#version 450

#extension GL_EXT_control_flow_attributes : require

#define BLOCK_SIZE 64
layout(local_size_x = BLOCK_SIZE, local_size_y = 1, local_size_z = 1) in;

layout(push_constant) uniform Parameters {
    uint B;
    uint T;
    uint C;
    uint H;
    float scale;
};

layout(binding = 0) readonly buffer KBuf { A_TYPE k[]; };
layout(binding = 1) readonly buffer VBuf { A_TYPE v[]; };
layout(binding = 2) readonly buffer QBuf { A_TYPE q[]; };
layout(binding = 3) readonly buffer GBuf { A_TYPE g[]; };
layout(binding = 4) readonly buffer StateBuf { A_TYPE state_in[]; };
layout(binding = 5) buffer DstBuf { A_TYPE dst[]; };

shared A_TYPE _k[BLOCK_SIZE], _q[BLOCK_SIZE], _g[BLOCK_SIZE];

void main() {
    const uint head_size = BLOCK_SIZE;
    const uint batch_id = gl_WorkGroupID.x / H;
    const uint head_id = gl_WorkGroupID.x % H;
    const uint tid = gl_LocalInvocationID.x;

    const uint state_size = C * head_size;
    const uint n_seq_tokens = T / B;

    if (batch_id >= B || head_id >= H) {
        return;
    }

    // state[i] holds column tid of this head's state matrix: S[i][tid]
    A_TYPE state[BLOCK_SIZE];
    [[unroll]] for (uint i = 0; i < head_size; i++) {
        state[i] = state_in[batch_id * state_size + head_id * head_size * head_size
                          + i * head_size + tid];
    }

    const uint start_t = batch_id * n_seq_tokens * C + head_id * head_size + tid;
    const uint end_t = (batch_id + 1) * n_seq_tokens * C + head_id * head_size + tid;

    for (uint t = start_t; t < end_t; t += C) {
        barrier();
        _k[tid] = k[t];
        _q[tid] = q[t];
        _g[tid] = g[t];
        barrier();

        const A_TYPE v_val = v[t];
        A_TYPE y = 0.0;

        [[unroll]] for (uint i = 0; i < head_size; i += 4) {
            vec4 k_vec = vec4(_k[i], _k[i+1], _k[i+2], _k[i+3]);
            vec4 q_vec = vec4(_q[i], _q[i+1], _q[i+2], _q[i+3]);
            vec4 g_vec = vec4(_g[i], _g[i+1], _g[i+2], _g[i+3]);
            vec4 s_vec = vec4(state[i], state[i+1], state[i+2], state[i+3]);

            vec4 kv = k_vec * v_val;

            s_vec = s_vec * g_vec + kv;
            y += dot(q_vec, s_vec);

            state[i]   = s_vec.x;
            state[i+1] = s_vec.y;
            state[i+2] = s_vec.z;
            state[i+3] = s_vec.w;
        }

        dst[t] = y * scale;
    }

    [[unroll]] for (uint i = 0; i < head_size; i++) {
        dst[T * C + batch_id * state_size + head_id * head_size * head_size
            + i * head_size + tid] = state[i];
    }
}