"""
build_sequences.py
==================
从族谱（genealogy.pkl）和多尺度 3DGS 量化索引构建 split 序列。

序列结构（固定长度 MAX_SEQ_LEN = 38）：
  [parent(1)] [uncle×≤4] [child×≤32] [EOS(1)] [PAD×...]

每个 token 字段：
  dx, dy, dz    float32  坐标偏移（parent=0,0,0；其他=相对parent）
  scale_idx     int32    scale codebook 索引
  rot_idx       int32    rotation codebook 索引
  dc_idx        int32    DC codebook 索引
  sh_idx        int32    SH codebook 索引
  opacity       float32  不透明度原值（不量化）
  role          uint8    身份标识：
                           0 = parent（父节点，坐标原点）
                           1 = uncle （叔伯节点，相对坐标）
                           2 = child （子节点，相对坐标）
                           3 = EOS   （序列结束符）
                           4 = PAD   （补齐，不参与计算）

层级方向（粗→细）：
  quant_paths 按 L3, L2, L1, L0 顺序传入
  L3 最粗（点最少）作为 parent，逐级向细展开
"""

import os
import argparse
import pickle
import numpy as np

# ─────────────────────────────────────────────
# 常量
# ─────────────────────────────────────────────

ROLE_PARENT  = np.uint8(0)
ROLE_UNCLE   = np.uint8(1)
ROLE_CHILD   = np.uint8(2)
ROLE_EOS     = np.uint8(3)
ROLE_PAD     = np.uint8(4)

MAX_CHILDREN = 32
MAX_UNCLES   = 4
# 固定序列长度：parent(1) + uncle(4) + child(32) + EOS(1)
MAX_SEQ_LEN  = 1 + MAX_UNCLES + MAX_CHILDREN + 1   # = 38

TOKEN_DTYPE = np.dtype([
    ('dx',         np.float32),
    ('dy',         np.float32),
    ('dz',         np.float32),
    ('scale_idx',  np.int32),
    ('rot_idx',    np.int32),
    ('dc_idx',     np.int32),
    ('sh_idx',     np.int32),
    ('opacity',    np.float32),
    ('role',       np.uint8),
])


# ─────────────────────────────────────────────
# 1. 加载量化索引
# ─────────────────────────────────────────────

def load_quantized(npz_path: str) -> dict:
    npz = np.load(npz_path)
    return {
        'scale_indices':    npz['scale_indices'],
        'rotation_indices': npz['rotation_indices'],
        'dc_indices':       npz['dc_indices'],
        'sh_indices':       npz['sh_indices'],
        'positions':        npz['positions'],
        'opacities':        npz['opacities'].squeeze(),
    }


# ─────────────────────────────────────────────
# 2. 加载族谱
# ─────────────────────────────────────────────

def load_genealogy(genealogy_path: str) -> dict:
    with open(genealogy_path, 'rb') as f:
        return pickle.load(f)


# ─────────────────────────────────────────────
# 3. Token 构造工具
# ─────────────────────────────────────────────

def make_token(gauss_idx: int, quant: dict,
               parent_pos: np.ndarray, role: np.uint8) -> np.ndarray:
    """构造单个特征 token，坐标为相对 parent_pos 的偏移。"""
    pos   = quant['positions'][gauss_idx]
    delta = pos - parent_pos

    token = np.zeros(1, dtype=TOKEN_DTYPE)
    token['dx']        = delta[0]
    token['dy']        = delta[1]
    token['dz']        = delta[2]
    token['scale_idx'] = quant['scale_indices'][gauss_idx]
    token['rot_idx']   = quant['rotation_indices'][gauss_idx]
    token['dc_idx']    = quant['dc_indices'][gauss_idx]
    token['sh_idx']    = quant['sh_indices'][gauss_idx]
    token['opacity']   = quant['opacities'][gauss_idx]
    token['role']      = role
    return token[0]


def make_eos_token() -> np.ndarray:
    """结束符：特征全 0，role=3。"""
    token = np.zeros(1, dtype=TOKEN_DTYPE)
    token['role'] = ROLE_EOS
    return token[0]


def make_pad_token() -> np.ndarray:
    """补齐符：特征全 0，role=4，不参与任何 loss/attention。"""
    token = np.zeros(1, dtype=TOKEN_DTYPE)
    token['role'] = ROLE_PAD
    return token[0]


