## Extract `cib` log from journald and pretty print

_Want:_ `cibtool` can extract `cib` log messages from the systemd

journal sub-system, and pretty print them, and optionally filter the

messages.

_Why:_ systemd is the common service manager for Linux systems, and it

needs to be convenient to extract `cib` log messages from its system

logging sub-system, journald. This is especially important for CI

broker developers who need to diagnose problems on remote `cib`

instances to which they don't have direct access.

_Who:_ `cib-devs`

~~~scenario

given a Radicle node, with CI configured with broker.yaml and adapter dummy.sh

given file journal.json

when I run cibtool log --journal journal.json --output x.json

when I run jq . x.json

then command is successful

when I run cibtool log --journal journal.json --broker-run-id 62c45727-a4d8-4a29-9dae-88c6e8b61655 --output x.json

when I run grep -c timestamp x.json

then stdout has one line

~~~

~~~{#journal.json .file .json}

{"__CURSOR":"s=f30566e7c34e4ba190c6c671ff826507;i=31360;b=da4ba18425ea4e34bd0f0731f0270572;m=c3256a61;t=6290db5b772ca;x=280fbc307405cb81","_SYSTEMD_UNIT":"radicle-ci-broker.service","_STREAM_ID":"9c46f4f6f0074e07986a0c3769f6545e","_SYSTEMD_SLICE":"system.slice","_CMDLINE":"/bin/cib --log-level trace --config /home/_rad/ci-broker.yaml process-events","_PID":"526","MESSAGE":"{\"timestamp\":\"2024-12-12T07:32:00.276073Z\",\"level\":\"TRACE\",\"fields\":{\"message\":\"event queue length\",\"msg_id\":\"QueueProcQueueLength\",\"kind\":\"debug\",\"len\":\"0\"}}","_RUNTIME_SCOPE":"system","_CAP_EFFECTIVE":"0","_GID":"1001","_SELINUX_CONTEXT":"unconfined\n","_SYSTEMD_INVOCATION_ID":"949b57247eb24bb5aefcec93f049beab","__MONOTONIC_TIMESTAMP":"3274009185","PRIORITY":"6","_COMM":"cib","_UID":"1001","_SYSTEMD_CGROUP":"/system.slice/radicle-ci-broker.service","_HOSTNAME":"radicle-ci","_BOOT_ID":"da4ba18425ea4e34bd0f0731f0270572","__REALTIME_TIMESTAMP":"1733988720276170","SYSLOG_IDENTIFIER":"cib","_TRANSPORT":"stdout","_EXE":"/usr/bin/cib","_MACHINE_ID":"35c654cc069c402d8cb0b34b91f12e5e","SYSLOG_FACILITY":"3"}

{"_GID":"1001","_RUNTIME_SCOPE":"system","_UID":"1001","_BOOT_ID":"da4ba18425ea4e34bd0f0731f0270572","_PID":"526","_SYSTEMD_CGROUP":"/system.slice/radicle-ci-broker.service","_SYSTEMD_INVOCATION_ID":"949b57247eb24bb5aefcec93f049beab","_CMDLINE":"/bin/cib --log-level trace --config /home/_rad/ci-broker.yaml process-events","_CAP_EFFECTIVE":"0","_SELINUX_CONTEXT":"unconfined\n","_TRANSPORT":"stdout","SYSLOG_IDENTIFIER":"cib","_MACHINE_ID":"35c654cc069c402d8cb0b34b91f12e5e","_STREAM_ID":"9c46f4f6f0074e07986a0c3769f6545e","MESSAGE":"{\"timestamp\":\"2024-12-12T07:32:01.276463Z\",\"level\":\"TRACE\",\"fields\":{\"message\":\"event queue length\",\"msg_id\":\"QueueProcQueueLength\",\"kind\":\"debug\",\"len\":\"0\"}}","_SYSTEMD_SLICE":"system.slice","__MONOTONIC_TIMESTAMP":"3275009597","PRIORITY":"6","SYSLOG_FACILITY":"3","_HOSTNAME":"radicle-ci","_EXE":"/usr/bin/cib","_COMM":"cib","_SYSTEMD_UNIT":"radicle-ci-broker.service","__CURSOR":"s=f30566e7c34e4ba190c6c671ff826507;i=31361;b=da4ba18425ea4e34bd0f0731f0270572;m=c334ae3d;t=6290db5c6b6a5;x=a9c49aef9ad2a509","__REALTIME_TIMESTAMP":"1733988721276581"}

