149 lines
6 KiB
Rust
149 lines
6 KiB
Rust
/// This is an example to show fetching a file from a webiste and saving to a file
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///
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/// The example consts of:
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///
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/// - The main program, in `main()` - demonstrates how to setup `kxio` for use in prod
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/// - A test module - demonstrates how to use `kxio` in tests
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/// - sample functions - showing how to use `kxio` the body of your program, and be testable
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///
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/// NOTE: running this program with `cargo run --example get` will create and delete the file
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/// `example-readme.md` in the current directory.
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use std::path::Path;
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#[tokio::main]
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async fn main() -> kxio::Result<()> {
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// Create a `Net` object for making real network requests.
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let net: kxio::net::Net = kxio::net::new();
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// Create a `FileSystem` object for accessing files within the current directory.
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// The object created will return a `PathTraveral` error result if there is an attempt to\
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// access a file outside of this directory.
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let fs: kxio::fs::FileSystem = kxio::fs::new("./");
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// The URL we will fetch - the readme for this library.
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let url = "https://git.kemitix.net/kemitix/kxio/raw/branch/main/README.md";
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// Create a PathBuf to a file within the directory that the `fs` object has access to.
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let file_path = fs.base().join("example-readme.md");
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// Create a generic handle for the file. This doesn't open the file, and always succeeds.
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let path: kxio::fs::PathReal<kxio::fs::PathMarker> = fs.path(&file_path);
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// Other options are;
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// `fs.file(&file_path)` - for a file
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// `fs.dir(&dir_path)` - for a directory
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// Checks if the path exists (whether a file, directory, etc)
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if path.exists()? {
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// extracts the path from the handle
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let pathbuf = path.as_pathbuf();
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eprintln!("The file {} already exists. Aborting!", pathbuf.display());
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return Ok(());
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}
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// Passes a reference to the `fs` and `net` objects for use by your program.
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// Your programs should not know whether they are handling a mock or the real thing.
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// Any file or network access should be made using these handlers to be properly testable.
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download_and_save_to_file(url, &file_path, &fs, &net).await?;
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delete_file(&file_path, &fs)?;
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Ok(())
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}
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/// An function that uses a `FileSystem` and a `Net` object to interact with the outside world.
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async fn download_and_save_to_file(
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url: &str,
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file_path: &Path,
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// The file system abstraction
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fs: &kxio::fs::FileSystem,
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// The network abstraction
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net: &kxio::net::Net,
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) -> kxio::Result<()> {
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println!("fetching: {url}");
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// Uses the network abstraction to create a perfectly normal `reqwest::ResponseBuilder`.
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let request: reqwest::RequestBuilder = net.client().get(url);
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// Rather than calling `.build().send()?` on the request, pass it to the `net`
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// This allows the `net` to either make the network request as normal, or, if we are
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// under test, to handle the request as the test dictates.
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// NOTE: if the `.build().send()` is called on the `request` then that WILL result in
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// a real network request being made, even under test conditions. Only ever use the
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// `net.send(...)` function to keep your code testable.
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let response: reqwest::Response = net.send(request).await?;
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let body = response.text().await?;
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println!("fetched {} bytes", body.bytes().len());
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println!("writing file: {}", file_path.display());
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// Uses the file system abstraction to create a handle for a file.
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let file: kxio::fs::PathReal<kxio::fs::FileMarker> = fs.file(file_path);
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// Writes the body to the file.
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file.write(body)?;
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Ok(())
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}
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/// An function that uses a `FileSystem` object to interact with the outside world.
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fn delete_file(file_path: &Path, fs: &kxio::fs::FileSystem) -> kxio::Result<()> {
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println!("reading file: {}", file_path.display());
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// Uses the file system abstraction to create a handle for a file.
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let file: kxio::fs::PathReal<kxio::fs::FileMarker> = fs.file(file_path);
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// Creates a `Reader` which loaded the file into memory.
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let reader: kxio::fs::Reader = file.reader()?;
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let contents: &str = reader.as_str();
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println!("{contents}");
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Ok(())
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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// This test demonstrates how to use the `kxio` to test your program.
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#[tokio::test]
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async fn should_save_remote_body() {
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//given
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// Create a fake/mock network abstraction
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// When `net` goes out of scope it will check that all the expected network requests (see
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// `net.on(...)` below) were all made. If there are any that were not made, the test will
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// be failed. If you want to avoid this, then call `net.reset()` before your test ends.
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let mock_net: kxio::net::MockNet = kxio::net::mock();
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let url = "http://localhost:8080";
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// declare what response should be made for a given request
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let response = mock_net.response().body("contents").expect("response body");
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mock_net
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.on(http::Method::GET)
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.url(url::Url::parse(url).expect("parse url"))
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.respond(response);
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// Create a temporary directory that will be deleted with `fs` goes out of scope
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let fs = kxio::fs::temp().expect("temp fs");
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let file_path = fs.base().join("foo");
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// Create a [Net] from the [MockNet] to pass to the system under tets
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let net = kxio::net::Net::from(mock_net);
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//when
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// Pass the file sytsem and network abstractions to the code to be tested
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download_and_save_to_file(url, &file_path, &fs, &net)
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.await
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.expect("system under test");
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//then
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// Read the file
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let file = fs.file(&file_path);
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let reader = file.reader().expect("reader");
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let contents = reader.as_str();
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assert_eq!(contents, "contents");
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// not needed for this test, but should it be needed, we can avoid checking for any
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// unconsumed request matches.
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// let mock_net = kxio::net::MockNet::try_from(net).expect("recover mock");
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// mock_net.reset();
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}
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}
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