nav?: NavNode[]; // fragment merged into the global menu (composeNav); ids must be globally unique
+  permissions?: PermissionDecl[];
+  routes?: Route[];
+}
+
+// Identity helper: types the manifest, returns it unchanged. Validation happens at discovery
+// (§2), so a plugin may equally be a plain typed object. Mirrors Vite's `defineConfig`.
+export function definePlugin(plugin: Plugin): Plugin {
+  return plugin;
+}
+
+export interface VersionCheck {
+  level: "ok" | "refuse" | "warn";
+  message: string;
+}
+
+// The versioning rule: equal → ok; plugin older than host → warn (load, review); plugin newer
+// or not a positive integer → refuse. Discovery maps refuse→throw, warn→log.
+export function checkApiVersion(pluginVersion: unknown, hostVersion: number = HOST_API_VERSION): VersionCheck {
+  if (typeof pluginVersion !== "number" || !Number.isInteger(pluginVersion) || pluginVersion < 1) {
+    return { level: "refuse", message: `apiVersion must be a positive integer; got ${JSON.stringify(pluginVersion)}` };
+  }
+  if (pluginVersion > hostVersion) {
+    return { level: "refuse", message: `plugin targets apiVersion ${pluginVersion} but host is ${hostVersion}; upgrade the host` };
+  }
+  if (pluginVersion < hostVersion) {
+    return { level: "warn", message: `plugin targets apiVersion ${pluginVersion}; host is ${hostVersion} — review for deprecated behaviour` };
+  }
+  return { level: "ok", message: `apiVersion ${pluginVersion}` };
+}
+
+export interface PluginConflict {
+  kind: "basePath" | "id" | "nav-id" | "permission" | "route";
+  level: "error" | "warn";
+  message: string;
+  plugins: string[]; // unique ids involved
+}
+
+// The conflict rules: defined, loud resolution — never last-write-wins. Pure over the discovered
+// manifests; discovery throws on any "error" and logs every "warn". Shared permission tokens are
+// the one intentional overlap, so they warn rather than error.
+export function findConflicts(plugins: Plugin[]): PluginConflict[] {
+  const out: PluginConflict[] = [];
+
+  const idCounts = new Map<string, number>();
+  for (const plugin of plugins) idCounts.set(plugin.id, (idCounts.get(plugin.id) ?? 0) + 1);
+  for (const [id, n] of idCounts) {
+    if (n > 1) out.push({ kind: "id", level: "error", message: `${n} plugins share id "${id}"; ids must be globally unique`, plugins: [id] });
+  }
+
+  for (let i = 0; i < plugins.length; i++) {
+    for (let j = i + 1; j < plugins.length; j++) {
+      const a = plugins[i] as Plugin;
+      const b = plugins[j] as Plugin;
+      if (basePathOverlap(a.basePath, b.basePath)) {
+        out.push({ kind: "basePath", level: "error", message: `basePath "${a.basePath}" (${a.id}) overlaps "${b.basePath}" (${b.id})`, plugins: uniq([a.id, b.id]) });
+      }
+    }
+  }
+
+  collect(plugins, (plugin, push) => {
+    for (const route of plugin.routes ?? []) push(`${route.method} ${joinPath(plugin.basePath, route.path)}`);
+  }).forEach((owners, key) => {
+    if (owners.length > 1) out.push({ kind: "route", level: "error", message: `${owners.length} routes resolve to "${key}"`, plugins: uniq(owners) });
+  });
+
+  collect(plugins, (plugin, push) => collectNavIds(plugin.nav, push)).forEach((owners, id) => {
+    if (owners.length > 1) out.push({ kind: "nav-id", level: "error", message: `nav id "${id}" used ${owners.length}×; override targets ids, so they must be unique`, plugins: uniq(owners) });
+  });
+
+  collect(plugins, (plugin, push) => {
+    for (const decl of plugin.permissions ?? []) push(decl.token);
+  }).forEach((owners, token) => {
+    if (owners.length > 1) out.push({ kind: "permission", level: "warn", message: `permission "${token}" declared by ${uniq(owners).length} plugins; namespace as "<id>:<action>" unless shared on purpose`, plugins: uniq(owners) });
+  });
+
+  return out;
+}
+
+// Map each emitted key → the plugin ids that emitted it (repeats kept, so within-plugin dups count).
+function collect(plugins: Plugin[], emit: (plugin: Plugin, push: (key: string) => void) => void): Map<string, string[]> {
+  const owners = new Map<string, string[]>();
+  for (const plugin of plugins) emit(plugin, (key) => owners.set(key, [...(owners.get(key) ?? []), plugin.id]));
+  return owners;
+}
+
+function collectNavIds(nodes: NavNode[] | undefined, push: (id: string) => void): void {
+  for (const node of nodes ?? []) {
+    if (node.id != null) push(node.id);
+    collectNavIds(node.children, push);
+  }
+}
+
+const trimSlash = (s: string): string => s.replace(/\/+$/, "");
+
+function basePathOverlap(a: string, b: string): boolean {
+  const x = trimSlash(a);
+  const y = trimSlash(b);
+  return x === y || y.startsWith(`${x}/`) || x.startsWith(`${y}/`);
+}
+
+function joinPath(basePath: string, path: string): string {
+  return `${trimSlash(basePath)}${path.startsWith("/") ? path : `/${path}`}`;
+}
+
+function uniq(xs: string[]): string[] {
+  return [...new Set(xs)];
+}