db-library 0.1.2

//! PostgreSQL Table Listener
//!
//! This module provides `PostgresTableListener`, which listens for changes in specified database tables.
//! It uses PostgreSQL triggers and `LISTEN/NOTIFY` to capture and relay events asynchronously.
//!
//! # Features
//! - Monitors specified tables for `INSERT`, `UPDATE`, and `DELETE` operations.
//! - Captures changes at the column level.
//! - Uses PostgreSQL triggers and functions for efficient event detection.
//! - Sends notifications through async channels.
//! - Provides a structured API to start and stop listeners.
//!
//! # Dependencies
//! - `sqlx` for database interaction
//! - `tokio` for async execution
//! - `serde` and `serde_json` for JSON serialization
//! - `tracing` for logging

use async_trait::async_trait;
use once_cell::sync::Lazy;
use serde::{Deserialize, Serialize};
use serde_json::Value;
use sqlx::{
    postgres::{PgListener, PgNotification, PgPoolOptions},
    Executor, PgPool,
};
use std::{collections::HashMap, sync::Arc, time::Duration};
use tokio::{
    sync::{
        mpsc::{self, Receiver, Sender},
        Mutex, RwLock,
    },
    task::JoinHandle,
};
use tracing::{error, info};

use crate::config::DBListenerError;

use super::{DBListenerTrait, EventType};

static PG_POOL_REGISTRY: Lazy<RwLock<HashMap<String, Arc<PgPool>>>> =
    Lazy::new(|| RwLock::new(HashMap::new()));

async fn get_or_create_pool(db_url: &str) -> Result<Arc<PgPool>, DBListenerError> {
    // acquiring read lock first to check the existence of pool.
    {
        let pools = PG_POOL_REGISTRY.read().await;

        if let Some(pool) = pools.get(db_url) {
            return Ok(Arc::clone(pool));
        }
    }

    let mut pools = PG_POOL_REGISTRY.write().await;

    if let Some(pool) = pools.get(db_url) {
        Ok(Arc::clone(pool))
    } else {
        let new_pool = PgPoolOptions::new()
            .max_connections(10)
            .acquire_timeout(Duration::from_secs(2))
            .connect(db_url)
            .await;

        if let Err(e) = new_pool {
            error!("Failed to connect to the database: {:?}", e);
            return Err(DBListenerError::CreationError(format!(
                "Failed to connect to the database url : {:#?}",
                e
            )));
        }
        let new_pool = Arc::new(new_pool.unwrap());
        pools.insert(db_url.to_string(), Arc::clone(&new_pool));
        Ok(new_pool)
    }
}

#[derive(Debug, Clone)]
pub struct PostgresTableListener {
    pub pool: Arc<PgPool>,
    pub table_name: String,
    pub columns: Vec<String>,
    pub sender: Sender<Value>,
    pub receiver: Arc<Mutex<tokio::sync::mpsc::Receiver<Value>>>,
    pub table_identifier: String,
    pub pg_trigger_name: String,
    pub pg_function_name: String,
    pub pg_column_updates_name: String,
    pub events: Vec<EventType>,
}

impl PostgresTableListener {
    pub async fn new(
        url: &str,
        table_name: &str,
        columns: Vec<String>,
        table_identifier: &str,
        events: Vec<EventType>,
    ) -> Result<Self, DBListenerError> {
        let pool = get_or_create_pool(url).await?;

        let uniquekey_uuid = uuid::Uuid::new_v4().to_string();
        let uniquekey = uniquekey_uuid.replace("-", "_");

        let pg_trigger_name = format!("{}_{}_trigger", table_name, &uniquekey);
        let pg_function_name = format!("{}_{}_function", table_name, &uniquekey);
        let pg_column_updates_name = format!("{}_{}_column_updates", table_name, &uniquekey);

        let (sender, receiver) = mpsc::channel::<Value>(100); // Channel with buffer size 100

        let postgres_table_listener = Self {
            pool,
            table_name: table_name.to_string(),
            columns: columns.into_iter().map(|c| c.to_string()).collect(),
            table_identifier: table_identifier.to_string(),
            sender,
            receiver: Arc::new(Mutex::new(receiver)),
            pg_trigger_name,
            pg_function_name,
            pg_column_updates_name,
            events,
        };

        postgres_table_listener.verify_members().await?;

