Advanced Context & Parsing

When manually writing codecs for map structures, checking Optional returns and appending DataResult error paths can become verbose. AbyssalLib provides DecodeContext and EncodeContext to streamline this process by wrapping map operations in a fluent API that automatically collects errors and warnings.

Decoding Maps

DecodeContext wraps a deserialized map node. It allows you to sequentially read keys, apply their respective codecs, and pass the resulting values into a callback function.

If a required key is missing, or if a codec fails, the context logs a DataError internally. Calling .result() returns a single DataResult containing all collected issues, or DataResult.success(null) if parsing succeeded.

public class CustomData {
    private final String name;
    private final int count;

    public CustomData(String name, int count) {
        this.name = name;
        this.count = count;
    }

    public String getName() { return name; }
    public int getCount() { return count; }

    public static final Codec<CustomData> CODEC = Codec.of(
        new Codec.Decoder<CustomData>() {
            @Override
            public <D> DataResult<CustomData> decode(DynamicOps<D> ops, D input) {
                var mapOpt = ops.getMap(input);
                if (mapOpt.isEmpty()) return DataResult.error("Expected a map object");
                
                // Prepare variables to hold the parsed data
                String[] name = new String[1];
                int[] count = new int[1];
                
                // Parse the map sequentially
                DataResult<Void> validation = DecodeContext.of(ops, mapOpt.get())
                    // Reads a required key
                    .read("name", Codecs.STRING, val -> name[0] = val)
                    
                    // Reads an optional key, providing a default if missing
                    .readOrElse("count", Codecs.INT, 1, val -> count[0] = val)
                    
                    // Finish and get the combined result
                    .result();
                    
                // If validation failed, return the error
                if (validation.isError()) {
                    return DataResult.error(validation.dataError().get());
                }
                
                return DataResult.success(new CustomData(name[0], count[0]));
            }
        },
        // ... Encoder logic below ...

Encoding Maps

Similarly, EncodeContext simplifies building a new serialized map by chaining write operations. If a null value is passed or a codec fails to encode, it automatically logs the error to the context.

        // ... Decoder logic above ...
        new Codec.Encoder<CustomData>() {
            @Override
            public <D> DataResult<D> encode(DynamicOps<D> ops, CustomData value) {
                return EncodeContext.of(ops)
                    .write("name", Codecs.STRING, value.getName())
                    // Only writes the count if it is not the default value of 1
                    .writeOrElse("count", Codecs.INT, value.getCount(), 1)
                    .result();
            }
        }
    );
}

05 June 2026