import os
import json
import pickle
import random
import numpy as np
import pandas as pd
from collections import defaultdict

import torch
import torchvision
from torch.utils.data import DataLoader, Dataset, Sampler

from video_reader import PyVideoReader

from diffusers.utils import export_to_video
from diffusers.training_utils import free_memory

# 5:  (21, 41,  61,  81, 101)
# 6:  (25, 49,  73,  97, 121)
# 7:  (29, 57,  85, 113, 141)
# 8:  (33, 65,  97, 129, 161)
# 9:  (37, 73, 109, 145, 181)
# 10: (41, 81, 121, 161, 201)
# 11: (45, 89, 133, 177, 221)
# 12: (49, 97, 145, 193, 241)

# 1:  (21 - 1) * 4 + 1 = 81,  162
# 2:  (22 - 1) * 4 + 1 = 85,  170
# 3:  (23 - 1) * 4 + 1 = 89,  178
# 4:  (24 - 1) * 4 + 1 = 93,  186
# 5:  (25 - 1) * 4 + 1 = 97,  194
# 6:  (26 - 1) * 4 + 1 = 101, 202
# 7:  (27 - 1) * 4 + 1 = 105, 210
# 8:  (28 - 1) * 4 + 1 = 109, 218
# 9:  (29 - 1) * 4 + 1 = 113, 226
# 10: (30 - 1) * 4 + 1 = 117, 234
# 11: (31 - 1) * 4 + 1 = 121, 242
# 12: (32 - 1) * 4 + 1 = 125, 250
# 13: (33 - 1) * 4 + 1 = 129, 258
# 14: (34 - 1) * 4 + 1 = 133, 266
# 15: (35 - 1) * 4 + 1 = 137, 274
# 16: (36 - 1) * 4 + 1 = 141, 282

resolution_bucket_options = {
    640: [
        (768, 320),
        (768, 384),
        (640, 384),
        (768, 512),
        (576, 448),
        (512, 512),
        (448, 576),
        (512, 768),
        (384, 640),
        (384, 768),
        (320, 768),
    ],
}

length_bucket_options = {
    1: [321, 301, 281, 261, 241, 221, 193, 181, 161, 141, 121, 101, 81, 61, 41, 21],
    2: [193, 177, 161, 156, 145, 133, 129, 121, 113, 109, 97, 85, 81, 73, 65, 61, 49, 37, 25],
}

def find_nearest_resolution_bucket(h, w, resolution=640):
    min_metric = float('inf')
    best_bucket = None
    for (bucket_h, bucket_w) in resolution_bucket_options[resolution]:
        metric = abs(h * bucket_w - w * bucket_h)
        if metric <= min_metric:
            min_metric = metric
            best_bucket = (bucket_h, bucket_w)
    return best_bucket

def find_nearest_length_bucket(length, stride=1):
    buckets = length_bucket_options[stride]
    min_bucket = min(buckets)
    if length < min_bucket:
        return length
    valid_buckets = [bucket for bucket in buckets if bucket <= length]
    return max(valid_buckets)

def read_cut_crop_and_resize(video_path, f_prime, h_prime, w_prime, stride=1, start_frame=None, end_frame=None):
    vr = PyVideoReader(video_path, threads=0) # 0 means auto (let ffmpeg pick the optimal number)
    total_frames = len(vr)

    # if stride != 1:
    #     required_span = stride * (f_prime - 1)
    #     start_frame = max(0, total_frames - required_span - 1)
    # else:
    #     start_frame = max(0, total_frames - f_prime)

    frame_indices = list(range(start_frame, end_frame, stride))
    assert len(frame_indices) == f_prime
    frames = torch.from_numpy(vr.get_batch(frame_indices)).float()

    # if stride != 1:
    #     required_span = stride * (f_prime - 1)
    #     start_frame = max(0, total_frames - required_span - 1)
    #     frame_indices = list(range(start_frame, total_frames, stride))
    #     assert len(frame_indices) == f_prime
    #     frames = torch.from_numpy(np.stack(vr.decode_fast(start_frame=0, end_frame=total_frames))).float()
    #     frames = frames[frame_indices]
    # else:
    #     start_frame = max(0, total_frames - f_prime)
    #     frames = torch.from_numpy(np.stack(vr.decode_fast(start_frame=start_frame, end_frame=total_frames))).float()


