from __future__ import annotations
import math
from dataclasses import dataclass
import torch
import torch.nn as nn
import torch.nn.functional as F
import importlib.util as _ilu
import sys as _sys
from pathlib import Path as _Path
_UNIFIED_NAME = 'unified_cfm_model'
if _UNIFIED_NAME not in _sys.modules:
    _unified_spec = _ilu.spec_from_file_location(_UNIFIED_NAME, _Path(__file__).resolve().parents[1] / 'Unified_CFM' / 'model.py')
    _unified = _ilu.module_from_spec(_unified_spec)
    _sys.modules[_UNIFIED_NAME] = _unified
    _unified_spec.loader.exec_module(_unified)
else:
    _unified = _sys.modules[_UNIFIED_NAME]
AdaLNBlock = _unified.AdaLNBlock
SinusoidalTimeEmb = _unified.SinusoidalTimeEmb
_sinkhorn_coupling = _unified._sinkhorn_coupling


@dataclass
class MixedCFMConfig:
    T: int = 64
    flow_dim: int = 20
    n_cont_pkt: int = 3
    n_disc_pkt: int = 6
    cont_pkt_idx: tuple[int, ...] = (0, 1, 8)
    disc_pkt_idx: tuple[int, ...] = (2, 3, 4, 5, 6, 7)
    n_disc_classes: int = 2
    token_dim: int | None = None
    d_model: int = 128
    n_layers: int = 4
    n_heads: int = 4
    mlp_ratio: float = 4.0
    time_dim: int = 64
    sigma: float = 0.1
    use_ot: bool = False
    reference_mode: str | None = None
    lambda_disc: float = 1.0
    disc_path: str = 'uniform'
    disc_embed_scale: float = 1.0
    # ---- B-group ablation flags (defaults preserve JANUS-full behavior) ----
    use_flow_token: bool = True       # B1: False removes the [FLOW] token
    n_packet_tokens: int = -1         # B2: 0 removes packet tokens entirely; -1 = use cfg.T
    disc_as_cont: bool = False        # B3: feed 6 disc bits through CFM head as continuous values
    cont_as_disc: bool = False        # B4: quantize 3 cont channels into n_disc_classes bins (mask-pred only)

    def __post_init__(self) -> None:
        if len(self.cont_pkt_idx) != self.n_cont_pkt:
            raise ValueError('cont_pkt_idx length mismatch n_cont_pkt')
        if len(self.disc_pkt_idx) != self.n_disc_pkt:
            raise ValueError('disc_pkt_idx length mismatch n_disc_pkt')
        if self.disc_path != 'uniform':
            raise NotImplementedError(f'disc_path={self.disc_path}')
        if self.disc_as_cont and self.cont_as_disc:
            raise ValueError('disc_as_cont and cont_as_disc are mutually exclusive')


class MixedVelocity(nn.Module):

    def __init__(self, token_dim: int, seq_len: int, n_disc: int, n_classes: int, d_model: int=128, n_layers: int=4, n_heads: int=4, mlp_ratio: float=4.0, time_dim: int=64, reference_mode: str | None=None, has_flow_token: bool=True) -> None:
        super().__init__()
        if reference_mode not in (None, 'causal_packets', 'causal_all'):
            raise ValueError(f'reference_mode={reference_mode!r}')
        self.token_dim = token_dim
        self.seq_len = seq_len
        self.n_disc = n_disc
        self.n_classes = n_classes
        self.reference_mode = reference_mode
        self.has_flow_token = has_flow_token
        self.input_proj = nn.Linear(token_dim, d_model)
        self.pos_emb = nn.Parameter(torch.zeros(1, seq_len, d_model))
        self.type_emb = nn.Embedding(2, d_model)
        nn.init.trunc_normal_(self.pos_emb, std=0.02)
        nn.init.normal_(self.type_emb.weight, std=0.02)
        self.time_emb = SinusoidalTimeEmb(time_dim)
        self.cond_mlp = nn.Sequential(nn.Linear(time_dim, d_model), nn.SiLU(), nn.Linear(d_model, d_model))
        self.blocks = nn.ModuleList([AdaLNBlock(d_model, n_heads, mlp_ratio, cond_dim=d_model) for _ in range(n_layers)])
        self.out_norm = nn.LayerNorm(d_model, elementwise_affine=False)
        self.head_v = nn.Linear(d_model, token_dim)
        # head_disc only meaningful when n_disc > 0
        out_disc = max(n_disc * n_classes, 1)
        self.head_disc = nn.Linear(d_model, out_disc)
        for layer in (self.head_v, self.head_disc):
            nn.init.zeros_(layer.weight)
            nn.init.zeros_(layer.bias)
        type_ids = torch.ones(seq_len, dtype=torch.long)
        if has_flow_token and seq_len >= 1:
            type_ids[0] = 0
        self.register_buffer('type_ids', type_ids, persistent=False)