        Ok(postgres_table_listener)
    }

    async fn verify_members(&self) -> Result<(), DBListenerError> {
        info!("--> Verifying table and columns");
        // Verify that the table exists
        let table_exists = sqlx::query_as::<_, (bool,)>(
            r#"
            SELECT EXISTS (
                SELECT 1
                FROM information_schema.tables
                WHERE table_name = $1
            );
            "#,
        )
        .bind(&self.table_name)
        .fetch_one(&*self.pool)
        .await
        .map_err(|e| {
            DBListenerError::ListenerVerifyError(format!(
                "Failed to verify table existence : {:?}",
                e
            ))
        })?;

        info!("table exists : {:#?}", table_exists);

        if !table_exists.0 {
            return Err(DBListenerError::ListenerVerifyError(format!(
                "Table '{}' does not exist",
                &self.table_name
            )));
        }

        // verify all columns exist
        for column in &self.columns {
            let column_exists = sqlx::query_as::<_, (bool,)>(
                r#"
                SELECT EXISTS (
                    SELECT 1
                    FROM information_schema.columns
                    WHERE table_name = $1
                    AND column_name = $2
                );
                "#,
            )
            .bind(&self.table_name)
            .bind(column)
            .fetch_one(&*self.pool)
            .await
            .map_err(|e| {
                DBListenerError::ListenerVerifyError(format!(
                    "Failed to verify column existence '{}': {:?}",
                    column, e
                ))
            })?;

            if !column_exists.0 {
                return Err(DBListenerError::ListenerVerifyError(format!(
                    "Column '{}' does not exist",
                    column
                )));
            }
        }

        // Verify that the table identifier exists
        let table_identifier_exists = sqlx::query_as::<_, (bool,)>(
            r#"
            SELECT EXISTS (
                SELECT 1
                FROM information_schema.columns
                WHERE table_name = $1
                AND column_name = $2
            );
            "#,
        )
        .bind(&self.table_name)
        .bind(&self.table_identifier)
        .fetch_one(&*self.pool)
        .await
        .map_err(|e| {
            DBListenerError::ListenerVerifyError(format!(
                "Failed to verify table identifier '{}': {:?}",
                &self.table_identifier, e
            ))
        })?;

        if !table_identifier_exists.0 {
            return Err(DBListenerError::ListenerVerifyError(format!(
                "Table identifier '{}' does not exist",
                &self.table_identifier
            )));
        }

        info!("✅ Table and columns verified successfully");
        Ok(())
    }

    async fn create_trigger_and_function(&self) -> Result<(), DBListenerError> {
        let table_identifier = &self.table_identifier;

        // Create the function with clean INSERT handling
        let create_function = format!(
            r#"
                CREATE OR REPLACE FUNCTION {function_name}()
                RETURNS TRIGGER AS $$
                BEGIN
                    IF TG_OP = 'INSERT' THEN 
                        {insert_blocks}
                    ELSIF TG_OP = 'UPDATE' THEN 
                        {update_blocks}
                    ELSIF TG_OP = 'DELETE' THEN
                        {delete_blocks}
                    END IF;
                    RETURN NEW;
                END;
                $$ LANGUAGE plpgsql;
            "#,
            function_name = self.pg_function_name,
            insert_blocks = self
                .columns
                .iter()
                .map(|col| {
                    format!(
                        r#"
                        IF NEW.{col} IS NOT NULL THEN
                            PERFORM pg_notify(
                                '{column_updates}',
                                json_build_object(
                                    'operation', TG_OP,
                                    'table', TG_TABLE_NAME,
                                    'column', '{col}',
                                    'id', NEW.{table_identifier},
                                    'new_value', NEW.{col},
                                    'timestamp', NOW(),
                                    'new_row_data', row_to_json(NEW)
                                )::text
                            );
                        END IF;
                    "#,
                        column_updates = self.pg_column_updates_name
                    )
                })
                .collect::<Vec<_>>()
                .join("\n"),
            update_blocks = self
                .columns
                .iter()
                .map(|col| {
                    format!(
                        r#"
                        IF NEW.{col} IS DISTINCT FROM OLD.{col} THEN
                            PERFORM pg_notify(
                                '{column_updates}',
                                json_build_object(
                                    'operation', TG_OP,
                                    'table', TG_TABLE_NAME,
                                    'column', '{col}',
                                    'id', NEW.{table_identifier},
                                    'old_value', OLD.{col},
                                    'new_value', NEW.{col},
                                    'timestamp', NOW(),
                                    'old_row_data', row_to_json(OLD),
                                    'new_row_data', row_to_json(NEW)
                                )::text
                            );
                        END IF;
                    "#,
                        column_updates = self.pg_column_updates_name,
                    )
                })
                .collect::<Vec<_>>()
                .join("\n"),
            delete_blocks = self
                .columns
                .iter()
                .map(|col| {
                    format!(
                        r#"
                        IF OLD.{col} IS NOT NULL THEN
                            PERFORM pg_notify(
                                '{column_updates}',
                                json_build_object(
                                    'operation', TG_OP,
                                    'table', TG_TABLE_NAME,
                                    'column', '{col}',
                                    'id', OLD.{table_identifier},
                                    'old_value', OLD.{col},
                                    'timestamp', NOW(),
                                    'old_row_data', row_to_json(OLD)
                                )::text
                            );
                        END IF;
                    "#,
                        column_updates = self.pg_column_updates_name,
                    )
                })
                .collect::<Vec<_>>()
                .join("\n"),
        );

