//! Latency harness for the album-description path (`album_info_for_artist_id`).
//!
//! This is the description counterpart to `discography_audit`: it measures the
//! call the artist page's expander and background hint harvest both make, so
//! optimization work has a before/after number instead of an impression.
//!
//! Usage:
//!   cargo run -p metadata --example album_info_bench -- "Artist" "Title" "Title" ...
//!
//! Reports, in order:
//!   1. COLD SEQUENTIAL — one fresh client, titles one at a time. This is what
//!      the frontend harvest does today (`for (const title of titles) await`),
//!      so its total is the wall-clock the user waits for the tabs to settle.
//!   2. WARM SEQUENTIAL — same client again, exercising the per-source caches.
//!   3. COLD CONCURRENT — a second fresh client, all titles at once. The gap
//!      against (1) is the ceiling available from parallelizing the harvest.

use metadata::MetadataClient;
use std::sync::Arc;
use std::time::Instant;

#[tokio::main]
async fn main() {
    let mut args = std::env::args().skip(1);
    let Some(artist) = args.next() else {
        eprintln!("usage: album_info_bench -- \"Artist\" \"Title\" [\"Title\" ...]");
        return;
    };
    let titles: Vec<String> = args.collect();
    if titles.is_empty() {
        eprintln!("give at least one album title");
        return;
    }

    let client = Arc::new(MetadataClient::new());
    let search = client.catalog_search(&artist).await;
    let artist_id = search
        .artists
        .iter()
        .find(|a| normalize(&a.name) == normalize(&artist))
        .map(|a| a.id);
    println!(
        "artist {artist:?} -> id {artist_id:?}, {} titles\n",
        titles.len()
    );

    let cold = run_sequential(&client, artist_id, &artist, &titles, "COLD SEQUENTIAL").await;
    let warm = run_sequential(&client, artist_id, &artist, &titles, "WARM SEQUENTIAL").await;

    // A second client so the concurrent run is genuinely cold; sharing the
    // first one would measure the cache, not the network path.
    let fresh = Arc::new(MetadataClient::new());
    let started = Instant::now();
    let mut tasks = Vec::new();
    for title in &titles {
        let fresh = Arc::clone(&fresh);
        let artist = artist.clone();
        let title = title.clone();
        tasks.push(tokio::spawn(async move {
            let at = Instant::now();
            let info = fresh
                .album_info_for_artist_id(artist_id, &artist, &title)
                .await;
            (title, at.elapsed().as_millis(), info.type_hint)
        }));
    }
    let mut rows = Vec::new();
    for task in tasks {
        if let Ok(row) = task.await {
            rows.push(row);
        }
    }
    let concurrent = started.elapsed().as_millis();
    println!("== COLD CONCURRENT ==");
    for (title, ms, hint) in &rows {
        println!("  {ms:>6} ms  {title}  hint={hint:?}");
    }
    println!("  total {concurrent} ms\n");

    println!("== SUMMARY ==");
    println!("  cold sequential : {cold:>6} ms   <- today's harvest wall-clock");
    println!("  warm sequential : {warm:>6} ms   <- per-source cache hit");
    println!("  cold concurrent : {concurrent:>6} ms   <- ceiling from fan-out");
    if concurrent > 0 {
        println!(
            "  speedup         : {:.1}x",
            cold as f64 / concurrent as f64
        );
    }
}

async fn run_sequential(
    client: &Arc<MetadataClient>,
    artist_id: Option<u64>,
    artist: &str,
    titles: &[String],
    label: &str,
) -> u128 {
    println!("== {label} ==");
    let started = Instant::now();
    for title in titles {
        let at = Instant::now();
        let info = client
            .album_info_for_artist_id(artist_id, artist, title)
            .await;
        println!(
            "  {:>6} ms  {title}  hint={:?} source={:?}",
            at.elapsed().as_millis(),
            info.type_hint,
            info.source,
        );
    }
    let total = started.elapsed().as_millis();
    println!("  total {total} ms\n");
    total
}

fn normalize(s: &str) -> String {
    s.to_lowercase()
        .chars()
        .filter(|c| c.is_alphanumeric())
        .collect()
}