/**
 * ContentsControl - Table of Contents Display Control
 *
 * Provides an interactive table of contents for document navigation.
 * Extracts headings from the document and displays them in a hierarchical
 * structure with clickable links for quick navigation.
 *
 * Features:
 * - Automatic heading extraction from document
 * - Hierarchical display with proper indentation
 * - Clickable navigation links with smooth scrolling
 * - Real-time updates when document structure changes
 * - Search functionality within the table of contents
 *
 * Dependencies:
 * - ControlBase (base control functionality)
 */

/**
 * ContentsControl - Interactive table of contents control
 *
 * Built on the base class architecture for consistency with other panels.
 * Only implements content-specific functionality while inheriting all
 * common panel behavior from ControlBase.
 */
class ContentsControl extends ControlBase {
    constructor() {
        super();

        // Configure for contents functionality
        this.config = {
            icon: '📋',
            title: 'Contents',
            className: 'contents-control',
            defaultContent: 'Loading table of contents...',
            ariaLabel: 'Table of Contents Control',
            position: 'w' // West positioning
        };

        // Contents-specific state
        this.headings = [];
        this.lastScanTime = null;
        this.updateInterval = null;
        this.searchQuery = '';
    }

    /**
     * Generate contents control content (called by base class buildContent)
     */
    generateContent() {
        // Extract headings first
        this.extractHeadings();

        return this.safeOperation(() => {
            if (this.headings.length === 0) {
                return `
                    <div style="text-align: center; color: #666; padding: 2rem 0;">
                        <p>No headings found in document</p>
                        <button onclick="this.closest('.contents-control').contentsControl.refreshContents()"
                                style="padding: 0.5rem 1rem; background: #007bff; color: white; border: none; border-radius: 3px; cursor: pointer; margin-top: 0.5rem;">
                            🔄 Refresh
                        </button>
                    </div>
                `;
            }

            const searchHTML = `
                <div style="margin-bottom: 0.5rem; border-bottom: 1px solid #eee; padding-bottom: 0.5rem;">
                    <input type="text"
                           placeholder="Search headings..."
                           style="width: 100%; padding: 0.25rem; border: 1px solid #ddd; border-radius: 3px; font-size: 0.8rem; box-sizing: border-box; overflow: visible;"
                           onkeyup="this.closest('.contents-control').contentsControl.handleSearch(this.value)">
                </div>
            `;

            const filteredHeadings = this.filterHeadings(this.headings, this.searchQuery);
            const contentsHTML = filteredHeadings.map(heading => {
                const indentLevel = Math.max(0, heading.level - 1);
                const indentPx = indentLevel * 15;

                return `
                    <div class="contents-item"
                         style="margin-bottom: 0.3rem; padding-left: ${indentPx}px; overflow: visible;">
                        <a href="#${heading.id}"
                           onclick="event.preventDefault(); this.closest('.contents-control').contentsControl.navigateToHeading('${heading.id}')"
                           style="display: block; padding: 0.2rem 0; color: #007bff; text-decoration: none; font-size: 0.8rem; line-height: 1.2; overflow: visible;"
                           onmouseover="this.style.backgroundColor='#f8f9fa'"
                           onmouseout="this.style.backgroundColor='transparent'">
                            <span class="heading-level" style="color: #666; margin-right: 0.3rem;">H${heading.level}</span>
                            <span class="heading-text">${heading.text}</span>
                        </a>
                    </div>
                `;
            }).join('');

            const statusHTML = `
                <div style="margin-bottom: 0.5rem; font-size: 0.7rem; color: #666; text-align: center;">
                    Found ${filteredHeadings.length} heading${filteredHeadings.length !== 1 ? 's' : ''}
                </div>
            `;

            const refreshButtonHTML = `
                <div style="border-top: 1px solid #eee; padding-top: 0.5rem; text-align: center; margin-top: 0.5rem;">
                    <button onclick="this.closest('.contents-control').contentsControl.refreshContents()"
                            style="padding: 0.3rem 0.6rem; font-size: 0.7rem; background: #28a745; color: white; border: none; border-radius: 3px; cursor: pointer;">
                        🔄 Refresh Contents
                    </button>
                </div>
            `;

            return `
                ${searchHTML}
                ${statusHTML}
                ${contentsHTML}
                ${refreshButtonHTML}
            `;