    # total_frames = len(vr)
    # start_frame = max(0, total_frames - f_prime)
    # # frame_indices = list(range(start_frame, total_frames))
    # # frames = torch.from_numpy(vr.get_batch(frame_indices)).float()
    # frames = torch.from_numpy(np.stack(vr.decode_fast(start_frame=start_frame, end_frame=total_frames))).float()


    frames = (frames / 127.5) - 1
    video = frames.permute(0, 3, 1, 2)

    frames, channels, h, w = video.shape
    aspect_ratio_original = h / w
    aspect_ratio_target = h_prime / w_prime

    if aspect_ratio_original >= aspect_ratio_target:
        new_h = int(w * aspect_ratio_target)
        top = (h - new_h) // 2
        bottom = top + new_h
        left = 0
        right = w
    else:
        new_w = int(h / aspect_ratio_target)
        left = (w - new_w) // 2
        right = left + new_w
        top = 0
        bottom = h

    # Crop the video
    cropped_video = video[:, :, top:bottom, left:right]
    # Resize the cropped video
    resized_video = torchvision.transforms.functional.resize(cropped_video, (h_prime, w_prime))
    return resized_video

def save_frames(frame_raw, fps=24, video_path="1.mp4"):        
    save_list = []
    for frame in frame_raw:
        frame = (frame + 1) / 2 * 255
        frame = torchvision.transforms.transforms.ToPILImage()(frame.to(torch.uint8)).convert("RGB")
        save_list.append(frame)
        frame = None
        del frame
    export_to_video(save_list, video_path, fps=fps)
    
    save_list = None
    del save_list
    free_memory()

class BucketedFeatureDataset(Dataset):
    def __init__(self, csv_file, video_folder, stride=1, cache_file=None, force_rebuild=False):
        self.csv_file = csv_file
        self.video_folder = video_folder
        self.stride = stride
        
        if cache_file is None:
            cache_file = os.path.join(video_folder, f"dataset_cache_stride{stride}.pkl")

        if force_rebuild or not os.path.exists(cache_file):
            print("Building metadata cache...")
            self._build_metadata()
            self._save_cache(cache_file)
        else:
            print("Loading cached metadata...")
            with open(cache_file, "rb") as f:
                cached_data = pickle.load(f)
            if cached_data.get("stride", 1) != stride:
                print(f"Stride mismatch in cache (cached: {cached_data.get('stride', 1)}, current: {stride}). Rebuilding...")
                self._build_metadata()
                self._save_cache(cache_file)
            else:
                self.samples = cached_data["samples"]
                self.buckets = cached_data["buckets"]
                print(f"Loaded {len(self.samples)} samples from cache")
        

    def _save_cache(self, cache_file):
        print("Saving metadata cache...")
        cached_data = {
            "samples": self.samples, 
            "buckets": self.buckets,
            "stride": self.stride
        }
        with open(cache_file, "wb") as f:
            pickle.dump(cached_data, f)
        print(f"Cached {len(self.samples)} samples with stride={self.stride}")

    # def _build_metadata(self):
    #     self.feature_files = [f for f in os.listdir(self.video_folder) if f.endswith(".mp4")]
    #     self.samples = []
    #     self.buckets = defaultdict(list)
    #     sample_idx = 0

    #     print(f"Processing {len(self.feature_files)} files...")
    #     for i, feature_file in enumerate(self.feature_files):
    #         if i % 10000 == 0:
    #             print(f"Processed {i}/{len(self.feature_files)} files")

    #         video_path = os.path.join(self.video_folder, feature_file)

    #         # Parse filename
    #         parts = feature_file.split("_")[:4]
    #         uttid = parts[0]
    #         num_frame = int(parts[1])
    #         height = int(parts[2])
    #         width = int(parts[3].replace(".mp4", ""))

    def _build_metadata(self):
        self.df = pd.read_csv(self.csv_file)
        
        self.samples = []
        self.buckets = defaultdict(list)
        sample_idx = 0
        
        print(f"Processing {len(self.df)} records from CSV with stride={self.stride}...")
        for i, row in self.df.iterrows():
            if i % 10000 == 0:
                print(f"Processed {i}/{len(self.df)} records")

            uttid = row['id']
            video_file = row['video path']
            video_path = os.path.join(self.video_folder, video_file)
            start_frame = row["start_frame"]
            end_frame = row["end_frame"]
            segment_id = row["segment_id"]
            num_frame = end_frame - start_frame
            # resolution = row["resolution"]
            # width, height = map(int, row["resolution"].split('x'))
            width = row["new_width"]
            height = row["new_height"]
            fps = row["new_fps"]

            uttid = f"{uttid}_{start_frame}_{end_frame}"
            prompt = row["prompt"]