    def _attn_mask(self, L: int, device: torch.device) -> torch.Tensor | None:
        if self.reference_mode is None:
            return None
        if self.reference_mode == 'causal_packets':
            mask = torch.zeros((L, L), dtype=torch.bool, device=device)
            offset = 1 if self.has_flow_token else 0
            if L > offset:
                M = L - offset
                if M > 1:
                    mask[offset:, offset:] = torch.triu(torch.ones(M, M, dtype=torch.bool, device=device), diagonal=1)
            return mask
        return torch.triu(torch.ones(L, L, dtype=torch.bool, device=device), diagonal=1)

    def forward(self, x: torch.Tensor, t: torch.Tensor, key_padding_mask: torch.Tensor | None=None) -> tuple[torch.Tensor, torch.Tensor]:
        (B, L, _) = x.shape
        if t.dim() == 0:
            t = t.expand(B)
        h = self.input_proj(x)
        h = h + self.pos_emb[:, :L, :] + self.type_emb(self.type_ids[:L])[None, :, :]
        cond = self.cond_mlp(self.time_emb(t))
        attn_mask = self._attn_mask(L, x.device)
        for block in self.blocks:
            h = block(h, cond, key_padding_mask, attn_mask=attn_mask)
        h = self.out_norm(h)
        v = self.head_v(h)
        if self.n_disc > 0:
            d = self.head_disc(h).view(B, L, self.n_disc, self.n_classes)
        else:
            d = h.new_zeros((B, L, 0, self.n_classes))
        return (v, d)


class MixedTokenCFM(nn.Module):

    def __init__(self, cfg: MixedCFMConfig) -> None:
        super().__init__()
        self.cfg = cfg
        # Effective packet count (B2: n_packet_tokens=0 → no packets)
        self.eff_T = cfg.T if cfg.n_packet_tokens < 0 else int(cfg.n_packet_tokens)
        if not cfg.use_flow_token and self.eff_T == 0:
            raise ValueError('cannot disable both FLOW token and packet tokens')
        # Effective per-packet feature split
        if cfg.disc_as_cont:
            # B3: 9 cont, 0 disc (CFM head only)
            self.eff_n_cont = cfg.n_cont_pkt + cfg.n_disc_pkt
            self.eff_n_disc = 0
        elif cfg.cont_as_disc:
            # B4: 0 cont, 9 disc (mask-pred head only)
            self.eff_n_cont = 0
            self.eff_n_disc = cfg.n_cont_pkt + cfg.n_disc_pkt
        else:
            self.eff_n_cont = cfg.n_cont_pkt
            self.eff_n_disc = cfg.n_disc_pkt
        cont_size = self.eff_n_cont + self.eff_n_disc
        # Token layout: [type_flag(1) | flow_dim or cont_size]
        self.token_dim = cfg.token_dim or 1 + max(cfg.flow_dim, cont_size)
        if self.token_dim < 1 + max(cfg.flow_dim, cont_size):
            raise ValueError('token_dim too small')
        self.seq_len = (1 if cfg.use_flow_token else 0) + self.eff_T
        self.velocity = MixedVelocity(
            token_dim=self.token_dim, seq_len=self.seq_len,
            n_disc=self.eff_n_disc, n_classes=cfg.n_disc_classes,
            d_model=cfg.d_model, n_layers=cfg.n_layers, n_heads=cfg.n_heads,
            mlp_ratio=cfg.mlp_ratio, time_dim=cfg.time_dim,
            reference_mode=cfg.reference_mode, has_flow_token=cfg.use_flow_token,
        )

