/**
 * UI Enhancements Module
 * 
 * Provides loading states, optimistic updates, and better error handling
 */

export class UIEnhancements {
    constructor() {
        this.init();
    }

    init() {
        this.setupLoadingStates();
        this.setupOptimisticUpdates();
        this.setupErrorHandling();
        this.setupFormEnhancements();
    }

    /**
     * Setup loading states for async operations
     */
    setupLoadingStates() {
        // Add loading state to buttons
        document.addEventListener('click', (e) => {
            const button = e.target.closest('button[data-loading]');
            if (button && !button.disabled) {
                const originalText = button.textContent;
                button.dataset.originalText = originalText;
                button.disabled = true;
                button.classList.add('loading');
                
                // Add spinner
                const spinner = document.createElement('span');
                spinner.className = 'button-spinner';
                spinner.innerHTML = '⏳';
                button.prepend(spinner);
                button.textContent = button.dataset.loadingText || 'Loading...';
                
                // Auto-reset after 10 seconds (safety)
                setTimeout(() => {
                    this.resetButton(button);
                }, 10000);
            }
        });
    }

    resetButton(button) {
        if (button.dataset.originalText) {
            button.textContent = button.dataset.originalText;
            delete button.dataset.originalText;
        }
        button.disabled = false;
        button.classList.remove('loading');
        const spinner = button.querySelector('.button-spinner');
        if (spinner) {
            spinner.remove();
        }
    }

    /**
     * Setup optimistic updates for better UX
     */
    setupOptimisticUpdates() {
        // Optimistic update helper
        window.optimisticUpdate = (element, updateFn, rollbackFn) => {
            const originalState = this.captureState(element);
            
            try {
                updateFn(element);
                return () => {
                    // Rollback function
                    this.restoreState(element, originalState);
                    if (rollbackFn) rollbackFn();
                };
            } catch (error) {
                console.error('Optimistic update failed:', error);
                return null;
            }
        };

        // Apply optimistic updates to table rows
        document.addEventListener('click', (e) => {
            const row = e.target.closest('tr[data-id]');
            if (!row) return;

            const action = e.target.closest('[data-optimistic]');
            if (!action) return;

            const actionType = action.dataset.optimistic;
            const rollback = this.optimisticTableUpdate(row, actionType);
            
            // Store rollback function
            action.dataset.rollback = 'true';
            action.addEventListener('error', () => {
                if (rollback) rollback();
            }, { once: true });
        });
    }

    optimisticTableUpdate(row, actionType) {
        const originalClass = row.className;
        const originalOpacity = row.style.opacity;

        switch (actionType) {
            case 'delete':
                row.style.opacity = '0.5';
                row.style.textDecoration = 'line-through';
                row.classList.add('optimistic-delete');
                return () => {
                    row.className = originalClass;
                    row.style.opacity = originalOpacity;
                    row.style.textDecoration = '';
                    row.classList.remove('optimistic-delete');
                };
            case 'update':
                row.classList.add('optimistic-update');
                return () => {
                    row.classList.remove('optimistic-update');
                };
            default:
                return null;
        }
    }

    captureState(element) {
        return {
            className: element.className,
            style: element.style.cssText,
            innerHTML: element.innerHTML,
        };
    }

    restoreState(element, state) {
        element.className = state.className;
        element.style.cssText = state.style;
        element.innerHTML = state.innerHTML;
    }

    /**
     * Setup better error handling
     */
    setupErrorHandling() {
        // Global error handler
        window.addEventListener('error', (e) => {
            this.showErrorNotification('An unexpected error occurred', e.error);
        });

        // Unhandled promise rejection handler
        window.addEventListener('unhandledrejection', (e) => {
            this.showErrorNotification('Request failed', e.reason);
        });

        // Enhanced fetch wrapper with error handling
        window.safeFetch = async (url, options = {}) => {
            try {
                const response = await fetch(url, options);
                
                if (!response.ok) {
                    const errorData = await response.json().catch(() => ({ error: 'Unknown error' }));
                    throw new Error(errorData.error || `HTTP ${response.status}: ${response.statusText}`);
                }
                
                return await response.json();
            } catch (error) {
                this.showErrorNotification('Request failed', error.message);
                throw error;
            }
        };
    }

    showErrorNotification(title, message) {
        // Use existing toast system if available
        if (window.Toast) {
            window.Toast.error(`${title}: ${message}`);
        } else {
            // Fallback: console error
            console.error(title, message);
            
            // Show simple alert as last resort
            const errorDiv = document.createElement('div');
            errorDiv.className = 'error-notification';
            errorDiv.innerHTML = `
                <strong>${title}</strong>
                <p>${message}</p>
                <button onclick="this.parentElement.remove()">Close</button>
            `;
            document.body.appendChild(errorDiv);
            
            setTimeout(() => {
                if (errorDiv.parentNode) {
                    errorDiv.remove();
                }
            }, 5000);
        }
    }

    /**
     * Setup form enhancements
     */
    setupFormEnhancements() {
        // Add loading state to forms
        document.addEventListener('submit', (e) => {
            const form = e.target;
            if (form.tagName !== 'FORM') return;

            const submitButton = form.querySelector('button[type="submit"], input[type="submit"]');
            if (submitButton) {
                submitButton.disabled = true;
                submitButton.classList.add('loading');
                
                // Add loading text
                const originalText = submitButton.value || submitButton.textContent;
                submitButton.dataset.originalText = originalText;
                submitButton.value = submitButton.value ? 'Submitting...' : submitButton.value;
                submitButton.textContent = submitButton.textContent ? 'Submitting...' : submitButton.textContent;
            }

            // Reset on error
            form.addEventListener('error', () => {
                if (submitButton) {
                    submitButton.disabled = false;
                    submitButton.classList.remove('loading');
                    submitButton.value = submitButton.dataset.originalText || submitButton.value;
                    submitButton.textContent = submitButton.dataset.originalText || submitButton.textContent;
                }
            }, { once: true });
        });

        // Add retry functionality for failed requests
        window.retryRequest = async (requestFn, maxRetries = 3, delay = 1000) => {
            let lastError;
            
            for (let i = 0; i < maxRetries; i++) {
                try {
                    return await requestFn();
                } catch (error) {
                    lastError = error;
                    if (i < maxRetries - 1) {
                        await new Promise(resolve => setTimeout(resolve, delay * (i + 1)));
                    }
                }
            }
            
            throw lastError;
        };
    }
}

// Auto-initialize
document.addEventListener('DOMContentLoaded', () => {
    new UIEnhancements();
});