        // Execute function creation
        self.pool
            .execute(create_function.as_str())
            .await
            .map_err(|e| {
                DBListenerError::CreationError(format!(
                    "Failed to execute function creation : {:#?}",
                    e
                ))
            })?;

        let events_list = self.get_events_list();

        let create_trigger = format!(
            r#"
                DO $$ 
                BEGIN 
                    IF NOT EXISTS (
                        SELECT 1 
                        FROM pg_trigger 
                        WHERE tgname = '{trigger_name}'
                    ) THEN 
                        CREATE TRIGGER {trigger_name}
                        AFTER {events_list} ON {table_name} 
                        FOR EACH ROW
                        EXECUTE FUNCTION {function_name}();
                    END IF;
                END $$;
            "#,
            trigger_name = self.pg_trigger_name,
            events_list = events_list,
            table_name = self.table_name,
            function_name = self.pg_function_name
        );

        // Execute trigger creation
        self.pool
            .execute(create_trigger.as_str())
            .await
            .map_err(|e| {
                DBListenerError::CreationError(format!(
                    "Failed to execute trigger creation : {:#?}",
                    e
                ))
            })?;

        Ok(())
    }

    fn get_events_list(&self) -> String {
        self.events
            .iter()
            .map(|event| match event {
                EventType::INSERT => "INSERT".to_string(),
                EventType::UPDATE => format!("UPDATE OF {}", self.columns.join(", ")),
                EventType::DELETE => "DELETE".to_string(),
            })
            .collect::<Vec<_>>()
            .join(" OR ")
    }

    async fn drop_trigger_and_function(&self) -> Result<(), DBListenerError> {
        let trigger_name = &self.pg_trigger_name;
        let function_name = &self.pg_function_name;
        let table_name = &self.table_name;

        // Drop the trigger if it exists
        let drop_trigger = format!(
            r#"
            DO $$
            BEGIN
                IF EXISTS (
                    SELECT 1
                    FROM pg_trigger
                    WHERE tgname = '{trigger_name}'
                ) THEN
                    DROP TRIGGER {trigger_name} ON {table_name};
                END IF;
            END $$;
            "#,
            trigger_name = trigger_name,
            table_name = table_name
        );

        self.pool
            .execute(drop_trigger.as_str())
            .await
            .map_err(|e| {
                DBListenerError::DeletionError(format!(
                    "Failed to execute trigger deletion : {:#?}",
                    e
                ))
            })?;

        // Drop the function if it exists
        let drop_function = format!(
            r#"
            DO $$
            BEGIN
                IF EXISTS (
                    SELECT 1
                    FROM pg_proc
                    WHERE proname = '{function_name}'
                ) THEN
                    DROP FUNCTION {function_name}();
                END IF;
            END $$;
            "#,
            function_name = function_name
        );

        self.pool
            .execute(drop_function.as_str())
            .await
            .map_err(|e| {
                DBListenerError::DeletionError(format!(
                    "Failed to execute trigger deletion : {:#?}",
                    e
                ))
            })?;

        info!("Trigger and function removed for table: {}", table_name);
        Ok(())
    }

    async fn initialize_listener(&self) -> Result<Arc<Mutex<PgListener>>, DBListenerError> {
        // Create trigger and function if they don't exist
        self.create_trigger_and_function()
            .await
            .map_err(|e| DBListenerError::ListenerError(e.to_string()))?;

