namespace WhiteMagic.Assembly;

/// <summary>
/// The default <see cref="IAssembler"/> backend. Hand-emits calling-convention
/// trampolines and injection stubs using deterministic byte emitters
/// (<see cref="EmitU8"/>, <see cref="EmitU32"/>, <see cref="EmitU64"/>). Has
/// no native or third-party dependency — no FASM, no Iced.
/// </summary>
/// <remarks>
/// <see cref="Assemble"/> is not supported by this backend (it is a parse-free
/// emitter, not a text assembler). Use <see cref="IcedAssembler"/> (Phase 8) for
/// arbitrary mnemonics.
/// </remarks>
public class StubAssembler : IAssembler
{
    /// <inheritdoc />
    /// <exception cref="NotSupportedException">Always thrown. StubAssembler does
    /// not parse text assembly; use IcedAssembler for that.</exception>
    public byte[] Assemble(string assemblyText, ulong origin = 0)
    {
        throw new NotSupportedException(
            "StubAssembler does not parse text assembly. " +
            "Use IcedAssembler (Phase 8) for arbitrary mnemonics.");
    }

    // ── Emit primitives ────────────────────────────────────────────────────

    /// <summary>Appends a single byte to <paramref name="buffer"/>.</summary>
    public void EmitU8(List<byte> buffer, byte value)
    {
        buffer.Add(value);
    }

    /// <summary>Appends <paramref name="value"/> as 4 little-endian bytes.</summary>
    public void EmitU32(List<byte> buffer, uint value)
    {
        buffer.Add((byte)value);
        buffer.Add((byte)(value >> 8));
        buffer.Add((byte)(value >> 16));
        buffer.Add((byte)(value >> 24));
    }

    /// <summary>Appends <paramref name="value"/> as 8 little-endian bytes.</summary>
    public void EmitU64(List<byte> buffer, ulong value)
    {
        EmitU32(buffer, (uint)value);
        EmitU32(buffer, (uint)(value >> 32));
    }
}