2 files changed, 33 insertions, 13 deletions

diff --git a/src/fexpr/mod.rs b/src/fexpr/mod.rs
index 5754d94..5610aba 100644
--- a/src/fexpr/mod.rs
+++ b/src/fexpr/mod.rs
@@ -46,9 +46,9 @@ pub enum FErrorKind {
 }
 
 /// Shortcut to create a new parser and parse the given input.
-pub fn parse_logfilter(
-    input: &str,
-) -> Result<Box<dyn filters::log::LogFilter>, ParseError<usize, Token, FError>> {
+pub fn parse_logfilter<'a>(
+    input: &'a str,
+) -> Result<Box<dyn filters::log::LogFilter>, ParseError<usize, Token<'a>, FError>> {
     grammar::LogFilterParser::new().parse(input)
 }
 
diff --git a/src/main.rs b/src/main.rs
index 2e0c82f..ff882e5 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -2,7 +2,7 @@
 use std::collections::HashMap;
 use std::fmt;
 use std::fs::File;
-use std::io::{BufReader, Read, Seek};
+use std::io::{BufReader, Read, Seek, Write};
 use std::path::PathBuf;
 use std::str::FromStr;
 
@@ -58,6 +58,10 @@ pub struct Opt {
     #[structopt(long = "guilds")]
     guilds: bool,
 
+    /// Run the REPL.
+    #[structopt(long)]
+    repl: bool,
+
     /// The filter expression.
     expression: Vec<String>,
 }
@@ -211,9 +215,13 @@ fn run() -> Result<()> {
         guilds::prepare_cache();
     }
 
-    let filter = build_filter(&opt)?;
-
-    grep(&opt, &*filter)?;
+    if !opt.repl {
+        let expr_string = opt.expression.join(" ");
+        let filter = build_filter(&expr_string)?;
+        grep(&opt, &*filter)?;
+    } else {
+        repl(&opt)?;
+    }
 
     if opt.guilds {
         guilds::save_cache();
@@ -222,6 +230,22 @@ fn run() -> Result<()> {
     Ok(())
 }
 
+fn repl(opt: &Opt) -> Result<()> {
+    let stdin = std::io::stdin();
+    loop {
+        print!("Query> ");
+        std::io::stdout().flush()?;
+        let mut line = String::new();
+        stdin.read_line(&mut line)?;
+        let line = line.trim();
+        let parsed = build_filter(&line);
+        match parsed {
+            Ok(filter) => grep(&opt, &*filter)?,
+            Err(err) => display_error(&err.into()),
+        }
+    }
+}
+
 /// Check if the given entry represents a log file, based on the file name.
 fn is_log_file(entry: &DirEntry) -> bool {
     entry
@@ -231,12 +255,8 @@ fn is_log_file(entry: &DirEntry) -> bool {
         .unwrap_or(false)
 }
 
-fn build_filter(opt: &Opt) -> Result<Box<dyn LogFilter>> {
-    // Our error needs access to the string, so we make our lives easier by just leaking it into a
-    // 'static lifetime. Otherwise we'd need to build this string in main() and pass it in.
-    // We're fine with the small memory leak, as we're only dealing with a small string in a
-    // short-lived program.
-    let expr_string = Box::leak(Box::new(opt.expression.join(" ")));
+/// Small wrapper around `fexpr::parse_logfilter` to convert the returned `Err` to be `'static'.
+fn build_filter(expr_string: &str) -> Result<Box<dyn LogFilter>> {
     if expr_string.trim().is_empty() {
         return Err(anyhow!("Expected a filter to be given"));
     }