/**
 * Code-specific chunking for source code files
 * Intelligently splits code while preserving context
 */

export interface CodeChunk {
  content: string;
  metadata: {
    chunkIndex: number;
    totalChunks: number;
    startLine: number;
    endLine: number;
    tokenCount: number;
    filePath: string;
    language?: string;
  };
}

export interface CodeChunkOptions {
  maxChunkSize?: number; // characters
  chunkOverlap?: number; // lines
  preserveFunctions?: boolean;
  preserveClasses?: boolean;
  filePath: string;
}

/**
 * Estimate token count (rough approximation: 1 token ≈ 4 characters)
 */
function estimateTokens(text: string): number {
  return Math.ceil(text.length / 4);
}

/**
 * Detect language from file path
 */
function detectLanguage(filePath: string): string | undefined {
  const ext = filePath.split('.').pop()?.toLowerCase();
  const langMap: Record<string, string> = {
    ts: 'typescript',
    tsx: 'typescript',
    js: 'javascript',
    jsx: 'javascript',
    py: 'python',
    java: 'java',
    go: 'go',
    rs: 'rust',
    cpp: 'cpp',
    c: 'c',
    cs: 'csharp',
    rb: 'ruby',
    php: 'php',
    swift: 'swift',
    kt: 'kotlin',
    sql: 'sql',
    css: 'css',
    scss: 'scss',
    html: 'html',
    json: 'json',
    yaml: 'yaml',
    yml: 'yaml',
    md: 'markdown',
  };
  return langMap[ext || ''];
}

/**
 * Chunk source code file intelligently
 */
export function chunkCode(
  content: string,
  options: CodeChunkOptions
): CodeChunk[] {
  const {
    maxChunkSize = 3000, // Larger chunks for code context
    chunkOverlap = 5,
    preserveFunctions = true,
    preserveClasses = true,
    filePath,
  } = options;

  const language = detectLanguage(filePath);
  const lines = content.split('\n');

  // For small files, return as single chunk
  if (content.length <= maxChunkSize) {
    return [
      {
        content,
        metadata: {
          chunkIndex: 0,
          totalChunks: 1,
          startLine: 1,
          endLine: lines.length,
          tokenCount: estimateTokens(content),
          filePath,
          language,
        },
      },
    ];
  }

  // For larger files, split by logical boundaries
  const chunks: CodeChunk[] = [];
  let currentChunk: string[] = [];
  let currentSize = 0;
  let chunkStartLine = 1;

  // Patterns for detecting logical boundaries
  const functionPattern = /^\s*(function|def|fn|func|fun|public|private|protected|static|async|export)\s/;
  const classPattern = /^\s*(class|interface|struct|enum|type)\s/;
  const importPattern = /^\s*(import|from|require|using|include)\s/;
  const commentPattern = /^\s*(\/\/|\/\*|\*|#|--|<!--)/;

  // Always include file header (imports, comments at top)
  let headerLines: string[] = [];
  for (let i = 0; i < Math.min(20, lines.length); i++) {
    const line = lines[i];
    if (importPattern.test(line) || commentPattern.test(line) || line.trim() === '') {
      headerLines.push(line);
    } else {
      break;
    }
  }

  for (let i = 0; i < lines.length; i++) {
    const line = lines[i];
    const lineSize = line.length + 1; // +1 for newline

    // Check if we should start a new chunk
    const shouldSplit =
      currentSize + lineSize > maxChunkSize &&
      currentChunk.length > 0 &&
      (functionPattern.test(line) ||
        classPattern.test(line) ||
        (line.trim() === '' && currentSize > maxChunkSize * 0.7));

    if (shouldSplit) {
      // Save current chunk
      const chunkContent = currentChunk.join('\n');
      chunks.push({
        content: chunkContent,
        metadata: {
          chunkIndex: chunks.length,
          totalChunks: 0, // Will update at end
          startLine: chunkStartLine,
          endLine: chunkStartLine + currentChunk.length - 1,
          tokenCount: estimateTokens(chunkContent),
          filePath,
          language,
        },
      });

      // Start new chunk with overlap and header
      const overlapStart = Math.max(0, currentChunk.length - chunkOverlap);
      currentChunk = [
        ...headerLines,
        '',
        `// ... continued from line ${chunkStartLine}`,
        '',
        ...currentChunk.slice(overlapStart),
      ];
      currentSize = currentChunk.reduce((sum, l) => sum + l.length + 1, 0);
      chunkStartLine = chunkStartLine + overlapStart;
    }

    currentChunk.push(line);
    currentSize += lineSize;
  }

  // Add final chunk
  if (currentChunk.length > 0) {
    const chunkContent = currentChunk.join('\n');
    chunks.push({
      content: chunkContent,
      metadata: {
        chunkIndex: chunks.length,
        totalChunks: 0,
        startLine: chunkStartLine,
        endLine: lines.length,
        tokenCount: estimateTokens(chunkContent),
        filePath,
        language,
      },
    });
  }

  // Update totalChunks for all chunks
  chunks.forEach((chunk) => {
    chunk.metadata.totalChunks = chunks.length;
  });

  return chunks;
}

/**
 * Generate a summary header for a code file
 */
export function generateCodeSummary(
  filePath: string,
  content: string,
  language?: string
): string {
  const lines = content.split('\n');
  const functions = lines.filter(line => /^\s*(function|def|fn|func|async function|export function)/.test(line));
  const classes = lines.filter(line => /^\s*(class|interface|struct|enum|type)\s/.test(line));
  
  let summary = `File: ${filePath}\n`;
  if (language) {
    summary += `Language: ${language}\n`;
  }
  summary += `Lines: ${lines.length}\n`;
  
  if (functions.length > 0) {
    summary += `Functions: ${functions.length}\n`;
  }
  if (classes.length > 0) {
    summary += `Classes/Types: ${classes.length}\n`;
  }
  
  return summary;
}