Plume/plume-models/src/posts.rs

use activitypub::{
    CustomObject,
    activity::{Create, Delete, Update},
    link,
    object::{Article, Image, Tombstone},
};
use canapi::{Error as ApiError, Provider};
use chrono::{NaiveDateTime, TimeZone, Utc};
use diesel::{self, BelongingToDsl, ExpressionMethods, QueryDsl, RunQueryDsl};
use heck::{CamelCase, KebabCase};
use scheduled_thread_pool::ScheduledThreadPool as Worker;
use serde_json;
use std::collections::HashSet;

use plume_api::posts::PostEndpoint;
use plume_common::{
    activity_pub::{
        inbox::{Deletable, FromActivity},
        broadcast, Hashtag, Id, IntoId, Licensed, Source, PUBLIC_VISIBILTY,
    },
    utils::md_to_html,
};
use blogs::Blog;
use instance::Instance;
use medias::Media;
use mentions::Mention;
use post_authors::*;
use safe_string::SafeString;
use search::Searcher;
use schema::posts;
use tags::*;
use users::User;
use {ap_url, Connection, BASE_URL, Error, Result, ApiResult};

pub type LicensedArticle = CustomObject<Licensed, Article>;

#[derive(Queryable, Identifiable, Serialize, Clone, AsChangeset)]
#[changeset_options(treat_none_as_null = "true")]
pub struct Post {
    pub id: i32,
    pub blog_id: i32,
    pub slug: String,
    pub title: String,
    pub content: SafeString,
    pub published: bool,
    pub license: String,
    pub creation_date: NaiveDateTime,
    pub ap_url: String,
    pub subtitle: String,
    pub source: String,
    pub cover_id: Option<i32>,
}

#[derive(Insertable)]
#[table_name = "posts"]
pub struct NewPost {
    pub blog_id: i32,
    pub slug: String,
    pub title: String,
    pub content: SafeString,
    pub published: bool,
    pub license: String,
    pub creation_date: Option<NaiveDateTime>,
    pub ap_url: String,
    pub subtitle: String,
    pub source: String,
    pub cover_id: Option<i32>,
}

impl<'a> Provider<(&'a Connection, &'a Worker, &'a Searcher, Option<i32>)> for Post {
    type Data = PostEndpoint;

    fn get(
        (conn, _worker, _search, user_id): &(&Connection, &Worker, &Searcher, Option<i32>),
        id: i32,
    ) -> ApiResult<PostEndpoint> {
        if let Ok(post) = Post::get(conn, id) {
            if !post.published && !user_id.map(|u| post.is_author(conn, u).unwrap_or(false)).unwrap_or(false) {
                return Err(ApiError::Authorization(
                    "You are not authorized to access this post yet.".to_string(),
                ));
            }
            Ok(PostEndpoint {
                id: Some(post.id),
                title: Some(post.title.clone()),
                subtitle: Some(post.subtitle.clone()),
                content: Some(post.content.get().clone()),
                source: Some(post.source.clone()),
                author: Some(post.get_authors(conn).map_err(|_| ApiError::NotFound("Authors not found".into()))?[0].username.clone()),
                blog_id: Some(post.blog_id),
                published: Some(post.published),
                creation_date: Some(post.creation_date.format("%Y-%m-%d").to_string()),
                license: Some(post.license.clone()),
                tags: Some(Tag::for_post(conn, post.id).map_err(|_| ApiError::NotFound("Tags not found".into()))?.into_iter().map(|t| t.tag).collect()),
                cover_id: post.cover_id,
            })
        } else {
            Err(ApiError::NotFound("Request post was not found".to_string()))
        }
    }

    fn list(
        (conn, _worker, _search, user_id): &(&Connection, &Worker, &Searcher, Option<i32>),
        filter: PostEndpoint,
    ) -> Vec<PostEndpoint> {
        let mut query = posts::table.into_boxed();
        if let Some(title) = filter.title {
            query = query.filter(posts::title.eq(title));
        }
        if let Some(subtitle) = filter.subtitle {
            query = query.filter(posts::subtitle.eq(subtitle));
        }
        if let Some(content) = filter.content {
            query = query.filter(posts::content.eq(content));
        }

