//! Starting server processes: binary resolution and the [`Launcher`] seam.

use ide_core::CancellationToken;
use ide_jsonrpc::{Handler, Peer};
use ide_language::LanguageServerConfig;
use std::ffi::OsString;
use std::path::{Path, PathBuf};
use std::sync::{Arc, OnceLock};

#[derive(Debug)]
pub enum LaunchError {
    /// The server binary is not installed / not on `PATH`.
    Missing,
    /// The configuration can't be launched (`LanguageServerConfig::launch_error`).
    Config(String),
    Failed(String),
}

/// Starts a language server and returns a connected peer. The default
/// [`ProcessLauncher`] spawns the configured command; tests substitute
/// in-memory servers.
pub trait Launcher: Send + Sync + 'static {
    fn launch(
        &self,
        config: &LanguageServerConfig,
        root: &Path,
        handler: Arc<dyn Handler>,
        on_stderr: Box<dyn Fn(String) + Send + Sync>,
    ) -> Result<Peer, LaunchError>;

    /// [`Launcher::launch`] that gives up once `cancel` fires (the server was stopped
    /// while still starting). Launchers that return at once need not override it.
    fn launch_cancellable(
        &self,
        config: &LanguageServerConfig,
        root: &Path,
        handler: Arc<dyn Handler>,
        on_stderr: Box<dyn Fn(String) + Send + Sync>,
        cancel: &CancellationToken,
    ) -> Result<Peer, LaunchError> {
        let _ = cancel;
        self.launch(config, root, handler, on_stderr)
    }

    /// Whether `config` could start without a `Missing` error.
    fn available(&self, _config: &LanguageServerConfig, _root: &Path) -> bool {
        true
    }
}

/// Resolves `command` on an augmented `PATH` and spawns it with stdio transport,
/// or for a `connect` server reaches it over TCP (see [`crate::tcp`]).
pub struct ProcessLauncher;

impl Launcher for ProcessLauncher {
    fn launch(
        &self,
        config: &LanguageServerConfig,
        root: &Path,
        handler: Arc<dyn Handler>,
        on_stderr: Box<dyn Fn(String) + Send + Sync>,
    ) -> Result<Peer, LaunchError> {
        self.launch_cancellable(config, root, handler, on_stderr, &CancellationToken::new())
    }

    fn launch_cancellable(
        &self,
        config: &LanguageServerConfig,
        root: &Path,
        handler: Arc<dyn Handler>,
        on_stderr: Box<dyn Fn(String) + Send + Sync>,
        cancel: &CancellationToken,
    ) -> Result<Peer, LaunchError> {
        let search = server_search_path(config);
        let binary = which::which_in(&config.command, Some(&search), root)
            .ok()
            .map(|b| resolve_rustup_proxy(&config.command, b));
        let mut env: Vec<(String, String)> = vec![("PATH".into(), search.to_string_lossy().into_owned())];
        env.extend(config.env.iter().filter(|(k, _)| *k != "PATH").map(|(k, v)| (k.clone(), v.clone())));
        if let Some(addr) = &config.connect {
            return crate::tcp::connect_or_start(
                config,
                addr,
                binary.as_deref(),
                &env,
                root,
                handler,
                on_stderr,
                cancel,
            );
        }
        let binary = binary.ok_or(LaunchError::Missing)?;
        Peer::spawn(&binary.to_string_lossy(), &config.args, root, &env, handler, on_stderr)
            .map_err(|e| LaunchError::Failed(format!("failed to start {}: {e}", binary.display())))
    }

    fn available(&self, config: &LanguageServerConfig, root: &Path) -> bool {
        which::which_in(&config.command, Some(server_search_path(config)), root).is_ok()
    }
}

/// A configured `PATH` (e.g. a selected toolchain prepended) also resolves the binary.
fn server_search_path(config: &LanguageServerConfig) -> OsString {
    config.env.get("PATH").map(OsString::from).unwrap_or_else(search_path)
}

