File: blends.py

package info (click to toggle)
blends 0.7.2
  • links: PTS, VCS
  • area: main
  • in suites: bullseye, buster, sid
  • size: 792 kB
  • sloc: xml: 5,097; python: 1,003; sh: 705; makefile: 272
file content (815 lines) | stat: -rw-r--r-- 26,827 bytes parent folder | download
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
'''A module to handle Debian Pure Blends tasks, modelled after apt.package.

The examples use the following sample tasks file:

>>> sample_task = """Format: https://blends.debian.org/blends/1.1
... Task: Education
... Install: true
... Description: Educational astronomy applications
...  Various applications that can be used to teach astronomy.
...  .
...  This is however incomplete.
...
... Recommends: celestia-gnome | celestia-glut, starplot
...
... Recommends: gravit
... WNPP: 743379
... Homepage: http://gravit.slowchop.com/
... Pkg-Description: Visually stunning gravity simulator
...  Gravit is a free, visually stunning gravity simulator.
...  .
...  You can spend endless time experimenting with various
...  configurations of simulated universes.
... Why: Useful package
... Remark: Entered Debian in 2014
...
... Suggests: sunclock, xtide
... """
>>> with open('education', 'w') as fp:
...     nbytes = fp.write(sample_task)
'''
import io
import os
import itertools
import re
import shutil
from debian.deb822 import Deb822


class Blend:
    '''Representation of a Debian Pure Blend.
    '''
    def __init__(self, basedir='.'):
        with open(os.path.join(basedir, 'debian', 'control.stub'),
                  encoding="UTF-8") as fp:
            self.control_stub = Deb822List(Deb822.iter_paragraphs(fp))

        self.name = self.control_stub[0]['Source']
        '''Full (package) name of the blend (``debian-astro``)'''

        self.short_name = self.name.split('-', 1)[-1]
        '''Short name of the blend (``astro``)'''

        self.title = 'Debian ' + self.short_name.capitalize()
        '''Blends title (``Debian Astro``)'''

        base_deps = ["${misc:Depends}"]

        self.prefix = self.short_name
        '''Prefix for tasks (``astro``)'''

        for pkg in self.control_stub[1:]:
            p = pkg['Package'].split('-', 1)
            if len(p) > 1 and p[1] == 'tasks':
                self.prefix = p[0]
                base_deps.append("{Package} (= ${{source:Version}})"
                                 .format(**pkg))
                break

        try:
            with open(os.path.join(basedir, 'config', 'control'),
                      encoding="UTF-8") as fp:
                self.control_stub.append(Deb822(fp))
                base_deps.append("{}-config (= ${{source:Version}})"
                                 .format(self.prefix))
        except IOError:
            pass

        self.tasks = []
        '''``Task`` list'''
        for name in sorted(filter(lambda n: n[-1] != '~',
                                  os.listdir(os.path.join(basedir, 'tasks')))):
            with open(os.path.join(basedir, 'tasks', name),
                      encoding="UTF-8") as fp:
                task = Task(self, name, fp, base_deps=base_deps)
            self.tasks.append(task)

    def update(self, cache):
        '''Update from cache

        :param cache: ``apt.Cache`` like object

        This adds the available versions to all dependencies. It
        updates descriptions, summaries etc. available to all
        BaseDependencies in all tasks.

        Instead of using ``update()``, also the ``+=`` operator can be used.

        '''
        for task in self.tasks:
            task += cache

    def __iadd__(self, cache):
        self.update(cache)
        return self

    @property
    def all(self):
        '''All Base Dependencies of this task
        '''
        return list(itertools.chain(*(t.all for t in self.tasks)))

    def fix_dependencies(self):
        '''Fix the dependencies according to available packages

        This lowers all unavailable ``recommended`` dependencies to
        ``suggested``.
        '''
        missing = []
        for task in self.tasks:
            missing += task.fix_dependencies()
        return missing

    def gen_control(self):
        '''Return the task as list of ``Deb822`` objects suitable for
        ``debian/control``
        '''
        tasks = list(filter(lambda task: task.is_metapackage, self.tasks))

