# ActivitySim
# See full license in LICENSE.txt.
from builtins import range

import logging

import numpy as np
import pandas as pd

from activitysim.core import tracing
from activitysim.core import config
from activitysim.core import pipeline
from activitysim.core import simulate
from activitysim.core import inject
from activitysim.core import los
from activitysim.core import assign
from activitysim.core import expressions

from activitysim.core.tracing import print_elapsed_time

from activitysim.core.util import reindex
from activitysim.core.util import assign_in_place

from activitysim.core.pathbuilder import TransitVirtualPathBuilder

from activitysim.abm.tables.size_terms import tour_destination_size_terms

from activitysim.core.skim_dictionary import DataFrameMatrix

from activitysim.core.interaction_sample_simulate import interaction_sample_simulate
from activitysim.core.interaction_sample import interaction_sample

from .util import estimation

from activitysim.abm.models.util.trip import cleanup_failed_trips
from activitysim.abm.models.util.trip import flag_failed_trip_leg_mates


logger = logging.getLogger(__name__)

NO_DESTINATION = -1

TRIP_ORIG_TAZ = 'TAZ'
ALT_DEST_TAZ = 'ALT_DEST_TAZ'
PRIMARY_DEST_TAZ = 'PRIMARY_DEST_TAZ'
DEST_MAZ = 'dest_maz'


def _destination_sample(
        primary_purpose,
        trips,
        alternatives,
        model_settings,
        size_term_matrix,
        skims,
        alt_dest_col_name,
        estimator,
        chunk_size,
        chunk_tag,
        trace_label):
    """

    Note: trips with no viable destination receive no sample rows
    (because we call interaction_sample with allow_zero_probs=True)
    All other trips will have one or more rows with pick_count summing to sample_size

    returns
        choices: pandas.DataFrame

               alt_dest      prob  pick_count
    trip_id
    102829169      2898  0.002333           1
    102829169      2901  0.004976           1
    102829169      3193  0.002628           1
    """

    spec = simulate.spec_for_segment(model_settings, spec_id='DESTINATION_SAMPLE_SPEC',
                                     segment_name=primary_purpose, estimator=estimator)

    sample_size = model_settings['SAMPLE_SIZE']
    if config.setting('disable_destination_sampling', False) or (estimator and estimator.want_unsampled_alternatives):
        # FIXME interaction_sample will return unsampled complete alternatives with probs and pick_count
        logger.info("Estimation mode for %s using unsampled alternatives short_circuit_choices" % (trace_label,))
        sample_size = 0

    locals_dict = config.get_model_constants(model_settings).copy()

    # size_terms of destination zones are purpose-specific, and trips have various purposes
    # so the relevant size_term for each interaction_sample row
    # cannot be determined until after choosers are joined with alternatives
    # (unless we iterate over trip.purpose - which we could, though we are already iterating over trip_num)
    # so, instead, expressions determine row-specific size_term by a call to: size_terms.get(df.alt_dest, df.purpose)
    locals_dict.update({
        'size_terms': size_term_matrix
    })
    locals_dict.update(skims)

    log_alt_losers = config.setting('log_alt_losers', False)

    choices = interaction_sample(
        choosers=trips,
        alternatives=alternatives,
        sample_size=sample_size,
        alt_col_name=alt_dest_col_name,
        log_alt_losers=log_alt_losers,
        allow_zero_probs=True,
        spec=spec,
        skims=skims,
        locals_d=locals_dict,
        chunk_size=chunk_size, chunk_tag=chunk_tag,
        trace_label=trace_label
        )

    return choices


def destination_sample(
        primary_purpose,
        trips,
        alternatives,
        model_settings,
        size_term_matrix,
        skim_hotel,
        estimator,
        chunk_size,
        trace_label):

    chunk_tag = 'trip_destination.sample'

    skims = skim_hotel.sample_skims(presample=False)
    alt_dest_col_name = model_settings['ALT_DEST_COL_NAME']

    choices = _destination_sample(
        primary_purpose,
        trips,
        alternatives,
        model_settings,
        size_term_matrix,
        skims,
        alt_dest_col_name,
        estimator,
        chunk_size,
        chunk_tag=chunk_tag,
        trace_label=trace_label)

    return choices


def aggregate_size_term_matrix(maz_size_term_matrix, maz_taz):

    df = maz_size_term_matrix.df
    assert ALT_DEST_TAZ not in df

    dest_taz = df.index.map(maz_taz)
    maz_size_term_matrix = df.groupby(dest_taz).sum()

    maz_size_term_matrix = DataFrameMatrix(maz_size_term_matrix)

    return maz_size_term_matrix


def choose_MAZ_for_TAZ(taz_sample, MAZ_size_terms, trips, network_los, alt_dest_col_name, trace_label):
    """
    Convert taz_sample table with TAZ zone sample choices to a table with a MAZ zone chosen for each TAZ
    choose MAZ probabilistically (proportionally by size_term) from set of MAZ zones in parent TAZ

    Parameters
    ----------
    taz_sample: dataframe with duplicated index <chooser_id_col> and columns: <alt_dest_col_name>, prob, pick_count
    MAZ_size_terms: dataframe with duplicated index <chooser_id_col> and columns: zone_id, dest_TAZ, size_term

