#!/usr/bin/env python
# -*- coding: utf-8 -*-
# Copyright (c) 2020 Satpy developers
#
# This file is part of satpy.
#
# satpy is free software: you can redistribute it and/or modify it under the
# terms of the GNU General Public License as published by the Free Software
# Foundation, either version 3 of the License, or (at your option) any later
# version.
#
# satpy is distributed in the hope that it will be useful, but WITHOUT ANY
# WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
# A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License along with
# satpy.  If not, see <http://www.gnu.org/licenses/>.
"""Implementation of a dependency tree."""

import numpy as np

from satpy.dataset import create_filtered_query, ModifierTuple
from satpy.dataset.data_dict import TooManyResults, get_key
from satpy.node import CompositorNode, Node, EMPTY_LEAF_NAME, MissingDependencies, LOG, ReaderNode


class Tree:
    """A tree implementation."""

    # simplify future logic by only having one "sentinel" empty node
    # making it a class attribute ensures it is the same across instances
    empty_node = Node(EMPTY_LEAF_NAME)

    def __init__(self):
        """Set up the tree."""
        self._root = Node(None)

        # keep a flat dictionary of nodes contained in the tree for better
        # __contains__
        self._all_nodes = _DataIDContainer()

    def leaves(self, nodes=None, unique=True):
        """Get the leaves of the tree starting at the root.

        Args:
            nodes (iterable): limit leaves for these node names
            unique: only include individual leaf nodes once

        Returns:
            list of leaf nodes

        """
        if nodes is None:
            return self._root.leaves(unique=unique)

        res = list()
        for child_id in nodes:
            for sub_child in self._all_nodes[child_id].leaves(unique=unique):
                if not unique or sub_child not in res:
                    res.append(sub_child)
        return res

    def trunk(self, nodes=None, unique=True):
        """Get the trunk nodes of the tree starting at this root.

        Args:
            nodes (iterable): limit trunk nodes to the names specified or the
                              children of them that are also trunk nodes.
            unique: only include individual trunk nodes once

        Returns:
            list of trunk nodes

        """
        if nodes is None:
            return self._root.trunk(unique=unique)

        res = list()
        for child_id in nodes:
            for sub_child in self._all_nodes[child_id].trunk(unique=unique):
                if not unique or sub_child not in res:
                    res.append(sub_child)
        return res

    def add_child(self, parent, child):
        """Add a child to the tree."""
        Node.add_child(parent, child)
        # Sanity check: Node objects should be unique. They can be added
        #               multiple times if more than one Node depends on them
        #               but they should all map to the same Node object.
        if self.contains(child.name):
            assert self._all_nodes[child.name] is child
        if child is self.empty_node:
            # No need to store "empty" nodes
            return
        self._all_nodes[child.name] = child

    def add_leaf(self, ds_id, parent=None):
        """Add a leaf to the tree."""
        if parent is None:
            parent = self._root
        try:
            node = self[ds_id]
        except KeyError:
            node = Node(ds_id)
        self.add_child(parent, node)
        return node

    def __contains__(self, item):
        """Check if a item is in the tree."""
        return item in self._all_nodes

    def __getitem__(self, item):
        """Get an item of the tree."""
        return self._all_nodes[item]

    def contains(self, item):
        """Check contains when we know the *exact* DataID or DataQuery."""
        return super(_DataIDContainer, self._all_nodes).__contains__(item)

    def getitem(self, item):
        """Get Node when we know the *exact* DataID or DataQuery."""
        return super(_DataIDContainer, self._all_nodes).__getitem__(item)

    def __str__(self):
        """Render the dependency tree as a string."""
        return self._root.display()


class DependencyTree(Tree):
    """Structure to discover and store `Dataset` dependencies.

    Used primarily by the `Scene` object to organize dependency finding.
    Dependencies are stored used a series of `Node` objects which this
    class is a subclass of.

    """

    def __init__(self, readers, compositors, modifiers, available_only=False):
        """Collect Dataset generating information.

        Collect the objects that generate and have information about Datasets
        including objects that may depend on certain Datasets being generated.
        This includes readers, compositors, and modifiers.

        Composites and modifiers are defined per-sensor. If multiple sensors
        are available, compositors and modifiers are searched for in
        sensor alphabetical order.

        Args:
            readers (dict): Reader name -> Reader Object
            compositors (dict): Sensor name -> Composite ID -> Composite Object
            modifiers (dict): Sensor name -> Modifier name -> (Modifier Class, modifier options)
            available_only (bool): Whether only reader's available/loadable
                datasets should be used when searching for dependencies (True)
                or use all known/configured datasets regardless of whether the
                necessary files were provided to the reader (False).
                Note that when ``False`` loadable variations of a dataset will
                have priority over other known variations.
                Default is ``False``.

