//! Tiny hash-based router.
//!
//! - `#/` — root picker / single-root browser
//! - `#/files/{root_id}/{segment/...}` — a user's folder
//! - `#/shares/{token}/{segment/...}` — a public share (no login)
//! - `#/shares`, `#/users`, `#/settings` — the signed-in shell's manage views
//!
//! (`#/shares` with a token is the public share; without one it is the
//! manage view that lists your own shares.)
//!
//! The URL hash is the single source of truth; the `Location` signal in the
//! app mirrors it.

/// Which section of the signed-in shell a location points at. `Files` is the
/// browser; the rest are the manage views, each with its own URL.
#[derive(Clone, Copy, PartialEq, Eq, Debug)]
pub enum Section {
    Files,
    /// The search view (`#/search`); query params live in the hash query.
    Search,
    Shares,
    Users,
    Settings,
}

impl Section {
    /// The URL segment for this section, or `None` for `Files` (which has no
    /// segment of its own — the browser is the default view).
    const fn segment(self) -> Option<&'static str> {
        match self {
            Section::Files => None,
            Section::Search => Some("search"),
            Section::Shares => Some("shares"),
            Section::Users => Some("users"),
            Section::Settings => Some("settings"),
        }
    }
}

#[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 (or share target).
    pub path: Vec<String>,
    /// Present when the location is a public share (`#/s/{token}/...`).
    pub share_token: Option<String>,
    /// Which shell section the location points at.
    pub section: Section,
}

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

/// Percent-encode one path segment for the URL hash. Without this a name
/// containing `#`, `%` or `/` would break the round trip.
fn encode_segment(seg: &str) -> String {
    js_sys::encode_uri_component(seg).into()
}

fn decode_segment(seg: &str) -> String {
    // A hand-typed hash can hold invalid escapes; keep it verbatim then.
    js_sys::decode_uri_component(seg)
        .map(String::from)
        .unwrap_or_else(|_| seg.to_string())
}

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('/');
    // Hash query (e.g. `#/search?q=…`) is not part of the path; the search
    // view parses it itself.
    let h = h.split_once('?').map(|(p, _)| p).unwrap_or(h);
    let mut parts = h.split('/').filter(|s| !s.is_empty());
    match parts.next() {
        Some("files") => match parts.next().and_then(|s| s.parse().ok()) {
            Some(root_id) => Location {
                root_id: Some(root_id),
                path: parts.map(decode_segment).collect(),
                share_token: None,
                section: Section::Files,
            },
            None => Location::root(),
        },
        Some("search") => Location {
            root_id: None,
            path: Vec::new(),
            share_token: None,
            section: Section::Search,
        },
        Some("shares") => match parts.next() {
            // `#/shares/{token}/...` — public share page.
            Some(token) => Location {
                root_id: None,
                path: parts.map(decode_segment).collect(),
                share_token: Some(token.to_string()),
                section: Section::Files,
            },
            // `#/shares` — the signed-in shares manage view.
            None => Location {
                root_id: None,
                path: Vec::new(),
                share_token: None,
                section: Section::Shares,
            },
        },
        Some("users") => Location {
            root_id: None,
            path: Vec::new(),
            share_token: None,
            section: Section::Users,
        },
        Some("settings") => Location {
            root_id: None,
            path: Vec::new(),
            share_token: None,
            section: Section::Settings,
        },
        _ => Location::root(),
    }
}

pub fn location_to_hash(loc: &Location) -> String {
    if let Some(token) = &loc.share_token {
        let mut s = format!("#/shares/{token}");
        for seg in &loc.path {
            s.push('/');
            s.push_str(&encode_segment(seg));
        }
        return s;
    }
    if let Some(segment) = loc.section.segment() {
        return format!("#/{segment}");
    }
    match loc.root_id {
        None => "#/".to_string(),
        Some(id) => {
            let mut s = format!("#/files/{id}");
            for seg in &loc.path {
                s.push('/');
                s.push_str(&encode_segment(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));
    }
}

/// Build the share link for a token, relative to the current page origin.
pub fn share_url(token: &str) -> String {
    let base = web_sys::window()
        .and_then(|w| w.location().href().ok())
        .unwrap_or_default();
    // Cut off any existing hash, then append the share hash.
    let cut = base.find('#').unwrap_or(base.len());
    format!("{}#/shares/{token}", &base[..cut])
}