"""Schema and validation for exact BF16 Predictor-v2 trajectories."""

from __future__ import annotations

from typing import Mapping

import torch

from .schema import (
    CHUNK_LATENT_FRAMES,
    HIDDEN_SIZE,
    LATENT_CHANNELS,
    LATENT_HEIGHT,
    LATENT_WIDTH,
    NUM_STEPS,
    STEP_FIELDS,
    TOKENS_PER_CHUNK,
)


LEGACY_SCHEMA_VERSION_V2 = "predictor_v2_exact_ar_context_kv_bf16"
SCHEMA_VERSION_V2 = "predictor_v2_padded_masked_ar_context_kv_bf16"
CONTEXT_BLOCK_IDS = (0, 1, 52, 53)
ATTENTION_HEADS = 16
HEAD_DIM = HIDDEN_SIZE // ATTENTION_HEADS
TOKENS_PER_FRAME = LATENT_HEIGHT * LATENT_WIDTH
DEFAULT_TEXT_KV_TOKENS = 903
DEFAULT_CONTEXT_KV_FRAMES = 20


def block_key(block_id: int, field: str) -> str:
    if block_id not in CONTEXT_BLOCK_IDS:
        raise ValueError(f"Unsupported context block: {block_id}")
    return f"block_{block_id:02d}_{field}"


def expected_step_keys() -> set[str]:
    keys = {
        "action_labels",
        "target_viewmats",
        "target_Ks",
        "rope_temporal_size",
        "start_rope_start_idx",
    }
    for step in range(NUM_STEPS):
        keys.update(f"step_{step}_{field}" for field in STEP_FIELDS)
    return keys


def _validate_bf16(name: str, tensor: torch.Tensor) -> None:
    if tensor.is_floating_point() and tensor.dtype != torch.bfloat16:
        raise ValueError(f"{name} must be BF16, got {tensor.dtype}")
    if tensor.is_floating_point() and not torch.isfinite(tensor).all():
        raise ValueError(f"Non-finite values in {name}")


def _validate_mask(name: str, mask: torch.Tensor, expected_shape: tuple[int, int]) -> None:
    if tuple(mask.shape) != expected_shape:
        raise ValueError(f"Unexpected {name} shape: {tuple(mask.shape)} != {expected_shape}")
    if mask.dtype != torch.bool:
        raise ValueError(f"{name} must be bool, got {mask.dtype}")
    if mask.shape[1] and not torch.equal(
        mask, torch.arange(mask.shape[1], device=mask.device)[None] < mask.sum(dim=1)[:, None]
    ):
        raise ValueError(f"{name} must contain a contiguous valid prefix")


def validate_case_tensors_v2(tensors: Mapping[str, torch.Tensor]) -> int:
    required = {"image_condition_latent", "text_valid_mask"}
    for block_id in CONTEXT_BLOCK_IDS:
        required.update(
            {block_key(block_id, "k_txt"), block_key(block_id, "v_txt")}
        )
    missing = required.difference(tensors)
    if missing:
        raise ValueError(f"Missing v2 case tensor keys: {sorted(missing)}")

    image_condition = tensors["image_condition_latent"]
    if tuple(image_condition.shape) != (1, LATENT_CHANNELS, 1, LATENT_HEIGHT, LATENT_WIDTH):
        raise ValueError(f"Unexpected image condition shape: {tuple(image_condition.shape)}")
    _validate_bf16("image_condition_latent", image_condition)

    text_valid_mask = tensors["text_valid_mask"]
    token_count = None
    for block_id in CONTEXT_BLOCK_IDS:
        k_txt = tensors[block_key(block_id, "k_txt")]
        v_txt = tensors[block_key(block_id, "v_txt")]
        if k_txt.shape != v_txt.shape:
            raise ValueError(f"Block {block_id} text K/V shape mismatch")
        if (
            k_txt.ndim != 4
            or k_txt.shape[0] != 1
            or k_txt.shape[1] != ATTENTION_HEADS
            or k_txt.shape[3] != HEAD_DIM
        ):
            raise ValueError(f"Unexpected block {block_id} text KV shape: {tuple(k_txt.shape)}")
        if token_count is None:
            token_count = int(k_txt.shape[2])
        elif int(k_txt.shape[2]) != token_count:
            raise ValueError("Text token count differs between context blocks")
        _validate_bf16(block_key(block_id, "k_txt"), k_txt)
        _validate_bf16(block_key(block_id, "v_txt"), v_txt)
    assert token_count is not None
    _validate_mask("text_valid_mask", text_valid_mask, (1, token_count))
    valid_tokens = int(text_valid_mask.sum())
    if valid_tokens <= 0:
        raise ValueError("text_valid_mask must contain at least one valid token")
    return valid_tokens


