/**
 * GraphPathHighlighter - Highlight đường đi trong đồ thị
 * Tìm và highlight upstream path (từ input đến node) và downstream path (từ node đến output).
 * Làm mờ các node/edge không thuộc đường đi. Xóa highlight khi click vào vùng trống.
 * Requirements: 18.1, 18.2, 18.3, 18.4, 18.5
 */

class GraphPathHighlighter {
    constructor() {
        /** @type {boolean} Whether a path is currently highlighted */
        this._isActive = false;

        /** @type {string|null} The node ID being traced */
        this._tracedNodeId = null;

        /** @type {Function|null} EventBus unsubscribe for path:highlight-requested */
        this._unsubHighlight = null;

        /** @type {Function|null} EventBus unsubscribe for path:cleared */
        this._unsubCleared = null;

        /** @type {Function|null} EventBus unsubscribe for model:loaded */
        this._unsubModelLoaded = null;

        this._bindEvents();
    }

    // ─── Public API ────────────────────────────────────────────────────────────

    /**
     * Highlight the full path (upstream + downstream) through a node.
     * @param {cytoscape.Core} cy - Cytoscape instance
     * @param {string} nodeId - The node to trace paths through
     */
    highlightPath(cy, nodeId) {
        if (!cy || !nodeId) return;

        const node = cy.getElementById(nodeId);
        if (!node || node.length === 0) {
            console.warn('[GraphPathHighlighter] Node not found:', nodeId);
            return;
        }

        // Find upstream and downstream paths
        const upstreamIds = this._findUpstream(cy, nodeId);
        const downstreamIds = this._findDownstream(cy, nodeId);

        console.log('[GraphPathHighlighter] upstream:', upstreamIds.size, 'downstream:', downstreamIds.size, 'total nodes:', cy.nodes().length);

        // Combine all path node IDs (include the selected node itself)
        const pathNodeIds = new Set([...upstreamIds, nodeId, ...downstreamIds]);

        // If no path found at all (isolated node with no connections)
        if (pathNodeIds.size === 1 && upstreamIds.size === 0 && downstreamIds.size === 0) {
            this._showMessage('Không tìm thấy đường đi nào qua node này.');
            return;
        }

        // Collect edges on the path
        const pathEdgeIds = this._findPathEdges(cy, pathNodeIds);

        // Set traced node BEFORE applying highlight so _applyHighlight can use it
        this._isActive = true;
        this._tracedNodeId = nodeId;

        // Apply highlight classes
        this._applyHighlight(cy, pathNodeIds, pathEdgeIds);

        // Emit event
        if (typeof EventBus !== 'undefined') {
            EventBus.emit('path:highlighted', {
                nodeId: nodeId,
                upstreamCount: upstreamIds.size,
                downstreamCount: downstreamIds.size
            });
        }
    }

    /**
     * Clear all path highlighting and restore normal graph appearance.
     * @param {cytoscape.Core} cy - Cytoscape instance
     */
    clearPath(cy) {
        if (!cy) return;

        cy.startBatch();
        cy.elements().removeClass('path-highlighted path-dimmed path-source');
        cy.elements().removeStyle('opacity');
        cy.endBatch();

        this._isActive = false;
        this._tracedNodeId = null;

        if (typeof EventBus !== 'undefined') {
            EventBus.emit('path:cleared', {});
        }
    }

    /**
     * Check if path highlighting is currently active.
     * @returns {boolean}
     */
    isActive() {
        return this._isActive;
    }

    /**
     * Get the currently traced node ID.
     * @returns {string|null}
     */
    getTracedNodeId() {
        return this._tracedNodeId;
    }

    /**
     * Destroy and clean up all resources.
     */
    destroy() {
        if (this._unsubHighlight) {
            this._unsubHighlight();
            this._unsubHighlight = null;
        }
        if (this._unsubCleared) {
            this._unsubCleared();
            this._unsubCleared = null;
        }
        if (this._unsubModelLoaded) {
            this._unsubModelLoaded();
            this._unsubModelLoaded = null;
        }
        this._isActive = false;
        this._tracedNodeId = null;
    }

    // ─── Path Finding ──────────────────────────────────────────────────────────

    /**
     * Find all upstream (ancestor) nodes via BFS backwards from the given node.
     * Traverses incoming edges to find all predecessors up to input nodes.
     * @param {cytoscape.Core} cy
     * @param {string} nodeId
     * @returns {Set<string>} Set of upstream node IDs
     * @private
     */
    _findUpstream(cy, nodeId) {
        const visited = new Set();
        const queue = [nodeId];

        while (queue.length > 0) {
            const currentId = queue.shift();
            const current = cy.getElementById(currentId);
            if (!current || current.length === 0) continue;

            // Get all incoming edges (edges where this node is the target)
            const incomers = current.incomers('node');
            incomers.forEach(function (predecessor) {
                const predId = predecessor.id();
                if (!visited.has(predId)) {
                    visited.add(predId);
                    queue.push(predId);
                }
            });
        }

        return visited;
    }

    /**
     * Find all downstream (descendant) nodes via BFS forward from the given node.
     * Traverses outgoing edges to find all successors down to output nodes.
     * @param {cytoscape.Core} cy
     * @param {string} nodeId
     * @returns {Set<string>} Set of downstream node IDs
     * @private
     */
    _findDownstream(cy, nodeId) {
        const visited = new Set();
        const queue = [nodeId];

        while (queue.length > 0) {
            const currentId = queue.shift();
            const current = cy.getElementById(currentId);
            if (!current || current.length === 0) continue;