        query.get_results::<Post>(*conn).map(|ps| ps.into_iter()
            .filter(|p| p.published || user_id.map(|u| p.is_author(conn, u).unwrap_or(false)).unwrap_or(false))
            .map(|p| PostEndpoint {
                id: Some(p.id),
                title: Some(p.title.clone()),
                subtitle: Some(p.subtitle.clone()),
                content: Some(p.content.get().clone()),
                source: Some(p.source.clone()),
                author: Some(p.get_authors(conn).unwrap_or_default()[0].username.clone()),
                blog_id: Some(p.blog_id),
                published: Some(p.published),
                creation_date: Some(p.creation_date.format("%Y-%m-%d").to_string()),
                license: Some(p.license.clone()),
                tags: Some(Tag::for_post(conn, p.id).unwrap_or(vec![]).into_iter().map(|t| t.tag).collect()),
                cover_id: p.cover_id,
            })
            .collect()
        ).unwrap_or(vec![])
    }

    fn update(
        (_conn, _worker, _search, _user_id): &(&Connection, &Worker, &Searcher, Option<i32>),
        _id: i32,
        _new_data: PostEndpoint,
    ) -> ApiResult<PostEndpoint> {
        unimplemented!()
    }

    fn delete((conn, _worker, search, user_id): &(&Connection, &Worker, &Searcher, Option<i32>), id: i32) {
        let user_id = user_id.expect("Post as Provider::delete: not authenticated");
        if let Ok(post) = Post::get(conn, id) {
            if post.is_author(conn, user_id).unwrap_or(false) {
                post.delete(&(conn, search)).ok().expect("Post as Provider::delete: delete error");
            }
        }
    }

    fn create(
        (conn, worker, search, user_id): &(&Connection, &Worker, &Searcher, Option<i32>),
        query: PostEndpoint,
    ) -> ApiResult<PostEndpoint> {
        if user_id.is_none() {
            return Err(ApiError::Authorization("You are not authorized to create new articles.".to_string()));
        }

        let title = query.title.clone().expect("No title for new post in API");
        let slug = query.title.unwrap().to_kebab_case();

        let date = query.creation_date.clone()
            .and_then(|d| NaiveDateTime::parse_from_str(format!("{} 00:00:00", d).as_ref(), "%Y-%m-%d %H:%M:%S").ok());

        let domain = &Instance::get_local(&conn)
            .map_err(|_| ApiError::NotFound("posts::update: Error getting local instance".into()))?
            .public_domain;
        let (content, mentions, hashtags) = md_to_html(query.source.clone().unwrap_or(String::new()).clone().as_ref(), domain);

        let author = User::get(conn, user_id.expect("<Post as Provider>::create: no user_id error"))
            .map_err(|_| ApiError::NotFound("Author not found".into()))?;
        let blog = match query.blog_id {
            Some(x) => x,
            None => Blog::find_for_author(conn, &author).map_err(|_| ApiError::NotFound("No default blog".into()))?[0].id
        };

        if Post::find_by_slug(conn, &slug, blog).is_ok() {
            // Not an actual authorization problem, but we have nothing better for now…
            // TODO: add another error variant to canapi and add it there
            return Err(ApiError::Authorization("A post with the same slug already exists".to_string()));
        }

        let post = Post::insert(conn, NewPost {
            blog_id: blog,
            slug: slug,
            title: title,
            content: SafeString::new(content.as_ref()),
            published: query.published.unwrap_or(true),
            license: query.license.unwrap_or(Instance::get_local(conn)
                .map(|i| i.default_license)
                .unwrap_or(String::from("CC-BY-SA"))),
            creation_date: date,
            ap_url: String::new(),
            subtitle: query.subtitle.unwrap_or(String::new()),
            source: query.source.expect("Post API::create: no source error"),
            cover_id: query.cover_id,
        }, search).map_err(|_| ApiError::NotFound("Creation error".into()))?;
        post.update_ap_url(conn).map_err(|_| ApiError::NotFound("Error setting ActivityPub URLs".into()))?;;

