Day 10: remove errors

Signed-off-by: Aaron Fischer <mail@aaron-fischer.net>

src/main.zig

@@ -3,27 +3,46 @@ const builtin = @import("builtin");
 const eql = @import("std").mem.eql;
 
 const stdout = std.io.getStdOut().writer();
+const stderr = std.io.getStdErr().writer();
 const stdin = std.io.getStdIn().reader();
 
+const Target = enum {
+    Stdout,
+    Stderr,
+};
+
+pub fn write(target: Target, comptime format: []const u8, args: anytype) void {
+    switch (target) {
+        Target.Stdout => stdout.print(format, args) catch |err| {
+            std.debug.panic("unable to write to output: {any}\n", .{err});
+        },
+        Target.Stderr => stderr.print(format, args) catch |err| {
+            std.debug.panic("unable to write to output: {any}\n", .{err});
+        },
+    }
+}
+
 pub fn main() !void {
     // Read the first argument to determine the subcommand
     const allocator = std.heap.page_allocator;
-    var args = try std.process.argsWithAllocator(allocator);
+    var args = std.process.argsWithAllocator(allocator) catch |err| {
+        write(Target.Stderr, "out of memory: {any}\n", .{err});
+    };
     defer args.deinit();
 
     _ = args.next(); // Skip the first argument, which is the program name
 
     const firstArg = args.next() orelse {
-        try stdout.print("No subcommand provided\n", .{});
+        write(Target.Stderr, "no subcommand provided\n", .{});
         return;
     };
 
     if (eql(u8, firstArg, "list")) {
-        try listEntries();
+        listEntries();
     } else if (eql(u8, firstArg, "create")) {
         try createNewEntry();
     } else {
-        try stdout.print("Unknown subcommand: {s}\n", .{firstArg});
+        write(Target.Stderr, "Unknown subcommand: {any}\n", .{firstArg});
     }
 }
 
@@ -58,16 +77,22 @@ fn createNewEntry() !void {
     try stdout.print("=> / Back to the log entries", .{});
 }
 
-fn listEntries() !void {
-    const file = try std.fs.cwd().openFile("entries.log.gmi", .{});
+fn listEntries() void {
+    const file = std.fs.cwd().openFile("entries.log.gmi", .{}) catch |err| {
+        write(Target.Stderr, "unable to open file: {any}\n", .{err});
+        return;
+    };
     defer file.close();
 
     var bufReader = std.io.bufferedReader(file.reader());
     var inStream = bufReader.reader();
 
     var buf: [1024]u8 = undefined;
-    while (try inStream.readUntilDelimiterOrEof(&buf, '\n')) |line| {
-        try stdout.print("{s}\n", .{ line });
+
+    while (inStream.readUntilDelimiterOrEof(&buf, '\n')) |line| {
+        write(Target.Stdout, "{s}\n", .{ line orelse break });
+    } else |err| {
+        write(Target.Stderr, "error while reading the file: {!}\n", .{err});
     }
 }