fix(javascript): bind Next page admission to source context

src/application/javascript/JavaScriptNextAppContext.ts

@@ -0,0 +1,74 @@
+import { posix } from "node:path";
+
+import type { JavaScriptArtifactFile } from "../../domain/javascript/javascriptArtifactFiles.js";
+import type { NextAppSourceContext } from "../../domain/javascript/javascriptRoutePaths.js";
+import type { JavaScriptJsonDocuments } from "./JavaScriptJsonDocuments.js";
+
+/** Package declarations and inventoried directories own source-router applicability. */
+export const createJavaScriptNextAppContext = (
+  files: readonly JavaScriptArtifactFile[],
+  documents: JavaScriptJsonDocuments,
+  directories: ReadonlySet<string>,
+): ((
+  file: Pick<JavaScriptArtifactFile, "path" | "container_sha256">,
+) => NextAppSourceContext) => {
+  const packages = new Map(
+    files
+      .filter(({ kind }) => kind === "package-json")
+      .map((file) => [posix.dirname(file.path), file]),
+  );
+  const roots = new Map<JavaScriptArtifactFile, string | null>();
+  return (file) => {
+    for (
+      let directory = posix.dirname(file.path);
+      ;
+      directory = posix.dirname(directory)
+    ) {
+      const manifest = packages.get(directory);
+      if (
+        manifest !== undefined &&
+        manifest.container_sha256 === file.container_sha256
+      ) {
+        const identity = {
+          path: manifest.path,
+          sha256: manifest.sha256,
+          container_sha256: manifest.container_sha256,
+        };
+        const facts = documents.read(manifest);
+        if (facts.status !== "included" || facts.nextDependency !== "declared")
+          return {
+            kind: "unknown",
+            package: identity,
+            reason:
+              "The owning package does not establish a Next dependency for source routing.",
+          };
+        const prefix = directory === "." ? "" : `${directory}/`;
+        const compiled = `${prefix}.next/static/chunks/app`;
+        if (file.path.startsWith(`${compiled}/`))
+          return {
+            kind: "compiled-directory",
+            directory: compiled,
+            package: identity,
+          };
+        let root = roots.get(manifest);
+        if (root === undefined) {
+          root =
+            ["app", "src/app"]
+              .map((candidate) => `${prefix}${candidate}`)
+              .find((candidate) => directories.has(candidate)) ?? null;
+          roots.set(manifest, root);
+        }
+        return root !== null && file.path.startsWith(`${root}/`)
+          ? { kind: "app-directory", directory: root, package: identity }
+          : { kind: "outside-app-directory", package: identity };
+      }
+      if (directory === "." || directory === "/") break;
+    }
+    return {
+      kind: "unknown",
+      package: null,
+      reason:
+        "No owning package declaration establishes a Next App Router source root.",
+    };
+  };
+};