const fs = require('fs');
const path = require('path');

/**
 * Phase 9: Terraform Extraction
 * Multi-pass regex parser for .tf files.
 * Extracts: modules, resources, variables, outputs, data sources, locals, providers.
 * Detects cross-references: var.X, module.X, local.X, data.X, resource refs.
 */

// Block types we care about
const BLOCK_TYPES = ['resource', 'data', 'module', 'variable', 'output', 'provider', 'locals', 'terraform'];

/**
 * Find matching closing brace for a block starting at `startLine`.
 * Returns the line index of the closing brace.
 */
function findBlockEnd(lines, startLine) {
  let depth = 0;
  for (let i = startLine; i < lines.length; i++) {
    const line = lines[i];
    // Count braces outside of strings (simplified — good enough for HCL)
    for (let j = 0; j < line.length; j++) {
      if (line[j] === '{') depth++;
      else if (line[j] === '}') {
        depth--;
        if (depth === 0) return i;
      }
    }
  }
  return lines.length - 1; // fallback
}

/**
 * Extract the body text of a block (between opening { and closing }).
 */
function extractBlockBody(lines, startLine, endLine) {
  const bodyLines = lines.slice(startLine, endLine + 1);
  return bodyLines.join('\n');
}

/**
 * Parse a variable block for type and default.
 */
function parseVariableBlock(body) {
  const result = { type: null, default: null, description: null };
  
  const typeMatch = body.match(/^\s*type\s*=\s*(.+)/m);
  if (typeMatch) result.type = typeMatch[1].trim();
  
  const defaultMatch = body.match(/^\s*default\s*=\s*(.+)/m);
  if (defaultMatch) result.default = defaultMatch[1].trim().replace(/^"(.*)"$/, '$1');
  
  const descMatch = body.match(/^\s*description\s*=\s*"([^"]+)"/m);
  if (descMatch) result.description = descMatch[1];
  
  return result;
}

/**
 * Parse a module block for source and version.
 */
function parseModuleBlock(body) {
  const result = { source: null, version: null };
  
  const sourceMatch = body.match(/^\s*source\s*=\s*"([^"]+)"/m);
  if (sourceMatch) result.source = sourceMatch[1];
  
  const versionMatch = body.match(/^\s*version\s*=\s*"([^"]+)"/m);
  if (versionMatch) result.version = versionMatch[1];
  
  return result;
}

/**
 * Parse an output block for value and description.
 */
function parseOutputBlock(body) {
  const result = { value: null, description: null };
  
  const valueMatch = body.match(/^\s*value\s*=\s*(.+)/m);
  if (valueMatch) result.value = valueMatch[1].trim();
  
  const descMatch = body.match(/^\s*description\s*=\s*"([^"]+)"/m);
  if (descMatch) result.description = descMatch[1];
  
  return result;
}

/**
 * Extract all cross-references from a block body.
 * Returns array of { type, name } objects.
 */
function extractReferences(body) {
  const refs = [];
  const seen = new Set();
  
  const patterns = [
    { regex: /var\.([a-zA-Z0-9_-]+)/g, type: 'variable' },
    { regex: /local\.([a-zA-Z0-9_-]+)/g, type: 'local' },
    { regex: /module\.([a-zA-Z0-9_-]+)/g, type: 'module' },
    { regex: /data\.([a-zA-Z0-9_-]+)\.([a-zA-Z0-9_-]+)/g, type: 'data' },
    // Resource references: aws_instance.web.id → resource ref
    { regex: /(?<!data\.)(?<!module\.)(?<!var\.)(?<!local\.)([a-z][a-z0-9]*_[a-z][a-z0-9_]*)\.([a-zA-Z0-9_-]+)\./g, type: 'resource' },
  ];
  
  for (const { regex, type } of patterns) {
    let m;
    while ((m = regex.exec(body)) !== null) {
      const key = type === 'data' ? `data.${m[1]}.${m[2]}` :
                  type === 'resource' ? `${m[1]}.${m[2]}` :
                  `${type}.${m[1]}`;
      if (!seen.has(key)) {
        seen.add(key);
        refs.push({ type, ref: key });
      }
    }
  }
  
  return refs;
}

/**
 * Extract all Terraform entities and relationships from a .tf file.
 * @param {string} filePath - Absolute path to the .tf file.
 * @param {string} repoRoot - Base path of the repository.
 * @returns {Object} { file, language: 'hcl', entities: [...], relationships: [...] }
 */
function extractTerraform(filePath, repoRoot) {
  const sourceCode = fs.readFileSync(filePath, 'utf8');
  const relFilePath = path.relative(repoRoot, filePath);
  const lines = sourceCode.split('\n');
  const entities = [];
  const relationships = [];

  // File-level entity
  const fileId = relFilePath;
  entities.push({
    id: fileId,
    type: 'Config',
    name: relFilePath,
    kind: 'terraform',
    visibility: 'public',
    line_range: [1, lines.length]
  });

