//! Artist monitoring — periodically checks for new releases from monitored artists
//! and automatically adds them to the watchlist.

use std::collections::HashSet;
use std::time::Duration;

use actix_web::web;
use serde::Serialize;
use shanty_data::MetadataFetcher;
use shanty_db::queries;
use shanty_search::SearchProvider;

use crate::error::ApiError;
use crate::state::AppState;

/// Stats returned from a monitor check run.
#[derive(Debug, Clone, Serialize)]
pub struct MonitorStats {
    pub artists_checked: u32,
    pub new_releases_found: u32,
    pub tracks_added: u32,
}

/// Check all monitored artists for new releases and add them to the watchlist.
pub async fn check_monitored_artists(
    state: &web::Data<AppState>,
) -> Result<MonitorStats, ApiError> {
    let monitored = queries::artists::list_monitored(state.db.conn()).await?;

    let mut stats = MonitorStats {
        artists_checked: 0,
        new_releases_found: 0,
        tracks_added: 0,
    };

    let allowed = state.config.read().await.allowed_secondary_types.clone();

    for artist in &monitored {
        let mbid = match &artist.musicbrainz_id {
            Some(m) => m.clone(),
            None => {
                tracing::warn!(
                    artist_id = artist.id,
                    name = %artist.name,
                    "monitored artist has no MBID, skipping"
                );
                continue;
            }
        };

        stats.artists_checked += 1;

        // Fetch release groups from MusicBrainz
        let all_release_groups = match state.search.get_release_groups(&mbid).await {
            Ok(rgs) => rgs,
            Err(e) => {
                tracing::warn!(
                    artist = %artist.name,
                    error = %e,
                    "failed to fetch release groups for monitored artist"
                );
                continue;
            }
        };

        // Filter by allowed secondary types (same logic as enrich_artist)
        let release_groups: Vec<_> = all_release_groups
            .into_iter()
            .filter(|rg| {
                if rg.secondary_types.is_empty() {
                    true
                } else {
                    rg.secondary_types.iter().all(|st| allowed.contains(st))
                }
            })
            .collect();

        // Get all existing wanted items for this artist
        let artist_wanted = queries::wanted::list(state.db.conn(), None, None).await?;
        let wanted_mbids: HashSet<String> = artist_wanted
            .iter()
            .filter(|w| w.artist_id == Some(artist.id))
            .filter_map(|w| w.musicbrainz_id.clone())
            .collect();

        // Check each release group's tracks to find new ones
        for rg in &release_groups {
            // Check if we already have any tracks from this release group cached
            let cache_key = format!("artist_rg_tracks:{}", rg.id);
            let cached_tracks: Option<Vec<String>> =
                if let Ok(Some(json)) = queries::cache::get(state.db.conn(), &cache_key).await {
                    // Parse the cached data to get recording MBIDs
                    if let Ok(cached) = serde_json::from_str::<serde_json::Value>(&json) {
                        cached
                            .get("tracks")
                            .and_then(|t| t.as_array())
                            .map(|tracks| {
                                tracks
                                    .iter()
                                    .filter_map(|t| {
                                        t.get("recording_mbid")
                                            .and_then(|m| m.as_str())
                                            .map(String::from)
                                    })
                                    .collect()
                            })
                    } else {
                        None
                    }
                } else {
                    None
                };

            let track_mbids = if let Some(mbids) = cached_tracks {
                mbids
            } else {
                // Not cached — resolve release and fetch tracks (rate limited by shared MB client)
                let release_mbid = if let Some(ref rid) = rg.first_release_id {
                    rid.clone()
                } else {
                    // Resolve from release group (goes through shared rate limiter)
                    match state.mb_client.resolve_release_from_group(&rg.id).await {
                        Ok(rid) => rid,
                        Err(e) => {
                            tracing::debug!(rg_id = %rg.id, error = %e, "skipping release group");
                            continue;
                        }
                    }
                };

                match state.mb_client.get_release_tracks(&release_mbid).await {
                    Ok(tracks) => tracks.into_iter().map(|t| t.recording_mbid).collect(),
                    Err(e) => {
                        tracing::debug!(
                            release = %release_mbid,
                            error = %e,
                            "failed to fetch tracks"
                        );
                        continue;
                    }
                }
            };

            // Check if any of these tracks are NOT in the wanted items
            let new_mbids: Vec<&String> = track_mbids
                .iter()
                .filter(|mbid| !wanted_mbids.contains(*mbid))
                .collect();

            if new_mbids.is_empty() {
                continue;
            }

            // Found a release group with new tracks — add the whole album via shanty_watch
            tracing::info!(
                artist = %artist.name,
                album = %rg.title,
                new_tracks = new_mbids.len(),
                "new release detected for monitored artist"
            );

            stats.new_releases_found += 1;

            match shanty_watch::add_album(
                state.db.conn(),
                Some(&artist.name),
                Some(&rg.title),
                rg.first_release_id.as_deref(),
                &state.mb_client,
                None, // system-initiated, no user_id
            )
            .await
            {
                Ok(summary) => {
                    stats.tracks_added += summary.tracks_added as u32;
                }
                Err(e) => {
                    tracing::warn!(
                        artist = %artist.name,
                        album = %rg.title,
                        error = %e,
                        "failed to add album for monitored artist"
                    );
                }
            }
        }

        // Update last_checked_at
        if let Err(e) = queries::artists::update_last_checked(state.db.conn(), artist.id).await {
            tracing::warn!(
                artist_id = artist.id,
                error = %e,
                "failed to update last_checked_at"
            );
        }
    }

    Ok(stats)
}

/// Spawn the monitor scheduler background loop.
///
/// Sleeps for the configured interval, then checks monitored artists if enabled.
/// Reads config each iteration so changes take effect without restart.
pub fn spawn(state: web::Data<AppState>) {
    tokio::spawn(async move {
        loop {
            let (enabled, hours) = {
                let cfg = state.config.read().await;
                (
                    cfg.scheduling.monitor_enabled,
                    cfg.scheduling.monitor_interval_hours.max(1),
                )
            };

            let sleep_secs = u64::from(hours) * 3600;

            // Update next-run time
            {
                let mut sched = state.scheduler.lock().await;
                sched.next_monitor = if enabled {
                    Some(
                        (chrono::Utc::now() + chrono::Duration::seconds(sleep_secs as i64))
                            .naive_utc(),
                    )
                } else {
                    None
                };
            }

            tokio::time::sleep(Duration::from_secs(sleep_secs)).await;

            if !enabled {
                continue;
            }

            // Check if this run was skipped
            {
                let mut sched = state.scheduler.lock().await;
                sched.next_monitor = None;
                if sched.skip_monitor {
                    sched.skip_monitor = false;
                    tracing::info!("scheduled monitor check skipped (user cancelled)");
                    continue;
                }
            }

            tracing::info!("scheduled monitor check starting");
            match check_monitored_artists(&state).await {
                Ok(stats) => {
                    tracing::info!(
                        artists_checked = stats.artists_checked,
                        new_releases = stats.new_releases_found,
                        tracks_added = stats.tracks_added,
                        "scheduled monitor check complete"
                    );
                }
                Err(e) => {
                    tracing::error!(error = %e, "scheduled monitor check failed");
                }
            }
        }
    });
}