# ruff: noqa: UP007 UP045
# @omlish-lite
"""
TODO:
 - https://www.rootusers.com/how-to-change-log-rate-limiting-in-linux/

==

https://www.freedesktop.org/software/systemd/man/latest/journalctl.html

Source Options
--system, --user
    Show messages from system services and the kernel (with --system). Show messages from service of current user (with
    --user). If neither is specified, show all messages that the user can see. The --user option affects how --unit=
    arguments are treated. See --unit=. Note that --user only works if persistent logging is enabled, via the Storage=
    setting in journald.conf(5).
-M, --machine=
    Show messages from a running, local container. Specify a container name to connect to.
-m, --merge
    Show entries interleaved from all available journals, including remote ones.
-D DIR, --directory=DIR
    Takes a directory path as argument. If specified, journalctl will operate on the specified journal directory DIR
    instead of the default runtime and system journal paths.
-i GLOB, --file=GLOB
    Takes a file glob as an argument. If specified, journalctl will operate on the specified journal files matching GLOB
    instead of the default runtime and system journal paths. May be specified multiple times, in which case files will
    be suitably interleaved.
--root=ROOT
    Takes a directory path as an argument. If specified, journalctl will operate on journal directories and catalog file
    hierarchy underneath the specified directory instead of the root directory (e.g. --update-catalog will create
    ROOT/var/lib/systemd/catalog/database, and journal files under ROOT/run/journal/ or ROOT/var/log/journal/ will be
    displayed).
--image=IMAGE
    Takes a path to a disk image file or block device node. If specified, journalctl will operate on the file system in
    the indicated disk image. This option is similar to --root=, but operates on file systems stored in disk images or
    block devices, thus providing an easy way to extract log data from disk images. The disk image should either contain
    just a file system or a set of file systems within a GPT partition table, following the Discoverable Partitions
    Specification. For further information on supported disk images, see systemd-nspawn(1)'s switch of the same name.
--image-policy=policy
    Takes an image policy string as argument, as per systemd.image-policy(7). The policy is enforced when operating on
    the disk image specified via --image=, see above. If not specified defaults to the "*" policy, i.e. all recognized
    file systems in the image are used.
--namespace=NAMESPACE
    Takes a journal namespace identifier string as argument. If not specified the data collected by the default
    namespace is shown. If specified shows the log data of the specified namespace instead. If the namespace is
    specified as "*" data from all namespaces is shown, interleaved. If the namespace identifier is prefixed with "+"
    data from the specified namespace and the default namespace is shown, interleaved, but no other. For details about
    journal namespaces see systemd-journald.service(8).

