//! Formatting + small browser helpers.

use leptos::prelude::*;
use wasm_bindgen::JsCast;
use wasm_bindgen::closure::Closure;

/// A window event listener that is removed when the current owner is disposed.
///
/// Leptos' `window_event_listener` returns a `WindowListenerHandle` with no
/// `Drop` impl — if the owning component is unmounted without an explicit
/// `remove()`, the listener keeps firing on `window` and panics by reading
/// the component's now-disposed signals.
pub fn owned_window_listener<E: leptos::ev::EventDescriptor + 'static>(
    event: E,
    cb: impl Fn(E::EventType) + 'static,
) where
    E::EventType: wasm_bindgen::JsCast,
{
    let handle = window_event_listener(event, cb);
    on_cleanup(move || handle.remove());
}

/// Same as [`owned_window_listener`], but registered in the capture phase,
/// so it runs before the bubble-phase window listeners (registration order
/// otherwise decides, and that depends on component creation order).
pub fn owned_window_listener_capture<E: leptos::ev::EventDescriptor + 'static>(
    event: E,
    cb: impl Fn(E::EventType) + 'static,
) where
    E::EventType: wasm_bindgen::JsCast,
{
    let closure = Closure::<dyn FnMut(web_sys::Event)>::new({
        move |e: web_sys::Event| cb(e.unchecked_into::<E::EventType>())
    });
    let add_options = web_sys::AddEventListenerOptions::new();
    add_options.set_capture(true);
    let remove_options = web_sys::EventListenerOptions::new();
    remove_options.set_capture(true);
    let name = event.name();
    web_sys::window()
        .expect("window")
        .add_event_listener_with_callback_and_add_event_listener_options(
            &name,
            closure.as_ref().unchecked_ref(),
            &add_options,
        )
        .expect("failed to add window event listener");
    let closure_js = closure.into_js_value();
    on_cleanup(move || {
        let closure: js_sys::Function = closure_js.unchecked_into();
        let _ = web_sys::window()
            .expect("window")
            .remove_event_listener_with_callback_and_event_listener_options(
                &name,
                &closure,
                &remove_options,
            );
    });
}

/// The value of a `<select>` behind an event, when the target is one.
pub fn select_value(ev: &web_sys::Event) -> Option<String> {
    ev.target()
        .and_then(|t| t.dyn_into::<web_sys::HtmlSelectElement>().ok())
        .map(|s| s.value())
}

pub fn format_size(bytes: u64) -> String {
    const UNITS: [&str; 5] = ["B", "KB", "MB", "GB", "TB"];
    let mut v = bytes as f64;
    let mut i = 0;
    while v >= 1024.0 && i < UNITS.len() - 1 {
        v /= 1024.0;
        i += 1;
    }
    if i == 0 {
        format!("{bytes} B")
    } else {
        format!("{v:.1} {}", UNITS[i])
    }
}

/// Format an RFC 3339 timestamp as "YYYY-MM-DD HH:MM" (UTC) for display.
/// Falls back to the raw string when it does not look like one.
///
/// Every timestamp the server sends is UTC with a `Z` suffix, so the display
/// text is a slice of the input. No date parsing is needed.
pub fn format_date(rfc3339: &str) -> String {
    let b = rfc3339.as_bytes();
    if b.len() >= 16 && b[10] == b'T' {
        return format!("{} {}", &rfc3339[..10], &rfc3339[11..16]);
    }
    rfc3339.to_string()
}

pub fn storage_get(key: &str) -> Option<String> {
    let w = web_sys::window()?;
    let storage_opt = w.local_storage().ok()?;
    let storage = storage_opt.as_ref()?;
    storage.get_item(key).ok().flatten()
}

pub fn storage_set(key: &str, value: &str) {
    if let Some(s) = web_sys::window().and_then(|w| w.local_storage().ok().flatten()) {
        let _ = s.set_item(key, value);
    }
}

#[derive(Clone, Copy, PartialEq, Debug)]
pub enum ViewMode {
    Grid,
    List,
}

impl ViewMode {
    const KEY: &'static str = "fbng.view";

    pub fn load() -> Self {
        match storage_get(Self::KEY).as_deref() {
            Some("list") => ViewMode::List,
            _ => ViewMode::Grid,
        }
    }

    pub fn save(self) {
        storage_set(
            Self::KEY,
            if self == ViewMode::List {
                "list"
            } else {
                "grid"
            },
        );
    }
}

