/**
 * Modal Manager for LiveComponents
 * 
 * Manages modal stack using native <dialog> element with showModal().
 * 
 * Native <dialog> Features:
 * - Automatic backdrop/overlay (::backdrop pseudo-element)
 * - Automatic focus management (focus trapping)
 * - Automatic ESC handling (cancel event)
 * - Native modal semantics (blocks background interaction)
 * - Better accessibility (ARIA attributes)
 * 
 * Browser Support:
 * - Chrome 37+ (2014)
 * - Firefox 98+ (2022)
 * - Safari 15.4+ (2022)
 */

export class ModalManager {
    constructor() {
        this.modalStack = []; // Array of { componentId, dialogElement, zIndex, closeOnEscape, closeOnBackdrop }
        this.baseZIndex = 1050; // Bootstrap modal default
        this.zIndexIncrement = 10;
    }

    /**
     * Open modal using native <dialog> element
     * @param {string} componentId - Component ID
     * @param {Object} options - Modal options
     * @returns {Object} Modal instance with dialog element
     */
    open(componentId, options = {}) {
        const {
            title = '',
            content = '',
            size = 'medium',
            buttons = [],
            closeOnBackdrop = true,
            closeOnEscape = true
        } = options;

        // Calculate z-index for stacking
        const zIndex = this.baseZIndex + (this.modalStack.length * this.zIndexIncrement);

        // Create native <dialog> element
        const dialog = document.createElement('dialog');
        dialog.className = `livecomponent-modal livecomponent-modal--${size}`;
        dialog.id = `modal-${componentId}`;
        dialog.style.zIndex = zIndex.toString();

        // Set content
        dialog.innerHTML = this.createModalContent(title, content, buttons);

        // Add to DOM
        document.body.appendChild(dialog);

        // Setup event handlers BEFORE showing modal
        this.setupDialogHandlers(dialog, componentId, closeOnBackdrop, closeOnEscape, buttons);

        // Show modal using native showModal() - this blocks background interaction
        dialog.showModal();

        // Track in stack
        const stackItem = {
            componentId,
            dialogElement: dialog,
            zIndex,
            closeOnEscape,
            closeOnBackdrop
        };
        this.modalStack.push(stackItem);

        // Focus management (native <dialog> handles focus trapping, but we set initial focus)
        this.focusModal(dialog);

        // Return wrapper object for compatibility
        return {
            dialog: dialog,
            close: () => this.close(componentId),
            isOpen: () => dialog.open
        };
    }

    /**
     * Setup event handlers for dialog element
     * @param {HTMLDialogElement} dialog - Dialog element
     * @param {string} componentId - Component ID
     * @param {boolean} closeOnBackdrop - Whether to close on backdrop click
     * @param {boolean} closeOnEscape - Whether to close on ESC key
     * @param {Array} buttons - Button configurations
     */
    setupDialogHandlers(dialog, componentId, closeOnBackdrop, closeOnEscape, buttons) {
        // Native cancel event (triggered by ESC key)
        dialog.addEventListener('cancel', (e) => {
            e.preventDefault();
            if (closeOnEscape) {
                this.close(componentId);
            }
        });

        // Backdrop click handling
        // Note: Native <dialog> doesn't have built-in backdrop click handling
        // We need to check if click target is the dialog element itself (backdrop)
        if (closeOnBackdrop) {
            dialog.addEventListener('click', (e) => {
                // If click target is the dialog element itself (not its children), it's a backdrop click
                if (e.target === dialog) {
                    this.close(componentId);
                }
            });
        }

        // Close button
        const closeBtn = dialog.querySelector('.modal-close');
        if (closeBtn) {
            closeBtn.addEventListener('click', () => {
                this.close(componentId);
            });
        }

        // Button actions
        dialog.querySelectorAll('[data-modal-action]').forEach((btn, index) => {
            btn.addEventListener('click', () => {
                const buttonConfig = buttons[index];
                if (buttonConfig && buttonConfig.action) {
                    // Trigger action if specified
                    if (buttonConfig.action === 'close') {
                        this.close(componentId);
                    }
                }
            });
        });
    }

    /**
     * Close modal and remove from stack
     * @param {string} componentId - Component ID
     */
    close(componentId) {
        const index = this.modalStack.findIndex(item => item.componentId === componentId);
        if (index === -1) {
            return;
        }

        const { dialogElement } = this.modalStack[index];

        // Close dialog using native close() method
        if (dialogElement && dialogElement.open) {
            dialogElement.close();
        }

        // Remove from DOM
        if (dialogElement.parentNode) {
            dialogElement.parentNode.removeChild(dialogElement);
        }

        // Remove from stack
        this.modalStack.splice(index, 1);

        // Focus previous modal or return focus to body
        if (this.modalStack.length > 0) {
            const previousModal = this.modalStack[this.modalStack.length - 1];
            this.focusModal(previousModal.dialogElement);
        } else {
            // Return focus to previously focused element or body
            // Native <dialog> handles this automatically, but we ensure it
            const activeElement = document.activeElement;
            if (activeElement && activeElement !== document.body) {
                activeElement.blur();
            }
            document.body.focus();
        }
    }

    /**
     * Close all modals
     */
    closeAll() {
        while (this.modalStack.length > 0) {
            const { componentId } = this.modalStack[this.modalStack.length - 1];
            this.close(componentId);
        }
    }

    /**
     * Get topmost modal
     * @returns {Object|null}
     */
    getTopModal() {
        if (this.modalStack.length === 0) {
            return null;
        }
        return this.modalStack[this.modalStack.length - 1];
    }

    /**
     * Check if modal is open
     * @param {string} componentId - Component ID
     * @returns {boolean}
     */
    isOpen(componentId) {
        return this.modalStack.some(item => item.componentId === componentId);
    }

    /**
     * Focus modal element
     * Native <dialog> handles focus trapping automatically, but we set initial focus
     * @param {HTMLDialogElement} dialog - Dialog element
     */
    focusModal(dialog) {
        if (!dialog) {
            return;
        }

        // Find first focusable element
        const focusableSelectors = [
            'button:not([disabled])',
            '[href]',
            'input:not([disabled])',
            'select:not([disabled])',
            'textarea:not([disabled])',
            '[tabindex]:not([tabindex="-1"])'
        ].join(', ');

        const focusableElement = dialog.querySelector(focusableSelectors);
        if (focusableElement) {
            // Small delay to ensure dialog is fully rendered
            requestAnimationFrame(() => {
                focusableElement.focus();
            });
        } else {
            // Fallback: focus dialog itself
            requestAnimationFrame(() => {
                dialog.focus();
            });
        }
    }

    /**
     * Create modal content HTML
     * @param {string} title - Modal title
     * @param {string} content - Modal content
     * @param {Array} buttons - Button configurations
     * @returns {string}
     */
    createModalContent(title, content, buttons) {
        const buttonsHtml = buttons.map((btn, index) => {
            const btnClass = btn.class || btn.className || 'btn-secondary';
            return `<button class="btn ${btnClass}" data-modal-action="${index}">${btn.text || 'Button'}</button>`;
        }).join('');

        return `
            <div class="livecomponent-modal-content">
                ${title ? `<div class="modal-header">
                    <h3 class="modal-title">${title}</h3>
                    <button class="modal-close" aria-label="Close">×</button>
                </div>` : ''}
                <div class="modal-body">${content}</div>
                ${buttons.length > 0 ? `<div class="modal-footer">${buttonsHtml}</div>` : ''}
            </div>
        `;
    }

    /**
     * Cleanup all modals
     */
    destroy() {
        this.closeAll();
    }
}