Filtering Options
-S, --since=, -U, --until=
    Start showing entries on or newer than the specified date, or on or older than the specified date, respectively.
    Date specifications should be of the format "2012-10-30 18:17:16". If the time part is omitted, "00:00:00" is
    assumed. If only the seconds component is omitted, ":00" is assumed. If the date component is omitted, the current
    day is assumed. Alternatively the strings "yesterday", "today", "tomorrow" are understood, which refer to 00:00:00
    of the day before the current day, the current day, or the day after the current day, respectively. "now" refers to
    the current time. Finally, relative times may be specified, prefixed with "-" or "+", referring to times before or
    after the current time, respectively. For complete time and date specification, see systemd.time(7). Note that
    --output=short-full prints timestamps that follow precisely this format.
-c, --cursor=
    Start showing entries from the location in the journal specified by the passed cursor.
--after-cursor=
    Start showing entries from the location in the journal after the location specified by the passed cursor. The cursor
    is shown when the --show-cursor option is used.
--cursor-file=FILE
    If FILE exists and contains a cursor, start showing entries after this location. Otherwise show entries according to
    the other given options. At the end, write the cursor of the last entry to FILE. Use this option to continually read
    the journal by sequentially calling journalctl.
-b [[ID][±offset]|all], --boot[=[ID][±offset]|all]
    Show messages from a specific boot. This will add a match for "_BOOT_ID=". The argument may be empty, in which case
    logs for the current boot will be shown. If the boot ID is omitted, a positive offset will look up the boots
    starting from the beginning of the journal, and an equal-or-less-than zero offset will look up boots starting from
    the end of the journal. Thus, 1 means the first boot found in the journal in chronological order, 2 the second and
    so on; while -0 is the last boot, -1 the boot before last, and so on. An empty offset is equivalent to specifying
    -0, except when the current boot is not the last boot (e.g. because --directory= was specified to look at logs from
    a different machine). If the 32-character ID is specified, it may optionally be followed by offset which identifies
    the boot relative to the one given by boot ID. Negative values mean earlier boots and positive values mean later
    boots. If offset is not specified, a value of zero is assumed, and the logs for the boot given by ID are shown. The
    special argument all can be used to negate the effect of an earlier use of -b.
-u, --unit=UNIT|PATTERN
    Show messages for the specified systemd unit UNIT (such as a service unit), or for any of the units matched by
    PATTERN. If a pattern is specified, a list of unit names found in the journal is compared with the specified pattern
    and all that match are used. For each unit name, a match is added for messages from the unit ("_SYSTEMD_UNIT=UNIT"),
    along with additional matches for messages from systemd and messages about coredumps for the specified unit. A match
    is also added for "_SYSTEMD_SLICE=UNIT", such that if the provided UNIT is a systemd.slice(5) unit, all logs of
    children of the slice will be shown. With --user, all --unit= arguments will be converted to match user messages as
    if specified with --user-unit=. This parameter can be specified multiple times.
--user-unit=
    Show messages for the specified user session unit. This will add a match for messages from the unit
    ("_SYSTEMD_USER_UNIT=" and "_UID=") and additional matches for messages from session systemd and messages about
    coredumps for the specified unit. A match is also added for "_SYSTEMD_USER_SLICE=UNIT", such that if the provided
    UNIT is a systemd.slice(5) unit, all logs of children of the unit will be shown. This parameter can be specified
    multiple times.
-t, --identifier=SYSLOG_IDENTIFIER
    Show messages for the specified syslog identifier SYSLOG_IDENTIFIER. This parameter can be specified multiple times.
-T, --exclude-identifier=SYSLOG_IDENTIFIER
    Exclude messages for the specified syslog identifier SYSLOG_IDENTIFIER. This parameter can be specified multiple
    times.
-p, --priority=
    Filter output by message priorities or priority ranges. Takes either a single numeric or textual log level (i.e.
    between 0/"emerg" and 7/"debug"), or a range of numeric/text log levels in the form FROM..TO. The log levels are the
    usual syslog log levels as documented in syslog(3), i.e. "emerg" (0), "alert" (1), "crit" (2), "err" (3), "warning"
    (4), "notice" (5), "info" (6), "debug" (7). If a single log level is specified, all messages with this log level or
    a lower (hence more important) log level are shown. If a range is specified, all messages within the range are
    shown, including both the start and the end value of the range. This will add "PRIORITY=" matches for the specified
    priorities.
--facility=
    Filter output by syslog facility. Takes a comma-separated list of numbers or facility names. The names are the usual
    syslog facilities as documented in syslog(3). --facility=help may be used to display a list of known facility names
    and exit.
-g, --grep=
    Filter output to entries where the MESSAGE= field matches the specified regular expression. PERL-compatible regular
    expressions are used, see pcre2pattern(3) for a detailed description of the syntax. If the pattern is all lowercase,
    matching is case insensitive. Otherwise, matching is case sensitive. This can be overridden with the
    --case-sensitive option, see below. When used with --lines= (not prefixed with "+"), --reverse is implied.
--case-sensitive[=BOOLEAN]
    Make pattern matching case sensitive or case insensitive.
-k, --dmesg
    Show only kernel messages. This implies -b and adds the match "_TRANSPORT=kernel".

