♻️ refactor(gmail): rename labels.rs to gmail_client.rs

- Renamed `labels.rs` to `gmail_client.rs` for better clarity
- Refactor `Labels` struct to `GmailClient` for better naming
- Update `get_label_map` to use BTreeMap for label storage
- Remove the show flag functionality

src/gmail_client.rs

@@ -0,0 +1,107 @@
+use std::collections::BTreeMap;
+
+use google_gmail1::{
+    Gmail,
+    hyper_rustls::{HttpsConnector, HttpsConnectorBuilder},
+    hyper_util::{
+        client::legacy::{Client, connect::HttpConnector},
+        rt::TokioExecutor,
+    },
+    yup_oauth2::{ApplicationSecret, InstalledFlowAuthenticator, InstalledFlowReturnMethod},
+};
+
+use crate::{Credential, Error, Result};
+
+/// Default for the maximum number of results to return on a page
+pub const DEFAULT_MAX_RESULTS: &str = "200";
+
+/// Struct to capture configuration for List API call.
+pub struct GmailClient {
+    hub: Gmail<HttpsConnector<HttpConnector>>,
+    label_map: BTreeMap<String, String>,
+}
+
+impl std::fmt::Debug for GmailClient {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.debug_struct("Labels")
+            .field("label_map", &self.label_map)
+            .finish()
+    }
+}
+
+impl GmailClient {
+    /// Create a new List struct and add the Gmail api connection.
+    pub async fn new(credential: &str) -> Result<Self> {
+        let (config_dir, secret) = {
+            let config_dir = crate::utils::assure_config_dir_exists("~/.cull-gmail")?;
+
+            let secret: ApplicationSecret = Credential::load_json_file(credential).into();
+            (config_dir, secret)
+        };
+
+        let executor = TokioExecutor::new();
+        let connector = HttpsConnectorBuilder::new()
+            .with_native_roots()
+            .unwrap()
+            .https_or_http()
+            .enable_http1()
+            .build();
+
+        let client = Client::builder(executor.clone()).build(connector.clone());
+
+        let auth = InstalledFlowAuthenticator::with_client(
+            secret,
+            InstalledFlowReturnMethod::HTTPRedirect,
+            Client::builder(executor).build(connector),
+        )
+        .persist_tokens_to_disk(format!("{config_dir}/gmail1"))
+        .build()
+        .await
+        .unwrap();
+
+        let hub = Gmail::new(client, auth);
+        let label_map = GmailClient::get_label_map(&hub).await?;
+
+        Ok(GmailClient { hub, label_map })
+    }
+
+    /// Create a new List struct and add the Gmail api connection.
+    async fn get_label_map(
+        hub: &Gmail<HttpsConnector<HttpConnector>>,
+    ) -> Result<BTreeMap<String, String>> {
+        let call = hub.users().labels_list("me");
+        let (_response, list) = call
+            .add_scope("https://mail.google.com/")
+            .doit()
+            .await
+            .map_err(Box::new)?;
+
+        let Some(label_list) = list.labels else {
+            return Err(Error::NoLabelsFound);
+        };
+
+        let mut label_map = BTreeMap::new();
+        for label in &label_list {
+            if label.id.is_some() && label.name.is_some() {
+                let name = label.name.clone().unwrap();
+                let id = label.id.clone().unwrap();
+                label_map.insert(name, id);
+            }
+        }
+
+        Ok(label_map)
+    }
+
+    /// Return the id for the name from the labels map.
+    /// Returns `None` if the name is not found in the map.
+    pub fn get_label_id(&self, name: &str) -> Option<String> {
+        self.label_map.get(name).cloned()
+    }
+
+    /// Show the label names and related id.
+    pub fn show_label(&self) {
+        for (name, id) in self.label_map.iter() {
+            log::info!("{name}: {id}")
+        }
+    }
+}