        """
        super().__init__()
        self.readers = readers
        self.compositors = compositors
        self.modifiers = modifiers
        self._available_only = available_only

    def copy(self):
        """Copy this node tree.

        Note all references to readers are removed. This is meant to avoid
        tree copies accessing readers that would return incompatible (Area)
        data. Theoretically it should be possible for tree copies to request
        compositor or modifier information as long as they don't depend on
        any datasets not already existing in the dependency tree.
        """
        new_tree = DependencyTree({}, self.compositors, self.modifiers)
        for c in self._root.children:
            c = c.copy(node_cache=new_tree._all_nodes)
            new_tree.add_child(new_tree._root, c)
        return new_tree

    def populate_with_keys(self, dataset_keys: set, query=None):
        """Populate the dependency tree.

        Args:
            dataset_keys (set): Strings, DataIDs, DataQuerys to find dependencies for
            query (DataQuery): Additional filter parameters. See
                              `satpy.readers.get_key` for more details.

        Returns:
            (Node, set): Root node of the dependency tree and a set of unknown datasets

        """
        unknown_datasets = list()
        known_nodes = list()
        for key in dataset_keys.copy():
            try:
                dsq = create_filtered_query(key, query)
                node = self._create_subtree_for_key(dsq, query)
            except MissingDependencies as unknown:
                unknown_datasets.append(unknown.missing_dependencies)
            else:
                known_nodes.append(node)
                self.add_child(self._root, node)

        for key in dataset_keys.copy():
            dataset_keys.discard(key)
        for node in known_nodes:
            dataset_keys.add(node.name)
        if unknown_datasets:
            raise MissingDependencies(unknown_datasets, "Unknown datasets:")

    def _create_subtree_for_key(self, dataset_key, query=None):
        """Find the dependencies for *dataset_key*.

        Args:
            dataset_key (str, float, DataID, DataQuery): Dataset identifier to locate
                                                         and find any additional
                                                         dependencies for.
            query (DataQuery): Additional filter parameters. See
                               `satpy.readers.get_key` for more details.

        """
        # 0 check if the *exact* dataset is already loaded
        try:
            node = self._get_subtree_for_existing_key(dataset_key)
        except MissingDependencies:
            # exact dataset isn't loaded, let's load it below
            pass
        else:
            return node

        # 1 try to get *best* dataset from reader
        try:
            node = self._create_subtree_from_reader(dataset_key, query)
        except TooManyResults:
            LOG.warning("Too many possible datasets to load for {}".format(dataset_key))
            raise MissingDependencies({dataset_key})
        except MissingDependencies:
            pass
        else:
            return node

        # 2 try to find a composite by name (any version of it is good enough)
        try:
            node = self._get_subtree_for_existing_name(dataset_key)
        except MissingDependencies:
            pass
        else:
            return node

        # 3 try to find a composite that matches
        try:
            node = self._create_subtree_from_compositors(dataset_key, query)
        except MissingDependencies:
            raise
        else:
            return node

    def _get_subtree_for_existing_key(self, dsq):
        try:
            node = self.getitem(dsq)
            LOG.trace("Found exact dataset already loaded: {}".format(node.name))
            return node
        except KeyError:
            LOG.trace("Exact dataset {} isn't loaded, will try reader...".format(dsq))
            raise MissingDependencies({dsq})

    def _create_subtree_from_reader(self, dataset_key, query):
        try:
            node = self._find_reader_node(dataset_key, query)
        except MissingDependencies:
            LOG.trace("Could not find dataset in reader: {}".format(dataset_key))
            raise
        else:
            LOG.trace("Found reader provided dataset:\n\tRequested: {}\n\tFound: {}".format(dataset_key, node.name))
            return node

    def _find_reader_node(self, dataset_key, query):
        """Attempt to find a `DataID` in the available readers.

        Args:
            dataset_key (str, float, DataID, DataQuery):
                Dataset name, wavelength, `DataID` or `DataQuery`
                to use in searching for the dataset from the
                available readers.

        """
        matching_ids = self._find_matching_ids_in_readers(dataset_key)
        unique_id = self._get_unique_matching_id(matching_ids, dataset_key, query)

        for reader_name, ids in matching_ids.items():
            if unique_id in ids:
                return self._get_unique_reader_node_from_id(unique_id, reader_name)

        raise RuntimeError("Data ID disappeared.")