        # Create the special 'all' task recommending all tasks that
        # shall be installed by default
        all_task = Task(
            self, "all",
            '''Description: Default selection of tasks for {task.title}
 This package is part of the {task.title} Pure Blend and installs all
 tasks for a default installation of this blend.'''.format(task=self),
            base_deps=['${misc:Depends}'])
        for task in tasks:
            if task.install:
                all_task.recommends.append(Dependency("Recommends",
                                                      task.package_name))
            else:
                all_task.suggests.append(Dependency("Suggests",
                                                    task.package_name))
        if len(all_task.recommends) > 0:
            tasks.insert(0, all_task)

        return Deb822List(self.control_stub
                          + [task.gen_control() for task in tasks])

    def gen_task_desc(self, udeb=False):
        '''Return the task as list of ``Deb822`` objects suitable for
        ``blends-task.desc``
        '''
        tasks = list(filter(lambda task: task.is_metapackage and task.is_leaf,
                            self.tasks))

        header = [Deb822({
            'Task': self.name,
            'Relevance':  '7',
            'Section': self.name,
            'Description': '{} Pure Blend\n .'.format(self.title),
        })] if not udeb else []
        return Deb822List(header + [task.gen_task_desc(udeb)
                                    for task in tasks])


class Task:
    '''Representation of a Blends task. Modelled after apt.package.Version.

    The Version class contains all information related to a
    specific package version of a blends task.

    :param blend: ``Blend`` object, or Blend name

    :param name: Name of the task

    :param sequence: ``str`` or ``file`` containing the ``Deb822``
                     description of the task

    :param base_deps: List of dependencies to add to the task (``str``)

    When the header does not contain a line

    ``Format: https://blends.debian.org/blends/1.1``

    then the ``Depends`` priorities will be lowered to ``Recommends``
    when read.

    Example:

    >>> with open('education') as fp:
    ...     task = Task('debian-astro', 'education', fp)
    >>> print(task.name)
    education
    >>> print(task.package_name)
    astro-education
    >>> print(task.description)
    Various applications that can be used to teach astronomy.
    <BLANKLINE>
    This is however incomplete.
    >>> print(task.summary)
    Educational astronomy applications
    >>> print(task.section)
    metapackages
    >>> print(task.architecture)
    all
    >>> for p in task.all:
    ...     print(p.name)
    celestia-gnome
    celestia-glut
    starplot
    gravit
    sunclock
    xtide

    '''
    def __init__(self, blend, name, sequence, base_deps=None):
        if isinstance(blend, str):
            self.blend = blend
            '''Blend name'''

            self.prefix = blend[len('debian-'):] \
                if blend.startswith('debian-') else blend
            '''Metapackage prefix'''
        else:
            self.blend = blend.name
            self.prefix = blend.prefix

        self.name = name
        '''Task name'''

        self.content = Deb822List(Deb822.iter_paragraphs(sequence))
        '''Deb822List content of the task'''

        self.header = self.content[0]
        '''Deb822 header'''

        self.base_deps = base_deps or []
        '''Base dependencies'''

        # Check for the format version, and upgrade if not actual
        self.format_upgraded = False
        '''``True`` if the format was upgraded from an older version'''

        if 'Format' in self.header:
            self.format_version = self.header['Format'].strip() \
                .rsplit('/', 1)[-1]
        else:
            self.format_version = '1'
        if self.format_version.split('.') < ['1', '1']:
            self.content = Task.upgrade_from_1_0(self.content)
            self.format_upgraded = True

        # Create package dependencies
        dep_types = ["Depends", "Recommends", "Suggests"]
        dep_attrs = ["dependencies", "recommends", "suggests"]
        for dep_type, dep_attr in zip(dep_types, dep_attrs):
            setattr(self, dep_attr, list(itertools.chain(
                *(list(Dependency(dep_type, s.strip(), par)
                       for s in par.get(dep_type, '').split(",") if s)
                  for par in self.content[1:]))))
        self.enhances = [
            Dependency('Enhances', s.strip(), self.header)
            for s in self.header.get('Enhances', '').split(",") if s
        ]

