feat: Refactor user and thought models to use UUIDs instead of integers

- Updated user and thought models to utilize UUIDs for primary keys.
- Modified persistence functions to accommodate UUIDs for user and thought IDs.
- Implemented tag functionality with new Tag and ThoughtTag models.
- Added migration scripts to create new tables for tags and thought-tag relationships.
- Enhanced thought creation to parse hashtags and link them to thoughts.
- Updated tests to reflect changes in user and thought ID types.

thoughts-backend/Cargo.lock

@@ -2408,6 +2408,7 @@ dependencies = [
  "serde",
  "serde_json",
  "utoipa",
+ "uuid",
  "validator",
 ]
 
@@ -4894,6 +4895,7 @@ dependencies = [
  "quote",
  "regex",
  "syn 2.0.104",
+ "uuid",
 ]
 
 [[package]]

thoughts-backend/Cargo.toml

@@ -21,7 +21,7 @@ sea-query = { version = "0.32.6" }                              # Added sea-quer
 serde = { version = "1.0.219", features = ["derive"] }
 serde_json = { version = "1.0.140", features = ["raw_value"] }
 tracing = "0.1.41"
-utoipa = { version = "5.4.0", features = ["macros", "chrono"] }
+utoipa = { version = "5.4.0", features = ["macros", "chrono", "uuid"] }
 validator = { version = "0.20.0", default-features = false }
 chrono = { version = "0.4.41", features = ["serde"] }
 tokio = { version = "1.45.1", features = ["full"] }

thoughts-backend/api/src/extractor/auth.rs

@@ -5,13 +5,14 @@ use axum::{
 
 use jsonwebtoken::{decode, DecodingKey, Validation};
 use once_cell::sync::Lazy;
+use sea_orm::prelude::Uuid;
 use serde::{Deserialize, Serialize};
 
 use app::state::AppState;
 
 #[derive(Debug, Serialize, Deserialize)]
 pub struct Claims {
-    pub sub: i32,
+    pub sub: Uuid,
     pub exp: usize,
 }
 
@@ -19,7 +20,7 @@ static JWT_SECRET: Lazy<String> =
     Lazy::new(|| std::env::var("AUTH_SECRET").expect("AUTH_SECRET must be set"));
 
 pub struct AuthUser {
-    pub id: i32,
+    pub id: Uuid,
 }
 
 impl FromRequestParts<AppState> for AuthUser {
@@ -31,7 +32,7 @@ impl FromRequestParts<AppState> for AuthUser {
     ) -> Result<Self, Self::Rejection> {
         if let Some(user_id_header) = parts.headers.get("x-test-user-id") {
             let user_id_str = user_id_header.to_str().unwrap_or("0");
-            let user_id = user_id_str.parse::<i32>().unwrap_or(0);
+            let user_id = user_id_str.parse::<Uuid>().unwrap_or(Uuid::nil());
             return Ok(AuthUser { id: user_id });
         }
 

thoughts-backend/api/src/routers/mod.rs

@@ -3,6 +3,7 @@ use axum::Router;
 pub mod auth;
 pub mod feed;
 pub mod root;
+pub mod tag;
 pub mod thought;
 pub mod user;
 pub mod well_known;
@@ -25,6 +26,7 @@ pub fn create_router(state: AppState) -> Router {
         .nest("/users", create_user_router())
         .nest("/thoughts", create_thought_router())
         .nest("/feed", create_feed_router())
+        .nest("/tags", tag::create_tag_router())
         .with_state(state)
         .layer(cors)
 }

thoughts-backend/api/src/routers/tag.rs

@@ -0,0 +1,38 @@
+use crate::error::ApiError;
+use app::{persistence::thought::get_thoughts_by_tag_name, state::AppState};
+use axum::{
+    extract::{Path, State},
+    response::IntoResponse,
+    routing::get,
+    Json, Router,
+};
+use models::schemas::thought::{ThoughtListSchema, ThoughtSchema};
+
+#[utoipa::path(
+    get,
+    path = "{tagName}",
+    params(("tagName" = String, Path, description = "Tag name")),
+    responses((status = 200, description = "List of thoughts with a specific tag", body = ThoughtListSchema))
+)]
+async fn get_thoughts_by_tag(
+    State(state): State<AppState>,
+    Path(tag_name): Path<String>,
+) -> Result<impl IntoResponse, ApiError> {
+    let thoughts_with_authors = get_thoughts_by_tag_name(&state.conn, &tag_name).await;
+    println!(
+        "Result from get_thoughts_by_tag_name: {:?}",
+        thoughts_with_authors
+    );
+    let thoughts_with_authors = thoughts_with_authors?;
+    println!("Thoughts with authors: {:?}", thoughts_with_authors);
+    let thoughts_schema: Vec<ThoughtSchema> = thoughts_with_authors
+        .into_iter()
+        .map(ThoughtSchema::from)
+        .collect();
+    println!("Thoughts schema: {:?}", thoughts_schema);
+    Ok(Json(ThoughtListSchema::from(thoughts_schema)))
+}
+
+pub fn create_tag_router() -> Router<AppState> {
+    Router::new().route("/{tag_name}", get(get_thoughts_by_tag))
+}

thoughts-backend/api/src/routers/thought.rs

@@ -12,6 +12,7 @@ use app::{
     state::AppState,
 };
 use models::{params::thought::CreateThoughtParams, schemas::thought::ThoughtSchema};
+use sea_orm::prelude::Uuid;
 
 use crate::{
     error::ApiError,
@@ -74,7 +75,7 @@ async fn thoughts_post(
 async fn thoughts_delete(
     State(state): State<AppState>,
     auth_user: AuthUser,
-    Path(id): Path<i32>,
+    Path(id): Path<Uuid>,
 ) -> Result<impl IntoResponse, ApiError> {
     let thought = get_thought(&state.conn, id)
         .await?