    def _find_matching_ids_in_readers(self, dataset_key):
        matching_ids = {}
        for reader_name, reader_instance in self.readers.items():
            matching_ids[reader_name] = []
            try:
                ds_ids = reader_instance.get_dataset_key(dataset_key, available_only=self._available_only,
                                                         num_results=0, best=False)
            except KeyError:
                LOG.trace("Can't find dataset %s in reader %s", str(dataset_key), reader_name)
                continue
            matching_ids[reader_name].extend(ds_ids)
        return matching_ids

    def _get_unique_matching_id(self, matching_ids, dataset_key, query):
        """Get unique matching id from `matching_ids`, for a given `dataset_key` and some optional `query`."""
        all_ids = sum(matching_ids.values(), [])
        if len(all_ids) == 0:
            raise MissingDependencies({dataset_key})
        elif len(all_ids) == 1:
            result = all_ids[0]
        else:
            sorted_ids, distances = dataset_key.sort_dataids_with_preference(all_ids, query)
            try:
                result = self._get_unique_id_from_sorted_ids(sorted_ids, distances)
            except TooManyResults:
                LOG.trace("Too many datasets matching key {} in readers {}".format(dataset_key, matching_ids.keys()))
                raise TooManyResults("Too many keys matching: {}".format(dataset_key))
            except MissingDependencies:
                raise MissingDependencies({dataset_key})
        return result

    @staticmethod
    def _get_unique_id_from_sorted_ids(sorted_ids, distances):
        if distances[0] != np.inf:
            if distances[0] != distances[1]:
                result = sorted_ids[0]
            else:
                raise TooManyResults
        else:
            raise MissingDependencies
        return result

    def _get_unique_reader_node_from_id(self, data_id, reader_name):
        try:
            # now that we know we have the exact DataID see if we have already created a Node for it
            return self.getitem(data_id)
        except KeyError:
            # we haven't created a node yet, create it now
            return ReaderNode(data_id, reader_name)

    def _get_subtree_for_existing_name(self, dsq):
        try:
            # assume that there is no such thing as a "better" composite
            # version so if we find any DataIDs already loaded then
            # we want to use them
            node = self[dsq]
            LOG.trace("Composite already loaded:\n\tRequested: {}\n\tFound: {}".format(dsq, node.name))
            return node
        except KeyError:
            # composite hasn't been loaded yet, let's load it below
            LOG.trace("Composite hasn't been loaded yet, will load: {}".format(dsq))
            raise MissingDependencies({dsq})

    def _create_subtree_from_compositors(self, dataset_key, query):
        try:
            node = self._find_compositor(dataset_key, query)
            LOG.trace("Found composite:\n\tRequested: {}\n\tFound: {}".format(dataset_key, node and node.name))
        except KeyError:
            LOG.trace("Composite not found: {}".format(dataset_key))
            raise MissingDependencies({dataset_key})
        return node

    def _find_compositor(self, dataset_key, query):
        """Find the compositor object for the given dataset_key."""
        # NOTE: This function can not find a modifier that performs
        # one or more modifications if it has modifiers see if we can find
        # the unmodified version first

        if dataset_key.is_modified():
            implicit_dependency_node = self._create_implicit_dependency_subtree(dataset_key, query)
            dataset_key = self._promote_query_to_modified_dataid(dataset_key, implicit_dependency_node.name)
            try:
                compositor = self.get_modifier(dataset_key)
            except KeyError:
                raise KeyError("Can't find anything called {}".format(str(dataset_key)))
            compositor.attrs['prerequisites'] = [implicit_dependency_node] + list(compositor.attrs['prerequisites'])
        else:
            try:
                compositor = self.get_compositor(dataset_key)
            except KeyError:
                raise KeyError("Can't find anything called {}".format(str(dataset_key)))

        root = CompositorNode(compositor)
        composite_id = root.name

        prerequisite_filter = composite_id.create_filter_query_without_required_fields(dataset_key)

        # Get the prerequisites
        LOG.trace("Looking for composite prerequisites for: {}".format(dataset_key))
        prereqs = [create_filtered_query(prereq, prerequisite_filter) if not isinstance(prereq, Node) else prereq
                   for prereq in compositor.attrs['prerequisites']]
        prereqs = self._create_required_subtrees(root, prereqs, query=query)
        root.add_required_nodes(prereqs)

        # Get the optionals
        LOG.trace("Looking for optional prerequisites for: {}".format(dataset_key))
        optionals = [create_filtered_query(prereq, prerequisite_filter) if not isinstance(prereq, Node) else prereq
                     for prereq in compositor.attrs['optional_prerequisites']]
        optionals = self._create_optional_subtrees(root, optionals, query=query)
        root.add_optional_nodes(optionals)

        return root

    def _create_implicit_dependency_subtree(self, dataset_key, query):
        new_prereq = dataset_key.create_less_modified_query()
        src_node = self._create_subtree_for_key(new_prereq, query)
        return src_node

    def _promote_query_to_modified_dataid(self, query, dep_key):
        """Promote a query to an id based on the dataset it will modify (dep).

        Typical use case is requesting a modified dataset (query). This
        modified dataset most likely depends on a less-modified
        dataset (dep_key). The less-modified dataset must come from a reader
        (at least for now) or will eventually depend on a reader dataset.
        The original request key may be limited like
        (wavelength=0.67, modifiers=('a', 'b')) while the reader-based key
        should have all of its properties specified. This method updates the
        original request key so it is fully specified and should reduce the
        chance of Node's not being unique.