        // Initialize and configure the listener
        let listener = PgListener::connect_with(&self.pool)
            .await
            .map_err(|e| DBListenerError::ListenerError(e.to_string()))?;

        let listener = Arc::new(Mutex::new(listener));

        // Start listening for notifications
        {
            let mut locked_listener = listener.lock().await;
            locked_listener
                .listen(&self.pg_column_updates_name)
                .await
                .map_err(|e| DBListenerError::ListenerError(e.to_string()))?;
        }

        info!(
            "Listening for column update notifications on {}",
            self.table_name
        );

        Ok(listener)
    }

    fn spawn_listener_task(&self, listener: Arc<Mutex<PgListener>>) -> JoinHandle<()> {
        let sender_clone = self.sender.clone();
        let table_name = self.table_name.clone();

        tokio::spawn(async move {
            info!("Listener spawned and waiting for notifications");

            loop {
                let mut locked_listener = listener.lock().await;
                match locked_listener.recv().await {
                    Ok(notification) => {
                        if let Some(pg_notify) = process_notification(&notification, &table_name) {
                            // Convert PgNotify to Value and send
                            if let Ok(json_data) = serde_json::to_value(pg_notify) {
                                if let Err(e) = sender_clone.send(json_data).await {
                                    error!("Failed to send payload to channel: {:?}", e);
                                }
                            } else {
                                error!("Failed to serialize PgNotify to JSON");
                            }
                        }
                    }
                    Err(e) => {
                        error!("Listener encountered an error: {:?}", e);
                        break;
                    }
                }
            }
        })
    }
}

#[async_trait]
impl DBListenerTrait for PostgresTableListener {
    async fn start(
        &self,
    ) -> Result<(Arc<Mutex<Receiver<Value>>>, JoinHandle<()>), DBListenerError> {
        let listener = self.initialize_listener().await?;

        let handle = self.spawn_listener_task(listener);

        Ok((Arc::clone(&self.receiver), handle))
    }

    async fn stop(&self) -> Result<(), DBListenerError> {
        self.drop_trigger_and_function()
            .await
            .map_err(|e| DBListenerError::ListenerError(e.to_string()))?;
        Ok(())
    }
}

fn process_notification(notification: &PgNotification, table_name: &str) -> Option<PgNotify> {
    match serde_json::from_str::<Value>(&notification.payload()) {
        Ok(payload) => Some(PgNotify {
            operation: payload
                .get("operation")
                .and_then(|v| v.as_str().map(String::from))
                .unwrap_or_default(),
            table: table_name.to_string(),
            column: payload
                .get("column")
                .and_then(|v| v.as_str().map(String::from))
                .unwrap_or_default(),
            id: payload.get("id").map(|v| v.to_string()).unwrap_or_default(),
            new_row_data: payload
                .get("new_row_data")
                .cloned()
                .unwrap_or_else(|| Value::Null),
            old_row_data: payload
                .get("old_row_data")
                .cloned()
                .unwrap_or_else(|| Value::Null),
            timestamp: chrono::Utc::now().to_rfc3339(),
        }),
        Err(e) => {
            error!("Failed to parse notification payload: {:?}", e);
            None
        }
    }
}

#[derive(Debug, Deserialize, Serialize)]
pub struct PgNotify {
    pub operation: String,
    pub table: String,
    pub id: String,
    pub column: String,
    pub new_row_data: Value,
    pub old_row_data: Value,
    pub timestamp: String,
}

#[cfg(test)]
mod tests {
    use std::{env, sync::Arc};
    use tokio::time::{sleep, Duration};

    use dotenv::dotenv;
    use sqlx::Executor;

    use crate::{
        database::{
            postgres::{get_or_create_pool, PostgresTableListener},
            DBListenerTrait,
        },
        EventType,
    };