    Returns
    -------
    dataframe with with duplicated index <chooser_id_col> and columns: <alt_dest_col_name>, prob, pick_count
    """

    if len(taz_sample) == 0:
        # it can happen that all trips have no viable destinations (and so are dropped from the sample)
        # in which case we can just return the empty taz_sample, since it has the same columns
        return taz_sample.copy()

    # we had to use alt_dest_col_name as specified in model_settings for interaction_sample
    # because expressions reference it to look up size_terms by trip purpose
    DEST_MAZ = alt_dest_col_name
    DEST_TAZ = f"{alt_dest_col_name}_TAZ"

    taz_sample.rename(columns={alt_dest_col_name: DEST_TAZ}, inplace=True)

    trace_hh_id = inject.get_injectable("trace_hh_id", None)
    have_trace_targets = trace_hh_id and tracing.has_trace_targets(taz_sample)
    if have_trace_targets:
        trace_label = tracing.extend_trace_label(trace_label, 'choose_MAZ_for_TAZ')

        # write taz choices, pick_counts, probs
        trace_targets = tracing.trace_targets(taz_sample)
        tracing.trace_df(taz_sample[trace_targets],
                         label=tracing.extend_trace_label(trace_label, 'taz_sample'),
                         transpose=False)

    # print(f"taz_sample\n{taz_sample}")
    #            alt_dest_TAZ      prob  pick_count
    # trip_id
    # 4343721              12  0.000054           1
    # 4343721              20  0.001864           2

    taz_choices = taz_sample[[DEST_TAZ, 'prob']].reset_index(drop=False)
    taz_choices = taz_choices.reindex(taz_choices.index.repeat(taz_sample.pick_count)).reset_index(drop=True)
    taz_choices = taz_choices.rename(columns={'prob': 'TAZ_prob'})

    # print(f"taz_choices\n{taz_choices}")
    #         trip_id  alt_dest_TAZ      prob
    # 0       4343721            12  0.000054
    # 1       4343721            20  0.001864
    # 2       4343721            20  0.001864

    # print(f"MAZ_size_terms\n{MAZ_size_terms.df}")
    #           work  escort  shopping  eatout  othmaint  social  othdiscr   univ
    # alt_dest
    # 2         31.0   9.930     0.042   0.258     0.560   0.520    10.856  0.042
    # 3          0.0   3.277     0.029   0.000     0.029   0.029     7.308  0.029
    # 4          0.0   1.879     0.023   0.000     0.023   0.023     5.796  0.023

    # just to make it clear we are siloing choices by chooser_id
    chooser_id_col = taz_sample.index.name  # should be canonical chooser index name (e.g. 'trip_id')

    # for random_for_df, we need df with de-duplicated chooser canonical index
    chooser_df = pd.DataFrame(index=taz_sample.index[~taz_sample.index.duplicated()])
    num_choosers = len(chooser_df)
    assert chooser_df.index.name == chooser_id_col

    # to make choices, <taz_sample_size> rands for each chooser (one rand for each sampled TAZ)
    # taz_sample_size will be model_settings['SAMPLE_SIZE'] samples, except if we are estimating
    taz_sample_size = taz_choices.groupby(chooser_id_col)[DEST_TAZ].count().max()

    # taz_choices index values should be contiguous
    assert (taz_choices[chooser_id_col] == np.repeat(chooser_df.index, taz_sample_size)).all()

    # we need to choose a MAZ for each DEST_TAZ choice
    # probability of choosing MAZ based on MAZ size_term fraction of TAZ total
    # there will be a different set (and number) of candidate MAZs for each TAZ
    # (preserve index, which will have duplicates as result of join)

    maz_taz = network_los.maz_taz_df[['MAZ', 'TAZ']].rename(columns={'TAZ': DEST_TAZ, 'MAZ': DEST_MAZ})
    maz_sizes = pd.merge(taz_choices[[chooser_id_col, DEST_TAZ]].reset_index(),
                         maz_taz,
                         how='left', on=DEST_TAZ).set_index('index')

    purpose = maz_sizes['trip_id'].map(trips.purpose)  # size term varies by purpose
    maz_sizes['size_term'] = MAZ_size_terms.get(maz_sizes[DEST_MAZ], purpose)

    # print(f"maz_sizes\n{maz_sizes}")
    #          trip_id  alt_dest_TAZ  alt_dest  size_term
    # index
    # 0        4343721            12      3445      0.019
    # 0        4343721            12     11583      0.017
    # 0        4343721            12     21142      0.020

    if have_trace_targets:
        # write maz_sizes: maz_sizes[index,trip_id,dest_TAZ,zone_id,size_term]
        maz_sizes_trace_targets = tracing.trace_targets(maz_sizes, slicer='trip_id')
        trace_maz_sizes = maz_sizes[maz_sizes_trace_targets]
        tracing.trace_df(trace_maz_sizes,
                         label=tracing.extend_trace_label(trace_label, 'maz_sizes'),
                         transpose=False)

