#!/usr/bin/env python
# vim:fileencoding=utf-8
# License: GPL v3 Copyright: 2016, Kovid Goyal <kovid at kovidgoyal.net>

import fcntl
import os

import kitty.fast_data_types as fast_data_types

from .constants import is_macos, shell_path, terminfo_dir

if is_macos:
    from kitty.fast_data_types import cmdline_of_process, cwd_of_process as _cwd, environ_of_process as _environ_of_process

    def cwd_of_process(pid):
        return os.path.realpath(_cwd(pid))

else:

    def cmdline_of_process(pid):
        return list(filter(None, open('/proc/{}/cmdline'.format(pid), 'rb').read().decode('utf-8').split('\0')))

    def cwd_of_process(pid):
        ans = '/proc/{}/cwd'.format(pid)
        return os.path.realpath(ans)

    def _environ_of_process(pid):
        return open('/proc/{}/environ'.format(pid), 'rb').read().decode('utf-8')


def parse_environ_block(data):
    """Parse a C environ block of environment variables into a dictionary."""
    # The block is usually raw data from the target process.  It might contain
    # trailing garbage and lines that do not look like assignments.
    ret = {}
    pos = 0

    while True:
        next_pos = data.find("\0", pos)
        # nul byte at the beginning or double nul byte means finish
        if next_pos <= pos:
            break
        # there might not be an equals sign
        equal_pos = data.find("=", pos, next_pos)
        if equal_pos > pos:
            key = data[pos:equal_pos]
            value = data[equal_pos + 1:next_pos]
            ret[key] = value
        pos = next_pos + 1

    return ret


def environ_of_process(pid):
    return parse_environ_block(_environ_of_process(pid))


def remove_cloexec(fd):
    fcntl.fcntl(fd, fcntl.F_SETFD, fcntl.fcntl(fd, fcntl.F_GETFD) & ~fcntl.FD_CLOEXEC)


def default_env():
    try:
        return default_env.env
    except AttributeError:
        return os.environ


def set_default_env(val=None):
    env = os.environ.copy()
    if val:
        env.update(val)
    default_env.env = env


class Child:

    child_fd = pid = None
    forked = False

    def __init__(self, argv, cwd, opts, stdin=None, env=None, cwd_from=None):
        self.allow_remote_control = False
        if argv and argv[0] == '@':
            self.allow_remote_control = True
            if len(argv) > 1:
                argv = argv[1:]
        self.argv = argv
        if cwd_from is not None:
            try:
                cwd = cwd_of_process(cwd_from)
            except Exception:
                import traceback
                traceback.print_exc()
        else:
            cwd = os.path.expandvars(os.path.expanduser(cwd or os.getcwd()))
        self.cwd = os.path.abspath(cwd)
        self.opts = opts
        self.stdin = stdin
        self.env = env or {}

    def fork(self):
        if self.forked:
            return
        self.forked = True
        master, slave = os.openpty()  # Note that master and slave are in blocking mode
        remove_cloexec(slave)
        fast_data_types.set_iutf8(master, True)
        stdin, self.stdin = self.stdin, None
        ready_read_fd, ready_write_fd = os.pipe()
        remove_cloexec(ready_read_fd)
        if stdin is not None:
            stdin_read_fd, stdin_write_fd = os.pipe()
            remove_cloexec(stdin_read_fd)
        else:
            stdin_read_fd = stdin_write_fd = -1
        env = default_env().copy()
        env.update(self.env)
        env['TERM'] = self.opts.term
        env['COLORTERM'] = 'truecolor'
        if os.path.isdir(terminfo_dir):
            env['TERMINFO'] = terminfo_dir
        env = tuple('{}={}'.format(k, v) for k, v in env.items())
        argv = list(self.argv)
        exe = argv[0]
        if is_macos and exe == shell_path:
            # Some macOS machines need the shell to have argv[0] prefixed by
            # hyphen, see https://github.com/kovidgoyal/kitty/issues/247
            argv[0] = ('-' + exe.split('/')[-1])
        pid = fast_data_types.spawn(exe, self.cwd, tuple(argv), env, master, slave, stdin_read_fd, stdin_write_fd, ready_read_fd, ready_write_fd)
        os.close(slave)
        self.pid = pid
        self.child_fd = master
        if stdin is not None:
            os.close(stdin_read_fd)
            fast_data_types.thread_write(stdin_write_fd, stdin)
        os.close(ready_read_fd)
        self.terminal_ready_fd = ready_write_fd
        fcntl.fcntl(self.child_fd, fcntl.F_SETFL, fcntl.fcntl(self.child_fd, fcntl.F_GETFL) | os.O_NONBLOCK)
        return pid

    def mark_terminal_ready(self):
        os.close(self.terminal_ready_fd)
        self.terminal_ready_fd = -1

    @property
    def cmdline(self):
        try:
            return cmdline_of_process(self.pid) or list(self.argv)
        except Exception:
            return list(self.argv)

    @property
    def environ(self):
        try:
            return environ_of_process(self.pid)
        except Exception:
            return {}

    @property
    def current_cwd(self):
        try:
            return cwd_of_process(self.pid)
        except Exception:
            pass