  // Pass 1: Extract block declarations
  // Patterns:
  //   resource "type" "name" {
  //   data "type" "name" {
  //   module "name" {
  //   variable "name" {
  //   output "name" {
  //   provider "name" {
  //   locals {
  //   terraform {
  const blockRegex = /^(resource|data|module|variable|output|provider|locals|terraform)\s*(?:"([^"]+)")?(?:\s+"([^"]+)")?\s*\{/;

  for (let i = 0; i < lines.length; i++) {
    const trimmed = lines[i].trimStart();
    // Skip comments
    if (trimmed.startsWith('#') || trimmed.startsWith('//') || trimmed.startsWith('/*')) continue;
    
    const match = trimmed.match(blockRegex);
    if (!match) continue;

    const blockType = match[1];
    const label1 = match[2] || null;
    const label2 = match[3] || null;
    const blockEnd = findBlockEnd(lines, i);
    const body = extractBlockBody(lines, i, blockEnd);

    let entityId, entityName, entityKind, extra = {};

    switch (blockType) {
      case 'resource': {
        entityName = label2 ? `${label1}.${label2}` : label1;
        entityId = `${fileId}:resource.${entityName}`;
        entityKind = 'terraform-resource';
        extra = { resourceType: label1, resourceName: label2 };
        break;
      }
      case 'data': {
        entityName = label2 ? `${label1}.${label2}` : label1;
        entityId = `${fileId}:data.${entityName}`;
        entityKind = 'terraform-data';
        extra = { dataType: label1, dataName: label2 };
        break;
      }
      case 'module': {
        entityName = label1;
        entityId = `${fileId}:module.${entityName}`;
        entityKind = 'terraform-module';
        const modInfo = parseModuleBlock(body);
        extra = { source: modInfo.source, version: modInfo.version };
        break;
      }
      case 'variable': {
        entityName = label1;
        entityId = `${fileId}:variable.${entityName}`;
        entityKind = 'terraform-variable';
        const varInfo = parseVariableBlock(body);
        extra = { varType: varInfo.type, default: varInfo.default, description: varInfo.description };
        break;
      }
      case 'output': {
        entityName = label1;
        entityId = `${fileId}:output.${entityName}`;
        entityKind = 'terraform-output';
        const outInfo = parseOutputBlock(body);
        extra = { value: outInfo.value, description: outInfo.description };
        break;
      }
      case 'provider': {
        entityName = label1;
        entityId = `${fileId}:provider.${entityName}`;
        entityKind = 'terraform-provider';
        break;
      }
      case 'locals': {
        entityName = 'locals';
        entityId = `${fileId}:locals.${i + 1}`;
        entityKind = 'terraform-locals';
        // Extract local names from body
        const localNames = [];
        const localRegex = /^\s*([a-zA-Z_][a-zA-Z0-9_]*)\s*=/gm;
        let lm;
        while ((lm = localRegex.exec(body)) !== null) {
          localNames.push(lm[1]);
        }
        extra = { localNames };
        break;
      }
      case 'terraform': {
        entityName = 'terraform';
        entityId = `${fileId}:terraform`;
        entityKind = 'terraform-config';
        break;
      }
      default:
        continue;
    }

    entities.push({
      id: entityId,
      type: 'Config',
      name: entityName,
      kind: entityKind,
      visibility: 'public',
      line_range: [i + 1, blockEnd + 1],
      ...extra
    });

    relationships.push({
      type: 'CONTAINS',
      source: fileId,
      target: entityId
    });

    // Pass 2: Extract cross-references from block body
    const refs = extractReferences(body);
    for (const ref of refs) {
      relationships.push({
        type: 'DEPENDS_ON',
        source: entityId,
        target: `${ref.ref}`, // Will be resolved to full IDs during graph merge
        _refType: ref.type,
        _unresolved: true
      });
    }

    // Skip to end of block
    i = blockEnd;
  }

  return { file: filePath, language: 'hcl', entities, relationships };
}

/**
 * Resolve unresolved DEPENDS_ON references within a set of extraction results.
 * Matches var.X → variable.X, module.X → module.X, etc. within the same directory tree.
 */
function resolveReferences(results) {
  // Build lookup: shortRef → full entityId
  const lookup = new Map();
  for (const result of results) {
    for (const entity of result.entities) {
      if (entity.kind === 'terraform-variable') {
        lookup.set(`variable.${entity.name}`, entity.id);
      } else if (entity.kind === 'terraform-module') {
        lookup.set(`module.${entity.name}`, entity.id);
      } else if (entity.kind === 'terraform-resource') {
        lookup.set(`resource.${entity.name}`, entity.id);
        // Also register as type.name for resource refs
        if (entity.resourceType && entity.resourceName) {
          lookup.set(`${entity.resourceType}.${entity.resourceName}`, entity.id);
        }
      } else if (entity.kind === 'terraform-data') {
        lookup.set(`data.${entity.name}`, entity.id);
      } else if (entity.kind === 'terraform-locals') {
        if (entity.localNames) {
          for (const ln of entity.localNames) {
            lookup.set(`local.${ln}`, entity.id);
          }
        }
      }
    }
  }

  // Resolve
  for (const result of results) {
    for (const rel of result.relationships) {
      if (rel._unresolved) {
        const resolved = lookup.get(rel.target) || lookup.get(rel._refType + '.' + rel.target);
        if (resolved) {
          rel.target = resolved;
        }
        delete rel._unresolved;
        delete rel._refType;
      }
    }
  }

  return results;
}

// CLI
if (require.main === module) {
  const filePath = process.argv[2];
  const repoRoot = process.argv[3] || process.cwd();
  if (!filePath) {
    console.error('Usage: node extract-terraform.js <file.tf> [repoRoot]');
    process.exit(1);
  }
  const result = extractTerraform(filePath, repoRoot);
  console.log(JSON.stringify(result, null, 2));
}

module.exports = { extractTerraform, resolveReferences };