use crate::objects::{comment::ApubComment, person::ApubPerson};
use activitypub_federation::{
  config::Data,
  fetch::webfinger::webfinger_resolve_actor,
  kinds::link::MentionType,
  traits::Actor,
};
use lemmy_api_common::context::LemmyContext;
use lemmy_db_schema::{
  source::{comment::Comment, person::Person, post::Post},
  traits::Crud,
  utils::DbPool,
};
use lemmy_utils::{
  error::{FederationError, LemmyResult},
  utils::mention::scrape_text_for_mentions,
};
use serde::{Deserialize, Serialize};
use serde_json::Value;
use url::Url;

#[derive(Clone, Debug, Deserialize, Serialize)]
#[serde(untagged)]
pub enum MentionOrValue {
  Mention(Mention),
  Value(Value),
}

#[derive(Clone, Debug, Deserialize, Serialize)]
pub struct Mention {
  pub href: Url,
  name: Option<String>,
  #[serde(rename = "type")]
  pub kind: MentionType,
}

pub struct MentionsAndAddresses {
  pub ccs: Vec<Url>,
  pub tags: Vec<MentionOrValue>,
}

/// This takes a comment, and builds a list of to_addresses, inboxes,
/// and mention tags, so they know where to be sent to.
/// Addresses are the persons / addresses that go in the cc field.
pub async fn collect_non_local_mentions(
  comment: &ApubComment,
  context: &Data<LemmyContext>,
) -> LemmyResult<MentionsAndAddresses> {
  let parent_creator = get_comment_parent_creator(&mut context.pool(), comment).await?;
  let mut addressed_ccs: Vec<Url> = vec![parent_creator.id()];

  // Add the mention tag
  let parent_creator_tag = Mention {
    href: parent_creator.ap_id.clone().into(),
    name: Some(format!(
      "@{}@{}",
      &parent_creator.name,
      &parent_creator
        .id()
        .domain()
        .ok_or(FederationError::UrlWithoutDomain)?
    )),
    kind: MentionType::Mention,
  };
  let mut tags = vec![parent_creator_tag];

  // Get the person IDs for any mentions
  let mentions = scrape_text_for_mentions(&comment.content)
    .into_iter()
    // Filter only the non-local ones
    .filter(|m| !m.is_local(&context.settings().hostname));

  for mention in mentions {
    let identifier = format!("{}@{}", mention.name, mention.domain);
    let person = webfinger_resolve_actor::<LemmyContext, ApubPerson>(&identifier, context).await;
    if let Ok(person) = person {
      addressed_ccs.push(person.ap_id.to_string().parse()?);

      let mention_tag = Mention {
        href: person.id(),
        name: Some(mention.full_name()),
        kind: MentionType::Mention,
      };
      tags.push(mention_tag);
    }
  }

  let tags = tags.into_iter().map(MentionOrValue::Mention).collect();
  Ok(MentionsAndAddresses {
    ccs: addressed_ccs,
    tags,
  })
}

/// Returns the apub ID of the person this comment is responding to. Meaning, in case this is a
/// top-level comment, the creator of the post, otherwise the creator of the parent comment.
async fn get_comment_parent_creator(
  pool: &mut DbPool<'_>,
  comment: &Comment,
) -> LemmyResult<ApubPerson> {
  let parent_creator_id = if let Some(parent_comment_id) = comment.parent_comment_id() {
    let parent_comment = Comment::read(pool, parent_comment_id).await?;
    parent_comment.creator_id
  } else {
    let parent_post_id = comment.post_id;
    let parent_post = Post::read(pool, parent_post_id).await?;
    parent_post.creator_id
  };
  Ok(Person::read(pool, parent_creator_id).await?.into())
}