{"__MONOTONIC_TIMESTAMP":"3276010022","SYSLOG_IDENTIFIER":"cib","_CAP_EFFECTIVE":"0","_SYSTEMD_INVOCATION_ID":"949b57247eb24bb5aefcec93f049beab","_HOSTNAME":"radicle-ci","_EXE":"/usr/bin/cib","_UID":"1001","_BOOT_ID":"da4ba18425ea4e34bd0f0731f0270572","_MACHINE_ID":"35c654cc069c402d8cb0b34b91f12e5e","_SYSTEMD_SLICE":"system.slice","_PID":"526","SYSLOG_FACILITY":"3","_COMM":"cib","PRIORITY":"6","_STREAM_ID":"9c46f4f6f0074e07986a0c3769f6545e","_SELINUX_CONTEXT":"unconfined\n","_TRANSPORT":"stdout","_SYSTEMD_UNIT":"radicle-ci-broker.service","MESSAGE":"{\"timestamp\":\"2024-12-12T07:32:02.276881Z\",\"level\":\"TRACE\",\"fields\":{\"message\":\"event queue length\",\"msg_id\":\"QueueProcQueueLength\",\"kind\":\"debug\",\"len\":\"0\"}}","__CURSOR":"s=f30566e7c34e4ba190c6c671ff826507;i=31362;b=da4ba18425ea4e34bd0f0731f0270572;m=c343f226;t=6290db5d5fa8e;x=843418c04ac1932f","_GID":"1001","_SYSTEMD_CGROUP":"/system.slice/radicle-ci-broker.service","__REALTIME_TIMESTAMP":"1733988722277006","_RUNTIME_SCOPE":"system","_CMDLINE":"/bin/cib --log-level trace --config /home/_rad/ci-broker.yaml process-events"}

{"SYSLOG_FACILITY":"3","_MACHINE_ID":"35c654cc069c402d8cb0b34b91f12e5e","__REALTIME_TIMESTAMP":"1733988723277782","_CAP_EFFECTIVE":"0","_PID":"526","_SYSTEMD_INVOCATION_ID":"949b57247eb24bb5aefcec93f049beab","_EXE":"/usr/bin/cib","_COMM":"cib","_RUNTIME_SCOPE":"system","_UID":"1001","__MONOTONIC_TIMESTAMP":"3277010798","_TRANSPORT":"stdout","_SYSTEMD_UNIT":"radicle-ci-broker.service","_SYSTEMD_SLICE":"system.slice","_SELINUX_CONTEXT":"unconfined\n","MESSAGE":"{\"timestamp\":\"2024-12-12T07:32:03.277600Z\",\"level\":\"TRACE\",\"fields\":{\"message\":\"event queue length\",\"msg_id\":\"QueueProcQueueLength\",\"kind\":\"debug\",\"len\":\"0\"}}","PRIORITY":"6","_SYSTEMD_CGROUP":"/system.slice/radicle-ci-broker.service","SYSLOG_IDENTIFIER":"cib","_STREAM_ID":"9c46f4f6f0074e07986a0c3769f6545e","_GID":"1001","__CURSOR":"s=f30566e7c34e4ba190c6c671ff826507;i=31363;b=da4ba18425ea4e34bd0f0731f0270572;m=c353376e;t=6290db5e53fd6;x=f0840763406ccc13","_HOSTNAME":"radicle-ci","_CMDLINE":"/bin/cib --log-level trace --config /home/_rad/ci-broker.yaml process-events","_BOOT_ID":"da4ba18425ea4e34bd0f0731f0270572"}