/// `PATH` plus the login shell's `PATH` and common tool directories, so
/// servers resolve even when the app is launched from a GUI shell with a
/// minimal environment.
/// `~/.cargo/bin/<tool>` is usually a rustup proxy that fails when the active
/// toolchain lacks the component (common for rust-analyzer). In that case use
/// the newest installed toolchain that ships the binary.
fn resolve_rustup_proxy(command: &str, binary: PathBuf) -> PathBuf {
    let is_proxy = binary.parent().is_some_and(|d| d.ends_with(".cargo/bin"));
    if !is_proxy || command.contains('/') {
        return binary;
    }
    let works = ide_core::process::no_window(&mut std::process::Command::new(&binary))
        .arg("--version")
        .stdin(std::process::Stdio::null())
        .stdout(std::process::Stdio::null())
        .stderr(std::process::Stdio::null())
        .status()
        .is_ok_and(|s| s.success());
    if works {
        return binary;
    }
    let toolchains = std::env::var_os("RUSTUP_HOME")
        .map(PathBuf::from)
        .or_else(|| std::env::var_os("HOME").map(|h| PathBuf::from(h).join(".rustup")))
        .map(|h| h.join("toolchains"));
    let mut candidates: Vec<(std::time::SystemTime, PathBuf)> = toolchains
        .and_then(|dir| std::fs::read_dir(dir).ok())
        .into_iter()
        .flatten()
        .flatten()
        .map(|e| e.path().join("bin").join(command))
        .filter(|p| p.is_file())
        .filter_map(|p| Some((p.metadata().ok()?.modified().ok()?, p)))
        .collect();
    // Prefer stable-looking toolchains, then the most recently installed.
    candidates.sort_by_key(|(mtime, p)| (!p.to_string_lossy().contains("nightly"), *mtime));
    match candidates.pop() {
        Some((_, path)) => {
            tracing::info!("using {} instead of the rustup proxy", path.display());
            path
        }
        None => binary,
    }
}

pub fn search_path() -> OsString {
    static PATH: OnceLock<OsString> = OnceLock::new();
    PATH.get_or_init(|| {
        let mut dirs: Vec<PathBuf> =
            std::env::var_os("PATH").map(|p| std::env::split_paths(&p).collect()).unwrap_or_default();
        if let Some(shell_path) = login_shell_path() {
            dirs.extend(std::env::split_paths(&shell_path));
        }
        if let Some(home) = std::env::var_os("HOME").or_else(|| std::env::var_os("USERPROFILE")).map(PathBuf::from) {
            for rel in [".cargo/bin", ".local/bin", "go/bin", ".bun/bin", ".deno/bin", ".npm-global/bin", ".volta/bin"]
            {
                dirs.push(home.join(rel));
            }
            // nvm: newest installed node's bin.
            if let Ok(entries) = std::fs::read_dir(home.join(".nvm/versions/node")) {
                let mut versions: Vec<PathBuf> = entries.flatten().map(|e| e.path().join("bin")).collect();
                versions.sort();
                dirs.extend(versions.into_iter().rev());
            }
        }
        for d in ["/opt/homebrew/bin", "/usr/local/bin", "/usr/bin", "/bin"] {
            dirs.push(PathBuf::from(d));
        }
        let mut seen = std::collections::HashSet::new();
        dirs.retain(|d| !d.as_os_str().is_empty() && seen.insert(d.clone()));
        std::env::join_paths(dirs).unwrap_or_default()
    })
    .clone()
}

#[cfg(unix)]
fn login_shell_path() -> Option<OsString> {
    use std::io::Read;
    use std::process::{Command, Stdio};
    use std::time::{Duration, Instant};
    let shell = std::env::var_os("SHELL")?;
    const MARK: &str = "__OPENIDEA_PATH__";
    let mut child = Command::new(shell)
        .args(["-l", "-c", &format!("printf '{MARK}%s{MARK}' \"$PATH\"")])
        .stdin(Stdio::null())
        .stdout(Stdio::piped())
        .stderr(Stdio::null())
        .spawn()
        .ok()?;
    let deadline = Instant::now() + Duration::from_secs(3);
    loop {
        match child.try_wait() {
            Ok(Some(_)) => break,
            Ok(None) if Instant::now() < deadline => std::thread::sleep(Duration::from_millis(10)),
            _ => {
                let _ = child.kill();
                let _ = child.wait();
                return None;
            }
        }
    }
    let mut out = String::new();
    child.stdout.take()?.read_to_string(&mut out).ok()?;
    let start = out.find(MARK)? + MARK.len();
    let end = start + out[start..].find(MARK)?;
    Some(OsString::from(&out[start..end]))
}

