Add invoice generator for fuel station transactions

- Read CSV files from input/ directory
- Generate static HTML invoices grouped by customer and card
- Filter transactions to only include fleet customers
- Compact print-friendly layout with 2 decimal precision

src/invoice_generator.rs

@@ -0,0 +1,126 @@
+use chrono::NaiveDateTime;
+use csv::ReaderBuilder;
+use std::collections::BTreeMap;
+use std::fs;
+use std::path::Path;
+
+#[derive(Debug, Clone)]
+pub struct Transaction {
+    pub date: NaiveDateTime,
+    pub batch_number: String,
+    pub amount: f64,
+    pub volume: f64,
+    pub price: f64,
+    pub quality: i32,
+    pub quality_name: String,
+    pub card_number: String,
+    pub card_type: String,
+    pub customer_number: String,
+    pub station: String,
+    pub terminal: String,
+    pub pump: String,
+    pub receipt: String,
+    pub card_report_group_number: String,
+    pub control_number: String,
+}
+
+#[derive(Debug, Clone)]
+pub struct Batch {
+    pub filename: String,
+    pub transactions: Vec<Transaction>,
+}
+
+#[derive(Debug, Clone)]
+pub struct Customer {
+    pub customer_number: String,
+    pub cards: BTreeMap<String, Vec<Transaction>>,
+}
+
+fn get_field(record: &csv::StringRecord, index: usize) -> &str {
+    record.get(index).unwrap_or("")
+}
+
+impl Transaction {
+    pub fn from_record(record: &csv::StringRecord) -> Option<Self> {
+        let date_str = get_field(record, 0);
+        let date = NaiveDateTime::parse_from_str(date_str, "%Y-%m-%d %H:%M:%S").ok()?;
+
+        Some(Transaction {
+            date,
+            batch_number: get_field(record, 1).to_string(),
+            amount: get_field(record, 2).parse().unwrap_or(0.0),
+            volume: get_field(record, 3).parse().unwrap_or(0.0),
+            price: get_field(record, 4).parse().unwrap_or(0.0),
+            quality: get_field(record, 5).parse().unwrap_or(0),
+            quality_name: get_field(record, 6).to_string(),
+            card_number: get_field(record, 7).to_string(),
+            card_type: get_field(record, 8).to_string(),
+            customer_number: get_field(record, 9).to_string(),
+            station: get_field(record, 10).to_string(),
+            terminal: get_field(record, 11).to_string(),
+            pump: get_field(record, 12).to_string(),
+            receipt: get_field(record, 13).to_string(),
+            card_report_group_number: get_field(record, 14).to_string(),
+            control_number: get_field(record, 15).to_string(),
+        })
+    }
+}
+
+pub fn read_csv_file(path: &Path) -> Result<Batch, Box<dyn std::error::Error>> {
+    let filename = path
+        .file_name()
+        .and_then(|n| n.to_str())
+        .unwrap_or("unknown")
+        .to_string();
+
+    let file = fs::File::open(path)?;
+    let mut rdr = ReaderBuilder::new()
+        .delimiter(b'\t')
+        .has_headers(true)
+        .flexible(true)
+        .from_reader(file);
+
+    let mut transactions = Vec::new();
+
+    for result in rdr.records() {
+        let record = result?;
+        if let Some(tx) = Transaction::from_record(&record) {
+            if tx.amount > 0.0 && !tx.customer_number.is_empty() {
+                transactions.push(tx);
+            }
+        }
+    }
+
+    transactions.sort_by(|a, b| a.date.cmp(&b.date));
+
+    Ok(Batch {
+        filename,
+        transactions,
+    })
+}
+
+pub fn group_by_customer(batches: &[Batch]) -> BTreeMap<String, Customer> {
+    let mut customers: BTreeMap<String, Customer> = BTreeMap::new();
+
+    for batch in batches {
+        for tx in &batch.transactions {
+            let customer = customers
+                .entry(tx.customer_number.clone())
+                .or_insert_with(|| Customer {
+                    customer_number: tx.customer_number.clone(),
+                    cards: BTreeMap::new(),
+                });
+
+            let card_txs = customer.cards.entry(tx.card_number.clone()).or_default();
+            card_txs.push(tx.clone());
+        }
+    }
+
+    for customer in customers.values_mut() {
+        for card_txs in customer.cards.values_mut() {
+            card_txs.sort_by(|a, b| a.date.cmp(&b.date));
+        }
+    }
+
+    customers
+}