"""Tensor and manifest schema for Self-Forcing Predictor v4 data."""

from __future__ import annotations

from collections.abc import Mapping

import torch


SCHEMA_VERSION = "self_forcing_predictor_v4_bf16_v1"
CANDIDATE_BLOCK_IDS = (0, 1, 28, 29)
NUM_STEPS = 4
NUM_CHUNKS = 7
CHUNK_FRAMES = 3
LATENT_CHANNELS = 16
LATENT_HEIGHT = 60
LATENT_WIDTH = 104
HIDDEN_SIZE = 1536
NUM_HEADS = 12
HEAD_DIM = 128
TEXT_TOKENS = 512
TOKENS_PER_FRAME = 1560
TOKENS_PER_CHUNK = CHUNK_FRAMES * TOKENS_PER_FRAME
SUPERVISION_PAIRS = ((0, 1), (1, 2), (2, 3))


def _require_finite_bf16(name: str, tensor: torch.Tensor) -> None:
    if tensor.dtype != torch.bfloat16:
        raise ValueError(f"{name} must be BF16, got {tensor.dtype}")
    if not torch.isfinite(tensor).all():
        raise ValueError(f"{name} contains non-finite values")


def validate_step_tensors(tensors: Mapping[str, torch.Tensor]) -> None:
    """Validate one chunk containing all four Full-DiT teacher steps."""
    required = {
        f"step_{step}_{field}"
        for step in range(NUM_STEPS)
        for field in ("noisy_latent", "timestep", "final_hidden", "flow")
    }
    missing = required.difference(tensors)
    extra = set(tensors).difference(required)
    if missing or extra:
        raise ValueError(
            f"step tensor keys mismatch; missing={sorted(missing)}, extra={sorted(extra)}"
        )

    latent_shape = (
        1,
        CHUNK_FRAMES,
        LATENT_CHANNELS,
        LATENT_HEIGHT,
        LATENT_WIDTH,
    )
    hidden_shape = (1, TOKENS_PER_CHUNK, HIDDEN_SIZE)
    timestep_shape = (1, CHUNK_FRAMES)
    for step in range(NUM_STEPS):
        for field in ("noisy_latent", "flow"):
            name = f"step_{step}_{field}"
            value = tensors[name]
            if tuple(value.shape) != latent_shape:
                raise ValueError(f"{name} has shape {tuple(value.shape)}, expected {latent_shape}")
            _require_finite_bf16(name, value)
        hidden_name = f"step_{step}_final_hidden"
        hidden = tensors[hidden_name]
        if tuple(hidden.shape) != hidden_shape:
            raise ValueError(
                f"{hidden_name} has shape {tuple(hidden.shape)}, expected {hidden_shape}"
            )
        _require_finite_bf16(hidden_name, hidden)
        timestep_name = f"step_{step}_timestep"
        timestep = tensors[timestep_name]
        if tuple(timestep.shape) != timestep_shape or timestep.dtype != torch.int64:
            raise ValueError(
                f"{timestep_name} must be INT64 {timestep_shape}, "
                f"got {timestep.dtype} {tuple(timestep.shape)}"
            )
        if not bool(torch.all(timestep == timestep[:, :1])):
            raise ValueError(f"{timestep_name} must be constant within the temporal chunk")


def validate_clean_prefeature(
    block_id: int,
    tensors: Mapping[str, torch.Tensor],
) -> None:
    """Validate the input to ``block.self_attn.k`` from one clean pass."""
    if int(block_id) not in CANDIDATE_BLOCK_IDS:
        raise ValueError(f"unsupported clean prefeature block: {block_id}")
    required = {"self_attn_input", "start_frame", "num_frames"}
    missing = required.difference(tensors)
    extra = set(tensors).difference(required)
    if missing or extra:
        raise ValueError(
            f"clean prefeature keys mismatch; missing={sorted(missing)}, extra={sorted(extra)}"
        )
    feature = tensors["self_attn_input"]
    expected = (1, TOKENS_PER_CHUNK, HIDDEN_SIZE)
    if tuple(feature.shape) != expected:
        raise ValueError(
            f"block {block_id} self_attn_input has shape {tuple(feature.shape)}, "
            f"expected {expected}"
        )
    _require_finite_bf16("self_attn_input", feature)
    for name in ("start_frame", "num_frames"):
        value = tensors[name]
        if value.dtype != torch.int64 or tuple(value.shape) != (1,):
            raise ValueError(f"{name} must be one INT64 value")
    if int(tensors["start_frame"].item()) < 0:
        raise ValueError("start_frame must be non-negative")
    if int(tensors["num_frames"].item()) != CHUNK_FRAMES:
        raise ValueError(f"num_frames must equal {CHUNK_FRAMES}")


def validate_case_tensors(
    tensors: Mapping[str, torch.Tensor],
    block_ids: tuple[int, ...] = CANDIDATE_BLOCK_IDS,
) -> None:
    """Validate the case-level selected-layer text cross-attention KV."""
    required = {
        f"block_{block_id:02d}_cross_{field}"
        for block_id in block_ids
        for field in ("k", "v")
    }
    missing = required.difference(tensors)
    extra = set(tensors).difference(required)
    if missing or extra:
        raise ValueError(
            f"case tensor keys mismatch; missing={sorted(missing)}, extra={sorted(extra)}"
        )
    expected = (1, TEXT_TOKENS, NUM_HEADS, HEAD_DIM)
    token_counts = set()
    for name in sorted(required):
        value = tensors[name]
        if value.ndim != 4 or (
            value.shape[0] != expected[0]
            or value.shape[2] != expected[2]
            or value.shape[3] != expected[3]
        ):
            raise ValueError(
                f"{name} has shape {tuple(value.shape)}, expected [1, text, 12, 128]"
            )
        token_counts.add(int(value.shape[1]))
        _require_finite_bf16(name, value)
    if len(token_counts) != 1 or next(iter(token_counts)) != TEXT_TOKENS:
        raise ValueError(f"all text KV tensors must have exactly {TEXT_TOKENS} tokens")