            # prompt_path = os.path.join(self.video_folder, row["annotation path"], "caption.json")
            # with open(prompt_path, 'r') as f:
            #     data = json.load(f)
            # prompt = data['SceneDescription'] + " " + data["CameraMotion"]

            # # keep length >= 121
            # if num_frame < 121:
            #     continue

            effective_num_frame = (num_frame + self.stride - 1) // self.stride
            bucket_height, bucket_width = find_nearest_resolution_bucket(height, width, resolution=640)
            bucket_num_frame = find_nearest_length_bucket(effective_num_frame, stride=self.stride)
            bucket_key = (bucket_num_frame, bucket_height, bucket_width)

            sample_info = {
                "uttid": uttid,
                "bucket_key": bucket_key,
                "video_path": video_path,
                "prompt": prompt,
                "fps": fps,
                "stride": self.stride,
                "effective_num_frame": effective_num_frame,
                "num_frame": num_frame,
                "height": height,
                "width": width,
                "bucket_num_frame": bucket_num_frame,
                "bucket_height": bucket_height,
                "bucket_width": bucket_width,
                "start_frame": start_frame,
                "end_frame": end_frame,
            }

            self.samples.append(sample_info)
            self.buckets[bucket_key].append(sample_idx)
            sample_idx += 1

    def __len__(self):
        return len(self.samples)

    def __getitem__(self, idx):
        # sample_info = self.samples[idx]
        # video_data = read_cut_crop_and_resize(
        #     video_path=sample_info["video_path"],
        #     f_prime=sample_info["bucket_num_frame"],
        #     h_prime=sample_info["bucket_height"],
        #     w_prime=sample_info["bucket_width"],
        #     stride=self.stride,
        # )
        while True:
            sample_info = self.samples[idx]
            try:
                video_data = read_cut_crop_and_resize(
                    video_path=sample_info["video_path"],
                    f_prime=sample_info["bucket_num_frame"],
                    h_prime=sample_info["bucket_height"],
                    w_prime=sample_info["bucket_width"],
                    stride=self.stride,
                    start_frame=sample_info["start_frame"],
                    end_frame=sample_info["end_frame"],
                )
                break
            except Exception:
                idx = random.randint(0, len(self.samples) - 1)
                print(f"Error loading {sample_info['video_path']}, retrying...")

        return {
            "uttid": sample_info["uttid"],
            "bucket_key": sample_info["bucket_key"],
            "video_metadata": {
                "num_frames": sample_info["bucket_num_frame"],
                "height": sample_info["bucket_height"],
                "width": sample_info["bucket_width"],
                "fps": sample_info["fps"],
                "stride": self.stride,
                "effective_num_frame": sample_info["effective_num_frame"],
            },
            "videos": video_data,
            "prompts": sample_info["prompt"],
            "first_frames_images": (video_data[0] + 1) / 2 * 255,
        }

class BucketedSampler(Sampler):
    def __init__(self, dataset, batch_size, drop_last=False, shuffle=False, seed=42):
        self.dataset = dataset
        self.batch_size = batch_size
        self.drop_last = drop_last
        self.shuffle = shuffle
        self.seed = seed
        self.generator = torch.Generator()
        self.buckets = dataset.buckets
        self._epoch = 0

    def set_epoch(self, epoch):
        self._epoch = epoch

    def __iter__(self):
        if self.shuffle:
            self.generator.manual_seed(self.seed + self._epoch)
        else:
            self.generator.manual_seed(self.seed)

        bucket_iterators = {}
        bucket_batches = {}

        for bucket_key, sample_indices in self.buckets.items():
            indices = sample_indices.copy()
            if self.shuffle:
                indices = torch.randperm(len(indices), generator=self.generator).tolist()
                indices = [sample_indices[i] for i in indices]

            batches = []
            for i in range(0, len(indices), self.batch_size):
                batch = indices[i : i + self.batch_size]
                if len(batch) == self.batch_size or not self.drop_last:
                    batches.append(batch)

            if batches:
                bucket_batches[bucket_key] = batches
                bucket_iterators[bucket_key] = iter(batches)

        remaining_buckets = list(bucket_iterators.keys())

        while remaining_buckets:
            idx = torch.randint(len(remaining_buckets), (1,), generator=self.generator).item()
            bucket_key = remaining_buckets[idx]

            bucket_iter = bucket_iterators[bucket_key]

