const fs = require('fs');
const path = require('path');
const GraphStore = require('./graph.js');
const { buildSubsystems } = require('./subsystem.js');
const { extractAllContracts, buildContractXref } = require('./contracts.js');
const { buildFlowIndex, traceFlow } = require('./flow.js');
const { generateDependencyDiagram, generateFlowDiagram, generateContractDiagram } = require('./diagrams.js');

/**
 * Phase 7D: Hierarchical Doc Generator
 * Orchestrates 7A, 7B, 7C, and 7E to generate a Divio-structured documentation site.
 */

async function generateDocs(graph, srcRoot, outDir, opts = {}) {
  const entryPoints = opts.entryPoints || [];
  const useProse = opts.prose === true;
  
  // Optional LLM module for prose enrichment
  let proseMod = null;
  if (useProse) {
    try {
      proseMod = require('./prose.js');
      console.log('Prose generation enabled (LLM pass active)');
    } catch (err) {
      console.warn('Prose generation requested but prose.js not available. Skipping LLM pass.');
    }
  }
  
  // 1. Build Subsystems (7A)
  const subs = buildSubsystems(graph, {
    srcDir: opts.srcDir || '/src/',
    minTraffic: opts.minTraffic || 3,
    crossCuttingThreshold: opts.crossCuttingThreshold || 0.6
  });

  // 2. Extract Contracts (7B)
  const contractsResult = extractAllContracts(subs, srcRoot);
  const xref = buildContractXref(contractsResult.contracts, graph, (p) => p.replace(/^\/?src\//, ''));
  
  // 3. Trace Flows (7C)
  const flowIndex = buildFlowIndex(graph, subs);
  const flowResults = entryPoints.map(ep => traceFlow(ep, flowIndex));

  // Initialize output directory structure (Divio)
  const dirs = [
    'reference/subsystems',
    'reference/contracts',
    'reference/modules',
    'explanation',
    'tutorials',
    'how-to',
    'diagrams'
  ];
  
  for (const d of dirs) {
    fs.mkdirSync(path.join(outDir, d), { recursive: true });
  }

  // Generate Reference: System Architecture
  const sysArchPath = path.join(outDir, 'reference/system-architecture.md');
  const depDiag = generateDependencyDiagram(subs);
  const depDiagPath = 'diagrams/system-deps.mmd';
  fs.writeFileSync(path.join(outDir, depDiagPath), depDiag);
  
  let archProse = '';
  if (proseMod) {
    console.log('Generating architecture overview...');
    archProse = await proseMod.describeArchitecture(subs.subsystems, subs.crossCutting, {}, {});
    archProse = `\n${archProse.trim()}\n\n`;
  }
  
  const sysArchContent = `# System Architecture
${archProse}
## Subsystems
${subs.subsystems.map(s => `- **${s.name}** (${s.kind}): ${s.entities.modules} modules, ${s.entities.functions} functions`).join('\n')}

## Cross-Cutting Concerns
${subs.crossCutting.map(c => `- **${c}**`).join('\n')}

## Dependency Map
\`\`\`mermaid
${depDiag}
\`\`\`
`;
  fs.writeFileSync(sysArchPath, sysArchContent);

  // Generate Reference: Subsystem Docs
  for (const sub of subs.subsystems) {
    const subDocPath = path.join(outDir, `reference/subsystems/${sub.name}.md`);
    const subContracts = contractsResult.bySubsystem[sub.name] || [];
    
    let contractSection = '';
    if (subContracts.length > 0) {
      const contractDiag = generateContractDiagram(subContracts);
      fs.writeFileSync(path.join(outDir, `diagrams/${sub.name}-contracts.mmd`), contractDiag);
      contractSection = `\n## Contracts\n\`\`\`mermaid\n${contractDiag}\n\`\`\`\n`;
    }

    let subProse = '';
    if (proseMod) {
      console.log(`Generating prose for subsystem: ${sub.name}...`);
      subProse = await proseMod.describeSubsystem(sub, subs.dependencyMatrix, {});
      subProse = `\n${subProse.trim()}\n\n`;
    }

    const subContent = `# Subsystem: ${sub.name}
${subProse}
**Kind:** ${sub.kind}
**Files:** ${sub.files.length}

