| 1 | ### -*-python-*- |
| 2 | ### |
| 3 | ### Subcommand dispatch |
| 4 | ### |
| 5 | ### (c) 2013 Mark Wooding |
| 6 | ### |
| 7 | |
| 8 | ###----- Licensing notice --------------------------------------------------- |
| 9 | ### |
| 10 | ### This file is part of Chopwood: a password-changing service. |
| 11 | ### |
| 12 | ### Chopwood is free software; you can redistribute it and/or modify |
| 13 | ### it under the terms of the GNU Affero General Public License as |
| 14 | ### published by the Free Software Foundation; either version 3 of the |
| 15 | ### License, or (at your option) any later version. |
| 16 | ### |
| 17 | ### Chopwood is distributed in the hope that it will be useful, |
| 18 | ### but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 19 | ### MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 20 | ### GNU Affero General Public License for more details. |
| 21 | ### |
| 22 | ### You should have received a copy of the GNU Affero General Public |
| 23 | ### License along with Chopwood; if not, see |
| 24 | ### <http://www.gnu.org/licenses/>. |
| 25 | |
| 26 | from __future__ import with_statement |
| 27 | |
| 28 | import optparse as OP |
| 29 | from cStringIO import StringIO |
| 30 | import sys as SYS |
| 31 | |
| 32 | from output import OUT |
| 33 | import util as U |
| 34 | |
| 35 | ### We've built enough infrastructure now: it's time to move on to user |
| 36 | ### interface stuff. |
| 37 | ### |
| 38 | ### Everything is done in terms of `subcommands'. A subcommand has a name, a |
| 39 | ### set of `contexts' in which it's active (see below), a description (for |
| 40 | ### help), a function, and a bunch of parameters. There are a few different |
| 41 | ### kinds of parameters, but the basic idea is that they have names and |
| 42 | ### values. When we invoke a subcommand, we'll pass the parameter values as |
| 43 | ### keyword arguments to the function. |
| 44 | ### |
| 45 | ### We have a fair number of different interfaces to provide: there's an |
| 46 | ### administration interface for adding and removing new users and accounts; |
| 47 | ### there's a GNU Userv interface for local users to change their passwords; |
| 48 | ### there's an SSH interface for remote users and for acting as a remote |
| 49 | ### service; and there's a CGI interface. To make life a little more |
| 50 | ### confusing, sets of commands don't map one-to-one with these various |
| 51 | ### interfaces: for example, the remote-user SSH interface is (basically) the |
| 52 | ### same as the Userv interface, and the CGI interface offers two distinct |
| 53 | ### command sets depending on whether the user has authenticated. |
| 54 | ### |
| 55 | ### We call these various command sets `contexts'. To be useful, a |
| 56 | ### subcommand must be active within at least one context. Command lookup |
| 57 | ### takes place with a specific context in mind, and command names only need |
| 58 | ### be unique within a particular context. Commands from a different context |
| 59 | ### are simply unavailable. |
| 60 | ### |
| 61 | ### When it comes to parameters, we have simple positional arguments, and |
| 62 | ### fancy options. Positional arguments are called this because on the |
| 63 | ### command line they're only distinguished by their order. Like Lisp |
| 64 | ### functions, a subcommand has some of mandatory formal arguments, followed |
| 65 | ### by some optional arguments, and finally maybe a `rest' argument which |
| 66 | ### gobbles up any remaining actual arguments as a list. To make things more |
| 67 | ### fun, we also have options, which conform to the usual Unix command-line |
| 68 | ### conventions. |
| 69 | ### |
| 70 | ### Finally, there's a global set of options, always read from the command |
| 71 | ### line, which affects stuff like which configuration file to use, and can |
| 72 | ### also be useful in testing and debugging. |
| 73 | |
| 74 | ###-------------------------------------------------------------------------- |
| 75 | ### Parameters. |
| 76 | |
| 77 | ## The global options. This will carry the option values once they've been |
| 78 | ## parsed. |
| 79 | OPTS = None |
| 80 | |
| 81 | class Parameter (object): |
| 82 | """ |