# ─────────────────────────────────────────────
# 4. 构建单层所有 split 序列
# ─────────────────────────────────────────────

def build_level_sequences(
    parent_quant: dict,
    child_quant:  dict,
    children_ids: np.ndarray,    # (N_coarse, MAX_CHILDREN)，-1 为空位
    max_uncles:   int = MAX_UNCLES,
    min_children: int = 1,
    fixed_len:    int = MAX_SEQ_LEN,
) -> list:
    """
    遍历每个粗节点，构造一条固定长度的 split 序列。

    序列 token 顺序：
      [parent(1)] [uncle×≤max_uncles] [child×N_valid] [EOS(1)] [PAD×...]

    role 编码：
      0 = parent   坐标固定为 (0,0,0)，特征来自自身
      1 = uncle    坐标相对 parent，特征来自自身
      2 = child    坐标相对 parent，特征来自细尺度
      3 = EOS      结束符，标志真实子节点已全部输出
      4 = PAD      补齐，attention mask 中被屏蔽

    返回：list of np.ndarray，每个元素 shape (fixed_len,) TOKEN_DTYPE
    """
    N_parents = children_ids.shape[0]
    sequences = []

    for p_idx in range(N_parents):
        child_row      = children_ids[p_idx]
        valid_children = child_row[child_row >= 0]

        if len(valid_children) < min_children:
            continue

        parent_pos = parent_quant['positions'][p_idx]
        tokens     = []

        # ── parent（坐标置零）─────────────────────────
        t = make_token(p_idx, parent_quant, parent_pos, ROLE_PARENT)
        t['dx'] = t['dy'] = t['dz'] = 0.0
        tokens.append(t)

        # ── uncle（前后各 half 个空间邻居）────────────
        half         = max_uncles // 2
        added_uncles = 0
        for offset in list(range(-half, 0)) + list(range(1, half + 1)):
            u_idx = p_idx + offset
            if 0 <= u_idx < N_parents and added_uncles < max_uncles:
                tokens.append(
                    make_token(u_idx, parent_quant, parent_pos, ROLE_UNCLE)
                )
                added_uncles += 1

        # ── child（所有有效子节点）──────────────────────
        for c_idx in valid_children:
            tokens.append(
                make_token(int(c_idx), child_quant, parent_pos, ROLE_CHILD)
            )

        # ── EOS ────────────────────────────────────────
        tokens.append(make_eos_token())

        # ── PAD 补齐到 fixed_len ────────────────────────
        while len(tokens) < fixed_len:
            tokens.append(make_pad_token())

        # 超长截断（极端情况：uncle+child 超出 fixed_len-2）
        if len(tokens) > fixed_len:
            tokens = tokens[:fixed_len - 1]
            tokens.append(make_eos_token())

        sequences.append(np.array(tokens, dtype=TOKEN_DTYPE))

    return sequences


# ─────────────────────────────────────────────
# 5. 多层序列构建主函数
# ─────────────────────────────────────────────

def build_all_sequences(
    quant_paths:    list,    # 按粗→细顺序：[L3.npz, L2.npz, L1.npz, L0.npz]
    genealogy_path: str,
    save_dir:       str,
    max_uncles:     int = MAX_UNCLES,
    min_children:   int = 1,
) -> None:
    """
    quant_paths 按粗→细顺序传入，例如：
        [L3_quantized.npz, L2_quantized.npz, L1_quantized.npz, L0_quantized.npz]

    genealogy.pkl 格式：
        genealogy[3]['children_ids'] shape (N_L3, MAX_CHILDREN)
            L3粗节点 → L2细节点索引
        genealogy[2]['children_ids'] shape (N_L2, MAX_CHILDREN)
            L2粗节点 → L1细节点索引
        genealogy[1]['children_ids'] shape (N_L1, MAX_CHILDREN)
            L1粗节点 → L0细节点索引

