BDD-like description

README.md

@@ -6,7 +6,6 @@
 
 *Note: the app has only been used so far in a Linux environment. Windows support is dubious.*
 
-
 ### Install
 
 - Ensure you have Python 3.10> and `poetry` installed.
@@ -20,3 +19,37 @@ To use `xexe`, you will need to have credentials for the `xe.com` API. Specifica
 To set up your environment, you should create a `.env` file in the root of this repository. You can use the `.env-example` file as a reference. We also recommend running `chmod 400` or `chmod 600` on it for safety.
 
 Once you have done this, you can run `poetry run xexe xe-healthcheck`. If the connection to the API was successful, you will see some output telling you so.
+
+## Using
+
+You can use `xexe` to get rates and store them locally like this:
+
+```bash
+poetry run xexe get-rates --start-date "2024-01-01" --end-date "2024-01-10" --output my_rates.csv
+```
+
+You can also run without specifying dates. Not specifying `end-date` will get rates up to today. Not specifying `start-date` will get dates up to last week.
+
+```bash
+poetry run xexe get-rates --output my_rates.csv
+```
+
+`xexe` comes with a set of default currencies, but you can also specify the currencies you want to get data for by passing them like this:
+
+```bash
+# Currencies must be valid ISO 4217 codes and be comma-separated
+poetry run xexe get-rates --currencies USD,EUR,GBP --output my_rates.csv
+```
+
+The output file will follow this schema:
+
+- `date`
+- `from_currency`
+- `to_currency`
+- `exchange_rate`
+- `exported_at`
+
+A few more details:
+
+- Running `get-rates` with an `end-date` beyond the current date will ignore the future dates. The run will behave as if you had specified today as the `end-date`.
+- Any run that requires more than 1,000 API calls will prompt the user for confirmation. We do this to avoid accidentally running massive exports against the API due to human errors, since we have a monthly cap on the usage of xe.com's API.