/**
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 *
 * Copyright 2016 Chiori Greene a.k.a. Chiori-chan <me@chiorichan.com>
 * All Right Reserved.
 */
package com.chiorichan.factory.groovy;

import groovy.lang.Binding;
import groovy.lang.GroovyShell;
import groovy.lang.Script;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.ByteBufOutputStream;

import java.io.PrintStream;
import java.io.UnsupportedEncodingException;
import java.nio.charset.Charset;
import java.util.Arrays;
import java.util.List;

import org.apache.commons.lang3.StringUtils;

import com.chiorichan.factory.ScriptBinding;
import com.chiorichan.factory.ScriptingContext;
import com.chiorichan.factory.ScriptingEngine;
import com.chiorichan.lang.ReportingLevel;
import com.chiorichan.lang.ScriptingException;

/**
 * SeaShell for handling GSP files.
 * ie. Embedded Groovy Files
 *
 * sample:
 * <p>
 * This is plain html<% print ", with a twist of groovy. Today's date: " + date("") %>.
 * </p>
 */
public class EmbeddedGroovyEngine implements ScriptingEngine
{
	private static final String MARKER_END = "%>";
	private static final String MARKER_START = "<%";

	private Binding binding = new Binding();
	private GroovyRegistry registry;

	public EmbeddedGroovyEngine( GroovyRegistry registry )
	{
		this.registry = registry;
	}

	public String escapeFragment( String fragment )
	{
		String brackets = "\"\"\"";

		fragment = fragment.replace( "\\$", "$" );
		fragment = fragment.replace( "$", "\\$" );

		if ( fragment.endsWith( "\"" ) )
			brackets = "'''";

		return "print " + brackets + fragment + brackets + "; ";
	}

	@Override
	public boolean eval( ScriptingContext context ) throws Exception
	{
		String source = context.readString();

		int fullFileIndex = 0;
		String[] dontStartWith = new String[] {"println", "print", "echo", "def", "import", "if", "for", "do", "}", "else", "//", "/*", "\n", "\r"};

		StringBuilder output = new StringBuilder();

		while ( fullFileIndex < source.length() )
		{
			int startIndex = source.indexOf( MARKER_START, fullFileIndex );
			if ( -1 != startIndex )
			{
				// Append all the simple text until the marker

				String fragment = escapeFragment( source.substring( fullFileIndex, startIndex ) );
				if ( !fragment.isEmpty() )
					output.append( fragment );

				int endIndex = source.indexOf( MARKER_END, Math.max( startIndex, fullFileIndex ) );

				if ( endIndex == -1 )
					throw new ScriptingException( ReportingLevel.E_PARSE, "Marker `<%` was not closed after line " + ( StringUtils.countMatches( output.toString(), "\n" ) + 1 ) + ", please check your source file and try again." );

				// Re gets the fragment?
				fragment = source.substring( startIndex + MARKER_START.length(), endIndex );

				boolean appendPrint = true;

				for ( String s : dontStartWith )
					if ( fragment.trim().startsWith( s ) || fragment.startsWith( s ) || fragment.trim().isEmpty() )
						appendPrint = false;

				// void will disable the print depend
				if ( fragment.trim().startsWith( "void" ) )
				{
					appendPrint = false;
					fragment = fragment.replace( " *void ?", "" );
				}

				if ( appendPrint )
					fragment = "print " + fragment;

				if ( !fragment.isEmpty() )
					output.append( fragment + "; " );

				// Position index after end marker
				fullFileIndex = endIndex + MARKER_END.length();
			}
			else
			{
				String fragment = escapeFragment( source.substring( fullFileIndex ) );

				if ( !fragment.isEmpty() )
					output.append( fragment );

				// Position index after the end of the file
				fullFileIndex = source.length() + 1;
			}
		}

		context.baseSource( output.toString() );
		try
		{
			Script script = GroovyRegistry.getCachedScript( context, binding );
			if ( script == null )
			{
				GroovyShell shell = registry.getNewShell( context, binding );
				script = registry.makeScript( shell, output.toString(), context );
			}
			context.result().object( script.run() );
		}
		catch ( Throwable t )
		{
			// Clear the input source code and replace it with the exception stack trace
			// context.resetAndWrite( ExceptionUtils.getStackTrace( t ) );
			context.reset();
			throw t;
		}
		return true;
	}

	@Override
	public List<String> getTypes()
	{
		return Arrays.asList( "embedded", "gsp", "jsp", "chi" );
	}

	@Override
	public void setBinding( ScriptBinding binding )
	{
		// Groovy Binding will keep the original EvalBinding map updated automatically. YAY!
		this.binding = new Binding( binding.getVariables() );
	}

	@Override
	public void setOutput( ByteBuf buffer, Charset charset )
	{
		try
		{
			binding.setProperty( "out", new PrintStream( new ByteBufOutputStream( buffer ), true, charset.name() ) );
		}
		catch ( UnsupportedEncodingException e )
		{
			e.printStackTrace();
		}
	}
}