import os
import tarfile
from pathlib import Path
from typing import Optional

import faiss
import numpy as np
import pyarrow as pa
import requests
import torch
from tqdm import tqdm
from transformers import CLIPModel, CLIPProcessor
from transformers.modeling_utils import PreTrainedModel

from .configuration_cased import CaSEDConfig
from .transforms_cased import default_vocabulary_transforms

DATABASES = {
    "cc12m": {
        "url": "https://storage-cased.alessandroconti.me/cc12m.tar.gz",
        "cache_subdir": "./cc12m/vit-l-14/",
    },
}


class MetadataProvider:
    """Metadata provider.

    It uses arrow files to store metadata and retrieve it efficiently.

    Code reference:
        - https://github.dev/rom1504/clip-retrieval
    """

    def __init__(self, arrow_folder: Path):
        arrow_files = [str(a) for a in sorted(arrow_folder.glob("**/*")) if a.is_file()]
        self.table = pa.concat_tables(
            [
                pa.ipc.RecordBatchFileReader(pa.memory_map(arrow_file, "r")).read_all()
                for arrow_file in arrow_files
            ]
        )

    def get(self, ids: np.ndarray, cols: Optional[list] = None):
        """Get arrow metadata from ids.

        Args:
            ids (np.ndarray): Ids to retrieve.
            cols (Optional[list], optional): Columns to retrieve. Defaults to None.
        """
        if cols is None:
            cols = self.table.schema.names
        else:
            cols = list(set(self.table.schema.names) & set(cols))
        t = pa.concat_tables([self.table[i:j] for i, j in zip(ids, ids + 1)])
        return t.select(cols).to_pandas().to_dict("records")


class CaSEDModel(PreTrainedModel):
    """Transformers module for Category Search from External Databases (CaSED).

    Reference:
        - Conti et al. Vocabulary-free Image Classification. arXiv 2023.

    Args:
        config (CaSEDConfig): Configuration class for CaSED.
    """

    config_class = CaSEDConfig

    def __init__(self, config: CaSEDConfig):
        super().__init__(config)

        # load CLIP
        model = CLIPModel.from_pretrained("openai/clip-vit-large-patch14")
        self.vision_encoder = model.vision_model
        self.vision_proj = model.visual_projection
        self.language_encoder = model.text_model
        self.language_proj = model.text_projection
        self.logit_scale = model.logit_scale.exp()
        self.processor = CLIPProcessor.from_pretrained("openai/clip-vit-large-patch14")

        # load transforms
        self.vocabulary_transforms = default_vocabulary_transforms()

        # set hparams
        self.hparams = {}
        self.hparams["alpha"] = config.alpha
        self.hparams["index_name"] = config.index_name
        self.hparams["retrieval_num_results"] = config.retrieval_num_results

        # set cache dir
        self.hparams["cache_dir"] = Path(os.path.expanduser("~/.cache/cased"))
        os.makedirs(self.hparams["cache_dir"], exist_ok=True)

        # download databases
        self.prepare_data()

        # load faiss indices and metadata providers
        self.resources = {}
        for name, items in DATABASES.items():
            database_path = self.hparams["cache_dir"] / "databases" / items["cache_subdir"]
            text_index_fp = database_path / "text.index"
            metadata_fp = database_path / "metadata/"

            text_index = faiss.read_index(
                str(text_index_fp), faiss.IO_FLAG_MMAP | faiss.IO_FLAG_READ_ONLY
            )
            metadata_provider = MetadataProvider(metadata_fp)

            self.resources[name] = {
                "device": self.device,
                "model": "ViT-L-14",
                "text_index": text_index,
                "metadata_provider": metadata_provider,
            }

    def prepare_data(self):
        """Download data if needed."""
        databases_path = Path(self.hparams["cache_dir"]) / "databases"

        for name, items in DATABASES.items():
            url = items["url"]
            database_path = Path(databases_path, name)
            if database_path.exists():
                continue

            # download data
            target_path = Path(databases_path, name + ".tar.gz")
            os.makedirs(target_path.parent, exist_ok=True)
            with requests.get(url, stream=True) as r:
                r.raise_for_status()
                total_bytes_size = int(r.headers.get('content-length', 0))
                chunk_size = 8192
                p_bar = tqdm(
                    desc="Downloading cc12m index",
                    total=total_bytes_size,
                    unit='iB',
                    unit_scale=True,
                )
                with open(target_path, 'wb') as f:
                    for chunk in r.iter_content(chunk_size=chunk_size):
                        f.write(chunk)
                        p_bar.update(len(chunk))
                p_bar.close()

            # extract data
            tar = tarfile.open(target_path, "r:gz")
            tar.extractall(target_path.parent)
            tar.close()
            target_path.unlink()

    @torch.no_grad()
    def query_index(self, sample_z: torch.Tensor) -> torch.Tensor:
        """Query the external database index.

