Perspective

src/main.rs

@@ -1,13 +1,14 @@
 use clap::Parser as _;
+use core::error;
 use ecb_rates::cache::{Cache, CacheLine};
-use reqwest::{Client, IntoUrl};
+use reqwest::{Client, IntoUrl, StatusCode};
 use std::process::ExitCode;
 
 use ecb_rates::cli::{Cli, FormatOption};
 use ecb_rates::models::ExchangeRateResult;
 use ecb_rates::parsing::parse;
 use ecb_rates::table::{TableRef, TableTrait as _};
-use ecb_rates::utils_calc::filter_currencies;
+use ecb_rates::utils_calc::{change_perspective, filter_currencies};
 
 async fn get_and_parse(url: impl IntoUrl) -> anyhow::Result<Vec<ExchangeRateResult>> {
     let client = Client::new();
@@ -72,6 +73,14 @@ async fn main() -> ExitCode {
         parsed
     };
 
+    if let Some(currency) = cli.perspective {
+        let error_occured = change_perspective(&mut parsed, &currency).is_none();
+        if error_occured {
+            eprintln!("The currency wasn't in the data from the ECB!");
+            return ExitCode::FAILURE;
+        }
+    }
+
     if !cli.currencies.is_empty() {
         let currencies = cli
             .currencies

src/table/table_display.rs

@@ -36,7 +36,7 @@ pub fn helper_table_print<T: TableGet>(
 
     for (left, right) in table.get_rows().iter() {
         let left_str = left.as_ref();
-        let right_str = right.to_string();
+        let right_str = format!("{:.5}", right);
         let padding_amount = width.saturating_sub(left_str.len() + right_str.len());
         let padding = " ".repeat(padding_amount);
         writeln!(f, "{}{}{}", left_str.bold().green(), padding, right_str)?;

src/utils_calc.rs

@@ -1,4 +1,4 @@
-use std::{borrow::BorrowMut, collections::HashMap};
+use std::{borrow::BorrowMut, collections::HashMap, ops::Deref};
 
 use crate::models::ExchangeRateResult;
 
@@ -19,3 +19,28 @@ pub fn filter_currencies(exchange_rate_results: &mut [ExchangeRateResult], curre
             });
     }
 }
+
+pub fn change_perspective(
+    exchange_rate_results: &mut [ExchangeRateResult],
+    currency: &str,
+) -> Option<()> {
+    for rate_res in exchange_rate_results {
+        let currency_rate = rate_res.rates.remove(currency)?;
+        let eur_rate = 1.0 / currency_rate;
+
+        for (_, iter_rate) in rate_res.rates.iter_mut() {
+            *iter_rate = eur_rate * iter_rate.deref();
+        }
+
+        rate_res.rates.insert("EUR".to_string(), eur_rate);
+    }
+    Some(())
+}
+
+pub fn invert_rates(exchange_rate_results: &mut [ExchangeRateResult]) {
+    for rate_res in exchange_rate_results {
+        for (_, iter_rate) in rate_res.rates.iter_mut() {
+            *iter_rate = 1.0 / *iter_rate;
+        }
+    }
+}