import * as fs from 'node:fs';
import * as path from 'node:path';
import type { DependencyGraph, FileContext } from '../types/analysis.js';

const LANGUAGE_MAP: Record<string, string> = {
  '.js': 'javascript',
  '.mjs': 'javascript',
  '.cjs': 'javascript',
  '.jsx': 'javascript',
  '.ts': 'typescript',
  '.tsx': 'typescript',
  '.py': 'python',
  '.go': 'go',
  '.rs': 'rust',
  '.java': 'java',
  '.rb': 'ruby',
  '.php': 'php',
  '.c': 'c',
  '.cpp': 'cpp',
  '.cs': 'csharp',
  '.swift': 'swift',
  '.kt': 'kotlin',
};

const TEST_PATTERNS = [
  /\.test\.[jt]sx?$/,
  /\.spec\.[jt]sx?$/,
  /_test\.go$/,
  /test_.*\.py$/,
  /.*_test\.py$/,
  /\.test\.py$/,
  /Test\.java$/,
  /\.test\.rb$/,
];

const CONFIG_PATTERNS = [
  /\.config\.[jt]s$/,
  /\.rc$/,
  /\.json$/,
  /\.ya?ml$/,
  /\.toml$/,
  /\.ini$/,
  /\.env/,
  /Makefile$/,
  /Dockerfile$/,
];

const GENERATED_MARKERS = [
  '// Code generated',
  '# Generated by',
  '// AUTO-GENERATED',
  '/* eslint-disable */',
  '// @generated',
];

export function buildFileContext(
  filePath: string,
  projectRoot: string,
  graph?: DependencyGraph,
): FileContext {
  const content = fs.readFileSync(filePath, 'utf-8');
  const ext = path.extname(filePath);
  const language = LANGUAGE_MAP[ext] ?? 'unknown';
  const lines = content.split('\n');

  const relativePath = path.relative(projectRoot, filePath);
  const dirName = path.dirname(filePath);

  let siblingFiles: string[] = [];
  try {
    siblingFiles = fs
      .readdirSync(dirName)
      .filter((f) => {
        const full = path.join(dirName, f);
        try { return fs.statSync(full).isFile(); } catch { return false; }
      })
      .filter((f) => f !== path.basename(filePath))
      .slice(0, 20);
  } catch { /* dir read error */ }

  const imports = extractImports(content, language);

  let importedBy: string[] = [];
  if (graph) {
    const node = graph.nodes.get(relativePath) ?? graph.nodes.get(filePath);
    if (node) {
      importedBy = node.importedBy;
    }
  }

  return {
    filePath: relativePath,
    content,
    language,
    lineCount: lines.length,
    imports,
    importedBy,
    siblingFiles,
    isTestFile: isTestFile(relativePath),
    isConfigFile: isConfigFile(relativePath),
    isGenerated: isGeneratedFile(content),
  };
}

export function isTestFile(filePath: string): boolean {
  const name = path.basename(filePath);
  // Normalize separators for cross-platform matching
  const normalized = filePath.replace(/\\/g, '/');
  return TEST_PATTERNS.some((p) => p.test(name)) ||
    /(^|\/)(test|tests|__tests__)\//.test(normalized);
}

export function isConfigFile(filePath: string): boolean {
  const name = path.basename(filePath);
  return CONFIG_PATTERNS.some((p) => p.test(name));
}

export function isGeneratedFile(content: string): boolean {
  const header = content.slice(0, 500);
  return GENERATED_MARKERS.some((m) => header.includes(m));
}

function extractImports(content: string, language: string): string[] {
  const imports: string[] = [];

  if (['javascript', 'typescript'].includes(language)) {
    // ES imports
    const esImports = content.matchAll(/import\s+(?:.*?\s+from\s+)?['"]([^'"]+)['"]/g);
    for (const m of esImports) imports.push(m[1]);
    // require
    const requires = content.matchAll(/require\s*\(\s*['"]([^'"]+)['"]\s*\)/g);
    for (const m of requires) imports.push(m[1]);
  } else if (language === 'python') {
    const pyImports = content.matchAll(/(?:from\s+(\S+)\s+import|import\s+(\S+))/g);
    for (const m of pyImports) imports.push(m[1] ?? m[2]);
  } else if (language === 'go') {
    const goImports = content.matchAll(/import\s+(?:\(\s*)?["']([^"']+)["']/g);
    for (const m of goImports) imports.push(m[1]);
  } else if (language === 'java') {
    const javaImports = content.matchAll(/import\s+([\w.]+);/g);
    for (const m of javaImports) imports.push(m[1]);
  }

  return [...new Set(imports)];
}