    # ------------------------------------------------------------------ #
    # token assembly                                                     #
    # ------------------------------------------------------------------ #
    def _embed_disc(self, x_disc_int: torch.Tensor) -> torch.Tensor:
        n = self.cfg.n_disc_classes
        s = self.cfg.disc_embed_scale
        if n <= 1:
            return x_disc_int.float() * 0.0
        # Map integers in [0, n-1] to centered floats in [-s/2, +s/2].
        # Backwards-compatible with old (x - 0.5)*s formula when n=2.
        return (x_disc_int.float() / (n - 1) - 0.5) * s

    def _flow_dim(self) -> int:
        return self.cfg.flow_dim

    def build_tokens(self, flow: torch.Tensor, packets_cont: torch.Tensor, x_disc_t_int: torch.Tensor) -> torch.Tensor:
        """Assemble [B, seq_len, token_dim].

        packets_cont: [B, eff_T, eff_n_cont] (may be empty in last dim)
        x_disc_t_int: [B, eff_T, eff_n_disc] integer ids in [0, n_disc_classes-1]
        """
        B = flow.shape[0]
        device = flow.device
        T = self.eff_T
        z = flow.new_zeros((B, self.seq_len, self.token_dim))
        cur = 0
        if self.cfg.use_flow_token:
            z[:, 0, 0] = -1.0  # type flag
            z[:, 0, 1:1 + self._flow_dim()] = flow
            cur = 1
        if T > 0:
            z[:, cur:cur + T, 0] = 1.0  # type flag
            base = 1
            if self.eff_n_cont > 0:
                z[:, cur:cur + T, base:base + self.eff_n_cont] = packets_cont
                base += self.eff_n_cont
            if self.eff_n_disc > 0:
                z[:, cur:cur + T, base:base + self.eff_n_disc] = self._embed_disc(x_disc_t_int)
        return z

    def key_padding_mask(self, lens: torch.Tensor) -> torch.Tensor:
        B = lens.shape[0]
        device = lens.device
        T = self.eff_T
        pieces = []
        if self.cfg.use_flow_token:
            pieces.append(torch.ones(B, 1, dtype=torch.bool, device=device))
        if T > 0:
            idx = torch.arange(T, device=device)[None, :]
            pieces.append(idx < lens[:, None])
        real = torch.cat(pieces, dim=1) if pieces else torch.ones(B, 0, dtype=torch.bool, device=device)
        return ~real

    def _loss_mask(self, lens: torch.Tensor) -> torch.Tensor:
        return (~self.key_padding_mask(lens)).float()

    # ------------------------------------------------------------------ #
    # B4 helper: quantize cont -> integer bins                           #
    # ------------------------------------------------------------------ #
    def quantize_cont(self, packets_cont: torch.Tensor, bin_edges: torch.Tensor) -> torch.Tensor:
        """packets_cont [B, T, n_cont_orig] (already z-scored); bin_edges [n_cont_orig, n_classes-1]
        returns int64 [B, T, n_cont_orig] in [0, n_classes-1]."""
        B, T, C = packets_cont.shape
        out = torch.zeros((B, T, C), dtype=torch.long, device=packets_cont.device)
        for c in range(C):
            edges = bin_edges[c]  # [n_classes-1]
            # bucketize: returns 0..n for n edges
            out[:, :, c] = torch.bucketize(packets_cont[:, :, c].contiguous(), edges)
        out.clamp_(0, self.cfg.n_disc_classes - 1)
        return out

    # ------------------------------------------------------------------ #
    # Loss                                                               #
    # ------------------------------------------------------------------ #
    def compute_loss(self, flow: torch.Tensor, packets_cont: torch.Tensor, packets_disc: torch.Tensor, lens: torch.Tensor, *, return_components: bool=False, cont_bin_edges: torch.Tensor | None=None) -> torch.Tensor | dict[str, torch.Tensor]:
        cfg = self.cfg
        B = flow.shape[0]
        T = self.eff_T
        device = flow.device