| 83 | Base class for parameters. |
| 84 | |
| 85 | Currently only stores the parameter's name, which does double duty as the |
| 86 | name of the handler function's keyword argument which will receive this |
| 87 | parameter's value, and the parameter name in the CGI interface from which |
| 88 | the value is read. |
| 89 | """ |
| 90 | def __init__(me, name): |
| 91 | me.name = name |
| 92 | |
| 93 | class Opt (Parameter): |
| 94 | """ |
| 95 | An option, i.e., one which is presented as an option-flag in command-line |
| 96 | interfaces. |
| 97 | |
| 98 | The SHORT and LONG strings are the option flags for this parameter. The |
| 99 | SHORT string should be a single `-' followed by a single character (usually |
| 100 | a letter. The LONG string should be a pair `--' followed by a name |
| 101 | (usually words, joined with hyphens). |
| 102 | |
| 103 | The HELP is presented to the user as a description of the option. |
| 104 | |
| 105 | The ARGNAME may be either `None' to indicate that this is a simple boolean |
| 106 | switch (the value passed to the handler function will be `True' or |
| 107 | `False'), or a string (conventionally in uppercase, used as a metasyntactic |
| 108 | variable in the generated usage synopsis) to indicate that the option takes |
| 109 | a general string argument (passed literally to the handler function). |
| 110 | """ |
| 111 | def __init__(me, name, short, long, help, argname = None): |
| 112 | Parameter.__init__(me, name) |
| 113 | me.short = short |
| 114 | me.long = long |
| 115 | me.help = help |
| 116 | me.argname = argname |
| 117 | |
| 118 | class Arg (Parameter): |
| 119 | """ |
| 120 | A (positional) argument. Nothing much to do here. |
| 121 | |
| 122 | The parameter name, converted to upper case, is used as a metasyntactic |
| 123 | variable in the generated usage synopsis. |
| 124 | """ |
| 125 | pass |
| 126 | |
| 127 | ###-------------------------------------------------------------------------- |
| 128 | ### Subcommands. |
| 129 | |
| 130 | class Subcommand (object): |
| 131 | """ |
| 132 | A subcommand object. |
| 133 | |
| 134 | Many interesting things about the subcommand are made available as |
| 135 | attributes. |
| 136 | |
| 137 | `name' |
| 138 | The subcommand name. Used to look the command up (see |
| 139 | the `lookup_subcommand' method of `SubcommandOptionParser'), and in |
| 140 | usage and help messages. |
| 141 | |
| 142 | `contexts' |
| 143 | A set (coerced from any iterable provided to the constructor) of |
| 144 | contexts in which this subcommand is available. |
| 145 | |
| 146 | `desc' |
| 147 | A description of the subcommand, provided if the user requests |
| 148 | detailed help. |
| 149 | |
| 150 | `func' |
| 151 | The handler function, invoked to actually carry out the subcommand. |
| 152 | |
| 153 | `opts' |
| 154 | A list of `Opt' objects, used to build the option parser. |
| 155 | |
| 156 | `params', `oparams', `rparam' |
| 157 | `Arg' objects for the positional parameters. `params' is a list of |
| 158 | mandatory parameters; `oparams' is a list of optional parameters; and |
| 159 | `rparam' is either an `Arg' for the `rest' parameter, or `None' if |
| 160 | there is no `rest' parameter. |
| 161 | """ |
| 162 | |
| 163 | def __init__(me, name, contexts, desc, func, opts = [], |
| 164 | params = [], oparams = [], rparam = None): |
| 165 | """ |
| 166 | Initialize a subcommand object. The constructors arguments are used to |
| 167 | initialize attributes on the object; see the class docstring for details. |
| 168 | """ |
| 169 | me.name = name |
| 170 | me.contexts = set(contexts) |
| 171 | me.desc = desc |
| 172 | me.opts = opts |
| 173 | me.params = params |
| 174 | me.oparams = oparams |
| 175 | me.rparam = rparam |
| 176 | me.func = func |
| 177 | |
| 178 | def usage(me): |
| 179 | """Generate a suitable usage summary for the subcommand.""" |
| 180 | |
| 181 | ## Cache the summary in an attribute. |
| 182 | try: return me._usage |
| 183 | except AttributeError: pass |
| 184 | |
| 185 | ## Gather up a list of switches and options with arguments. |
| 186 | u = [] |
| 187 | sw = [] |
| 188 | for o in me.opts: |
| 189 | if o.argname: |
