import { Platform, useWindowDimensions } from "react-native";
import { useSafeAreaFrame, useSafeAreaInsets } from "react-native-safe-area-context";

import { spacing } from "@/constants/theme";

/** Standard UITabBar content height (home indicator is separate). */
const IOS_TAB_BAR_HEIGHT = 49;

/** Trim extra inset so scroll content sits closer to the tab bar. */
const TAB_BAR_PADDING_TRIM = spacing.lg;

/**
 * Pixels between the bottom of the safe-area layout frame and the window bottom.
 */
function useBelowLayoutFrame(): number {
  const { height: windowHeight } = useWindowDimensions();
  const frame = useSafeAreaFrame();

  return Math.max(0, windowHeight - frame.y - frame.height);
}

/** Native tab bar height excluding the home-indicator inset. */
export function useNativeTabBarHeight(): number {
  const belowLayoutFrame = useBelowLayoutFrame();
  const { bottom: homeIndicator } = useSafeAreaInsets();
  const measured = Math.max(0, belowLayoutFrame - homeIndicator);

  if (measured > 0) return measured;
  return Platform.OS === "ios" ? IOS_TAB_BAR_HEIGHT : 0;
}

/**
 * Bottom padding so scroll content can clear the floating native tab bar.
 * Uses tab bar + home indicator as the target — layout-frame measurement can
 * over-report and leave a large empty scroll gap above the tab bar.
 */
export function useTabBarScrollPadding(): number {
  const { bottom: homeIndicator } = useSafeAreaInsets();
  const tabBar = useNativeTabBarHeight();
  const clearance = tabBar + homeIndicator;

  return Math.max(spacing.xs, clearance - TAB_BAR_PADDING_TRIM);
}

/** Bottom offset for floating action buttons above the tab bar. */
export function useFloatingActionBottom(): number {
  const { bottom: homeIndicator } = useSafeAreaInsets();
  const tabBar = useNativeTabBarHeight();

  return tabBar + homeIndicator + spacing.xs;
}

/** @deprecated Use useTabBarScrollPadding */
export function useTabBarInset() {
  return useTabBarScrollPadding();
}