Add Timeout to Finder (#79)

* add timeout

* clearer variable name

* address feedback

* update docs

README.md

@@ -51,6 +51,7 @@ const selector = finder(event.target, {
   optimizedMinLength: 2,
   threshold: 1000,
   maxNumberOfTries: 10_000,
+  timeoutMs: undefined,
 })
 ```
 
@@ -77,6 +78,10 @@ selectors to check. Default `1000` is good enough in most cases.
 Max number of tries for the optimization. This is a trade-off between
 optimization and efficiency. Default `10_000` is good enough in most cases.
 
+### timeoutMs
+
+Optional timeout in milliseconds. `undefined` (no timeout) by default. If `timeoutMs: 500` is provided, an error will be thrown if selector generation takes more than 500ms.
+
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finder.ts

@@ -20,12 +20,15 @@ export type Options = {
   optimizedMinLength: number
   threshold: number
   maxNumberOfTries: number
+  timeoutMs: number | undefined
 }
 
 let config: Options
 let rootDocument: Document | Element
+let start: Date
 
 export function finder(input: Element, options?: Partial<Options>) {
+  start = new Date()
   if (input.nodeType !== Node.ELEMENT_NODE) {
     throw new Error(`Can't generate CSS selector for non-element node type.`)
   }
@@ -42,6 +45,7 @@ export function finder(input: Element, options?: Partial<Options>) {
     optimizedMinLength: 2,
     threshold: 1000,
     maxNumberOfTries: 10000,
+    timeoutMs: undefined,
   }
 
   config = {...defaults, ...options}
@@ -84,6 +88,10 @@ function bottomUpSearch(
   let current: Element | null = input
   let i = 0
   while (current) {
+    const elapsedTime = new Date().getTime() - start.getTime();
+    if (config.timeoutMs !== undefined && elapsedTime > config.timeoutMs) {
+      throw new Error(`Timeout: Can't find a unique selector after ${elapsedTime}ms`)
+    }
     let level: Knot[] = maybe(id(current)) ||
       maybe(...attr(current)) ||
       maybe(...classNames(current)) ||