const http = require('http');
const fs = require('fs');
const path = require('path');
const zlib = require('zlib');
const url = require('url');

const DATA_DIR = __dirname;
const PORT = 7860;

let convoIndex = [];
let idToSource = {};
let fileCache = {};
let kpiCache = null;
let kpiCacheTime = 0;

function buildIndex() {
  const files = fs.readdirSync(DATA_DIR)
    .filter(f => f.startsWith('conversations-') && f.endsWith('.json'))
    .sort();
  
  const entries = [];
  for (const fname of files) {
    const fpath = path.join(DATA_DIR, fname);
    const convos = JSON.parse(fs.readFileSync(fpath, 'utf-8'));
    for (const c of convos) {
      const cid = c.conversation_id || c.id;
      entries.push({
        id: cid,
        title: c.title || '(untitled)',
        create_time: c.create_time,
        update_time: c.update_time,
        model: c.default_model_slug || '',
        _source_file: fname,
      });
    }
  }
  entries.sort((a, b) => (b.create_time || 0) - (a.create_time || 0));
  convoIndex = entries;
  idToSource = {};
  for (const e of entries) idToSource[e.id] = e._source_file;
  console.error(`Indexed ${entries.length} conversations`);
}

function getFileConversations(sourceFile) {
  if (fileCache[sourceFile]) return fileCache[sourceFile];
  const fpath = path.join(DATA_DIR, sourceFile);
  const convos = JSON.parse(fs.readFileSync(fpath, 'utf-8'));
  fileCache[sourceFile] = convos;
  return convos;
}

function findConversation(cid) {
  const sourceFile = idToSource[cid];
  if (!sourceFile) return null;
  const convos = getFileConversations(sourceFile);
  return convos.find(c => (c.conversation_id || c.id) === cid) || null;
}

function extractMessages(conversation) {
  const messages = [];
  const mapping = conversation.mapping || {};
  const current = conversation.current_node;
  
  const chain = [];
  let nodeId = current;
  while (nodeId && mapping[nodeId]) {
    chain.push(nodeId);
    nodeId = mapping[nodeId].parent;
  }
  chain.reverse();
  
  for (const nid of chain) {
    const node = mapping[nid];
    const msg = node.message;
    if (!msg) continue;
    const role = (msg.author && msg.author.role) || 'unknown';
    const content = msg.content || {};
    const parts = content.parts || [];
    const textParts = [];
    
    for (const p of parts) {
      if (typeof p === 'string') {
        textParts.push(p);
      } else if (typeof p === 'object' && p !== null) {
        if (p.text) {
          textParts.push(p.text);
        } else if (p.content_type === 'image_asset_pointer') {
          let assetId = p.asset_pointer || '';
          for (const prefix of ['file-service://', 'sediment://']) {
            assetId = assetId.replace(prefix, '');
          }
          textParts.push(`[image:${assetId}]`);
        }
      }
    }
    if (textParts.length === 0) continue;
    messages.push({
      role,
      text: textParts.join('\n'),
      create_time: msg.create_time,
      model: (msg.metadata && msg.metadata.model_slug) || '',
    });
  }
  return messages;
}

function computeKPIs() {
  const now = Date.now();
  if (kpiCache && (now - kpiCacheTime) < 60000) return kpiCache;
  
  const modelCounts = {};
  const dateCounts = {};
  const hourCounts = {};
  const weekdayCounts = {};
  let earliest = null, latest = null;
  
  let totalMessages = 0, totalUser = 0, totalAssistant = 0, totalSystem = 0, totalTool = 0;
  let totalCharsUser = 0, totalCharsAssistant = 0, totalImages = 0;
  const promptLengths = [], responseLengths = [];
  const convoTop = [];
  const modelMsgStats = {};
  
  const files = fs.readdirSync(DATA_DIR)
    .filter(f => f.startsWith('conversations-') && f.endsWith('.json'))
    .sort();
  
  for (const fname of files) {
    const convos = getFileConversations(fname);
    for (const c of convos) {
      const cid = c.conversation_id || c.id;
      const title = c.title || '(untitled)';
      const ct = c.create_time;
      const model = c.default_model_slug || 'unknown';
      
      modelCounts[model] = (modelCounts[model] || 0) + 1;
      if (ct) {
        const d = new Date(ct * 1000);
        const dk = `${d.getFullYear()}-${String(d.getMonth()+1).padStart(2,'0')}`;
        dateCounts[dk] = (dateCounts[dk] || 0) + 1;
        hourCounts[d.getHours()] = (hourCounts[d.getHours()] || 0) + 1;
        weekdayCounts[d.getDay()] = (weekdayCounts[d.getDay()] || 0) + 1;
        if (earliest === null || ct < earliest) earliest = ct;
        if (latest === null || ct > latest) latest = ct;
      }
      
