processor: implement CLI interface

src/bin/processor.rs

@@ -1,3 +1,40 @@
-fn main() {
-    println!("Hello, world!");
+use thiserror::Error;
+
+use processor::{Ledger, Transaction};
+
+/// Any kind of error in the pipeline CSV parsing -> payment processing -> final state output.
+#[derive(Debug, Error)]
+pub enum Error {
+    #[error("missing input file argument")]
+    MissingFile,
+    #[error("error during CSV processing: {0}")]
+    CsvError(#[from] csv::Error),
+}
+
+fn main() -> Result<(), Error> {
+    let mut ledger = Ledger::new();
+
+    let path = std::env::args_os()
+        // Skip argv[0]
+        .skip(1)
+        // Expect a file name here
+        .next()
+        .ok_or(Error::MissingFile)?;
+
+    for (tx, index) in Transaction::configured_csv_reader_builder()
+        .from_path(path)?
+        .into_deserialize()
+        .zip(1..)
+    {
+        match ledger.process(tx?) {
+            // All errors are logged but should not stop processing
+            Err(err) => eprintln!("error during processing: transaction {}: {}", index, err),
+            _ => {}
+        }
+    }
+
+    let mut writer = csv::Writer::from_writer(std::io::stdout());
+    ledger.dump_csv(&mut writer)?;
+
+    Ok(())
 }