    @property
    def install(self):
        '''``True`` if the task is installed as a default package
        '''
        return self.header.get("Install") == "true"

    @property
    def index(self):
        '''``True`` if the task shall appear in the tasks index in the
        web senitel
        '''
        return self.header.get("index", "true") == "true"

    @property
    def is_leaf(self):
        return self.header.get("leaf", "true") == "true"

    @property
    def is_metapackage(self):
        '''``True`` if the tasks has a Debian metapackage
        '''
        return self.header.get("metapackage", "true") == "true"

    @property
    def package_name(self):
        return '{task.prefix}-{task.name}'.format(task=self)

    @property
    def description(self):
        '''Return the formatted long description.
        '''
        desc = self.header.get("Pkg-Description",
                               self.header.get("Description"))
        if not desc:
            return None
        else:
            return "\n".join(line[1:] if line != ' .' else ''
                             for line in desc.split("\n")[1:])

    @property
    def summary(self):
        '''Return the short description (one line summary).
        '''
        desc = self.header.get("Pkg-Description",
                               self.header.get("Description"))
        return desc.split('\n')[0] if desc else None

    @property
    def section(self):
        '''Return the section of the package.
        '''
        return 'metapackages'

    @property
    def architecture(self):
        '''Return the architecture of the package version.
        '''
        return self.header.get('Architecture', 'all')

    @property
    def tests(self):
        '''Return all tests for this task when included in tasksel
        '''
        tests = dict((key.split('-', 1)[1], value)
                     for key, value in self.header.items()
                     if key.startswith('Test-'))
        if self.install:
            tests['new-install'] = 'mark show'
        return tests

    @property
    def all(self):
        '''All Base Dependencies of this task
        '''
        return list(itertools.chain(
            *itertools.chain(self.dependencies,
                             self.recommends,
                             self.suggests)))

    def gen_control(self):
        '''Return the task as ``Deb822`` object suitable for ``debian/control``

        >>> with open('education') as fp:
        ...     task = Task('debian-astro', 'education', fp)
        >>> print(task.gen_control().dump())
        Package: astro-education
        Section: metapackages
        Architecture: all
        Recommends: celestia-gnome | celestia-glut,
                    gravit,
                    starplot
        Suggests: sunclock,
                  xtide
        Description: Educational astronomy applications
         Various applications that can be used to teach astronomy.
         .
         This is however incomplete.
        <BLANKLINE>
        '''
        d = Deb822()
        d['Package'] = self.package_name
        d['Section'] = self.section
        d['Architecture'] = self.architecture
        if self.dependencies or self.base_deps:
            d['Depends'] = ",\n         ".join(sorted(
                self.base_deps
                + list(set(d.rawstr for d in self.dependencies))
            ))
        if self.recommends:
            d['Recommends'] = ",\n            ".join(sorted(
                set(d.rawstr for d in self.recommends)
            ))
        if self.suggests:
            d['Suggests'] = ",\n          ".join(sorted(
                set(d.rawstr for d in self.suggests)
            ))
        d['Description'] = self.summary + '\n ' + \
            "\n ".join(self.description.replace("\n\n", "\n.\n").split("\n"))
        return d

    def gen_task_desc(self, udeb=False):
        '''Return the task as ``Deb822`` object suitable for ``blends-task.desc``.

