apps/backend/src/mcp/cognitive/GraphTraversalOptimizer.ts

import { neo4jService } from '../../database/Neo4jService';

/**
 * Advanced Graph Traversal Optimizer
 * Optimizes multi-hop graph queries for better performance
 */
export class GraphTraversalOptimizer {
    /**
     * Optimized breadth-first search with pruning
     */
    async optimizedBFS(
        startNodeId: string,
        targetCondition: (node: any) => boolean,
        maxDepth: number = 3,
        maxNodes: number = 100
    ): Promise<{ path: any[]; nodesVisited: number }> {
        await neo4jService.connect();

        try {
            // Use Cypher's built-in path finding with limits
            const result = await neo4jService.runQuery(
                `MATCH path = (start)-[*1..${maxDepth}]-(end)
         WHERE id(start) = $startId
         WITH path, nodes(path) as pathNodes
         LIMIT $maxNodes
         RETURN path, pathNodes`,
                { startId: parseInt(startNodeId), maxNodes }
            );

            await neo4jService.disconnect();

            if (result.length === 0) {
                return { path: [], nodesVisited: 0 };
            }

            // Find best path based on condition
            const bestPath = result.find(r => {
                const nodes = r.pathNodes;
                return nodes.some((node: any) => targetCondition(node));
            });

            return {
                path: bestPath?.pathNodes || [],
                nodesVisited: result.length,
            };
        } catch (error) {
            await neo4jService.disconnect();
            throw error;
        }
    }

    /**
     * Find shortest path with relationship type filtering
     */
    async findShortestPath(
        startNodeId: string,
        endNodeId: string,
        relationshipTypes?: string[],
        maxDepth: number = 5
    ): Promise<{ path: any[]; length: number } | null> {
        await neo4jService.connect();

        try {
            const relFilter = relationshipTypes
                ? `:${relationshipTypes.join('|')}`
                : '';

            const result = await neo4jService.runQuery(
                `MATCH path = shortestPath((start)-[${relFilter}*1..${maxDepth}]-(end))
         WHERE id(start) = $startId AND id(end) = $endId
         RETURN path, length(path) as pathLength`,
                { startId: parseInt(startNodeId), endId: parseInt(endNodeId) }
            );

            await neo4jService.disconnect();

            if (result.length === 0) return null;

            return {
                path: result[0].path,
                length: result[0].pathLength,
            };
        } catch (error) {
            await neo4jService.disconnect();
            throw error;
        }
    }

    /**
     * Find all paths with cost optimization
     */
    async findAllPathsWithCost(
        startNodeId: string,
        endNodeId: string,
        maxDepth: number = 4,
        costProperty: string = 'weight'
    ): Promise<Array<{ path: any[]; cost: number }>> {
        await neo4jService.connect();

        try {
            const result = await neo4jService.runQuery(
                `MATCH path = (start)-[*1..${maxDepth}]-(end)
         WHERE id(start) = $startId AND id(end) = $endId
         WITH path, relationships(path) as rels
         RETURN path, 
                reduce(cost = 0, r in rels | cost + coalesce(r.${costProperty}, 1)) as totalCost
         ORDER BY totalCost ASC
         LIMIT 10`,
                { startId: parseInt(startNodeId), endId: parseInt(endNodeId) }
            );

            await neo4jService.disconnect();

            return result.map(r => ({
                path: r.path,
                cost: r.totalCost,
            }));
        } catch (error) {
            await neo4jService.disconnect();
            throw error;
        }
    }

    /**
     * Community detection using label propagation
     */
    async detectCommunities(minCommunitySize: number = 3): Promise<Map<string, string[]>> {
        await neo4jService.connect();

        try {
            // Simple community detection based on connected components
            const result = await neo4jService.runQuery(
                `CALL gds.wcc.stream('myGraph')
         YIELD nodeId, componentId
         WITH componentId, collect(nodeId) as members
         WHERE size(members) >= $minSize
         RETURN componentId, members`,
                { minSize: minCommunitySize }
            );

            await neo4jService.disconnect();

            const communities = new Map<string, string[]>();
            result.forEach(r => {
                communities.set(r.componentId.toString(), r.members.map((id: any) => id.toString()));
            });

            return communities;
        } catch (error) {
            await neo4jService.disconnect();
            // Fallback to simple connected components
            return this.simpleConnectedComponents(minCommunitySize);
        }
    }

    /**
     * Fallback: Simple connected components without GDS
     */
    private async simpleConnectedComponents(minSize: number): Promise<Map<string, string[]>> {
        const result = await neo4jService.runQuery(
            `MATCH (n)
       OPTIONAL MATCH path = (n)-[*]-(m)
       WITH n, collect(DISTINCT m) as connected
       WHERE size(connected) >= $minSize
       RETURN id(n) as nodeId, [x in connected | id(x)] as members
       LIMIT 100`,
            { minSize }
        );

        const communities = new Map<string, string[]>();
        result.forEach((r, idx) => {
            communities.set(`community_${idx}`, r.members.map((id: any) => id.toString()));
        });

        return communities;
    }

    /**
     * PageRank-style importance scoring
     */
    async computeNodeImportance(dampingFactor: number = 0.85, iterations: number = 20): Promise<Map<string, number>> {
        await neo4jService.connect();

        try {
            // Try using GDS PageRank
            const result = await neo4jService.runQuery(
                `CALL gds.pageRank.stream('myGraph', {
           maxIterations: $iterations,
           dampingFactor: $dampingFactor
         })
         YIELD nodeId, score
         RETURN nodeId, score
         ORDER BY score DESC
         LIMIT 100`,
                { iterations, dampingFactor }
            );

            await neo4jService.disconnect();

            const scores = new Map<string, number>();
            result.forEach(r => {
                scores.set(r.nodeId.toString(), r.score);
            });

            return scores;
        } catch (error) {
            await neo4jService.disconnect();
            // Fallback to simple degree centrality
            return this.simpleDegreeCentrality();
        }
    }

    /**
     * Fallback: Simple degree centrality without GDS
     */
    private async simpleDegreeCentrality(): Promise<Map<string, number>> {
        const result = await neo4jService.runQuery(
            `MATCH (n)-[r]-(m)
       WITH n, count(r) as degree
       RETURN id(n) as nodeId, degree
       ORDER BY degree DESC
       LIMIT 100`
        );

        const scores = new Map<string, number>();
        result.forEach(r => {
            scores.set(r.nodeId.toString(), r.degree);
        });

        return scores;
    }
}

export const graphTraversalOptimizer = new GraphTraversalOptimizer();