      if (!modelMsgStats[model]) modelMsgStats[model] = { msgs: 0, chars: 0, convos: 0 };
      modelMsgStats[model].convos++;
      
      const msgs = extractMessages(c);
      totalMessages += msgs.length;
      
      for (const m of msgs) {
        const tlen = m.text.length;
        if (m.text.includes('[image:')) totalImages += (m.text.match(/\[image:/g) || []).length;
        modelMsgStats[model].msgs++;
        modelMsgStats[model].chars += tlen;
        
        if (m.role === 'user') {
          totalUser++; totalCharsUser += tlen; promptLengths.push(tlen);
        } else if (m.role === 'assistant') {
          totalAssistant++; totalCharsAssistant += tlen; responseLengths.push(tlen);
        } else if (m.role === 'system') totalSystem++;
        else if (m.role === 'tool') totalTool++;
      }
      
      convoTop.push({ id: cid, title, msg_count: msgs.length, model, create_time: ct });
    }
  }
  
  convoTop.sort((a, b) => b.msg_count - a.msg_count);
  const top10 = convoTop.slice(0, 10);
  
  const totalChars = totalCharsUser + totalCharsAssistant;
  const estTokens = Math.floor(totalChars / 4);
  const avgMsgs = totalMessages / convoIndex.length;
  const avgUserChars = totalUser ? totalCharsUser / totalUser : 0;
  const avgAsstChars = totalAssistant ? totalCharsAssistant / totalAssistant : 0;
  
  const bucketLabels = ['<100', '100-500', '500-1K', '1K-5K', '5K-10K', '10K+'];
  const promptBuckets = [0,0,0,0,0,0];
  for (const pl of promptLengths) {
    if (pl < 100) promptBuckets[0]++;
    else if (pl < 500) promptBuckets[1]++;
    else if (pl < 1000) promptBuckets[2]++;
    else if (pl < 5000) promptBuckets[3]++;
    else if (pl < 10000) promptBuckets[4]++;
    else promptBuckets[5]++;
  }
  const responseBuckets = [0,0,0,0,0,0];
  for (const rl of responseLengths) {
    if (rl < 100) responseBuckets[0]++;
    else if (rl < 500) responseBuckets[1]++;
    else if (rl < 1000) responseBuckets[2]++;
    else if (rl < 5000) responseBuckets[3]++;
    else if (rl < 10000) responseBuckets[4]++;
    else responseBuckets[5]++;
  }
  
  promptLengths.sort((a,b) => a-b);
  responseLengths.sort((a,b) => a-b);
  const medianPrompt = promptLengths.length ? promptLengths[Math.floor(promptLengths.length / 2)] : 0;
  const medianResponse = responseLengths.length ? responseLengths[Math.floor(responseLengths.length / 2)] : 0;
  const p90Prompt = promptLengths.length ? promptLengths[Math.floor(promptLengths.length * 0.9)] : 0;
  const p90Response = responseLengths.length ? responseLengths[Math.floor(responseLengths.length * 0.9)] : 0;
  
  // Build timeline
  const timeline = [];
  if (earliest && latest) {
    let cur = new Date(earliest * 1000);
    cur = new Date(cur.getFullYear(), cur.getMonth(), 1);
    const end = new Date(latest * 1000);
    while (cur <= end) {
      const key = `${cur.getFullYear()}-${String(cur.getMonth()+1).padStart(2,'0')}`;
      timeline.push({ month: key, count: dateCounts[key] || 0 });
      cur = new Date(cur.getFullYear(), cur.getMonth() + 1, 1);
    }
  }
  
  const dayNames = ['Sun', 'Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat'];
  const weekdayData = [];
  for (let i = 0; i < 7; i++) weekdayData.push({ day: dayNames[i], count: weekdayCounts[i] || 0 });
  const hourData = [];
  for (let h = 0; h < 24; h++) hourData.push({ hour: h, count: hourCounts[h] || 0 });
  
  const modelStats = Object.entries(modelMsgStats)
    .sort((a, b) => b[1].convos - a[1].convos)
    .map(([model, s]) => ({
      model, conversations: s.convos, messages: s.msgs, chars: s.chars,
      avg_msgs_per_convo: Math.round(s.msgs / s.convos * 10) / 10,
    }));
  
  const modelDist = Object.entries(modelCounts)
    .sort((a, b) => b[1] - a[1])
    .map(([model, count]) => ({ model, count }));
  