    #[tokio::test]
    async fn create_new_listener_with_props() {
        dotenv().ok();
        let database_url =
            env::var("POSTGRES_DATABASE_URL").expect("POSTGRES_DATABASE_URL must be set");

        let table_name = "swaps".to_string();
        let columns = vec![
            "initiate_tx_hash".to_string(),
            "redeem_tx_hash".to_string(),
            "refund_tx_hash".to_string(),
        ];

        let table_identifier = "swap_id".to_string();

        let events = vec![EventType::UPDATE, EventType::INSERT, EventType::DELETE];

        let result = PostgresTableListener::new(
            &database_url,
            &table_name,
            columns,
            &table_identifier,
            events,
        )
        .await;

        assert!(!result.is_err(), "Listener failed to connect");

        sleep(Duration::from_secs(1)).await;
    }

    #[tokio::test]
    async fn create_new_listener_with_invalid_props() {
        dotenv().ok();
        let database_url =
            env::var("POSTGRES_DATABASE_URL").expect("POSTGRES_DATABASE_URL must be set");

        let table_name = "atomic_swaps".to_string();
        let columns = vec![
            "initiate_tx_hash".to_string(),
            "redeem_tx_hash".to_string(),
            "refund_tx_hash".to_string(),
        ];

        let table_identifier = "swap_id".to_string();

        let events = vec![EventType::UPDATE, EventType::INSERT, EventType::DELETE];

        let result = PostgresTableListener::new(
            &database_url,
            &table_name,
            columns,
            &table_identifier,
            events,
        )
        .await;

        assert!(result.is_err(), "Listener failed to connect");

        sleep(Duration::from_secs(1)).await;
    }

    #[tokio::test]
    async fn get_same_pool_for_same_url() {
        dotenv().ok();
        let database_url =
            env::var("POSTGRES_DATABASE_URL").expect("POSTGRES_DATABASE_URL must be set");

        let pool1 = get_or_create_pool(&database_url).await.unwrap();

        let pool2 = get_or_create_pool(&database_url).await.unwrap();

        assert!(
            Arc::ptr_eq(&pool1, &pool2),
            "Expected the same pool instance, but got different ones"
        );

        sleep(Duration::from_secs(1)).await;
    }

    #[tokio::test]
    // #[ignore = "this should be tested alone.. as it requires client connection for the same db url"]
    async fn postgres_table_listener() {
        sleep(Duration::from_secs(1)).await;

        dotenv().ok();

        // Get the database URL from the environment variables
        let database_url =
            env::var("POSTGRES_DATABASE_URL").expect("POSTGRES_DATABASE_URL must be set");

        let table_name = "swaps".to_string();
        let columns = vec![
            "initiate_tx_hash".to_string(),
            "redeem_tx_hash".to_string(),
            "refund_tx_hash".to_string(),
        ];

        let table_identifier = "swap_id".to_string();

        let events = vec![EventType::UPDATE, EventType::INSERT, EventType::DELETE];

        let postgres_table_listener = PostgresTableListener::new(
            &database_url,
            &table_name,
            columns.clone(),
            &table_identifier,
            events.clone(),
        )
        .await;

        assert!(
            postgres_table_listener.is_ok(),
            "Failed to intialize postgres table listener"
        );

        let postgres_table_listener = postgres_table_listener.unwrap();

        let (rx, handle) = postgres_table_listener.start().await.unwrap();

        let notification_task = tokio::spawn(async move {
            let mut received_events = Vec::new();
            while let Some(payload) = rx.lock().await.recv().await {
                println!("Notification received: {:#?}", payload);
                received_events.push(payload);
                if received_events.len() >= 3 {
                    break; // Stop after receiving all expected events
                }
            }
            received_events
        });

        let pool = sqlx::PgPool::connect(&database_url)
            .await
            .expect("Failed to connect to DB");

        async fn execute_query(pool: &sqlx::PgPool, query: &str) {
            pool.execute(query).await.expect("Query execution failed");
        }

        // Execute queries
        execute_query(
        &pool,
        &format!(
            "INSERT INTO {} (id, initiate_tx_hash, redeem_tx_hash, refund_tx_hash) VALUES (1, 'tx1', 'tx2', 'tx3')",
            table_name
            ),
        )
        .await;

        sleep(Duration::from_millis(100)).await;

        execute_query(
            &pool,
            &format!(
                "UPDATE {} SET redeem_tx_hash = 'updated_tx2' WHERE id = 1",
                table_name
            ),
        )
        .await;

        sleep(Duration::from_millis(100)).await;

        execute_query(&pool, &format!("DELETE FROM {} WHERE id = 1", table_name)).await;

        sleep(Duration::from_secs(2)).await; // Allow time for notifications to be received

        let received_events = notification_task.await.unwrap();

        assert_eq!(
            received_events.len(),
            3,
            "Expected 3 events but received {}",
            received_events.len()
        );

        postgres_table_listener.stop().await.unwrap();
        handle.abort();
    }
}