thoughts-backend/api/src/routers/user.rs

@@ -5,6 +5,7 @@ use axum::{
     routing::{get, post},
     Router,
 };
+use sea_orm::prelude::Uuid;
 use serde_json::{json, Value};
 
 use app::persistence::{
@@ -201,7 +202,7 @@ async fn get_user_by_param(
     Path(param): Path<String>,
 ) -> Response {
     // First, try to handle it as a numeric ID.
-    if let Ok(id) = param.parse::<i32>() {
+    if let Ok(id) = param.parse::<Uuid>() {
         return match get_user(&state.conn, id).await {
             Ok(Some(user)) => Json(UserSchema::from(user)).into_response(),
             Ok(None) => ApiError::from(UserError::NotFound).into_response(),

thoughts-backend/app/src/persistence/follow.rs

@@ -1,11 +1,13 @@
-use sea_orm::{ActiveModelTrait, ColumnTrait, DbConn, DbErr, EntityTrait, QueryFilter, Set};
+use sea_orm::{
+    prelude::Uuid, ActiveModelTrait, ColumnTrait, DbConn, DbErr, EntityTrait, QueryFilter, Set,
+};
 
 use crate::{error::UserError, persistence::user::get_user_by_username};
 use models::domains::follow;
 
 pub async fn add_follower(
     db: &DbConn,
-    followed_id: i32,
+    followed_id: Uuid,
     follower_actor_id: &str,
 ) -> Result<(), UserError> {
     let follower_username = follower_actor_id
@@ -25,7 +27,7 @@ pub async fn add_follower(
     Ok(())
 }
 
-pub async fn follow_user(db: &DbConn, follower_id: i32, followed_id: i32) -> Result<(), DbErr> {
+pub async fn follow_user(db: &DbConn, follower_id: Uuid, followed_id: Uuid) -> Result<(), DbErr> {
     if follower_id == followed_id {
         return Err(DbErr::Custom("Users cannot follow themselves".to_string()));
     }
@@ -41,8 +43,8 @@ pub async fn follow_user(db: &DbConn, follower_id: i32, followed_id: i32) -> Res
 
 pub async fn unfollow_user(
     db: &DbConn,
-    follower_id: i32,
+    follower_id: Uuid,
-    followed_id: i32,
+    followed_id: Uuid,
 ) -> Result<(), UserError> {
     let deleted_result = follow::Entity::delete_many()
         .filter(follow::Column::FollowerId.eq(follower_id))
@@ -58,7 +60,7 @@ pub async fn unfollow_user(
     Ok(())
 }
 
-pub async fn get_followed_ids(db: &DbConn, user_id: i32) -> Result<Vec<i32>, DbErr> {
+pub async fn get_followed_ids(db: &DbConn, user_id: Uuid) -> Result<Vec<Uuid>, DbErr> {
     let followed_users = follow::Entity::find()
         .filter(follow::Column::FollowerId.eq(user_id))
         .all(db)
@@ -67,7 +69,7 @@ pub async fn get_followed_ids(db: &DbConn, user_id: i32) -> Result<Vec<i32>, DbE
     Ok(followed_users.into_iter().map(|f| f.followed_id).collect())
 }
 
-pub async fn get_follower_ids(db: &DbConn, user_id: i32) -> Result<Vec<i32>, DbErr> {
+pub async fn get_follower_ids(db: &DbConn, user_id: Uuid) -> Result<Vec<Uuid>, DbErr> {
     let followers = follow::Entity::find()
         .filter(follow::Column::FollowedId.eq(user_id))
         .all(db)

thoughts-backend/app/src/persistence/mod.rs

@@ -1,4 +1,5 @@
 pub mod auth;
 pub mod follow;
+pub mod tag;
 pub mod thought;
 pub mod user;

thoughts-backend/app/src/persistence/tag.rs

@@ -0,0 +1,86 @@
+use models::domains::{tag, thought_tag};
+use sea_orm::{
+    sqlx::types::uuid, ColumnTrait, ConnectionTrait, DbErr, EntityTrait, QueryFilter, Set,
+};
+use std::collections::HashSet;
+
+pub fn parse_hashtags(content: &str) -> Vec<String> {
+    content
+        .split_whitespace()
+        .filter_map(|word| {
+            if word.starts_with('#') && word.len() > 1 {
+                Some(word[1..].to_lowercase().to_string())
+            } else {
+                None
+            }
+        })
+        .collect::<HashSet<_>>()
+        .into_iter()
+        .collect()
+}
+
+pub async fn find_or_create_tags<C>(db: &C, names: Vec<String>) -> Result<Vec<tag::Model>, DbErr>
+where
+    C: ConnectionTrait,
+{
+    if names.is_empty() {
+        return Ok(vec![]);
+    }
+    let existing_tags = tag::Entity::find()
+        .filter(tag::Column::Name.is_in(names.clone()))
+        .all(db)
+        .await?;
+
+    let existing_names: HashSet<String> = existing_tags.iter().map(|t| t.name.clone()).collect();
+    let new_names: Vec<String> = names
+        .into_iter()
+        .filter(|n| !existing_names.contains(n))
+        .collect();
+
+    if !new_names.is_empty() {
+        let new_tags: Vec<tag::ActiveModel> = new_names
+            .clone()
+            .into_iter()
+            .map(|name| tag::ActiveModel {
+                name: Set(name),
+                ..Default::default()
+            })
+            .collect();
+        tag::Entity::insert_many(new_tags).exec(db).await?;
+    }
+
+    tag::Entity::find()
+        .filter(
+            tag::Column::Name.is_in(
+                existing_names
+                    .union(&new_names.into_iter().collect())
+                    .cloned()
+                    .collect::<Vec<_>>(),
+            ),
+        )
+        .all(db)
+        .await
+}
+
+pub async fn link_tags_to_thought<C>(
+    db: &C,
+    thought_id: uuid::Uuid,
+    tags: Vec<tag::Model>,
+) -> Result<(), DbErr>
+where
+    C: ConnectionTrait,
+{
+    if tags.is_empty() {
+        return Ok(());
+    }
+    let links: Vec<thought_tag::ActiveModel> = tags
+        .into_iter()
+        .map(|tag| thought_tag::ActiveModel {
+            thought_id: Set(thought_id),
+            tag_id: Set(tag.id),
+        })
+        .collect();
+
+    thought_tag::Entity::insert_many(links).exec(db).await?;
+    Ok(())
+}

thoughts-backend/app/src/persistence/thought.rs

@@ -1,42 +1,56 @@
 use sea_orm::{
-    ActiveModelTrait, ColumnTrait, DbConn, DbErr, EntityTrait, JoinType, QueryFilter, QueryOrder,
+    prelude::Uuid, ActiveModelTrait, ColumnTrait, DbConn, DbErr, EntityTrait, JoinType,
-    QuerySelect, RelationTrait, Set,
+    QueryFilter, QueryOrder, QuerySelect, RelationTrait, Set, TransactionTrait,
 };
 
 use models::{
-    domains::{thought, user},
+    domains::{tag, thought, thought_tag, user},
     params::thought::CreateThoughtParams,
     schemas::thought::ThoughtWithAuthor,
 };
 
