use crate::HandlerConfig;
use anyhow::{anyhow, Context as _, Result};
use serenity::all::{Context, MessageBuilder};
use std::{sync::Arc, time::Duration};
use time::{Date, OffsetDateTime, Weekday};
use tokio::{
    fs::{self, create_dir_all, File},
    time::{interval, MissedTickBehavior},
};

static REACTS: &[char] = &['✅', '❌', '❔'];

pub async fn start(config: Arc<HandlerConfig>, ctx: Context) {
    let mut timer = interval(Duration::from_secs(1));
    timer.set_missed_tick_behavior(MissedTickBehavior::Skip);
    loop {
        timer.tick().await;
        if let Err(err) = tick(&*config, &ctx).await {
            log::error!("{err:?}");
        }
    }
}

async fn tick(config: &HandlerConfig, ctx: &Context) -> Result<()> {
    let now = OffsetDateTime::now_local().context("Failed to get current time")?;
    if now.weekday() != Weekday::Sunday {
        // Wait to post 'till Sunday.
        return Ok(());
    }
    let mut now_path = config.db_dir.join("labwatch");
    create_dir_all(&now_path)
        .await
        .with_context(|| anyhow!("Failed to create {now_path:?}"))?;
    now_path.push(date_name(now.date()));
    if fs::try_exists(&now_path)
        .await
        .with_context(|| anyhow!("Failed to check if {now_path:?} exists"))?
    {
        // Already posted this week.
        return Ok(());
    }

    let mut date = now.date();
    for _ in 1..=5 {
        date = date.next_day().context("Reached the end of times")?;
        let msg = MessageBuilder::new().push(date_name(date)).build();
        let msg = config
            .labwatch_channel_id
            .say(&ctx.http, &msg)
            .await
            .with_context(|| anyhow!("Failed to send message for {date}"))?;
        for &react in REACTS {
            msg.react(&ctx.http, react).await.with_context(|| {
                anyhow!("Failed to react with {react} on the message for {date}")
            })?;
        }
    }

    File::create(&now_path)
        .await
        .with_context(|| anyhow!("Failed to create {now_path:?}"))?;
    Ok(())
}

fn date_name(date: Date) -> String {
    format!("{}, {} {}", date.weekday(), date.month(), date.day())
}