        }, 'Error generating contents', 'generateContent');
    }

    /**
     * Extract all headings from the document
     * Creates a hierarchical structure of the document's heading elements
     */
    extractHeadings() {
        return this.safeOperation(() => {
            const headingSelectors = 'h1, h2, h3, h4, h5, h6';
            const headingElements = document.querySelectorAll(headingSelectors);
            const extractedHeadings = [];

            headingElements.forEach((heading, index) => {
                const level = parseInt(heading.tagName.charAt(1));
                const text = heading.textContent.trim();

                // Generate or use existing ID for anchor links
                let id = heading.id;
                if (!id) {
                    id = text.toLowerCase()
                        .replace(/[^\w\s-]/g, '')
                        .replace(/\s+/g, '-')
                        .substring(0, 50);

                    // Ensure uniqueness
                    let counter = 1;
                    let uniqueId = id;
                    while (document.getElementById(uniqueId)) {
                        uniqueId = `${id}-${counter}`;
                        counter++;
                    }

                    heading.id = uniqueId;
                    id = uniqueId;
                }

                extractedHeadings.push({
                    id,
                    text,
                    level,
                    element: heading,
                    index
                });
            });

            this.headings = extractedHeadings;
            this.lastScanTime = Date.now();
            return extractedHeadings;

        }, [], 'extractHeadings');
    }

    /**
     * Filter headings based on search query
     */
    filterHeadings(headings, query) {
        if (!query || query.trim() === '') {
            return headings;
        }

        const normalizedQuery = query.toLowerCase().trim();
        return headings.filter(heading =>
            heading.text.toLowerCase().includes(normalizedQuery)
        );
    }

    /**
     * Navigate to a specific heading with smooth scrolling
     */
    navigateToHeading(headingId) {
        return this.safeOperation(() => {
            const targetElement = document.getElementById(headingId);
            if (targetElement) {
                targetElement.scrollIntoView({
                    behavior: 'smooth',
                    block: 'start'
                });

                // Highlight the target temporarily
                const originalStyle = targetElement.style.backgroundColor;
                targetElement.style.backgroundColor = '#fff3cd';
                targetElement.style.transition = 'background-color 0.3s ease';

                setTimeout(() => {
                    targetElement.style.backgroundColor = originalStyle;
                    setTimeout(() => {
                        targetElement.style.transition = '';
                    }, 300);
                }, 1500);

                return true;
            }
            return false;
        }, false, 'navigateToHeading');
    }

    /**
     * Handle search input
     */
    handleSearch(query) {
        this.searchQuery = query;
        this.buildContent(); // Rebuild content with new filter
    }

    /**
     * Refresh the contents by re-scanning the document
     */
    refreshContents() {
        return this.safeOperation(() => {
            this.extractHeadings();
            this.buildContent(); // Rebuild content with updated headings

            // Show success feedback
            const refreshBtn = this.element?.querySelector('button');
            if (refreshBtn && refreshBtn.textContent.includes('Refresh')) {
                const originalText = refreshBtn.innerHTML;
                refreshBtn.innerHTML = '✅ Updated';
                refreshBtn.style.background = '#28a745';

                setTimeout(() => {
                    refreshBtn.innerHTML = originalText;
                    refreshBtn.style.background = '#28a745';
                }, 1000);
            }
        }, null, 'refreshContents');
    }

    /**
     * Override buildContent to add control reference and auto-refresh
     */
    buildContent() {
        super.buildContent();

        // Store reference to this control for onclick handlers
        if (this.element) {
            this.element.contentsControl = this;
        }

        // Set up auto-refresh for dynamic content
        if (this.updateInterval) {
            clearInterval(this.updateInterval);
        }

        this.updateInterval = setInterval(() => {
            const currentHeadingCount = document.querySelectorAll('h1, h2, h3, h4, h5, h6').length;
            if (currentHeadingCount !== this.headings.length) {
                this.refreshContents();
            }
        }, 5000); // Check every 5 seconds
    }

    /**
     * Clean up resources when control is destroyed
     */
    destroy() {
        if (this.updateInterval) {
            clearInterval(this.updateInterval);
            this.updateInterval = null;
        }
        super.destroy();
    }
}

// Export for module systems or attach to global for direct usage
if (typeof module !== 'undefined' && module.exports) {
    module.exports = ContentsControl;
} else {
    window.ContentsControl = ContentsControl;
}