#!/usr/bin/env python3
"""Check proposed changes for common issues."""
import re
import sys
import shutil
import os.path
import subprocess
import sysconfig

import reindent
import untabify


def get_python_source_dir():
    src_dir = sysconfig.get_config_var('abs_srcdir')
    if not src_dir:
        src_dir = sysconfig.get_config_var('srcdir')
    return os.path.abspath(src_dir)


# Excluded directories which are copies of external libraries:
# don't check their coding style
EXCLUDE_DIRS = [
    os.path.join('Modules', '_decimal', 'libmpdec'),
    os.path.join('Modules', 'expat'),
    os.path.join('Modules', 'zlib'),
    ]
SRCDIR = get_python_source_dir()


def n_files_str(count):
    """Return 'N file(s)' with the proper plurality on 'file'."""
    s = "s" if count != 1 else ""
    return f"{count} file{s}"


def status(message, modal=False, info=None):
    """Decorator to output status info to stdout."""
    def decorated_fxn(fxn):
        def call_fxn(*args, **kwargs):
            sys.stdout.write(message + ' ... ')
            sys.stdout.flush()
            result = fxn(*args, **kwargs)
            if not modal and not info:
                print("done")
            elif info:
                print(info(result))
            else:
                print("yes" if result else "NO")
            return result
        return call_fxn
    return decorated_fxn


def get_git_branch():
    """Get the symbolic name for the current git branch"""
    cmd = "git rev-parse --abbrev-ref HEAD".split()
    try:
        return subprocess.check_output(cmd,
                                       stderr=subprocess.DEVNULL,
                                       cwd=SRCDIR,
                                       encoding='UTF-8')
    except subprocess.CalledProcessError:
        return None


def get_git_upstream_remote():
    """
    Get the remote name to use for upstream branches

    Check for presence of "https://github.com/python/cpython" remote URL.
    If only one is found, return that remote name. If multiple are found,
    check for and return "upstream", "origin", or "python", in that
    order. Raise an error if no valid matches are found.
    """
    cmd = "git remote -v".split()
    output = subprocess.check_output(
        cmd,
        stderr=subprocess.DEVNULL,
        cwd=SRCDIR,
        encoding="UTF-8"
    )
    # Filter to desired remotes, accounting for potential uppercasing
    filtered_remotes = {
        remote.split("\t")[0].lower() for remote in output.split('\n')
        if "python/cpython" in remote.lower() and remote.endswith("(fetch)")
    }
    if len(filtered_remotes) == 1:
        [remote] = filtered_remotes
        return remote
    for remote_name in ["upstream", "origin", "python"]:
        if remote_name in filtered_remotes:
            return remote_name
    remotes_found = "\n".join(
        {remote for remote in output.split('\n') if remote.endswith("(fetch)")}
    )
    raise ValueError(
        f"Patchcheck was unable to find an unambiguous upstream remote, "
        f"with URL matching 'https://github.com/python/cpython'. "
        f"For help creating an upstream remote, see Dev Guide: "
        f"https://devguide.python.org/getting-started/"
        f"git-boot-camp/#cloning-a-forked-cpython-repository "
        f"\nRemotes found: \n{remotes_found}"
        )


def get_git_remote_default_branch(remote_name):
    """Get the name of the default branch for the given remote

    It is typically called 'main', but may differ
    """
    cmd = f"git remote show {remote_name}".split()
    env = os.environ.copy()
    env['LANG'] = 'C'
    try:
        remote_info = subprocess.check_output(cmd,
                                              stderr=subprocess.DEVNULL,
                                              cwd=SRCDIR,
                                              encoding='UTF-8',
                                              env=env)
    except subprocess.CalledProcessError:
        return None
    for line in remote_info.splitlines():
        if "HEAD branch:" in line:
            base_branch = line.split(":")[1].strip()
            return base_branch
    return None


@status("Getting base branch for PR",
        info=lambda x: x if x is not None else "not a PR branch")
def get_base_branch():
    if not os.path.exists(os.path.join(SRCDIR, '.git')):
        # Not a git checkout, so there's no base branch
        return None
    upstream_remote = get_git_upstream_remote()
    version = sys.version_info
    if version.releaselevel == 'alpha':
        base_branch = get_git_remote_default_branch(upstream_remote)
    else:
        base_branch = "{0.major}.{0.minor}".format(version)
    this_branch = get_git_branch()
    if this_branch is None or this_branch == base_branch:
        # Not on a git PR branch, so there's no base branch
        return None
    return upstream_remote + "/" + base_branch