{"_SYSTEMD_UNIT":"radicle-ci-broker.service","_SYSTEMD_CGROUP":"/system.slice/radicle-ci-broker.service","__CURSOR":"s=f30566e7c34e4ba190c6c671ff826507;i=31364;b=da4ba18425ea4e34bd0f0731f0270572;m=c3627c05;t=6290db5f4846c;x=5bded561567c656f","MESSAGE":"{\"timestamp\":\"2024-12-12T07:32:04.278174Z\",\"level\":\"TRACE\",\"fields\":{\"message\":\"event queue length\",\"msg_id\":\"QueueProcQueueLength\",\"kind\":\"debug\",\"len\":\"0\"}}","_RUNTIME_SCOPE":"system","_HOSTNAME":"radicle-ci","_GID":"1001","PRIORITY":"6","_SELINUX_CONTEXT":"unconfined\n","_BOOT_ID":"da4ba18425ea4e34bd0f0731f0270572","__MONOTONIC_TIMESTAMP":"3278011397","_UID":"1001","_CMDLINE":"/bin/cib --log-level trace --config /home/_rad/ci-broker.yaml process-events","_SYSTEMD_INVOCATION_ID":"949b57247eb24bb5aefcec93f049beab","SYSLOG_IDENTIFIER":"cib","_MACHINE_ID":"35c654cc069c402d8cb0b34b91f12e5e","_TRANSPORT":"stdout","_PID":"526","_COMM":"cib","__REALTIME_TIMESTAMP":"1733988724278380","SYSLOG_FACILITY":"3","_CAP_EFFECTIVE":"0","_SYSTEMD_SLICE":"system.slice","_EXE":"/usr/bin/cib","_STREAM_ID":"9c46f4f6f0074e07986a0c3769f6545e"}

{"PRIORITY":"6","SYSLOG_FACILITY":"3","_STREAM_ID":"9c46f4f6f0074e07986a0c3769f6545e","_TRANSPORT":"stdout","_SYSTEMD_INVOCATION_ID":"949b57247eb24bb5aefcec93f049beab","_GID":"1001","__REALTIME_TIMESTAMP":"1733988725278778","MESSAGE":"{\"timestamp\":\"2024-12-12T07:32:05.278657Z\",\"level\":\"TRACE\",\"fields\":{\"message\":\"event queue length\",\"msg_id\":\"QueueProcQueueLength\",\"kind\":\"debug\",\"len\":\"0\"}}","_PID":"526","_CMDLINE":"/bin/cib --log-level trace --config /home/_rad/ci-broker.yaml process-events","_SYSTEMD_UNIT":"radicle-ci-broker.service","_EXE":"/usr/bin/cib","_MACHINE_ID":"35c654cc069c402d8cb0b34b91f12e5e","SYSLOG_IDENTIFIER":"cib","_HOSTNAME":"radicle-ci","_COMM":"cib","_SYSTEMD_SLICE":"system.slice","__MONOTONIC_TIMESTAMP":"3279011794","_RUNTIME_SCOPE":"system","_UID":"1001","_BOOT_ID":"da4ba18425ea4e34bd0f0731f0270572","_SYSTEMD_CGROUP":"/system.slice/radicle-ci-broker.service","__CURSOR":"s=f30566e7c34e4ba190c6c671ff826507;i=31367;b=da4ba18425ea4e34bd0f0731f0270572;m=c371bfd2;t=6290db603c83a;x=b50947c211c1edcb","_SELINUX_CONTEXT":"unconfined\n","_CAP_EFFECTIVE":"0"}

{"SYSLOG_IDENTIFIER":"cib","_BOOT_ID":"da4ba18425ea4e34bd0f0731f0270572","_TRANSPORT":"stdout","_PID":"526","PRIORITY":"6","_SYSTEMD_INVOCATION_ID":"949b57247eb24bb5aefcec93f049beab","_GID":"1001","_SYSTEMD_SLICE":"system.slice","__REALTIME_TIMESTAMP":"1733988726279175","_STREAM_ID":"9c46f4f6f0074e07986a0c3769f6545e","_COMM":"cib","__CURSOR":"s=f30566e7c34e4ba190c6c671ff826507;i=31368;b=da4ba18425ea4e34bd0f0731f0270572;m=c381039f;t=6290db6130c07;x=7b8169758b14d38c","_SELINUX_CONTEXT":"unconfined\n","_RUNTIME_SCOPE":"system","_EXE":"/usr/bin/cib","_CAP_EFFECTIVE":"0","MESSAGE":"{\"timestamp\":\"2024-12-12T07:32:06.279078Z\",\"level\":\"TRACE\",\"fields\":{\"message\":\"event queue length\",\"msg_id\":\"QueueProcQueueLength\",\"kind\":\"debug\",\"len\":\"0\"}}","_HOSTNAME":"radicle-ci","_MACHINE_ID":"35c654cc069c402d8cb0b34b91f12e5e","_SYSTEMD_UNIT":"radicle-ci-broker.service","SYSLOG_FACILITY":"3","_UID":"1001","_CMDLINE":"/bin/cib --log-level trace --config /home/_rad/ci-broker.yaml process-events","_SYSTEMD_CGROUP":"/system.slice/radicle-ci-broker.service","__MONOTONIC_TIMESTAMP":"3280012191"}

