//! Daily cost summary as a push notification (20:00 local time, opt-in per
//! user via the user setting "cost_push").

use crate::app::App;
use chrono::{Local, Timelike};
use serde_json::{Value, json};
use std::sync::Arc;
use std::time::Duration;

const HOUR: u32 = 20;

fn money(v: f64, currency: &str, de: bool) -> String {
    let s = format!("{v:.2}");
    let s = if de { s.replace('.', ",") } else { s };
    match currency {
        "" | "USD" => if de { format!("{s} $") } else { format!("${s}") },
        "EUR" => format!("{s} €"),
        c => format!("{s} {c}"),
    }
}

/// Today's summary for one user (None when nothing was used).
pub fn summary(app: &App, user_id: &str) -> Option<Value> {
    let now = Local::now();
    let start = now.with_hour(0)?.with_minute(0)?.with_second(0)?.timestamp_millis();
    let offset = now.offset().local_minus_utc() as i64 / 60;
    let stats = app.store.global_stats(start, now.timestamp_millis() + 1, offset, Some(user_id)).ok()?;
    let requests = stats["total"]["requests"].as_i64().unwrap_or(0);
    if requests == 0 {
        return None;
    }
    let prefs: Value = app.store.user_setting(user_id, "prefs").unwrap_or_default();
    let de = prefs["lang"].as_str().unwrap_or("").starts_with("de");
    let currency = app.config().server.currency.clone();
    let cost = stats["total"]["cost"].as_f64().unwrap_or(0.0);
    let top = stats["by_model"]
        .as_array()
        .and_then(|m| m.iter().max_by(|a, b| a["cost"].as_f64().unwrap_or(0.0).total_cmp(&b["cost"].as_f64().unwrap_or(0.0))))
        .and_then(|m| m["model"].as_str())
        .unwrap_or("")
        .to_string();
    let sessions = stats["top_sessions"].as_array().map(|a| a.len()).unwrap_or(0);
    let body = if de {
        format!("{} · {requests} Anfragen in {sessions} Chats{}", money(cost, &currency, true), if top.is_empty() { String::new() } else { format!(" · meist {top}") })
    } else {
        format!("{} · {requests} requests in {sessions} chats{}", money(cost, &currency, false), if top.is_empty() { String::new() } else { format!(" · mostly {top}") })
    };
    Some(json!({
        "kind": "digest",
        "title": if de { "CodeCraft – Kosten heute" } else { "CodeCraft – today's costs" },
        "body": body,
        "tag": "cost-digest",
        "url": "/#/stats",
    }))
}

pub fn spawn(app: Arc<App>) {
    tokio::spawn(async move {
        loop {
            tokio::time::sleep(Duration::from_secs(60)).await;
            let now = Local::now();
            if now.hour() != HOUR {
                continue;
            }
            let today = now.format("%Y-%m-%d").to_string();
            for user in app.store.users().unwrap_or_default() {
                let on: bool = app.store.user_setting(&user.id, "cost_push").unwrap_or(false);
                let last: String = app.store.user_setting(&user.id, "cost_push_last").unwrap_or_default();
                if !on || user.disabled || last == today {
                    continue;
                }
                let _ = app.store.set_user_setting(&user.id, "cost_push_last", &today);
                if let Some(payload) = summary(&app, &user.id) {
                    let (sent, errors) = crate::push::send_to_user(&app, &user.id, &payload).await;
                    tracing::info!(user = %user.username, sent, errors = errors.len(), "daily cost summary");
                }
            }
        }
    });
}