# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
# vim: set filetype=python:
# This Source Code Form is subject to the terms of the Mozilla Public
# License, v. 2.0. If a copy of the MPL was not distributed with this
# file, You can obtain one at http://mozilla.org/MPL/2.0/.

# Templates implementing some generic checks.
# ==============================================================

# Declare some exceptions. This is cumbersome, but since we shouldn't need a
# lot of them, let's stack them all here. When adding a new one, put it in the
# _declare_exceptions template, and add it to the return statement. Then
# destructure in the assignment below the function declaration.


@template
@imports(_from="__builtin__", _import="Exception")
def _declare_exceptions():
    class FatalCheckError(Exception):
        """An exception to throw from a function decorated with @checking.
        It will result in calling die() with the given message.
        Debugging messages emitted from the decorated function will also be
        printed out."""

    return (FatalCheckError,)


(FatalCheckError,) = _declare_exceptions()

del _declare_exceptions

# Helper to display "checking" messages
#   @checking('for foo')
#   def foo():
#       return 'foo'
# is equivalent to:
#   def foo():
#       log.info('checking for foo... ')
#       ret = foo
#       log.info(ret)
#       return ret
# This can be combined with e.g. @depends:
#   @depends(some_option)
#   @checking('for something')
#   def check(value):
#       ...
# An optional callback can be given, that will be used to format the returned
# value when displaying it.


@template
def checking(what, callback=None):
    def decorator(func):
        def wrapped(*args, **kwargs):
            log.info("checking %s... ", what)
            with log.queue_debug():
                error, ret = None, None
                try:
                    ret = func(*args, **kwargs)
                except FatalCheckError as e:
                    error = str(e)
                display_ret = callback(ret) if callback else ret
                if display_ret is True:
                    log.info("yes")
                elif display_ret is False or display_ret is None:
                    log.info("no")
                else:
                    log.info(display_ret)
                if error is not None:
                    die(error)
            return ret

        return wrapped

    return decorator


# Template to check for programs in $PATH.
# - `var` is the name of the variable that will be set with `set_config` when
#   the program is found.
# - `progs` is a list (or tuple) of program names that will be searched for.
#   It can also be a reference to a @depends function that returns such a
#   list. If the list is empty and there is no input, the check is skipped.
# - `what` is a human readable description of what is being looked for. It
#   defaults to the lowercase version of `var`.
# - `input` is a string reference to an existing option or a reference to a
#   @depends function resolving to explicit input for the program check.
#   The default is to create an option for the environment variable `var`.
#   This argument allows to use a different kind of option (possibly using a
#   configure flag), or doing some pre-processing with a @depends function.
# - `allow_missing` indicates whether not finding the program is an error.
# - `paths` is a list of paths or @depends function returning a list of paths
#   that will cause the given path(s) to be searched rather than $PATH. Input
#   paths may either be individual paths or delimited by os.pathsep, to allow
#   passing $PATH (for example) as an element.
# - `bootstrap` is a path relative to the bootstrap root path (e.g ~/.mozbuild)
#   where to find the program if it's bootstrapped.
# - `validate` is a callback function that takes a path and returns True if
#   the program at that location is appropriate or not, or False if not.
#   when the callback returns False, check_prog ignores the program and goes
#   on to the next from the `progs` list.
#
# - `bootstrap_search_path` is not an argument that users of the template are
#   supposed to pass. See the override of check_prog in top-level moz.configure.
#
# The simplest form is:
#   check_prog('PROG', ('a', 'b'))
# This will look for 'a' or 'b' in $PATH, and set_config PROG to the one
# it can find. If PROG is already set from the environment or command line,
# use that value instead.
@template
@imports(_from="mozbuild.shellutil", _import="quote")
def check_prog(
    var,
    progs,
    what=None,
    input=None,
    allow_missing=False,
    paths=None,
    allow_spaces=False,
    bootstrap=None,
    when=None,
    validate=None,
    bootstrap_search_path=None,
):
    if input is not None:
        # Wrap input with type checking and normalization.
        @depends(input, when=when)
        def input(value):
            if not value:
                return
            if isinstance(value, str):
                return (value,)
            if isinstance(value, (tuple, list)) and len(value) == 1:
                return value
            configure_error(
                "input must resolve to a tuple or a list with a "
                "single element, or a string"
            )

    else:
        option(
            env=var,
            nargs=1,
            when=when,
            help="Path to %s" % (what or "the %s program" % var.lower()),
        )
        input = var
    what = what or var.lower()

    # Trick to make a @depends function out of an immediate value.
    progs = dependable(progs)
    paths = dependable(paths)
    allow_missing = dependable(allow_missing)

    if bootstrap:
        if input is var:
            # A when is needed when depending on an option, so normalize
            # to a function that can used without.
            has_input = depends(input, when=when)(lambda x: x)
        else:
            has_input = input
        # We don't want to bootstrap when an explicit value was given as input.
        if when:
            bootstrap_when = depends(when, has_input)(lambda w, i: w and not i)
        else:
            bootstrap_when = depends(has_input)(lambda i: not i)
        paths = bootstrap_search_path(bootstrap, paths, when=bootstrap_when)

    # Avoid displaying the "Checking for" message when the inputs are such
    # that we don't actually want anything to be checked. It is a bit
    # convoluted because of how `when` works.
    # We first wrap all the inputs except allow_missing (which doesn't count
    # for whether to display the "Checking for" message).
    @depends_if(input, progs, paths, when=when)
    def inputs(input, progs, paths):
        if progs is None:
            progs = ()

        if not isinstance(progs, (tuple, list)):
            configure_error("progs must resolve to a list or tuple!")

        return namespace(value=input, progs=progs, paths=paths)

    @depends(inputs, allow_missing, when=inputs)
    @checking("for %s" % what, lambda x: quote(x) if x else "not found")
    def check(inputs, allow_missing):
        value = inputs.value
        progs = inputs.progs
        paths = inputs.paths

        for prog in value or progs:
            log.debug("%s: Looking for %s", var.lower(), quote(prog))
            result = find_program(prog, paths, allow_spaces)
            if validate and result and not validate(result):
                log.debug("%s: %s found but didn't work", var.lower(), quote(result))
                continue
            if result:
                return result

        if not allow_missing or value:
            raise FatalCheckError("Cannot find %s" % what)

    set_config(var, check)

    return check