  const result = {
    total_conversations: convoIndex.length,
    total_messages: totalMessages,
    total_user_messages: totalUser,
    total_assistant_messages: totalAssistant,
    total_system_messages: totalSystem,
    total_tool_messages: totalTool,
    total_chars_user: totalCharsUser,
    total_chars_assistant: totalCharsAssistant,
    total_image_assets: totalImages,
    estimated_tokens: estTokens,
    avg_messages_per_convo: Math.round(avgMsgs * 10) / 10,
    avg_user_chars: Math.round(avgUserChars * 10) / 10,
    avg_assistant_chars: Math.round(avgAsstChars * 10) / 10,
    median_prompt_chars: medianPrompt,
    median_response_chars: medianResponse,
    p90_prompt_chars: p90Prompt,
    p90_response_chars: p90Response,
    prompt_length_distribution: bucketLabels.map((b, i) => ({ bucket: b, count: promptBuckets[i] })),
    response_length_distribution: bucketLabels.map((b, i) => ({ bucket: b, count: responseBuckets[i] })),
    earliest_timestamp: earliest,
    latest_timestamp: latest,
    model_distribution: modelDist,
    model_stats: modelStats,
    activity_timeline: timeline,
    weekday_distribution: weekdayData,
    hour_distribution: hourData,
    top_conversations: top10,
  };
  
  kpiCache = result;
  kpiCacheTime = now;
  return result;
}

const MIME = {
  '.dat': 'application/octet-stream', '.json': 'application/json',
  '.js': 'application/javascript', '.css': 'text/css',
  '.png': 'image/png', '.jpg': 'image/jpeg', '.jpeg': 'image/jpeg',
  '.gif': 'image/gif', '.webp': 'image/webp', '.svg': 'image/svg+xml',
  '.pdf': 'application/pdf', '.html': 'text/html',
};

function sendJson(res, data, status = 200) {
  const body = Buffer.from(JSON.stringify(data), 'utf-8');
  res.writeHead(status, {
    'Content-Type': 'application/json; charset=utf-8',
    'Content-Length': body.length,
    'Access-Control-Allow-Origin': '*',
  });
  res.end(body);
}

function sendFile(res, fpath, mimeType, supportRange = true, req) {
  const stat = fs.statSync(fpath);
  const range = req.headers.range;
  
  if (range && supportRange) {
    const [startStr, endStr] = range.replace('bytes=', '').split('-');
    let start = parseInt(startStr) || 0;
    let end = endStr ? parseInt(endStr) : stat.size - 1;
    end = Math.min(end, stat.size - 1);
    const length = end - start + 1;
    res.writeHead(206, {
      'Content-Range': `bytes ${start}-${end}/${stat.size}`,
      'Content-Length': length,
      'Access-Control-Allow-Origin': '*',
    });
    fs.createReadStream(fpath, { start, end }).pipe(res);
    return;
  }
  
  res.writeHead(200, {
    'Content-Type': mimeType,
    'Content-Length': stat.size,
    'Access-Control-Allow-Origin': '*',
    ...(supportRange ? { 'Accept-Ranges': 'bytes' } : {}),
  });
  fs.createReadStream(fpath).pipe(res);
}

const server = http.createServer((req, res) => {
  const parsed = url.parse(req.url);
  const p = parsed.pathname;
  
  if (p === '/' || p === '/index.html') {
    const fpath = path.join(DATA_DIR, 'index.html');
    if (fs.existsSync(fpath)) {
      sendFile(res, fpath, 'text/html; charset=utf-8', false, req);
    } else {
      sendJson(res, { error: 'index.html not found' }, 404);
    }
    return;
  }
  
  if (p === '/api/conversations') {
    const clean = convoIndex.map(e => {
      const { _source_file, ...rest } = e;
      return rest;
    });
    sendJson(res, clean);
    return;
  }
  
  if (p.startsWith('/api/conversation/')) {
    const cid = decodeURIComponent(p.replace('/api/conversation/', ''));
    const conv = findConversation(cid);
    if (!conv) { sendJson(res, { error: 'Conversation not found' }, 404); return; }
    const messages = extractMessages(conv);
    sendJson(res, {
      id: cid,
      title: conv.title || '(untitled)',
      create_time: conv.create_time,
      model: conv.default_model_slug || '',
      messages,
    });
    return;
  }
  
  if (p === '/api/stats') {
    sendJson(res, { total_conversations: convoIndex.length, data_dir: DATA_DIR });
    return;
  }
  
  if (p === '/api/kpi') {
    sendJson(res, computeKPIs());
    return;
  }
  
  // Static files
  const safePath = decodeURIComponent(p.replace(/^\//, ''));
  const fpath = path.join(DATA_DIR, safePath);
  const resolved = path.resolve(fpath);
  if (resolved.startsWith(DATA_DIR) && fs.existsSync(fpath) && fs.statSync(fpath).isFile()) {
    const ext = path.extname(fpath).toLowerCase();
    sendFile(res, fpath, MIME[ext] || 'application/octet-stream', true, req);
  } else {
    sendJson(res, { error: 'Not found', path: p }, 404);
  }
});

buildIndex();
server.listen(PORT, '0.0.0.0', () => {
  console.log(`\n  ChatScope Viewer`);
  console.log(`  Serving ${convoIndex.length} conversations`);
  console.log(`  Open: http://localhost:${PORT}\n`);
});