import os
import sys
import logging
import subprocess
from functools import lru_cache
from pkg_resources import resource_filename

from ._definitions import get_platform, FNAME_PER_PLATFORM

logger = logging.getLogger("imageio_ffmpeg")


def get_ffmpeg_exe():
    """
    Get the ffmpeg executable file. This can be the binary defined by
    the IMAGEIO_FFMPEG_EXE environment variable, the binary distributed
    with imageio-ffmpeg, an ffmpeg binary installed with conda, or the
    system ffmpeg (in that order). A RuntimeError is raised if no valid
    ffmpeg could be found.
    """

    # 1. Try environment variable. - Dont test it: the user is explicit here!
    exe = os.getenv("IMAGEIO_FFMPEG_EXE", None)
    if exe:
        return exe

    # Auto-detect
    exe = _get_ffmpeg_exe()
    if exe:
        return exe

    # Nothing was found
    raise RuntimeError(
        "No ffmpeg exe could be found. Install ffmpeg on your system, "
        "or set the IMAGEIO_FFMPEG_EXE environment variable."
    )


@lru_cache()
def _get_ffmpeg_exe():
    plat = get_platform()

    # 2. Try from here
    bin_dir = resource_filename("imageio_ffmpeg", "binaries")
    exe = os.path.join(bin_dir, FNAME_PER_PLATFORM.get(plat, ""))
    if exe and os.path.isfile(exe) and _is_valid_exe(exe):
        return exe

    # 3. Try binary from conda package
    # (installed e.g. via `conda install ffmpeg -c conda-forge`)
    if plat.startswith("win"):
        exe = os.path.join(sys.prefix, "Library", "bin", "ffmpeg.exe")
    else:
        exe = os.path.join(sys.prefix, "bin", "ffmpeg")
    if exe and os.path.isfile(exe) and _is_valid_exe(exe):
        return exe

    # 4. Try system ffmpeg command
    exe = "ffmpeg"
    if _is_valid_exe(exe):
        return exe

    return None


def _popen_kwargs(prevent_sigint=False):
    startupinfo = None
    preexec_fn = None
    creationflags = 0
    if sys.platform.startswith("win"):
        # Stops executable from flashing on Windows (see #22)
        startupinfo = subprocess.STARTUPINFO()
        startupinfo.dwFlags |= subprocess.STARTF_USESHOWWINDOW
    if prevent_sigint:
        # Prevent propagation of sigint (see #4)
        # https://stackoverflow.com/questions/5045771
        if sys.platform.startswith("win"):
            creationflags = 0x00000200
        else:
            preexec_fn = os.setpgrp  # the _pre_exec does not seem to work

    falsy = ("", "0", "false", "no")
    if os.getenv("IMAGEIO_FFMPEG_NO_PREVENT_SIGINT", "").lower() not in falsy:
        # Unset preexec_fn to work around a strange hang on fork() (see #58)
        preexec_fn = None

    return {
        "startupinfo": startupinfo,
        "creationflags": creationflags,
        "preexec_fn": preexec_fn,
    }


def _is_valid_exe(exe):
    cmd = [exe, "-version"]
    try:
        with open(os.devnull, "w") as null:
            subprocess.check_call(
                cmd, stdout=null, stderr=subprocess.STDOUT, **_popen_kwargs()
            )
        return True
    except (OSError, ValueError, subprocess.CalledProcessError):
        return False


def get_ffmpeg_version():
    """
    Get the version of the used ffmpeg executable (as a string).
    """
    exe = get_ffmpeg_exe()
    line = subprocess.check_output([exe, "-version"], **_popen_kwargs()).split(
        b"\n", 1
    )[0]
    line = line.decode(errors="ignore").strip()
    version = line.split("version", 1)[-1].lstrip().split(" ", 1)[0].strip()
    return version