    # number of DEST_TAZ candidates per chooser
    maz_counts = maz_sizes.groupby(maz_sizes.index).size().values
    # print(maz_counts)

    # max number of MAZs for any TAZ
    max_maz_count = maz_counts.max()
    # print(f"max_maz_count {max_maz_count}")

    # offsets of the first and last rows of each chooser in sparse interaction_utilities
    last_row_offsets = maz_counts.cumsum()
    first_row_offsets = np.insert(last_row_offsets[:-1], 0, 0)

    # repeat the row offsets once for each dummy utility to insert
    # (we want to insert dummy utilities at the END of the list of alternative utilities)
    # inserts is a list of the indices at which we want to do the insertions
    inserts = np.repeat(last_row_offsets, max_maz_count - maz_counts)

    # insert zero filler to pad each alternative set to same size
    padded_maz_sizes = np.insert(maz_sizes.size_term.values, inserts, 0.0)
    padded_maz_sizes = padded_maz_sizes.reshape(-1, max_maz_count)

    # prob array with one row TAZ_choice, one column per alternative
    row_sums = padded_maz_sizes.sum(axis=1)
    maz_probs = np.divide(padded_maz_sizes, row_sums.reshape(-1, 1))
    assert maz_probs.shape == (num_choosers * taz_sample_size, max_maz_count)

    rands = pipeline.get_rn_generator().random_for_df(chooser_df, n=taz_sample_size).reshape(-1, 1)
    assert len(rands) == num_choosers * taz_sample_size
    assert len(rands) == maz_probs.shape[0]

    # make choices
    # positions is array with the chosen alternative represented as a column index in probs
    # which is an integer between zero and max_maz_count
    positions = np.argmax((maz_probs.cumsum(axis=1) - rands) > 0.0, axis=1)

    # shouldn't have chosen any of the dummy pad positions
    assert (positions < maz_counts).all()

    taz_choices[DEST_MAZ] = maz_sizes[DEST_MAZ].take(positions + first_row_offsets)
    taz_choices['MAZ_prob'] = maz_probs[np.arange(maz_probs.shape[0]), positions]
    taz_choices['prob'] = taz_choices['TAZ_prob'] * taz_choices['MAZ_prob']

    if have_trace_targets:

        taz_choices_trace_targets = tracing.trace_targets(taz_choices, slicer='trip_id')
        trace_taz_choices_df = taz_choices[taz_choices_trace_targets]
        tracing.trace_df(trace_taz_choices_df,
                         label=tracing.extend_trace_label(trace_label, 'taz_choices'),
                         transpose=False)

        lhs_df = trace_taz_choices_df[['trip_id', DEST_TAZ]]
        alt_dest_columns = [f'dest_maz_{c}' for c in range(max_maz_count)]

        # following the same logic as the full code, but for trace cutout
        trace_maz_counts = maz_counts[taz_choices_trace_targets]
        trace_last_row_offsets = maz_counts[taz_choices_trace_targets].cumsum()
        trace_inserts = np.repeat(trace_last_row_offsets, max_maz_count - trace_maz_counts)

        # trace dest_maz_alts
        padded_maz_sizes = np.insert(trace_maz_sizes[DEST_MAZ].values, trace_inserts, 0.0).reshape(-1, max_maz_count)
        df = pd.DataFrame(data=padded_maz_sizes,
                          columns=alt_dest_columns, index=trace_taz_choices_df.index)
        df = pd.concat([lhs_df, df], axis=1)
        tracing.trace_df(df, label=tracing.extend_trace_label(trace_label, 'dest_maz_alts'), transpose=False)

        # trace dest_maz_size_terms
        padded_maz_sizes = np.insert(trace_maz_sizes['size_term'].values, trace_inserts, 0.0).reshape(-1, max_maz_count)
        df = pd.DataFrame(data=padded_maz_sizes,
                          columns=alt_dest_columns, index=trace_taz_choices_df.index)
        df = pd.concat([lhs_df, df], axis=1)
        tracing.trace_df(df, label=tracing.extend_trace_label(trace_label, 'dest_maz_size_terms'), transpose=False)

        # trace dest_maz_probs
        df = pd.DataFrame(data=maz_probs[taz_choices_trace_targets],
                          columns=alt_dest_columns, index=trace_taz_choices_df.index)
        df = pd.concat([lhs_df, df], axis=1)
        df['rand'] = rands[taz_choices_trace_targets]
        tracing.trace_df(df, label=tracing.extend_trace_label(trace_label, 'dest_maz_probs'), transpose=False)

    taz_choices = taz_choices.drop(columns=['TAZ_prob', 'MAZ_prob'])
    taz_choices = taz_choices.groupby([chooser_id_col, DEST_MAZ]).agg(prob=('prob', 'max'),
                                                                      pick_count=('prob', 'count'))

    taz_choices.reset_index(level=DEST_MAZ, inplace=True)

    return taz_choices


def destination_presample(
        primary_purpose,
        trips,
        alternatives,
        model_settings,
        size_term_matrix,
        skim_hotel,
        network_los,
        estimator,
        chunk_size, trace_hh_id,
        trace_label):

    trace_label = tracing.extend_trace_label(trace_label, 'presample')
    chunk_tag = 'trip_destination.presample'  # distinguish from trip_destination.sample

    alt_dest_col_name = model_settings['ALT_DEST_COL_NAME']
    maz_taz = network_los.maz_taz_df[['MAZ', 'TAZ']].set_index('MAZ').TAZ