{"MESSAGE":"{\"timestamp\":\"2024-12-12T07:32:07.279440Z\",\"level\":\"TRACE\",\"fields\":{\"message\":\"event queue length\",\"msg_id\":\"QueueProcQueueLength\",\"kind\":\"debug\",\"len\":\"0\"}}","_STREAM_ID":"9c46f4f6f0074e07986a0c3769f6545e","_EXE":"/usr/bin/cib","_RUNTIME_SCOPE":"system","_TRANSPORT":"stdout","_SYSTEMD_INVOCATION_ID":"949b57247eb24bb5aefcec93f049beab","_SELINUX_CONTEXT":"unconfined\n","_CMDLINE":"/bin/cib --log-level trace --config /home/_rad/ci-broker.yaml process-events","_PID":"526","_HOSTNAME":"radicle-ci","_MACHINE_ID":"35c654cc069c402d8cb0b34b91f12e5e","__REALTIME_TIMESTAMP":"1733988727279541","_SYSTEMD_UNIT":"radicle-ci-broker.service","PRIORITY":"6","_GID":"1001","_UID":"1001","SYSLOG_FACILITY":"3","_COMM":"cib","SYSLOG_IDENTIFIER":"cib","__CURSOR":"s=f30566e7c34e4ba190c6c671ff826507;i=31369;b=da4ba18425ea4e34bd0f0731f0270572;m=c390474d;t=6290db6224fb5;x=faafb09a153285ff","_BOOT_ID":"da4ba18425ea4e34bd0f0731f0270572","_SYSTEMD_CGROUP":"/system.slice/radicle-ci-broker.service","_CAP_EFFECTIVE":"0","_SYSTEMD_SLICE":"system.slice","__MONOTONIC_TIMESTAMP":"3281012557"}

{"_PID":"526","_CMDLINE":"/bin/cib --log-level trace --config /home/_rad/ci-broker.yaml process-events","_SYSTEMD_CGROUP":"/system.slice/radicle-ci-broker.service","_HOSTNAME":"radicle-ci","__MONOTONIC_TIMESTAMP":"3282012856","_MACHINE_ID":"35c654cc069c402d8cb0b34b91f12e5e","_TRANSPORT":"stdout","SYSLOG_IDENTIFIER":"cib","_SYSTEMD_SLICE":"system.slice","_COMM":"cib","_CAP_EFFECTIVE":"0","_SELINUX_CONTEXT":"unconfined\n","__REALTIME_TIMESTAMP":"1733988728279841","_SYSTEMD_UNIT":"radicle-ci-broker.service","_SYSTEMD_INVOCATION_ID":"949b57247eb24bb5aefcec93f049beab","_STREAM_ID":"9c46f4f6f0074e07986a0c3769f6545e","_BOOT_ID":"da4ba18425ea4e34bd0f0731f0270572","_GID":"1001","SYSLOG_FACILITY":"3","__CURSOR":"s=f30566e7c34e4ba190c6c671ff826507;i=3136a;b=da4ba18425ea4e34bd0f0731f0270572;m=c39f8ab8;t=6290db6319321;x=d04fd63cc7903199","PRIORITY":"6","_EXE":"/usr/bin/cib","MESSAGE":"{\"timestamp\":\"2024-12-12T07:32:08.279755Z\",\"level\":\"TRACE\",\"fields\":{\"message\":\"event queue length\",\"msg_id\":\"QueueProcQueueLength\",\"kind\":\"debug\",\"len\":\"0\"}}","_RUNTIME_SCOPE":"system","_UID":"1001"}