        PostAuthor::insert(conn, NewPostAuthor {
            author_id: author.id,
            post_id: post.id
        }).map_err(|_| ApiError::NotFound("Error saving authors".into()))?;

        if let Some(tags) = query.tags {
            for tag in tags {
                Tag::insert(conn, NewTag {
                    tag: tag,
                    is_hashtag: false,
                    post_id: post.id
                }).map_err(|_| ApiError::NotFound("Error saving tags".into()))?;
            }
        }
        for hashtag in hashtags {
            Tag::insert(conn, NewTag {
                tag: hashtag.to_camel_case(),
                is_hashtag: true,
                post_id: post.id
            }).map_err(|_| ApiError::NotFound("Error saving hashtags".into()))?;
        }

        if post.published {
            for m in mentions.into_iter() {
                Mention::from_activity(
                    &*conn,
                    &Mention::build_activity(&*conn, &m).map_err(|_| ApiError::NotFound("Couldn't build mentions".into()))?,
                    post.id,
                    true,
                    true
                ).map_err(|_| ApiError::NotFound("Error saving mentions".into()))?;
            }

            let act = post.create_activity(&*conn).map_err(|_| ApiError::NotFound("Couldn't create activity".into()))?;
            let dest = User::one_by_instance(&*conn).map_err(|_| ApiError::NotFound("Couldn't list remote instances".into()))?;
            worker.execute(move || broadcast(&author, act, dest));
        }

        Ok(PostEndpoint {
            id: Some(post.id),
            title: Some(post.title.clone()),
            subtitle: Some(post.subtitle.clone()),
            content: Some(post.content.get().clone()),
            source: Some(post.source.clone()),
            author: Some(post.get_authors(conn).map_err(|_| ApiError::NotFound("No authors".into()))?[0].username.clone()),
            blog_id: Some(post.blog_id),
            published: Some(post.published),
            creation_date: Some(post.creation_date.format("%Y-%m-%d").to_string()),
            license: Some(post.license.clone()),
            tags: Some(Tag::for_post(conn, post.id).map_err(|_| ApiError::NotFound("Tags not found".into()))?.into_iter().map(|t| t.tag).collect()),
            cover_id: post.cover_id,
        })
    }
}

impl Post {
    get!(posts);
    find_by!(posts, find_by_slug, slug as &str, blog_id as i32);
    find_by!(posts, find_by_ap_url, ap_url as &str);

    last!(posts);
    pub fn insert(conn: &Connection, new: NewPost, searcher: &Searcher) -> Result<Self> {
        diesel::insert_into(posts::table)
            .values(new)
            .execute(conn)?;
        let post = Self::last(conn)?;
        searcher.add_document(conn, &post)?;
        Ok(post)
    }
    pub fn update(&self, conn: &Connection, searcher: &Searcher) -> Result<Self> {
        diesel::update(self)
            .set(self)
            .execute(conn)?;
        let post = Self::get(conn, self.id)?;
        searcher.update_document(conn, &post)?;
        Ok(post)
    }


    pub fn list_by_tag(conn: &Connection, tag: String, (min, max): (i32, i32)) -> Result<Vec<Post>> {
        use schema::tags;

        let ids = tags::table.filter(tags::tag.eq(tag)).select(tags::post_id);
        posts::table
            .filter(posts::id.eq_any(ids))
            .filter(posts::published.eq(true))
            .order(posts::creation_date.desc())
            .offset(min.into())
            .limit((max - min).into())
            .load(conn)
            .map_err(Error::from)
    }

    pub fn count_for_tag(conn: &Connection, tag: String) -> Result<i64> {
        use schema::tags;
        let ids = tags::table.filter(tags::tag.eq(tag)).select(tags::post_id);
        posts::table
            .filter(posts::id.eq_any(ids))
            .filter(posts::published.eq(true))
            .count()
            .load(conn)?
            .iter()
            .next()
            .map(|x| *x)
            .ok_or(Error::NotFound)
    }

    pub fn count_local(conn: &Connection) -> Result<i64> {
        use schema::post_authors;
        use schema::users;
        let local_authors = users::table
            .filter(users::instance_id.eq(Instance::get_local(conn)?.id))
            .select(users::id);
        let local_posts_id = post_authors::table
            .filter(post_authors::author_id.eq_any(local_authors))
            .select(post_authors::post_id);
        posts::table
            .filter(posts::id.eq_any(local_posts_id))
            .filter(posts::published.eq(true))
            .count()
            .get_result(conn)
            .map_err(Error::from)
    }

