✨ feat(gmail): implement list functionality for Gmail API

- Add list functionality to retrieve and display email subjects from Gmail.
- Integrate with google_gmail1 crate for Gmail API interactions.
- Implement authentication using InstalledFlowAuthenticator.
- Retrieve and display email subjects using the Gmail API.
- Configure max results to limit displayed subjects.

src/list.rs

@@ -1,38 +1,109 @@
+use google_clis_common as common;
 use google_gmail1::{
-    Error, Gmail, hyper_rustls::HttpsConnector, hyper_util::client::legacy::connect::HttpConnector,
+    Gmail,
+    hyper_rustls::{HttpsConnector, HttpsConnectorBuilder},
+    hyper_util::{
+        client::legacy::{Client, connect::HttpConnector},
+        rt::TokioExecutor,
+    },
+    yup_oauth2::{ApplicationSecret, InstalledFlowAuthenticator, InstalledFlowReturnMethod},
 };
 
+use crate::{Credential, Error};
+
+const DEFAULT_MAX_RESULTS: u32 = 10;
+
 /// Struct to capture configuration for List API call.
 pub struct List {
     hub: Gmail<HttpsConnector<HttpConnector>>,
+    max_results: u32,
 }
 
 impl List {
     /// Create a new List struct and add the Gmail api connection.
-    pub fn new(hub: Gmail<HttpsConnector<HttpConnector>>) -> Self {
-        List { hub }
+    pub async fn new(credential: &str) -> Result<Self, Error> {
+        let (config_dir, secret) = {
+            let config_dir = match common::assure_config_dir_exists("~/.cull-gmail") {
+                Err(e) => return Err(Error::InvalidOptionsError(e, 3)),
+                Ok(p) => p,
+            };
+
+            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();
+
+        Ok(List {
+            hub: Gmail::new(client, auth),
+            max_results: DEFAULT_MAX_RESULTS,
+        })
     }
 
     /// Run the Gmail api as configured
-    pub async fn run(&self) {
-        let result = self.hub.users().messages_list("me").doit().await;
+    pub async fn run(&self) -> Result<(), Error> {
+        let (_response, list) = self
+            .hub
+            .users()
+            .messages_list("me")
+            .max_results(self.max_results)
+            .doit()
+            .await?;
 
-        match result {
-            Err(e) => match e {
-                // The Error enum provides details about what exactly happened.
-                // You can also just use its `Debug`, `Display` or `Error` traits
-                Error::HttpError(_)
-                | Error::Io(_)
-                | Error::MissingAPIKey
-                | Error::MissingToken(_)
-                | Error::Cancelled
-                | Error::UploadSizeLimitExceeded(_, _)
-                | Error::Failure(_)
-                | Error::BadRequest(_)
-                | Error::FieldClash(_)
-                | Error::JsonDecodeError(_, _) => println!("{e}"),
-            },
-            Ok(res) => println!("Success: {res:?}"),
+        // println!("{list:#?}");
+        if let Some(messages) = list.messages {
+            for message in messages {
+                if let Some(id) = message.id {
+                    log::trace!("{id}");
+                    let (_res, m) = self
+                        .hub
+                        .users()
+                        .messages_get("me", &id)
+                        .add_scope("https://www.googleapis.com/auth/gmail.metadata")
+                        .format("metadata")
+                        .add_metadata_headers("subject")
+                        .doit()
+                        .await?;
+
+                    let mut subject = String::new();
+                    if let Some(payload) = m.payload {
+                        if let Some(headers) = payload.headers {
+                            for header in headers {
+                                if header.name.is_some()
+                                    && header.name.unwrap() == "Subject"
+                                    && header.value.is_some()
+                                {
+                                    subject = header.value.unwrap();
+                                    break;
+                                } else {
+                                    continue;
                                 }
                             }
+                        }
+                    }
+
+                    log::info!("{subject:?}");
+                }
+            }
+        }
+        Ok(())
+    }
 }