Output Options
-o, --output=
    Controls the formatting of the journal entries that are shown. Takes one of the following options:
        short
            is the default and generates an output that is mostly identical to the formatting of classic syslog files,
            showing one line per journal entry.
        short-full
            is very similar, but shows timestamps in the format the --since= and --until= options accept. Unlike the
            timestamp information shown in short output mode this mode includes weekday, year and timezone information
            in the output, and is locale-independent.
        short-iso
            is very similar, but shows timestamps in the RFC 3339 profile of ISO 8601.
        short-iso-precise
            as for short-iso but includes full microsecond precision.
        short-precise
            is very similar, but shows classic syslog timestamps with full microsecond precision.
        short-monotonic
            is very similar, but shows monotonic timestamps instead of wallclock timestamps.
        short-delta
            as for short-monotonic but includes the time difference to the previous entry. Maybe unreliable time
            differences are marked by a "*".
        short-unix
            is very similar, but shows seconds passed since January 1st 1970 UTC instead of wallclock timestamps ("UNIX
            time"). The time is shown with microsecond accuracy.
        verbose
            shows the full-structured entry items with all fields.
        export
            serializes the journal into a binary (but mostly text-based) stream suitable for backups and network
            transfer (see Journal Export Format for more information). To import the binary stream back into native
            journald format use systemd-journal-remote(8).
        json
            formats entries as JSON objects, separated by newline characters (see Journal JSON Format for more
            information). Field values are generally encoded as JSON strings, with three exceptions: Fields larger than
            4096 bytes are encoded as null values. (This may be turned off by passing --all, but be aware that this may
            allocate overly long JSON objects.) Journal entries permit non-unique fields within the same log entry. JSON
            does not allow non-unique fields within objects. Due to this, if a non-unique field is encountered a JSON
            array is used as field value, listing all field values as elements. Fields containing non-printable or
            non-UTF8 bytes are encoded as arrays containing the raw bytes individually formatted as unsigned numbers.
            Note that this encoding is reversible (with the exception of the size limit).
        json-pretty
            formats entries as JSON data structures, but formats them in multiple lines in order to make them more
            readable by humans.
        json-sse
            formats entries as JSON data structures, but wraps them in a format suitable for Server-Sent Events.
        json-seq
            formats entries as JSON data structures, but prefixes them with an ASCII Record Separator character (0x1E)
            and suffixes them with an ASCII Line Feed character (0x0A), in accordance with JavaScript Object Notation
            (JSON) Text Sequences ("application/json-seq").
        cat
            generates a very terse output, only showing the actual message of each journal entry with no metadata, not
            even a timestamp. If combined with the --output-fields= option will output the listed fields for each log
            record, instead of the message.
        with-unit
            similar to short-full, but prefixes the unit and user unit names instead of the traditional syslog
            identifier. Useful when using templated instances, as it will include the arguments in the unit names.
--truncate-newline
    Truncate each log message at the first newline character on output, so that only the first line of each message is
    displayed.
--output-fields=
    A comma separated list of the fields which should be included in the output. This has an effect only for the output
    modes which would normally show all fields (verbose, export, json, json-pretty, json-sse and json-seq), as well as
    on cat. For the former, the "__CURSOR", "__REALTIME_TIMESTAMP", "__MONOTONIC_TIMESTAMP", and "_BOOT_ID" fields are
    always printed.
-n, --lines=
    Show the most recent journal events and limit the number of events shown. The argument is a positive integer or
    "all" to disable the limit. Additionally, if the number is prefixed with "+", the oldest journal events are used
    instead. The default value is 10 if no argument is given. If --follow is used, this option is implied. When not
    prefixed with "+" and used with --grep=, --reverse is implied.
-r, --reverse
    Reverse output so that the newest entries are displayed first.
--show-cursor
    The cursor is shown after the last entry after two dashes:
-- cursor: s=0639...
    The format of the cursor is private and subject to change.
--utc
    Express time in Coordinated Universal Time (UTC).
-x, --catalog
    Augment log lines with explanation texts from the message catalog. This will add explanatory help texts to log
    messages in the output where this is available. These short help texts will explain the context of an error or log
    event, possible solutions, as well as pointers to support forums, developer documentation, and any other relevant
    manuals. Note that help texts are not available for all messages, but only for selected ones. For more information
    on the message catalog, see Journal Message Catalogs. Note: when attaching journalctl output to bug reports, please
    do not use -x.
--no-hostname
    Don't show the hostname field of log messages originating from the local host. This switch has an effect only on the
    short family of output modes (see above). Note: this option does not remove occurrences of the hostname from log
    entries themselves, so it does not prevent the hostname from being visible in the logs.
--no-full, --full, -l
    Ellipsize fields when they do not fit in available columns. The default is to show full fields, allowing them to
    wrap or be truncated by the pager, if one is used. The old options -l/--full are not useful anymore, except to undo
    --no-full.
-a, --all
    Show all fields in full, even if they include unprintable characters or are very long. By default, fields with
    unprintable characters are abbreviated as "blob data". (Note that the pager may escape unprintable characters
    again.)
-f, --follow
    Show only the most recent journal entries, and continuously print new entries as they are appended to the journal.
--no-tail
    Show all stored output lines, even in follow mode. Undoes the effect of --lines=.
-q, --quiet
    Suppresses all informational messages (i.e. "-- Journal begins at ...", "-- Reboot --"), any warning messages
    regarding inaccessible system journals when run as a normal user.