        # Resolve effective cont/disc tensors per ablation mode
        if cfg.disc_as_cont:
            # 9 cont = original 3 cont + 6 disc-as-float
            disc_as_cont_float = self._embed_disc(packets_disc) if T > 0 else None
            if T > 0:
                eff_cont = torch.cat([packets_cont, disc_as_cont_float], dim=-1) if cfg.n_cont_pkt > 0 else disc_as_cont_float
            else:
                eff_cont = packets_cont.new_zeros((B, 0, 0))
            eff_disc_int = torch.zeros((B, T, 0), dtype=torch.long, device=device)
        elif cfg.cont_as_disc:
            # 0 cont, 9 disc: quantize cont via supplied bin_edges
            if T > 0:
                if cont_bin_edges is None:
                    raise ValueError('cont_as_disc requires cont_bin_edges')
                cont_int = self.quantize_cont(packets_cont, cont_bin_edges)
                eff_disc_int = torch.cat([cont_int, packets_disc.long()], dim=-1)
            else:
                eff_disc_int = torch.zeros((B, 0, self.eff_n_disc), dtype=torch.long, device=device)
            eff_cont = flow.new_zeros((B, T, 0))
        else:
            eff_cont = packets_cont if T > 0 else packets_cont.new_zeros((B, 0, cfg.n_cont_pkt))
            eff_disc_int = packets_disc.long() if T > 0 else torch.zeros((B, 0, cfg.n_disc_pkt), dtype=torch.long, device=device)

        # Build x_1 (data tokens; mask-pred path uses zero ids for disc at packet positions during CFM regression)
        zero_disc = torch.zeros_like(eff_disc_int)
        x_1_cont = self.build_tokens(flow, eff_cont, zero_disc)

        mask = self._loss_mask(lens)
        kpm = mask == 0

        x_0_cont = torch.randn_like(x_1_cont)

        if cfg.use_ot:
            flat0 = (x_0_cont * mask[:, :, None]).reshape(B, -1)
            flat1 = (x_1_cont * mask[:, :, None]).reshape(B, -1)
            col = _sinkhorn_coupling(torch.cdist(flat0.float(), flat1.float()))
            x_1_cont = x_1_cont[col]
            eff_cont = eff_cont[col] if eff_cont.numel() > 0 else eff_cont
            eff_disc_int = eff_disc_int[col] if eff_disc_int.numel() > 0 else eff_disc_int
            packets_disc = packets_disc[col]
            flow = flow[col]
            lens = lens[col]
            mask = self._loss_mask(lens)
            kpm = mask == 0

        t = torch.rand(B, device=device)
        x_t_cont = (1.0 - t[:, None, None]) * x_0_cont + t[:, None, None] * x_1_cont
        if cfg.sigma > 0:
            std = cfg.sigma * torch.sqrt(t * (1.0 - t))[:, None, None]
            x_t_cont = x_t_cont + std * torch.randn_like(x_t_cont)
        target_cont = x_1_cont - x_0_cont

        # Disc corruption schedule (mask-pred): keep fraction t of true labels
        if T > 0 and self.eff_n_disc > 0:
            u = torch.rand(B, T, self.eff_n_disc, device=device)
            keep = u < t[:, None, None]
            rand_disc = torch.randint(0, cfg.n_disc_classes, eff_disc_int.shape, device=device)
            x_disc_t = torch.where(keep, eff_disc_int, rand_disc)
            disc_start = (1 if cfg.use_flow_token else 0) + 0  # placeholder; overwritten below
            # Where in x_t_full do disc embeds go?
            # Within each packet token: [type(1) | cont(eff_n_cont) | disc(eff_n_disc) | pad...]
            disc_start_in_token = 1 + self.eff_n_cont
            cur_offset = 1 if cfg.use_flow_token else 0
            x_t_full = x_t_cont.clone()
            x_t_full[:, cur_offset:cur_offset + T, disc_start_in_token:disc_start_in_token + self.eff_n_disc] = self._embed_disc(x_disc_t)
        else:
            x_t_full = x_t_cont
            x_disc_t = eff_disc_int  # unused
            keep = None

        (v_pred, d_logits) = self.velocity(x_t_full, t, key_padding_mask=kpm)

