use std::{
    collections::BTreeMap,
    env, fs,
    path::{Path, PathBuf},
    sync::LazyLock,
    time::Instant,
};

use anyhow::Context;
use log::info;
use tree_sitter::{Language, Parser, Query};
use tree_sitter_loader::{CompileConfig, Loader};

include!("../src/tests/helpers/dirs.rs");

static LANGUAGE_FILTER: LazyLock<Option<String>> =
    LazyLock::new(|| env::var("TREE_SITTER_BENCHMARK_LANGUAGE_FILTER").ok());
static EXAMPLE_FILTER: LazyLock<Option<String>> =
    LazyLock::new(|| env::var("TREE_SITTER_BENCHMARK_EXAMPLE_FILTER").ok());
static REPETITION_COUNT: LazyLock<usize> = LazyLock::new(|| {
    env::var("TREE_SITTER_BENCHMARK_REPETITION_COUNT").map_or(5, |s| s.parse::<usize>().unwrap())
});
static TEST_LOADER: LazyLock<Loader> =
    LazyLock::new(|| Loader::with_parser_lib_path(SCRATCH_DIR.clone()));

#[expect(
    clippy::type_complexity,
    reason = "complex map type reflects benchmark data structure"
)]
static EXAMPLE_AND_QUERY_PATHS_BY_LANGUAGE_DIR: LazyLock<
    BTreeMap<PathBuf, (Vec<PathBuf>, Vec<PathBuf>)>,
> = LazyLock::new(|| {
    fn process_dir(result: &mut BTreeMap<PathBuf, (Vec<PathBuf>, Vec<PathBuf>)>, dir: &Path) {
        if dir.join("grammar.js").exists() {
            let relative_path = dir.strip_prefix(GRAMMARS_DIR.as_path()).unwrap();
            let (example_paths, query_paths) = result.entry(relative_path.to_owned()).or_default();

            if let Ok(example_files) = fs::read_dir(dir.join("examples")) {
                example_paths.extend(example_files.filter_map(|p| {
                    let p = p.unwrap().path();
                    if p.is_file() { Some(p) } else { None }
                }));
            }

            if let Ok(query_files) = fs::read_dir(dir.join("queries")) {
                query_paths.extend(query_files.filter_map(|p| {
                    let p = p.unwrap().path();
                    if p.is_file() { Some(p) } else { None }
                }));
            }
        } else {
            for entry in fs::read_dir(dir).unwrap() {
                let entry = entry.unwrap().path();
                if entry.is_dir() {
                    process_dir(result, &entry);
                }
            }
        }
    }

    let mut result = BTreeMap::new();
    process_dir(&mut result, &GRAMMARS_DIR);
    result
});

fn main() {
    tree_sitter_cli::logger::init();

    let max_path_length = EXAMPLE_AND_QUERY_PATHS_BY_LANGUAGE_DIR
        .values()
        .flat_map(|(e, q)| {
            e.iter()
                .chain(q.iter())
                .map(|s| s.file_name().unwrap().to_str().unwrap().len())
        })
        .max()
        .unwrap_or(0);

    info!("Benchmarking with {} repetitions", *REPETITION_COUNT);

    let mut parser = Parser::new();
    let mut all_normal_speeds = Vec::new();
    let mut all_error_speeds = Vec::new();

    for (language_path, (example_paths, query_paths)) in
        EXAMPLE_AND_QUERY_PATHS_BY_LANGUAGE_DIR.iter()
    {
        let language_name = language_path.file_name().unwrap().to_str().unwrap();

        if let Some(filter) = LANGUAGE_FILTER.as_ref()
            && language_name != filter.as_str()
        {
            continue;
        }

        info!("\nLanguage: {language_name}");
        let language = get_language(language_path);
        parser.set_language(&language).unwrap();

        info!("  Constructing Queries");
        for path in query_paths {
            if let Some(filter) = EXAMPLE_FILTER.as_ref()
                && !path.to_str().unwrap().contains(filter.as_str())
            {
                continue;
            }

