using System.Buffers.Binary;

namespace AcDream.Core.Net.Messages;

/// <summary>
/// Outbound combat attack GameActions.
///
/// Retail/ACE use distinct payloads for melee and missile:
///
/// <code>
///   u32 0xF7B1                   // GameAction envelope opcode
///   u32 gameActionSequence       // client sequence
///   u32 0x0008                   // TargetedMeleeAttack
///   u32 targetGuid
///   u32 attackHeight             // 1=High, 2=Medium, 3=Low
///   f32 powerLevel               // [0.0, 1.0]
///
///   u32 0xF7B1
///   u32 gameActionSequence
///   u32 0x000A                   // TargetedMissileAttack
///   u32 targetGuid
///   u32 attackHeight
///   f32 accuracyLevel            // [0.0, 1.0]
/// </code>
///
/// References: CM_Combat::Event_TargetedMeleeAttack 0x006A9C10,
/// CM_Combat::Event_TargetedMissileAttack 0x006A9D60, ACE
/// GameActionTargetedMeleeAttack/GameActionTargetedMissileAttack, and
/// holtburger protocol game_action.rs.
/// </summary>
public static class AttackTargetRequest
{
    public const uint GameActionEnvelope = 0xF7B1u;
    public const uint TargetedMeleeAttackOpcode = 0x0008u;
    public const uint TargetedMissileAttackOpcode = 0x000Au;
    public const uint CancelAttackOpcode = 0x01B7u;

    /// <summary>Build the wire body for a targeted melee attack.</summary>
    public static byte[] BuildMelee(
        uint gameActionSequence,
        uint targetGuid,
        uint attackHeight,
        float powerLevel)
    {
        byte[] body = new byte[24];
        BinaryPrimitives.WriteUInt32LittleEndian(body,             GameActionEnvelope);
        BinaryPrimitives.WriteUInt32LittleEndian(body.AsSpan(4),   gameActionSequence);
        BinaryPrimitives.WriteUInt32LittleEndian(body.AsSpan(8),   TargetedMeleeAttackOpcode);
        BinaryPrimitives.WriteUInt32LittleEndian(body.AsSpan(12),  targetGuid);
        BinaryPrimitives.WriteUInt32LittleEndian(body.AsSpan(16),  attackHeight);
        BinaryPrimitives.WriteSingleLittleEndian(body.AsSpan(20),  powerLevel);
        return body;
    }

    /// <summary>Build the wire body for a targeted missile attack.</summary>
    public static byte[] BuildMissile(
        uint gameActionSequence,
        uint targetGuid,
        uint attackHeight,
        float accuracyLevel)
    {
        byte[] body = new byte[24];
        BinaryPrimitives.WriteUInt32LittleEndian(body,             GameActionEnvelope);
        BinaryPrimitives.WriteUInt32LittleEndian(body.AsSpan(4),   gameActionSequence);
        BinaryPrimitives.WriteUInt32LittleEndian(body.AsSpan(8),   TargetedMissileAttackOpcode);
        BinaryPrimitives.WriteUInt32LittleEndian(body.AsSpan(12),  targetGuid);
        BinaryPrimitives.WriteUInt32LittleEndian(body.AsSpan(16),  attackHeight);
        BinaryPrimitives.WriteSingleLittleEndian(body.AsSpan(20),  accuracyLevel);
        return body;
    }

    /// <summary>Build the wire body for cancelling an active attack request.</summary>
    public static byte[] BuildCancel(uint gameActionSequence)
    {
        byte[] body = new byte[12];
        BinaryPrimitives.WriteUInt32LittleEndian(body,           GameActionEnvelope);
        BinaryPrimitives.WriteUInt32LittleEndian(body.AsSpan(4), gameActionSequence);
        BinaryPrimitives.WriteUInt32LittleEndian(body.AsSpan(8), CancelAttackOpcode);
        return body;
    }
}