        Args:
            sample_z (torch.Tensor): Sample to query the index.
        """
        # get the index
        resources = self.resources[self.hparams["index_name"]]
        text_index = resources["text_index"]
        metadata_provider = resources["metadata_provider"]

        # query the index
        sample_z = sample_z.squeeze(0)
        sample_z = sample_z / sample_z.norm(dim=-1, keepdim=True)
        query_input = sample_z.cpu().detach().numpy().tolist()
        query = np.expand_dims(np.array(query_input).astype("float32"), 0)

        distances, idxs, _ = text_index.search_and_reconstruct(
            query, self.hparams["retrieval_num_results"]
        )
        results = idxs[0]
        nb_results = np.where(results == -1)[0]
        nb_results = nb_results[0] if len(nb_results) > 0 else len(results)
        indices = results[:nb_results]
        distances = distances[0][:nb_results]

        if len(distances) == 0:
            return []

        # get the metadata
        results = []
        metadata = metadata_provider.get(indices[:20], ["caption"])
        for key, (d, i) in enumerate(zip(distances, indices)):
            output = {}
            meta = None if key + 1 > len(metadata) else metadata[key]
            if meta is not None:
                output.update(meta)
            output["id"] = i.item()
            output["similarity"] = d.item()
            results.append(output)

        # get the captions only
        vocabularies = [result["caption"] for result in results]

        return vocabularies

    @torch.no_grad()
    def forward(self, images: dict, alpha: Optional[float] = None) -> torch.Tensor():
        """Forward pass.

        Args:
            images (dict): Dictionary with the images. The expected keys are:
                - pixel_values (torch.Tensor): Pixel values of the images.
            alpha (Optional[float]): Alpha value for the interpolation.
        """
        # forward the images
        images["pixel_values"] = images["pixel_values"].to(self.device)
        images_z = self.vision_proj(self.vision_encoder(**images)[1])

        vocabularies, samples_p = [], []
        for image_z in images_z:
            image_z = image_z.unsqueeze(0)

            # generate a single text embedding from the unfiltered vocabulary
            vocabulary = self.query_index(image_z)
            text = self.processor(text=vocabulary, return_tensors="pt", padding=True)
            text["input_ids"] = text["input_ids"][:, :77].to(self.device)
            text["attention_mask"] = text["attention_mask"][:, :77].to(self.device)
            text_z = self.language_encoder(**text)[1]
            text_z = self.language_proj(text_z)
            text_z = text_z / text_z.norm(dim=-1, keepdim=True)
            text_z = text_z.mean(dim=0).unsqueeze(0)
            text_z = text_z / text_z.norm(dim=-1, keepdim=True)

            # filter the vocabulary, embed it, and get its mean embedding
            vocabulary = self.vocabulary_transforms(vocabulary) or ["object"]
            text = self.processor(text=vocabulary, return_tensors="pt", padding=True)
            text = {k: v.to(self.device) for k, v in text.items()}
            vocabulary_z = self.language_encoder(**text)[1]
            vocabulary_z = self.language_proj(vocabulary_z)
            vocabulary_z = vocabulary_z / vocabulary_z.norm(dim=-1, keepdim=True)

            # get the image and text predictions
            image_z = image_z / image_z.norm(dim=-1, keepdim=True)
            text_z = text_z / text_z.norm(dim=-1, keepdim=True)
            image_p = (self.logit_scale * image_z @ vocabulary_z.T).softmax(dim=-1)
            text_p = (self.logit_scale * text_z @ vocabulary_z.T).softmax(dim=-1)

            # average the image and text predictions
            alpha = alpha or self.hparams["alpha"]
            sample_p = alpha * image_p + (1 - alpha) * text_p

            # save the results
            samples_p.append(sample_p)
            vocabularies.append(vocabulary)

        # get the scores
        samples_p = torch.stack(samples_p, dim=0)
        scores = sample_p.cpu()

        # define the results
        results = {"vocabularies": vocabularies, "scores": scores}

        return results