//! Discovers installed language servers on the system PATH.

use std::collections::HashMap;

use super::config::LspProvisionerConfig;

/// Known language server configurations keyed by language.
fn known_configs() -> HashMap<&'static str, (&'static str, Vec<&'static str>)> {
    let mut m = HashMap::new();
    m.insert("rust", ("rust-analyzer", vec![]));
    m.insert("python", ("pyright-langserver", vec!["--stdio"]));
    m.insert(
        "typescript",
        ("typescript-language-server", vec!["--stdio"]),
    );
    m.insert(
        "javascript",
        ("typescript-language-server", vec!["--stdio"]),
    );
    m.insert("go", ("gopls", vec![]));
    m
}

/// Check if a command is available on PATH.
fn command_exists(cmd: &str) -> bool {
    std::env::var_os("PATH")
        .and_then(|path| {
            std::env::split_paths(&path).find_map(|dir| {
                let full_path = dir.join(cmd);
                if full_path.is_file() {
                    Some(())
                } else {
                    None
                }
            })
        })
        .is_some()
}

/// Discover which language servers are already on PATH.
pub fn discover_installed() -> Vec<LspProvisionerConfig> {
    let mut configs = Vec::new();
    for (lang, (cmd, args)) in known_configs() {
        if command_exists(cmd) {
            configs.push(LspProvisionerConfig {
                language: lang.to_string(),
                command: cmd.to_string(),
                args: args.iter().map(|s| s.to_string()).collect(),
                install_hint: None,
            });
        }
    }
    configs
}