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# mermaid_renderer.py
import os
import sys
import subprocess
import tempfile
import logging
# Configure logging
logging.basicConfig(level=logging.INFO, format='%(asctime)s - %(levelname)s - %(message)s')
class MermaidRenderer:
"""
A Python class to render Mermaid diagrams using @mermaid-js/mermaid-cli.
"""
def __init__(self):
"""Initialize the renderer and check if dependencies are installed"""
self._check_dependencies()
def _check_dependencies(self):
"""Check if Node.js and npx are installed"""
try:
subprocess.run(["node", "--version"], capture_output=True, check=True, text=True)
logging.info("Node.js found.")
except (subprocess.SubprocessError, FileNotFoundError) as e:
logging.error(f"Node.js check failed: {e}")
# In a web context, exiting might not be ideal. Log error.
# Consider raising an exception or handling this state in the Flask app.
raise RuntimeError("Error: Node.js is not installed or not found in PATH.")
# Check if npx is available
try:
subprocess.run(["npx", "--version"], capture_output=True, check=True, text=True)
logging.info("npx found.")
except (subprocess.SubprocessError, FileNotFoundError) as e:
logging.error(f"npx check failed: {e}")
raise RuntimeError("Error: npx is not installed or not found in PATH.")
def render(self, mermaid_code, output_format="png", theme="default"):
"""
Render Mermaid code to the specified format into a temporary file.
Args:
mermaid_code (str): The Mermaid diagram code.
output_format (str, optional): Output format (png, pdf, svg). Default: png.
theme (str, optional): Mermaid theme. Default: default.
Returns:
tuple: (path_to_temp_output_file, temp_input_file_path) or raises Exception on error.
The caller is responsible for deleting these files.
"""
valid_formats = ["png", "pdf", "svg"]
if output_format not in valid_formats:
raise ValueError(f"Invalid output format '{output_format}'. Choose from: {', '.join(valid_formats)}")
valid_themes = ["default", "forest", "dark", "neutral"]
if theme not in valid_themes:
raise ValueError(f"Invalid theme '{theme}'. Choose from: {', '.join(valid_themes)}")
# Create temporary files (ensure they are deleted by the caller)
# Input file for mermaid code
temp_input_file = tempfile.NamedTemporaryFile(mode='w', suffix='.mmd', delete=False)
# Output file for the generated diagram
temp_output_file = tempfile.NamedTemporaryFile(suffix=f'.{output_format}', delete=False)
input_path = temp_input_file.name
output_path = temp_output_file.name
try:
temp_input_file.write(mermaid_code)
temp_input_file.close() # Close file before passing to subprocess
cmd = [
"npx", "@mermaid-js/mermaid-cli",
"-i", input_path,
"-o", output_path,
"-t", theme,
# No -f flag needed for mmdc, format is determined by -o extension
# However, explicitly setting background color might be needed for transparency
# "-b", "transparent" # Example: if you want transparent background for PNG/SVG
]
logging.info(f"Running mmdc command: {' '.join(cmd)}")
result = subprocess.run(cmd, check=True, capture_output=True, text=True)
logging.info(f"mmdc execution successful. Output saved to: {output_path}")
if result.stderr:
logging.warning(f"mmdc stderr: {result.stderr}")
# Return paths for Flask to handle; caller must delete files
return output_path, input_path
except subprocess.CalledProcessError as e:
logging.error(f"Error rendering diagram with mmdc: {e}")
logging.error(f"mmdc stderr: {e.stderr}")
# Clean up files on error before raising
temp_output_file.close()
os.unlink(output_path)
if os.path.exists(input_path): # Input file might already be closed/deleted
os.unlink(input_path)
raise RuntimeError(f"Error rendering diagram: {e.stderr or e}")
except Exception as e:
# Catch any other unexpected errors
logging.error(f"Unexpected error during rendering: {e}")
# Ensure cleanup
temp_input_file.close()
temp_output_file.close()
if os.path.exists(input_path): os.unlink(input_path)
if os.path.exists(output_path): os.unlink(output_path)
raise # Re-raise the caught exception
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