    pub fn count(conn: &Connection) -> Result<i64> {
        posts::table
            .filter(posts::published.eq(true))
            .count()
            .get_result(conn)
            .map_err(Error::from)
    }

    pub fn get_recents(conn: &Connection, limit: i64) -> Result<Vec<Post>> {
        posts::table
            .order(posts::creation_date.desc())
            .filter(posts::published.eq(true))
            .limit(limit)
            .load::<Post>(conn)
            .map_err(Error::from)
    }

    pub fn get_recents_for_author(conn: &Connection, author: &User, limit: i64) -> Result<Vec<Post>> {
        use schema::post_authors;

        let posts = PostAuthor::belonging_to(author).select(post_authors::post_id);
        posts::table
            .filter(posts::id.eq_any(posts))
            .filter(posts::published.eq(true))
            .order(posts::creation_date.desc())
            .limit(limit)
            .load::<Post>(conn)
            .map_err(Error::from)
    }

    pub fn get_recents_for_blog(conn: &Connection, blog: &Blog, limit: i64) -> Result<Vec<Post>> {
        posts::table
            .filter(posts::blog_id.eq(blog.id))
            .filter(posts::published.eq(true))
            .order(posts::creation_date.desc())
            .limit(limit)
            .load::<Post>(conn)
            .map_err(Error::from)
    }

    pub fn get_for_blog(conn: &Connection, blog: &Blog) -> Result<Vec<Post>> {
        posts::table
            .filter(posts::blog_id.eq(blog.id))
            .filter(posts::published.eq(true))
            .load::<Post>(conn)
            .map_err(Error::from)
    }

    pub fn count_for_blog(conn: &Connection, blog: &Blog) -> Result<i64> {
        posts::table
            .filter(posts::blog_id.eq(blog.id))
            .filter(posts::published.eq(true))
            .count()
            .get_result(conn)
            .map_err(Error::from)
    }

    pub fn blog_page(conn: &Connection, blog: &Blog, (min, max): (i32, i32)) -> Result<Vec<Post>> {
        posts::table
            .filter(posts::blog_id.eq(blog.id))
            .filter(posts::published.eq(true))
            .order(posts::creation_date.desc())
            .offset(min.into())
            .limit((max - min).into())
            .load::<Post>(conn)
            .map_err(Error::from)
    }

    /// Give a page of all the recent posts known to this instance (= federated timeline)
    pub fn get_recents_page(conn: &Connection, (min, max): (i32, i32)) -> Result<Vec<Post>> {
        posts::table
            .order(posts::creation_date.desc())
            .filter(posts::published.eq(true))
            .offset(min.into())
            .limit((max - min).into())
            .load::<Post>(conn)
            .map_err(Error::from)
    }

    /// Give a page of posts from a specific instance
    pub fn get_instance_page(
        conn: &Connection,
        instance_id: i32,
        (min, max): (i32, i32),
    ) -> Result<Vec<Post>> {
        use schema::blogs;

        let blog_ids = blogs::table
            .filter(blogs::instance_id.eq(instance_id))
            .select(blogs::id);

        posts::table
            .order(posts::creation_date.desc())
            .filter(posts::published.eq(true))
            .filter(posts::blog_id.eq_any(blog_ids))
            .offset(min.into())
            .limit((max - min).into())
            .load::<Post>(conn)
            .map_err(Error::from)
    }

    /// Give a page of customized user feed, based on a list of followed users
    pub fn user_feed_page(
        conn: &Connection,
        followed: Vec<i32>,
        (min, max): (i32, i32),
    ) -> Result<Vec<Post>> {
        use schema::post_authors;
        let post_ids = post_authors::table
            .filter(post_authors::author_id.eq_any(followed))
            .select(post_authors::post_id);

        posts::table
            .order(posts::creation_date.desc())
            .filter(posts::published.eq(true))
            .filter(posts::id.eq_any(post_ids))
            .offset(min.into())
            .limit((max - min).into())
            .load::<Post>(conn)
            .map_err(Error::from)
    }

    pub fn drafts_by_author(conn: &Connection, author: &User) -> Result<Vec<Post>> {
        use schema::post_authors;

        let posts = PostAuthor::belonging_to(author).select(post_authors::post_id);
        posts::table
            .order(posts::creation_date.desc())
            .filter(posts::published.eq(false))
            .filter(posts::id.eq_any(posts))
            .load::<Post>(conn)
            .map_err(Error::from)
    }