Pager Control Options
--no-pager
    Do not pipe output into a pager.
-e, --pager-end
    Immediately jump to the end of the journal inside the implied pager tool. This implies -n1000 to guarantee that the
    pager will not buffer logs of unbounded size. This may be overridden with an explicit -n with some other numeric
    value, while -nall will disable this cap. Note that this option is only supported for the less(1) pager.

Forward Secure Sealing (FSS) Options
--interval=
    Specifies the change interval for the sealing key when generating an FSS key pair with --setup-keys. Shorter
    intervals increase CPU consumption but shorten the time range of undetectable journal alterations. Defaults to
    15min.
--verify-key=
    Specifies the FSS verification key to use for the --verify operation.
--force
    When --setup-keys is passed and Forward Secure Sealing (FSS) has already been configured, recreate FSS keys.

Commands
-N, --fields
    Print all field names currently used in all entries of the journal.
-F, --field=
    Print all possible data values the specified field can take in all entries of the journal.
--list-boots
    Show a tabular list of boot numbers (relative to the current boot), their IDs, and the timestamps of the first and
    last message pertaining to the boot. When specified with -n/--lines=[+]N option, only the first (when the number
    prefixed with "+") or the last (without prefix) N entries will be shown. When specified with -r/--reverse, the list
    will be shown in the reverse order.
--disk-usage
    Shows the current disk usage of all journal files. This shows the sum of the disk usage of all archived and active
    journal files.
--vacuum-size=, --vacuum-time=, --vacuum-files=
    --vacuum-size=
        removes the oldest archived journal files until the disk space they use falls below the specified size. Accepts
        the usual "K", "M", "G" and "T" suffixes (to the base of 1024).
    --vacuum-time=
        removes archived journal files older than the specified timespan. Accepts the usual "s" (default), "m", "h",
        "days", "weeks", "months", and "years" suffixes, see systemd.time(7) for details.
    --vacuum-files=
        leaves only the specified number of separate journal files. Note that running --vacuum-size= has only an
        indirect effect on the output shown by --disk-usage, as the latter includes active journal files, while the
        vacuuming operation only operates on archived journal files. Similarly,
    --vacuum-files= might not actually reduce the number of journal files to below the specified number, as it will not
    remove active journal files.
    --vacuum-size=, --vacuum-time= and --vacuum-files= may be combined in a single invocation to enforce any combination
    of a size, a time and a number of files limit on the archived journal files. Specifying any of these three
    parameters as zero is equivalent to not enforcing the specific limit, and is thus redundant.
    These three switches may also be combined with --rotate into one command. If so, all active files are rotated first,
    and the requested vacuuming operation is executed right after. The rotation has the effect that all currently active
    files are archived (and potentially new, empty journal files opened as replacement), and hence the vacuuming
    operation has the greatest effect as it can take all log data written so far into account.
--verify
    Check the journal file for internal consistency. If the file has been generated with FSS enabled and the FSS
    verification key has been specified with --verify-key=, authenticity of the journal file is verified.
