Add transitions

1 files changed, 74 insertions, 0 deletions

diff --git a/app/lib/transition-rule.js b/app/lib/transition-rule.js
new file mode 100644
index 0000000000..f0c7020870
--- /dev/null
+++ b/app/lib/transition-rule.js
@@ -0,0 +1,74 @@
+// @flow
+
+export type TransitionDescriptor = {
+  name: string,
+  duration: number
+};
+
+export type TransitionFork = {
+  forward: TransitionDescriptor,
+  backward: TransitionDescriptor
+};
+
+/**
+ * Transition rule
+ *
+ * @class TransitionRule
+ */
+export default class TransitionRule {
+
+  from: ?string;
+  to: string;
+  fork: TransitionFork;
+  dir: 'forward' | 'backward' = 'forward';
+
+  /**
+   * Creates an instance of TransitionRule.
+   * @param {string} from - source route to match against, pass null for any.
+   * @param {string} to - destination route to match against
+   * @param {TransitionFork} fork - transition
+   *
+   * @memberof TransitionRule
+   */
+  constructor(from: ?string, to: string, fork: TransitionFork) {
+    this.from = from;
+    this.to = to;
+    this.fork = fork;
+  }
+
+  /**
+   * Attempts to match the transition between routes A -> B and B -> A
+   *
+   * @param {string} [fromRoute] source route, pass null for any
+   * @param {string} toRoute
+   * @returns {boolean} true if matches, otherwise false
+   *
+   * @memberof TransitionRule
+   */
+  match(fromRoute: ?string, toRoute: string): boolean {
+    if((!this.from || this.from === fromRoute) && this.to === toRoute) {
+      this.dir = 'forward';
+      return true;
+    }
+
+    if((!this.from || this.from === toRoute) && this.to === fromRoute) {
+      this.dir = 'backward';
+      return true;
+    }
+
+    return false;
+  }
+
+  /**
+   * Returns transition descriptor.
+   * Make sure you run match() before to obtain the direction
+   * of transition before calling this method
+   *
+   * @returns {TransitionDescriptor} transitionDescriptor
+   *
+   * @memberof TransitionRule
+   */
+  transitionDescriptor(): TransitionDescriptor {
+    return this.fork[this.dir];
+  }
+}
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