-use crate::error::UserError;
+use crate::{
+    error::UserError,
+    persistence::tag::{find_or_create_tags, link_tags_to_thought, parse_hashtags},
+};
 
 pub async fn create_thought(
     db: &DbConn,
-    author_id: i32,
+    author_id: Uuid,
     params: CreateThoughtParams,
 ) -> Result<thought::Model, DbErr> {
-    thought::ActiveModel {
+    let txn = db.begin().await?;
+
+    let new_thought = thought::ActiveModel {
         author_id: Set(author_id),
-        content: Set(params.content),
+        content: Set(params.content.clone()),
         ..Default::default()
     }
-    .insert(db)
+    .insert(&txn)
-    .await
+    .await?;
+
+    let tag_names = parse_hashtags(&params.content);
+    if !tag_names.is_empty() {
+        let tags = find_or_create_tags(&txn, tag_names).await?;
+        link_tags_to_thought(&txn, new_thought.id, tags).await?;
     }
 
-pub async fn get_thought(db: &DbConn, thought_id: i32) -> Result<Option<thought::Model>, DbErr> {
+    txn.commit().await?;
+    Ok(new_thought)
+}
+
+pub async fn get_thought(db: &DbConn, thought_id: Uuid) -> Result<Option<thought::Model>, DbErr> {
     thought::Entity::find_by_id(thought_id).one(db).await
 }
 
-pub async fn delete_thought(db: &DbConn, thought_id: i32) -> Result<(), DbErr> {
+pub async fn delete_thought(db: &DbConn, thought_id: Uuid) -> Result<(), DbErr> {
     thought::Entity::delete_by_id(thought_id).exec(db).await?;
     Ok(())
 }
 
 pub async fn get_thoughts_by_user(
     db: &DbConn,
-    user_id: i32,
+    user_id: Uuid,
 ) -> Result<Vec<ThoughtWithAuthor>, DbErr> {
     thought::Entity::find()
         .select_only()
@@ -55,7 +69,7 @@ pub async fn get_thoughts_by_user(
 
 pub async fn get_feed_for_user(
     db: &DbConn,
-    followed_ids: Vec<i32>,
+    followed_ids: Vec<Uuid>,
 ) -> Result<Vec<ThoughtWithAuthor>, UserError> {
     if followed_ids.is_empty() {
         return Ok(vec![]);
@@ -76,3 +90,24 @@ pub async fn get_feed_for_user(
         .await
         .map_err(|e| UserError::Internal(e.to_string()))
 }
+
+pub async fn get_thoughts_by_tag_name(
+    db: &DbConn,
+    tag_name: &str,
+) -> Result<Vec<ThoughtWithAuthor>, DbErr> {
+    thought::Entity::find()
+        .select_only()
+        .column(thought::Column::Id)
+        .column(thought::Column::Content)
+        .column(thought::Column::CreatedAt)
+        .column(thought::Column::AuthorId)
+        .column_as(user::Column::Username, "author_username")
+        .join(JoinType::InnerJoin, thought::Relation::User.def())
+        .join(JoinType::InnerJoin, thought::Relation::ThoughtTag.def())
+        .join(JoinType::InnerJoin, thought_tag::Relation::Tag.def())
+        .filter(tag::Column::Name.eq(tag_name.to_lowercase()))
+        .order_by_desc(thought::Column::CreatedAt)
+        .into_model::<ThoughtWithAuthor>()
+        .all(db)
+        .await
+}

thoughts-backend/app/src/persistence/user.rs

@@ -1,8 +1,9 @@
+use sea_orm::prelude::Uuid;
 use sea_orm::{
     ActiveModelTrait, ColumnTrait, DbConn, DbErr, EntityTrait, QueryFilter, Set, TransactionTrait,
 };
 
-use models::domains::user;
+use models::domains::{top_friends, user};
 use models::params::user::{CreateUserParams, UpdateUserParams};
 use models::queries::user::UserQuery;
 
@@ -27,7 +28,7 @@ pub async fn search_users(db: &DbConn, query: UserQuery) -> Result<Vec<user::Mod
         .await
 }
 
-pub async fn get_user(db: &DbConn, id: i32) -> Result<Option<user::Model>, DbErr> {
+pub async fn get_user(db: &DbConn, id: Uuid) -> Result<Option<user::Model>, DbErr> {
     user::Entity::find_by_id(id).one(db).await
 }
 
@@ -41,7 +42,7 @@ pub async fn get_user_by_username(
         .await
 }
 
-pub async fn get_users_by_ids(db: &DbConn, ids: Vec<i32>) -> Result<Vec<user::Model>, DbErr> {
+pub async fn get_users_by_ids(db: &DbConn, ids: Vec<Uuid>) -> Result<Vec<user::Model>, DbErr> {
     user::Entity::find()
         .filter(user::Column::Id.is_in(ids))
         .all(db)
@@ -50,7 +51,7 @@ pub async fn get_users_by_ids(db: &DbConn, ids: Vec<i32>) -> Result<Vec<user::Mo
 
 pub async fn update_user_profile(
     db: &DbConn,
-    user_id: i32,
+    user_id: Uuid,
     params: UpdateUserParams,
 ) -> Result<user::Model, UserError> {
     let mut user: user::ActiveModel = get_user(db, user_id)
@@ -75,26 +76,47 @@ pub async fn update_user_profile(
         user.custom_css = Set(Some(custom_css));
     }
 
-    // This is a complex operation, so we use a transaction
     if let Some(friend_usernames) = params.top_friends {
         let txn = db
             .begin()
             .await
             .map_err(|e| UserError::Internal(e.to_string()))?;
 
-        // 1. Delete old top friends
+        top_friends::Entity::delete_many()
-        // In a real app, you would create a `top_friends` entity and use it here.
+            .filter(top_friends::Column::UserId.eq(user_id))
-        // For now, we'll skip this to avoid creating the model.
+            .exec(&txn)
+            .await
+            .map_err(|e| UserError::Internal(e.to_string()))?;
 
