import logging
from contextlib import suppress

import torch
import torch.nn.functional as F
from tqdm import tqdm

from open_clip import tokenize
from .imagenet_zeroshot_data import imagenet_classnames, openai_imagenet_template


def zero_shot_classifier(model, classnames, templates, args):
    with torch.no_grad():
        zeroshot_weights = []
        for classname in tqdm(classnames):
            texts = [template(classname) for template in templates]  # format with class
            texts = tokenize(texts).to(args.device)  # tokenize
            if args.distributed and not args.horovod:
                class_embeddings = model.module.encode_text(texts)
            else:
                class_embeddings = model.encode_text(texts)
            class_embedding = F.normalize(class_embeddings, dim=-1).mean(dim=0)
            class_embedding /= class_embedding.norm()
            zeroshot_weights.append(class_embedding)
        zeroshot_weights = torch.stack(zeroshot_weights, dim=1).to(args.device)
    return zeroshot_weights


def accuracy(output, target, topk=(1,)):
    pred = output.topk(max(topk), 1, True, True)[1].t()
    correct = pred.eq(target.view(1, -1).expand_as(pred))
    return [
        float(correct[:k].reshape(-1).float().sum(0, keepdim=True).cpu().numpy())
        for k in topk
    ]


def run(model, classifier, dataloader, args):
    autocast = torch.cuda.amp.autocast if args.precision == "amp" else suppress
    with torch.no_grad():
        top1, top5, n = 0.0, 0.0, 0.0
        for images, target in tqdm(dataloader, unit_scale=args.batch_size):
            images = images.to(args.device)
            target = target.to(args.device)

            with autocast():
                # predict
                if args.distributed and not args.horovod:
                    image_features = model.module.encode_image(images)
                else:
                    image_features = model.encode_image(images)
                image_features = F.normalize(image_features, dim=-1)
                logits = 100.0 * image_features @ classifier

            # measure accuracy
            acc1, acc5 = accuracy(logits, target, topk=(1, 5))
            top1 += acc1
            top5 += acc5
            n += images.size(0)

    top1 = top1 / n
    top5 = top5 / n
    return top1, top5


def zero_shot_eval(model, data, epoch, args):
    if "imagenet-val" not in data and "imagenet-v2" not in data:
        return {}
    if args.zeroshot_frequency == 0:
        return {}
    if (epoch % args.zeroshot_frequency) != 0 and epoch != args.epochs:
        return {}

    logging.info("Starting zero-shot imagenet.")

    logging.info("Building zero-shot classifier")
    classifier = zero_shot_classifier(
        model, imagenet_classnames, openai_imagenet_template, args
    )

    logging.info("Using classifier")
    results = {}
    if "imagenet-val" in data:
        top1, top5 = run(model, classifier, data["imagenet-val"].dataloader, args)
        results["imagenet-zeroshot-val-top1"] = top1
        results["imagenet-zeroshot-val-top5"] = top5
    if "imagenet-v2" in data:
        top1, top5 = run(model, classifier, data["imagenet-v2"].dataloader, args)
        results["imagenetv2-zeroshot-val-top1"] = top1
        results["imagenetv2-zeroshot-val-top5"] = top5

    logging.info("Finished zero-shot imagenet.")

    return results