    pub fn get_authors(&self, conn: &Connection) -> Result<Vec<User>> {
        use schema::post_authors;
        use schema::users;
        let author_list = PostAuthor::belonging_to(self).select(post_authors::author_id);
        users::table
            .filter(users::id.eq_any(author_list))
            .load::<User>(conn)
            .map_err(Error::from)
    }

    pub fn is_author(&self, conn: &Connection, author_id: i32) -> Result<bool> {
        use schema::post_authors;
        Ok(PostAuthor::belonging_to(self)
            .filter(post_authors::author_id.eq(author_id))
            .count()
            .get_result::<i64>(conn)? > 0)
    }

    pub fn get_blog(&self, conn: &Connection) -> Result<Blog> {
        use schema::blogs;
        blogs::table
            .filter(blogs::id.eq(self.blog_id))
            .limit(1)
            .load::<Blog>(conn)?
            .into_iter()
            .nth(0)
            .ok_or(Error::NotFound)
    }

    pub fn count_likes(&self, conn: &Connection) -> Result<i64> {
        use schema::likes;
        likes::table
            .filter(likes::post_id.eq(self.id))
            .count()
            .get_result(conn)
            .map_err(Error::from)
    }

    pub fn count_reshares(&self, conn: &Connection) -> Result<i64> {
        use schema::reshares;
        reshares::table
            .filter(reshares::post_id.eq(self.id))
            .count()
            .get_result(conn)
            .map_err(Error::from)
    }

    pub fn update_ap_url(&self, conn: &Connection) -> Result<Post> {
        if self.ap_url.is_empty() {
            diesel::update(self)
                .set(posts::ap_url.eq(self.compute_id(conn)?))
                .execute(conn)?;
            Post::get(conn, self.id)
        } else {
            Ok(self.clone())
        }
    }

    pub fn get_receivers_urls(&self, conn: &Connection) -> Result<Vec<String>> {
        let followers = self
            .get_authors(conn)?
            .into_iter()
            .filter_map(|a| a.get_followers(conn).ok())
            .collect::<Vec<Vec<User>>>();
        Ok(followers.into_iter().fold(vec![], |mut acc, f| {
            for x in f {
                acc.push(x.ap_url);
            }
            acc
        }))
    }

    pub fn to_activity(&self, conn: &Connection) -> Result<LicensedArticle> {
        let cc = self.get_receivers_urls(conn)?;
        let to  = vec![PUBLIC_VISIBILTY.to_string()];

        let mut mentions_json = Mention::list_for_post(conn, self.id)?
            .into_iter()
            .map(|m| json!(m.to_activity(conn).ok()))
            .collect::<Vec<serde_json::Value>>();
        let mut tags_json = Tag::for_post(conn, self.id)?
            .into_iter()
            .map(|t| json!(t.to_activity(conn).ok()))
            .collect::<Vec<serde_json::Value>>();
        mentions_json.append(&mut tags_json);

        let mut article = Article::default();
        article
            .object_props
            .set_name_string(self.title.clone())?;
        article
            .object_props
            .set_id_string(self.ap_url.clone())?;

        let mut authors = self
            .get_authors(conn)?
            .into_iter()
            .map(|x| Id::new(x.ap_url))
            .collect::<Vec<Id>>();
        authors.push(self.get_blog(conn)?.into_id()); // add the blog URL here too
        article
            .object_props
            .set_attributed_to_link_vec::<Id>(authors)?;
        article
            .object_props
            .set_content_string(self.content.get().clone())?;
        article
            .ap_object_props
            .set_source_object(Source {
                content: self.source.clone(),
                media_type: String::from("text/markdown"),
            })?;
        article
            .object_props
            .set_published_utctime(Utc.from_utc_datetime(&self.creation_date))?;
        article
            .object_props
            .set_summary_string(self.subtitle.clone())?;
        article.object_props.tag = Some(json!(mentions_json));

        if let Some(media_id) = self.cover_id {
            let media = Media::get(conn, media_id)?;
            let mut cover = Image::default();
            cover
                .object_props
                .set_url_string(media.url(conn)?)?;
            if media.sensitive {
                cover
                    .object_props
                    .set_summary_string(media.content_warning.unwrap_or_default())?;
            }
            cover
                .object_props
                .set_content_string(media.alt_text)?;
            cover
                .object_props
                .set_attributed_to_link_vec(vec![
                    User::get(conn, media.owner_id)?
                        .into_id(),
                ])?;
            article
                .object_props
                .set_icon_object(cover)?;
        }