-        // 2. Find new friends by username
+        let friends = user::Entity::find()
-        let _friends = user::Entity::find()
+            .filter(user::Column::Username.is_in(friend_usernames.clone()))
-            .filter(user::Column::Username.is_in(friend_usernames))
             .all(&txn)
             .await
             .map_err(|e| UserError::Internal(e.to_string()))?;
 
-        // 3. Insert new friends
+        if friends.len() != friend_usernames.len() {
-        // This part would involve inserting into the `top_friends` table.
+            return Err(UserError::Validation(
+                "One or more usernames in top_friends do not exist".to_string(),
+            ));
+        }
+
+        let new_top_friends: Vec<top_friends::ActiveModel> = friends
+            .iter()
+            .enumerate()
+            .map(|(index, friend)| top_friends::ActiveModel {
+                user_id: Set(user_id),
+                friend_id: Set(friend.id),
+                position: Set((index + 1) as i16),
+                ..Default::default()
+            })
+            .collect();
+
+        if !new_top_friends.is_empty() {
+            top_friends::Entity::insert_many(new_top_friends)
+                .exec(&txn)
+                .await
+                .map_err(|e| UserError::Internal(e.to_string()))?;
+        }
 
         txn.commit()
             .await

thoughts-backend/migration/src/lib.rs

@@ -3,6 +3,7 @@ pub use sea_orm_migration::prelude::*;
 mod m20240101_000001_init;
 mod m20250905_000001_init;
 mod m20250906_100000_add_profile_fields;
+mod m20250906_130237_add_tags;
 
 pub struct Migrator;
 
@@ -13,6 +14,7 @@ impl MigratorTrait for Migrator {
             Box::new(m20240101_000001_init::Migration),
             Box::new(m20250905_000001_init::Migration),
             Box::new(m20250906_100000_add_profile_fields::Migration),
+            Box::new(m20250906_130237_add_tags::Migration),
         ]
     }
 }

thoughts-backend/migration/src/m20240101_000001_init.rs

@@ -13,10 +13,10 @@ impl MigrationTrait for Migration {
                     .if_not_exists()
                     .col(
                         ColumnDef::new(User::Id)
-                            .integer()
+                            .uuid()
                             .not_null()
-                            .auto_increment()
+                            .primary_key()
-                            .primary_key(),
+                            .default(Expr::cust("gen_random_uuid()")),
                     )
                     .col(
                         ColumnDef::new(User::Username)

thoughts-backend/migration/src/m20250905_000001_init.rs

@@ -13,8 +13,14 @@ impl MigrationTrait for Migration {
                 Table::create()
                     .table(Thought::Table)
                     .if_not_exists()
-                    .col(pk_auto(Thought::Id))
+                    .col(
-                    .col(integer(Thought::AuthorId).not_null())
+                        ColumnDef::new(Thought::Id)
+                            .uuid()
+                            .not_null()
+                            .primary_key()
+                            .default(Expr::cust("gen_random_uuid()")),
+                    )
+                    .col(uuid(Thought::AuthorId).not_null())
                     .foreign_key(
                         ForeignKey::create()
                             .name("fk_thought_author_id")
@@ -39,8 +45,8 @@ impl MigrationTrait for Migration {
                 Table::create()
                     .table(Follow::Table)
                     .if_not_exists()
-                    .col(integer(Follow::FollowerId).not_null())
+                    .col(uuid(Follow::FollowerId).not_null())
-                    .col(integer(Follow::FollowedId).not_null())
+                    .col(uuid(Follow::FollowedId).not_null())
                     // Composite Primary Key to ensure a user can only follow another once
                     .primary_key(
                         Index::create()
@@ -77,7 +83,7 @@ impl MigrationTrait for Migration {
 }
 
 #[derive(DeriveIden)]
-enum Thought {
+pub enum Thought {
     Table,
     Id,
     AuthorId,
@@ -86,7 +92,7 @@ enum Thought {
 }
 
 #[derive(DeriveIden)]
-enum Follow {
+pub enum Follow {
     Table,
     // The user who is initiating the follow
     FollowerId,

thoughts-backend/migration/src/m20250906_100000_add_profile_fields.rs

@@ -36,8 +36,8 @@ impl MigrationTrait for Migration {
                 Table::create()
                     .table(TopFriends::Table)
                     .if_not_exists()
-                    .col(integer(TopFriends::UserId).not_null())
+                    .col(uuid(TopFriends::UserId).not_null())
-                    .col(integer(TopFriends::FriendId).not_null())
+                    .col(uuid(TopFriends::FriendId).not_null())
                     .col(small_integer(TopFriends::Position).not_null())
                     .primary_key(
                         Index::create()

thoughts-backend/migration/src/m20250906_130237_add_tags.rs

@@ -0,0 +1,74 @@
+use super::m20250905_000001_init::Thought;
+use sea_orm_migration::{prelude::*, schema::*};
+
+#[derive(DeriveMigrationName)]
+pub struct Migration;
+
+#[async_trait::async_trait]
+impl MigrationTrait for Migration {
+    async fn up(&self, manager: &SchemaManager) -> Result<(), DbErr> {
+        manager
+            .create_table(
+                Table::create()
+                    .table(Tag::Table)
+                    .if_not_exists()
+                    .col(pk_auto(Tag::Id))
+                    .col(string(Tag::Name).not_null().unique_key())
+                    .to_owned(),
+            )
+            .await?;
+
+        manager
+            .create_table(
+                Table::create()
+                    .table(ThoughtTag::Table)
+                    .if_not_exists()
+                    .col(uuid(ThoughtTag::ThoughtId).not_null())
+                    .col(integer(ThoughtTag::TagId).not_null())
+                    .primary_key(
+                        Index::create()
+                            .col(ThoughtTag::ThoughtId)
+                            .col(ThoughtTag::TagId),
+                    )
+                    .foreign_key(
+                        ForeignKey::create()
+                            .name("fk_thought_tag_thought_id")
+                            .from(ThoughtTag::Table, ThoughtTag::ThoughtId)
+                            .to(Thought::Table, Thought::Id)
+                            .on_delete(ForeignKeyAction::Cascade),
+                    )
+                    .foreign_key(
+                        ForeignKey::create()
+                            .name("fk_thought_tag_tag_id")
+                            .from(ThoughtTag::Table, ThoughtTag::TagId)
+                            .to(Tag::Table, Tag::Id)
+                            .on_delete(ForeignKeyAction::Cascade),
+                    )
+                    .to_owned(),
+            )
+            .await
+    }
+
+    async fn down(&self, manager: &SchemaManager) -> Result<(), DbErr> {
+        manager
+            .drop_table(Table::drop().table(ThoughtTag::Table).to_owned())
+            .await?;
+        manager
+            .drop_table(Table::drop().table(Tag::Table).to_owned())
+            .await
+    }
+}
+
+#[derive(DeriveIden)]
+enum Tag {
+    Table,
+    Id,
+    Name,
+}
+
+#[derive(DeriveIden)]
+enum ThoughtTag {
+    Table,
+    ThoughtId,
+    TagId,
+}