            try:
                batch = next(bucket_iter)
                for sample_idx in batch:
                    sample_bucket = self.dataset.samples[sample_idx]['bucket_key']
                    if sample_bucket != bucket_key:
                        print(f"❌ BUCKET MISMATCH! Expected {bucket_key}, got {sample_bucket} for sample {sample_idx}")
                yield batch
            except StopIteration:
                remaining_buckets.remove(bucket_key)

    def __len__(self):
        total_batches = 0
        for sample_indices in self.buckets.values():
            num_batches = len(sample_indices) // self.batch_size
            if not self.drop_last and len(sample_indices) % self.batch_size != 0:
                num_batches += 1
            total_batches += num_batches
        return total_batches


def collate_fn(batch):
    def collate_dict(data_list):
        if isinstance(data_list[0], dict):
            return {
                key: collate_dict([d[key] for d in data_list])
                for key in data_list[0]
            }
        elif isinstance(data_list[0], torch.Tensor):
            return torch.stack(data_list)
        else:
            return data_list
    
    return {
        key: collate_dict([d[key] for d in batch])
        for key in batch[0]
    }


if __name__ == "__main__":
    from accelerate import Accelerator

    csv_file = f"/mnt/bn/yufan-dev-my/ysh/Ckpts/SpatialVID/SpatialVID-HQ-Final/test_prompt_filtered"
    video_folder = f"/mnt/bn/yufan-dev-my/ysh/Ckpts/SpatialVID/SpatialVID-HQ-Final"
    stride = 1
    batch_size = 64
    num_train_epochs = 1
    seed = 0
    output_dir = "accelerate_checkpoints"
    checkpoint_dirs = (
        [
            d
            for d in os.listdir(output_dir)
            if d.startswith("checkpoint-") and os.path.isdir(os.path.join(output_dir, d))
        ]
        if os.path.exists(output_dir)
        else []
    )

    dataset = BucketedFeatureDataset(csv_file=csv_file, video_folder=video_folder, stride=stride)
    sampler = BucketedSampler(dataset, batch_size=batch_size, drop_last=True, shuffle=False, seed=seed)
    dataloader = DataLoader(dataset, batch_sampler=sampler, collate_fn=collate_fn, num_workers=8)

    print(len(dataset), len(dataloader))
    accelerator = Accelerator()
    dataloader = accelerator.prepare(dataloader)
    print(f"Dataset size: {len(dataset)}, Dataloader batches: {len(dataloader)}")
    print(f"Process index: {accelerator.process_index}, World size: {accelerator.num_processes}")

    step = 0
    global_step = 0
    first_epoch = 0
    num_update_steps_per_epoch = len(dataloader)

    print("Testing dataloader...")
    step = global_step
    for epoch in range(first_epoch, num_train_epochs):
        sampler.set_epoch(epoch)
        skip_steps = 0
        printed_skip_log = False
        for i, batch in enumerate(dataloader):
            if epoch == first_epoch and skip_steps < (global_step % num_update_steps_per_epoch):
                skip_steps += 1
                continue
            if epoch == first_epoch and not printed_skip_log:
                print(f"Skip {skip_steps} steps in epoch {epoch}")
                printed_skip_log = True

            # Get metadata
            uttid = batch["uttid"]
            bucket_key = batch["bucket_key"]
            num_frame = batch["video_metadata"]["num_frames"]
            height = batch["video_metadata"]["height"]
            width = batch["video_metadata"]["width"]

            # Get feature
            video_data = batch["videos"]
            prompt = batch["prompts"]
            first_frames_images = batch["first_frames_images"]
            first_frames_images = [torchvision.transforms.ToPILImage()(x.to(torch.uint8)) for x in first_frames_images]

            # import pdb;pdb.set_trace()
            # save_frames(video_data[0].squeeze(0), video_path="1.mp4")

            if accelerator.process_index == 0:
                # print info
                print(f" Step {step}:")
                print(f"  Batch {i}:")
                print(f"  Batch size: {len(uttid)}")
                print(f"  Uttids: {uttid}")
                print(f"  Dimensions - frames: {num_frame[0]}, height: {height[0]}, width: {width[0]}")
                print(f"  Bucket key: {bucket_key[0]}")
                print(f"  Videos shape: {video_data.shape}")
                print(f"  Cpation: {prompt}")

                # verify
                assert all(nf == num_frame[0] for nf in num_frame), "Frame numbers not consistent in batch"
                assert all(h == height[0] for h in height), "Heights not consistent in batch"
                assert all(w == width[0] for w in width), "Widths not consistent in batch"

                print("  ✓ Batch dimensions are consistent")

            step += 1