/**
 * Context Engine Service
 * 
 * Stub for Context-Engine integration (https://github.com/Eskapeum/Context-Engine)
 * 
 * Features to integrate:
 * - Tree-sitter AST parsing (20+ languages)
 * - Incremental indexing with dependency tracking
 * - Git branch-aware per-user indexing
 * - cAST semantic chunking for optimal retrieval
 * - Hybrid retrieval (BM25 + dense vectors)
 * - MCP server for Claude Code integration
 * - Library documentation (local-first with optional API)
 * - Sequential thinking engine for complex reasoning
 * - Persistent memory with Q&A history
 * - Context sharing for team collaboration
 */

import { getLogger } from "@/lib/logger";

const log = getLogger("context-service");

export interface ContextEngineConfig {
    projectRoot: string;
    enableIndexing?: boolean;
    enableVectors?: boolean;
    vectorProvider?: "voyage" | "openai" | "local";
}

export interface RetrievedContext {
    content: string;
    sources: ContextSource[];
    relevanceScore: number;
}

export interface ContextSource {
    file: string;
    line?: number;
    symbol?: string;
    type: "code" | "documentation" | "memory" | "qa";
}

export interface IndexStats {
    filesIndexed: number;
    symbolsFound: number;
    lastUpdated: number;
}

// Singleton instance
let instance: ContextService | null = null;

export class ContextService {
    private config: ContextEngineConfig;
    private initialized: boolean = false;
    private stats: IndexStats = { filesIndexed: 0, symbolsFound: 0, lastUpdated: 0 };

    constructor(config: ContextEngineConfig) {
        this.config = config;
    }

    /**
     * Initialize the context engine
     */
    async initialize(): Promise<void> {
        if (this.initialized) return;

        log.info("Context Engine initializing...", { projectRoot: this.config.projectRoot });

        // TODO: Initialize Context-Engine
        // const engine = new ContextEngine({ projectRoot: this.config.projectRoot });
        // await engine.initialize();

        this.initialized = true;
        log.info("Context Engine initialized (stub)");
    }

    /**
     * Retrieve relevant context for a query
     */
    async retrieve(query: string, options?: { maxTokens?: number }): Promise<RetrievedContext> {
        if (!this.initialized) {
            await this.initialize();
        }

        log.info("Retrieving context for query", { query: query.substring(0, 50) });

        // TODO: Call Context-Engine retrieve
        // const context = await engine.retrieve(query);

        // Return stub response
        return {
            content: "",
            sources: [],
            relevanceScore: 0
        };
    }

    /**
     * Index or re-index the project
     */
    async index(options?: { force?: boolean }): Promise<IndexStats> {
        log.info("Indexing project...", { force: options?.force });

        // TODO: Call Context-Engine indexer
        // await engine.index();

        this.stats = {
            filesIndexed: 0,
            symbolsFound: 0,
            lastUpdated: Date.now()
        };

        return this.stats;
    }

    /**
     * Get current index stats
     */
    getStats(): IndexStats {
        return this.stats;
    }

    /**
     * Add to Q&A memory
     */
    async remember(question: string, answer: string): Promise<void> {
        log.info("Remembering Q&A", { question: question.substring(0, 50) });

        // TODO: Call Context-Engine memory
        // await engine.remember(question, answer);
    }

    /**
     * Search Q&A memory
     */
    async recall(query: string): Promise<{ question: string; answer: string }[]> {
        log.info("Recalling from memory", { query: query.substring(0, 50) });

        // TODO: Call Context-Engine memory search
        // return await engine.recall(query);

        return [];
    }
}

/**
 * Get or create context service instance
 */
export function getContextService(config?: ContextEngineConfig): ContextService {
    if (!instance && config) {
        instance = new ContextService(config);
    }
    if (!instance) {
        throw new Error("Context service not initialized. Provide config on first call.");
    }
    return instance;
}

/**
 * Initialize context service for a workspace
 */
export async function initializeContextService(projectRoot: string): Promise<ContextService> {
    const service = getContextService({ projectRoot });
    await service.initialize();
    return service;
}

export default {
    ContextService,
    getContextService,
    initializeContextService,
};
