# This file is part of beets.
# Copyright 2016
#
# Permission is hereby granted, free of charge, to any person obtaining
# a copy of this software and associated documentation files (the
# "Software"), to deal in the Software without restriction, including
# without limitation the rights to use, copy, modify, merge, publish,
# distribute, sublicense, and/or sell copies of the Software, and to
# permit persons to whom the Software is furnished to do so, subject to
# the following conditions:
#
# The above copyright notice and this permission notice shall be
# included in all copies or substantial portions of the Software.

"""Open metadata information in a text editor to let the user edit it.
"""
from __future__ import (division, absolute_import, print_function,
                        unicode_literals)

from beets import plugins
from beets import util
from beets import ui
from beets.dbcore import types
from beets.importer import action, SingletonImportTask
from beets.library import Item, Album
from beets.ui.commands import _do_query, PromptChoice
from copy import deepcopy
import subprocess
import yaml
from tempfile import NamedTemporaryFile
import os


# These "safe" types can avoid the format/parse cycle that most fields go
# through: they are safe to edit with native YAML types.
SAFE_TYPES = (types.Float, types.Integer, types.Boolean)


class ParseError(Exception):
    """The modified file is unreadable. The user should be offered a chance to
    fix the error.
    """


def edit(filename):
    """Open `filename` in a text editor.
    """
    cmd = util.shlex_split(util.editor_command())
    cmd.append(filename)
    subprocess.call(cmd)


def dump(arg):
    """Dump a sequence of dictionaries as YAML for editing.
    """
    return yaml.safe_dump_all(
        arg,
        allow_unicode=True,
        default_flow_style=False,
    )


def load(s):
    """Read a sequence of YAML documents back to a list of dictionaries
    with string keys.

    Can raise a `ParseError`.
    """
    try:
        out = []
        for d in yaml.load_all(s):
            if not isinstance(d, dict):
                raise ParseError(
                    'each entry must be a dictionary; found {}'.format(
                        type(d).__name__
                    )
                )

            # Convert all keys to strings. They started out as strings,
            # but the user may have inadvertently messed this up.
            out.append({unicode(k): v for k, v in d.items()})

    except yaml.YAMLError as e:
        raise ParseError('invalid YAML: {}'.format(e))
    return out


def _safe_value(obj, key, value):
    """Check whether the `value` is safe to represent in YAML and trust as
    returned from parsed YAML.

    This ensures that values do not change their type when the user edits their
    YAML representation.
    """
    typ = obj._type(key)
    return isinstance(typ, SAFE_TYPES) and isinstance(value, typ.model_type)


def flatten(obj, fields):
    """Represent `obj`, a `dbcore.Model` object, as a dictionary for
    serialization. Only include the given `fields` if provided;
    otherwise, include everything.

    The resulting dictionary's keys are strings and the values are
    safely YAML-serializable types.
    """
    # Format each value.
    d = {}
    for key in obj.keys():
        value = obj[key]
        if _safe_value(obj, key, value):
            # A safe value that is faithfully representable in YAML.
            d[key] = value
        else:
            # A value that should be edited as a string.
            d[key] = obj.formatted()[key]

    # Possibly filter field names.
    if fields:
        return {k: v for k, v in d.items() if k in fields}
    else:
        return d


def apply_(obj, data):
    """Set the fields of a `dbcore.Model` object according to a
    dictionary.

    This is the opposite of `flatten`. The `data` dictionary should have
    strings as values.
    """
    for key, value in data.items():
        if _safe_value(obj, key, value):
            # A safe value *stayed* represented as a safe type. Assign it
            # directly.
            obj[key] = value
        else:
            # Either the field was stringified originally or the user changed
            # it from a safe type to an unsafe one. Parse it as a string.
            obj.set_parse(key, unicode(value))


class EditPlugin(plugins.BeetsPlugin):

    def __init__(self):
        super(EditPlugin, self).__init__()

        self.config.add({
            # The default fields to edit.
            'albumfields': 'album albumartist',
            'itemfields': 'track title artist album',

