class HistoryManager {
    constructor(app) {
        this.app = app;
        this.history = [];
        this.currentIndex = -1;
        this.maxHistorySize = 50;
        
        // Save initial state
        this.saveState();
    }

    // Save current state to history
    saveState() {
        // Remove any states after current index (when user makes new action after undo)
        this.history = this.history.slice(0, this.currentIndex + 1);
        
        // Create a deep copy of current design elements
        const state = {
            designElements: JSON.parse(JSON.stringify(this.app.designElements)),
            timestamp: Date.now()
        };
        
        this.history.push(state);
        this.currentIndex++;
        
        // Limit history size
        if (this.history.length > this.maxHistorySize) {
            this.history.shift();
            this.currentIndex--;
        }
        
        this.updateButtonStates();
        console.log('State saved. History size:', this.history.length, 'Current index:', this.currentIndex);
    }

    // Undo last action
    undo() {
        if (!this.canUndo()) {
            console.log('Cannot undo - at beginning of history');
            return;
        }
        
        this.currentIndex--;
        this.restoreState(this.history[this.currentIndex]);
        this.updateButtonStates();
        console.log('Undo performed. Current index:', this.currentIndex);
    }

    // Redo last undone action
    redo() {
        if (!this.canRedo()) {
            console.log('Cannot redo - at end of history');
            return;
        }
        
        this.currentIndex++;
        this.restoreState(this.history[this.currentIndex]);
        this.updateButtonStates();
        console.log('Redo performed. Current index:', this.currentIndex);
    }

    // Check if undo is possible
    canUndo() {
        return this.currentIndex > 0;
    }

    // Check if redo is possible
    canRedo() {
        return this.currentIndex < this.history.length - 1;
    }

    // Restore a state from history
    restoreState(state) {
        // Deep copy the state to avoid reference issues
        this.app.designElements = JSON.parse(JSON.stringify(state.designElements));
        
        // Redraw the canvas
        this.app.canvasDrawingManager.redraw();
        
        // Update 3D view if active
        if (this.app.threeJSManager.is3DViewActive()) {
            this.app.viewManager.convertTo3D();
        }
        
        // Clear selection
        this.app.uiManager.clearSelection();
    }

    // Update button states (enabled/disabled)
    updateButtonStates() {
        const undoBtn = document.getElementById('undoBtn');
        const redoBtn = document.getElementById('redoBtn');
        
        if (undoBtn) {
            if (this.canUndo()) {
                undoBtn.disabled = false;
                undoBtn.classList.remove('opacity-50', 'cursor-not-allowed');
                undoBtn.classList.add('hover:bg-gray-200');
            } else {
                undoBtn.disabled = true;
                undoBtn.classList.add('opacity-50', 'cursor-not-allowed');
                undoBtn.classList.remove('hover:bg-gray-200');
            }
        }
        
        if (redoBtn) {
            if (this.canRedo()) {
                redoBtn.disabled = false;
                redoBtn.classList.remove('opacity-50', 'cursor-not-allowed');
                redoBtn.classList.add('hover:bg-gray-200');
            } else {
                redoBtn.disabled = true;
                redoBtn.classList.add('opacity-50', 'cursor-not-allowed');
                redoBtn.classList.remove('hover:bg-gray-200');
            }
        }
    }

    // Clear history (useful for new design)
    clear() {
        this.history = [];
        this.currentIndex = -1;
        this.saveState();
        console.log('History cleared');
    }

    // Get history info for debugging
    getInfo() {
        return {
            historySize: this.history.length,
            currentIndex: this.currentIndex,
            canUndo: this.canUndo(),
            canRedo: this.canRedo()
        };
    }
}