        # CFM regression loss on cont slots (mask out disc slots)
        v_err = (v_pred - target_cont).square()
        if T > 0 and self.eff_n_disc > 0:
            disc_start_in_token = 1 + self.eff_n_cont
            cur_offset = 1 if cfg.use_flow_token else 0
            v_err[:, cur_offset:cur_offset + T, disc_start_in_token:disc_start_in_token + self.eff_n_disc] = 0.0
        v_per_token = v_err.mean(dim=-1)
        per_sample = (v_per_token * mask).sum(dim=-1) / mask.sum(dim=-1).clamp_min(1.0)
        L_cont = per_sample.mean()

        # Mask-pred CE on corrupted disc positions
        if T > 0 and self.eff_n_disc > 0 and keep is not None:
            cur_offset = 1 if cfg.use_flow_token else 0
            pkt_logits = d_logits[:, cur_offset:cur_offset + T]
            pkt_real = mask[:, cur_offset:cur_offset + T].bool()
            corrupt = ~keep & pkt_real[:, :, None]
            flat_logits = pkt_logits.reshape(-1, cfg.n_disc_classes)
            flat_targets = eff_disc_int.reshape(-1).long()
            flat_ce = F.cross_entropy(flat_logits, flat_targets, reduction='none')
            flat_ce = flat_ce.view(B, T, self.eff_n_disc)
            flat_ce = flat_ce * corrupt.float()
            denom = corrupt.float().sum().clamp_min(1.0)
            L_disc = flat_ce.sum() / denom
        else:
            L_disc = L_cont.new_zeros(())

        total = L_cont + cfg.lambda_disc * L_disc
        if return_components:
            return {'total': total, 'main': L_cont.detach(), 'aux_disc': L_disc.detach(),
                    'aux_flow': L_cont.new_zeros(()), 'aux_packet': L_cont.new_zeros(())}
        return total

    # ------------------------------------------------------------------ #
    # Scoring                                                            #
    # ------------------------------------------------------------------ #
    @torch.no_grad()
    def trajectory_metrics(self, flow: torch.Tensor, packets_cont: torch.Tensor, packets_disc: torch.Tensor, lens: torch.Tensor, n_steps: int=16, cont_bin_edges: torch.Tensor | None=None) -> dict[str, torch.Tensor]:
        cfg = self.cfg
        B = flow.shape[0]
        T = self.eff_T

        # Build effective cont / disc tensors per ablation mode
        if cfg.disc_as_cont:
            disc_float = self._embed_disc(packets_disc) if T > 0 else None
            if T > 0:
                eff_cont = torch.cat([packets_cont, disc_float], dim=-1) if cfg.n_cont_pkt > 0 else disc_float
            else:
                eff_cont = packets_cont.new_zeros((B, 0, 0))
            eff_disc_int = torch.zeros((B, T, 0), dtype=torch.long, device=flow.device)
        elif cfg.cont_as_disc:
            if T > 0:
                if cont_bin_edges is None:
                    raise ValueError('cont_as_disc requires cont_bin_edges at scoring time')
                cont_int = self.quantize_cont(packets_cont, cont_bin_edges)
                eff_disc_int = torch.cat([cont_int, packets_disc.long()], dim=-1)
            else:
                eff_disc_int = torch.zeros((B, 0, 0), dtype=torch.long, device=flow.device)
            eff_cont = flow.new_zeros((B, T, 0))
        else:
            eff_cont = packets_cont if T > 0 else packets_cont.new_zeros((B, 0, cfg.n_cont_pkt))
            eff_disc_int = packets_disc.long() if T > 0 else torch.zeros((B, 0, cfg.n_disc_pkt), dtype=torch.long, device=flow.device)

        z = self.build_tokens(flow, eff_cont, eff_disc_int)
        mask = self._loss_mask(lens)
        kpm = mask == 0
        dt = 1.0 / n_steps

