"""Discover repository properties like repository root, proof root, etc."""

# Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
# SPDX-License-Identifier: MIT-0

from pathlib import Path
from subprocess import Popen, PIPE
import logging

import git

from cbmc_starter_kit import ctagst

################################################################
# Construct an ascending relative path like "../../.." from a
# directory to an ancestor in the file system.
#
# The Path method dst.relative_to(src) requires that dst is a
# descendant of src and will not produce a path like "../../..".

def path_to_ancestor(descendant, ancestor):
    """Relative path from descendant to ancestor."""

    descendant = Path(descendant).resolve()
    ancestor = Path(ancestor).resolve()

    try:
        path = descendant.relative_to(ancestor)
    except ValueError:
        raise UserWarning(f"{ancestor} is not an ancestor of {descendant}") from ValueError

    return Path(*[Path('..') for part in path.parts])

################################################################
# Discover the roots of
#   * the respository and
#   * the proofs subtree installed by the starter kit
#   * the directory containing GitHub Actions workflows

def repository_root(cwd='.', abspath=True):
    """Path to root of repository containing current directory.

    Return the absolute path if abspath is True.  If abspath is False,
    return the relative path from the current directory.  If the
    current directory is within a submodule of the repository, then
    the root of the submodule is returned, not the repository itself.
    """

    try:
        root = git.Repo(cwd, search_parent_directories=True).working_dir
        return Path(root) if abspath else path_to_ancestor(cwd, root)
    except git.InvalidGitRepositoryError:
        raise UserWarning(f"No git repository contains {cwd}") from None

def proofs_root(cwd='.', abspath=True):
    """Path to root of proofs subtree installed by starter kit.

    Return an absolute path if abspath is True, and a path relative to
    cwd otherwise.  Search starts at cwd and ascends until it reaches
    the root of the enclosing repository, and raises UserWarning if
    there is no enclosing repository."""

    cwd = Path(cwd).resolve()                     # Where to start looking
    root = repository_root(cwd=cwd, abspath=True) # Where to stop looking
    proofs = "proofs"                             # What to look for

    for path in [cwd, *cwd.parents]:
        if path.name == proofs:
            return path if abspath else path_to_ancestor(cwd, path)
        if path == root:
            break
    raise UserWarning(f"'{cwd}' has no ancestor named '{proofs}'")

def _get_directory_paths(start):
    """Generate path to subdirectory, only if it is not a git submodule

    This is used in identifying the CBMC proof root subdirectory."""
    for path in start.iterdir():
        if not path.is_dir() or git.repo.fun.is_git_dir(path):
            continue
        yield path

def get_abspath_to_proofs_root(start):
    """Return absolute path to CBMC proof root."""
    for path in _get_directory_paths(start):
        if path.name == "proofs":
            return path.absolute()
        proofs_dir = get_abspath_to_proofs_root(start=path)
        if proofs_dir:
            return proofs_dir

def get_relative_path_from_repository_to_proofs_root():
    """Return str version of absolute path to CBMC proof root.

    This function starts from the root of the repository and traverses all
    subdirectories.w"""
    repo_root = repository_root(abspath=True)
    return str(get_abspath_to_proofs_root(repo_root).relative_to(repo_root))

def github_actions_workflows_root(cwd='.', abspath=True):
    """Path to directory containing GitHub Actions workflows."""

    return repository_root(cwd=cwd, abspath=abspath) / ".github" / "workflows"

################################################################
# Discover the set of all source files in the repository that define a
# function named func.

def run(cmd, cwd=None, stdin=None):
    """Run a command with string stdin on stdin, return stdout and stderr."""

    cmd = [str(word) for word in cmd]
    try:
        with Popen(cmd, cwd=cwd, text=True, stdin=PIPE, stdout=PIPE, stderr=PIPE) as pipe:
            stdout, stderr = pipe.communicate(input=stdin)
        if pipe.returncode:
            logging.debug("Nonzero return code %s: command: '%s'", pipe.returncode, ' '.join(cmd))
            logging.debug("Nonzero return code %s: stderr: '%s'", pipe.returncode, pipe.stderr)
            return None, None
        return stdout, stderr
    except FileNotFoundError:
        logging.debug("FileNotFoundError: command '%s'", ' '.join(cmd))
        return None, None

def function_tags(repo='.'):
    """List of tags for function definitions in respository source files.

    Each tag is a dict '{"name": function, "path": source}' naming a
    function and a source file defining the function."""

    repo = Path(repo).resolve()

    find_cmd = ['find', '.', '-name', '*.c']
    files, _ = run(find_cmd, cwd=repo)
    if files is None: # run() logs errors on debug
        return []

    # legacy ctags does not give the kind of a symbol
    # assume a symbol is a function if the kind is None
    tags = ctagst.ctags(repo, files.split())
    return [tag for tag in tags if tag['kind'] in ['function', None]]

def function_paths(func, tags):
    """Paths to all source files in tags defining a function func."""

    return sorted([tag['file'] for tag in tags if tag['symbol'] == func])

def function_sources(func, cwd='.', repo='.'):
    """Paths to all source files in the repository defining a function func.

    Paths are absolute if abspath is True, and relative to cwd otherwise.

    """

    cwd = Path(cwd).resolve()
    repo = Path(repo).resolve()

    tags = function_tags(repo)
    sources = function_paths(func, tags)

    assert all(src.is_file() for src in sources)
    return sources

################################################################