{"MESSAGE":"{\"timestamp\":\"2024-12-12T07:32:09.280049Z\",\"level\":\"TRACE\",\"fields\":{\"message\":\"event queue length\",\"msg_id\":\"QueueProcQueueLength\",\"kind\":\"debug\",\"len\":\"0\"}}","_UID":"1001","_CMDLINE":"/bin/cib --log-level trace --config /home/_rad/ci-broker.yaml process-events","_HOSTNAME":"radicle-ci","_PID":"526","_TRANSPORT":"stdout","__REALTIME_TIMESTAMP":"1733988729280146","_SELINUX_CONTEXT":"unconfined\n","_SYSTEMD_CGROUP":"/system.slice/radicle-ci-broker.service","_RUNTIME_SCOPE":"system","_MACHINE_ID":"35c654cc069c402d8cb0b34b91f12e5e","_GID":"1001","PRIORITY":"6","_BOOT_ID":"da4ba18425ea4e34bd0f0731f0270572","_STREAM_ID":"9c46f4f6f0074e07986a0c3769f6545e","_CAP_EFFECTIVE":"0","_SYSTEMD_UNIT":"radicle-ci-broker.service","_EXE":"/usr/bin/cib","SYSLOG_IDENTIFIER":"cib","_COMM":"cib","_SYSTEMD_INVOCATION_ID":"949b57247eb24bb5aefcec93f049beab","_SYSTEMD_SLICE":"system.slice","SYSLOG_FACILITY":"3","__CURSOR":"s=f30566e7c34e4ba190c6c671ff826507;i=3136b;b=da4ba18425ea4e34bd0f0731f0270572;m=c3aece29;t=6290db640d692;x=b38aefb25148da02","__MONOTONIC_TIMESTAMP":"3283013161"}

{"__MONOTONIC_TIMESTAMP":"1284501864","_PID":"526","__REALTIME_TIMESTAMP":"1733986730768848","_EXE":"/usr/bin/cib","__CURSOR":"s=f30566e7c34e4ba190c6c671ff826507;i=2d8f2;b=da4ba18425ea4e34bd0f0731f0270572;m=4c8ff168;t=6290d3f21f9d0;x=d9b8c7ef2053cc0f","_SYSTEMD_CGROUP":"/system.slice/radicle-ci-broker.service","_CAP_EFFECTIVE":"0","_SYSTEMD_SLICE":"system.slice","_SELINUX_CONTEXT":"unconfined\n","_CMDLINE":"/bin/cib --log-level trace --config /home/_rad/ci-broker.yaml process-events","_UID":"1001","SYSLOG_IDENTIFIER":"cib","_RUNTIME_SCOPE":"system","_BOOT_ID":"da4ba18425ea4e34bd0f0731f0270572","_MACHINE_ID":"35c654cc069c402d8cb0b34b91f12e5e","_SYSTEMD_UNIT":"radicle-ci-broker.service","_SYSTEMD_INVOCATION_ID":"949b57247eb24bb5aefcec93f049beab","SYSLOG_FACILITY":"3","_COMM":"cib","_STREAM_ID":"9c46f4f6f0074e07986a0c3769f6545e","_HOSTNAME":"radicle-ci","_GID":"1001","MESSAGE":"{\"timestamp\":\"2024-12-12T06:58:50.768787Z\",\"level\":\"INFO\",\"fields\":{\"message\":\"Finish CI run\",\"msg_id\":\"BrokerRunEnd\",\"kind\":\"finish_run\",\"run\":\"Run { broker_run_id: RunId { id: \\\"62c45727-a4d8-4a29-9dae-88c6e8b61655\\\" }, adapter_run_id: Some(RunId { id: \\\"fa233c62-51df-4812-865c-7b989915c1f3\\\" }), adapter_info_url: Some(\\\"http://radicle-ci/fa233c62-51df-4812-865c-7b989915c1f3/log.html\\\"), repo_id: RepoId(rad:z3gqcJUoA1n9HaHKufZs5FCSGazv5), repo_name: \\\"heartwood\\\", timestamp: \\\"2024-12-12 06:58:03Z\\\", whence: Branch { name: \\\"master\\\", commit: Oid(d9c76893a144fd787654613f2bfb919613014a71), who: Some(\\\"did:key:z6MkiB8T5cBEQHnrs2MgjMVqvpSVj42X81HjKfFi2XBoMbtr (radicle-ci)\\\") }, state: Finished, result: Some(Failure) }\"},\"span\":{\"broker_run_id\":\"62c45727-a4d8-4a29-9dae-88c6e8b61655\",\"name\":\"execute_ci_run\"},\"spans\":[{\"broker_run_id\":\"62c45727-a4d8-4a29-9dae-88c6e8b61655\",\"name\":\"execute_ci_run\"}]}","_TRANSPORT":"stdout","PRIORITY":"6"}

