"""Build a project using PEP 517 hooks.
"""
import argparse
import logging
import os
from pip._vendor import toml
import shutil

from .envbuild import BuildEnvironment
from .wrappers import Pep517HookCaller
from .dirtools import tempdir, mkdir_p
from .compat import FileNotFoundError

log = logging.getLogger(__name__)


def validate_system(system):
    """
    Ensure build system has the requisite fields.
    """
    required = {'requires', 'build-backend'}
    if not (required <= set(system)):
        message = "Missing required fields: {missing}".format(
            missing=required-set(system),
        )
        raise ValueError(message)


def load_system(source_dir):
    """
    Load the build system from a source dir (pyproject.toml).
    """
    pyproject = os.path.join(source_dir, 'pyproject.toml')
    with open(pyproject) as f:
        pyproject_data = toml.load(f)
    return pyproject_data['build-system']


def compat_system(source_dir):
    """
    Given a source dir, attempt to get a build system backend
    and requirements from pyproject.toml. Fallback to
    setuptools but only if the file was not found or a build
    system was not indicated.
    """
    try:
        system = load_system(source_dir)
    except (FileNotFoundError, KeyError):
        system = {}
    system.setdefault(
        'build-backend',
        'setuptools.build_meta:__legacy__',
    )
    system.setdefault('requires', ['setuptools', 'wheel'])
    return system


def _do_build(hooks, env, dist, dest):
    get_requires_name = 'get_requires_for_build_{dist}'.format(**locals())
    get_requires = getattr(hooks, get_requires_name)
    reqs = get_requires({})
    log.info('Got build requires: %s', reqs)

    env.pip_install(reqs)
    log.info('Installed dynamic build dependencies')

    with tempdir() as td:
        log.info('Trying to build %s in %s', dist, td)
        build_name = 'build_{dist}'.format(**locals())
        build = getattr(hooks, build_name)
        filename = build(td, {})
        source = os.path.join(td, filename)
        shutil.move(source, os.path.join(dest, os.path.basename(filename)))


def build(source_dir, dist, dest=None, system=None):
    system = system or load_system(source_dir)
    dest = os.path.join(source_dir, dest or 'dist')
    mkdir_p(dest)

    validate_system(system)
    hooks = Pep517HookCaller(
        source_dir, system['build-backend'], system.get('backend-path')
    )

    with BuildEnvironment() as env:
        env.pip_install(system['requires'])
        _do_build(hooks, env, dist, dest)


parser = argparse.ArgumentParser()
parser.add_argument(
    'source_dir',
    help="A directory containing pyproject.toml",
)
parser.add_argument(
    '--binary', '-b',
    action='store_true',
    default=False,
)
parser.add_argument(
    '--source', '-s',
    action='store_true',
    default=False,
)
parser.add_argument(
    '--out-dir', '-o',
    help="Destination in which to save the builds relative to source dir",
)


def main(args):
    # determine which dists to build
    dists = list(filter(None, (
        'sdist' if args.source or not args.binary else None,
        'wheel' if args.binary or not args.source else None,
    )))

    for dist in dists:
        build(args.source_dir, dist, args.out_dir)


if __name__ == '__main__':
    main(parser.parse_args())