thoughts-backend/models/Cargo.toml

@@ -17,6 +17,7 @@ sea-orm = { workspace = true, features = [
   "runtime-tokio-rustls",
   "macros",
 ] }
+uuid = { version = "1.18.1", features = ["v4", "serde"] }
 validator = { workspace = true, features = ["derive"] }
 utoipa = { workspace = true }
 

thoughts-backend/models/src/domains/follow.rs

@@ -3,10 +3,10 @@ use sea_orm::entity::prelude::*;
 #[derive(Clone, Debug, PartialEq, DeriveEntityModel, Eq)]
 #[sea_orm(table_name = "follow")]
 pub struct Model {
-    #[sea_orm(primary_key)]
+    #[sea_orm(primary_key, auto_increment = false)]
-    pub follower_id: i32,
+    pub follower_id: Uuid,
-    #[sea_orm(primary_key)]
+    #[sea_orm(primary_key, auto_increment = false)]
-    pub followed_id: i32,
+    pub followed_id: Uuid,
 }
 
 #[derive(Copy, Clone, Debug, EnumIter, DeriveRelation)]
@@ -29,4 +29,10 @@ pub enum Relation {
     Followed,
 }
 
+impl Related<super::user::Entity> for Entity {
+    fn to() -> RelationDef {
+        Relation::Follower.def()
+    }
+}
+
 impl ActiveModelBehavior for ActiveModel {}

thoughts-backend/models/src/domains/mod.rs

@@ -3,5 +3,8 @@
 pub mod prelude;
 
 pub mod follow;
+pub mod tag;
 pub mod thought;
+pub mod thought_tag;
+pub mod top_friends;
 pub mod user;

thoughts-backend/models/src/domains/prelude.rs

@@ -1,5 +1,8 @@
 //! `SeaORM` Entity, @generated by sea-orm-codegen 1.0.0
 
 pub use super::follow::Entity as Follow;
+pub use super::tag::Entity as Tag;
 pub use super::thought::Entity as Thought;
+pub use super::thought_tag::Entity as ThoughtTag;
+pub use super::top_friends::Entity as TopFriends;
 pub use super::user::Entity as User;

thoughts-backend/models/src/domains/tag.rs

@@ -0,0 +1,27 @@
+use sea_orm::entity::prelude::*;
+
+#[derive(Clone, Debug, PartialEq, DeriveEntityModel, Eq)]
+#[sea_orm(table_name = "tag")]
+pub struct Model {
+    #[sea_orm(primary_key)]
+    pub id: i32,
+    #[sea_orm(unique)]
+    pub name: String,
+}
+
+#[derive(Copy, Clone, Debug, EnumIter, DeriveRelation)]
+pub enum Relation {
+    #[sea_orm(has_many = "super::thought_tag::Entity")]
+    ThoughtTag,
+}
+
+impl Related<super::thought::Entity> for Entity {
+    fn to() -> RelationDef {
+        super::thought_tag::Relation::Thought.def()
+    }
+    fn via() -> Option<RelationDef> {
+        Some(super::thought_tag::Relation::Tag.def().rev())
+    }
+}
+
+impl ActiveModelBehavior for ActiveModel {}

thoughts-backend/models/src/domains/thought.rs

@@ -3,9 +3,9 @@ use sea_orm::entity::prelude::*;
 #[derive(Clone, Debug, PartialEq, DeriveEntityModel, Eq)]
 #[sea_orm(table_name = "thought")]
 pub struct Model {
-    #[sea_orm(primary_key)]
+    #[sea_orm(primary_key, auto_increment = false)]
-    pub id: i32,
+    pub id: Uuid,
-    pub author_id: i32,
+    pub author_id: Uuid,
     pub content: String,
     pub created_at: DateTimeWithTimeZone,
 }
@@ -20,6 +20,9 @@ pub enum Relation {
         on_delete = "Cascade"
     )]
     User,
+
+    #[sea_orm(has_many = "super::thought_tag::Entity")]
+    ThoughtTag,
 }
 
 impl Related<super::user::Entity> for Entity {
@@ -28,4 +31,13 @@ impl Related<super::user::Entity> for Entity {
     }
 }
 
+impl Related<super::tag::Entity> for Entity {
+    fn to() -> RelationDef {
+        super::thought_tag::Relation::Tag.def()
+    }
+    fn via() -> Option<RelationDef> {
+        Some(super::thought_tag::Relation::Thought.def().rev())
+    }
+}
+
 impl ActiveModelBehavior for ActiveModel {}

thoughts-backend/models/src/domains/thought_tag.rs

@@ -0,0 +1,40 @@
+use sea_orm::entity::prelude::*;
+
+#[derive(Clone, Debug, PartialEq, DeriveEntityModel, Eq)]
+#[sea_orm(table_name = "thought_tag")]
+pub struct Model {
+    #[sea_orm(primary_key, auto_increment = false)]
+    pub thought_id: Uuid,
+    #[sea_orm(primary_key, auto_increment = false)]
+    pub tag_id: i32,
+}
+
+#[derive(Copy, Clone, Debug, EnumIter, DeriveRelation)]
+pub enum Relation {
+    #[sea_orm(
+        belongs_to = "super::thought::Entity",
+        from = "Column::ThoughtId",
+        to = "super::thought::Column::Id"
+    )]
+    Thought,
+    #[sea_orm(
+        belongs_to = "super::tag::Entity",
+        from = "Column::TagId",
+        to = "super::tag::Column::Id"
+    )]
+    Tag,
+}
+
+impl Related<super::thought::Entity> for Entity {
+    fn to() -> RelationDef {
+        Relation::Thought.def()
+    }
+}
+
+impl Related<super::tag::Entity> for Entity {
+    fn to() -> RelationDef {
+        Relation::Tag.def()
+    }
+}
+
+impl ActiveModelBehavior for ActiveModel {}

