const memory = require('../services/memory');
const inference = require('../services/inference');
const embedding = require('../services/embedding');
const qdrant = require('../services/qdrant');
const { ORCHESTRATION } = require('@nexusai/shared')

const { RECENT_EPISODE_LIMIT, SEMANTIC_LIMIT, SCORE_THRESHOLD, SYSTEM_PROMPT } = ORCHESTRATION;

function buildPrompt(recentEpisodes, semanticEpisodes, userMessage) {
    const parts = [SYSTEM_PROMPT];

    if (semanticEpisodes.length > 0 )
    {
        parts.push('Here are some relevant memories from earlier conversations:')
        for (const ep of semanticEpisodes) {
            parts.push(`User: ${ep.user_message}\nAssistant: ${ep.ai_response}`);
        }
        parts.push('---')
    }

    if (recentEpisodes.length > 0) {
        parts.push(`Here are some relevant memories from your past conversations:`);
        for (const ep of recentEpisodes) {
            parts.push(`User: ${ep.user_message}\nAssistant: ${ep.ai_response}`);
        }
        parts.push('--- End of recent memories ---\n');
    }

    parts.push(`User: ${userMessage}`);
    parts.push('Assistant:');

    return parts.join('\n');
}

async function getSemanticEpisodes(userMessage, sessionId, recentIds) {
    try {
        const vector = await embedding.embed(userMessage);
        const results = await qdrant.searchEpisodes( vector, {
            limit: SEMANTIC_LIMIT,
            scoreThreshold: SCORE_THRESHOLD,
            sessionId,
        });

        const fetched = await Promise.all(
            results
                .filter(r => !recentIds.has(r.id))
                .map(r => memory.getEpisodeById(r.id))
        );
        return fetched.filter(Boolean);
    } catch (err) {
        console.warn(`[orchestration] Semantic search failed, continuing without: `, err.message);
        return [];
    }
}

async function chat(externalId, userMessage, options = {}) {
    // 1. Resolve or create session
    let session = await memory.getSessionByExternalId(externalId);
    if (!session) session = await memory.createSession(externalId);

    // 2. Fetch recent episodes for context
    const recentEpisodes = await memory.getRecentEpisodes(session.id, RECENT_EPISODE_LIMIT );
    const recentIds = new Set(recentEpisodes.map(e => e.id));

    // 3. Semantic Search
    const semanticEpisodes = await getSemanticEpisodes(userMessage, session.id, recentIds);

    // 4. Assemble prompt
    const prompt = buildPrompt(recentEpisodes, semanticEpisodes, userMessage);

    // 5. Run inference
    const result = await inference.complete(prompt, options);

    // 6. Write episode back to memory
    memory.createEpisode(
        session.id,
        userMessage,
        result.text,
        (result.evalCount || 0) + (result.promptEvalCount || 0 )
    ).catch(err => console.error(`[orchestration] Failed to save episode`, err.message));

    // 7. Return response
    return {
        sessionId: externalId,
        response: result.text,
        model: result.model,
        tokenCount: (result.evalCount || 0 ) + (result.promptEvalCount || 0 ),
    };
}

async function chatStream(externalId, userMessage, onChunk, options = {} ) {
    // 1. Resolve or create session
    let session = await memory.getSessionByExternalId(externalId);
    if (!session) session = await memory.createSession(externalId);

    // 2. Context assembly
    const recentEpisodes = await memory.getRecentEpisodes(session.id, RECENT_EPISODE_LIMIT);
    const recentIds = new Set(recentEpisodes.map(e => e.id));
    const semanticEpisodes = await getSemanticEpisodes(userMessage, session.id, recentIds)

    // 3. Assemble Prompt
    const prompt = buildPrompt(recentEpisodes, semanticEpisodes, userMessage);

    // 4. Open stream to inference service
    const res = await inference.completeStream(prompt, options);

    let fullText = '';
    let model = '';
    let tokenCount = 0;

    // 5. Parse SSE chunks
    // Replace the current SSE parsing block in chatStream:
    for await (const chunk of res.body) {
        const lines = chunk.toString().split('\n');

        for (const line of lines) {
            if (!line.startsWith('data: ')) continue;
            const raw = line.slice(6).trim();
            if (raw === '[DONE]') continue;

            try {
                const data = JSON.parse(raw);

                // llama.cpp provider shape: { response, done }
                if (data.response) {
                    fullText += data.response;
                    onChunk(data.response);
                }

                // model comes through on done chunk from inference route
                if (data.model) model = data.model;

                // token count — inference.js route sends this on the done chunk
                if (data.done && data.tokenCount !== undefined) {
                    tokenCount = data.tokenCount;
                }

            } catch {
                // partial chunk — skip
            }
        }
    }

    // 6. Write Complete episode to memory
    if(fullText && fullText.trim()){
        memory.createEpisode(session.id, userMessage, fullText, tokenCount)
            .catch(err => console.error('[orchestration] Failed to save streamed episode:', err.message))
    }
    return {model, tokenCount};        
}

module.exports = { chat, chatStream };