@status("Getting the list of files that have been added/changed",
        info=lambda x: n_files_str(len(x)))
def changed_files(base_branch=None):
    """Get the list of changed or added files from git."""
    if os.path.exists(os.path.join(SRCDIR, '.git')):
        # We just use an existence check here as:
        #  directory = normal git checkout/clone
        #  file = git worktree directory
        if base_branch:
            cmd = 'git diff --name-status ' + base_branch
        else:
            cmd = 'git status --porcelain'
        filenames = []
        with subprocess.Popen(cmd.split(),
                              stdout=subprocess.PIPE,
                              cwd=SRCDIR) as st:
            git_file_status, _ = st.communicate()
            if st.returncode != 0:
                sys.exit(f'error running {cmd}')
            for line in git_file_status.splitlines():
                line = line.decode().rstrip()
                status_text, filename = line.split(maxsplit=1)
                status = set(status_text)
                # modified, added or unmerged files
                if not status.intersection('MAU'):
                    continue
                if ' -> ' in filename:
                    # file is renamed
                    filename = filename.split(' -> ', 2)[1].strip()
                filenames.append(filename)
    else:
        sys.exit('need a git checkout to get modified files')

    filenames2 = []
    for filename in filenames:
        # Normalize the path to be able to match using .startswith()
        filename = os.path.normpath(filename)
        if any(filename.startswith(path) for path in EXCLUDE_DIRS):
            # Exclude the file
            continue
        filenames2.append(filename)

    return filenames2


def report_modified_files(file_paths):
    count = len(file_paths)
    if count == 0:
        return n_files_str(count)
    else:
        lines = [f"{n_files_str(count)}:"]
        for path in file_paths:
            lines.append(f"  {path}")
        return "\n".join(lines)


#: Python files that have tabs by design:
_PYTHON_FILES_WITH_TABS = frozenset({
    'Tools/c-analyzer/cpython/_parser.py',
})


@status("Fixing Python file whitespace", info=report_modified_files)
def normalize_whitespace(file_paths):
    """Make sure that the whitespace for .py files have been normalized."""
    reindent.makebackup = False  # No need to create backups.
    fixed = [
        path for path in file_paths
        if (
            path.endswith('.py')
            and path not in _PYTHON_FILES_WITH_TABS
            and reindent.check(os.path.join(SRCDIR, path))
        )
    ]
    return fixed


@status("Fixing C file whitespace", info=report_modified_files)
def normalize_c_whitespace(file_paths):
    """Report if any C files """
    fixed = []
    for path in file_paths:
        abspath = os.path.join(SRCDIR, path)
        with open(abspath, 'r') as f:
            if '\t' not in f.read():
                continue
        untabify.process(abspath, 8, verbose=False)
        fixed.append(path)
    return fixed


@status("Docs modified", modal=True)
def docs_modified(file_paths):
    """Report if any file in the Doc directory has been changed."""
    return bool(file_paths)


@status("Misc/ACKS updated", modal=True)
def credit_given(file_paths):
    """Check if Misc/ACKS has been changed."""
    return os.path.join('Misc', 'ACKS') in file_paths


@status("Misc/NEWS.d updated with `blurb`", modal=True)
def reported_news(file_paths):
    """Check if Misc/NEWS.d has been changed."""
    return any(p.startswith(os.path.join('Misc', 'NEWS.d', 'next'))
               for p in file_paths)


@status("configure regenerated", modal=True, info=str)
def regenerated_configure(file_paths):
    """Check if configure has been regenerated."""
    if 'configure.ac' in file_paths:
        return "yes" if 'configure' in file_paths else "no"
    else:
        return "not needed"


@status("pyconfig.h.in regenerated", modal=True, info=str)
def regenerated_pyconfig_h_in(file_paths):
    """Check if pyconfig.h.in has been regenerated."""
    if 'configure.ac' in file_paths:
        return "yes" if 'pyconfig.h.in' in file_paths else "no"
    else:
        return "not needed"


def ci(pull_request):
    if pull_request == 'false':
        print('Not a pull request; skipping')
        return
    base_branch = get_base_branch()
    file_paths = changed_files(base_branch)
    python_files = [fn for fn in file_paths if fn.endswith('.py')]
    c_files = [fn for fn in file_paths if fn.endswith(('.c', '.h'))]
    fixed = []
    fixed.extend(normalize_whitespace(python_files))
    fixed.extend(normalize_c_whitespace(c_files))
    if not fixed:
        print('No whitespace issues found')
    else:
        count = len(fixed)
        print(f'Please fix the {n_files_str(count)} with whitespace issues')
        print('(on Unix you can run `make patchcheck` to make the fixes)')
        sys.exit(1)


def main():
    base_branch = get_base_branch()
    file_paths = changed_files(base_branch)
    python_files = [fn for fn in file_paths if fn.endswith('.py')]
    c_files = [fn for fn in file_paths if fn.endswith(('.c', '.h'))]
    doc_files = [fn for fn in file_paths if fn.startswith('Doc') and
                 fn.endswith(('.rst', '.inc'))]
    misc_files = {p for p in file_paths if p.startswith('Misc')}
    # PEP 8 whitespace rules enforcement.
    normalize_whitespace(python_files)
    # C rules enforcement.
    normalize_c_whitespace(c_files)
    # Docs updated.
    docs_modified(doc_files)
    # Misc/ACKS changed.
    credit_given(misc_files)
    # Misc/NEWS changed.
    reported_news(misc_files)
    # Regenerated configure, if necessary.
    regenerated_configure(file_paths)
    # Regenerated pyconfig.h.in, if necessary.
    regenerated_pyconfig_h_in(file_paths)

    # Test suite run and passed.
    if python_files or c_files:
        end = " and check for refleaks?" if c_files else "?"
        print()
        print("Did you run the test suite" + end)


if __name__ == '__main__':
    import argparse
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument('--ci',
                        help='Perform pass/fail checks')
    args = parser.parse_args()
    if args.ci:
        ci(args.ci)
    else:
        main()