#[cfg(not(unix))]
fn login_shell_path() -> Option<OsString> {
    None
}

/// Workspace root for `file`: the outermost ancestor within `project_root`
/// containing a root marker (so a Cargo/npm workspace gets one server, not one
/// per member), else `project_root`. `None` when `file` is outside the project.
pub fn find_root(project_root: &Path, file: &Path, markers: &[String]) -> Option<PathBuf> {
    if !file.starts_with(project_root) {
        return None;
    }
    let mut best = None;
    for dir in file.ancestors().skip(1) {
        if !dir.starts_with(project_root) {
            break;
        }
        if markers.iter().any(|m| has_marker(dir, m)) {
            best = Some(dir.to_path_buf());
        }
    }
    Some(best.unwrap_or_else(|| project_root.to_path_buf()))
}

fn has_marker(dir: &Path, marker: &str) -> bool {
    if !marker.contains('*') {
        return dir.join(marker).exists();
    }
    let (prefix, suffix) = marker.split_once('*').unwrap_or((marker, ""));
    std::fs::read_dir(dir).is_ok_and(|entries| {
        entries.flatten().any(|e| {
            let name = e.file_name();
            let name = name.to_string_lossy();
            name.len() >= prefix.len() + suffix.len() && name.starts_with(prefix) && name.ends_with(suffix)
        })
    })
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn root_detection() {
        let tmp = std::env::temp_dir().join(format!("openidea-lsp-root-{}", std::process::id()));
        let member = tmp.join("crates/a/src");
        std::fs::create_dir_all(&member).unwrap();
        std::fs::write(tmp.join("crates/a/Cargo.toml"), "").unwrap();
        let markers = vec!["Cargo.toml".to_string()];
        let file = member.join("lib.rs");
        assert_eq!(find_root(&tmp, &file, &markers), Some(tmp.join("crates/a")));
        std::fs::write(tmp.join("Cargo.toml"), "").unwrap();
        assert_eq!(find_root(&tmp, &file, &markers), Some(tmp.clone()));
        assert_eq!(find_root(&tmp.join("crates"), &file, &["*.toml".into()]), Some(tmp.join("crates/a")));
        assert_eq!(find_root(&tmp, Path::new("/elsewhere/x.rs"), &markers), None);
        assert_eq!(find_root(&tmp.join("crates"), &tmp.join("crates/b.rs"), &markers), Some(tmp.join("crates")));
        std::fs::remove_dir_all(&tmp).unwrap();
    }

    #[test]
    fn search_path_contains_env_path() {
        let p = search_path();
        let dirs: Vec<PathBuf> = std::env::split_paths(&p).collect();
        assert!(dirs.contains(&PathBuf::from("/usr/bin")));
    }
}

#[cfg(test)]
mod proxy_tests {
    use super::*;

    #[test]
    fn non_proxy_binaries_are_kept() {
        let p = PathBuf::from("/usr/bin/true");
        assert_eq!(resolve_rustup_proxy("true", p.clone()), p);
    }

    /// Exercises the real machine setup when a broken rustup proxy is present.
    #[test]
    #[ignore]
    fn broken_rustup_proxy_falls_back_to_a_toolchain() {
        let home = PathBuf::from(std::env::var_os("HOME").unwrap());
        let proxy = home.join(".cargo/bin/rust-analyzer");
        let resolved = resolve_rustup_proxy("rust-analyzer", proxy.clone());
        eprintln!("resolved: {}", resolved.display());
        assert_ne!(resolved, proxy);
    }
}