initial work on comparison based filters

This enables filters such as
    -time > 2020-01-01
    -time < 2020-02-03
    ...
for time and duration, and later possibly also for more things (such as
a COUNT(...) construct).

This work tries to integrate them into the existing filter system as
seamless as possible, by providing a Comparator which implements
LogFilter.

The "type checking" is done at parse time, so nonsensical comparisons
like -time > 12s flat out give a parse error. This however might be
changed to a more dynamic system with run-time type checking, in which
case we could do away with the type parameter on Producer and simply
work with a generic Value. The comparator would then return an error if
two non-identical types would be compared.

Note that the system does not support arithmetic expressions, only
simple comparisons to constant values.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/filters/log.rs b/src/filters/log.rs
index 8cfdcb4..9ca7d3c 100644
--- a/src/filters/log.rs
+++ b/src/filters/log.rs
@@ -137,7 +137,7 @@ fn time_is_between(
 ///
 /// This expects the filename to have the datetime in the pattern `YYYYmmdd-HHMMSS` somewhere in
 /// it.
-fn datetime_from_filename(name: &OsStr) -> Option<DateTime<Utc>> {
+pub(crate) fn datetime_from_filename(name: &OsStr) -> Option<DateTime<Utc>> {
     let date_match = DATE_REGEX.find(name.to_str()?)?;
     let local_time = Local
         .datetime_from_str(date_match.as_str(), "%Y%m%d-%H%M%S")