def validate_step_tensors_v2(tensors: Mapping[str, torch.Tensor]) -> None:
    missing = expected_step_keys().difference(tensors)
    if missing:
        raise ValueError(f"Missing v2 step tensor keys: {sorted(missing)}")

    if tuple(tensors["action_labels"].shape) != (1, CHUNK_LATENT_FRAMES):
        raise ValueError(f"Unexpected action_labels shape: {tuple(tensors['action_labels'].shape)}")
    if tuple(tensors["target_viewmats"].shape) != (1, CHUNK_LATENT_FRAMES, 4, 4):
        raise ValueError(f"Unexpected target_viewmats shape: {tuple(tensors['target_viewmats'].shape)}")
    if tuple(tensors["target_Ks"].shape) != (1, CHUNK_LATENT_FRAMES, 3, 3):
        raise ValueError(f"Unexpected target_Ks shape: {tuple(tensors['target_Ks'].shape)}")

    for step in range(NUM_STEPS):
        noisy = tensors[f"step_{step}_noisy_sample"]
        hidden = tensors[f"step_{step}_final_hidden"]
        condition = tensors[f"step_{step}_frame_condition"]
        velocity = tensors[f"step_{step}_velocity"]
        timestep = tensors[f"step_{step}_timestep"]
        if tuple(noisy.shape) != (1, LATENT_CHANNELS, CHUNK_LATENT_FRAMES, LATENT_HEIGHT, LATENT_WIDTH):
            raise ValueError(f"Step {step} noisy shape: {tuple(noisy.shape)}")
        if tuple(hidden.shape) != (1, TOKENS_PER_CHUNK, HIDDEN_SIZE):
            raise ValueError(f"Step {step} hidden shape: {tuple(hidden.shape)}")
        if tuple(condition.shape) != (1, CHUNK_LATENT_FRAMES, HIDDEN_SIZE):
            raise ValueError(f"Step {step} condition shape: {tuple(condition.shape)}")
        if tuple(velocity.shape) != tuple(noisy.shape):
            raise ValueError(f"Step {step} velocity shape: {tuple(velocity.shape)}")
        if timestep.numel() != 1 or timestep.dtype != torch.float32:
            raise ValueError(f"Step {step} timestep must be one FP32 scalar")
        for name, tensor in (
            ("noisy_sample", noisy),
            ("final_hidden", hidden),
            ("frame_condition", condition),
            ("velocity", velocity),
        ):
            _validate_bf16(f"step_{step}_{name}", tensor)

    _validate_bf16("target_viewmats", tensors["target_viewmats"])
    _validate_bf16("target_Ks", tensors["target_Ks"])


def validate_vision_context_v2(
    block_id: int,
    tensors: Mapping[str, torch.Tensor],
) -> int:
    required = {"k_vision", "v_vision", "context_valid_mask"}
    missing = required.difference(tensors)
    if missing:
        raise ValueError(f"Block {block_id} missing vision KV keys: {sorted(missing)}")
    k_vision = tensors["k_vision"]
    v_vision = tensors["v_vision"]
    if k_vision.shape != v_vision.shape:
        raise ValueError(f"Block {block_id} vision K/V shape mismatch")
    if (
        k_vision.ndim != 4
        or k_vision.shape[0] != 2
        or k_vision.shape[1] != ATTENTION_HEADS
        or k_vision.shape[3] != HEAD_DIM
    ):
        raise ValueError(f"Unexpected block {block_id} vision KV shape: {tuple(k_vision.shape)}")
    if k_vision.shape[2] % TOKENS_PER_FRAME:
        raise ValueError(
            f"Block {block_id} context tokens {k_vision.shape[2]} are not frame-aligned"
        )
    _validate_bf16(f"block_{block_id}_k_vision", k_vision)
    _validate_bf16(f"block_{block_id}_v_vision", v_vision)
    context_valid_mask = tensors["context_valid_mask"]
    _validate_mask(
        f"block_{block_id}_context_valid_mask",
        context_valid_mask,
        (1, int(k_vision.shape[2])),
    )
    valid_tokens = int(context_valid_mask.sum())
    if valid_tokens % TOKENS_PER_FRAME:
        raise ValueError(
            f"Block {block_id} valid context tokens {valid_tokens} are not frame-aligned"
        )
    return valid_tokens // TOKENS_PER_FRAME