/*
 * Copyright (c) 2012-2017 The ANTLR Project. All rights reserved.
 * Use of this file is governed by the BSD 3-clause license that
 * can be found in the LICENSE.txt file in the project root.
 */

package org.antlr.v4.codegen.target;

import org.antlr.v4.codegen.CodeGenerator;
import org.antlr.v4.codegen.SourceType;
import org.antlr.v4.codegen.Target;
import org.antlr.v4.parse.ANTLRParser;
import org.antlr.v4.tool.Grammar;
import org.stringtemplate.v4.ST;

import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.util.Arrays;
import java.util.HashSet;
import java.util.Set;

public class GoTarget extends Target {
	protected static final HashSet<String> reservedWords = new HashSet<>(Arrays.asList(
		// keywords
		"break", "default", "func", "interface", "select",
		"case", "defer", "go", "map", "struct",
		"chan", "else", "goto", "package", "switch",
		"const", "fallthrough", "if", "range", "type",
		"continue", "for", "import", "return", "var",

		// predeclared identifiers https://golang.org/ref/spec#Predeclared_identifiers
		"bool", "byte", "complex64", "complex128", "error", "float32", "float64",
		"int", "int8", "int16", "int32", "int64", "rune", "string",
		"uint", "uint8", "uint16", "uint32", "uint64", "uintptr",
		"true", "false", "iota", "nil",
		"append", "cap", "close", "complex", "copy", "delete", "imag", "len",
		"make", "new", "panic", "print", "println", "real", "recover",
		"string",

		// interface definition of RuleContext from runtime/Go/antlr/rule_context.go
		"Accept", "GetAltNumber", "GetBaseRuleContext", "GetChild", "GetChildCount",
		"GetChildren", "GetInvokingState", "GetParent", "GetPayload", "GetRuleContext",
		"GetRuleIndex", "GetSourceInterval", "GetText", "IsEmpty", "SetAltNumber",
		"SetInvokingState", "SetParent", "String",

		// misc
		"rule", "parserRule", "action",

		// the use of start or stop abd others as a label name will cause the generation of a GetStart() or GetStop() method, which
		// then clashes with the GetStart() or GetStop() method that is generated by the code gen for the rule. So, we need to
		// convert it. This is not ideal as it will still probably confuse authors of parse listeners etc. but the code will
		// compile. This is a proof of Hyrum's law.
		"start", "stop", "exception",
		"sempred", "precpred", "addErrorListener"
	));

	private static final boolean DO_GOFMT = !Boolean.parseBoolean(System.getenv("ANTLR_GO_DISABLE_GOFMT"))
			&& !Boolean.parseBoolean(System.getProperty("antlr.go.disable-gofmt"));

	public GoTarget(CodeGenerator gen) {
		super(gen);
	}

	@Override
	protected Set<String> getReservedWords() {
		return reservedWords;
	}

	@Override
	protected void genFile(Grammar g, ST outputFileST, String fileName) {
		super.genFile(g, outputFileST, fileName);
		if (DO_GOFMT && !fileName.startsWith(".") /* criterion taken from gofmt */ && fileName.endsWith(".go")) {
			gofmt(new File(getCodeGenerator().tool.getOutputDirectory(g.fileName), fileName));
		}
	}

	private void gofmt(File fileName) {
		// Optimistically run gofmt. If this fails, it doesn't matter at this point. Wait for termination though,
		// because "gofmt -w" uses ioutil.WriteFile internally, which means it literally writes in-place with O_TRUNC.
		// That could result in a race. (Why oh why doesn't it do tmpfile + rename?)
		try {
			// TODO: need something like: String goExecutable = locateGo();
			ProcessBuilder gofmtBuilder = new ProcessBuilder("gofmt", "-w", "-s", fileName.getPath());
			gofmtBuilder.redirectErrorStream(true);
			Process gofmt = gofmtBuilder.start();
			InputStream stdout = gofmt.getInputStream();
			// TODO(wjkohnen): simplify to `while (stdout.Read() > 1) {}`
			byte[] buf = new byte[1 << 10];
			for (int l = 0; l > -1; l = stdout.read(buf)) {
				// There should not be any output that exceeds the implicit output buffer. In normal ops there should be
				// zero output. In case there is output, blocking and therefore killing the process is acceptable. This
				// drains the buffer anyway to play it safe.

				// dirty debug (change -w above to -d):
				// System.err.write(buf, 0, l);
			}
			gofmt.waitFor();
		} catch (IOException e) {
			// Probably gofmt not in $PATH, in any case ignore.
		} catch (InterruptedException forward) {
			Thread.currentThread().interrupt();
		}
	}

	@Override
	public String getRecognizerFileName(SourceType sourceType) {
		CodeGenerator gen = getCodeGenerator();
		Grammar g = gen.g;
		assert g!=null;
		String name;
		switch ( g.getType()) {
			case ANTLRParser.PARSER:
				name = g.name.endsWith("Parser") ? g.name.substring(0, g.name.length()-6) : g.name;
				return name.toLowerCase()+"_parser.go";
			case ANTLRParser.LEXER:
				name = g.name.endsWith("Lexer") ? g.name.substring(0, g.name.length()-5) : g.name; // trim off "lexer"
				return name.toLowerCase()+"_lexer.go";
			case ANTLRParser.COMBINED:
				return g.name.toLowerCase()+"_parser.go";
			default :
				return "INVALID_FILE_NAME";
		}
	}

	/** A given grammar T, return the listener name such as
	 *  TListener.java, if we're using the Java target.
 	 */
	@Override
	public String getListenerFileName(SourceType sourceType) {
		CodeGenerator gen = getCodeGenerator();
		Grammar g = gen.g;
		assert g.name != null;
		return g.name.toLowerCase()+"_listener.go";
	}

	/** A given grammar T, return the visitor name such as
	 *  TVisitor.java, if we're using the Java target.
 	 */
	@Override
	public String getVisitorFileName(SourceType sourceType) {
		CodeGenerator gen = getCodeGenerator();
		Grammar g = gen.g;
		assert g.name != null;
		return g.name.toLowerCase()+"_visitor.go";
	}

	/** A given grammar T, return a blank listener implementation
	 *  such as TBaseListener.java, if we're using the Java target.
 	 */
	@Override
	public String getBaseListenerFileName(SourceType sourceType) {
		CodeGenerator gen = getCodeGenerator();
		Grammar g = gen.g;
		assert g.name != null;
		return g.name.toLowerCase()+"_base_listener.go";
	}

	/** A given grammar T, return a blank listener implementation
	 *  such as TBaseListener.java, if we're using the Java target.
 	 */
	@Override
	public String getBaseVisitorFileName(SourceType sourceType) {
		CodeGenerator gen = getCodeGenerator();
		Grammar g = gen.g;
		assert g.name != null;
		return g.name.toLowerCase()+"_base_visitor.go";
	}
}