1 files changed, 197 insertions, 0 deletions
diff --git a/src/argument.zig b/src/argument.zig
new file mode 100644
index 0000000..fa9612d
--- /dev/null
+++ b/src/argument.zig
@@ -0,0 +1,197 @@
+const std = @import("std");
+pub const Grammar = @import("grammar.zig");
+
+fn help(err: ?anyerror) noreturn {
+	const stderr = std.io.getStdErr().writer();
+
+	if (err) |e| {
+		stderr.print("error: {s}\n", .{@errorName(e)}) catch unreachable;
+	}
+
+	stderr.writeAll(
+		\\mry [command] [options]
+		\\
+		\\Commands:
+		\\
+		\\  generate [grammar] [options]
+		\\       Options:
+		\\         -o, --output entry  Output string to file
+		\\                             By default stdout will be used.
+		\\
+		\\         -c, --count n       Number of texts to generate. (default: 1)
+		\\
+		\\         -n, --non-empty     Only output texts which are non-empty.
+		\\
+		\\  recognize [grammar] [options]
+		\\       Options:
+		\\         -i, --input entry   Specify input source, if the path
+		\\                             points to a directory it will scan
+		\\                             all files in it. By default stdin will
+		\\                             be used as input.
+		\\
+		\\General Options
+		\\  -h, --help                 Print usage
+		\\
+	) catch unreachable;
+	std.process.exit(@intFromBool(err != null));
+}
+
+fn check(arg_or_null: ?[]const u8) []const u8 {
+	const arg = arg_or_null orelse help(error.MissingArgument);
+
+	if (std.mem.eql(u8, arg, "-h") or std.mem.eql(u8, arg, "--help")) {
+		help(null);
+	}
+	return arg;
+}
+
+fn parse_enum(T: type, arg: []const u8) T {
+	return std.meta.stringToEnum(T, arg) orelse help(error.InvalidArgument);
+}
+
+fn parse_int(n: []const u8) usize {
+	return std.fmt.parseInt(usize, n, 10) catch |e| help(e);
+}
+
+fn check_flags(arg: []const u8, comptime flags: []const []const u8) bool {
+	inline for (flags) |flag| {
+		if (std.mem.eql(u8, arg, flag)) {
+			return true;
+		}
+	}
+
+	return false;
+}
+
+pub const Mode = enum {
+	recognize,
+	generate,
+};
+
+pub const Entry = struct {
+	const Self = @This();
+
+	name: []const u8,
+	file: std.fs.File,
+
+	pub fn open(path: []const u8) Self {
+		var cwd = std.fs.cwd();
+
+		return Self {
+			.name = path,
+			.file = cwd.openFile(path, .{}) catch |e| help(e)
+		};
+	}
+
+	pub fn read_file(path: []const u8, allocator: std.mem.Allocator) []const u8 {
+		var cwd = std.fs.cwd();
+
+		var file = cwd.openFile(path, .{}) catch |e| help(e);
+		defer file.close();
+		const stat = file.stat() catch |e| help(e);
+
+		return file.readToEndAlloc(allocator, stat.size) catch |e| help(e);
+	}
+
+	pub fn stdin() Self {
+		return Self {
+			.name = "[stdin]",
+			.file = std.io.getStdIn(),
+		};
+	}
+
+	pub fn stdout() Self {
+		return Self {
+			.name = "[stdout]",
+			.file = std.io.getStdOut(),
+		};
+	}
+};
+
+pub const RecognizeArgs = struct {
+	input: Entry,
+	grammar: Grammar,
+};
+
+pub const GenerateArgs = struct {
+	count: usize,
+	empty: bool,
+	output: Entry,
+	grammar: Grammar,
+};
+
+pub const Args = union(Mode) {
+	const Self = @This();
+
+	recognize: RecognizeArgs,
+	generate: GenerateArgs,
+
+	pub fn parse(allocator: std.mem.Allocator) Self {
+		var args = std.process.args();
+		_ = args.next();
+
+		const mode = parse_enum(Mode, check(args.next()));
+
+		const text = Entry.read_file(check(args.next()), allocator);
+		defer allocator.free(text);
+		const grammar = Grammar.parse(
+			text,
+			allocator
+		) catch |e| help(e);
+
+		switch (mode) {
+			.recognize => {
+				var input: ?Entry = null;
+
+				while (args.next()) |arg| {
+					if (check_flags(arg, &[_][]const u8 { "-i", "--input" })) {
+						input = Entry.open(check(args.next()));
+					} else help(error.InvalidArgument);
+				}
+
+				return Self {
+					.recognize = .{
+						.input = input orelse Entry.stdin(),
+						.grammar = grammar,
+					},
+				};
+			},
+
+			.generate => {
+				var count: usize = 1;
+				var output: ?Entry = null;
+				var empty: bool = true;
+
+				while (args.next()) |arg| {
+					if (check_flags(arg, &[_][]const u8 { "-o", "--output" })) {
+						output = Entry.open(check(args.next()));
+					} else if (check_flags(arg, &[_][]const u8 { "-c", "--count" })) {
+						count = parse_int(check(args.next()));
+					} else if (check_flags(arg, &[_][]const u8 { "-n", "--non-empty" })) {
+						empty = false;
+					} else help(error.InvalidArgument);
+				}
+
+				return Self {
+					.generate = .{
+						.count = count,
+						.empty = empty,
+						.output = output orelse Entry.stdout(),
+						.grammar = grammar,
+					},
+				};
+			},
+		}
+	}
+
+	pub fn deinit(self: *Self, allocator: std.mem.Allocator) void {
+		switch (self.*) {
+			.recognize => |*rec| {
+				rec.grammar.deinit(allocator);
+			},
+			.generate => |*gen| {
+				gen.grammar.deinit(allocator);
+			}
+		}
+	}
+};