Refactoring for Show/Delete handlers

Refactor the existing code architecture to be a little flatter to support adding the show and delete handlers.  Currently these two handlers are just stubbed functions, but the CLI looks about right.

src/commands.rs

@@ -14,6 +14,117 @@
  *    limitations under the License.
  */
 
-pub mod catalog;
-pub mod tags;
-pub mod version;
+use crate::api;
+use crate::config::Config;
+use crate::error::ApiError;
+use serde::Deserialize;
+
+/// Handler for the `Catalog` endpoint
+///
+/// Fetch the list of repository names from the Docker Registry API, and
+/// simply print the resulting names to stdout.
+///
+/// # Errors:
+///
+/// Returns an `ApiError` if there is a problem fetching or parsing the
+/// responses from the Docker Registry API.  
+pub async fn catalog_handler(config: &Config) -> Result<(), ApiError> {
+    #[derive(Deserialize)]
+    struct Response {
+        repositories: Vec<String>,
+    }
+
+    log::trace!("catalog_handler()");
+    let path = "v2/_catalog";
+
+    let responses: Vec<Response> = api::fetch_all(config, path).await?;
+    let repository_list: Vec<&str> = responses
+        .iter()
+        .flat_map(|r| r.repositories.iter().map(String::as_str))
+        .collect();
+
+    for repository in repository_list {
+        println!("{repository}");
+    }
+
+    Ok(())
+}
+
+/// Handler for the `Tags` endpoint
+///
+/// Fetch the list of tags names for a given image from the Docker Registry API, and
+/// simply print the resulting names to stdout.
+///
+/// # Errors:
+///
+/// Returns an `ApiError` if there is a problem fetching or parsing the
+/// responses from the Docker Registry API.  
+pub async fn tags_handler(config: &Config, name: &str) -> Result<(), ApiError> {
+    #[derive(Deserialize)]
+    struct Response {
+        tags: Vec<String>,
+    }
+
+    log::trace!("tags_handler(name: {name})");
+    let path = format!("/v2/{name}/tags/list");
+
+    let responses: Vec<Response> = api::fetch_all(config, &path).await?;
+    let tag_list: Vec<&str> = responses
+        .iter()
+        .flat_map(|r| r.tags.iter().map(String::as_str))
+        .collect();
+
+    for tag in tag_list {
+        println!("{tag}");
+    }
+
+    Ok(())
+}
+
+/// Handler function for showing manifest details
+///
+/// # Errors:
+///
+/// Returns an `ApiError` if there is a problem fetching the manifest or if there
+/// is a problem parsing the response from the Docker Registry API.
+pub async fn show_handler(config: &Config, image: &str, tag: &str) -> Result<(), ApiError> {
+    log::trace!("show_handler(image: {image}, tag: {tag})");
+    let base = config.registry_url.to_owned();
+    let path = format!("/v2/{image}/manifests/{tag}");
+    let _url = base.join(&path)?;
+    Ok(())
+}
+
+/// Handler function for deleting a manifest for a given tagged image.
+///
+/// # Errors:
+///
+/// Returns and `ApiError` if there is a problem converting the given tag to a
+/// manifest digest, or if there is a problem deleting the manifest from the
+/// Docker Registry API.
+pub async fn delete_handler(_config: &Config, image: &str, tag: &str) -> Result<(), ApiError> {
+    log::trace!("delete_handler(image: {image}, tag: {tag})");
+    todo!()
+}
+
+// Path to the Docker Registry APIs "api version check" endpoint.
+
+/// Handler for the API Version Check.
+///
+/// # Errors:
+///
+/// Returns an `ApiError` if there is a problem communicating with the
+/// endpoint or if the required version is not supported.
+pub async fn check_handler(config: &Config) -> Result<(), ApiError> {
+    log::trace!("check_handler()");
+
+    let base = config.registry_url.to_owned();
+    let path = "/v2";
+    let url = base.join(path)?;
+
+    let response = reqwest::get(url).await?;
+
+    api::parse_response_status(&response)?;
+    println!("Ok");
+    Ok(())
+}