    输出（按粗→细命名）：
        save_dir/sequences_L3_to_L2.pkl
        save_dir/sequences_L2_to_L1.pkl
        save_dir/sequences_L1_to_L0.pkl
    """
    os.makedirs(save_dir, exist_ok=True)

    print(f"[build] 加载族谱：{genealogy_path}")
    genealogy = load_genealogy(genealogy_path)

    print(f"[build] 加载量化数据（共 {len(quant_paths)} 个尺度，粗→细顺序）...")
    quants = []
    for path in quant_paths:
        print(f"         {os.path.basename(path)}")
        quants.append(load_quantized(path))

    # quants[0]=最粗(L3), quants[1]=L2, ..., quants[-1]=最细(L0)
    n_levels = len(quants)
    # genealogy key: quants[0]→quants[1] 对应 key=n_levels-1（即3）
    #               quants[1]→quants[2] 对应 key=n_levels-2（即2）
    #               ...

    for i in range(n_levels - 1):
        coarse_level = n_levels - 1 - i      # 3, 2, 1
        fine_level   = coarse_level - 1      # 2, 1, 0
        gen_key      = coarse_level          # genealogy key 与粗尺度编号一致

        coarse_name = f"L{coarse_level}"
        fine_name   = f"L{fine_level}"

        if gen_key not in genealogy:
            print(f"[build] 警告：族谱中无 key={gen_key}，跳过 {coarse_name}→{fine_name}")
            continue

        parent_quant = quants[i]
        child_quant  = quants[i + 1]
        children_ids = genealogy[gen_key]['children_ids']   # (N_coarse, 32)

        print(f"\n[build] 构建 {coarse_name}→{fine_name} 序列")
        print(f"         父节点数={children_ids.shape[0]}, "
              f"children_ids.shape={children_ids.shape}")

        sequences = build_level_sequences(
            parent_quant, child_quant, children_ids,
            max_uncles=max_uncles,
            min_children=min_children,
            fixed_len=MAX_SEQ_LEN,
        )

        if len(sequences) == 0:
            print("         [警告] 没有有效序列，请检查族谱与量化数据")
            continue

        # 统计子节点数分布
        child_counts = np.array([
            int((s['role'] == ROLE_CHILD).sum()) for s in sequences
        ])
        print(f"         生成序列数：{len(sequences)}")
        print(f"         子节点数：min={child_counts.min()}, "
              f"max={child_counts.max()}, mean={child_counts.mean():.2f}")

        # role 分布统计
        all_roles = np.concatenate([s['role'] for s in sequences])
        for r, name in [(0,'parent'),(1,'uncle'),(2,'child'),(3,'EOS'),(4,'PAD')]:
            cnt = (all_roles == r).sum()
            print(f"           role={r}({name:6s})：{cnt:,} tokens")

        out_path = os.path.join(save_dir,
                                f"sequences_{coarse_name}_to_{fine_name}.pkl")
        with open(out_path, 'wb') as f:
            pickle.dump(sequences, f, protocol=4)

        size_mb = os.path.getsize(out_path) / 1024 / 1024
        print(f"         保存 → {out_path}  ({size_mb:.2f} MB)")

    print(f"\n[build] 全部序列构建完成！")
    print(f"        固定序列长度 MAX_SEQ_LEN={MAX_SEQ_LEN} "
          f"(parent=1, uncle≤{MAX_UNCLES}, child≤{MAX_CHILDREN}, EOS=1)")


# ─────────────────────────────────────────────
# 6. CLI
# ─────────────────────────────────────────────

def parse_args():
    parser = argparse.ArgumentParser(description="构建 3DGS split 序列")
    parser.add_argument('--quant_paths', nargs='+', required=True,
                        help='量化 .npz 路径，按粗→细顺序：L3 L2 L1 L0')
    parser.add_argument('--genealogy',    required=True,
                        help='族谱 genealogy.pkl 路径')
    parser.add_argument('--save_dir',     default='./sequences',
                        help='序列输出目录（默认 ./sequences）')
    parser.add_argument('--max_uncles',   type=int, default=MAX_UNCLES)
    parser.add_argument('--min_children', type=int, default=1)
    return parser.parse_args()


if __name__ == '__main__':
    args = parse_args()
    build_all_sequences(
        quant_paths=args.quant_paths,
        genealogy_path=args.genealogy,
        save_dir=args.save_dir,
        max_uncles=args.max_uncles,
        min_children=args.min_children,
    )