// ============================================================================
// Stylescape | Cookie Consent Manager
// ============================================================================
// GDPR-compliant cookie consent management with granular category control.
// Supports data-ss-cookie-consent attributes for declarative configuration.
// ============================================================================

/**
 * Cookie categories for granular consent
 */
export type CookieCategory =
    | "necessary"
    | "analytics"
    | "marketing"
    | "preferences";

/**
 * Consent state for all categories
 */
export interface ConsentState {
    necessary: boolean;
    analytics: boolean;
    marketing: boolean;
    preferences: boolean;
    timestamp?: number;
}

/**
 * Configuration options for CookieConsentManager
 */
export interface CookieConsentOptions {
    /** Main message text */
    message?: string;
    /** Accept all button text */
    acceptAllText?: string;
    /** Accept necessary only button text */
    acceptNecessaryText?: string;
    /** Settings button text */
    settingsText?: string;
    /** CSS class prefix */
    cssClass?: string;
    /** Storage key */
    storageKey?: string;
    /** Position on screen */
    position?: "top" | "bottom" | "center";
    /** Cookie categories to show */
    categories?: CookieCategory[];
    /** Link to privacy policy */
    privacyPolicyUrl?: string;
    /** Days until consent expires */
    expirationDays?: number;
    /** Callback when consent is given */
    onAccept?: (consent: ConsentState) => void;
    /** Callback when consent changes */
    onChange?: (consent: ConsentState) => void;
    /** Auto-show banner if no consent */
    autoShow?: boolean;
    /** Show detailed settings panel */
    showSettings?: boolean;
}

/**
 * GDPR-compliant cookie consent manager with category support.
 *
 * @example JavaScript
 * ```typescript
 * const consent = new CookieConsentManager({
 *     categories: ["necessary", "analytics", "marketing"],
 *     onAccept: (state) => {
 *         if (state.analytics) initAnalytics()
 *         if (state.marketing) initMarketing()
 *     }
 * })
 * ```
 *
 * @example HTML with data-ss
 * ```html
 * <div data-ss="cookie-consent"
 *      data-ss-cookie-position="bottom"
 *      data-ss-cookie-privacy-url="/privacy">
 * </div>
 *
 * <!-- Or use in scripts -->
 * <script data-ss-cookie-category="analytics" src="analytics.js"></script>
 * ```
 */
export class CookieConsentManager {
    private options: Required<
        Omit<CookieConsentOptions, "onAccept" | "onChange">
    > &
        Pick<CookieConsentOptions, "onAccept" | "onChange">;
    private bannerElement: HTMLElement | null = null;
    private settingsPanel: HTMLElement | null = null;
    private consentState: ConsentState;

    constructor(options: CookieConsentOptions = {}) {
        this.options = {
            message:
                options.message ??
                "We use cookies to enhance your experience. By continuing to visit this site you agree to our use of cookies.",
            acceptAllText: options.acceptAllText ?? "Accept All",
            acceptNecessaryText:
                options.acceptNecessaryText ?? "Necessary Only",
            settingsText: options.settingsText ?? "Cookie Settings",
            cssClass: options.cssClass ?? "ss-cookie-consent",
            storageKey: options.storageKey ?? "ss-cookie-consent",
            position: options.position ?? "bottom",
            categories: options.categories ?? [
                "necessary",
                "analytics",
                "marketing",
                "preferences",
            ],
            privacyPolicyUrl: options.privacyPolicyUrl ?? "",
            expirationDays: options.expirationDays ?? 365,
            onAccept: options.onAccept,
            onChange: options.onChange,
            autoShow: options.autoShow ?? true,
            showSettings: options.showSettings ?? true,
        };

        // Load existing consent or set defaults
        this.consentState = this.loadConsent() ?? {
            necessary: true, // Always required
            analytics: false,
            marketing: false,
            preferences: false,
        };

        if (this.options.autoShow && !this.hasConsent()) {
            this.show();
        }
    }

    // ========================================================================
    // Public Methods
    // ========================================================================

    /**
     * Check if user has given consent
     */
    public hasConsent(): boolean {
        return this.loadConsent() !== null;
    }

    /**
     * Get current consent state
     */
    public getConsent(): ConsentState {
        return { ...this.consentState };
    }

    /**
     * Check if a specific category is allowed
     */
    public isAllowed(category: CookieCategory): boolean {
        return this.consentState[category] ?? false;
    }

    /**
     * Accept all cookies
     */
    public acceptAll(): void {
        this.consentState = {
            necessary: true,
            analytics: true,
            marketing: true,
            preferences: true,
            timestamp: Date.now(),
        };
        this.saveConsent();
        this.hide();
        this.options.onAccept?.(this.consentState);
        this.activateCategoryScripts();
    }

