use std::io;
use std::sync::OnceLock;

use parking_lot::Mutex;
use tracing_subscriber::layer::SubscriberExt;
use tracing_subscriber::registry::Registry;
use tracing_subscriber::util::SubscriberInitExt;
use tracing_subscriber::{EnvFilter, reload};

use crate::LauncherResult;

pub mod console;

/// The launcher's own crates given an explicit directive rather than falling
/// back to the base level
const APP_TARGETS: &[&str] = &[
    "oneclient_app",
    "oneclient_auth",
    "oneclient_cluster",
    "oneclient_common",
    "oneclient_content",
    "oneclient_core",
    "oneclient_db",
    "oneclient_discord",
    "oneclient_events",
    "oneclient_java",
    "oneclient_mc",
    "oneclient_net",
    "oneclient_polyplus",
    "polyio",
];

/// Pinned regardless of the base level because the debug filter raises the base
/// to `info` and that would otherwise let this lot flood the log
const NOISY_TARGETS: &[&str] = &[
    "calloop",
    "h2",
    "hickory_proto",
    "hickory_resolver",
    "html5ever",
    "hyper",
    "hyper_util",
    "mio",
    "quinn",
    "reqwest",
    "rustls",
    "smithay_client_toolkit",
    // Only `sqlx::query` `sqlx` proper reports pool and migration problems we want
    "sqlx::query",
    "tokio_util",
    "tower",
    "want",
    "winit",
    "zbus",
];

const UI_TARGETS: &[&str] = &[
    "freya",
    "freya_components",
    "freya_core",
    "freya_radio",
    "freya_winit",
    "ragnarok",
    "torin",
];

const UI_FLOOD_TARGETS: &[&str] = &[
    "freya_core::accessibility",
    "freya_core::runner",
    "freya_core::tree",
    "freya_winit::renderer",
	"freya::metrics",
    "ragnarok::executor",
    "ragnarok::nodes_state",
    "torin::torin",
];

/// Whether `target` belongs to one of [`APP_TARGETS`] rather than a dependency
fn is_app_target(target: &str) -> bool {
    APP_TARGETS.iter().any(|app| {
        target
            .strip_prefix(app)
            .is_some_and(|rest| rest.is_empty() || rest.starts_with("::"))
    })
}

fn sentry_event_filter(metadata: &tracing::Metadata<'_>) -> sentry_tracing::EventFilter {
    dependency_filter(*metadata.level(), metadata.target())
        .unwrap_or_else(|| sentry_tracing::default_event_filter(metadata))
}

/// `None` when the target is one of ours, meaning the default filter decides
fn dependency_filter(level: tracing::Level, target: &str) -> Option<sentry_tracing::EventFilter> {
    if is_app_target(target) {
        return None;
    }

    Some(match level {
        // Kept as context for a report of ours, but never a report of its own
        tracing::Level::ERROR => sentry_tracing::EventFilter::Breadcrumb,
        _ => sentry_tracing::EventFilter::Ignore,
    })
}

pub fn default_directives() -> String {
    directives("info", "warn")
}

/// Raises the base level too so an unlisted dependency's `info` still reaches
/// the log
pub fn debug_directives() -> String {
    directives("debug", "info")
}

fn directives(app_level: &str, base_level: &str) -> String {
    let mut out = String::from(base_level);
    for target in NOISY_TARGETS {
        out.push_str(&format!(",{target}=warn"));
    }
    for target in UI_TARGETS {
        out.push_str(&format!(",{target}=info"));
    }
    for target in UI_FLOOD_TARGETS {
        out.push_str(&format!(",{target}=warn"));
    }
    for target in APP_TARGETS {
        out.push_str(&format!(",{target}={app_level}"));
    }
    out
}

/// The filter layer sits directly on the [`Registry`] so that is the subscriber
/// type the reload handle is parameterised over
type FilterHandle = reload::Handle<EnvFilter, Registry>;

static FILTER: OnceLock<FilterHandle> = OnceLock::new();
static ACTIVE_DIRECTIVES: Mutex<String> = Mutex::new(String::new());

#[derive(Debug, thiserror::Error)]
pub enum FilterError {
    #[error("invalid log filter directives: {0}")]
    Invalid(String),

    #[error("the logger has not been initialized")]
    NotInitialized,
}

pub fn active_directives() -> String {
    ACTIVE_DIRECTIVES.lock().clone()
}

/// Swaps the active filter without restarting
/// Unparseable directives leave the previous filter in place rather than
/// blanking the log
pub fn set_filter(directives: &str) -> Result<(), FilterError> {
    let filter =
        EnvFilter::try_new(directives).map_err(|err| FilterError::Invalid(err.to_string()))?;

    FILTER
        .get()
        .ok_or(FilterError::NotInitialized)?
        .reload(filter)
        .map_err(|err| FilterError::Invalid(err.to_string()))?;

    *ACTIVE_DIRECTIVES.lock() = directives.to_string();
    tracing::info!(%directives, "log filter reloaded");

    Ok(())
}

pub fn init_debug() -> LauncherResult<()> {
    init_filtered(debug_directives)
}

pub fn init() -> LauncherResult<()> {
    init_filtered(default_directives)
}

pub fn init_filtered(filter: impl FnOnce() -> String) -> LauncherResult<()> {
    // `RUST_LOG` wins outright rather than merging appending ours would quietly
    // override the targets the user asked for
    let directives = std::env::var(EnvFilter::DEFAULT_ENV)
        .ok()
        .filter(|value| !value.trim().is_empty())
        .unwrap_or_else(filter);

    let env_filter = EnvFilter::try_new(&directives).unwrap_or_else(|_| {
        eprintln!(
            "ignoring unparseable {} filter: {directives}",
            EnvFilter::DEFAULT_ENV
        );
        EnvFilter::new(default_directives())
    });

    let (filter, handle) = reload::Layer::new(env_filter);
    let _ = FILTER.set(handle);
    *ACTIVE_DIRECTIVES.lock() = directives;

    let stdout_layer = tracing_subscriber::fmt::layer().with_writer(io::stdout);

    let sentry_layer = sentry_tracing::layer().event_filter(sentry_event_filter);

    #[cfg(debug_assertions)]
    {
        tracing_subscriber::registry()
            .with(filter)
            .with(stdout_layer)
            .with(console::layer())
            .with(sentry_layer)
            .init();
    }

    #[cfg(not(debug_assertions))]
    {
        let logs_dir = oneclient_common::paths::logs_dir()?;
        std::fs::create_dir_all(&logs_dir)?;

        let log_path = logs_dir.join(format!(
            "{}.log",
            chrono::Local::now().to_rfc3339().replace(':', "-")
        ));

        let file = std::fs::OpenOptions::new()
            .create(true)
            .append(true)
            .open(&log_path)?;

        let file_layer = tracing_subscriber::fmt::layer()
            .with_ansi(false)
            .with_writer(file);

        tracing_subscriber::registry()
            .with(filter)
            .with(stdout_layer)
            .with(file_layer)
            .with(console::layer())
            .with(sentry_layer)
            .init();

        tracing::info!(path = %log_path.display(), "writing logs to file");
    }

    Ok(())
}