//! Common test utilities for tokenizer tests

use std::{
    fs,
    path::PathBuf,
    sync::{Mutex, OnceLock},
};

// Tokenizer download configuration
const TINYLLAMA_TOKENIZER_URL: &str =
    "https://huggingface.co/TinyLlama/TinyLlama-1.1B-Chat-v1.0/resolve/main/tokenizer.json";
const CACHE_DIR: &str = ".tokenizer_cache";
const TINYLLAMA_TOKENIZER_FILENAME: &str = "tinyllama_tokenizer.json";

// Global mutex to prevent concurrent downloads
static DOWNLOAD_MUTEX: OnceLock<Mutex<()>> = OnceLock::new();

/// Downloads the TinyLlama tokenizer from HuggingFace if not already cached.
/// Returns the path to the cached tokenizer file.
///
/// This function is thread-safe and will only download the tokenizer once
/// even if called from multiple threads concurrently.
#[expect(clippy::unwrap_used, reason = "test helper — panics are intentional")]
#[expect(clippy::expect_used, reason = "test helper — panics are intentional")]
#[expect(clippy::print_stdout, reason = "test diagnostic output")]
pub fn ensure_tokenizer_cached() -> PathBuf {
    // Get or initialize the mutex
    let mutex = DOWNLOAD_MUTEX.get_or_init(|| Mutex::new(()));

    // Lock to ensure only one thread downloads at a time
    let _guard = mutex.lock().unwrap();

    let cache_dir = PathBuf::from(CACHE_DIR);
    let tokenizer_path = cache_dir.join(TINYLLAMA_TOKENIZER_FILENAME);

    // Create cache directory if it doesn't exist
    if !cache_dir.exists() {
        fs::create_dir_all(&cache_dir).expect("Failed to create cache directory");
    }

    // Download tokenizer if not already cached
    if !tokenizer_path.exists() {
        println!("Downloading TinyLlama tokenizer from HuggingFace...");

        // Use blocking reqwest client since we're in tests/benchmarks
        let client = reqwest::blocking::Client::new();
        let response = client
            .get(TINYLLAMA_TOKENIZER_URL)
            .send()
            .expect("Failed to download tokenizer");

        assert!(
            response.status().is_success(),
            "Failed to download tokenizer: HTTP {}",
            response.status()
        );

        let content = response.bytes().expect("Failed to read tokenizer content");

        assert!(
            content.len() >= 100,
            "Downloaded content too small: {} bytes",
            content.len()
        );

        fs::write(&tokenizer_path, content).expect("Failed to write tokenizer to cache");
        println!(
            "Tokenizer downloaded and cached successfully ({} bytes)",
            tokenizer_path.metadata().unwrap().len()
        );
    }

    tokenizer_path
}

/// Common test prompts for consistency across tests
pub const TEST_PROMPTS: [&str; 4] = [
    "deep learning is",
    "Deep learning is",
    "has anyone seen nemo lately",
    "another prompt",
];

/// Pre-computed hashes for verification
pub const EXPECTED_HASHES: [u64; 4] = [
    1209591529327510910,
    4181375434596349981,
    6245658446118930933,
    5097285695902185237,
];
