using System.Buffers.Binary;

namespace AcDream.Core.Net.Messages;

/// <summary>
/// Outbound interaction GameActions. Each carries a single uint32
/// target guid (plus a second guid for <c>UseWithTarget</c>) inside the
/// standard <c>0xF7B1</c> GameAction envelope.
///
/// <para>
/// Wire layout (r08 §3 rows 0x0035/0x0036):
/// <code>
///   u32 0xF7B1
///   u32 gameActionSequence
///   u32 subOpcode
///   u32 targetGuid        // e.g. door, NPC, lifestone, corpse, item
///   u32 sourceGuid        // only for UseWithTarget (the item you're using)
/// </code>
/// </para>
///
/// <para>
/// Server reply is <c>GameEventType.UseDone</c> (0x01C7) carrying a
/// <c>WeenieError</c>; 0 = success.
/// </para>
/// </summary>
public static class InteractRequests
{
    public const uint GameActionEnvelope = 0xF7B1u;
    public const uint UseOpcode = 0x0036u;
    public const uint UseWithTargetOpcode = 0x0035u;
    public const uint TeleToLifestoneOpcode = 0x0063u;
    public const uint PutItemInContainerOpcode = 0x0019u;

    /// <summary>
    /// Use an object: click a door, loot a corpse, talk to an NPC,
    /// activate a lifestone, step onto a portal.
    /// </summary>
    public static byte[] BuildUse(uint gameActionSequence, uint targetGuid)
    {
        byte[] body = new byte[16];
        BinaryPrimitives.WriteUInt32LittleEndian(body,            GameActionEnvelope);
        BinaryPrimitives.WriteUInt32LittleEndian(body.AsSpan(4),  gameActionSequence);
        BinaryPrimitives.WriteUInt32LittleEndian(body.AsSpan(8),  UseOpcode);
        BinaryPrimitives.WriteUInt32LittleEndian(body.AsSpan(12), targetGuid);
        return body;
    }

    /// <summary>
    /// Use source item on target: e.g. key on locked door, key on
    /// chest, scroll on yourself, salvage tool on an item.
    /// </summary>
    public static byte[] BuildUseWithTarget(
        uint gameActionSequence, uint sourceGuid, uint targetGuid)
    {
        byte[] body = new byte[20];
        BinaryPrimitives.WriteUInt32LittleEndian(body,            GameActionEnvelope);
        BinaryPrimitives.WriteUInt32LittleEndian(body.AsSpan(4),  gameActionSequence);
        BinaryPrimitives.WriteUInt32LittleEndian(body.AsSpan(8),  UseWithTargetOpcode);
        BinaryPrimitives.WriteUInt32LittleEndian(body.AsSpan(12), sourceGuid);
        BinaryPrimitives.WriteUInt32LittleEndian(body.AsSpan(16), targetGuid);
        return body;
    }

    /// <summary>
    /// Teleport to your lifestone. No target guid — just tells the
    /// server "recall me." Fails if you haven't tied to a lifestone
    /// (server responds with a WeenieError).
    /// </summary>
    public static byte[] BuildTeleToLifestone(uint gameActionSequence)
    {
        byte[] body = new byte[12];
        BinaryPrimitives.WriteUInt32LittleEndian(body,            GameActionEnvelope);
        BinaryPrimitives.WriteUInt32LittleEndian(body.AsSpan(4),  gameActionSequence);
        BinaryPrimitives.WriteUInt32LittleEndian(body.AsSpan(8),  TeleToLifestoneOpcode);
        return body;
    }

    /// <summary>
    /// Pick up a ground item or move an item between containers. The
    /// server places the item in <paramref name="containerGuid"/> at
    /// the given <paramref name="placement"/> slot (pass 0 to let the
    /// server choose). For F-key ground-pickup, pass the player's own
    /// server guid as <paramref name="containerGuid"/>.
    ///
    /// <para>
    /// Wire layout (ACE GameActionPutItemInContainer.Handle):
    /// <code>
    ///   u32 0xF7B1
    ///   u32 gameActionSequence
    ///   u32 0x0019                 // PutItemInContainer
    ///   u32 itemGuid               // server guid of the item
    ///   u32 containerGuid          // destination container (player or bag)
    ///   i32 placement              // 0 = server picks slot
    /// </code>
    /// </para>
    /// </summary>
    public static byte[] BuildPickUp(
        uint gameActionSequence, uint itemGuid, uint containerGuid, int placement)
    {
        byte[] body = new byte[24];
        BinaryPrimitives.WriteUInt32LittleEndian(body,            GameActionEnvelope);
        BinaryPrimitives.WriteUInt32LittleEndian(body.AsSpan(4),  gameActionSequence);
        BinaryPrimitives.WriteUInt32LittleEndian(body.AsSpan(8),  PutItemInContainerOpcode);
        BinaryPrimitives.WriteUInt32LittleEndian(body.AsSpan(12), itemGuid);
        BinaryPrimitives.WriteUInt32LittleEndian(body.AsSpan(16), containerGuid);
        BinaryPrimitives.WriteInt32LittleEndian (body.AsSpan(20), placement);
        return body;
    }
}