--sync
    Asks the journal daemon to write all yet unwritten journal data to the backing file system and synchronize all
    journals. This call does not return until the synchronization operation is complete. This command guarantees that
    any log messages written before its invocation are safely stored on disk at the time it returns.
--relinquish-var
    Asks the journal daemon for the reverse operation to --flush: if requested the daemon will write further log data to
    /run/log/journal/ and stops writing to /var/log/journal/. A subsequent call to --flush causes the log output to
    switch back to /var/log/journal/, see above.
--smart-relinquish-var
    Similar to --relinquish-var, but executes no operation if the root file system and /var/log/journal/ reside on the
    same mount point. This operation is used during system shutdown in order to make the journal daemon stop writing
    data to /var/log/journal/ in case that directory is located on a mount point that needs to be unmounted.
--flush
    Asks the journal daemon to flush any log data stored in /run/log/journal/ into /var/log/journal/, if persistent
    storage is enabled. This call does not return until the operation is complete. Note that this call is idempotent:
    the data is only flushed from /run/log/journal/ into /var/log/journal/ once during system runtime (but see
    --relinquish-var below), and this command exits cleanly without executing any operation if this has already
    happened. This command effectively guarantees that all data is flushed to /var/log/journal/ at the time it returns.
--rotate
    Asks the journal daemon to rotate journal files. This call does not return until the rotation operation is complete.
    Journal file rotation has the effect that all currently active journal files are marked as archived and renamed, so
    that they are never written to in future. New (empty) journal files are then created in their place. This operation
    may be combined with --vacuum-size=, --vacuum-time= and --vacuum-file= into a single command, see above.
--header
    Instead of showing journal contents, show internal header information of the journal fields accessed. This option is
    particularly useful when trying to identify out-of-order journal entries, as happens for example when the machine is
    booted with the wrong system time.
--list-catalog [128-bit-ID...]
    List the contents of the message catalog as a table of message IDs, plus their short description strings. If any
    128-bit-IDs are specified, only those entries are shown.
--dump-catalog [128-bit-ID...]
    Show the contents of the message catalog, with entries separated by a line consisting of two dashes and the ID (the
    format is the same as .catalog files). If any 128-bit-IDs are specified, only those entries are shown.
--update-catalog
    Update the message catalog index. This command needs to be executed each time new catalog files are installed,
    removed, or updated to rebuild the binary catalog index.
--setup-keys
    Instead of showing journal contents, generate a new key pair for Forward Secure Sealing (FSS). This will generate a
    sealing key and a verification key. The sealing key is stored in the journal data directory and shall remain on the
    host. The verification key should be stored externally. Refer to the Seal= option in journald.conf(5) for
    information on Forward Secure Sealing and for a link to a refereed scholarly paper detailing the cryptographic
    theory it is based on.
-h, --help
    Print a short help text and exit.
--version
    Print a short version string and exit.

