use zellij_utils::async_std::task;
use zellij_utils::errors::{prelude::*, BackgroundJobContext, ContextType};

use std::collections::HashMap;
use std::time::{Duration, Instant};

use crate::panes::PaneId;
use crate::screen::ScreenInstruction;
use crate::thread_bus::Bus;

#[derive(Debug, Clone, Eq, PartialEq, Hash)]
pub enum BackgroundJob {
    DisplayPaneError(Vec<PaneId>, String),
    Exit,
}

impl From<&BackgroundJob> for BackgroundJobContext {
    fn from(background_job: &BackgroundJob) -> Self {
        match *background_job {
            BackgroundJob::DisplayPaneError(..) => BackgroundJobContext::DisplayPaneError,
            BackgroundJob::Exit => BackgroundJobContext::Exit,
        }
    }
}

static FLASH_DURATION_MS: u64 = 1000;

pub(crate) fn background_jobs_main(bus: Bus<BackgroundJob>) -> Result<()> {
    let err_context = || "failed to write to pty".to_string();
    let mut running_jobs: HashMap<BackgroundJob, Instant> = HashMap::new();

    loop {
        let (event, mut err_ctx) = bus.recv().with_context(err_context)?;
        err_ctx.add_call(ContextType::BackgroundJob((&event).into()));
        let job = event.clone();
        match event {
            BackgroundJob::DisplayPaneError(pane_ids, text) => {
                if job_already_running(job, &mut running_jobs) {
                    continue;
                }
                task::spawn({
                    let senders = bus.senders.clone();
                    async move {
                        let _ = senders.send_to_screen(
                            ScreenInstruction::AddRedPaneFrameColorOverride(
                                pane_ids.clone(),
                                Some(text),
                            ),
                        );
                        task::sleep(std::time::Duration::from_millis(FLASH_DURATION_MS)).await;
                        let _ = senders.send_to_screen(
                            ScreenInstruction::ClearPaneFrameColorOverride(pane_ids),
                        );
                    }
                });
            },
            BackgroundJob::Exit => {
                return Ok(());
            },
        }
    }
}

fn job_already_running(
    job: BackgroundJob,
    running_jobs: &mut HashMap<BackgroundJob, Instant>,
) -> bool {
    match running_jobs.get_mut(&job) {
        Some(current_running_job_start_time) => {
            if current_running_job_start_time.elapsed() > Duration::from_millis(FLASH_DURATION_MS) {
                *current_running_job_start_time = Instant::now();
                false
            } else {
                true
            }
        },
        None => {
            running_jobs.insert(job.clone(), Instant::now());
            false
        },
    }
}