add missing src/base-transition.mjs from template

src/base-transition.mjs

@@ -0,0 +1,88 @@
+/**
+ *
+ */
+export class BaseTransition {
+  /**
+   * Deliver url search params form the current location.
+   * @return {URLSearchParams} as extracted from the path
+   */
+  get searchParams() {
+    const path = this.path;
+    const i = path.indexOf("?");
+    return new URLSearchParams(i >= 0 ? path.substring(i + 1) : undefined);
+  }
+
+  /**
+   * Replaces the search part of the path with the given searchParams.
+   * @param {URLSearchParams|Object} searchParams
+   */
+  set searchParams(searchParams) {
+    let path = this.path;
+    const i = path.indexOf("?");
+
+    if (i >= 0) {
+      path = path.substring(0, i);
+    }
+
+    const sp = (
+      searchParams instanceof URLSearchParams
+        ? searchParams
+        : new URLSearchParams(
+            Object.fromEntries(
+              Object.entries(searchParams).filter(([k, v]) => v?.length > 0)
+            )
+          )
+    ).toString();
+
+    this.path = sp.length > 0 ? `${path}?${sp}` : path;
+  }
+
+  /**
+   * Add another transition nesting level.
+   * Starts a transition from the given factory.
+   * @param {string} path
+   * @param {Transition} factory
+   */
+  async nest(path, factory) {
+    if (this.nested) {
+      await this.nested.abort();
+    }
+    this.nested = new factory(this, path);
+    return this.nested.start();
+  }
+
+  async start() {}
+
+  /**
+   * Continue a nested route to its original destination.
+   * Does nothing if the transition has not been nested.
+   */
+  async continue() {
+    if (this.nested !== undefined) {
+      await this.nested.continue();
+      this.nested = undefined;
+      return true;
+    }
+
+    return false;
+  }
+
+  /**
+   * Abort the transition.
+   * @param error
+   * @return {Promise<boolean>} truen in case there was a nesten transition
+   */
+  async abort(error) {
+    if (error) {
+      console.error(error);
+    }
+
+    if (this.nested !== undefined) {
+      await this.nested.abort(error);
+      this.nested = undefined;
+      return true;
+    }
+
+    return false;
+  }
+}