        article
            .object_props
            .set_url_string(self.ap_url.clone())?;
        article
            .object_props
            .set_to_link_vec::<Id>(to.into_iter().map(Id::new).collect())?;
        article
            .object_props
            .set_cc_link_vec::<Id>(cc.into_iter().map(Id::new).collect())?;
        let mut license = Licensed::default();
        license.set_license_string(self.license.clone())?;
        Ok(LicensedArticle::new(article, license))
    }

    pub fn create_activity(&self, conn: &Connection) -> Result<Create> {
        let article = self.to_activity(conn)?;
        let mut act = Create::default();
        act.object_props
            .set_id_string(format!("{}activity", self.ap_url))?;
        act.object_props
            .set_to_link_vec::<Id>(
                article.object
                    .object_props
                    .to_link_vec()?,
            )?;
        act.object_props
            .set_cc_link_vec::<Id>(
                article.object
                    .object_props
                    .cc_link_vec()?,
            )?;
        act.create_props
            .set_actor_link(Id::new(self.get_authors(conn)?[0].clone().ap_url))?;
        act.create_props
            .set_object_object(article)?;
        Ok(act)
    }

    pub fn update_activity(&self, conn: &Connection) -> Result<Update> {
        let article = self.to_activity(conn)?;
        let mut act = Update::default();
        act.object_props
            .set_id_string(format!("{}/update-{}", self.ap_url, Utc::now().timestamp()))?;
        act.object_props
            .set_to_link_vec::<Id>(
                article.object
                    .object_props
                    .to_link_vec()?,
            )?;
        act.object_props
            .set_cc_link_vec::<Id>(
                article.object
                    .object_props
                    .cc_link_vec()?,
            )?;
        act.update_props
            .set_actor_link(Id::new(self.get_authors(conn)?[0].clone().ap_url))?;
        act.update_props
            .set_object_object(article)?;
        Ok(act)
    }

    pub fn handle_update(conn: &Connection, updated: &LicensedArticle, searcher: &Searcher) -> Result<()> {
        let id = updated.object
            .object_props
            .id_string()?;
        let mut post = Post::find_by_ap_url(conn, &id)?;

        if let Ok(title) = updated.object.object_props.name_string() {
            post.slug = title.to_kebab_case();
            post.title = title;
        }

        if let Ok(content) = updated.object.object_props.content_string() {
            post.content = SafeString::new(&content);
        }

        if let Ok(subtitle) = updated.object.object_props.summary_string() {
            post.subtitle = subtitle;
        }

        if let Ok(ap_url) = updated.object.object_props.url_string() {
            post.ap_url = ap_url;
        }

        if let Ok(source) = updated.object.ap_object_props.source_object::<Source>() {
            post.source = source.content;
        }

        if let Ok(license) = updated.custom_props.license_string() {
            post.license = license;
        }

        let mut txt_hashtags = md_to_html(&post.source, "")
            .2
            .into_iter()
            .map(|s| s.to_camel_case())
            .collect::<HashSet<_>>();
        if let Some(serde_json::Value::Array(mention_tags)) = updated.object.object_props.tag.clone() {
            let mut mentions = vec![];
            let mut tags = vec![];
            let mut hashtags = vec![];
            for tag in mention_tags {
                serde_json::from_value::<link::Mention>(tag.clone())
                    .map(|m| mentions.push(m))
                    .ok();

                serde_json::from_value::<Hashtag>(tag.clone())
                    .map_err(Error::from)
                    .and_then(|t| {
                        let tag_name = t
                            .name_string()?;
                        if txt_hashtags.remove(&tag_name) {
                            hashtags.push(t);
                        } else {
                            tags.push(t);
                        }
                        Ok(())
                    })
                    .ok();
            }
            post.update_mentions(conn, mentions)?;
            post.update_tags(conn, tags)?;
            post.update_hashtags(conn, hashtags)?;
        }