        :parameter udeb: if ``True``, generate ```blends-task.desc``
                         suitable for udebs

        >>> with open('education') as fp:
        ...     task = Task('debian-astro', 'education', fp)
        >>> print(task.gen_task_desc().dump())
        Task: astro-education
        Parent: debian-astro
        Section: debian-astro
        Description: Educational astronomy applications
         Various applications that can be used to teach astronomy.
         .
         This is however incomplete.
        Test-new-install: mark show
        Key:
         astro-education
        <BLANKLINE>

        '''
        d = Deb822()
        d['Task'] = self.package_name
        if not udeb:
            d['Parent'] = self.blend
        d['Section'] = self.blend
        d['Description'] = self.summary + '\n ' + \
            "\n ".join(self.description.replace("\n\n", "\n.\n").split("\n"))
        if udeb:
            d['Relevance'] = '10'
        if self.enhances:
            d['Enhances'] = ', '.join(sorted(d.name for d in itertools.chain(
                *self.enhances)))
        for key, value in self.tests.items():
            d['Test-' + key] = value
        d['Key'] = '\n {}'.format(self.package_name)
        return d

    def update(self, cache):
        '''Update from cache

        This adds the available versions to all dependencies. It updates
        descriptions, summaries etc. available to all BaseDependencies.

        :param cache: ``apt.Cache`` like object

        Instead of using ``update()``, also the ``+=`` operator can be used:

        >>> import apt
        >>> with open('education') as fp:
        ...     task = Task('debian-astro', 'education', fp)
        >>> dep = task.recommends[1][0]
        >>> print(dep.name + ": ", dep.summary)
        starplot:  None
        >>> task += apt.Cache()
        >>> print(dep.name + ": ", dep.summary)
        starplot:  3-dimensional perspective star map viewer
        '''
        for dep in self.all:
            pkg = cache.get(dep.name)
            if pkg is not None:
                dep.target_versions += pkg.versions
            if hasattr(cache, 'get_providing_packages'):
                for pkg in cache.get_providing_packages(dep.name):
                    dep.target_versions += pkg.versions

    def __iadd__(self, cache):
        self.update(cache)
        return self

    def fix_dependencies(self):
        '''Fix the dependencies according to available packages

        This lowers all unavailable ``recommended`` dependencies to
        ``suggested``.

        >>> import apt
        >>> with open('education') as fp:
        ...     task = Task('debian-astro', 'education', fp)
        >>> for dep in task.recommends:
        ...     print(dep.rawstr)
        celestia-gnome | celestia-glut
        starplot
        gravit
        >>> for dep in task.suggests:
        ...     print(dep.rawstr)
        sunclock
        xtide
        >>> task += apt.Cache()
        >>> missing = task.fix_dependencies()
        >>> for dep in task.recommends:
        ...     print(dep.rawstr)
        starplot
        gravit
        >>> for dep in task.suggests:
        ...     print(dep.rawstr)
        sunclock
        xtide
        celestia-gnome | celestia-glut
        '''
        missing = list()
        for recommended in self.recommends[:]:
            suggested = Dependency("Suggests")
            for dep in recommended[:]:
                if len(dep.target_versions) == 0:
                    recommended.remove(dep)
                    suggested.append(dep)
                    missing.append(dep)
            if len(recommended) == 0:
                self.recommends.remove(recommended)
            if len(suggested) > 0:
                self.suggests.append(suggested)
        return missing

    @staticmethod
    def upgrade_from_1_0(content):
        header = [("Format", "https://blends.debian.org/blends/1.1")]
        header += list(filter(lambda x: x[0] != "Format", content[0].items()))
        res = [dict(header)]
        for p in content[1:]:
            q = []
            for key, value in p.items():
                if key == 'Depends' and 'Recommends' not in p:
                    key = 'Recommends'
                # Remove backslashes, which are not DEB822 compliant
                value = re.sub(r'\s*\\', '', value)
                q.append((key, value))
            res.append(dict(q))
        return Deb822List(res)


class Dependency(list):
    '''Represent an Or-group of dependencies.

    Example:

    >>> with open('education') as fp:
    ...     task = Task('debian-astro', 'education', fp)
    >>> dep = task.recommends[0]
    >>> print(dep.rawstr)
    celestia-gnome | celestia-glut
    '''

    def __init__(self, rawtype, s=None, content=None):
        super(Dependency, self).__init__(BaseDependency(bs.strip(), content)
                                         for bs in (s.split("|") if s else []))
        self.rawtype = rawtype
        '''The type of the dependencies in the Or-group'''

    @property
    def or_dependencies(self):
        return self

    @property
    def rawstr(self):
        '''String represenation of the Or-group of dependencies.