    /**
     * Accept only necessary cookies
     */
    public acceptNecessary(): void {
        this.consentState = {
            necessary: true,
            analytics: false,
            marketing: false,
            preferences: false,
            timestamp: Date.now(),
        };
        this.saveConsent();
        this.hide();
        this.options.onAccept?.(this.consentState);
    }

    /**
     * Save custom consent selection
     */
    public saveCustomConsent(consent: Partial<ConsentState>): void {
        this.consentState = {
            necessary: true, // Always required
            analytics: consent.analytics ?? false,
            marketing: consent.marketing ?? false,
            preferences: consent.preferences ?? false,
            timestamp: Date.now(),
        };
        this.saveConsent();
        this.hide();
        this.options.onAccept?.(this.consentState);
        this.options.onChange?.(this.consentState);
        this.activateCategoryScripts();
    }

    /**
     * Revoke consent and show banner again
     */
    public revokeConsent(): void {
        localStorage.removeItem(this.options.storageKey);
        this.consentState = {
            necessary: true,
            analytics: false,
            marketing: false,
            preferences: false,
        };
        this.show();
    }

    /**
     * Show the consent banner
     */
    public show(): void {
        if (this.bannerElement) {
            this.bannerElement.style.display = "block";
            return;
        }

        this.createBanner();
    }

    /**
     * Hide the consent banner
     */
    public hide(): void {
        if (this.bannerElement) {
            this.bannerElement.style.display = "none";
        }
        this.hideSettings();
    }

    /**
     * Show settings panel
     */
    public showSettings(): void {
        if (!this.settingsPanel) {
            this.createSettingsPanel();
        }
        if (this.settingsPanel) {
            this.settingsPanel.style.display = "block";
        }
    }

    /**
     * Hide settings panel
     */
    public hideSettings(): void {
        if (this.settingsPanel) {
            this.settingsPanel.style.display = "none";
        }
    }

    /**
     * Destroy the manager and remove elements
     */
    public destroy(): void {
        this.bannerElement?.remove();
        this.settingsPanel?.remove();
        this.bannerElement = null;
        this.settingsPanel = null;
    }

    // ========================================================================
    // Static Factory
    // ========================================================================

    /**
     * Initialize from data-ss="cookie-consent" element
     */
    public static init(): CookieConsentManager | null {
        const element = document.querySelector<HTMLElement>(
            '[data-ss="cookie-consent"]',
        );

        if (!element) {
            return new CookieConsentManager();
        }

        return new CookieConsentManager({
            message: element.dataset.ssCookieMessage,
            position: element.dataset.ssCookiePosition as
                | "top"
                | "bottom"
                | "center",
            privacyPolicyUrl: element.dataset.ssCookiePrivacyUrl,
            cssClass: element.dataset.ssCookieClass,
            showSettings: element.dataset.ssCookieShowSettings !== "false",
        });
    }

    // ========================================================================
    // Private Methods
    // ========================================================================

    private loadConsent(): ConsentState | null {
        try {
            const stored = localStorage.getItem(this.options.storageKey);
            if (!stored) return null;

            const consent = JSON.parse(stored) as ConsentState;

            // Check expiration
            if (consent.timestamp) {
                const expirationMs =
                    this.options.expirationDays * 24 * 60 * 60 * 1000;
                if (Date.now() - consent.timestamp > expirationMs) {
                    localStorage.removeItem(this.options.storageKey);
                    return null;
                }
            }

            return consent;
        } catch {
            return null;
        }
    }

    private saveConsent(): void {
        localStorage.setItem(
            this.options.storageKey,
            JSON.stringify(this.consentState),
        );
    }

    private createBanner(): void {
        const banner = document.createElement("div");
        banner.className = `${this.options.cssClass} ${this.options.cssClass}--${this.options.position}`;
        banner.setAttribute("role", "dialog");
        banner.setAttribute("aria-label", "Cookie Consent");
        banner.setAttribute(
            "aria-describedby",
            `${this.options.cssClass}-message`,
        );

        const privacyLink = this.options.privacyPolicyUrl
            ? `<a href="${this.options.privacyPolicyUrl}" class="${this.options.cssClass}__link">Privacy Policy</a>`
            : "";

        banner.innerHTML = `
            <div class="${this.options.cssClass}__content">
                <p id="${this.options.cssClass}-message" class="${this.options.cssClass}__message">
                    ${this.options.message}
                    ${privacyLink}
                </p>
                <div class="${this.options.cssClass}__actions">
                    ${
                        this.options.showSettings
                            ? `<button type="button" class="${this.options.cssClass}__button ${this.options.cssClass}__button--settings">
                               ${this.options.settingsText}
                           </button>`
                            : ""
                    }
                    <button type="button" class="${this.options.cssClass}__button ${this.options.cssClass}__button--necessary">
                        ${this.options.acceptNecessaryText}
                    </button>
                    <button type="button" class="${this.options.cssClass}__button ${this.options.cssClass}__button--accept">
                        ${this.options.acceptAllText}
                    </button>
                </div>
            </div>
        `;

        document.body.appendChild(banner);
        this.bannerElement = banner;