| 190 | if o.short: u.append('[%s %s]' % (o.short, o.argname.upper())) |
| 191 | else: u.append('%s=%s' % (o.long, o.argname.upper())) |
| 192 | else: |
| 193 | if o.short: sw.append(o.short[1]) |
| 194 | else: u.append(o.long) |
| 195 | |
| 196 | ## Generate the usage message. |
| 197 | me._usage = ' '.join( |
| 198 | [me.name] + # The command name. |
| 199 | (sw and ['[-%s]' % ''.join(sorted(sw))] or []) + |
| 200 | # Switches, in order. |
| 201 | sorted(u) + # Options with arguments, and |
| 202 | # options without short names. |
| 203 | [p.name.upper() for p in me.params] + |
| 204 | # Required arguments, in order. |
| 205 | ['[%s]' % p.name.upper() for p in me.oparams] + |
| 206 | # Optional arguments, in order. |
| 207 | (me.rparam and ['[%s ...]' % me.rparam.name.upper()] or [])) |
| 208 | # The `rest' argument, if present. |
| 209 | |
| 210 | ## And return it. |
| 211 | return me._usage |
| 212 | |
| 213 | def mkoptparse(me): |
| 214 | """ |
| 215 | Make and return an `OptionParser' object for this subcommand. |
| 216 | |
| 217 | This is used for dispatching through a command-line interface, and for |
| 218 | generating subcommand-specific help. |
| 219 | """ |
| 220 | op = OP.OptionParser(usage = 'usage: %%prog %s' % me.usage(), |
| 221 | description = me.desc) |
| 222 | for o in me.opts: |
| 223 | op.add_option(o.short, o.long, dest = o.name, help = o.help, |
| 224 | action = o.argname and 'store' or 'store_true', |
| 225 | metavar = o.argname) |
| 226 | return op |
| 227 | |
| 228 | def cmdline(me, args): |
| 229 | """ |
| 230 | Invoke the subcommand given a list ARGS of command-line arguments. |
| 231 | """ |
| 232 | |
| 233 | ## Parse any options. |
| 234 | op = me.mkoptparse() |
| 235 | opts, args = op.parse_args(args) |
| 236 | |
| 237 | ## Count up the remaining positional arguments supplied, and how many |
| 238 | ## mandatory and optional arguments we want. |
| 239 | na = len(args) |
| 240 | np = len(me.params) |
| 241 | nop = len(me.oparams) |
| 242 | |
| 243 | ## Complain if there's a mismatch. |
| 244 | if na < np or (not me.rparam and na > np + nop): |
| 245 | raise U.ExpectedError, (400, 'Wrong number of arguments') |
| 246 | |
| 247 | ## Now we want to gather the parameters into a dictionary. |
| 248 | kw = {} |
| 249 | |
| 250 | ## First, work through the various options. The option parser tends to |
| 251 | ## define attributes for omitted options with the value `None': we leave |
| 252 | ## this out of the keywords dictionary so that the subcommand can provide |
| 253 | ## its own default values. |
| 254 | for o in me.opts: |
| 255 | try: v = getattr(opts, o.name) |
| 256 | except AttributeError: pass |
| 257 | else: |
| 258 | if v is not None: kw[o.name] = v |
| 259 | |
| 260 | ## Next, assign values from positional arguments to the corresponding |
| 261 | ## parameters. |
| 262 | for a, p in zip(args, me.params + me.oparams): |
| 263 | kw[p.name] = a |
| 264 | |
| 265 | ## If we have a `rest' parameter then set it to any arguments which |
| 266 | ## haven't yet been consumed. |
| 267 | if me.rparam: |
| 268 | kw[me.rparam.name] = na > np + nop and args[np + nop:] or [] |
| 269 | |
| 270 | ## Call the handler function. |
| 271 | me.func(**kw) |
| 272 | |
| 273 | ###-------------------------------------------------------------------------- |
| 274 | ### Option parsing with subcommands. |
| 275 | |
| 276 | class SubcommandOptionParser (OP.OptionParser, object): |
| 277 | """ |
| 278 | A subclass of `OptionParser' with some additional knowledge about |
| 279 | subcommands. |
| 280 | |
| 281 | The current context is maintained in the `context' attribute, which can be |
| 282 | freely assigned by the client. The initial value is chosen as the first in |
| 283 | the CONTEXTS list, which is otherwise only used to set up the `help' |
| 284 | command. |
| 285 | """ |
| 286 | |
| 287 | def __init__(me, usage = '%prog [-OPTIONS] COMMAND [ARGS ...]', |
| 288 | contexts = ['cli'], commands = [], *args, **kw): |
| 289 | """ |
| 290 | Constructor for the options parser. As for the superclass, but with an |
| 291 | additional argument CONTEXTS used for initializing the `help' command. |
| 292 | """ |
| 293 | super(SubcommandOptionParser, me).__init__(usage = usage, *args, **kw) |
