const http = require('http');
const https = require('https');

/**
 * Phase 6+7: LLM Prose Generator
 * Generates human-readable prose for system documentation using Claude Sonnet.
 * All structural analysis is deterministic — LLM is ONLY for prose formatting.
 */

const DEFAULT_URL = process.env.LLM_URL || 'http://192.168.86.11:8000/v1';
const DEFAULT_MODEL = process.env.LLM_MODEL || 'claude-sonnet-4.6';
const DEFAULT_API_KEY = process.env.LLM_API_KEY || 'my-super-secret-password-123';

/**
 * Call an OpenAI-compatible chat completions API.
 */
function callLLM(prompt, opts = {}) {
  const baseUrl = opts.url || DEFAULT_URL;
  const model = opts.model || DEFAULT_MODEL;
  const apiKey = opts.apiKey || DEFAULT_API_KEY;
  const maxTokens = opts.maxTokens || 1024;
  const temperature = opts.temperature || 0.3;

  return new Promise((resolve, reject) => {
    const url = new URL('/v1/chat/completions', baseUrl.replace(/\/v1\/?$/, ''));
    const body = JSON.stringify({
      model,
      messages: [
        { role: 'system', content: 'You are a senior software architect writing concise, precise technical documentation. Write in present tense. Be specific about domain logic, not syntax. No filler.' },
        { role: 'user', content: prompt },
      ],
      max_tokens: maxTokens,
      temperature,
    });

    const client = url.protocol === 'https:' ? https : http;
    const req = client.request(url, {
      method: 'POST',
      headers: { 'Content-Type': 'application/json', 'Authorization': `Bearer ${apiKey}` },
    }, (res) => {
      let data = '';
      res.on('data', c => data += c);
      res.on('end', () => {
        try {
          const parsed = JSON.parse(data);
          resolve(parsed.choices?.[0]?.message?.content || '');
        } catch (e) {
          reject(new Error(`LLM parse error: ${e.message} — raw: ${data.substring(0, 200)}`));
        }
      });
    });
    req.on('error', reject);
    req.setTimeout(120000, () => { req.destroy(); reject(new Error('LLM timeout (120s)')); });
    req.write(body);
    req.end();
  });
}

/**
 * Generate a prose overview for a subsystem.
 */
async function describeSubsystem(sub, deps, llmOpts) {
  const depList = Object.entries(deps)
    .filter(([k]) => k.startsWith(sub.name + '→') || k.endsWith('→' + sub.name))
    .map(([k, v]) => `${k}: ${v.calls} calls, ${v.imports} imports`)
    .slice(0, 10);

  const prompt = `Write a 2-3 sentence technical overview of the "${sub.name}" subsystem.

Facts:
- Kind: ${sub.kind}
- Files: ${sub.files.length}
- Functions: ${sub.entities.functions}, Classes: ${sub.entities.classes}, Modules: ${sub.entities.modules}
- Public exports: ${sub.publicExports.slice(0, 15).join(', ')}${sub.publicExports.length > 15 ? ` (+${sub.publicExports.length - 15} more)` : ''}
${depList.length > 0 ? `- Dependencies:\n  ${depList.join('\n  ')}` : '- No cross-subsystem dependencies'}

Write ONLY the overview paragraph, no heading.`;

  return callLLM(prompt, llmOpts);
}

/**
 * Generate a prose narrative for a data flow trace.
 */
async function describeFlow(flowResult, llmOpts) {
  const steps = flowResult.flow.slice(0, 20).map((s, i) =>
    `${i + 1}. [${s.subsystem}] ${s.entity}${s.crossedVia ? ` (crosses via ${s.crossedVia})` : ''}`
  ).join('\n');

  const prompt = `Write a 3-5 sentence narrative describing this data flow through the system.

Entry point: ${flowResult.entryPoint}
Subsystem sequence: ${flowResult.subsystemSequence.join(' → ')}
${flowResult.excludedNodes.length > 0 ? `Excluded (high fan-in): ${flowResult.excludedNodes.slice(0, 5).join(', ')}` : ''}
${flowResult.cyclesDetected.length > 0 ? `Cycles detected: ${flowResult.cyclesDetected.length}` : ''}

Steps:
${steps}${flowResult.flow.length > 20 ? `\n... (+${flowResult.flow.length - 20} more steps)` : ''}

Write ONLY the narrative paragraph, no heading. Explain what happens when this entry point is triggered and how data moves across subsystem boundaries.`;

  return callLLM(prompt, llmOpts);
}

/**
 * Generate a prose description for a contract (interface/type/enum).
 */
async function describeContract(contract, xref, llmOpts) {
  const usedBy = xref?.[contract.name]?.usedBy || [];
  let details = '';
  
  if (contract.type === 'Interface' && contract.fields) {
    details = `Fields: ${contract.fields.map(f => `${f.name}: ${f.type}`).join(', ')}`;
    if (contract.extends) details += `\nExtends: ${contract.extends.join(', ')}`;
  } else if (contract.type === 'Enum' && contract.members) {
    details = `Members: ${contract.members.join(', ')}`;
  } else if (contract.type.startsWith('Helm')) {
    // Helm contract types
    if (contract.fields) {
      details = `Fields: ${contract.fields.slice(0, 20).map(f => `${f.name}: ${f.type}`).join(', ')}`;
      if (contract.fields.length > 20) details += ` (+${contract.fields.length - 20} more)`;
    }
  }

  const typeLabel = contract.type.startsWith('Helm') ? `Helm ${contract.type.replace('Helm', '').toLowerCase()} contract` : `TypeScript ${contract.type.toLowerCase()}`;

  const prompt = `Write a 1-2 sentence description of this ${typeLabel}.

Name: ${contract.name}
Type: ${contract.type}
Defined in: ${contract.id}
Visibility: ${contract.visibility}
${details}
${usedBy.length > 0 ? `Used by subsystems: ${usedBy.join(', ')}` : 'Not referenced cross-subsystem'}

Write ONLY the description, no heading. Do not ask for more information.`;

  return callLLM(prompt, { ...llmOpts, maxTokens: 256 });
}

/**
 * Generate a system-level architecture overview.
 */
async function describeArchitecture(subsystems, crossCutting, stats, llmOpts) {
  const subList = subsystems.slice(0, 20).map(s =>
    `- ${s.name} (${s.kind}): ${s.entities.functions} functions, ${s.files.length} files`
  ).join('\n');

  const prompt = `Write a 4-6 sentence architecture overview for this software system.

Total subsystems: ${subsystems.length}
Cross-cutting concerns: ${crossCutting.join(', ') || 'none detected'}

Largest subsystems:
${subList}

Write ONLY the overview paragraph, no heading. Describe the high-level architecture, the role of cross-cutting concerns, and the overall system organization.`;

  return callLLM(prompt, { ...llmOpts, maxTokens: 512 });
}

module.exports = { callLLM, describeSubsystem, describeFlow, describeContract, describeArchitecture };