        post.update(conn, searcher)?;
        Ok(())
    }

    pub fn update_mentions(&self, conn: &Connection, mentions: Vec<link::Mention>) -> Result<()> {
        let mentions = mentions
            .into_iter()
            .map(|m| {
                (
                    m.link_props
                        .href_string()
                        .ok()
                        .and_then(|ap_url| User::find_by_ap_url(conn, &ap_url).ok())
                        .map(|u| u.id),
                    m,
                )
            })
            .filter_map(|(id, m)| {
                if let Some(id) = id {
                    Some((m, id))
                } else {
                    None
                }
            })
            .collect::<Vec<_>>();

        let old_mentions = Mention::list_for_post(&conn, self.id)?;
        let old_user_mentioned = old_mentions
            .iter()
            .map(|m| m.mentioned_id)
            .collect::<HashSet<_>>();
        for (m, id) in &mentions {
            if !old_user_mentioned.contains(&id) {
                Mention::from_activity(&*conn, &m, self.id, true, true)?;
            }
        }

        let new_mentions = mentions
            .into_iter()
            .map(|(_m, id)| id)
            .collect::<HashSet<_>>();
        for m in old_mentions
            .iter()
            .filter(|m| !new_mentions.contains(&m.mentioned_id))
        {
            m.delete(&conn)?;
        }
        Ok(())
    }

    pub fn update_tags(&self, conn: &Connection, tags: Vec<Hashtag>) -> Result<()> {
        let tags_name = tags
            .iter()
            .filter_map(|t| t.name_string().ok())
            .collect::<HashSet<_>>();

        let old_tags = Tag::for_post(&*conn, self.id)?;
        let old_tags_name = old_tags
            .iter()
            .filter_map(|tag| {
                if !tag.is_hashtag {
                    Some(tag.tag.clone())
                } else {
                    None
                }
            })
            .collect::<HashSet<_>>();

        for t in tags {
            if !t
                .name_string()
                .map(|n| old_tags_name.contains(&n))
                .unwrap_or(true)
            {
                Tag::from_activity(conn, &t, self.id, false)?;
            }
        }

        for ot in old_tags.iter().filter(|t| !t.is_hashtag) {
            if !tags_name.contains(&ot.tag) {
                ot.delete(conn)?;
            }
        }
        Ok(())
    }

    pub fn update_hashtags(&self, conn: &Connection, tags: Vec<Hashtag>) -> Result<()> {
        let tags_name = tags
            .iter()
            .filter_map(|t| t.name_string().ok())
            .collect::<HashSet<_>>();

        let old_tags = Tag::for_post(&*conn, self.id)?;
        let old_tags_name = old_tags
            .iter()
            .filter_map(|tag| {
                if tag.is_hashtag {
                    Some(tag.tag.clone())
                } else {
                    None
                }
            })
            .collect::<HashSet<_>>();

        for t in tags {
            if !t
                .name_string()
                .map(|n| old_tags_name.contains(&n))
                .unwrap_or(true)
            {
                Tag::from_activity(conn, &t, self.id, true)?;
            }
        }

        for ot in old_tags.into_iter().filter(|t| t.is_hashtag) {
            if !tags_name.contains(&ot.tag) {
                ot.delete(conn)?;
            }
        }
        Ok(())
    }

    pub fn url(&self, conn: &Connection) -> Result<String> {
        let blog = self.get_blog(conn)?;
        Ok(format!("/~/{}/{}", blog.get_fqn(conn), self.slug))
    }

    pub fn compute_id(&self, conn: &Connection) -> Result<String> {
        Ok(ap_url(&format!(
            "{}/~/{}/{}/",
            BASE_URL.as_str(),
            self.get_blog(conn)?.get_fqn(conn),
            self.slug
        )))
    }

    pub fn cover_url(&self, conn: &Connection) -> Option<String> {
        self.cover_id.and_then(|i| Media::get(conn, i).ok()).and_then(|c| c.url(conn).ok())
    }
}

impl<'a> FromActivity<LicensedArticle, (&'a Connection, &'a Searcher)> for Post {
    type Error = Error;