    TAZ_size_term_matrix = aggregate_size_term_matrix(size_term_matrix, maz_taz)

    TRIP_ORIGIN = model_settings['TRIP_ORIGIN']
    PRIMARY_DEST = model_settings['PRIMARY_DEST']
    trips = trips.copy()

    trips[TRIP_ORIGIN] = trips[TRIP_ORIGIN].map(maz_taz)
    trips[PRIMARY_DEST] = trips[PRIMARY_DEST].map(maz_taz)

    # alternatives is just an empty dataframe indexed by maz with index name <alt_dest_col_name>
    # but logically, we are aggregating so lets do it, as there is no particular gain in being clever
    alternatives = alternatives.groupby(alternatives.index.map(maz_taz)).sum()

    skims = skim_hotel.sample_skims(presample=True)

    taz_sample = _destination_sample(
        primary_purpose,
        trips,
        alternatives,
        model_settings,
        TAZ_size_term_matrix,
        skims,
        alt_dest_col_name,
        estimator,
        chunk_size,
        chunk_tag=chunk_tag,
        trace_label=trace_label)

    # choose a MAZ for each DEST_TAZ choice, choice probability based on MAZ size_term fraction of TAZ total
    maz_sample = choose_MAZ_for_TAZ(taz_sample, size_term_matrix, trips, network_los, alt_dest_col_name, trace_label)

    assert alt_dest_col_name in maz_sample

    return maz_sample


def trip_destination_sample(
        primary_purpose,
        trips,
        alternatives,
        model_settings,
        size_term_matrix,
        skim_hotel,
        estimator,
        chunk_size, trace_hh_id,
        trace_label):
    """

    Returns
    -------
    destination_sample: pandas.dataframe
        choices_df from interaction_sample with (up to) sample_size alts for each chooser row
        index (non unique) is trip_id from trips (duplicated for each alt)
        and columns dest_zone_id, prob, and pick_count

        dest_zone_id: int
            alt identifier from alternatives[<alt_col_name>]
        prob: float
            the probability of the chosen alternative
        pick_count : int
            number of duplicate picks for chooser, alt
    """
    trace_label = tracing.extend_trace_label(trace_label, 'sample')

    assert len(trips) > 0
    assert len(alternatives) > 0

    # by default, enable presampling for multizone systems, unless they disable it in settings file
    network_los = inject.get_injectable('network_los')
    pre_sample_taz = not (network_los.zone_system == los.ONE_ZONE)
    if pre_sample_taz and not config.setting('want_dest_choice_presampling', True):
        pre_sample_taz = False
        logger.info(f"Disabled destination zone presampling for {trace_label} "
                    f"because 'want_dest_choice_presampling' setting is False")

    if pre_sample_taz:

        logger.info("Running %s trip_destination_presample with %d trips" % (trace_label, len(trips)))

        choices = destination_presample(
            primary_purpose,
            trips,
            alternatives,
            model_settings,
            size_term_matrix,
            skim_hotel,
            network_los,
            estimator,
            chunk_size, trace_hh_id,
            trace_label)

    else:
        choices = destination_sample(
            primary_purpose,
            trips,
            alternatives,
            model_settings,
            size_term_matrix,
            skim_hotel,
            estimator,
            chunk_size,
            trace_label)

    return choices


def compute_ood_logsums(
        choosers,
        logsum_settings,
        nest_spec, logsum_spec,
        od_skims,
        locals_dict,
        chunk_size,
        trace_label,
        chunk_tag):
    """
    Compute one (of two) out-of-direction logsums for destination alternatives

    Will either be trip_origin -> alt_dest or alt_dest -> primary_dest
    """

    locals_dict.update(od_skims)

    expressions.annotate_preprocessors(
        choosers, locals_dict, od_skims,
        logsum_settings,
        trace_label)

    logsums = simulate.simple_simulate_logsums(
        choosers,
        logsum_spec,
        nest_spec,
        skims=od_skims,
        locals_d=locals_dict,
        chunk_size=chunk_size,
        trace_label=trace_label,
        chunk_tag=chunk_tag)

    assert logsums.index.equals(choosers.index)

    # FIXME not strictly necessary, but would make trace files more legible?
    # logsums = logsums.replace(-np.inf, -999)

    return logsums


def compute_logsums(
        primary_purpose,
        trips,
        destination_sample,
        tours_merged,
        model_settings,
        skim_hotel,
        chunk_size,
        trace_label):
    """
    Calculate mode choice logsums using the same recipe as for trip_mode_choice, but do it twice
    for each alternative since we need out-of-direction logsum
    (i.e . origin to alt_dest, and alt_dest to half-tour destination)