~~~

    Log(cibtoolcmd::LogCmd),

            Self::Log(x) => x.run(args),

    #[error(transparent)]

    Log(#[from] cibtoolcmd::LogError),

use std::{

    convert::TryFrom,

    fs::{read, File},

    io::{Read, Write},

    path::{Path, PathBuf},

};

use logger::LogLevel;

use serde::Deserialize;

use serde_json::{Map, Value};

use super::*;

/// Format Radicle CI broker log files in a pretty way.

///

/// The journald output must be provided in the format produced by

/// `journalctl -u radicle-ci-broker -o json` (possibly with options

/// such as `-u radicle-ci-broker` or `-S today`), and not in ah the

/// default text format that's hard to parse.

#[derive(Debug, Parser)]

pub struct LogCmd {

    /// Read journalctl JSON output from this file. repository name.

    /// Default is to read from the standard input.

    #[clap(long)]

    journal: Option<PathBuf>,

    /// Include messages only if they are at least of this log level.

    /// Default is to allow any log level.

    #[clap(long)]

    log_level: Option<crate::logger::LogLevel>,

    /// Include messages only if they have this message kind. Can be

    /// used multiple times, and any of the kinds will do. Default is

    /// to allow every kind of message.

    #[clap(long)]

    kind: Vec<logger::Kind>,

    /// Include messages only if they relate to this CI run. The run

    /// ID is the broker run id. Default is to allow every CI run, and

    /// messages not related to a specific CI run.

    #[clap(long)]

    broker_run_id: Option<RunId>,

    /// Write output to this file. Default is to write to the standard

    /// output.

    #[clap(long)]

    output: Option<PathBuf>,

}

#[allow(clippy::unwrap_used)]

impl LogCmd {

    fn allowed(&self, msg: &Value) -> bool {

        self.allowed_by_log_level(msg)

            && self.allowed_by_kind(msg)

            && self.allowed_by_broker_run_id(msg)

    }

    fn allowed_by_log_level(&self, msg: &Value) -> bool {

        if let Some(wanted) = &self.log_level {

            if let Some(actual) = log_level(msg) {

                return actual >= *wanted;

            }

        }

        true

    }

    fn allowed_by_kind(&self, msg: &Value) -> bool {

        if !self.kind.is_empty() {

            if let Some(actual) = kind(msg) {

                if !self.kind.iter().any(|wanted| *wanted == actual) {

                    return false;

                }

            } else {

                return false;

            }

        }

        true

    }

    fn allowed_by_broker_run_id(&self, msg: &Value) -> bool {

        if let Some(wanted) = &self.broker_run_id {

            if let Some(actual) = broker_run_id(msg) {

                return actual == *wanted;

            } else {

                return false;

            }

        }

        true

    }

}

fn log_level(msg: &Value) -> Option<LogLevel> {

    map_get(msg, "level").map(|v| LogLevel::try_from(v).ok())?