thoughts-backend/models/src/domains/top_friends.rs

@@ -0,0 +1,35 @@
+use sea_orm::entity::prelude::*;
+
+#[derive(Clone, Debug, PartialEq, DeriveEntityModel, Eq)]
+#[sea_orm(table_name = "top_friends")]
+pub struct Model {
+    #[sea_orm(primary_key, auto_increment = false)]
+    pub user_id: Uuid,
+    #[sea_orm(primary_key, auto_increment = false)]
+    pub friend_id: Uuid,
+    pub position: i16,
+}
+
+#[derive(Copy, Clone, Debug, EnumIter, DeriveRelation)]
+pub enum Relation {
+    #[sea_orm(
+        belongs_to = "super::user::Entity",
+        from = "Column::UserId",
+        to = "super::user::Column::Id"
+    )]
+    User,
+    #[sea_orm(
+        belongs_to = "super::user::Entity",
+        from = "Column::FriendId",
+        to = "super::user::Column::Id"
+    )]
+    Friend,
+}
+
+impl Related<super::user::Entity> for Entity {
+    fn to() -> RelationDef {
+        Relation::User.def()
+    }
+}
+
+impl ActiveModelBehavior for ActiveModel {}

thoughts-backend/models/src/domains/user.rs

@@ -5,8 +5,8 @@ use sea_orm::entity::prelude::*;
 #[derive(Clone, Debug, PartialEq, DeriveEntityModel, Eq)]
 #[sea_orm(table_name = "user")]
 pub struct Model {
-    #[sea_orm(primary_key)]
+    #[sea_orm(primary_key, auto_increment = false)]
-    pub id: i32,
+    pub id: Uuid,
     #[sea_orm(unique)]
     pub username: String,
     pub password_hash: Option<String>,
@@ -22,6 +22,12 @@ pub struct Model {
 }
 
 #[derive(Copy, Clone, Debug, EnumIter, DeriveRelation)]
-pub enum Relation {}
+pub enum Relation {
+    #[sea_orm(has_many = "super::thought::Entity")]
+    Thought,
+
+    #[sea_orm(has_many = "super::top_friends::Entity")]
+    TopFriends,
+}
 
 impl ActiveModelBehavior for ActiveModel {}

thoughts-backend/models/src/schemas/thought.rs

@@ -3,10 +3,11 @@ use common::DateTimeWithTimeZoneWrapper;
 use sea_orm::FromQueryResult;
 use serde::Serialize;
 use utoipa::ToSchema;
+use uuid::Uuid;
 
 #[derive(Serialize, ToSchema, FromQueryResult, Debug)]
 pub struct ThoughtSchema {
-    pub id: i32,
+    pub id: Uuid,
     #[schema(example = "frutiger")]
     pub author_username: String,
     #[schema(example = "This is my first thought! #welcome")]
@@ -38,10 +39,10 @@ impl From<Vec<ThoughtSchema>> for ThoughtListSchema {
 
 #[derive(Debug, FromQueryResult)]
 pub struct ThoughtWithAuthor {
-    pub id: i32,
+    pub id: Uuid,
     pub content: String,
     pub created_at: sea_orm::prelude::DateTimeWithTimeZone,
-    pub author_id: i32,
+    pub author_id: Uuid,
     pub author_username: String,
 }
 

thoughts-backend/models/src/schemas/user.rs

@@ -1,12 +1,13 @@
 use common::DateTimeWithTimeZoneWrapper;
 use serde::Serialize;
 use utoipa::ToSchema;
+use uuid::Uuid;
 
 use crate::domains::user;
 
 #[derive(Serialize, ToSchema)]
 pub struct UserSchema {
-    pub id: i32,
+    pub id: Uuid,
     pub username: String,
     pub display_name: Option<String>,
     pub bio: Option<String>,

thoughts-backend/tests/api/activitypub.rs

@@ -64,9 +64,9 @@ async fn test_user_actor_endpoint() {
 async fn test_user_inbox_follow() {
     let app = setup().await;
     // user1 will be followed
-    create_user_with_password(&app.db, "user1", "password123").await;
+    let user1 = create_user_with_password(&app.db, "user1", "password123").await;
     // user2 will be the follower
-    create_user_with_password(&app.db, "user2", "password123").await;
+    let user2 = create_user_with_password(&app.db, "user2", "password123").await;
 
     // Construct a follow activity from user2, targeting user1
     let follow_activity = json!({
@@ -90,16 +90,19 @@ async fn test_user_inbox_follow() {
     assert_eq!(response.status(), StatusCode::ACCEPTED);
 
     // Verify that user2 is now following user1 in the database
-    let followers = app::persistence::follow::get_followed_ids(&app.db, 2)
+    let followers = app::persistence::follow::get_followed_ids(&app.db, user2.id)
-        .await
-        .unwrap();
-    assert!(followers.contains(&1), "User2 should be following user1");
-
-    let following = app::persistence::follow::get_followed_ids(&app.db, 1)
         .await
         .unwrap();
     assert!(
-        !following.contains(&2),
+        followers.contains(&user1.id),
+        "User2 should be following user1"
+    );
+
+    let following = app::persistence::follow::get_followed_ids(&app.db, user1.id)
+        .await
+        .unwrap();
+    assert!(
+        !following.contains(&user2.id),
         "User1 should now be followed by user2"
     );
     assert!(following.is_empty(), "User1 should not be following anyone");

thoughts-backend/tests/api/auth.rs

@@ -20,7 +20,6 @@ async fn test_auth_flow() {
     let body = response.into_body().collect().await.unwrap().to_bytes();
     let v: Value = serde_json::from_slice(&body).unwrap();
     assert_eq!(v["username"], "testuser");
-    assert!(v["id"].is_number());
 
     let response = make_post_request(
         app.router.clone(),

thoughts-backend/tests/api/main.rs

@@ -1,8 +1,7 @@
 use api::setup_router;
-use app::persistence::user::create_user;
 use axum::Router;
 use http_body_util::BodyExt;
-use models::params::{auth::RegisterParams, user::CreateUserParams};
+use models::{domains::user, params::auth::RegisterParams};
 use sea_orm::DatabaseConnection;
 use serde_json::{json, Value};
 use utils::testing::{make_post_request, setup_test_db};
@@ -35,25 +34,18 @@ pub async fn setup() -> TestApp {
     TestApp { router, db }
 }
 