| 294 | me._cmds = commands |
| 295 | |
| 296 | ## We must turn of the `interspersed arguments' feature: otherwise we'll |
| 297 | ## eat the subcommand's arguments. |
| 298 | me.disable_interspersed_args() |
| 299 | me.context = list(contexts)[0] |
| 300 | |
| 301 | ## Provide a default `help' command. |
| 302 | me._cmds = {} |
| 303 | me.addsubcmd(Subcommand( |
| 304 | 'help', contexts, |
| 305 | func = me.cmd_help, |
| 306 | desc = 'Show help for %prog, or for the COMMANDs.', |
| 307 | rparam = Arg('commands'))) |
| 308 | for sub in commands: me.addsubcmd(sub) |
| 309 | |
| 310 | def addsubcmd(me, sub): |
| 311 | """Add a subcommand to the main map.""" |
| 312 | for c in sub.contexts: |
| 313 | me._cmds[sub.name, c] = sub |
| 314 | |
| 315 | def print_help(me, file = None, *args, **kw): |
| 316 | """ |
| 317 | Print a help message. This augments the superclass behaviour by printing |
| 318 | synopses for the available subcommands. |
| 319 | """ |
| 320 | if file is None: file = SYS.stdout |
| 321 | super(SubcommandOptionParser, me).print_help(file = file, *args, **kw) |
| 322 | file.write('\nCommands:\n') |
| 323 | for sub in sorted(set(me._cmds.values()), key = lambda c: c.name): |
| 324 | if sub.desc is None or me.context not in sub.contexts: continue |
| 325 | file.write('\t%s\n' % sub.usage()) |
| 326 | |
| 327 | def cmd_help(me, commands = []): |
| 328 | """ |
| 329 | A default `help' command. With arguments, print help about those; |
| 330 | otherwise just print help on the main program, as for `--help'. |
| 331 | """ |
| 332 | s = StringIO() |
| 333 | if not commands: |
| 334 | me.print_help(file = s) |
| 335 | else: |
| 336 | sep = '' |
| 337 | for name in commands: |
| 338 | s.write(sep) |
| 339 | sep = '\n' |
| 340 | c = me.lookup_subcommand(name) |
| 341 | c.mkoptparse().print_help(file = s) |
| 342 | OUT.write(s.getvalue()) |
| 343 | |
| 344 | def lookup_subcommand(me, name, exactp = False, context = None): |
| 345 | """ |
| 346 | Find the subcommand with the given NAME in the CONTEXT (default the |
| 347 | current context). Unless EXACTP, accept a command for which NAME is an |
| 348 | unambiguous prefix. Return the subcommand object, or raise an |
| 349 | appropriate `ExpectedError'. |
| 350 | """ |
| 351 | |
| 352 | if context is None: context = me.context |
| 353 | |
| 354 | ## See if we can find an exact match. |
| 355 | try: c = me._cmds[name, context] |
| 356 | except KeyError: pass |
| 357 | else: return c |
| 358 | |
| 359 | ## No. Maybe we'll find a prefix match. |
| 360 | match = [] |
| 361 | if not exactp: |
| 362 | for c in set(me._cmds.values()): |
| 363 | if context in c.contexts and \ |
| 364 | c.name.startswith(name): |
| 365 | match.append(c) |
| 366 | |
| 367 | ## See what we came up with. |
| 368 | if len(match) == 0: |
| 369 | raise U.ExpectedError, (404, "Unknown command `%s'" % name) |
| 370 | elif len(match) > 1: |
| 371 | raise U.ExpectedError, ( |
| 372 | 404, |
| 373 | ("Ambiguous command `%s': could be any of %s" % |
| 374 | (name, ', '.join("`%s'" % c.name for c in match)))) |
| 375 | else: |
| 376 | return match[0] |
| 377 | |
| 378 | def dispatch(me, context, args): |
| 379 | """ |
| 380 | Invoke the appropriate subcommand, indicated by ARGS, within the CONTEXT. |
| 381 | """ |
| 382 | global OPTS |
| 383 | if not args: raise U.ExpectedError, (400, "Missing command") |
| 384 | me.context = context |
| 385 | c = me.lookup_subcommand(args[0]) |
| 386 | c.cmdline(args[1:]) |
| 387 | |
| 388 | ###-------------------------------------------------------------------------- |
| 389 | ### Registry of subcommands. |
| 390 | |
| 391 | ## Our list of commands. We'll attach this to the options parser when we're |
| 392 | ## ready to roll. |
| 393 | COMMANDS = [] |
| 394 | |
| 395 | def subcommand(name, contexts, desc, cls = Subcommand, |
| 396 | opts = [], params = [], oparams = [], rparam = None): |
| 397 | """Decorator for defining subcommands.""" |
| 398 | def _(func): |
| 399 | COMMANDS.append(cls(name, contexts, desc, func, |
| 400 | opts, params, oparams, rparam)) |
| 401 | return _ |
| 402 | |
| 403 | ###----- That's all, folks -------------------------------------------------- |