}

fn kind(msg: &Value) -> Option<logger::Kind> {

    let fields = map_get(msg, "fields")?;

    map_get(&fields, "kind").map(|v| logger::Kind::try_from(v).ok())?

}

fn broker_run_id(msg: &Value) -> Option<RunId> {

    let span = map_get(msg, "span")?;

    map_get(&span, "broker_run_id").map(|v| RunId::try_from(v).ok())?

}

fn map_get(v: &Value, key: &str) -> Option<Value> {

    if let Value::Object(map) = v {

        map.get(key).cloned()

    } else {

        None

    }

}

fn pretty(msg: Value) -> Result<String, LogError> {

    serde_json::to_string_pretty(&msg).map_err(|err| LogError::JsonSer(msg, err))

}

impl Leaf for LogCmd {

    fn run(&self, _args: &Args) -> Result<(), CibToolError> {

        let journal = if let Some(filename) = &self.journal {

            JournalLines::from_file(filename)?

        } else {

            JournalLines::from_stdin()?

        };

        let messages = journal.flatten().filter(|msg| self.allowed(msg));

        if let Some(filename) = &self.output {

            let mut file = File::create(filename)

                .map_err(|err| LogError::CreateOutput(filename.into(), err))?;

            for msg in messages {

                file.write_all(format!("{}\n", pretty(msg)?).as_bytes())

                    .map_err(|err| LogError::WriteOutput(filename.into(), err))?;

            }

        } else {

            for msg in messages {

                println!("{}", pretty(msg)?);

            }

        }

        Ok(())

    }

}

struct JournalLines {

    data: Vec<u8>,

    next: usize,

}

impl JournalLines {

    fn from_file(filename: &Path) -> Result<Self, LogError> {

        let data = read(filename).map_err(|err| LogError::Read(filename.into(), err))?;

        Ok(Self { data, next: 0 })

    }

    fn from_stdin() -> Result<Self, LogError> {

        let mut data = vec![];

        std::io::stdin()

            .read_to_end(&mut data)

            .map_err(LogError::ReadStdin)?;

        Ok(Self { data, next: 0 })

    }

}

impl Iterator for JournalLines {

    type Item = Result<serde_json::Value, LogError>;

    fn next(&mut self) -> Option<Self::Item> {

        let mut i = self.next;

        while i < self.data.len() {

            if self.data.get(i) == Some(&b'\n') {

                let line = String::from_utf8_lossy(&self.data[self.next..i]).to_string();

                self.next = i + 1;

                match serde_json::from_str::<JournalJson>(&line) {

                    Err(err) => return Some(Err(LogError::JsonParseJournal(line, err))),

                    Ok(jj) => match serde_json::from_str(&jj.message) {

                        Err(err) => return Some(Err(LogError::JsonParse(line, err))),

                        Ok(value) => return Some(Ok(value)),

                    },

                }

            }

            i += 1;

        }

        None

    }

}

#[derive(Debug, Deserialize)]

struct JournalJson {

    #[serde(rename = "MESSAGE")]

    message: String,

}

#[derive(Debug, thiserror::Error)]

pub enum LogError {

    #[error("failed to read journal file {0}")]

    Read(PathBuf, #[source] std::io::Error),

    #[error("failed to read journal file from the standard input")]

    ReadStdin(#[source] std::io::Error),

    #[error("failed to parse a journald log line as JSON: {0:?}")]

    JsonParseJournal(String, #[source] serde_json::Error),

    #[error("failed to parse a log line as JSON: {0:?}")]