-// Helper to create users for tests
+pub async fn create_user_with_password(
-pub async fn create_test_user(db: &DatabaseConnection, username: &str) {
+    db: &DatabaseConnection,
-    let params = CreateUserParams {
+    username: &str,
-        username: username.to_string(),
+    password: &str,
-        password: "password".to_string(),
+) -> user::Model {
-    };
-    create_user(db, params)
-        .await
-        .expect("Failed to create test user");
-}
-
-pub async fn create_user_with_password(db: &DatabaseConnection, username: &str, password: &str) {
     let params = RegisterParams {
         username: username.to_string(),
         password: password.to_string(),
     };
     app::persistence::auth::register_user(db, params)
         .await
-        .expect("Failed to create test user with password");
+        .expect("Failed to create test user with password")
 }
 
 pub async fn login_user(router: Router, username: &str, password: &str) -> String {

thoughts-backend/tests/api/mod.rs

@@ -3,5 +3,6 @@ mod auth;
 mod feed;
 mod follow;
 mod main;
+mod tag;
 mod thought;
 mod user;

thoughts-backend/tests/api/tag.rs

@@ -0,0 +1,51 @@
+use crate::api::main::{create_user_with_password, login_user, setup};
+use axum::http::StatusCode;
+use http_body_util::BodyExt;
+use serde_json::{json, Value};
+use utils::testing::{make_get_request, make_jwt_request};
+
+#[tokio::test]
+async fn test_hashtag_flow() {
+    let app = setup().await;
+    let user = create_user_with_password(&app.db, "taguser", "password123").await;
+    let token = login_user(app.router.clone(), "taguser", "password123").await;
+
+    // 1. Post a thought with hashtags
+    let body = json!({ "content": "Hello #world this is a post about #RustLang" }).to_string();
+    let response =
+        make_jwt_request(app.router.clone(), "/thoughts", "POST", Some(body), &token).await;
+    assert_eq!(response.status(), StatusCode::CREATED);
+    let body_bytes = response.into_body().collect().await.unwrap().to_bytes();
+    let thought_json: Value = serde_json::from_slice(&body_bytes).unwrap();
+    let thought_id = thought_json["id"].as_str().unwrap();
+
+    // 2. Post another thought
+    let body2 = json!({ "content": "Another post about the #rustlang ecosystem" }).to_string();
+    make_jwt_request(app.router.clone(), "/thoughts", "POST", Some(body2), &token).await;
+
+    // 3. Fetch thoughts by tag "rustlang"
+    let response = make_get_request(app.router.clone(), "/tags/rustlang", Some(user.id)).await;
+    println!("Response: {:?}", response);
+    assert_eq!(response.status(), StatusCode::OK);
+    let body_bytes = response.into_body().collect().await.unwrap().to_bytes();
+    let v: Value = serde_json::from_slice(&body_bytes).unwrap();
+
+    let thoughts = v["thoughts"].as_array().unwrap();
+    assert_eq!(thoughts.len(), 2);
+    // Note: The most recent post appears first
+    assert_eq!(
+        thoughts[0]["content"],
+        "Another post about the #rustlang ecosystem"
+    );
+    assert_eq!(thoughts[1]["id"], thought_id);
+
+    // 4. Fetch thoughts by tag "world"
+    let response = make_get_request(app.router.clone(), "/tags/world", Some(user.id)).await;
+    assert_eq!(response.status(), StatusCode::OK);
+    let body_bytes = response.into_body().collect().await.unwrap().to_bytes();
+    let v: Value = serde_json::from_slice(&body_bytes).unwrap();
+
+    let thoughts = v["thoughts"].as_array().unwrap();
+    assert_eq!(thoughts.len(), 1);
+    assert_eq!(thoughts[0]["id"], thought_id);
+}

thoughts-backend/tests/api/thought.rs

@@ -1,40 +1,47 @@
-use super::main::{create_test_user, setup};
+use crate::api::main::create_user_with_password;
+
+use super::main::setup;
 use axum::http::StatusCode;
 use http_body_util::BodyExt;
+use sea_orm::prelude::Uuid;
 use serde_json::json;
 use utils::testing::{make_delete_request, make_post_request};
 
 #[tokio::test]
 async fn test_thought_endpoints() {
     let app = setup().await;
-    create_test_user(&app.db, "user1").await; // AuthUser is ID 1
+    let user1 = create_user_with_password(&app.db, "user1", "password123").await; // AuthUser is ID 1
-    create_test_user(&app.db, "user2").await; // Other user is ID 2
+    let _user2 = create_user_with_password(&app.db, "user2", "password123").await; // Other user is ID 2
 
     // 1. Post a new thought as user 1
     let body = json!({ "content": "My first thought!" }).to_string();
-    let response = make_post_request(app.router.clone(), "/thoughts", body, Some(1)).await;
+    let response = make_post_request(app.router.clone(), "/thoughts", body, Some(user1.id)).await;
     assert_eq!(response.status(), StatusCode::CREATED);
     let body = response.into_body().collect().await.unwrap().to_bytes();
     let v: serde_json::Value = serde_json::from_slice(&body).unwrap();
     assert_eq!(v["content"], "My first thought!");
     assert_eq!(v["author_username"], "user1");
-    let thought_id = v["id"].as_i64().unwrap();
+    let thought_id = v["id"].as_str().unwrap().to_string();
 
     // 2. Post a thought with invalid content
     let body = json!({ "content": "" }).to_string(); // Too short
-    let response = make_post_request(app.router.clone(), "/thoughts", body, Some(1)).await;
+    let response = make_post_request(app.router.clone(), "/thoughts", body, Some(user1.id)).await;
     assert_eq!(response.status(), StatusCode::UNPROCESSABLE_ENTITY);
 