Environment
$SYSTEMD_LOG_LEVEL
    The maximum log level of emitted messages (messages with a higher log level, i.e. less important ones, will be
    suppressed). Takes a comma-separated list of values. A value may be either one of (in order of decreasing
    importance) emerg, alert, crit, err, warning, notice, info, debug, or an integer in the range 0...7. See syslog(3)
    for more information. Each value may optionally be prefixed with one of console, syslog, kmsg or journal followed by
    a colon to set the maximum log level for that specific log target (e.g. SYSTEMD_LOG_LEVEL=debug,console:info
    specifies to log at debug level except when logging to the console which should be at info level). Note that the
    global maximum log level takes priority over any per target maximum log levels.
$SYSTEMD_LOG_COLOR
    A boolean. If true, messages written to the tty will be colored according to priority. This setting is only useful
    when messages are written directly to the terminal, because journalctl(1) and other tools that display logs will
    color messages based on the log level on their own.
$SYSTEMD_LOG_TIME
    A boolean. If true, console log messages will be prefixed with a timestamp. This setting is only useful when
    messages are written directly to the terminal or a file, because journalctl(1) and other tools that display logs
    will attach timestamps based on the entry metadata on their own.
$SYSTEMD_LOG_LOCATION
    A boolean. If true, messages will be prefixed with a filename and line number in the source code where the message
    originates. Note that the log location is often attached as metadata to journal entries anyway. Including it
    directly in the message text can nevertheless be convenient when debugging programs.
$SYSTEMD_LOG_TID
    A boolean. If true, messages will be prefixed with the current numerical thread ID (TID). Note that the this
    information is attached as metadata to journal entries anyway. Including it directly in the message text can
    nevertheless be convenient when debugging programs.
$SYSTEMD_LOG_TARGET
    The destination for log messages. One of console (log to the attached tty), console-prefixed (log to the attached
    tty but with prefixes encoding the log level and "facility", see syslog(3), kmsg (log to the kernel circular log
    buffer), journal (log to the journal), journal-or-kmsg (log to the journal if available, and to kmsg otherwise),
    auto (determine the appropriate log target automatically, the default), null (disable log output).
$SYSTEMD_LOG_RATELIMIT_KMSG
    Whether to ratelimit kmsg or not. Takes a boolean. Defaults to "true". If disabled, systemd will not ratelimit
    messages written to kmsg.
$SYSTEMD_PAGER
    Pager to use when --no-pager is not given; overrides $PAGER. If neither $SYSTEMD_PAGER nor $PAGER are set, a set of
    well-known pager implementations are tried in turn, including less(1) and more(1), until one is found. If no pager
    implementation is discovered no pager is invoked. Setting this environment variable to an empty string or the value
    "cat" is equivalent to passing --no-pager. Note: if $SYSTEMD_PAGERSECURE is not set, $SYSTEMD_PAGER (as well as
    $PAGER) will be silently ignored.
$SYSTEMD_LESS
    Override the options passed to less (by default "FRSXMK"). Users might want to change two options in particular:
        K
            This option instructs the pager to exit immediately when Ctrl+C is pressed. To allow less to handle Ctrl+C
            itself to switch back to the pager command prompt, unset this option. If the value of $SYSTEMD_LESS does not
            include "K", and the pager that is invoked is less, Ctrl+C will be ignored by the executable, and needs to
            be handled by the pager.
        X
            This option instructs the pager to not send termcap initialization and deinitialization strings to the
            terminal. It is set by default to allow command output to remain visible in the terminal even after the
            pager exits. Nevertheless, this prevents some pager functionality from working, in particular paged output
            cannot be scrolled with the mouse. Note that setting the regular $LESS environment variable has no effect
            for less invocations by systemd tools.
$SYSTEMD_LESSCHARSET
    Override the charset passed to less (by default "utf-8", if the invoking terminal is determined to be UTF-8
    compatible). Note that setting the regular $LESSCHARSET environment variable has no effect for less invocations by
    systemd tools.
$SYSTEMD_PAGERSECURE
    Takes a boolean argument. When true, the "secure" mode of the pager is enabled; if false, disabled. If
    $SYSTEMD_PAGERSECURE is not set at all, secure mode is enabled if the effective UID is not the same as the owner of
    the login session, see geteuid(2) and sd_pid_get_owner_uid(3). In secure mode, LESSSECURE=1 will be set when
    invoking the pager, and the pager shall disable commands that open or create new files or start new subprocesses.
    When $SYSTEMD_PAGERSECURE is not set at all, pagers which are not known to implement secure mode will not be used.
    (Currently only less(1) implements secure mode.) Note: when commands are invoked with elevated privileges, for
    example under sudo(8) or pkexec(1), care must be taken to ensure that unintended interactive features are not
    enabled. "Secure" mode for the pager may be enabled automatically as describe above. Setting SYSTEMD_PAGERSECURE=0
    or not removing it from the inherited environment allows the user to invoke arbitrary commands. Note that if the
    $SYSTEMD_PAGER or $PAGER variables are to be honoured, $SYSTEMD_PAGERSECURE must be set too. It might be reasonable
    to completely disable the pager using --no-pager instead.
$SYSTEMD_COLORS
    Takes a boolean argument. When true, systemd and related utilities will use colors in their output, otherwise the
    output will be monochrome. Additionally, the variable can take one of the following special values: "16", "256" to
    restrict the use of colors to the base 16 or 256 ANSI colors, respectively. This can be specified to override the
    automatic decision based on $TERM and what the console is connected to.
$SYSTEMD_URLIFY
    The value must be a boolean. Controls whether clickable links should be generated in the output for terminal
    emulators supporting this. This can be specified to override the decision that systemd makes based on $TERM and
    other conditions.
"""
import fcntl
import os.path
import queue  # noqa
import subprocess
import time
import typing as ta

