use sea_orm_migration::{prelude::*, sea_orm::ConnectionTrait, sea_query::Expr};

#[derive(DeriveMigrationName)]
pub struct Migration;

#[derive(DeriveIden)]
enum UserRoles {
    Table,
    UserId,
    Role,
    AssignedBy,
    AssignedAt,
}

#[derive(DeriveIden)]
enum Users {
    Table,
    Id,
}

#[async_trait::async_trait]
impl MigrationTrait for Migration {
    async fn up(&self, m: &SchemaManager) -> Result<(), DbErr> {
        m.create_table(
            Table::create()
                .table(UserRoles::Table)
                .if_not_exists()
                .col(ColumnDef::new(UserRoles::UserId).integer().not_null())
                .col(ColumnDef::new(UserRoles::Role).string_len(50).not_null())
                .col(ColumnDef::new(UserRoles::AssignedBy).integer().null())
                .col(
                    ColumnDef::new(UserRoles::AssignedAt)
                        .timestamp_with_time_zone()
                        .not_null()
                        .default(Expr::current_timestamp()),
                )
                .primary_key(
                    Index::create()
                        .name("pk-user_roles")
                        .col(UserRoles::UserId)
                        .col(UserRoles::Role),
                )
                .foreign_key(
                    ForeignKey::create()
                        .name("fk-user_roles-user_id-to-users")
                        .from(UserRoles::Table, UserRoles::UserId)
                        .to(Users::Table, Users::Id)
                        .on_delete(ForeignKeyAction::Cascade)
                        .on_update(ForeignKeyAction::Cascade),
                )
                .foreign_key(
                    ForeignKey::create()
                        .name("fk-user_roles-assigned_by-to-users")
                        .from(UserRoles::Table, UserRoles::AssignedBy)
                        .to(Users::Table, Users::Id)
                        .on_delete(ForeignKeyAction::SetNull)
                        .on_update(ForeignKeyAction::NoAction),
                )
                .to_owned(),
        )
        .await?;

        m.create_index(
            Index::create()
                .name("idx-user_roles-user_id")
                .table(UserRoles::Table)
                .col(UserRoles::UserId)
                .to_owned(),
        )
        .await?;

        let sql = match m.get_database_backend() {
            sea_orm_migration::sea_orm::DatabaseBackend::Postgres => {
                "INSERT INTO user_roles (user_id, role, assigned_at) \
                 SELECT id, 'user', CURRENT_TIMESTAMP FROM users \
                 ON CONFLICT (user_id, role) DO NOTHING"
            }
            sea_orm_migration::sea_orm::DatabaseBackend::Sqlite => {
                "INSERT OR IGNORE INTO user_roles (user_id, role, assigned_at) \
                 SELECT id, 'user', CURRENT_TIMESTAMP FROM users"
            }
            sea_orm_migration::sea_orm::DatabaseBackend::MySql => {
                "INSERT IGNORE INTO user_roles (user_id, role, assigned_at) \
                 SELECT id, 'user', CURRENT_TIMESTAMP FROM users"
            }
        };
        m.get_connection().execute_unprepared(sql).await?;

        Ok(())
    }

    async fn down(&self, m: &SchemaManager) -> Result<(), DbErr> {
        m.drop_table(Table::drop().table(UserRoles::Table).to_owned())
            .await?;
        Ok(())
    }
}