6 files changed, 166 insertions, 6 deletions

diff --git a/src/lexer/lexer.c b/src/lexer/lexer.c
index 59a71d8..ca51bb8 100644
--- a/src/lexer/lexer.c
+++ b/src/lexer/lexer.c
@@ -234,3 +234,4 @@ const char* token_type_name(enum TokenType type)
 
 	return "unknown";
 }
+
diff --git a/src/main.c b/src/main.c
index 9a9dae4..3196013 100644
--- a/src/main.c
+++ b/src/main.c
@@ -1,8 +1,10 @@
 #include <stdio.h>
+#include <stddef.h>
 
 #include "io/file.h"
 #include "cli/args.h"
 #include "lexer/lexer.h"
+#include "parser/parser.h"
 
 int main(int argc, char** argv)
 {
@@ -20,14 +22,22 @@ int main(int argc, char** argv)
 
 	struct Lexer lexer = create_lexer(source.data);
 
-	for (;;)
+	struct Program program;
+	if (!parse_program(&lexer, &program))
 	{
-		struct Token token = scan_token(&lexer);
-		printf("%4u  %-14s  %.*s\n", token.line, token_type_name(token.type), (int)token.length, token.start);
-		if (token.type == TOKEN_EOF)
-			break;
+		free_program(&program);
+		free_file(&source);
+		return 1;
+	}
+
+	for (size_t i = 0; i < program.const_count; i += 1)
+	{
+		struct ConstDecl decl = program.consts[i];
+		printf("const %.*s = %.*s\n",
+			(int)decl.name.length, decl.name.start,
+			(int)decl.value.length, decl.value.start);
 	}
 
+	free_program(&program);
 	free_file(&source);
-	return 0;
 }
diff --git a/src/parser/ast.c b/src/parser/ast.c
new file mode 100644
index 0000000..979dff0
--- /dev/null
+++ b/src/parser/ast.c
@@ -0,0 +1,33 @@
+#include <stdlib.h>
+
+#include "parser/ast.h"
+
+struct Program create_program(void)
+{
+	struct Program program;
+	program.consts = NULL;
+	program.const_count = 0;
+	program.const_capacity = 0;
+	return program;
+}
+
+void free_program(struct Program* program)
+{
+	free(program->consts);
+	program->consts = NULL;
+	program->const_count = 0;
+	program->const_capacity = 0;
+}
+
+void add_const(struct Program* program, struct ConstDecl decl)
+{
+	if (program->const_count == program->const_capacity)
+	{
+		size_t capacity = program->const_capacity < 8 ? 8 : program->const_capacity * 2;
+		program->consts = realloc(program->consts, capacity * sizeof(struct ConstDecl));
+		program->const_capacity = capacity;
+	}
+
+	program->consts[program->const_count] = decl;
+	program->const_count += 1;
+}
diff --git a/src/parser/ast.h b/src/parser/ast.h
new file mode 100644
index 0000000..7079305
--- /dev/null
+++ b/src/parser/ast.h
@@ -0,0 +1,22 @@
+#pragma once
+
+#include <stddef.h>
+
+#include "lexer/lexer.h"
+
+struct ConstDecl
+{
+	struct Token name;
+	struct Token value;
+};
+
+struct Program
+{
+	struct ConstDecl* consts;
+	size_t const_count;
+	size_t const_capacity;
+};
+
+struct Program create_program(void);
+void free_program(struct Program* program);
+void add_const(struct Program* program, struct ConstDecl decl);
diff --git a/src/parser/parser.c b/src/parser/parser.c
new file mode 100644
index 0000000..5845ad4
--- /dev/null
+++ b/src/parser/parser.c
@@ -0,0 +1,86 @@
+#include <stdio.h>
+
+#include "parser/parser.h"
+
+struct Parser
+{
+	struct Lexer* lexer;
+	struct Token current;
+	struct Token previous;
+	bool had_error;
+};
+
+static void advance_parser(struct Parser* parser)
+{
+	parser->previous = parser->current;
+	parser->current = scan_token(parser->lexer);
+}
+
+static bool check(struct Parser* parser, enum TokenType type)
+{
+	return parser->current.type == type;
+}
+
+static void error_at(struct Parser* parser, struct Token token, const char* message)
+{
+	fprintf(stderr, "error: line %u: %s\n", token.line, message);
+	parser->had_error = true;
+}
+
+static bool consume(struct Parser* parser, enum TokenType type, const char* message)
+{
+	if (check(parser, type))
+	{
+		advance_parser(parser);
+		return true;
+	}
+
+	error_at(parser, parser->current, message);
+	return false;
+}
+
+static bool parse_const(struct Parser* parser, struct Program* program)
+{
+	struct ConstDecl decl;
+
+	if (!consume(parser, TOKEN_IDENTIFIER, "expected constant name after 'const'"))
+		return false;
+	decl.name = parser->previous;
+
+	if (!consume(parser, TOKEN_EQUAL, "expected '=' after constant name"))
+		return false;
+
+	if (!consume(parser, TOKEN_INTEGER, "expected integer value after '='"))
+		return false;
+	decl.value = parser->previous;
+
+	add_const(program, decl);
+	return true;
+}
+
+bool parse_program(struct Lexer* lexer, struct Program* out)
+{
+	struct Parser parser;
+	parser.lexer = lexer;
+	parser.had_error = false;
+	advance_parser(&parser);
+
+	*out = create_program();
+
+	while (!check(&parser, TOKEN_EOF))
+	{
+		if (check(&parser, TOKEN_CONST))
+		{
+			advance_parser(&parser);
+			if (!parse_const(&parser, out))
+				return false;
+		}
+		else
+		{
+			error_at(&parser, parser.current, "expected a top-level declaration");
+			return false;
+		}
+	}
+
+	return !parser.had_error;
+}
diff --git a/src/parser/parser.h b/src/parser/parser.h
new file mode 100644
index 0000000..82d306a
--- /dev/null
+++ b/src/parser/parser.h
@@ -0,0 +1,8 @@
+#pragma once
+
+#include <stdbool.h>
+
+#include "lexer/lexer.h"
+#include "parser/ast.h"
+
+bool parse_program(struct Lexer* lexer, struct Program* out);