from omlish.lite.cached import cached_nullary
from omlish.lite.check import check
from omlish.logs.modules import get_module_logger
from omlish.subprocesses.utils import subprocess_close
from omlish.subprocesses.wrap import subprocess_shell_wrap_exec

from ..threadworkers import ThreadWorker
from .messages import JournalctlMessage  # noqa
from .messages import JournalctlMessageBuilder


log = get_module_logger(globals())  # noqa


##


class JournalctlTailerWorker(ThreadWorker):
    DEFAULT_CMD: ta.ClassVar[ta.Sequence[str]] = ['journalctl']

    def __init__(
            self,
            output,  # type: queue.Queue[ta.Sequence[JournalctlMessage]]
            *,
            since: ta.Optional[str] = None,
            after_cursor: ta.Optional[str] = None,

            cmd: ta.Optional[ta.Sequence[str]] = None,
            shell_wrap: bool = False,

            read_size: int = 0x4000,
            sleep_s: float = 1.,

            **kwargs: ta.Any,
    ) -> None:
        super().__init__(**kwargs)

        self._output = output

        self._since = since
        self._after_cursor = after_cursor

        self._cmd = cmd or self.DEFAULT_CMD
        self._shell_wrap = shell_wrap

        self._read_size = read_size
        self._sleep_s = sleep_s

        self._builder = JournalctlMessageBuilder()

        self._proc: ta.Optional[subprocess.Popen] = None

    @cached_nullary
    def _full_cmd(self) -> ta.Sequence[str]:
        cmd = [
            *self._cmd,
            '--output', 'json',
            '--show-cursor',
            '--follow',
        ]

        if self._since is not None:
            cmd.extend(['--since', self._since])

        if self._after_cursor is not None:
            cmd.extend(['--after-cursor', self._after_cursor])

        if self._shell_wrap:
            cmd = list(subprocess_shell_wrap_exec(*cmd))

        return cmd

    def _read_loop(self, stdout: ta.IO) -> None:
        while stdout.readable():
            self._heartbeat()

            buf = stdout.read(self._read_size)
            if not buf:
                log.debug('Journalctl empty read')
                break

            log.debug('Journalctl read buffer: %r', buf)
            msgs = self._builder.feed(buf)
            if msgs:
                while True:
                    try:
                        self._output.put(msgs, timeout=1.)
                    except queue.Full:
                        self._heartbeat()
                    else:
                        break

    def _run(self) -> None:
        with subprocess.Popen(
            self._full_cmd(),
            stdout=subprocess.PIPE,
        ) as self._proc:
            try:
                stdout = check.not_none(self._proc.stdout)

                fd = stdout.fileno()
                fl = fcntl.fcntl(fd, fcntl.F_GETFL)
                fcntl.fcntl(fd, fcntl.F_SETFL, fl | os.O_NONBLOCK)

                while True:
                    self._heartbeat()

                    self._read_loop(stdout)

                    log.debug('Journalctl not readable')

                    if self._proc.poll() is not None:
                        log.critical('Journalctl process terminated')
                        return

                    time.sleep(self._sleep_s)

            finally:
                subprocess_close(self._proc)