    Returns
    -------
        adds od_logsum and dp_logsum columns to trips (in place)
    """
    trace_label = tracing.extend_trace_label(trace_label, 'compute_logsums')
    logger.info("Running %s with %d samples", trace_label, destination_sample.shape[0])

    # chunk usage is uniform so better to combine
    chunk_tag = 'trip_destination.compute_logsums'

    # FIXME should pass this in?
    network_los = inject.get_injectable('network_los')

    # - trips_merged - merge trips and tours_merged
    trips_merged = pd.merge(
        trips,
        tours_merged,
        left_on='tour_id',
        right_index=True,
        how="left")
    assert trips_merged.index.equals(trips.index)

    # - choosers - merge destination_sample and trips_merged
    # re/set index because pandas merge does not preserve left index if it has duplicate values!
    choosers = pd.merge(destination_sample,
                        trips_merged.reset_index(),
                        left_index=True,
                        right_on='trip_id',
                        how="left",
                        suffixes=('', '_r')).set_index('trip_id')
    assert choosers.index.equals(destination_sample.index)

    logsum_settings = config.read_model_settings(model_settings['LOGSUM_SETTINGS'])
    coefficients = simulate.get_segment_coefficients(logsum_settings, primary_purpose)

    nest_spec = config.get_logit_model_settings(logsum_settings)
    nest_spec = simulate.eval_nest_coefficients(nest_spec, coefficients, trace_label)

    logsum_spec = simulate.read_model_spec(file_name=logsum_settings['SPEC'])
    logsum_spec = simulate.eval_coefficients(logsum_spec, coefficients, estimator=None)

    locals_dict = {}
    locals_dict.update(config.get_model_constants(logsum_settings))

    # coefficients can appear in expressions
    locals_dict.update(coefficients)

    skims = skim_hotel.logsum_skims()
    if network_los.zone_system == los.THREE_ZONE:
        # TVPB constants can appear in expressions
        locals_dict.update(network_los.setting('TVPB_SETTINGS.tour_mode_choice.CONSTANTS'))

    # - od_logsums
    od_skims = {
        'ORIGIN': model_settings['TRIP_ORIGIN'],
        'DESTINATION': model_settings['ALT_DEST_COL_NAME'],
        "odt_skims": skims['odt_skims'],
        "dot_skims": skims['dot_skims'],
        "od_skims": skims['od_skims'],
    }
    if network_los.zone_system == los.THREE_ZONE:
        od_skims.update({
            'tvpb_logsum_odt':  skims['tvpb_logsum_odt'],
            'tvpb_logsum_dot': skims['tvpb_logsum_dot']
        })
    destination_sample['od_logsum'] = compute_ood_logsums(
        choosers,
        logsum_settings,
        nest_spec, logsum_spec,
        od_skims,
        locals_dict,
        chunk_size,
        trace_label=tracing.extend_trace_label(trace_label, 'od'),
        chunk_tag=chunk_tag)

    # - dp_logsums
    dp_skims = {
        'ORIGIN': model_settings['ALT_DEST_COL_NAME'],
        'DESTINATION': model_settings['PRIMARY_DEST'],
        "odt_skims": skims['dpt_skims'],
        "dot_skims": skims['pdt_skims'],
        "od_skims": skims['dp_skims'],
    }
    if network_los.zone_system == los.THREE_ZONE:
        dp_skims.update({
            'tvpb_logsum_odt':  skims['tvpb_logsum_dpt'],
            'tvpb_logsum_dot': skims['tvpb_logsum_pdt']
        })

    destination_sample['dp_logsum'] = compute_ood_logsums(
        choosers,
        logsum_settings,
        nest_spec, logsum_spec,
        dp_skims,
        locals_dict,
        chunk_size,
        trace_label=tracing.extend_trace_label(trace_label, 'dp'),
        chunk_tag=chunk_tag)

    return destination_sample


def trip_destination_simulate(
        primary_purpose,
        trips,
        destination_sample,
        model_settings,
        want_logsums,
        size_term_matrix,
        skim_hotel,
        estimator,
        chunk_size, trace_hh_id,
        trace_label):
    """
    Chose destination from destination_sample (with od_logsum and dp_logsum columns added)


    Returns
    -------
    choices - pandas.Series
        destination alt chosen
    """
    trace_label = tracing.extend_trace_label(trace_label, 'trip_dest_simulate')
    chunk_tag = 'trip_destination.simulate'

    spec = simulate.spec_for_segment(model_settings, spec_id='DESTINATION_SPEC',
                                     segment_name=primary_purpose, estimator=estimator)

    if estimator:
        estimator.write_choosers(trips)

    alt_dest_col_name = model_settings['ALT_DEST_COL_NAME']

    logger.info("Running trip_destination_simulate with %d trips", len(trips))

    skims = skim_hotel.sample_skims(presample=False)

    locals_dict = config.get_model_constants(model_settings).copy()
    locals_dict.update({
        'size_terms': size_term_matrix
    })
    locals_dict.update(skims)

    log_alt_losers = config.setting('log_alt_losers', False)

