allow using custom date format

README.md

@@ -18,6 +18,19 @@ logsmash ./logfile.log
 Logsmash supports both loading plain log files, compressed log files (`.gz`, `.bz2`, `.xz` or `.zst`), or archives
 containing log files (`.zip` or (compressed) `.tar`).
 
+### Date formats
+
+Since not all log files use the same date format, logsmash tries to parse each data with a number of different log
+formats.
+
+If the log file you're opening is using an unsupported log format, you can specify a custom date format with the
+`--date-format` option.
+
+The data format can either be in [the strftime format](https://man7.org/linux/man-pages/man3/strftime.3.html) or
+in [the time crate format (version 2)](https://time-rs.github.io/book/api/format-description.html).
+
+For example: `[day].[month].[year] - [hour]:[minute]:[second]`.
+
 ## Log sources
 
 Logsmash is built around matching log line to their source, either a call to a logging function or an exception being

src/logline.rs

@@ -6,8 +6,10 @@ use serde_json::Value;
 use std::borrow::Cow;
 use std::fmt::{Display, Formatter};
 use std::hash::{Hash, Hasher};
+use std::sync::OnceLock;
 use time::format_description::well_known::iso8601::{Config, EncodedConfig, TimePrecision};
 use time::format_description::well_known::Iso8601;
+use time::format_description::OwnedFormatItem;
 use time::OffsetDateTime;
 use tinystr::TinyAsciiStr;
 
@@ -17,6 +19,9 @@ pub const TIME_FORMAT: EncodedConfig = Config::DEFAULT
     })
     .encode();
 
+// ugly global because passing state to serde is hard
+pub static CUSTOM_TIME_FORMAT: OnceLock<Option<OwnedFormatItem>> = OnceLock::new();
+
 #[derive(Deserialize, Clone)]
 pub struct LogLine<'a> {
     #[serde(default)]
@@ -38,6 +43,7 @@ pub struct LogLine<'a> {
 }
 
 mod date {
+    use crate::logline::CUSTOM_TIME_FORMAT;
     use serde::de::Error;
     use serde::{Deserialize, Deserializer};
     use time::format_description::well_known::Iso8601;
@@ -70,6 +76,12 @@ mod date {
     ) -> Result<OffsetDateTime, D::Error> {
         let str = <&str>::deserialize(deserializer)?;
 
+        if let Some(Some(format)) = CUSTOM_TIME_FORMAT.get() {
+            if let Some(date) = try_format(str, format) {
+                return Ok(date);
+            }
+        }
+
         if let Some(date) = try_format(str, &Iso8601::DATE_TIME_OFFSET) {
             return Ok(date);
         }

src/main.rs

@@ -1,7 +1,7 @@
 use crate::app::{App, LogMatch};
 use crate::error::LogError;
 use crate::logfile::LogFile;
-use crate::logline::{Exception, FullException, FullLogLine, LogLine};
+use crate::logline::{Exception, FullException, FullLogLine, LogLine, CUSTOM_TIME_FORMAT};
 use crate::matcher::{MatchResult, Matcher};
 use crate::ui::run_ui;
 use base64::prelude::*;
@@ -26,6 +26,7 @@ mod ui;
 
 #[cfg(not(target_os = "windows"))]
 use tikv_jemallocator::Jemalloc;
+use time::format_description::{parse_owned, parse_strftime_owned};
 
 #[cfg(not(target_os = "windows"))]
 #[global_allocator]
@@ -37,11 +38,28 @@ struct Args {
     /// Collect data and exit, intended for profiling
     #[arg(long)]
     profile: bool,
+    /// Date format to use when parsing log lines
+    #[arg(long)]
+    date_format: Option<String>,
 }
 
 fn main() -> MainResult {
     let args = Args::parse();
 
+    if let Some(date_format) = args.date_format.as_deref() {
+        let date_format = if date_format.contains('%') {
+            parse_strftime_owned(date_format)
+                .inspect_err(|_| eprintln!("Invalid strftime format: {date_format}"))?
+        } else {
+            parse_owned::<2>(date_format)
+                .inspect_err(|_| eprintln!("Invalid date format: {date_format}"))?
+        };
+
+        CUSTOM_TIME_FORMAT
+            .set(Some(date_format))
+            .expect("Set only once");
+    }
+
     let file = File::open(&args.file)?;
     let file = BufReader::new(file);
     let log_file = LogFile::open(&args.file, file).map_err(|err| LogError::Read {