        Returns the string representation of the Or-group of
        dependencies as it would be written in the ``debian/control``
        file.  The string representation does not include the type of
        the Or-group of dependencies.
        '''
        return ' | '.join(bd.rawstr for bd in self)

    @property
    def target_versions(self):
        '''A list of all Version objects which satisfy this Or-group of deps.
        '''
        return list(itertools.chain(bd.target_versions for bd in self))


class BaseDependency:
    '''A single dependency.

    Example:

    >>> with open('education') as fp:
    ...     task = Task('debian-astro', 'education', fp)
    >>> dep = task.recommends[2][0]
    >>> print(dep.rawstr)
    gravit
    >>> print(dep.wnpp)
    743379
    >>> print(dep.homepage)
    http://gravit.slowchop.com/
    >>> print(dep.description)
    Gravit is a free, visually stunning gravity simulator.
    <BLANKLINE>
    You can spend endless time experimenting with various
    configurations of simulated universes.
    >>> print(dep.summary)
    Visually stunning gravity simulator
    '''

    def __init__(self, s, content=None):
        r = re.compile(r'([a-z0-9][a-z0-9+-\.]+)')
        m = r.match(s)
        if m is None or m.string != s:
            raise ValueError('"{}" is not a valid package name'.format(s))
        self.name = s
        self.content = content or dict()
        self.target_versions = []

    def _get_from_target_versions(self, key):
        for v in self.target_versions:
            if v.package.name == self.name:
                return getattr(v, key)

    @property
    def rawstr(self):
        '''String represenation of the dependency.

        Returns the string representation of the dependency as it
        would be written in the ``debian/control`` file.  The string
        representation does not include the type of the dependency.
        '''
        return self.name

    @property
    def wnpp(self):
        '''The WNPP bug number, if available, or None
        '''
        return self.content.get("WNPP")

    @property
    def homepage(self):
        '''Return the homepage for the package.
        '''
        return self._get_from_target_versions("homepage") or \
            self.content.get("Homepage")

    @property
    def description(self):
        '''Return the formatted long description.
        '''
        desc = self._get_from_target_versions("description")
        if desc is not None:
            return desc
        desc = self.content.get("Pkg-Description",
                                self.content.get("Description"))
        if desc:
            return "\n".join(line[1:] if line != ' .' else ''
                             for line in desc.split("\n")[1:])

    @property
    def summary(self):
        '''Return the short description (one line summary).
        '''
        summary = self._get_from_target_versions("summary")
        if summary:
            return summary

        desc = self.content.get("Pkg-Description",
                                self.content.get("Description"))
        if desc:
            return desc.split('\n')[0]

    @property
    def why(self):
        return self.content.get("Why")

    @property
    def remark(self):
        return self.content.get("Remark")


class Deb822List(list):
    '''A list of ``Deb822`` paragraphs
    '''
    def __init__(self, paragraphs):
        list.__init__(self, (p if isinstance(p, Deb822) else Deb822(p)
                             for p in paragraphs))

    def dump(self, fd=None, encoding=None, text_mode=False):
        '''Dump the the contents in the original format

        If ``fd`` is ``None``, returns a ``str`` object. Otherwise,
        ``fd`` is assumed to be a ``file``-like object, and this
        method will write the data to it instead of returning an
        ``str`` object.

        If ``fd`` is not ``None`` and ``text_mode`` is ``False``, the
        data will be encoded to a byte string before writing to the
        file.  The encoding used is chosen via the encoding parameter;
        None means to use the encoding the object was initialized with
        (utf-8 by default).  This will raise ``UnicodeEncodeError`` if
        the encoding can't support all the characters in the
        ``Deb822Dict`` values.