        // Add event listeners
        banner
            .querySelector(`.${this.options.cssClass}__button--accept`)
            ?.addEventListener("click", () => this.acceptAll());
        banner
            .querySelector(`.${this.options.cssClass}__button--necessary`)
            ?.addEventListener("click", () => this.acceptNecessary());
        banner
            .querySelector(`.${this.options.cssClass}__button--settings`)
            ?.addEventListener("click", () => this.showSettings());
    }

    private createSettingsPanel(): void {
        const panel = document.createElement("div");
        panel.className = `${this.options.cssClass}-settings`;
        panel.setAttribute("role", "dialog");
        panel.setAttribute("aria-label", "Cookie Settings");

        const categoryLabels: Record<
            CookieCategory,
            { title: string; description: string }
        > = {
            necessary: {
                title: "Necessary Cookies",
                description:
                    "Required for the website to function properly. Cannot be disabled.",
            },
            analytics: {
                title: "Analytics Cookies",
                description:
                    "Help us understand how visitors interact with our website.",
            },
            marketing: {
                title: "Marketing Cookies",
                description:
                    "Used to track visitors across websites for advertising purposes.",
            },
            preferences: {
                title: "Preference Cookies",
                description: "Allow the website to remember choices you make.",
            },
        };

        const categoriesHtml = this.options.categories
            .map((cat) => {
                const info = categoryLabels[cat];
                const isNecessary = cat === "necessary";
                const isChecked = this.consentState[cat];

                return `
                <div class="${this.options.cssClass}-settings__category">
                    <label class="${this.options.cssClass}-settings__label">
                        <input type="checkbox"
                               name="${cat}"
                               ${isChecked ? "checked" : ""}
                               ${isNecessary ? "disabled" : ""}>
                        <span class="${this.options.cssClass}-settings__title">${info.title}</span>
                    </label>
                    <p class="${this.options.cssClass}-settings__description">${info.description}</p>
                </div>
            `;
            })
            .join("");

        panel.innerHTML = `
            <div class="${this.options.cssClass}-settings__overlay"></div>
            <div class="${this.options.cssClass}-settings__panel">
                <h2 class="${this.options.cssClass}-settings__heading">Cookie Settings</h2>
                <div class="${this.options.cssClass}-settings__categories">
                    ${categoriesHtml}
                </div>
                <div class="${this.options.cssClass}-settings__actions">
                    <button type="button" class="${this.options.cssClass}-settings__button--cancel">Cancel</button>
                    <button type="button" class="${this.options.cssClass}-settings__button--save">Save Preferences</button>
                </div>
            </div>
        `;

        document.body.appendChild(panel);
        this.settingsPanel = panel;

        // Event listeners
        panel
            .querySelector(
                `.${this.options.cssClass}-settings__button--cancel`,
            )
            ?.addEventListener("click", () => this.hideSettings());
        panel
            .querySelector(`.${this.options.cssClass}-settings__overlay`)
            ?.addEventListener("click", () => this.hideSettings());
        panel
            .querySelector(`.${this.options.cssClass}-settings__button--save`)
            ?.addEventListener("click", () => this.saveFromSettings());
    }

    private saveFromSettings(): void {
        if (!this.settingsPanel) return;

        const checkboxes =
            this.settingsPanel.querySelectorAll<HTMLInputElement>(
                "input[type='checkbox']",
            );
        const consent: Partial<ConsentState> = { necessary: true };

        checkboxes.forEach((checkbox) => {
            const category = checkbox.name as CookieCategory;
            consent[category] = checkbox.checked;
        });

        this.saveCustomConsent(consent);
    }

    private activateCategoryScripts(): void {
        // Activate scripts based on consent
        document
            .querySelectorAll<HTMLScriptElement>(
                "script[data-ss-cookie-category]",
            )
            .forEach((script) => {
                const category = script.dataset
                    .ssCookieCategory as CookieCategory;
                if (
                    this.isAllowed(category) &&
                    !script.dataset.ssCookieActivated
                ) {
                    const newScript = document.createElement("script");
                    newScript.src = script.src;
                    newScript.dataset.ssCookieActivated = "true";
                    document.head.appendChild(newScript);
                }
            });
    }
}

export default CookieConsentManager;