    fn from_activity((conn, searcher): &(&'a Connection, &'a Searcher), article: LicensedArticle, _actor: Id) -> Result<Post> {
        let license = article.custom_props.license_string().unwrap_or_default();
        let article = article.object;
        if let Ok(post) = Post::find_by_ap_url(
            conn,
            &article.object_props.id_string().unwrap_or_default(),
        ) {
            Ok(post)
        } else {
            let (blog, authors) = article
                .object_props
                .attributed_to_link_vec::<Id>()?
                .into_iter()
                .fold((None, vec![]), |(blog, mut authors), link| {
                    let url: String = link.into();
                    match User::from_url(conn, &url) {
                        Ok(u) => {
                            authors.push(u);
                            (blog, authors)
                        },
                        Err(_) => {
                            (blog.or_else(|| Blog::from_url(conn, &url).ok()), authors)
                        },
                    }
                });

            let cover = article
                .object_props
                .icon_object::<Image>()
                .ok()
                .and_then(|img| Media::from_activity(conn, &img).ok().map(|m| m.id));

            let title = article
                .object_props
                .name_string()?;
            let post = Post::insert(
                conn,
                NewPost {
                    blog_id: blog?.id,
                    slug: title.to_kebab_case(),
                    title,
                    content: SafeString::new(
                        &article
                            .object_props
                            .content_string()?,
                    ),
                    published: true,
                    license: license,
                    // FIXME: This is wrong: with this logic, we may use the display URL as the AP ID. We need two different fields
                    ap_url: article.object_props.url_string().or_else(|_|
                        article
                            .object_props
                            .id_string()
                    )?,
                    creation_date: Some(
                        article
                            .object_props
                            .published_utctime()?
                            .naive_utc(),
                    ),
                    subtitle: article
                        .object_props
                        .summary_string()?,
                    source: article
                        .ap_object_props
                        .source_object::<Source>()?
                        .content,
                    cover_id: cover,
                },
                searcher,
            )?;

            for author in authors {
                PostAuthor::insert(
                    conn,
                    NewPostAuthor {
                        post_id: post.id,
                        author_id: author.id,
                    },
                )?;
            }

            // save mentions and tags
            let mut hashtags = md_to_html(&post.source, "")
                .2
                .into_iter()
                .map(|s| s.to_camel_case())
                .collect::<HashSet<_>>();
            if let Some(serde_json::Value::Array(tags)) = article.object_props.tag.clone() {
                for tag in tags {
                    serde_json::from_value::<link::Mention>(tag.clone())
                        .map(|m| Mention::from_activity(conn, &m, post.id, true, true))
                        .ok();

                    serde_json::from_value::<Hashtag>(tag.clone())
                        .map_err(Error::from)
                        .and_then(|t| {
                            let tag_name = t.name_string()?;
                            Ok(Tag::from_activity(conn, &t, post.id, hashtags.remove(&tag_name)))
                        })
                        .ok();
                }
            }
            Ok(post)
        }
    }
}

impl<'a> Deletable<(&'a Connection, &'a Searcher), Delete> for Post {
    type Error = Error;

    fn delete(&self, (conn, searcher): &(&Connection, &Searcher)) -> Result<Delete> {
        let mut act = Delete::default();
        act.delete_props
            .set_actor_link(self.get_authors(conn)?[0].clone().into_id())?;

        let mut tombstone = Tombstone::default();
        tombstone
            .object_props
            .set_id_string(self.ap_url.clone())?;
        act.delete_props
            .set_object_object(tombstone)?;

        act.object_props
            .set_id_string(format!("{}#delete", self.ap_url))?;
        act.object_props
            .set_to_link_vec(vec![Id::new(PUBLIC_VISIBILTY)])?;

        for m in Mention::list_for_post(&conn, self.id)? {
            m.delete(conn)?;
        }
        diesel::delete(self)
            .execute(*conn)?;
        searcher.delete_document(self);
        Ok(act)
    }

    fn delete_id(id: &str, actor_id: &str, (conn, searcher): &(&Connection, &Searcher)) -> Result<Delete> {
        let actor = User::find_by_ap_url(conn, actor_id)?;
        let post = Post::find_by_ap_url(conn, id)?;
        let can_delete = post.get_authors(conn)?.into_iter().any(|a| actor.id == a.id);
        if can_delete {
            post.delete(&(conn, searcher))
        } else {
            Err(Error::Unauthorized)
        }
    }
}

impl IntoId for Post {
    fn into_id(self) -> Id {
        Id::new(self.ap_url.clone())
    }
}