use crate::error::AppError;
use crate::ingestion::ingestion_logic::MonzoRow;
use anyhow::anyhow;
use entity::{expenditure, transaction};
use sea_orm::sea_query::OnConflict;
use sea_orm::{
    ColumnTrait, DatabaseConnection, DbErr, EntityTrait, Iterable, QuerySelect, TransactionTrait,
};
use sea_orm::{ConnectionTrait, DatabaseTransaction, QueryFilter};

pub struct Insertion {
    pub transaction: transaction::ActiveModel,
    pub contained_expenditures: Vec<expenditure::ActiveModel>,
    pub identity_hash: i64,
}

// Note while this is more efficient in db calls, it does bind together the entire group.
// We employ a batching process for now to try balance speed and failure rate, but it is worth
// trying to move failures earlier and improve reporting.
pub async fn insert(
    db: &DatabaseConnection,
    monzo_rows: Vec<MonzoRow>,
    account_id: i32,
) -> Result<Vec<String>, AppError> {
    let mut new_transaction_ids = Vec::new();
    let insertions = monzo_rows
        .into_iter()
        .map(|row| MonzoRow::into_insertion(row, account_id))
        .collect::<Result<Vec<_>, _>>()?;

    for insertions in insertions.chunks(200) {
        let (new_or_updated_insertions, inserted_transaction_ids) =
            whittle_insertions(insertions, db).await?;

        if new_or_updated_insertions.is_empty() {
            continue;
        }

        let tx = db.begin().await?;
        update_transactions(&tx, &new_or_updated_insertions).await?;
        update_expenditures(&tx, &new_or_updated_insertions, &inserted_transaction_ids).await?;
        tx.commit().await?;

        // We wait until the transaction is committed before adding the new transaction ids to the
        // list to avoid issues with the transaction being rolled back.
        new_transaction_ids.extend(inserted_transaction_ids);
    }

    // Notify the new transactions once everything is committed.
    notify_new_transactions(db, &new_transaction_ids).await?;

    Ok(new_transaction_ids)
}

async fn update_expenditures(
    tx: &DatabaseTransaction,
    new_or_updated_insertions: &[&Insertion],
    inserted_transaction_ids: &[String],
) -> Result<(), AppError> {
    if new_or_updated_insertions.is_empty() {
        return Ok(());
    }

    // Expenditures can change as we re-categorise them, so we delete all the old ones and
    // insert an entirely new set to ensure we don't end up leaving old ones around.
    expenditure::Entity::delete_many()
        .filter(expenditure::Column::TransactionId.is_in(inserted_transaction_ids))
        .exec(tx)
        .await?;

    expenditure::Entity::insert_many(
        new_or_updated_insertions
            .iter()
            .flat_map(|i| &i.contained_expenditures)
            .cloned(),
    )
    .on_conflict(
        OnConflict::columns(vec![
            expenditure::Column::TransactionId,
            expenditure::Column::Category,
        ])
        .update_columns(expenditure::Column::iter())
        .to_owned(),
    )
    .exec(tx)
    .await?;
    Ok(())
}

async fn update_transactions(
    tx: &DatabaseTransaction,
    new_or_updated_insertions: &[&Insertion],
) -> Result<(), DbErr> {
    if new_or_updated_insertions.is_empty() {
        return Ok(());
    }

    let transactions = new_or_updated_insertions
        .iter()
        .map(|i| &i.transaction)
        .cloned();

    transaction::Entity::insert_many(transactions)
        .on_conflict(
            OnConflict::column(transaction::Column::Id)
                .update_columns(transaction::Column::iter())
                .to_owned(),
        )
        .exec(tx)
        .await?;
    Ok(())
}

async fn whittle_insertions<'a>(
    insertions: &'a [Insertion],
    tx: &DatabaseConnection,
) -> Result<(Vec<&'a Insertion>, Vec<String>), AppError> {
    let existing_hashes = transaction::Entity::find()
        .select_only()
        .columns([transaction::Column::IdentityHash])
        .filter(transaction::Column::IdentityHash.is_not_null())
        .into_tuple::<(i64,)>()
        .all(tx)
        .await?;

    tracing::debug!("Found existing entries: {existing_hashes:?}");

    // We will only update those where the hash is different to avoid unnecessary updates and
    // notifications.
    let new_or_updated_insertions = insertions
        .iter()
        .filter(|i| {
            let hash = i.identity_hash;
            !existing_hashes
                .iter()
                .any(|(existing_hash,)| *existing_hash == hash)
        })
        .collect::<Vec<_>>();

    let inserted_transaction_ids = new_or_updated_insertions
        .iter()
        .map(|i| i.transaction.id.clone().unwrap())
        .collect::<Vec<_>>();

    Ok((new_or_updated_insertions, inserted_transaction_ids))
}

async fn notify_new_transactions(
    db: &DatabaseConnection,
    new_transaction_ids: &[String],
) -> Result<(), AppError> {
    let payload = serde_json::to_string(&new_transaction_ids).map_err(|e| anyhow!(e))?;

    db.execute_unprepared(&format!(r#"NOTIFY monzo_new_transactions, '{payload}'"#))
        .await?;

