import { executeCallbacks } from "svelte-toolbelt";
import { Previous, watch } from "runed";
import { on } from "svelte/events";
import { StateMachine } from "../../../internal/state-machine.js";
/**
 * Cache for animation names with TTL to reduce getComputedStyle calls.
 * Uses WeakMap to avoid memory leaks when elements are removed.
 */
const animationNameCache = new WeakMap();
const ANIMATION_NAME_CACHE_TTL_MS = 16; // One frame at 60fps
const presenceMachine = {
    mounted: {
        UNMOUNT: "unmounted",
        ANIMATION_OUT: "unmountSuspended",
    },
    unmountSuspended: {
        MOUNT: "mounted",
        ANIMATION_END: "unmounted",
    },
    unmounted: {
        MOUNT: "mounted",
    },
};
export class Presence {
    opts;
    prevAnimationNameState = $state("none");
    styles = $state({ display: "", animationName: "none" });
    initialStatus;
    previousPresent;
    machine;
    present;
    constructor(opts) {
        this.opts = opts;
        this.present = this.opts.open;
        this.initialStatus = opts.open.current ? "mounted" : "unmounted";
        this.previousPresent = new Previous(() => this.present.current);
        this.machine = new StateMachine(this.initialStatus, presenceMachine);
        this.handleAnimationEnd = this.handleAnimationEnd.bind(this);
        this.handleAnimationStart = this.handleAnimationStart.bind(this);
        watchPresenceChange(this);
        watchStatusChange(this);
        watchRefChange(this);
    }
    /**
     * Triggering an ANIMATION_OUT during an ANIMATION_IN will fire an `animationcancel`
     * event for ANIMATION_IN after we have entered `unmountSuspended` state. So, we
     * make sure we only trigger ANIMATION_END for the currently active animation.
     */
    handleAnimationEnd(event) {
        if (!this.opts.ref.current)
            return;
        // Use cached animation name from styles when available to avoid getComputedStyle
        const currAnimationName = this.styles.animationName || getAnimationName(this.opts.ref.current);
        const isCurrentAnimation = currAnimationName.includes(event.animationName) || currAnimationName === "none";
        if (event.target === this.opts.ref.current && isCurrentAnimation) {
            this.machine.dispatch("ANIMATION_END");
        }
    }
    handleAnimationStart(event) {
        if (!this.opts.ref.current)
            return;
        if (event.target === this.opts.ref.current) {
            // Force refresh cache on animation start to get accurate animation name
            const animationName = getAnimationName(this.opts.ref.current, true);
            this.prevAnimationNameState = animationName;
            // Update styles cache for subsequent reads
            this.styles.animationName = animationName;
        }
    }
    isPresent = $derived.by(() => {
        return ["mounted", "unmountSuspended"].includes(this.machine.state.current);
    });
}
function watchPresenceChange(state) {
    watch(() => state.present.current, () => {
        if (!state.opts.ref.current)
            return;
        const hasPresentChanged = state.present.current !== state.previousPresent.current;
        if (!hasPresentChanged)
            return;
        const prevAnimationName = state.prevAnimationNameState;
        // Force refresh on state change to get accurate current animation
        const currAnimationName = getAnimationName(state.opts.ref.current, true);
        // Update styles cache for subsequent reads
        state.styles.animationName = currAnimationName;
        if (state.present.current) {
            state.machine.dispatch("MOUNT");
        }
        else if (currAnimationName === "none" || state.styles.display === "none") {
            // If there is no exit animation or the element is hidden, animations won't run
            // so we unmount instantly
            state.machine.dispatch("UNMOUNT");
        }
        else {
            /**
             * When `present` changes to `false`, we check changes to animation-name to
             * determine whether an animation has started. We chose this approach (reading
             * computed styles) because there is no `animationrun` event and `animationstart`
             * fires after `animation-delay` has expired which would be too late.
             */
            const isAnimating = prevAnimationName !== currAnimationName;
            if (state.previousPresent.current && isAnimating) {
                state.machine.dispatch("ANIMATION_OUT");
            }
            else {
                state.machine.dispatch("UNMOUNT");
            }
        }
    });
}
function watchStatusChange(state) {
    watch(() => state.machine.state.current, () => {
        if (!state.opts.ref.current)
            return;
        // Use cached animation name first, only force refresh if needed for mounted state
        const currAnimationName = state.machine.state.current === "mounted"
            ? getAnimationName(state.opts.ref.current, true)
            : "none";
        state.prevAnimationNameState = currAnimationName;
        // Update styles cache
        state.styles.animationName = currAnimationName;
    });
}
function watchRefChange(state) {
    watch(() => state.opts.ref.current, () => {
        if (!state.opts.ref.current)
            return;
        // Snapshot only needed style properties instead of storing live CSSStyleDeclaration
        // This avoids triggering style recalculations when accessing the cached object
        const computed = getComputedStyle(state.opts.ref.current);
        state.styles = {
            display: computed.display,
            animationName: computed.animationName || "none",
        };
        return executeCallbacks(on(state.opts.ref.current, "animationstart", state.handleAnimationStart), on(state.opts.ref.current, "animationcancel", state.handleAnimationEnd), on(state.opts.ref.current, "animationend", state.handleAnimationEnd));
    });
}
/**
 * Gets the animation name from computed styles with optional caching.
 *
 * @param node - The HTML element to get animation name from
 * @param forceRefresh - If true, bypasses the cache and forces a fresh getComputedStyle call
 * @returns The animation name or "none" if not animating
 */
function getAnimationName(node, forceRefresh = false) {
    if (!node)
        return "none";
    const now = performance.now();
    const cached = animationNameCache.get(node);
    // Return cached value if still valid and not forced to refresh
    if (!forceRefresh && cached && now - cached.timestamp < ANIMATION_NAME_CACHE_TTL_MS) {
        return cached.value;
    }
    // Compute and cache the new value
    const value = getComputedStyle(node).animationName || "none";
    animationNameCache.set(node, { value, timestamp: now });
    return value;
}