import pandas as pd
import numpy as np
from sklearn.cluster import DBSCAN,OPTICS
from math import radians, cos, sin, asin, sqrt

def filterDatafromDf(origDf):
    
    return origDf[origDf['local_hour']<=6]

def distance_to_degrees(d):
    #Just an approximation, but speeds up clustering by a huge amount and doesnt introduce much error
    #over small distances
    d = d / 1852
    d = d / 60
    return d

def cluster_and_label(df,clustering_algorithm,threshold_static,**kwargs):
    """

    :param df:   a df with columns "latitude", "longitude", and "datetime"
                                     or
               a df with comlumns "latitude","longitude" and a datetime index
    :param kwargs: arguments for sklearn's DBSCAN
    :return: a new df of labeled locations with moving points removed, where the cluster
             labeled as "1" is the largest, "2" the second largest, and so on
    """
    if not df.empty:
        location_data = df
        if not isinstance(df.index, pd.DatetimeIndex):
            location_data = df.set_index("local_date_time")

        stationary = mark_moving(location_data,threshold_static)

        counts_df = stationary[["double_latitude" ,"double_longitude"]].groupby(["double_latitude" ,"double_longitude"]).size().reset_index()
        counts = counts_df[0]
        lat_lon = counts_df[["double_latitude","double_longitude"]].values

        if clustering_algorithm == "DBSCAN":
            clusterer = DBSCAN(**kwargs)
            cluster_results = clusterer.fit_predict(lat_lon, sample_weight= counts)
        else:
            clusterer = OPTICS(**kwargs)
            cluster_results = clusterer.fit_predict(lat_lon)

        #Need to extend labels back to original df without weights
        counts_df["location_label"] = cluster_results
        # remove the old count column
        del counts_df[0]

        merged = pd.merge(stationary,counts_df, on = ["double_latitude" ,"double_longitude"])

        #Now compute the label mapping:
        cluster_results = merged["location_label"].values
        valid_clusters = cluster_results[np.where(cluster_results != -1)]
        label_map = rank_count_map(valid_clusters)

        #And remap the labels:
        merged.index = stationary.index
        stationary = stationary.assign(location_label = merged["location_label"].map(label_map).values)
        stationary.loc[:, "location_label"] = merged["location_label"].map(label_map)
        return stationary
    else:
        return df
    
def rank_count_map(clusters):
    """ Returns a function which will map each element of a list 'l' to its rank,
    such that the most common element maps to 1

    Is used in this context to sort the cluster labels so that cluster with rank 1 is the most
    visited.

    If return_dict, return a mapping dict rather than a function

    If a function, if the value can't be found label as -1

    """
    labels, counts = tuple(np.unique(clusters, return_counts = True))
    sorted_by_count = [x for (y,x) in sorted(zip(counts, labels), reverse = True)]
    label_to_rank = {label : rank + 1 for (label, rank) in [(sorted_by_count[i],i) for i in range(len(sorted_by_count))]}
    return lambda x: label_to_rank.get(x, -1)


def mark_moving(df, threshold_static):

    if not df.index.is_monotonic:
        df = df.sort_index()

    distance = haversine(df.double_longitude,df.double_latitude,df.double_longitude.shift(-1),df.double_latitude.shift(-1))/ 1000
    time = (df.timestamp.diff(-1) * -1) / (1000*60*60)
    
    df['stationary_or_not'] = np.where((distance / time) < threshold_static,1,0)   # 1 being stationary,0 for moving 

    return df

def haversine(lon1,lat1,lon2,lat2):
    """
    Calculate the great circle distance between two points 
    on the earth (specified in decimal degrees)
    """
    # convert decimal degrees to radians 
    lon1, lat1, lon2, lat2 = np.radians([lon1, lat1, lon2, lat2])

    # haversine formula 
    a = np.sin((lat2-lat1)/2.0)**2 + np.cos(lat1) * np.cos(lat2) * np.sin((lon2-lon1)/2.0)**2

    r = 6371 # Radius of earth in kilometers. Use 3956 for miles

    return (r * 2 * np.arcsin(np.sqrt(a)) * 1000)

# Infer a participants home location

origDf = pd.read_csv(snakemake.input[0])
filteredDf = filterDatafromDf(origDf)
if filteredDf.empty:
    filteredDf.to_csv(snakemake.output[0])
else:
    dbscan_eps = snakemake.params["dbscan_eps"]
    dbscan_minsamples = snakemake.params["dbscan_minsamples"]
    threshold_static = snakemake.params["threshold_static"]
    clustering_algorithm = snakemake.params["clustering_algorithm"]

    if clustering_algorithm == "DBSCAN":
        hyperparameters = {'eps' : distance_to_degrees(dbscan_eps), 'min_samples': dbscan_minsamples}
    elif clustering_algorithm == "OPTICS":
        hyperparameters = {'max_eps': distance_to_degrees(dbscan_eps), 'min_samples': 2, 'metric':'euclidean', 'cluster_method' : 'dbscan'} 
    else:
        raise ValueError("config[PHONE_LOCATIONS][HOME_INFERENCE][CLUSTERING ALGORITHM] only accepts DBSCAN or OPTICS but you provided ",clustering_algorithm)

    filteredDf = cluster_and_label(filteredDf,clustering_algorithm,threshold_static,**hyperparameters)

    origDf['home_latitude'] = filteredDf[filteredDf['location_label']==1][['double_latitude','double_longitude']].mean()['double_latitude']
    origDf['home_longitude'] = filteredDf[filteredDf['location_label']==1][['double_latitude','double_longitude']].mean()['double_longitude']

    distanceFromHome = haversine(origDf.double_longitude,origDf.double_latitude,origDf.home_longitude,origDf.home_latitude)

    finalDf = origDf.drop(['home_latitude','home_longitude'], axis=1)
    finalDf.insert(len(finalDf.columns)-1,'distancefromhome',distanceFromHome)
    finalDf.to_csv(snakemake.output[0], index=False)