    destinations = interaction_sample_simulate(
        choosers=trips,
        alternatives=destination_sample,
        spec=spec,
        choice_column=alt_dest_col_name,
        log_alt_losers=log_alt_losers,
        want_logsums=want_logsums,
        allow_zero_probs=True, zero_prob_choice_val=NO_DESTINATION,
        skims=skims,
        locals_d=locals_dict,
        chunk_size=chunk_size, chunk_tag=chunk_tag,
        trace_label=trace_label,
        trace_choice_name='trip_dest',
        estimator=estimator)

    if not want_logsums:
        # for consistency, always return a dataframe with canonical column name
        assert isinstance(destinations, pd.Series)
        destinations = destinations.to_frame('choice')

    if estimator:
        # need to overwrite choices here before any failed choices are suppressed
        estimator.write_choices(destinations.choice)

        destinations.choice = estimator.get_survey_values(destinations.choice, 'trips', 'destination')
        estimator.write_override_choices(destinations.choice)

    # drop any failed zero_prob destinations
    if (destinations.choice == NO_DESTINATION).any():
        # logger.debug("dropping %s failed destinations", (destinations == NO_DESTINATION).sum())
        destinations = destinations[destinations.choice != NO_DESTINATION]

    return destinations


def choose_trip_destination(
        primary_purpose,
        trips,
        alternatives,
        tours_merged,
        model_settings,
        want_logsums,
        want_sample_table,
        size_term_matrix, skim_hotel,
        estimator,
        chunk_size, trace_hh_id,
        trace_label):

    logger.info("choose_trip_destination %s with %d trips", trace_label, trips.shape[0])

    t0 = print_elapsed_time()

    # - trip_destination_sample
    destination_sample = trip_destination_sample(
        primary_purpose=primary_purpose,
        trips=trips,
        alternatives=alternatives,
        model_settings=model_settings,
        size_term_matrix=size_term_matrix,
        skim_hotel=skim_hotel,
        estimator=estimator,
        chunk_size=chunk_size, trace_hh_id=trace_hh_id,
        trace_label=trace_label)

    dropped_trips = ~trips.index.isin(destination_sample.index.unique())
    if dropped_trips.any():
        logger.warning("%s trip_destination_sample %s trips "
                       "without viable destination alternatives" %
                       (trace_label, dropped_trips.sum()))
        trips = trips[~dropped_trips]

    t0 = print_elapsed_time("%s.trip_destination_sample" % trace_label, t0)

    if trips.empty:
        return pd.Series(index=trips.index).to_frame('choice'), None

    # - compute logsums
    destination_sample = compute_logsums(
        primary_purpose=primary_purpose,
        trips=trips,
        destination_sample=destination_sample,
        tours_merged=tours_merged,
        model_settings=model_settings,
        skim_hotel=skim_hotel,
        chunk_size=chunk_size,
        trace_label=trace_label)

    t0 = print_elapsed_time("%s.compute_logsums" % trace_label, t0)

    # - trip_destination_simulate
    destinations = trip_destination_simulate(
        primary_purpose=primary_purpose,
        trips=trips,
        destination_sample=destination_sample,
        model_settings=model_settings,
        want_logsums=want_logsums,
        size_term_matrix=size_term_matrix,
        skim_hotel=skim_hotel,
        estimator=estimator,
        chunk_size=chunk_size, trace_hh_id=trace_hh_id,
        trace_label=trace_label)

    dropped_trips = ~trips.index.isin(destinations.index)
    if dropped_trips.any():
        logger.warning("%s trip_destination_simulate %s trips "
                       "without viable destination alternatives" %
                       (trace_label, dropped_trips.sum()))

    if want_sample_table:
        # FIXME - sample_table
        destination_sample.set_index(model_settings['ALT_DEST_COL_NAME'], append=True, inplace=True)
    else:
        destination_sample = None

    t0 = print_elapsed_time("%s.trip_destination_simulate" % trace_label, t0)

    return destinations, destination_sample


class SkimHotel(object):

    def __init__(self, model_settings, network_los, trace_label):

        self.model_settings = model_settings
        self.trace_label = tracing.extend_trace_label(trace_label, 'skim_hotel')

        self.network_los = network_los
        self.zone_system = network_los.zone_system

    def sample_skims(self, presample):

        o = self.model_settings['TRIP_ORIGIN']
        d = self.model_settings['ALT_DEST_COL_NAME']
        p = self.model_settings['PRIMARY_DEST']

        if presample:
            assert not (self.zone_system == los.ONE_ZONE)
            skim_dict = self.network_los.get_skim_dict('taz')
        else:
            skim_dict = self.network_los.get_default_skim_dict()

        skims = {
            "od_skims": skim_dict.wrap(o, d),
            "dp_skims": skim_dict.wrap(d, p),