            // Get all outgoing edges (edges where this node is the source)
            const outgoers = current.outgoers('node');
            outgoers.forEach(function (successor) {
                const sucId = successor.id();
                if (!visited.has(sucId)) {
                    visited.add(sucId);
                    queue.push(sucId);
                }
            });
        }

        return visited;
    }

    /**
     * Find all edges that connect nodes within the path set.
     * @param {cytoscape.Core} cy
     * @param {Set<string>} pathNodeIds
     * @returns {Set<string>} Set of edge IDs on the path
     * @private
     */
    _findPathEdges(cy, pathNodeIds) {
        const pathEdgeIds = new Set();

        cy.edges().forEach(function (edge) {
            var srcId = edge.source().id();
            var tgtId = edge.target().id();
            if (pathNodeIds.has(srcId) && pathNodeIds.has(tgtId)) {
                pathEdgeIds.add(edge.id());
            }
        });

        return pathEdgeIds;
    }

    // ─── Highlight Application ─────────────────────────────────────────────────

    /**
     * Apply visual highlight to path elements and dim non-path elements.
     * @param {cytoscape.Core} cy
     * @param {Set<string>} pathNodeIds
     * @param {Set<string>} pathEdgeIds
     * @private
     */
    _applyHighlight(cy, pathNodeIds, pathEdgeIds) {
        // First clear any existing path highlight
        cy.elements().removeClass('path-highlighted path-dimmed path-source');
        cy.elements().removeStyle('opacity');

        // Batch style changes for performance
        cy.startBatch();

        // Dim ALL elements first using inline style (more reliable than class)
        cy.elements().style('opacity', 0.15);

        // Un-dim and highlight path nodes
        pathNodeIds.forEach(function (id) {
            var el = cy.getElementById(id);
            if (el && el.length > 0) {
                el.style('opacity', 1);
                el.addClass('path-highlighted');
            }
        });

        // Un-dim and highlight path edges
        pathEdgeIds.forEach(function (id) {
            var el = cy.getElementById(id);
            if (el && el.length > 0) {
                el.style('opacity', 1);
                el.addClass('path-highlighted');
            }
        });

        // Mark the source node distinctly
        var sourceId = this._tracedNodeId;
        if (sourceId) {
            var sourceNode = cy.getElementById(sourceId);
            if (sourceNode && sourceNode.length > 0) {
                sourceNode.addClass('path-source');
            }
        }

        cy.endBatch();
    }

    // ─── Event Handling ────────────────────────────────────────────────────────

    /**
     * Bind EventBus listeners for path highlight requests and clearing.
     * @private
     */
    _bindEvents() {
        if (typeof EventBus === 'undefined' || typeof CONFIG === 'undefined') return;

        // Listen for path highlight requests (Shift+click or Trace Path button)
        this._unsubHighlight = EventBus.on('path:highlight-requested', (data) => {
            console.log('[GraphPathHighlighter] path:highlight-requested received:', data);
            if (!data || !data.nodeId) return;
            var cy = this._getCytoscapeInstance();
            if (!cy) {
                console.warn('[GraphPathHighlighter] No Cytoscape instance available');
                return;
            }
            console.log('[GraphPathHighlighter] Highlighting path for node:', data.nodeId);
            this.highlightPath(cy, data.nodeId);
            if (cy) {
                this.highlightPath(cy, data.nodeId);
            }
        });

        // Listen for path clear requests
        this._unsubCleared = EventBus.on('path:clear-requested', () => {
            var cy = this._getCytoscapeInstance();
            if (cy) {
                this.clearPath(cy);
            }
        });

        // Clear path when a new model is loaded
        this._unsubModelLoaded = EventBus.on(CONFIG.EVENTS.MODEL_LOADED, () => {
            var cy = this._getCytoscapeInstance();
            if (cy) {
                this.clearPath(cy);
            }
        });
    }

    /**
     * Attach Shift+click and background-click handlers to a Cytoscape instance.
     * Call this after the graph is initialized/rendered.
     * @param {cytoscape.Core} cy
     */
    attachCytoscapeHandlers(cy) {
        if (!cy) return;

        // Remove previous handlers to avoid duplicates
        cy.off('tap.pathHighlighter');

        // Shift+click on a node → trace path
        cy.on('tap.pathHighlighter', 'node', (evt) => {
            if (evt.originalEvent && evt.originalEvent.shiftKey) {
                var nodeId = evt.target.id();
                this.highlightPath(cy, nodeId);
            }
        });

        // Click on background → clear path
        cy.on('tap.pathHighlighter', (evt) => {
            if (evt.target === cy && this._isActive) {
                this.clearPath(cy);
            }
        });
    }

    // ─── Helpers ───────────────────────────────────────────────────────────────

    /**
     * Get the Cytoscape instance from the global app interface.
     * @returns {cytoscape.Core|null}
     * @private
     */
    _getCytoscapeInstance() {
        if (window._onnxApp && typeof window._onnxApp.getGraphVisualizer === 'function') {
            var gv = window._onnxApp.getGraphVisualizer();
            if (gv && gv._cy) {
                return gv._cy;
            }
        }
        return null;
    }

    /**
     * Show a temporary message to the user (e.g., "no path found").
     * @param {string} message
     * @private
     */
    _showMessage(message) {
        // Use EventBus error display if available
        if (typeof EventBus !== 'undefined' && typeof CONFIG !== 'undefined') {
            EventBus.emit(CONFIG.EVENTS.ERROR_OCCURRED, {
                message: message,
                type: 'info'
            });
            return;
        }
        console.info('[GraphPathHighlighter]', message);
    }
}

// Export as global for browser usage
window.GraphPathHighlighter = GraphPathHighlighter;