What is the difference between implicit wait, explicit wait, and fluent wait in Selenium?

// Set ONCE — applies to every findElement() call globally
driver.manage().timeouts().implicitlyWait(Duration.ofSeconds(10));

// Now every findElement() polls the DOM for up to 10s before throwing
driver.findElement(By.id("submit"));  // waits up to 10s

// ⚠️ Problems with implicit wait:
// 1. Makes "element should not be present" tests SLOW (always waits 10s)
// 2. Unpredictable interaction with explicit waits
// 3. Hides performance issues — elements should load fast!

// Wait for a SPECIFIC element to meet a SPECIFIC condition
WebDriverWait wait = new WebDriverWait(driver, Duration.ofSeconds(15));

// Visibility
WebElement btn = wait.until(
    ExpectedConditions.visibilityOfElementLocated(By.id("submit")));

// Clickable
WebElement link = wait.until(
    ExpectedConditions.elementToBeClickable(By.cssSelector("a.nav-link")));

// Text present
wait.until(
    ExpectedConditions.textToBePresentInElementLocated(
        By.id("status"), "Order Confirmed"));

// URL change
wait.until(ExpectedConditions.urlContains("/dashboard"));

// Staleness — wait for old element to go stale (page refresh)
WebElement oldEl = driver.findElement(By.id("result"));
driver.navigate().refresh();
wait.until(ExpectedConditions.stalenessOf(oldEl));

// Alert
wait.until(ExpectedConditions.alertIsPresent());

// Attribute value
wait.until(ExpectedConditions.attributeToBe(By.id("btn"), "disabled", "true"));

// Number of elements
wait.until(ExpectedConditions.numberOfElementsToBe(By.cssSelector(".row"), 5));

// Visibility / Presence
visibilityOfElementLocated(By locator)
presenceOfElementLocated(By locator)         // just in DOM, not visible
visibilityOfAllElementsLocatedBy(By locator) // all visible

// Clickability
elementToBeClickable(By locator)

// Text
textToBePresentInElementLocated(By, String)
textToBePresentInElementValue(By, String)

// URL / Title
urlContains(String fraction)
urlToBe(String exactUrl)
titleContains(String fraction)
titleIs(String exactTitle)

// Other
invisibilityOfElementLocated(By locator)     // wait for element to disappear
alertIsPresent()
frameToBeAvailableAndSwitchToIt(By locator)
stalenessOf(WebElement element)
numberOfElementsToBeMoreThan(By, int)

// FluentWait: custom polling interval + ignored exceptions + custom message
FluentWait<WebDriver> fluentWait = new FluentWait<>(driver)
    .withTimeout(Duration.ofSeconds(20))          // max wait
    .pollingEvery(Duration.ofMillis(500))          // check every 500ms (not 250ms default)
    .ignoring(NoSuchElementException.class)        // don't throw if not found yet
    .ignoring(StaleElementReferenceException.class)
    .withMessage("Button was not clickable after 20s");

WebElement btn = fluentWait.until(driver ->
    driver.findElement(By.id("save-btn")));

// Custom condition with FluentWait
WebElement result = fluentWait.until(driver -> {
    WebElement el = driver.findElement(By.id("status"));
    String text = el.getText();
    return text.equals("Completed") ? el : null;   // return null to keep waiting
});

// ✅ Recommended: Explicit wait per interaction
// ❌ Avoid: Mixing implicit + explicit waits (causes timeout multiplication bugs)
// ❌ Avoid: Thread.sleep() — wastes time, not condition-based