//! Server-Sent Events endpoint for real-time status push.
//!
//! The supervisor sends `()` on a `broadcast::Sender` after every
//! `update_status()` cycle. Each SSE client subscribes, renders the
//! partial templates, and pushes them as a single `status` event with
//! htmx OOB swap attributes so multiple DOM regions update at once.

use std::convert::Infallible;
use std::time::Duration;

use askama::Template;
use axum::extract::State;
use axum::response::sse::{Event, KeepAlive, Sse};
use axum::routing::get;
use axum::Router;
use tokio_stream::wrappers::BroadcastStream;
use tokio_stream::StreamExt;

use crate::web::SharedState;

pub fn routes() -> Router<SharedState> {
    Router::new().route("/events", get(sse_handler))
}

async fn sse_handler(
    State(state): State<SharedState>,
) -> Sse<impl tokio_stream::Stream<Item = Result<Event, Infallible>>> {
    let rx = state.sse_tx.subscribe();
    let stream = BroadcastStream::new(rx).filter_map(move |r| {
        match r {
            Ok(()) => {
                let status = state.status.read().unwrap();
                let config = state.config.read().unwrap();

                let html = render_sse_payload(&status, &config);
                Some(Ok(Event::default().event("status").data(html)))
            }
            Err(_) => None, // lagged, skip
        }
    });

    Sse::new(stream).keep_alive(KeepAlive::new().interval(Duration::from_secs(15)))
}

/// Render all SSE partials into a single HTML payload.
///
/// Uses htmx OOB (Out-of-Band) swap so a single SSE event can update
/// multiple independent DOM regions:
/// - `#dashboard-stats` — stat cards
/// - `#share-rows` — share card list
/// - `#protocol-badges` — SMB/NFS/WebDAV badges
fn render_sse_payload(
    status: &crate::daemon::DaemonStatus,
    config: &crate::config::Config,
) -> String {
    let shares: Vec<SseShareView> = status
        .shares
        .iter()
        .map(|s| {
            let share_config = config.find_share(&s.name);
            let (warmup_state, warmup_done, warmup_total) =
                status.warmup_summary_for(&s.name);
            SseShareView {
                name: s.name.clone(),
                connection: share_config
                    .map(|sc| sc.connection.clone())
                    .unwrap_or_default(),
                mount_point: share_config
                    .map(|sc| sc.mount_point.display().to_string())
                    .unwrap_or_default(),
                remote_path: share_config
                    .map(|sc| sc.remote_path.clone())
                    .unwrap_or_default(),
                mounted: s.mounted,
                cache_display: s.cache_display(),
                dirty_count: s.dirty_count,
                errored_files: s.errored_files,
                speed_display: s.speed_display(),
                transfers: s.transfers,
                errors: s.errors,
                read_only: share_config.map(|sc| sc.read_only).unwrap_or(false),
                health: s.health_label().to_string(),
                health_message: s.health_message().unwrap_or("").to_string(),
                rc_port: s.rc_port,
                warmup_state: warmup_state.to_string(),
                warmup_done,
                warmup_total,
            }
        })
        .collect();

    let healthy_count = shares.iter().filter(|s| s.health == "OK").count();
    let failed_count = shares.iter().filter(|s| s.health == "FAILED").count();
    let total_cache: u64 = status.shares.iter().map(|s| s.cache_bytes).sum();
    let total_speed: f64 = status.shares.iter().map(|s| s.speed).sum();
    let active_transfers: u64 = status.shares.iter().map(|s| s.transfers).sum();

    let stats = DashboardStatsPartial {
        total_shares: shares.len(),
        healthy_count,
        failed_count,
        total_cache_display: format_bytes_static(total_cache),
        aggregate_speed_display: if total_speed < 1.0 {
            "-".to_string()
        } else {
            format!("{}/s", format_bytes_static(total_speed as u64))
        },
        active_transfers,
        uptime: status.uptime_string(),
    };

    let share_rows = ShareRowsPartial {
        shares: shares.clone(),
    };

    let badges = ProtocolBadgesPartial {
        smbd_running: status.smbd_running,
        nfs_exported: status.nfs_exported,
        webdav_running: status.webdav_running,
    };

    let sync_status = SyncStatusPartial {
        all_synced: status.all_synced,
    };

    let mut html = String::new();
    // Primary target: dashboard stats
    if let Ok(s) = stats.render() {
        html.push_str(&s);
    }
    // OOB: share rows
    if let Ok(s) = share_rows.render() {
        html.push_str(&s);
    }
    // OOB: protocol badges
    if let Ok(s) = badges.render() {
        html.push_str(&s);
    }
    // OOB: sync status indicator
    if let Ok(s) = sync_status.render() {
        html.push_str(&s);
    }
    html
}

fn format_bytes_static(bytes: u64) -> String {
    const KIB: f64 = 1024.0;
    const MIB: f64 = KIB * 1024.0;
    const GIB: f64 = MIB * 1024.0;
    const TIB: f64 = GIB * 1024.0;
    let b = bytes as f64;
    if b >= TIB {
        format!("{:.1} TiB", b / TIB)
    } else if b >= GIB {
        format!("{:.1} GiB", b / GIB)
    } else if b >= MIB {
        format!("{:.1} MiB", b / MIB)
    } else if b >= KIB {
        format!("{:.1} KiB", b / KIB)
    } else {
        format!("{bytes} B")
    }
}

// --- SSE partial templates ---

#[derive(Clone)]
#[allow(dead_code)] // fields used by askama templates
pub struct SseShareView {
    pub name: String,
    pub connection: String,
    pub mount_point: String,
    pub remote_path: String,
    pub mounted: bool,
    pub cache_display: String,
    pub dirty_count: u64,
    pub errored_files: u64,
    pub speed_display: String,
    pub transfers: u64,
    pub errors: u64,
    pub read_only: bool,
    pub health: String,
    pub health_message: String,
    pub rc_port: u16,
    pub warmup_state: String,
    pub warmup_done: usize,
    pub warmup_total: usize,
}

#[derive(Template)]
#[template(path = "web/partials/dashboard_stats.html")]
struct DashboardStatsPartial {
    total_shares: usize,
    healthy_count: usize,
    #[allow(dead_code)]
    failed_count: usize,
    total_cache_display: String,
    aggregate_speed_display: String,
    active_transfers: u64,
    uptime: String,
}

#[derive(Template)]
#[template(path = "web/partials/share_rows.html")]
struct ShareRowsPartial {
    shares: Vec<SseShareView>,
}

#[derive(Template)]
#[template(path = "web/partials/protocol_badges.html")]
struct ProtocolBadgesPartial {
    smbd_running: bool,
    nfs_exported: bool,
    webdav_running: bool,
}

#[derive(Template)]
#[template(path = "web/partials/sync_status.html")]
struct SyncStatusPartial {
    all_synced: bool,
}