using System.IO;
using System.Text;
using WasmBox.Wasm.Binary;

namespace WasmBox.Wasm.Instructions {
    /// <summary>
    /// Describes a WebAssembly stack machine instruction.
    /// </summary>
    public abstract class Instruction {
        /// <summary>
        /// Creates an instruction.
        /// </summary>
        public Instruction() { }

        /// <summary>
        /// Gets the operator for this instruction.
        /// </summary>
        /// <returns>The instruction's operator.</returns>
        public abstract Operator Op { get; }

        /// <summary>
        /// Writes this instruction's immediates (but not its opcode)
        /// to the given WebAssembly file writer.
        /// </summary>
        /// <param name="writer">The writer to write this instruction's immediates to.</param>
        public abstract void WriteImmediatesTo(BinaryWasmWriter writer);

        /// <summary>
        /// Writes this instruction's opcode and immediates to the given
        /// WebAssembly file writer.
        /// </summary>
        /// <param name="writer">The writer to write this instruction to.</param>
        public void WriteTo(BinaryWasmWriter writer) {
            writer.Writer.Write(Op.OpCode);
            WriteImmediatesTo(writer);
        }

        /// <summary>
        /// Writes a string representation of this instruction to the given text writer.
        /// </summary>
        /// <param name="writer">
        /// The writer to which a representation of this instruction is written.
        /// </param>
        public virtual void Dump(TextWriter writer) {
            Op.Dump(writer);
        }

        /// <summary>
        /// Creates a string representation of this instruction.
        /// </summary>
        /// <returns>The instruction's string representation.</returns>
        public override string ToString() {
            var builder = new StringBuilder();
            Dump(new StringWriter(builder));
            return builder.ToString();
        }
    }
}