//! Finding binaries on `PATH`.

use std::collections::BTreeMap;
use std::path::PathBuf;

/// The prefix every verb binary carries.
const PREFIX: &str = "didbot-";

/// The first executable named `name` on `PATH`, if there is one.
pub fn find(name: &str) -> Option<PathBuf> {
    let path = std::env::var_os("PATH")?;
    std::env::split_paths(&path)
        .map(|dir| dir.join(name))
        .find(|candidate| executable(candidate))
}

/// Every `didbot-*` on `PATH`, by name, the first on `PATH` winning — the
/// same one [`find`] would run.
pub fn installed() -> BTreeMap<String, PathBuf> {
    let mut found = BTreeMap::new();
    let Some(path) = std::env::var_os("PATH") else {
        return found;
    };
    for dir in std::env::split_paths(&path) {
        let Ok(entries) = std::fs::read_dir(&dir) else {
            continue;
        };
        for entry in entries.flatten() {
            let name = entry.file_name().to_string_lossy().into_owned();
            if name.len() > PREFIX.len() && name.starts_with(PREFIX) && executable(&entry.path()) {
                found.entry(name).or_insert_with(|| entry.path());
            }
        }
    }
    found
}

/// A regular file this process may run.
fn executable(candidate: &std::path::Path) -> bool {
    let Ok(metadata) = std::fs::metadata(candidate) else {
        return false;
    };
    if !metadata.is_file() {
        return false;
    }
    #[cfg(unix)]
    {
        use std::os::unix::fs::PermissionsExt;
        metadata.permissions().mode() & 0o111 != 0
    }
    #[cfg(not(unix))]
    {
        true
    }
}