            parse(path, max_path_length, |source| {
                Query::new(&language, str::from_utf8(source).unwrap())
                    .with_context(|| format!("Query file path: {}", path.display()))
                    .expect("Failed to parse query");
            });
        }

        info!("  Parsing Valid Code:");
        let mut normal_speeds = Vec::new();
        for example_path in example_paths {
            if let Some(filter) = EXAMPLE_FILTER.as_ref()
                && !example_path.to_str().unwrap().contains(filter.as_str())
            {
                continue;
            }

            normal_speeds.push(parse(example_path, max_path_length, |code| {
                parser.parse(code, None).expect("Failed to parse");
            }));
        }

        info!("  Parsing Invalid Code (mismatched languages):");
        let mut error_speeds = Vec::new();
        for (other_language_path, (example_paths, _)) in
            EXAMPLE_AND_QUERY_PATHS_BY_LANGUAGE_DIR.iter()
        {
            if other_language_path != language_path {
                for example_path in example_paths {
                    if let Some(filter) = EXAMPLE_FILTER.as_ref()
                        && !example_path.to_str().unwrap().contains(filter.as_str())
                    {
                        continue;
                    }

                    error_speeds.push(parse(example_path, max_path_length, |code| {
                        parser.parse(code, None).expect("Failed to parse");
                    }));
                }
            }
        }

        if let Some((average_normal, worst_normal)) = aggregate(&normal_speeds) {
            info!("  Average Speed (normal): {average_normal} bytes/ms");
            info!("  Worst Speed (normal):   {worst_normal} bytes/ms");
        }

        if let Some((average_error, worst_error)) = aggregate(&error_speeds) {
            info!("  Average Speed (errors): {average_error} bytes/ms");
            info!("  Worst Speed (errors):   {worst_error} bytes/ms");
        }

        all_normal_speeds.extend(normal_speeds);
        all_error_speeds.extend(error_speeds);
    }

    info!("\n  Overall");
    if let Some((average_normal, worst_normal)) = aggregate(&all_normal_speeds) {
        info!("  Average Speed (normal): {average_normal} bytes/ms");
        info!("  Worst Speed (normal):   {worst_normal} bytes/ms");
    }

    if let Some((average_error, worst_error)) = aggregate(&all_error_speeds) {
        info!("  Average Speed (errors): {average_error} bytes/ms");
        info!("  Worst Speed (errors):   {worst_error} bytes/ms");
    }
    info!("");
}

fn aggregate(speeds: &[usize]) -> Option<(usize, usize)> {
    if speeds.is_empty() {
        return None;
    }
    let mut total = 0;
    let mut max = usize::MAX;
    for speed in speeds.iter().copied() {
        total += speed;
        if speed < max {
            max = speed;
        }
    }
    Some((total / speeds.len(), max))
}

fn parse(path: &Path, max_path_length: usize, mut action: impl FnMut(&[u8])) -> usize {
    let source_code = fs::read(path)
        .with_context(|| format!("Failed to read {}", path.display()))
        .unwrap();
    let time = Instant::now();
    for _ in 0..*REPETITION_COUNT {
        action(&source_code);
    }
    let duration = time.elapsed() / (*REPETITION_COUNT as u32);
    let duration_ns = duration.as_nanos();
    let speed = ((source_code.len() as u128) * 1_000_000) / duration_ns;
    info!(
        "    {:max_path_length$}\ttime {:>7.2} ms\t\tspeed {speed:>6} bytes/ms",
        path.file_name().unwrap().to_str().unwrap(),
        (duration_ns as f64) / 1e6,
    );
    speed as usize
}

fn get_language(path: &Path) -> Language {
    let src_path = GRAMMARS_DIR.join(path).join("src");
    TEST_LOADER
        .load_language_at_path(CompileConfig::new(&src_path, None, None))
        .with_context(|| format!("Failed to load language at path {}", src_path.display()))
        .unwrap()
}
