import argparse
from itertools import compress, starmap
from operator import itemgetter
from pathlib import Path
from typing import Iterable

import torch
from detr.models import build_model
from detr.test import get_args_parser, infer
from iteration_utilities import starfilter

from fb_detr.utils.non_max_supprs import greedy_non_max_supprs
from fb_detr.utils.config import read_config


def load_model(checkpoint_path):

    parser = argparse.ArgumentParser(parents=[get_args_parser()])
    args = parser.parse_args()

    if args.output_dir:
        Path(args.output_dir).mkdir(parents=True, exist_ok=True)

    device = torch.device(read_config("device"))

    model, _, _ = build_model(args)

    checkpoint = torch.load(checkpoint_path, map_location="cpu")
    model.load_state_dict(checkpoint["model"])

    model.to(device)

    return model


class Predictor:
    def __init__(self, checkpoint_path, classes=None, rejection_class=None):
        self.model = load_model(checkpoint_path)
        self.classes = classes
        self.rejection_class = rejection_class

    @staticmethod
    def __format_boxes(boxes):

        keys = "x1", "y1", "x2", "y2"

        x1s = boxes[:, 0].tolist()
        y1s = boxes[:, 1].tolist()
        x2s = boxes[:, 2].tolist()
        y2s = boxes[:, 3].tolist()

        boxes = [dict(zip(keys, vs)) for vs in zip(x1s, y1s, x2s, y2s)]

        return boxes

    @staticmethod
    def __normalize_to_list(maybe_multiple):
        return maybe_multiple if isinstance(maybe_multiple, tuple) else tuple([maybe_multiple])

    def __format_classes(self, classes):
        if self.classes:
            return self.__normalize_to_list(itemgetter(*classes.tolist())(self.classes))
        else:
            return classes.tolist()

    @staticmethod
    def __format_probas(probas):
        return probas.max(axis=1).tolist()

    def __format_prediction(self, predictions: dict):

        boxes, classes, probas = itemgetter("bboxes", "classes", "probas")(predictions)

        if len(boxes):
            boxes = self.__format_boxes(boxes)
            classes = self.__format_classes(classes)
            probas = self.__format_probas(probas)
        else:
            boxes, classes, probas = [], [], []

        predictions["bboxes"] = boxes
        predictions["classes"] = classes
        predictions["probas"] = probas

        return predictions

    def __filter_predictions_for_image(self, predictions):

        boxes, classes, probas = itemgetter("bboxes", "classes", "probas")(predictions)

        if boxes:
            keep = map(lambda c: c != self.rejection_class, classes)
            compressed = list(compress(zip(boxes, classes, probas), keep))
            boxes, classes, probas = map(list, zip(*compressed)) if compressed else ([], [], [])
            predictions["bboxes"] = boxes
            predictions["classes"] = classes
            predictions["probas"] = probas

        return predictions

    def filter_predictions(self, predictions):
        def detections_present(_, prediction):
            return bool(prediction["classes"])

        def build_return_dict(page_idx, predictions):
            return {"page_idx": page_idx, **predictions}

        filtered_rejections = map(self.__filter_predictions_for_image, predictions)
        filtered_no_detections = starfilter(detections_present, enumerate(filtered_rejections))
        filtered_no_detections = starmap(build_return_dict, filtered_no_detections)

        return filtered_no_detections

    def format_predictions(self, outputs: Iterable):
        return map(self.__format_prediction, outputs)

    def __merge_boxes(self, predictions):
        predictions = map(greedy_non_max_supprs, predictions)
        return predictions

    def predict(self, images, threshold=None):

        if not threshold:
            threshold = read_config("threshold")

        predictions = infer(images, self.model, read_config("device"), threshold)
        predictions = self.format_predictions(predictions)
        if self.rejection_class:
            predictions = self.filter_predictions(predictions)

        predictions = self.__merge_boxes(predictions)

        predictions = list(predictions)

        return predictions