/// What a listing is ordered by. Folders always sort before files, so a
/// size or date order does not scatter them through the listing.
#[derive(Clone, Copy, PartialEq, Eq, Debug)]
pub enum SortKey {
    Name,
    Size,
    Modified,
}

impl SortKey {
    pub fn as_str(self) -> &'static str {
        match self {
            SortKey::Name => "name",
            SortKey::Size => "size",
            SortKey::Modified => "modified",
        }
    }

    pub fn parse(s: &str) -> Option<Self> {
        match s {
            "name" => Some(SortKey::Name),
            "size" => Some(SortKey::Size),
            "modified" => Some(SortKey::Modified),
            _ => None,
        }
    }
}

/// A sort key plus its direction, persisted like [`ViewMode`].
#[derive(Clone, Copy, PartialEq, Eq, Debug)]
pub struct SortSpec {
    pub key: SortKey,
    pub asc: bool,
}

impl Default for SortSpec {
    fn default() -> Self {
        // The server's own order, so the first paint after a fetch does not
        // reshuffle.
        Self {
            key: SortKey::Name,
            asc: true,
        }
    }
}

impl SortSpec {
    const KEY: &'static str = "fbng.sort";

    pub fn load() -> Self {
        let raw = storage_get(Self::KEY).unwrap_or_default();
        let (key, dir) = raw.split_once(':').unwrap_or(("", ""));
        match SortKey::parse(key) {
            Some(key) => Self {
                key,
                asc: dir != "desc",
            },
            None => Self::default(),
        }
    }

    pub fn save(self) {
        let dir = if self.asc { "asc" } else { "desc" };
        storage_set(Self::KEY, &format!("{}:{dir}", self.key.as_str()));
    }

    /// Order `entries` in place.
    ///
    /// Name is compared case-insensitively, with the raw name as the
    /// tie-breaker so two names differing only in case keep a stable order.
    /// Folders have no meaningful size, so they fall back to the name order
    /// among themselves.
    pub fn apply(self, entries: &mut [crate::api::Entry]) {
        match self.key {
            SortKey::Name => entries.sort_by(|a, b| {
                a.is_dir
                    .cmp(&b.is_dir)
                    .reverse()
                    .then_with(|| cmp_name(a, b).dir(self.asc))
            }),
            SortKey::Size => entries.sort_by(|a, b| {
                a.is_dir.cmp(&b.is_dir).reverse().then_with(|| {
                    if a.is_dir {
                        cmp_name(a, b)
                    } else {
                        a.size
                            .cmp(&b.size)
                            .dir(self.asc)
                            .then_with(|| cmp_name(a, b))
                    }
                })
            }),
            SortKey::Modified => entries.sort_by(|a, b| {
                a.is_dir.cmp(&b.is_dir).reverse().then_with(|| {
                    // RFC 3339 UTC with a fixed width, so bytewise order is
                    // chronological order.
                    a.mtime
                        .cmp(&b.mtime)
                        .dir(self.asc)
                        .then_with(|| cmp_name(a, b))
                })
            }),
        }
    }
}

fn cmp_name(a: &crate::api::Entry, b: &crate::api::Entry) -> std::cmp::Ordering {
    a.name
        .to_lowercase()
        .cmp(&b.name.to_lowercase())
        .then_with(|| a.name.cmp(&b.name))
}

trait OrderingDir {
    fn dir(self, asc: bool) -> std::cmp::Ordering;
}

impl OrderingDir for std::cmp::Ordering {
    fn dir(self, asc: bool) -> std::cmp::Ordering {
        if asc { self } else { self.reverse() }
    }
}

/// Entries rendered at once in a listing, and how many more each click of
/// the "show more" row reveals. Rendering a row costs a fixed amount of
/// reactive-graph setup, so the first paint stays well under a frame and the
/// user pays for more rows only by asking for them.
pub const FILE_PAGE: usize = 100;

