/**
 * VideoKonverter TV - Focus-Manager und Navigation
 * D-Pad Navigation fuer TV-Fernbedienungen (Samsung Tizen, Android TV)
 * + Lazy-Loading fuer Poster-Bilder
 */

// === Focus-Manager ===

class FocusManager {
    constructor() {
        this._enabled = true;
        this._currentFocus = null;

        // Tastatur-Events abfangen
        document.addEventListener("keydown", (e) => this._onKeyDown(e));

        // Initiales Focus-Element setzen
        requestAnimationFrame(() => this._initFocus());
    }

    _initFocus() {
        // Erstes fokussierbares Element finden (nicht autofocus Inputs)
        const autofocusEl = document.querySelector("[autofocus]");
        if (autofocusEl) {
            autofocusEl.focus();
            return;
        }
        const first = document.querySelector("[data-focusable]");
        if (first) first.focus();
    }

    _onKeyDown(e) {
        if (!this._enabled) return;

        // Samsung Tizen Remote Key-Codes mappen
        const keyMap = {
            37: "ArrowLeft", 38: "ArrowUp", 39: "ArrowRight", 40: "ArrowDown",
            13: "Enter", 27: "Escape", 8: "Backspace",
            // Samsung Tizen spezifisch
            10009: "Escape",   // RETURN-Taste
            10182: "Escape",   // EXIT-Taste
        };
        const key = keyMap[e.keyCode] || e.key;

        switch (key) {
            case "ArrowUp":
            case "ArrowDown":
            case "ArrowLeft":
            case "ArrowRight":
                this._navigate(key, e);
                break;
            case "Enter":
                this._activate(e);
                break;
            case "Escape":
            case "Backspace":
                this._goBack(e);
                break;
        }
    }

    _navigate(direction, e) {
        const active = document.activeElement;
        // Input-Felder: Links/Rechts nicht abfangen (Cursor-Navigation)
        if (active && (active.tagName === "INPUT" || active.tagName === "TEXTAREA")) {
            if (direction === "ArrowLeft" || direction === "ArrowRight") return;
        }

        const focusables = this._getFocusableElements();
        if (!focusables.length) return;

        // Aktuelles Element
        const currentIdx = focusables.indexOf(active);
        if (currentIdx === -1) {
            // Kein fokussiertes Element -> erstes waehlen
            focusables[0].focus();
            e.preventDefault();
            return;
        }

        // Naechstes Element in Richtung finden (Nearest-Neighbor)
        const current = active.getBoundingClientRect();
        const cx = current.left + current.width / 2;
        const cy = current.top + current.height / 2;

        let bestEl = null;
        let bestDist = Infinity;

        for (const el of focusables) {
            if (el === active) continue;
            const rect = el.getBoundingClientRect();
            // Element muss sichtbar sein
            if (rect.width === 0 || rect.height === 0) continue;

            const ex = rect.left + rect.width / 2;
            const ey = rect.top + rect.height / 2;

            // Pruefen ob Element in der richtigen Richtung liegt
            const dx = ex - cx;
            const dy = ey - cy;

            let valid = false;
            switch (direction) {
                case "ArrowUp":    valid = dy < -5; break;
                case "ArrowDown":  valid = dy > 5; break;
                case "ArrowLeft":  valid = dx < -5; break;
                case "ArrowRight": valid = dx > 5; break;
            }
            if (!valid) continue;

            // Distanz berechnen (gewichtet: Hauptrichtung weniger, Querrichtung mehr)
            let dist;
            if (direction === "ArrowUp" || direction === "ArrowDown") {
                dist = Math.abs(dy) + Math.abs(dx) * 3;
            } else {
                dist = Math.abs(dx) + Math.abs(dy) * 3;
            }

            if (dist < bestDist) {
                bestDist = dist;
                bestEl = el;
            }
        }

        if (bestEl) {
            bestEl.focus();
            // Ins Sichtfeld scrollen
            bestEl.scrollIntoView({ block: "nearest", inline: "nearest", behavior: "smooth" });
            e.preventDefault();
        }
    }

    _activate(e) {
        const active = document.activeElement;
        if (!active || active === document.body) return;

        // Links, Buttons -> Click ausfuehren
        if (active.tagName === "A" || active.tagName === "BUTTON") {
            // Natuerliches Enter-Verhalten beibehalten
            return;
        }

        // Andere fokussierbare Elemente -> Click simulieren
        if (active.hasAttribute("data-focusable")) {
            active.click();
            e.preventDefault();
        }
    }

    _goBack(e) {
        const active = document.activeElement;
        // In Input-Feldern: Escape = Blur, Backspace = natuerlich
        if (active && active.tagName === "INPUT") {
            if (e.key === "Escape") {
                active.blur();
                e.preventDefault();
            }
            return;
        }

        // Zurueck navigieren
        if (window.history.length > 1) {
            window.history.back();
            e.preventDefault();
        }
    }

    _getFocusableElements() {
        // Alle sichtbaren fokussierbaren Elemente
        const elements = document.querySelectorAll("[data-focusable]");
        return Array.from(elements).filter(el => {
            if (el.offsetParent === null && el.style.position !== "fixed") return false;
            const rect = el.getBoundingClientRect();
            return rect.width > 0 && rect.height > 0;
        });
    }
}

// === Horizontale Scroll-Reihen: Scroll per Pfeiltaste ===

function initRowScroll() {
    document.querySelectorAll(".tv-row").forEach(row => {
        // Maus-Rad horizontal scrollen
        row.addEventListener("wheel", (e) => {
            if (Math.abs(e.deltaY) > Math.abs(e.deltaX)) {
                e.preventDefault();
                row.scrollLeft += e.deltaY;
            }
        }, { passive: false });
    });
}

// === Lazy-Loading fuer Poster (IntersectionObserver) ===

function initLazyLoad() {
    // Browser-natives loading="lazy" wird bereits verwendet
    // Zusaetzlich: Placeholder-Klasse entfernen nach Laden
    document.querySelectorAll("img.tv-card-img").forEach(img => {
        if (img.complete) return;
        img.style.opacity = "0";
        img.style.transition = "opacity 0.3s";
        img.addEventListener("load", () => {
            img.style.opacity = "1";
        }, { once: true });
        img.addEventListener("error", () => {
            // Fehlerhaftes Bild: Placeholder anzeigen
            img.style.display = "none";
            const placeholder = document.createElement("div");
            placeholder.className = "tv-card-placeholder";
            placeholder.textContent = img.alt || "?";
            img.parentNode.insertBefore(placeholder, img);
        }, { once: true });
    });
}

// === Navigation: Aktiven Tab highlighten ===

function initNavHighlight() {
    const path = window.location.pathname;
    document.querySelectorAll(".tv-nav-item").forEach(item => {
        const href = item.getAttribute("href");
        if (href === path || (href !== "/tv/" && path.startsWith(href))) {
            item.classList.add("active");
        }
    });
}

// === Init ===

document.addEventListener("DOMContentLoaded", () => {
    window.focusManager = new FocusManager();
    initRowScroll();
    initLazyLoad();
    initNavHighlight();
});