        """
        orig_dict = query._asdict()
        dep_dict = dep_key._asdict()
        for key, dep_val in dep_dict.items():
            # don't change the modifiers, just cast them to the right class
            if isinstance(dep_val, ModifierTuple):
                orig_dict[key] = dep_val.__class__(orig_dict[key])
            else:
                orig_dict[key] = dep_val
        return dep_key.from_dict(orig_dict)

    def get_compositor(self, key):
        """Get a compositor."""
        for sensor_name in sorted(self.compositors):
            try:
                return self.compositors[sensor_name][key]
            except KeyError:
                continue

        raise KeyError("Could not find compositor '{}'".format(key))

    def get_modifier(self, comp_id):
        """Get a modifer."""
        # create a DataID for the compositor we are generating
        modifier = comp_id['modifiers'][-1]
        for sensor_name in sorted(self.modifiers):
            modifiers = self.modifiers[sensor_name]
            compositors = self.compositors[sensor_name]
            if modifier not in modifiers:
                continue

            mloader, moptions = modifiers[modifier]
            moptions = moptions.copy()
            moptions.update(comp_id.to_dict())
            moptions['sensor'] = sensor_name
            compositors[comp_id] = mloader(_satpy_id=comp_id, **moptions)
            return compositors[comp_id]

        raise KeyError("Could not find modifier '{}'".format(modifier))

    def _create_required_subtrees(self, parent, prereqs, query=None):
        """Determine required prerequisite Nodes for a composite.

        Args:
            parent (Node): Compositor node to add these prerequisites under
            prereqs (sequence): Strings (names), floats (wavelengths),
                                DataQuerys or Nodes to analyze.

        """
        prereq_nodes, unknown_datasets = self._create_prerequisite_subtrees(parent, prereqs, query)
        if unknown_datasets:
            raise MissingDependencies(unknown_datasets)
        return prereq_nodes

    def _create_optional_subtrees(self, parent, prereqs, query=None):
        """Determine optional prerequisite Nodes for a composite.

        Args:
            parent (Node): Compositor node to add these prerequisites under
            prereqs (sequence): Strings (names), floats (wavelengths), or
                                DataQuerys to analyze.

        """
        prereq_nodes, unknown_datasets = self._create_prerequisite_subtrees(parent, prereqs, query)

        for prereq, unknowns in unknown_datasets.items():
            u_str = ", ".join([str(x) for x in unknowns])
            LOG.debug('Skipping optional %s: Unknown dataset %s',
                      str(prereq), u_str)

        return prereq_nodes

    def _create_prerequisite_subtrees(self, parent, prereqs, query=None):
        """Determine prerequisite Nodes for a composite.

        Args:
            parent (Node): Compositor node to add these prerequisites under
            prereqs (sequence): Strings (names), floats (wavelengths),
                                DataQuerys or Nodes to analyze.

        """
        prereq_nodes = []
        unknown_datasets = dict()
        if not prereqs:
            # this composite has no required prerequisites
            prereq_nodes.append(self.empty_node)
            self.add_child(parent, self.empty_node)
            return prereq_nodes, unknown_datasets

        for prereq in prereqs:
            try:
                if isinstance(prereq, Node):
                    node = prereq
                else:
                    node = self._create_subtree_for_key(prereq, query=query)
            except MissingDependencies as unknown:
                unknown_datasets[prereq] = unknown.missing_dependencies

            else:
                prereq_nodes.append(node)
                self.add_child(parent, node)

        return prereq_nodes, unknown_datasets


class _DataIDContainer(dict):
    """Special dictionary object that can handle dict operations based on dataset name, wavelength, or DataID.

    Note: Internal dictionary keys are `DataID` objects.

    """

    def keys(self):
        """Give currently contained keys."""
        # sort keys so things are a little more deterministic (.keys() is not)
        return sorted(super(_DataIDContainer, self).keys())

    def get_key(self, match_key):
        """Get multiple fully-specified keys that match the provided query.

        Args:
            match_key (DataID): DataID or DataQuery of query parameters to use for
                                searching. Can also be a string representing the
                                dataset name or a number representing the dataset
                                wavelength.

        """
        return get_key(match_key, self.keys())

    def __getitem__(self, item):
        """Get item from container."""
        try:
            # short circuit - try to get the object without more work
            return super(_DataIDContainer, self).__getitem__(item)
        except KeyError:
            key = self.get_key(item)
            return super(_DataIDContainer, self).__getitem__(key)

    def __contains__(self, item):
        """Check if item exists in container."""
        try:
            key = self.get_key(item)
        except KeyError:
            return False
        return super(_DataIDContainer, self).__contains__(key)
