add dc_receive_backup ffi (#3504)

* add dc_receive_backup ffi

* fix compile issues

* make clippy happy

Co-authored-by: dignifiedquire <me@dignifiedquire.com>

deltachat-ffi/Cargo.toml

@@ -27,6 +27,7 @@ thiserror = "1"
 rand = "0.7"
 once_cell = "1.16.0"
 iroh-share = { git = "https://github.com/n0-computer/iroh", branch = "iroh-share" }
+multibase = "0.9"
 
 [features]
 default = ["vendored"]

deltachat-ffi/src/lib.rs

@@ -2223,7 +2223,10 @@ pub unsafe extern "C" fn dc_send_backup(
             imex::send_backup(ctx, folder.as_ref(), passphrase)
                 .await
                 .map(|(sender, transfer)| {
-                    Box::into_raw(Box::new(dc_backup_sender { sender, transfer }))
+                    Box::into_raw(Box::new(dc_backup_sender {
+                        _sender: sender,
+                        transfer,
+                    }))
                 })
                 .log_err(ctx, "send_backup failed")
                 .unwrap_or_else(|_| ptr::null_mut())
@@ -2235,7 +2238,7 @@ pub unsafe extern "C" fn dc_send_backup(
 }
 
 pub struct dc_backup_sender {
-    sender: iroh_share::Sender,
+    _sender: iroh_share::Sender,
     transfer: iroh_share::SenderTransfer,
 }
 
@@ -2265,6 +2268,30 @@ pub unsafe extern "C" fn dc_backup_sender_unref(bs: *mut dc_backup_sender) {
     }
 }
 
+#[no_mangle]
+pub unsafe extern "C" fn dc_receive_backup(
+    ctx: *mut dc_context_t,
+    ticket: *const libc::c_char,
+    passphrase: *const libc::c_char,
+) {
+    if ctx.is_null() || ticket.is_null() {
+        eprintln!("ignoring careless call to dc_receive_backup");
+        return;
+    }
+    let ctx = &*ctx;
+    let ticket = multibase::decode(to_string_lossy(ticket))
+        .map(|(_, ticket)| ticket)
+        .unwrap_or_default();
+
+    let passphrase = to_opt_string_lossy(passphrase);
+
+    spawn(async move {
+        imex::receive_backup(ctx, ticket, passphrase)
+            .await
+            .log_err(ctx, "IMEX failed")
+    });
+}
+
 #[no_mangle]
 pub unsafe extern "C" fn dc_imex_has_backup(
     context: *mut dc_context_t,