use crate::Error;
use chrono::Utc;
use directories::ProjectDirs;
use futures::{StreamExt, TryStreamExt};
use serde::de::DeserializeOwned;
use serde::Serialize;
use sqlx::sqlite::{SqliteConnectOptions, SqliteJournalMode};
use sqlx::{QueryBuilder, Sqlite, SqlitePool};
use std::fmt::Display;
use tabled::Tabled;
use tokio::fs;
use tracing::{info, instrument};

static SQLITE_BIND_LIMIT: usize = 32766;

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

impl Display for TaskStatus {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            TaskStatus::Pending => {
                write!(f, "Pending")
            }
            TaskStatus::InProgress => {
                write!(f, "In Progress")
            }
            TaskStatus::Completed => {
                write!(f, "Completed")
            }
            TaskStatus::Failed => {
                write!(f, "Failed")
            }
        }
    }
}

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

pub type TaskJob<T: _Task> = fn(&Task<T>) -> TaskStatus;

#[derive(sqlx::FromRow, Tabled, Debug)]
pub struct Task<T: DeserializeOwned + std::fmt::Display> {
    id: u32,
    payload_key: String,
    #[sqlx(json)]
    #[tabled(skip)]
    payload: T,
    #[sqlx(rename = "status_id")]
    status: TaskStatus,
    created_at: chrono::DateTime<Utc>,
    #[tabled(display = "display_option_date")]
    updated_at: Option<chrono::DateTime<Utc>>,
}

impl<T: DeserializeOwned + std::fmt::Display> Task<T> {
    pub fn get_key(&self) -> String {
        self.payload_key.clone()
    }
}

fn display_option_date(o: &Option<chrono::DateTime<Utc>>) -> String {
    match o {
        Some(s) => format!("{}", s),
        None => String::from(""),
    }
}

pub trait _Task: DeserializeOwned + Send + Unpin + 'static + Display {}
impl<T: DeserializeOwned + Send + Unpin + 'static + Display> _Task for T {}

#[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)
    }

    fn get_task_builder(
        status: Option<TaskStatus>,
        limit: Option<u16>,
    ) -> QueryBuilder<'static, Sqlite> {
        let mut builder: QueryBuilder<'_, Sqlite> = QueryBuilder::new(
            "select id, payload_key, payload, status_id, created_at, updated_at from tasks ",
        );

        if let Some(status) = status {
            builder.push("where status_id = ").push_bind(status);
        }

        builder.push("ORDER BY created_at DESC ");

        if let Some(limit) = limit {
            builder.push("LIMIT ").push_bind(limit);
        }
        builder
    }

    pub async fn get_tasks<T: _Task>(
        &self,
        status: Option<TaskStatus>,
        limit: Option<u16>,
    ) -> crate::Result<Vec<Task<T>>> {
        let mut builder = Self::get_task_builder(status, limit);

        let tasks: Vec<Task<T>> = builder.build_query_as().fetch_all(&self.pool).await?;

        Ok(tasks)
    }

    #[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(())
    }

    pub async fn run_tasks<T: _Task>(&self, func: TaskJob<T>) -> crate::Result<()> {
        let mut builder = Self::get_task_builder(Some(TaskStatus::Pending), None);

        let rows = builder.build_query_as::<Task<T>>().fetch(&self.pool);

        let result: Vec<(Task<T>, TaskStatus)> = rows.map(|x| {
            let task = x.unwrap();
            let status = func(&task);

            (task, status)
        }).collect().await;

        Ok(())
    }
}