/// Footer under a paged list: where the user is in the list, and a button
/// to reveal the next page.
///
/// `shown` of `total` is stated plainly rather than only counting what is
/// hidden — "Showing 100 of 6027" answers "where am I?", which a bare
/// "5927 more…" does not. The button appears only while more items are
/// actually retained; past the caller's retain cap the count is all that is
/// left to say, so the footer becomes a plain line.
///
/// Returns nothing at all when everything is on screen.
pub fn page_footer(
    shown: usize,
    retained: usize,
    total: usize,
    page: usize,
    reveal: impl Fn() + 'static,
) -> AnyView {
    if total <= shown {
        return view! {}.into_view().into_any();
    }
    let label = crate::i18n::t_fmt2(
        crate::i18n::k::SEARCH_SHOWN_OF,
        &shown.to_string(),
        &total.to_string(),
    );
    let pageable = retained.saturating_sub(shown);
    if pageable == 0 {
        return view! { <div class="page-foot">{label}</div> }
            .into_view()
            .into_any();
    }
    let next = pageable.min(page);
    view! {
        <div class="page-foot">
            <span class="pf-count">{label}</span>
            <button class="pf-more" on:click=move |_| reveal()>
                {crate::i18n::t_fmt(crate::i18n::k::SEARCH_SHOW_MORE, &next.to_string())}
            </button>
        </div>
    }
    .into_view()
    .into_any()
}

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

    fn entry(name: &str, is_dir: bool, size: u64, mtime: &str) -> crate::api::Entry {
        crate::api::Entry {
            name: name.to_string(),
            is_dir,
            size,
            mtime: mtime.to_string(),
            kind: if is_dir {
                api_types::FileKind::Dir
            } else {
                api_types::FileKind::Binary
            },
        }
    }

    /// This order is what the browser's arrow keys and Shift+click ranges
    /// walk, so a wrong order moves the wrong file.
    #[test]
    fn sort_keeps_folders_first_in_every_order() {
        let mut v = vec![
            entry("b.txt", false, 10, "2026-01-02T00:00:00Z"),
            entry("Zdir", true, 0, "2026-01-01T00:00:00Z"),
            entry("a.txt", false, 30, "2026-01-03T00:00:00Z"),
        ];
        for key in [SortKey::Name, SortKey::Size, SortKey::Modified] {
            for asc in [true, false] {
                SortSpec { key, asc }.apply(&mut v);
                assert!(v[0].is_dir, "{key:?} asc={asc} put a file first");
            }
        }
    }

    #[test]
    fn sort_orders_by_the_chosen_key() {
        let mut v = vec![
            entry("b.txt", false, 10, "2026-01-02T00:00:00Z"),
            entry("a.txt", false, 30, "2026-01-03T00:00:00Z"),
            entry("c.txt", false, 20, "2026-01-01T00:00:00Z"),
        ];
        let names = |v: &[crate::api::Entry]| v.iter().map(|e| e.name.clone()).collect::<Vec<_>>();

        SortSpec {
            key: SortKey::Name,
            asc: true,
        }
        .apply(&mut v);
        assert_eq!(names(&v), ["a.txt", "b.txt", "c.txt"]);
        SortSpec {
            key: SortKey::Name,
            asc: false,
        }
        .apply(&mut v);
        assert_eq!(names(&v), ["c.txt", "b.txt", "a.txt"]);

        SortSpec {
            key: SortKey::Size,
            asc: true,
        }
        .apply(&mut v);
        assert_eq!(names(&v), ["b.txt", "c.txt", "a.txt"]);
        SortSpec {
            key: SortKey::Modified,
            asc: true,
        }
        .apply(&mut v);
        assert_eq!(names(&v), ["c.txt", "b.txt", "a.txt"]);
    }

    #[test]
    fn sort_spec_round_trips_through_its_stored_form() {
        // No localStorage in the test runner, so only the parse half runs
        // here. `load` falls back to the default.
        assert_eq!(SortKey::parse("size"), Some(SortKey::Size));
        assert_eq!(SortKey::parse("bogus"), None);
        assert_eq!(SortSpec::default().key, SortKey::Name);
        assert!(SortSpec::default().asc);
    }

    #[test]
    fn format_date_drops_seconds_and_zone() {
        assert_eq!(format_date("2026-09-11T12:34:56Z"), "2026-09-11 12:34");
        assert_eq!(format_date("nonsense"), "nonsense");
    }
}