            # Silently ignore any changes to these fields.
            'ignore_fields': 'id path',
        })

        self.register_listener('before_choose_candidate',
                               self.before_choose_candidate_listener)
        self.register_listener('import_begin', self.import_begin_listener)

    def _set_reference_field(self, field):
        """Set the "unequivocal, non-editable field" that will be used for
        reconciling back the user changes.
        """
        if field == 'id':
            self.reference_field = 'id'
            self.ref_field_value = lambda o: int(o.id)
            self.obj_from_ref = lambda d: int(d['id'])
        elif field == 'path':
            self.reference_field = 'path'
            self.ref_field_value = lambda o: util.displayable_path(o.path)
            self.obj_from_ref = lambda d: util.displayable_path(d['path'])

    def commands(self):
        edit_command = ui.Subcommand(
            'edit',
            help='interactively edit metadata'
        )
        edit_command.parser.add_option(
            '-f', '--field',
            metavar='FIELD',
            action='append',
            help='edit this field also',
        )
        edit_command.parser.add_option(
            '--all',
            action='store_true', dest='all',
            help='edit all fields',
        )
        edit_command.parser.add_album_option()
        edit_command.func = self._edit_command
        return [edit_command]

    def _edit_command(self, lib, opts, args):
        """The CLI command function for the `beet edit` command.
        """
        # Set the reference field to "id", as all Models have valid ids.
        self._set_reference_field('id')

        # Get the objects to edit.
        query = ui.decargs(args)
        items, albums = _do_query(lib, query, opts.album, False)
        objs = albums if opts.album else items
        if not objs:
            ui.print_('Nothing to edit.')
            return

        # Get the fields to edit.
        if opts.all:
            fields = None
        else:
            fields = self._get_fields(opts.album, opts.field)
        self.edit(opts.album, objs, fields)

    def _get_fields(self, album, extra):
        """Get the set of fields to edit.
        """
        # Start with the configured base fields.
        if album:
            fields = self.config['albumfields'].as_str_seq()
        else:
            fields = self.config['itemfields'].as_str_seq()

        # Add the requested extra fields.
        if extra:
            fields += extra

        # Ensure we always have the reference field for identification.
        fields.append(self.reference_field)

        return set(fields)

    def edit(self, album, objs, fields):
        """The core editor function.

        - `album`: A flag indicating whether we're editing Items or Albums.
        - `objs`: The `Item`s or `Album`s to edit.
        - `fields`: The set of field names to edit (or None to edit
          everything).
        """
        # Present the YAML to the user and let her change it.
        if album:
            success = self.edit_objects(objs, None, fields)
        else:
            success = self.edit_objects(objs, fields, None)

        # Save the new data.
        if success:
            self.save_changes(objs)

    def edit_objects(self, objs, item_fields, album_fields):
        """Dump a set of Model objects to a file as text, ask the user
        to edit it, and apply any changes to the objects.

        Return a boolean indicating whether the edit succeeded.
        """
        # Get the content to edit as raw data structures.
        old_data = [flatten(o,
                            item_fields if isinstance(o, Item)
                            else album_fields)
                    for o in objs]

        # Set up a temporary file with the initial data for editing.
        new = NamedTemporaryFile(suffix='.yaml', delete=False)
        old_str = dump(old_data)
        new.write(old_str)
        new.close()

        # Loop until we have parseable data and the user confirms.
        try:
            while True:
                # Ask the user to edit the data.
                edit(new.name)

                # Read the data back after editing and check whether anything
                # changed.
                with open(new.name) as f:
                    new_str = f.read()
                if new_str == old_str:
                    ui.print_("No changes; aborting.")
                    return False

                # Parse the updated data.
                try:
                    new_data = load(new_str)
                except ParseError as e:
                    ui.print_("Could not read data: {}".format(e))
                    if ui.input_yn("Edit again to fix? (Y/n)", True):
                        continue
                    else:
                        return False

                # Show the changes.
                # If the objects are not on the DB yet, we need a copy of their
                # original state for show_model_changes.
                if all(not obj.id for obj in objs):
                    objs_old = {self.ref_field_value(obj): deepcopy(obj)
                                for obj in objs}
                self.apply_data(objs, old_data, new_data)
                changed = False
                for obj in objs:
                    if not obj.id:
                        # TODO: remove uglyness
                        obj_old = objs_old[self.ref_field_value(obj)]
                    else:
                        obj_old = None
                    changed |= ui.show_model_changes(obj, obj_old)
                if not changed:
                    ui.print_('No changes to apply.')
                    return False

                # Confirm the changes.
                choice = ui.input_options(
                    ('continue Editing', 'apply', 'cancel')
                )
                if choice == 'a':  # Apply.
                    return True
                elif choice == 'c':  # Cancel.
                    return False
                elif choice == 'e':  # Keep editing.
                    # Reset the temporary changes to the objects.
                    for obj in objs:
                        obj.read()
                    continue

        # Remove the temporary file before returning.
        finally:
            os.remove(new.name)

    def apply_data(self, objs, old_data, new_data):
        """Take potentially-updated data and apply it to a set of Model
        objects.

