1 files changed, 390 insertions, 0 deletions
diff --git a/RGens/src/main/java/bjc/rgens/parser/RGrammarParser.java b/RGens/src/main/java/bjc/rgens/parser/RGrammarParser.java
new file mode 100644
index 0000000..83b295a
--- /dev/null
+++ b/RGens/src/main/java/bjc/rgens/parser/RGrammarParser.java
@@ -0,0 +1,390 @@
+package bjc.rgens.parser;
+
+import bjc.utils.funcdata.FunctionalList;
+import bjc.utils.funcdata.IList;
+import bjc.utils.funcutils.TriConsumer;
+import bjc.utils.ioutils.blocks.Block;
+import bjc.utils.ioutils.blocks.BlockReader;
+import bjc.utils.ioutils.blocks.SimpleBlockReader;
+
+import java.io.Reader;
+import java.io.StringReader;
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * Reads {@link RGrammar} from a input stream.
+ *
+ * @author student
+ */
+public class RGrammarParser {
+	/* Whether we are in debug mode or not. */
+	public static final boolean DEBUG = false;
+
+	/*
+	 * Templates for level-dependent delimiters.
+	 */
+	/* Pragma block delimiter. */
+	private static final String TMPL_PRAGMA_BLOCK_DELIM   = "\\R\\t{%d}(?!\\t)";
+	/* Rule declaration block delimiter. */
+	private static final String TMPL_RULEDECL_BLOCK_DELIM = "\\R\\t\\t{%d}";
+	/* Where block delimiter. */
+	private static final String TMPL_WHERE_BLOCK_DELIM    = "\\R\\t{%d}(?:in|end)\\R";
+	/* Top-level block delimiter. */
+	private static final String TMPL_TOPLEVEL_BLOCK_DELIM = "\\R\\t{%d}\\.?\\R";
+
+	/* Pragma impls. */
+	private static Map<String, TriConsumer<String, RGrammarBuilder, Integer>> pragmas;
+
+	/* Initialize pragmas. */
+	static {
+		pragmas = new HashMap<>();
+
+		pragmas.put("initial-rule", (body, build, level) -> {
+			int sep = body.indexOf(' ');
+
+			if (sep != -1) {
+				String msg = "Initial-rule pragma takes only one argument, the name of the initial rule";
+				throw new GrammarException(msg);
+			}
+
+			build.setInitialRule(body);
+		});
+
+		pragmas.put("despace-rule", (body, build, level) -> {
+			int sep = body.indexOf(' ');
+
+			if (sep != -1) {
+				String msg = "despace-rule pragma takes only one argument, the name of the rule to despace";
+				throw new GrammarException(msg);
+			}
+
+			build.despaceRule(body);
+		});
+
+		pragmas.put("export-rule", (body, build, level) -> {
+			String[] exports = body.split(" ");
+
+			for (String export : exports) {
+				build.addExport(export);
+			}
+		});
+
+		pragmas.put("regex-rule", (body, build, level) -> {
+			int nameIndex = body.indexOf(" ");
+
+			if(nameIndex == -1) {
+				throw new GrammarException("Regex-rule pragma takes two arguments: the name of the rule to process, then the regex to apply after the rule has been generated.");
+			}
+
+			String name = body.substring(0, nameIndex).trim();
+			String patt = body.substring(nameIndex + 1).trim();
+
+			build.regexizeRule(name, patt);
+		});
+
+		pragmas.put("suffix-with", (body, build, level) -> {
+			String[] parts = body.trim().split(" ");
+
+			if (parts.length != 2) {
+				String msg = "Suffix-with pragma takes two arguments, the name of the rule to suffix, then what to suffix it with";
+
+				throw new GrammarException(msg);
+			}
+
+			build.suffixWith(parts[0], parts[1]);
+		});
+
+		pragmas.put("prefix-with", (body, build, level) -> {
+			String[] parts = body.trim().split(" ");
+
+			if (parts.length != 2) {
+				String msg = "Prefix-with pragma takes two arguments, the name of the rule to prefix, then what to prefix it with";
+
+				throw new GrammarException(msg);
+			}
+
+			build.prefixWith(parts[0], parts[1]);
+		});
+	}
+
+	/**
+	 * Read a {@link RGrammar} from an input stream.
+	 *
+	 * @param is
+	 * 	The input stream to read from.
+	 *
+	 * @return 
+	 * 	The grammar represented by the stream.
+	 *
+	 * @throws GrammarException
+	 * 	Thrown if the grammar has a syntax error.