    Ok(())
}

mod tests {
    use super::{insert, notify_new_transactions, update_expenditures, update_transactions};
    use crate::ingestion::ingestion_logic::from_json_row;
    use anyhow::Error;
    use entity::account;
    use migration::MigratorTrait;
    use sea_orm::{ActiveModelTrait, DatabaseConnection, TransactionTrait};
    use serde_json::Value;
    use sqlx::postgres::PgListener;
    use sqlx::{Executor, PgPool};
    use testcontainers::runners::AsyncRunner;
    use testcontainers::ContainerAsync;
    use tokio::sync::OnceCell;

    #[derive(Debug)]
    struct DatabaseInstance {
        container: ContainerAsync<testcontainers_modules::postgres::Postgres>,
        db: DatabaseConnection,
        pool: PgPool,
    }

    static INSTANCE: OnceCell<DatabaseInstance> = OnceCell::const_new();

    async fn initialise_db() -> Result<DatabaseInstance, Error> {
        let container = testcontainers_modules::postgres::Postgres::default()
            .start()
            .await?;

        // prepare connection string
        let connection_string = &format!(
            "postgres://postgres:postgres@127.0.0.1:{}/postgres",
            container.get_host_port_ipv4(5432).await?
        );

        let db: DatabaseConnection = sea_orm::Database::connect(connection_string).await?;
        migration::Migrator::up(&db, None).await?;

        let pool = PgPool::connect(connection_string).await?;
        let instance = DatabaseInstance {
            container,
            db,
            pool,
        };

        Ok(instance)
    }

    async fn get_or_initialize_db_instance() -> Result<&'static DatabaseInstance, Error> {
        Ok(INSTANCE
            .get_or_init(|| async { initialise_db().await.unwrap() })
            .await)
    }

    async fn create_test_account(db: &DatabaseConnection) -> Result<i32, Error> {
        let new_account = account::ActiveModel {
            id: sea_orm::ActiveValue::NotSet,
            name: sea_orm::ActiveValue::Set("Test Account".to_string()),
        };
        let inserted = new_account.insert(db).await?;
        Ok(inserted.id)
    }

    #[tokio::test]
    async fn test_empty_insertion_list() -> Result<(), Error> {
        let db = get_or_initialize_db_instance().await?;
        let insertions = vec![];
        let tx = db.db.begin().await?;
        update_transactions(&tx, &insertions).await?;
        update_expenditures(&tx, &insertions, &vec![]).await?;
        tx.commit().await?;

        Ok(())
    }

    #[tokio::test]
    async fn test_notify() -> Result<(), Error> {
        let dbi = get_or_initialize_db_instance().await?;
        let mut listener = PgListener::connect_with(&dbi.pool).await?;
        listener.listen("monzo_new_transactions").await?;

        let ids = vec![
            "test1".to_string(),
            "test2".to_string(),
            "test3".to_string(),
        ];

        notify_new_transactions(&dbi.db, &ids).await?;

        let notification = listener.recv().await?;
        let payload = notification.payload();
        println!("Payload: {}", payload);
        assert_eq!(
            serde_json::from_str::<Vec<String>>(&payload)?,
            ids,
            "Payloads do not match"
        );

        Ok(())
    }

    #[tokio::test]
    async fn test_notify_on_insert() -> Result<(), Error> {
        let dbi = get_or_initialize_db_instance().await?;
        let account_id = create_test_account(&dbi.db).await?;
        let mut listener = PgListener::connect_with(&dbi.pool).await?;
        listener.listen("monzo_new_transactions").await?;

        let json = include_str!("../../fixtures/transactions.json");
        let json: Vec<Vec<Value>> = serde_json::from_str(json).unwrap();
        let data = json
            .iter()
            .map(|row| from_json_row(row))
            .collect::<Result<Vec<_>, anyhow::Error>>()?;

        insert(&dbi.db, data.clone(), account_id).await?;
        let notification = listener.recv().await?;
        let payload = notification.payload();
        let mut payload = serde_json::from_str::<Vec<String>>(&payload)?;
        payload.sort();

        let mut ids = data
            .iter()
            .map(|row| row.transaction_id.clone())
            .collect::<Vec<_>>();

        ids.sort();

        assert_eq!(payload, ids, "Inserted IDs do not match");

        insert(&dbi.db, data.clone(), account_id).await?;
        let notification = listener.recv().await?;
        let payload = notification.payload();
        let payload = serde_json::from_str::<Vec<String>>(&payload)?;
        assert_eq!(
            payload,
            Vec::<String>::new(),
            "Re-inserting identical rows triggered double notification"
        );

        let mut altered_data = data.clone();
        altered_data[0].description = Some("New description".to_string());

        assert_ne!(
            altered_data[0].compute_hash(),
            data[0].compute_hash(),
            "Alterations have the same hash"
        );

        insert(&dbi.db, altered_data.clone(), account_id).await?;
        let notification = listener.recv().await?;
        let payload = notification.payload();
        let payload = serde_json::from_str::<Vec<String>>(&payload)?;
        assert_eq!(
            payload,
            vec![altered_data[0].transaction_id.clone()],
            "Re-inserting altered row failed to re-trigger notification"
        );

        Ok(())
    }
}

pub(crate) async fn get_account_id(
    p0: &DatabaseConnection,
    p1: Option<String>,
) -> Result<i32, AppError> {
    let p1 = p1.unwrap_or("Monzo".to_string());

    entity::prelude::Account::find()
        .filter(entity::account::Column::Name.eq(p1))
        .select_only()
        .column(entity::account::Column::Id)
        .into_tuple::<i32>()
        .one(p0)
        .await?
        .ok_or(AppError::BadRequest(anyhow!("Account not found")))
}