use crate::Error;
use directories::ProjectDirs;
use serde::Serialize;
use sqlx::sqlite::{SqliteConnectOptions, SqliteJournalMode};
use sqlx::{QueryBuilder, Sqlite, SqlitePool};
use tokio::fs;
use tracing::{info, instrument};

static SQLITE_BIND_LIMIT: usize = 32766;

#[derive(sqlx::Type)]
#[repr(u8)]
pub enum TaskStatus {
    Pending = 1,
    InProgress = 2,
    Completed = 3,
    Failed = 4,
}

pub trait TaskPayload {
    fn get_key(&self) -> String;
}

#[derive(Debug)]
pub struct TaskManager {
    pool: SqlitePool,
}

impl TaskManager {
    pub async fn new() -> Result<TaskManager, Error> {
        Ok(Self {
            pool: Self::connect_database().await?,
        })
    }

    async fn connect_database() -> crate::Result<SqlitePool> {
        let project_dir = ProjectDirs::from("", "", env!("CARGO_PKG_NAME"))
            .ok_or(Error::Unhandled("Could not get standard directories"))?;

        let database_file_path = project_dir.data_dir().join("db.sql");

        fs::create_dir_all(project_dir.data_dir()).await?;

        let opts = SqliteConnectOptions::new()
            .filename(database_file_path)
            .create_if_missing(true)
            .journal_mode(SqliteJournalMode::Wal);

        let pool = SqlitePool::connect_with(opts).await?;

        sqlx::migrate!("./migrations").run(&pool).await?;

        Ok(pool)
    }

    #[instrument(skip(self, values))]
    pub async fn load_tasks<T>(&self, values: Vec<T>) -> crate::Result<()>
    where
        T: TaskPayload + Serialize + std::fmt::Debug,
    {
        let mut tx = self.pool.begin().await?;
        let mut builder: QueryBuilder<'_, Sqlite> =
            QueryBuilder::new("insert into tasks(payload_key, payload, status_id)");

        let args: crate::Result<Vec<(String, String)>> = values
            .iter()
            .map(|value| Ok((value.get_key(), serde_json::to_string(value)?)))
            .collect();


        let mut affected_rows = 0;
        // Chunk the query by the size limit of bind params
        for chunk in args?.chunks(SQLITE_BIND_LIMIT / 3) {
            builder.push_values(chunk, |mut builder, item| {
                builder
                    .push_bind(&item.0)
                    .push_bind(&item.1)
                    .push_bind(TaskStatus::Pending);
            });
            builder.push("ON conflict (payload_key) DO NOTHING");

            let query = builder.build();

            affected_rows += query.execute(&mut *tx).await?.rows_affected();
            builder.reset();
        }

        tx.commit().await?;

        info!("{} rows inserted.", affected_rows);

        Ok(())
    }
}