        The objects are not written back to the database, so the changes
        are temporary.
        """
        if len(old_data) != len(new_data):
            self._log.warn('number of objects changed from {} to {}',
                           len(old_data), len(new_data))

        obj_by_ref = {self.ref_field_value(o): o for o in objs}
        ignore_fields = self.config['ignore_fields'].as_str_seq()
        for old_dict, new_dict in zip(old_data, new_data):
            # Prohibit any changes to forbidden fields to avoid
            # clobbering `id` and such by mistake.
            forbidden = False
            for key in ignore_fields:
                if old_dict.get(key) != new_dict.get(key):
                    self._log.warn('ignoring object whose {} changed', key)
                    forbidden = True
                    break
            if forbidden:
                continue

            # Reconcile back the user edits, using the reference_field.
            val = self.obj_from_ref(old_dict)
            apply_(obj_by_ref[val], new_dict)

    def save_changes(self, objs):
        """Save a list of updated Model objects to the database.
        """
        # Save to the database and possibly write tags.
        for ob in objs:
            if ob._dirty:
                self._log.debug('saving changes to {}', ob)
                ob.try_sync(ui.should_write(), ui.should_move())

    # Methods for interactive importer execution.

    def before_choose_candidate_listener(self, session, task):
        """Append an "Edit" choice to the interactive importer prompt.
        """
        choices = [PromptChoice('d', 'eDit', self.importer_edit)]
        if task.candidates:
            choices.append(PromptChoice('c', 'edit Candidates',
                                        self.importer_edit_candidate))

        return choices

    def import_begin_listener(self, session):
        """Initialize the reference field to 'path', as during an interactive
        import session Models do not have valid 'id's yet.
        """
        self._set_reference_field('path')

    def importer_edit(self, session, task):
        """Callback for invoking the functionality during an interactive
        import session on the *original* item tags.
        """
        singleton = isinstance(object, SingletonImportTask)
        item_fields = self._get_fields(False, [])
        items = list(task.items)  # Shallow copy, not modifying task.items.
        if not singleton:
            # Prepend a FakeAlbum for allowing the user to edit album fields.
            album = FakeAlbum(task.items, task.toppath)
            items.insert(0, album)
            album_fields = self._get_fields(True, [])
        else:
            album_fields = None

        # Present the YAML to the user and let her change it.
        success = self.edit_objects(items, item_fields, album_fields)

        # Save the new data.
        if success:
            if not singleton:
                # Propagate the album changes to the items.
                album._apply_changes()
            # Return action.RETAG, which makes the importer write the tags
            # to the files if needed.
            return action.RETAG
        else:
            # Edit cancelled / no edits made. Revert changes.
            for obj in task.items:
                obj.read()

    def importer_edit_candidate(self, session, task):
        """Callback for invoking the functionality during an interactive
        import session on a *candidate* applied to the original items.
        """
        # Prompt the user for a candidate, and simulate matching.
        sel = ui.input_options([], numrange=(1, len(task.candidates)))
        # Force applying the candidate on the items.
        task.match = task.candidates[sel - 1]
        task.apply_metadata()

        return self.importer_edit(session, task)


class FakeAlbum(Album):
    """Helper for presenting the user with an Album to be edited when there
    is no real Album present. The album fields are set from the first item,
    and after editing propagated to the items on `_apply_changes`.
    """
    def __init__(self, items, path):
        self._src_items = items

        # Create the album structure using metadata from the first item.
        values = dict((key, items[0][key]) for key in Album.item_keys)
        # Manually set the path as a single value field.
        values[u'path'] = util.displayable_path(path)
        super(FakeAlbum, self).__init__(**values)

    def _getters(self):
        """Remove 'path' from Album._getters(), treating it as a regular field
        in order to be able to use it directly."""
        getters = Album._getters()
        getters.pop('path')
        return getters

    def _apply_changes(self):
        """Propagate changes to the album fields onto the Items.
        """
        values = dict((key, self[key]) for key in Album.item_keys)
        for i in self._src_items:
            i.update(values)