How can I initiate a 1:1 conversation for any given mail address from a bot written in Rust?

Ivan · June 12, 2023, 6:26pm

Hi :

I’m looking at the Rust API for bots and I cannot find the proper way to create a new Chat for a given mail address. It appears that the only way to access such 1:1 chats is by having them already in the database, which would imply that the bot cannot start a conversation with any contact it wants (ie: it’s the contact who must send the first message, as in Telegram API).

Is that by design? Is it a lack of feature? Or is it simply that I’m not able to figure it out?

Thanks in advance.

Simon · June 12, 2023, 9:20pm

you can look up api here: deltachat - Rust though the c api might be more complete in terms of documentation comments: https://c.delta.chat/

The function you are looking for is Contact::add_or_lookup, though I personally would also have expected some more clear naming like a method with “create” or “new” in it’s name.

Ivan · June 13, 2023, 6:14am

Thx for the fast reply . However, I’m not sure if that’s what I’m looking for…

That function adds a contact, but I still need a Chat to use send_msg, and that’s the root of my problem: how do I create a Chat if it is not already present in the DB.

Maybe creating a group chat with create_group_chat and adding a single contact would work? I don’t think so, because it would still allow me to add more contacts and the Chat object would not return Single as chat type, I guess…

I’ll review the C API docs in more depth because I hadn’t the link (thx for that).

Regarding Rust docs, I didn’t know about the link but I generated them with cargo doc locally .

adbenitez · June 13, 2023, 7:38am

hi @Ivan, I guess you can use ChatId::create_for_contact

I am not a Rust developer, but if I would create a bot in Rust I would have a look at the usage of the API by the deltachat-jsonrpc program, for example, this is how the Rust API is used to create a 1:1 chat there:

github.com

deltachat/deltachat-core-rust/blob/0d0e223238bd54f19a50eddcf7466732a383a3e4/deltachat-jsonrpc/src/api/mod.rs#L1237-L1244


      
          /// Returns contact id of the created or existing DM chat with that contact
          async fn create_chat_by_contact_id(&self, account_id: u32, contact_id: u32) -> Result<u32> {
              let ctx = self.get_context(account_id).await?;
              let contact = Contact::get_by_id(&ctx, ContactId::new(contact_id)).await?;
              ChatId::create_for_contact(&ctx, contact.id)
                  .await
                  .map(|id| id.to_u32())
          }

adbenitez · June 13, 2023, 7:46am

so you would first use the email address to create the contact:

github.com

deltachat/deltachat-core-rust/blob/0d0e223238bd54f19a50eddcf7466732a383a3e4/deltachat-jsonrpc/src/api/mod.rs#L1218-L1235


      
          /// Add a single contact as a result of an explicit user action.
          ///
          /// Returns contact id of the created or existing contact
          async fn create_contact(
              &self,
              account_id: u32,
              email: String,
              name: Option<String>,
          ) -> Result<u32> {
              let ctx = self.get_context(account_id).await?;
              if !may_be_valid_addr(&email) {
                  bail!(anyhow!(
                      "provided email address is not a valid email address"
                  ))
              }
              let contact_id = Contact::create(&ctx, &name.unwrap_or_default(), &email).await?;
              Ok(contact_id.to_u32())
          }

and then use the contact to create a chat with the previously mentioned ChatId::create_for_contact

Ivan · June 13, 2023, 8:38am

Whoa, very unexpected. Good catch

I was misled by the fact that ChatId sounded like an “empty” type just to wrap the number that identified the chat so I didn’t really realise that I could find the method there.

In fact, looking at the ContactId API for example, there are no methods to create contacts because they are in Contact, as @Simon pointed out in the first answer. Thus, I expected something like Chat::create_for_contact or Contact::create_chat…

In any case, thx to both for the answers, I was getting crazy