        '''
        if fd is None:
            fd = io.StringIO()
            return_string = True
        else:
            return_string = False

        for p in self:
            p.dump(fd, encoding, text_mode)
            fd.write("\n")

        if return_string:
            return fd.getvalue()


def aptcache(release=None, srcdirs=['/etc/blends']):
    '''Open and update a (temporary) apt cache for the specified distribution.

    :param release: Distribution name

    :param srcdirs: List of directories to search for
        ``sources.list.<<release>>``

    If the distribution is not given, use the system's cache without update.
    '''
    import tempfile
    import apt

    if release is None:
        return apt.Cache()
    rootdir = tempfile.mkdtemp()
    try:
        os.makedirs(os.path.join(rootdir, 'etc', 'apt'))
        shutil.copytree('/etc/apt/trusted.gpg.d',
                        os.path.join(rootdir, 'etc', 'apt', 'trusted.gpg.d'))
        for src_dir in srcdirs:
            sources_list = os.path.join(src_dir,
                                        'sources.list.{}'.format(release))
            if os.path.exists(sources_list):
                shutil.copy(sources_list,
                            os.path.join(rootdir, 'etc/apt/sources.list'))
                break
        else:
            raise OSError("sources.list not found in " + str(srcdirs))
        cache = apt.Cache(rootdir=rootdir, memonly=True)
        cache.update()
        cache.open()
    finally:
        shutil.rmtree(rootdir)
    return cache


def uddcache(packages, release, components=['main'], **db_args):
    '''Create a ``dict`` from UDD that is roughly modelled after ``apt.Cache``.

    The ``dict`` just resolves the version number and archs for the packages.
    For performance reasons, an initial package list needs to be given.

    :param release: Distribution name
    :param packages: Initial package list
    :param db_args: UDD connection parameters

    ``Provided`` dependencies are integrated in the returned ``dict``.
    '''
    import collections
    import psycopg2

    pkgtuple = tuple(set(p.name for p in packages))

    componenttuple = tuple(components)

    Package = collections.namedtuple('Package',
                                     ('name', 'versions',))
    Version = collections.namedtuple('Version',
                                     ('package', 'architecture', 'version'))

    # To make the SELECT statements easier, we create a virtual view
    # of the "packages" table that is restricted to the release and
    # the component(s)
    pkg_view_stmt = '''
    CREATE TEMPORARY VIEW pkg
    AS SELECT packages.package,
           packages.version,
           packages.architecture,
           packages.provides
    FROM packages, releases
    WHERE packages.release=releases.release
        AND (releases.release=%s  OR releases.role=%s)
        AND packages.component IN %s;
    '''

    # Since the "provides" are in a comma separated list, we create a
    # normalized view
    provides_view_stmt = '''
    CREATE TEMPORARY VIEW provides
    AS SELECT DISTINCT
        package,
        version,
        architecture,
        regexp_split_to_table(regexp_replace(provides,
                                             E'\\\\s*\\\\([^)]*\\\\)',
                                             '', 'g'),
                              E',\\\\s*') AS provides
    FROM pkg;
    '''

    # Query all packages that have one of the specified names either as
    # package name, or as one of the provides
    query_stmt = '''
    SELECT package,
           version,
           architecture,
           provides
    FROM pkg
    WHERE package IN %s
    UNION
    SELECT package,
           version,
           architecture,
           provides
    FROM provides
    WHERE provides IN %s;
    '''

    with psycopg2.connect(**db_args) as conn:
        cursor = conn.cursor()
        cursor.execute(pkg_view_stmt, (release, release, componenttuple))
        cursor.execute(provides_view_stmt)
        cursor.execute(query_stmt, (pkgtuple, pkgtuple))

        cache = dict()
        for package, version, arch, provides in cursor:
            p = cache.setdefault(package, Package(package, []))
            p.versions.append(Version(p, arch, version))
            if provides:
                for prv in provides.split(','):
                    pp = cache.setdefault(prv, Package(package, []))
                    pp.versions.append(Version(p, arch, version))
        return cache