transactions: Add JSON response format

Rocket makes it easy to dispatch requests for the same path to different
methods based on the `Accept` request header via the `format` argument
to the request attribute.

We'll use this JSON response format to populate a dropdown on the Add
Receipt form, which can be used to automatically fill the fields for
receipt data based on an existing transaction.

src/main.rs

@@ -2,11 +2,13 @@ mod config;
 mod firefly;
 mod receipts;
 
+use chrono::{DateTime, FixedOffset};
 use rocket::fairing::{self, AdHoc};
 use rocket::form::Form;
 use rocket::fs::{FileServer, TempFile};
 use rocket::http::Status;
-use rocket::response::Redirect;
+use rocket::response::{Redirect, Responder};
+use rocket::serde::json::Json;
 use rocket::tokio::io::{AsyncReadExt, BufReader};
 use rocket::{Rocket, State};
 use rocket_db_pools::Database as RocketDatabase;
@@ -49,7 +51,7 @@ pub struct Transaction {
     pub id: String,
     pub amount: f64,
     pub description: String,
-    pub date: String,
+    pub date: DateTime<FixedOffset>,
 }
 
 #[derive(rocket::FromForm)]
@@ -59,6 +61,27 @@ struct TransactionPostData<'r> {
     photo: Vec<TempFile<'r>>,
 }
 
+#[derive(Serialize)]
+struct ErrorBody {
+    error: String,
+}
+
+#[derive(Responder)]
+#[response(status = 500)]
+struct ErrorResponse {
+    error: Json<ErrorBody>,
+}
+
+impl ErrorResponse {
+    pub fn new<S: Into<String>>(error: S) -> Self {
+        Self {
+            error: Json(ErrorBody {
+                error: error.into(),
+            }),
+        }
+    }
+}
+
 impl TryFrom<TransactionRead> for Transaction {
     type Error = &'static str;
 
@@ -81,7 +104,7 @@ impl TryFrom<TransactionRead> for Transaction {
             id: t.id,
             amount,
             description,
-            date: date.format("%A, %_d %B %Y").to_string(),
+            date,
         })
     }
 }
@@ -91,7 +114,7 @@ async fn index() -> Redirect {
     Redirect::to("/receipts")
 }
 
-#[rocket::get("/transactions")]
+#[rocket::get("/transactions", format = "html", rank = 2)]
 async fn transaction_list(ctx: &State<Context>) -> (Status, Template) {
     let result = ctx
         .firefly
@@ -136,6 +159,36 @@ async fn transaction_list(ctx: &State<Context>) -> (Status, Template) {
     }
 }
 
+#[rocket::get("/transactions", format = "json")]
+async fn transaction_list_json(
+    ctx: &State<Context>,
+) -> Result<Json<Vec<Transaction>>, ErrorResponse> {
+    let result = ctx
+        .firefly
+        .search_transactions(&ctx.config.firefly.search_query)
+        .await
+        .map_err(|e| {
+            error!("Error fetching transaction list: {}", e);
+            ErrorResponse::new(
+                "Failed to fetch transaction list from Firefly III",
+            )
+        })?;
+
+    Ok(Json(
+        result
+            .data
+            .into_iter()
+            .filter_map(|t| match Transaction::try_from(t) {
+                Ok(t) => Some(t),
+                Err(e) => {
+                    error!("Error parsing transaction details: {}", e);
+                    None
+                },
+            })
+            .collect(),
+    ))
+}
+
 #[rocket::get("/transactions/<id>")]
 async fn get_transaction(id: &str, ctx: &State<Context>) -> Option<Template> {
     match ctx.firefly.get_transaction(id).await {
@@ -272,6 +325,7 @@ async fn rocket() -> _ {
             rocket::routes![
                 index,
                 transaction_list,
+                transaction_list_json,
                 get_transaction,
                 update_transaction
             ],