//! Tiny hash-based router: `#/r/{root_id}/{segment/...}` (files) or `#/`
//! (root picker). The URL hash is the single source of truth; the
//! `Location` signal in the app mirrors it.

#[derive(Clone, Debug, PartialEq, Eq)]
pub struct Location {
    /// None = the top-level "folders" view (root picker).
    pub root_id: Option<i64>,
    /// Path segments relative to the current root.
    pub path: Vec<String>,
}

impl Location {
    pub const fn root() -> Self {
        Self {
            root_id: None,
            path: Vec::new(),
        }
    }
}

pub fn parse_location() -> Location {
    let hash = web_sys::window()
        .and_then(|w| w.location().hash().ok())
        .unwrap_or_default();
    let h = hash.trim_start_matches('#');
    let h = h.trim_start_matches('/');
    let mut parts = h.split('/').filter(|s| !s.is_empty());
    match parts.next() {
        Some("r") => match parts.next().and_then(|s| s.parse().ok()) {
            Some(root_id) => Location {
                root_id: Some(root_id),
                path: parts.map(String::from).collect(),
            },
            None => Location::root(),
        },
        _ => Location::root(),
    }
}

pub fn location_to_hash(loc: &Location) -> String {
    match loc.root_id {
        None => "#/".to_string(),
        Some(id) => {
            let mut s = format!("#/r/{id}");
            for seg in &loc.path {
                s.push('/');
                s.push_str(seg);
            }
            s
        }
    }
}

/// Change the app location (updates the hash; the app listens for hashchange).
pub fn navigate(loc: &Location) {
    if let Some(w) = web_sys::window() {
        let _ = w.location().set_hash(&location_to_hash(loc));
    }
}