        # Disc embed slot bounds (within token vector) for "freeze disc during ODE"
        cur_offset = 1 if cfg.use_flow_token else 0
        disc_start_in_token = 1 + self.eff_n_cont
        disc_end_in_token = disc_start_in_token + self.eff_n_disc
        if self.eff_n_disc > 0 and T > 0:
            disc_embed = z[:, cur_offset:cur_offset + T, disc_start_in_token:disc_end_in_token].clone()
        else:
            disc_embed = None

        for k in range(n_steps):
            t_val = 1.0 - k * dt
            t = torch.full((B,), t_val, device=z.device)
            (v, _) = self.velocity(z, t, key_padding_mask=kpm)
            if self.eff_n_disc > 0 and T > 0:
                v[:, cur_offset:cur_offset + T, disc_start_in_token:disc_end_in_token] = 0.0
            z = z - v * dt
            if disc_embed is not None:
                z[:, cur_offset:cur_offset + T, disc_start_in_token:disc_end_in_token] = disc_embed

        # Compute terminal-norm scores. Zero out the discrete embed slots so they don't pollute.
        z_real = z * mask[:, :, None]
        z_cont = z_real.clone()
        if self.eff_n_disc > 0 and T > 0:
            z_cont[:, cur_offset:cur_offset + T, disc_start_in_token:disc_end_in_token] = 0.0

        full_norm = z_cont.reshape(B, -1).norm(dim=-1) / (mask.sum(dim=-1) * self.token_dim).clamp_min(1.0).sqrt()
        out = {'terminal_norm': full_norm}
        if cfg.use_flow_token:
            out['terminal_flow'] = z_cont[:, 0].norm(dim=-1) / math.sqrt(self.token_dim)
        if T > 0:
            packet_count = mask[:, cur_offset:cur_offset + T].sum(dim=-1).clamp_min(1.0)
            out['terminal_packet'] = (z_cont[:, cur_offset:cur_offset + T] * mask[:, cur_offset:cur_offset + T, None]).reshape(B, -1).norm(dim=-1) / (packet_count * self.token_dim).sqrt()
        return out

    @torch.no_grad()
    def disc_nll_score(self, flow: torch.Tensor, packets_cont: torch.Tensor, packets_disc: torch.Tensor, lens: torch.Tensor, t_eval: float=0.5, cont_bin_edges: torch.Tensor | None=None) -> dict[str, torch.Tensor]:
        cfg = self.cfg
        B = flow.shape[0]
        T = self.eff_T
        device = flow.device
        if T == 0 or self.eff_n_disc == 0:
            return {}  # no disc head to score

        # Build effective disc int per mode
        if cfg.cont_as_disc:
            if cont_bin_edges is None:
                raise ValueError('cont_as_disc requires cont_bin_edges at scoring time')
            cont_int = self.quantize_cont(packets_cont, cont_bin_edges)
            eff_disc_int = torch.cat([cont_int, packets_disc.long()], dim=-1)
            eff_cont = flow.new_zeros((B, T, 0))
            ch_idx_list = list(cfg.cont_pkt_idx) + list(cfg.disc_pkt_idx)
        else:
            eff_disc_int = packets_disc.long()
            eff_cont = packets_cont
            ch_idx_list = list(cfg.disc_pkt_idx)

        mask = self._loss_mask(lens)
        kpm = mask == 0
        z = self.build_tokens(flow, eff_cont, eff_disc_int)
        t = torch.full((B,), float(t_eval), device=device)
        (_, d_logits) = self.velocity(z, t, key_padding_mask=kpm)
        cur_offset = 1 if cfg.use_flow_token else 0
        pkt_logits = d_logits[:, cur_offset:cur_offset + T]
        flat_logits = pkt_logits.reshape(-1, cfg.n_disc_classes)
        flat_targets = eff_disc_int.reshape(-1).long()
        ce = F.cross_entropy(flat_logits, flat_targets, reduction='none')
        ce = ce.view(B, T, self.eff_n_disc)
        pkt_real = mask[:, cur_offset:cur_offset + T].bool().float()
        per_sample = (ce.sum(dim=-1) * pkt_real).sum(dim=-1) / pkt_real.sum(dim=-1).clamp_min(1.0)
        per_ch = (ce * pkt_real[:, :, None]).sum(dim=1) / pkt_real.sum(dim=1).clamp_min(1.0)[:, None]
        out = {'disc_nll_total': per_sample}
        for c, idx in enumerate(ch_idx_list):
            out[f'disc_nll_ch{idx}'] = per_ch[:, c]
        return out

    def param_count(self) -> int:
        return sum((p.numel() for p in self.parameters()))