     // 3. Attempt to delete another user's thought (user1 tries to delete a non-existent thought, but let's pretend it's user2's)
-    let response =
+    let response = make_delete_request(
-        make_delete_request(app.router.clone(), &format!("/thoughts/999"), Some(1)).await;
+        app.router.clone(),
+        &format!("/thoughts/{}", Uuid::new_v4()),
+        Some(user1.id),
+    )
+    .await;
     assert_eq!(response.status(), StatusCode::NOT_FOUND);
 
     // 4. Delete the thought created in step 1
     let response = make_delete_request(
         app.router.clone(),
         &format!("/thoughts/{}", thought_id),
-        Some(1),
+        Some(user1.id),
     )
     .await;
     assert_eq!(response.status(), StatusCode::NO_CONTENT);

thoughts-backend/tests/api/user.rs

@@ -1,10 +1,12 @@
 use axum::http::StatusCode;
 use http_body_util::BodyExt;
+use models::domains::top_friends;
+use sea_orm::{ColumnTrait, EntityTrait, QueryFilter};
 use serde_json::{json, Value};
 
 use utils::testing::{make_get_request, make_jwt_request, make_post_request};
 
-use crate::api::main::{login_user, setup};
+use crate::api::main::{create_user_with_password, login_user, setup};
 
 #[tokio::test]
 async fn test_post_users() {
@@ -18,7 +20,6 @@ async fn test_post_users() {
     let body = response.into_body().collect().await.unwrap().to_bytes();
     let v: Value = serde_json::from_slice(&body).unwrap();
 
-    assert_eq!(v["id"], 1);
     assert_eq!(v["username"], "test");
     assert!(v["display_name"].is_null());
 }
@@ -54,7 +55,6 @@ pub async fn test_get_users() {
     assert!(v["users"].is_array());
     let users_array = v["users"].as_array().unwrap();
     assert_eq!(users_array.len(), 1);
-    assert_eq!(users_array[0]["id"], 1);
     assert_eq!(users_array[0]["username"], "test");
 }
 
@@ -113,3 +113,73 @@ async fn test_me_endpoints() {
     assert_eq!(v_verify["display_name"], "Me User");
     assert_eq!(v_verify["bio"], "This is my updated bio.");
 }
+
+#[tokio::test]
+async fn test_update_me_top_friends() {
+    let app = setup().await;
+
+    // 1. Create users for the test
+    let user_me = create_user_with_password(&app.db, "me_user", "password123").await;
+    let friend1 = create_user_with_password(&app.db, "friend1", "password123").await;
+    let friend2 = create_user_with_password(&app.db, "friend2", "password123").await;
+    let _friend3 = create_user_with_password(&app.db, "friend3", "password123").await;
+
+    // 2. Log in as "me_user"
+    let token = login_user(app.router.clone(), "me_user", "password123").await;
+
+    // 3. Update profile to set top friends
+    let update_body = json!({
+        "top_friends": ["friend1", "friend2"]
+    })
+    .to_string();
+
+    let response = make_jwt_request(
+        app.router.clone(),
+        "/users/me",
+        "PUT",
+        Some(update_body),
+        &token,
+    )
+    .await;
+    assert_eq!(response.status(), StatusCode::OK);
+
+    // 4. Verify the database state directly
+    let top_friends_list = top_friends::Entity::find()
+        .filter(top_friends::Column::UserId.eq(user_me.id))
+        .all(&app.db)
+        .await
+        .unwrap();
+
+    assert_eq!(top_friends_list.len(), 2);
+    assert_eq!(top_friends_list[0].friend_id, friend1.id);
+    assert_eq!(top_friends_list[0].position, 1);
+    assert_eq!(top_friends_list[1].friend_id, friend2.id);
+    assert_eq!(top_friends_list[1].position, 2);
+
+    // 5. Update again with a different list to test replacement
+    let update_body_2 = json!({
+        "top_friends": ["friend2"]
+    })
+    .to_string();
+
+    let response = make_jwt_request(
+        app.router.clone(),
+        "/users/me",
+        "PUT",
+        Some(update_body_2),
+        &token,
+    )
+    .await;
+    assert_eq!(response.status(), StatusCode::OK);
+
+    // 6. Verify the new state
+    let top_friends_list_2 = top_friends::Entity::find()
+        .filter(top_friends::Column::UserId.eq(user_me.id))
+        .all(&app.db)
+        .await
+        .unwrap();
+
+    assert_eq!(top_friends_list_2.len(), 1);
+    assert_eq!(top_friends_list_2[0].friend_id, friend2.id);
+    assert_eq!(top_friends_list_2[0].position, 1);
+}

thoughts-backend/tests/app/persistence/user.rs

@@ -14,6 +14,5 @@ pub(super) async fn test_user(db: &DatabaseConnection) {
         .try_into_model() // Convert ActiveModel to Model for easier checks
         .unwrap();
 
-    assert_eq!(user_model.id, 1);
     assert_eq!(user_model.username, "test");
 }

thoughts-backend/utils/Cargo.toml

@@ -10,7 +10,7 @@ path = "src/lib.rs"
 
 [dependencies]
 migration = { path = "../migration" }
-uuid = { version = "1.18.1", features = ["v4"] }
+uuid = { version = "1.18.1", features = ["v4", "serde"] }
 sea-orm = { version = "1.1.12", features = ["sqlx-sqlite", "sqlx-postgres"] }
 
 axum = { workspace = true }

thoughts-backend/utils/src/testing/api/mod.rs

@@ -5,8 +5,9 @@ use axum::{
     Router,
 };
 use tower::ServiceExt;
+use uuid::Uuid;
 
-pub async fn make_get_request(app: Router, url: &str, user_id: Option<i32>) -> Response {
+pub async fn make_get_request(app: Router, url: &str, user_id: Option<Uuid>) -> Response {
     let mut builder = Request::builder()
         .uri(url)
         .header("Content-Type", "application/json");
@@ -24,7 +25,7 @@ pub async fn make_post_request(
     app: Router,
     url: &str,
     body: String,
-    user_id: Option<i32>,
+    user_id: Option<Uuid>,
 ) -> Response {
     let mut builder = Request::builder()
         .method("POST")
@@ -40,7 +41,7 @@ pub async fn make_post_request(
         .unwrap()
 }
 
-pub async fn make_delete_request(app: Router, url: &str, user_id: Option<i32>) -> Response {
+pub async fn make_delete_request(app: Router, url: &str, user_id: Option<Uuid>) -> Response {
     let mut builder = Request::builder()
         .method("DELETE")
         .uri(url)