import { debounce } from '$shared/lib/utils';

/**
 * Default debounce delay used when no wait is provided. Picked to feel
 * snappy for typing while still coalescing API-bound side effects.
 */
export const DEFAULT_DEBOUNCE_MS = 300;

/**
 * Creates reactive state with immediate and debounced values.
 *
 * Useful for UI inputs that need instant feedback but debounced logic
 * (e.g., search fields with API calls). The immediate value updates on
 * every change for UI binding, while debounced updates after a delay.
 *
 * @param initialValue - Initial value for both immediate and debounced state
 * @param wait - Delay in milliseconds before updating debounced value (default: 300)
 * @returns Object with immediate/debounced getters, immediate setter, and reset method
 *
 * @example
 * ```svelte
 * <script lang="ts">
 *   const search = createDebouncedState('', 300);
 * </script>
 *
 * <input bind:value={search.immediate} />
 *
 * <p>Typing: {search.immediate}</p>
 * <p>Searching: {search.debounced}</p>
 * ```
 */
export function createDebouncedState<T>(initialValue: T, wait: number = DEFAULT_DEBOUNCE_MS) {
    let immediate = $state(initialValue);
    let debounced = $state(initialValue);

    const updateDebounced = debounce((value: T) => {
        debounced = value;
    }, wait);

    return {
        /**
         * Current value with immediate updates (for UI binding)
         */
        get immediate() {
            return immediate;
        },
        set immediate(value: T) {
            immediate = value;
            // Manually trigger the debounce on write
            updateDebounced(value);
        },
        /**
         * Current value with debounced updates (for logic/operations)
         */
        get debounced() {
            return debounced;
        },
        /**
         * Resets both values to initial or specified value.
         * @param value - Optional value to reset to (defaults to initialValue)
         */
        reset(value?: T) {
            const resetValue = value ?? initialValue;
            immediate = resetValue;
            debounced = resetValue;
        },
    };
}