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frontend-app-api: explain the route info extraction a bit

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Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>
This commit is contained in:
Patrik Oldsberg
2023-10-03 17:58:07 +02:00
parent e92ad1c067
commit 783a6b70e6
1 changed files with 22 additions and 4 deletions
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packages/frontend-app-api/src/routing/extractRouteInfoFromInstanceTree.ts
+22 -4
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@@ -47,8 +47,13 @@ export function extractRouteInfoFromInstanceTree(roots: ExtensionInstance[]): {
routeParents: Map<RouteRef, RouteRef | undefined>;
routeObjects: BackstageRouteObject[];
} {
// This tracks the route path for each route ref, the value is the route path relative to the parent ref
const routePaths = new Map<RouteRef, string>();
// This tracks the parents of each route ref. To find the full path of any route ref you traverse
// upwards in this tree and substitute each route ref for its route path along then way.
const routeParents = new Map<RouteRef, RouteRef | undefined>();
// This route object tree is passed to react-router in order to be able to look up the current route
// ref or extension/source based on our current location.
const routeObjects = new Array<BackstageRouteObject>();
function visit(
@@ -65,11 +70,14 @@ export function extractRouteInfoFromInstanceTree(roots: ExtensionInstance[]): {
const routeRef = current.getData(coreExtensionData.routeRef);
const parentChildren = parentObj?.children ?? routeObjects;
let currentObj = parentObj;
let newCollectedPath = collectedPath;
let newFoundRefForCollectedPath = foundRefForCollectedPath;
let newParentRef = parentRef;
let newCandidateParentRef = candidateParentRef;
// Whenever a route path is encountered, a new node is created in the routing tree.
if (routePath !== undefined) {
currentObj = {
path: routePath,
@@ -79,9 +87,16 @@ export function extractRouteInfoFromInstanceTree(roots: ExtensionInstance[]): {
children: [MATCH_ALL_ROUTE],
plugins: new Set(),
};
parentChildren.push(currentObj);
// Each route path that we discover creates a new node in the routing tree, at that point
// we also switch out our candidate parent ref to be the active one.
newParentRef = candidateParentRef;
newCandidateParentRef = undefined;
// We need to collect and concatenate route paths until the path has been assigned a route ref:
// Once we find a route ref the collection starts over from an empty path, that way each route
// path assignment only contains the diff from the parent ref.
if (newFoundRefForCollectedPath) {
newCollectedPath = routePath;
newFoundRefForCollectedPath = false;
@@ -90,11 +105,9 @@ export function extractRouteInfoFromInstanceTree(roots: ExtensionInstance[]): {
? joinPaths(collectedPath, routePath)
: routePath;
}
newParentRef = candidateParentRef;
newCandidateParentRef = undefined;
}
// Whenever a route ref is encountered, we need to give it a route path and position in the ref tree.
if (routeRef) {
const routeRefId = (routeRef as any).id; // TODO: properly
if (routeRefId !== current.id) {
@@ -103,10 +116,15 @@ export function extractRouteInfoFromInstanceTree(roots: ExtensionInstance[]): {
);
}
// The first route ref we find after encountering a route path is selected to be used as the
// parent ref further down the tree. We don't start using this candidate ref until we encounter
// another route path though, at which point we repeat the process and select another candidate.
if (!newCandidateParentRef) {
newCandidateParentRef = routeRef;
}
// Check if we've encountered any route paths since the closest route ref, in that case we assign
// that path to this and following route refs until we encounter another route path.
if (newCollectedPath !== undefined) {
routePaths.set(routeRef, newCollectedPath);
newFoundRefForCollectedPath = true;