    JsonParse(String, #[source] serde_json::Error),

    #[error("failed to serialize a log line as pretty JSON: {0:?}")]

    JsonSer(serde_json::Value, #[source] serde_json::Error),

    #[error("failed to create output file {0}")]

    CreateOutput(PathBuf, #[source] std::io::Error),

    #[error("failed to write to output file {0}")]

    WriteOutput(PathBuf, #[source] std::io::Error),

}

mod log;

pub use log::*;

use serde_json::Value;

#[derive(Debug, thiserror::Error)]

pub enum KindError {

    #[error("unknown log message kind {0:?}")]

    Unknown(String),

    #[error("unknown log message kind {0:?}")]

    UnknownValue(Value),

}

/// A unique type or kind for each log message.

#[derive(Debug, Clone, ValueEnum, Eq, PartialEq)]

pub enum Kind {

impl TryFrom<&str> for Kind {

    type Error = KindError;

    fn try_from(value: &str) -> Result<Self, Self::Error> {

        match value {

            "debug" => Ok(Self::Debug),

            "startup" => Ok(Self::Startup),

            "shutdown" => Ok(Self::Shutdown),

            "got_event" => Ok(Self::GotEvent),

            "start_run" => Ok(Self::StartRun),

            "finish_run" => Ok(Self::FinishRun),

            "adapter_message" => Ok(Self::AdapterMessage),

            _ => Err(KindError::Unknown(value.into())),

        }

    }

}

impl TryFrom<Value> for Kind {

    type Error = KindError;

    fn try_from(value: Value) -> Result<Self, Self::Error> {

        match value {

            Value::String(s) => match s.as_str() {

                "debug" => Ok(Self::Debug),

                "startup" => Ok(Self::Startup),

                "shutdown" => Ok(Self::Shutdown),

                "got_event" => Ok(Self::GotEvent),

                "start_run" => Ok(Self::StartRun),

                "finish_run" => Ok(Self::FinishRun),

                "adapter_message" => Ok(Self::AdapterMessage),

                _ => Err(KindError::Unknown(s)),

            },

            _ => Err(KindError::UnknownValue(value)),

        }

    }

}

#[derive(Debug, thiserror::Error)]

pub enum LogLevelError {

    #[error("unknown log level {0}")]

    UnknownLogLevel(String),

    #[error("unknown log level {0:?}")]

    UnknownLogLevelValue(Value),

}

#[derive(ValueEnum, Ord, PartialOrd, Eq, PartialEq, Copy, Clone, Debug)]

impl TryFrom<&str> for LogLevel {

    type Error = LogLevelError;

    fn try_from(s: &str) -> Result<Self, LogLevelError> {

        match s {

            "TRACE" => Ok(Self::Trace),

            "DEBUG" => Ok(Self::Debug),

            "INFO" => Ok(Self::Info),

            "WARNING" => Ok(Self::Warning),

            "ERROR" => Ok(Self::Error),

            _ => Err(LogLevelError::UnknownLogLevel(s.into())),

        }

    }

}

impl TryFrom<String> for LogLevel {

    type Error = LogLevelError;

    fn try_from(s: String) -> Result<Self, LogLevelError> {

        Self::try_from(s.as_str())

    }

}

impl TryFrom<&Value> for LogLevel {

    type Error = LogLevelError;

    fn try_from(v: &Value) -> Result<Self, LogLevelError> {

        match v {

            Value::String(s) => Self::try_from(s.as_str()),

            _ => Err(LogLevelError::UnknownLogLevelValue(v.clone())),

        }

    }

}

impl TryFrom<Value> for LogLevel {

    type Error = LogLevelError;

    fn try_from(v: Value) -> Result<Self, LogLevelError> {

        Self::try_from(&v)

    }

}

use serde_json::Value;

impl TryFrom<Value> for RunId {

    type Error = ();

    fn try_from(id: Value) -> Result<Self, Self::Error> {

        match id {

            Value::String(s) => Ok(Self::from(s.as_str())),

            _ => Err(()),

        }

    }

}