## Public Exports
${sub.publicExports.length > 0 ? sub.publicExports.map(e => `- \`${e}\``).join('\n') : '*None*'}
${contractSection}
## Files
${sub.files.map(f => `- \`${f}\``).join('\n')}
`;
    fs.writeFileSync(subDocPath, subContent);
  }

  // Generate Reference: Contracts
  const contractDocPath = path.join(outDir, 'reference/contracts/index.md');
  const allContractsDiag = generateContractDiagram(contractsResult.contracts);
  fs.writeFileSync(path.join(outDir, 'diagrams/all-contracts.mmd'), allContractsDiag);
  
  let contractProseList = '';
  if (proseMod && contractsResult.contracts.length > 0) {
    console.log(`Generating prose for ${contractsResult.contracts.length} contracts...`);
    // Batch processing to avoid overloading the API
    const batchSize = 10;
    const contractDocs = [];
    for (let i = 0; i < contractsResult.contracts.length; i += batchSize) {
      const batch = contractsResult.contracts.slice(i, i + batchSize);
      const docs = await Promise.all(batch.map(c => proseMod.describeContract(c, xref, {})));
      contractDocs.push(...docs);
    }
    contractProseList = contractsResult.contracts.map((c, i) => `### ${c.name}\n${contractDocs[i].trim()}\n`).join('\n');
  }

  fs.writeFileSync(contractDocPath, `# System Contracts\n\n\`\`\`mermaid\n${allContractsDiag}\n\`\`\`\n\n${contractProseList}`);

  // Generate Explanation: Data Flows
  const flowsPath = path.join(outDir, 'explanation/data-flows.md');
  let flowsContent = '# Data Flows\n\n';
  
  for (let i = 0; i < flowResults.length; i++) {
    const fr = flowResults[i];
    if (fr.error) {
      flowsContent += `## Flow: ${fr.entryPoint}\n**Error:** ${fr.error}\n\n`;
      continue;
    }
    const flowDiag = generateFlowDiagram(fr);
    const diagName = `flow-${i}.mmd`;
    fs.writeFileSync(path.join(outDir, `diagrams/${diagName}`), flowDiag);
    
    let flowProse = '';
    if (proseMod) {
      console.log(`Generating prose for flow: ${fr.entryPoint}...`);
      flowProse = await proseMod.describeFlow(fr, {});
      flowProse = `${flowProse.trim()}\n\n`;
    }
    
    flowsContent += `## Flow: ${fr.entryPoint}\n`;
    flowsContent += flowProse;
    flowsContent += `**Subsystem Sequence:** ${fr.subsystemSequence.join(' → ')}\n\n`;
    flowsContent += `\`\`\`mermaid\n${flowDiag}\n\`\`\`\n\n`;
  }
  fs.writeFileSync(flowsPath, flowsContent);

  return {
    subsystems: subs.subsystems.length,
    contracts: contractsResult.contracts.length,
    flows: flowResults.length,
    outDir
  };
}

if (require.main === module) {
  const snapshotPath = process.argv[2];
  const srcRoot = process.argv[3];
  const outDir = process.argv[4];
  const useProse = process.argv.includes('--prose');
  const entryPoints = process.argv.slice(5).filter(a => a !== '--prose');

  if (!snapshotPath || !srcRoot || !outDir) {
    console.error('Usage: node sysdoc.js <snapshot.json> <srcRoot> <outDir> [--prose] [entryPoint1] ...');
    process.exit(1);
  }

  const graph = GraphStore.loadSnapshot(snapshotPath);
  // Using an IIFE to support top-level await
  (async () => {
    try {
      const result = await generateDocs(graph, srcRoot, outDir, { entryPoints, prose: useProse });
      console.log(`Generated docs in ${result.outDir}`);
      console.log(`- ${result.subsystems} subsystems`);
      console.log(`- ${result.contracts} contracts`);
      console.log(`- ${result.flows} flows`);
    } catch (err) {
      console.error('Error generating docs:', err);
      process.exit(1);
    }
  })();
}

module.exports = { generateDocs };