Accept CSV file path as command line argument

Output is now written to the same directory as the input file.

src/main.rs

@@ -1,11 +1,12 @@
 use askama::Template;
 use chrono::Utc;
+use std::env;
 use std::fs;
 use std::path::Path;
 
 mod invoice_generator;
 
-use invoice_generator::{group_by_customer, read_csv_file, Batch, Customer};
+use invoice_generator::{group_by_customer, read_csv_file, Customer};
 
 fn fmt(v: f64) -> String {
     format!("{:.2}", v)
@@ -101,40 +102,35 @@ struct CustomerTemplate {
 }
 
 fn main() -> Result<(), Box<dyn std::error::Error>> {
-    let data_dir = Path::new("input");
-    let output_dir = Path::new("output");
+    let args: Vec<String> = env::args().collect();
+
+    if args.len() != 2 {
+        eprintln!("Usage: {} <csv-file>", args[0]);
+        std::process::exit(1);
+    }
+
+    let input_path = Path::new(&args[1]);
+
+    if !input_path.exists() {
+        eprintln!("Error: File not found: {:?}", input_path);
+        std::process::exit(1);
+    }
+
+    let output_dir = input_path.parent().unwrap_or(Path::new("."));
 
     if !output_dir.exists() {
         fs::create_dir_all(output_dir)?;
     }
 
-    let mut batches: Vec<Batch> = Vec::new();
+    let batch = read_csv_file(input_path)?;
+    println!(
+        "Loaded {} transactions from {}",
+        batch.transactions.len(),
+        batch.filename
+    );
 
-    for entry in fs::read_dir(data_dir)? {
-        let entry = entry?;
-        let path = entry.path();
-        if path.extension().and_then(|s| s.to_str()) == Some("csv") {
-            match read_csv_file(&path) {
-                Ok(batch) => {
-                    println!(
-                        "Loaded {} transactions from {}",
-                        batch.transactions.len(),
-                        batch.filename
-                    );
-                    batches.push(batch);
-                }
-                Err(e) => {
-                    eprintln!("Error reading {:?}: {}", path, e);
-                }
-            }
-        }
-    }
-
-    batches.sort_by(|a, b| a.filename.cmp(&b.filename));
-
-    let batch_filenames: Vec<String> = batches.iter().map(|b| b.filename.clone()).collect();
-
-    let customers = group_by_customer(&batches);
+    let batch_filename = batch.filename.clone();
+    let customers = group_by_customer(&[batch]);
 
     let index_customers: Vec<(String, usize)> = customers
         .iter()
@@ -142,8 +138,8 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
         .collect();
 
     let html = IndexTemplate {
-        customers: index_customers,
-        batches: batch_filenames.clone(),
+        customers: index_customers.clone(),
+        batches: vec![batch_filename.clone()],
     }
     .render()
     .unwrap();
@@ -156,7 +152,7 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
         let prepared = PreparedCustomer::from_customer(customer);
         let customer_html = CustomerTemplate {
             customer: prepared,
-            batches: batch_filenames.clone(),
+            batches: vec![batch_filename.clone()],
             generated_date: generated_date.clone(),
         }
         .render()
@@ -167,8 +163,8 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
     }
 
     println!(
-        "\nGenerated {} customer invoices in output/",
-        customer_count
+        "\nGenerated {} customer invoices in {:?}",
+        customer_count, output_dir
     );
 
     Ok(())