+	 */
+	public static RGrammar readGrammar(Reader is) throws GrammarException {
+		String dlm = String.format(TMPL_TOPLEVEL_BLOCK_DELIM, 0);
+
+		try (BlockReader reader = new SimpleBlockReader(dlm, is)) {
+			if (!reader.hasNextBlock()) {
+				throw new GrammarException("At least one top-level block must be present");
+			}
+
+			try {
+				RGrammarBuilder build = new RGrammarBuilder();
+
+				reader.forEachBlock((block) -> {
+					if(DEBUG)
+						System.err.printf("Handling top-level block (%s)\n", block);
+
+					handleBlock(build, block.contents, 0);
+				});
+
+				return build.toRGrammar();
+			} catch (GrammarException gex) {
+				String msg = String.format("Error in block (%s)", reader.getBlock());
+				throw new GrammarException(msg, gex);
+			}
+		} catch (Exception ex) {
+			throw new GrammarException("Unknown error handling block", ex);
+		}
+	}
+
+	/* Throughout these, level indicates the nesting level of that construct. */
+
+	/* Handles an arbitrary block. */
+	private static void handleBlock(RGrammarBuilder build, String block, 
+			int level) throws GrammarException {
+		/* Discard empty blocks. */
+		if (block.equals("") || block.matches("\\R"))
+			return;
+
+		int typeSep = block.indexOf(' ');
+
+		if (typeSep == -1) {
+			throw new GrammarException(
+			        "A block must start with a introducer, followed by a space, then the rest of the block");
+		}
+
+		String blockType = block.substring(0, typeSep).trim();
+
+		if (blockType.equalsIgnoreCase("pragma")) {
+			handlePragmaBlock(block, build, level);
+		} else if (blockType.startsWith("[")) {
+			handleRuleBlock(block, build, level);
+		} else if (blockType.equalsIgnoreCase("where")) {
+			handleWhereBlock(block, build, level);
+		} else if (blockType.equalsIgnoreCase("#")) {
+			if(DEBUG)
+				System.err.printf("Handled comment block (%s)\n", block);
+			/*
+			 * Comment block.
+			 *
+			 * @TODO 10/11/17 Ben Culkin :GrammarComment
+			 * 	Attach these to the grammar somehow so that they
+			 * 	can be re-output during formatting.
+			 */
+			return;
+		} else {
+			String msg = String.format("Unknown block type: '%s'", blockType);
+			throw new GrammarException(msg);
+		}
+	}
+
+	/* Handle reading a block of pragmas. */
+	private static void handlePragmaBlock(String block, RGrammarBuilder build,
+	                                      int level) throws GrammarException {
+		String dlm = String.format(TMPL_PRAGMA_BLOCK_DELIM, level);
+		try (BlockReader pragmaReader = new SimpleBlockReader(dlm, new StringReader(block))) {
+			try {
+				pragmaReader.forEachBlock((pragma) -> {
+					if(DEBUG)
+						System.err.printf("Handled pragma block (%s)\n", pragma);
+
+					String pragmaContents = pragma.contents;
+
+					int pragmaSep = pragmaContents.indexOf(' ');
+
+					if (pragmaSep == -1) {
+						String msg = "A pragma invocation must consist of the word pragma, followed by a space, then the body of the pragma";
+
+						throw new GrammarException(msg);
+					}
+
+					String pragmaLeader = pragmaContents.substring(0, pragmaSep);
+					String pragmaBody   = pragmaContents.substring(pragmaSep + 1);
+
+					if (!pragmaLeader.equalsIgnoreCase("pragma")) {
+						String msg = String.format("Illegal line leader in pragma block: '%s'", pragmaLeader);
+
+						throw new GrammarException(msg);
+					}
+
+					handlePragma(pragmaBody, build, level);
+				});
+			} catch (GrammarException gex) {
+				Block pragma = pragmaReader.getBlock();
+				String msg   = String.format("Error in pragma: (%s)", pragma);
+
+				throw new GrammarException(msg, gex);
+			}
+		} catch (Exception ex) {
+			throw new GrammarException("Unknown error handling pragma block", ex);
+		}
+	}
+
+	/* Handle an individual pragma in a block. */
+	private static void handlePragma(String pragma, RGrammarBuilder build,
+	                                 int level) throws GrammarException {
+		int bodySep = pragma.indexOf(' ');
+
+		if (bodySep == -1)
+			bodySep = pragma.length();
+
+		String pragmaName = pragma.substring(0, bodySep);
+		String pragmaBody = pragma.substring(bodySep + 1);
+
+		if (pragmas.containsKey(pragmaName)) {
+			try {
+				if(DEBUG)
+					System.err.printf("Handled pragma '%s'\n", pragmaName);
+
+				pragmas.get(pragmaName).accept(pragmaBody, build, level);
+			} catch (GrammarException gex) {
+				String msg = String.format("Error in pragma '%s'", pragmaName);
+