            "odt_skims": skim_dict.wrap_3d(orig_key=o, dest_key=d, dim3_key='trip_period'),
            "dot_skims": skim_dict.wrap_3d(orig_key=d, dest_key=o, dim3_key='trip_period'),
            "dpt_skims": skim_dict.wrap_3d(orig_key=d, dest_key=p, dim3_key='trip_period'),
            "pdt_skims": skim_dict.wrap_3d(orig_key=p, dest_key=d, dim3_key='trip_period'),
        }

        return skims

    def logsum_skims(self):

        o = self.model_settings['TRIP_ORIGIN']
        d = self.model_settings['ALT_DEST_COL_NAME']
        p = self.model_settings['PRIMARY_DEST']
        skim_dict = self.network_los.get_default_skim_dict()

        skims = {
            "odt_skims": skim_dict.wrap_3d(orig_key=o, dest_key=d, dim3_key='trip_period'),
            "dot_skims": skim_dict.wrap_3d(orig_key=d, dest_key=o, dim3_key='trip_period'),
            "dpt_skims": skim_dict.wrap_3d(orig_key=d, dest_key=p, dim3_key='trip_period'),
            "pdt_skims": skim_dict.wrap_3d(orig_key=p, dest_key=d, dim3_key='trip_period'),
            "od_skims": skim_dict.wrap(o, d),
            "dp_skims": skim_dict.wrap(d, p),
        }

        if self.zone_system == los.THREE_ZONE:
            # fixme - is this a lightweight object?
            tvpb = self.network_los.tvpb

            tvpb_logsum_odt = tvpb.wrap_logsum(orig_key=o, dest_key=d,
                                               tod_key='trip_period', segment_key='demographic_segment',
                                               trace_label=self.trace_label, tag='tvpb_logsum_odt')
            tvpb_logsum_dot = tvpb.wrap_logsum(orig_key=d, dest_key=o,
                                               tod_key='trip_period', segment_key='demographic_segment',
                                               trace_label=self.trace_label, tag='tvpb_logsum_dot')
            tvpb_logsum_dpt = tvpb.wrap_logsum(orig_key=d, dest_key=p,
                                               tod_key='trip_period', segment_key='demographic_segment',
                                               trace_label=self.trace_label, tag='tvpb_logsum_dpt')
            tvpb_logsum_pdt = tvpb.wrap_logsum(orig_key=p, dest_key=d,
                                               tod_key='trip_period', segment_key='demographic_segment',
                                               trace_label=self.trace_label, tag='tvpb_logsum_pdt')

            skims.update({
                'tvpb_logsum_odt': tvpb_logsum_odt,
                'tvpb_logsum_dot': tvpb_logsum_dot,
                'tvpb_logsum_dpt': tvpb_logsum_dpt,
                'tvpb_logsum_pdt': tvpb_logsum_pdt
            })

        return skims


def run_trip_destination(
        trips,
        tours_merged,
        estimator,
        chunk_size, trace_hh_id,
        trace_label,
        fail_some_trips_for_testing=False):
    """
    trip destination - main functionality separated from model step so it can be called iteratively

    Run the trip_destination model, assigning destinations for each (intermediate) trip
    (last trips already have a destination - either the tour primary destination or Home)

    Set trip destination and origin columns, and a boolean failed flag for any failed trips
    (destination for flagged failed trips will be set to -1)

    Parameters
    ----------
    trips
    tours_merged
    want_sample_table
    chunk_size
    trace_hh_id
    trace_label

    Returns
    -------

    """

    model_settings_file_name = 'trip_destination.yaml'
    model_settings = config.read_model_settings(model_settings_file_name)
    preprocessor_settings = model_settings.get('preprocessor', None)
    logsum_settings = config.read_model_settings(model_settings['LOGSUM_SETTINGS'])

    logsum_column_name = model_settings.get('DEST_CHOICE_LOGSUM_COLUMN_NAME')
    want_logsums = logsum_column_name is not None

    sample_table_name = model_settings.get('DEST_CHOICE_SAMPLE_TABLE_NAME')
    want_sample_table = config.setting('want_dest_choice_sample_tables') and sample_table_name is not None

    land_use = inject.get_table('land_use')
    size_terms = inject.get_injectable('size_terms')
    network_los = inject.get_injectable('network_los')

    trips = trips.sort_index()
    trips['next_trip_id'] = np.roll(trips.index, -1)
    trips.next_trip_id = trips.next_trip_id.where(trips.trip_num < trips.trip_count, 0)

    # - initialize trip origin and destination to those of half-tour
    # (we will sequentially adjust intermediate trips origin and destination as we choose them)
    tour_destination = reindex(tours_merged.destination, trips.tour_id).astype(np.int64)
    tour_origin = reindex(tours_merged.origin, trips.tour_id).astype(np.int64)
    trips['destination'] = np.where(trips.outbound, tour_destination, tour_origin)
    trips['origin'] = np.where(trips.outbound, tour_origin, tour_destination)
    trips['failed'] = False

    if estimator:
        # need to check or override non-intermediate trip destination
        # should check consistency of survey trips origin, destination with parent tour and subsequent/prior trip?
        # FIXME if not consistent, do we fail or override? (seems weird to override them to bad values?)

