"""
GLADIUS — Synthase Transformer Layer

Drop-in replacement for TransformerLayer that adds ATP synthase depth attention
as a separate residual stream (peripheral stalk principle).

Architecture:
    x_normed = RMSNorm(x)
    O_backbone = backbone_attention(x_normed, mask)    ← F1 hexamer (stable)
    O_depth = synthase_depth(Q, x_normed, depth_cache) ← FO motor (depth)
    x = x + O_backbone + depth_scale * O_depth         ← peripheral stalk
    x = x + FFN(RMSNorm(x))

The backbone attention is UNCHANGED. The depth attention is purely additive.
The backbone can learn to ignore depth (O_depth → 0 via gate).
The depth can learn to contribute (gate → 1, depth_scale grows).
Neither is forced. Both have fair initial conditions.

Authors: Ali A. Shakil, Ava Shakil
Date: March 27, 2026
"""

import torch
import torch.nn as nn
import math
from typing import Optional

from .synthase_attention import SynthaseDepthAttention


class SynthaseTransformerLayer(nn.Module):
    """
    Transformer layer with ATP synthase-inspired depth attention.
    
    Compatible with GLADIUS Omega kernel (HybridAttention + SwiGLU + RMSNorm).
    """
    
    def __init__(
        self,
        # These will be set by the existing layer's components
        attention: nn.Module,     # HybridAttention (backbone)
        ffn: nn.Module,           # SwiGLU
        attn_norm: nn.Module,     # RMSNorm
        ffn_norm: nn.Module,      # RMSNorm
        # Synthase-specific config
        hidden_dim: int = 640,
        num_heads: int = 20,
        head_dim: int = 32,
        num_depth_kv_heads: int = 4,
        depth_k: int = 32,
        max_depth_layers: int = 14,
        layer_idx: int = 0,
        qk_softcap: Optional[float] = None,
        use_bottleneck: bool = False,
        bottleneck_dim: int = 128,
    ):
        super().__init__()
        self.layer_idx = layer_idx
        
        # Backbone components (transferred from existing layer — NOT new)
        self.attention = attention
        self.ffn = ffn
        self.attn_norm = attn_norm
        self.ffn_norm = ffn_norm
        
        # === NEW: Synthase depth attention (the ATP synthase motor) ===
        self.depth_attention = SynthaseDepthAttention(
            hidden_dim=hidden_dim,
            num_heads=num_heads,
            head_dim=head_dim,
            num_depth_kv_heads=num_depth_kv_heads,
            depth_k=depth_k,
            max_depth_layers=max_depth_layers,
            qk_softcap=qk_softcap,
            use_bottleneck=use_bottleneck,
            bottleneck_dim=bottleneck_dim,
        )
        
        # Depth residual scale — starts at 0.1 (pump mode)
        # Learnable: grows as depth becomes useful (→ production mode)
        # Can go negative (depth as inhibitor — removing info is also useful)
        self.depth_scale = nn.Parameter(torch.tensor(0.1))
    
    def forward(
        self,
        x: torch.Tensor,
        mask: Optional[torch.Tensor] = None,
        depth_cache: Optional[torch.Tensor] = None,
    ) -> torch.Tensor:
        """
        Forward with separate backbone + depth residual streams.
        
        Args:
            x: (B, S, D) — input hidden state
            mask: causal mask
            depth_cache: (B, D_len, D) — depth cache from DepthCacheBuilder
        Returns:
            x: (B, S, D) — output with depth contribution
        """
        x_normed = self.attn_norm(x)
        
        # === Backbone attention (F1 hexamer — stable, well-trained) ===
        O_backbone = self.attention(x_normed, mask=mask)
        
        # === Depth attention (FO motor — learning to couple) ===
        if depth_cache is not None and depth_cache.shape[1] > 0:
            # Extract un-rotated Q from backbone for depth cross-attention
            B, S, D = x_normed.shape
            Q = self.attention.q_proj(x_normed)
            Q = Q.view(B, S, self.attention.num_heads, self.attention.head_dim).transpose(1, 2)
            # Note: we use UN-ROTATED Q for depth attention.
            # Depth has its own positional encoding (layer index, not sequence position).
            # RoPE is for sequence-axis positioning only.
            
            O_depth = self.depth_attention(Q, x_normed, depth_cache)
            
            # Peripheral stalk: separate residual streams, both additive
            x = x + O_backbone + self.depth_scale * O_depth
        else:
            x = x + O_backbone
        
        # FFN (unchanged)
        x = x + self.ffn(self.ffn_norm(x))
        return x
    
    def get_depth_diagnostics(self, x: torch.Tensor, depth_cache: Optional[torch.Tensor] = None) -> dict:
        """Get diagnostics for monitoring depth attention health."""
        diag = {
            'depth_scale': self.depth_scale.item(),
            'layer_idx': self.layer_idx,
        }
        if depth_cache is not None and depth_cache.shape[1] > 0:
            x_normed = self.attn_norm(x)
            gate_diag = self.depth_attention.get_diagnostics(x_normed)
            diag.update(gate_diag)
        return diag