+				throw new GrammarException(msg, gex);
+			}
+		} else {
+			String msg = String.format("Unknown pragma '%s'", pragmaName);
+
+			throw new GrammarException(msg);
+		}
+	}
+
+	/* Handle a block of a rule declaration and one or more cases. */
+	private static void handleRuleBlock(String ruleBlock, RGrammarBuilder build,
+	                                    int level) throws GrammarException {
+		String dlm = String.format(TMPL_RULEDECL_BLOCK_DELIM, level);
+		try (BlockReader ruleReader = new SimpleBlockReader(dlm, new StringReader(ruleBlock))) {
+			try {
+				if (ruleReader.hasNextBlock()) {
+					/* Rule with a declaration followed by multiple cases. */
+					ruleReader.nextBlock();
+					Block declBlock = ruleReader.getBlock();
+
+					String declContents = declBlock.contents;
+					Rule rl = handleRuleDecl(build, declContents);
+
+					ruleReader.forEachBlock((block) -> {
+						/* Ignore comment lines. */
+						if(block.contents.trim().startsWith("#")) return;
+
+						handleRuleCase(block.contents, build, rl);
+					});
+				} else {
+					/* Rule with a declaration followed by a single case. */
+					handleRuleDecl(build, ruleBlock);
+				}
+			} catch (GrammarException gex) {
+				String msg = String.format("Error in rule case (%s)", ruleReader.getBlock());
+
+				throw new GrammarException(msg, gex);
+			}
+		} catch (Exception ex) {
+			throw new GrammarException("Unknown error handling rule block", ex);
+		}
+	}
+
+	/* Handle a rule declaration and its initial case. */
+	private static Rule handleRuleDecl(RGrammarBuilder build, String declContents) {
+		int declSep = declContents.indexOf("\u2192");
+
+		if (declSep == -1) {
+			/*
+			 * @NOTE
+			 * 	We should maybe remove support for the old
+			 * 	syntax at some point. However, maybe we don't
+			 * 	want to do so so as to make inputting grammars
+			 * 	easier.
+			 */
+			declSep = declContents.indexOf(' ');
+
+			if (declSep == -1) {
+				String msg = "A rule must be given at least one case in its declaration, and seperated from that case by \u2192";
+
+				throw new GrammarException(msg);
+			}
+		}
+
+		String ruleName = declContents.substring(0, declSep).trim();
+		String ruleBody = declContents.substring(declSep + 1).trim();
+
+		if (ruleName.equals("")) {
+			throw new GrammarException("The empty string is not a valid rule name");
+		}
+
+		Rule rul = build.getOrCreateRule(ruleName);
+
+		handleRuleCase(ruleBody, build, rul);
+
+		return rul;
+	}
+
+	/* Handle a single case of a rule. */
+	private static void handleRuleCase(String cse, RGrammarBuilder build, Rule rul) {
+		IList<CaseElement> caseParts = new FunctionalList<>();
+
+		for (String csepart : cse.split(" ")) {
+			String partToAdd = csepart.trim();
+
+			/* Ignore empty parts */
+			if (partToAdd.equals(""))
+				continue;
+
+			caseParts.add(CaseElement.createElement(partToAdd));
+		}
+
+		rul.addCase(new RuleCase(RuleCase.CaseType.NORMAL, caseParts));
+	}
+
+	/* Handle a where block (a block with local rules). */
+	private static void handleWhereBlock(String block, RGrammarBuilder build,
+	                                     int level) throws GrammarException {
+		int nlIndex = block.indexOf("\\n");
+
+		if (nlIndex == -1) {
+			throw new GrammarException("Where block must be a context followed by a body");
+		}
+
+		String trimBlock = block.substring(nlIndex).trim();
+
+		String whereDelim = String.format(TMPL_WHERE_BLOCK_DELIM, level);
+
+		try (BlockReader whereReader = new SimpleBlockReader(whereDelim,
+			                new StringReader(trimBlock))) {
+			try {
+				Block whereCtx = whereReader.next();
+
+				StringReader ctxReader = new StringReader(whereCtx.contents.trim());
+				String ctxDelim = String.format(TMPL_TOPLEVEL_BLOCK_DELIM, level + 1);
+
+				try (BlockReader bodyReader = new SimpleBlockReader(ctxDelim, ctxReader)) {
+					Block whereBody = whereReader.next();
+
+					/**
+					 * @TODO 10/11/17 Ben Culkin :WhereBlocks
+					 * 	Implement where blocks. 
+					 *
+					 * 	A where block has the context evaluated
+					 * 	in a new context, and the body executed
+					 * 	in that context.
+					 */
+				}
+			} catch (GrammarException gex) {
+				throw new GrammarException(String.format("Error in where block (%s)",
+				                           whereReader.getBlock()), gex);
+			}
+		} catch (Exception ex) {
+			throw new GrammarException("Unknown error in where block", ex);
+		}
+	}
+}