        # expect all the same trips
        survey_trips = estimator.get_survey_table('trips').sort_index()
        assert survey_trips.index.equals(trips.index)

        first = (survey_trips.trip_num == 1)
        last = (survey_trips.trip_num == trips.trip_count)

        # expect survey's outbound first trip origin to be same as half tour origin
        assert (survey_trips.origin[survey_trips.outbound & first]
                == tour_origin[survey_trips.outbound & first]).all()
        # expect outbound last trip destination to be same as half tour destination
        assert (survey_trips.destination[survey_trips.outbound & last]
                == tour_destination[survey_trips.outbound & last]).all()

        # expect inbound first trip origin to be same as half tour destination
        assert (survey_trips.origin[~survey_trips.outbound & first]
                == tour_destination[~survey_trips.outbound & first]).all()
        # expect inbound last trip destination to be same as half tour origin
        assert (survey_trips.destination[~survey_trips.outbound & last]
                == tour_origin[~survey_trips.outbound & last]).all()

    # - filter tours_merged (AFTER copying destination and origin columns to trips)
    # tours_merged is used for logsums, we filter it here upfront to save space and time
    tours_merged_cols = logsum_settings['TOURS_MERGED_CHOOSER_COLUMNS']
    redundant_cols = model_settings.get('REDUNDANT_TOURS_MERGED_CHOOSER_COLUMNS', [])
    if redundant_cols:
        tours_merged_cols = [c for c in tours_merged_cols if c not in redundant_cols]

    tours_merged = tours_merged[tours_merged_cols]

    # - skims
    skim_hotel = SkimHotel(model_settings, network_los, trace_label)

    # - size_terms and alternatives
    alternatives = tour_destination_size_terms(land_use, size_terms, 'trip')

    # DataFrameMatrix alows us to treat dataframe as virtual a 2-D array, indexed by zone_id, purpose
    # e.g. size_terms.get(df.dest_zone_id, df.purpose)
    # returns a series of size_terms for each chooser's dest_zone_id and purpose with chooser index
    size_term_matrix = DataFrameMatrix(alternatives)

    # don't need size terms in alternatives, just zone_id index
    alternatives = alternatives.drop(alternatives.columns, axis=1)
    alternatives.index.name = model_settings['ALT_DEST_COL_NAME']

    sample_list = []

    # - process intermediate trips in ascending trip_num order
    intermediate = trips.trip_num < trips.trip_count
    if intermediate.any():

        first_trip_num = trips[intermediate].trip_num.min()
        last_trip_num = trips[intermediate].trip_num.max()

        # iterate over trips in ascending trip_num order
        for trip_num in range(first_trip_num, last_trip_num + 1):

            nth_trips = trips[intermediate & (trips.trip_num == trip_num)]
            nth_trace_label = tracing.extend_trace_label(trace_label, 'trip_num_%s' % trip_num)

            locals_dict = {
                'network_los': network_los
            }
            locals_dict.update(config.get_model_constants(model_settings))

            # - annotate nth_trips
            if preprocessor_settings:
                expressions.assign_columns(
                    df=nth_trips,
                    model_settings=preprocessor_settings,
                    locals_dict=locals_dict,
                    trace_label=nth_trace_label)

            logger.info("Running %s with %d trips", nth_trace_label, nth_trips.shape[0])

            # - choose destination for nth_trips, segmented by primary_purpose
            choices_list = []
            for primary_purpose, trips_segment in nth_trips.groupby('primary_purpose'):
                choices, destination_sample = choose_trip_destination(
                    primary_purpose,
                    trips_segment,
                    alternatives,
                    tours_merged,
                    model_settings,
                    want_logsums,
                    want_sample_table,
                    size_term_matrix, skim_hotel,
                    estimator,
                    chunk_size, trace_hh_id,
                    trace_label=tracing.extend_trace_label(nth_trace_label, primary_purpose))

                choices_list.append(choices)
                if want_sample_table:
                    assert destination_sample is not None
                    sample_list.append(destination_sample)

            destinations_df = pd.concat(choices_list)

            if fail_some_trips_for_testing:
                if len(destinations_df) > 0:
                    destinations_df = destinations_df.drop(destinations_df.index[0])

            failed_trip_ids = nth_trips.index.difference(destinations_df.index)
            if failed_trip_ids.any():
                logger.warning("%s sidelining %s trips without viable destination alternatives" %
                               (nth_trace_label, failed_trip_ids.shape[0]))
                next_trip_ids = nth_trips.next_trip_id.reindex(failed_trip_ids)
                trips.loc[failed_trip_ids, 'failed'] = True
                trips.loc[failed_trip_ids, 'destination'] = -1
                trips.loc[next_trip_ids, 'origin'] = trips.loc[failed_trip_ids].origin.values

            if len(destinations_df) == 0:
                assert failed_trip_ids.all()
                logger.warning(f"all {len(nth_trips)} {primary_purpose} trip_num {trip_num} trips failed")

            if len(destinations_df) > 0:
                # - assign choices to this trip's destinations
                # if estimator, then the choices will already have been overridden by trip_destination_simulate
                # because we need to overwrite choices before any failed choices are suppressed
                assign_in_place(trips, destinations_df.choice.to_frame('destination'))
                if want_logsums:
                    assert 'logsum' in destinations_df.columns
                    assign_in_place(trips, destinations_df.logsum.to_frame(logsum_column_name))

                # - assign choice to next trip's origin
                destinations_df.index = nth_trips.next_trip_id.reindex(destinations_df.index)