// ────────────────────────────────────────────────────────────────────
// StreamHeader geometry — shared constants for the curtain layout.
//
// Mental model: the chats card is a curtain layered ABOVE the header
// (z-index higher). The curtain's `top` is the visible part of the
// header below the always-pinned tabs row. When the curtain is fully
// closed it sits flush under the tabs row (covering chips + form area
// beneath). Dragging it DOWN reveals more of the header from underneath.
// Dragging UP raises the curtain back over the header.
//
// Snap stops (curtain.top, px):
//   pinned       = 0  (curtain sits flush at top of the stage, tabs row
//                      covered; the safe-top status-bar strip above the
//                      stage stays painted by the surrounding context —
//                      see «pinned visual contract» below)
//   closed       = TABS_ROW_PX
//   peek         = TABS_ROW_PX + 2·CHIP_ROW_PX + CHIP_GAP_PX
//                              + CURTAIN_BREATHER_PX
//   form:*       = TABS_ROW_PX + formHeight + CURTAIN_BREATHER_PX
//
// Pinned visual contract: at `pinned` the curtain's top edge lands at
// y = safe-top in viewport coords (because the stage starts after the
// PageNav / appBody padding-top: var(--vojo-safe-top)). The system tray
// strip stays painted by appBody / PageNav-inner / MobileTabsPager's
// static header — all of which use `SurfaceVariant.Container` for that
// zone, so the colour is continuous across surfaces. The curtain MUST
// NOT extend into the safe-top zone (otherwise system text is covered)
// and MUST NOT add internal padding-top (otherwise the chat list grows
// visually taller). The clamp on the up-drag (= -TABS_ROW_PX) enforces
// the first invariant; we deliberately do not add any padding inside
// the curtain to enforce the second.
// ────────────────────────────────────────────────────────────────────

// Tabs row height. Always visible above the curtain.
export const TABS_ROW_PX = 64;

// Each peek-chip row. Reveals one chip's pill (h=48) + 8px top breather.
export const CHIP_ROW_PX = 56;

// Vertical gap BETWEEN two consecutive chip rows. Separate from
// `CURTAIN_BREATHER_PX` so the inter-chip spacing can read tighter
// than the breather between the last chip and the curtain's rounded
// top (the curtain's straight edge against a chip pill needs more
// air to avoid feeling «clamped», while two pills sitting in a
// vertical stack want to read as a pair).
export const CHIP_GAP_PX = 14;

// Initial estimate for the search form's outer height. The actual
// height is measured at runtime via ResizeObserver and adapts to the
// available viewport so the form never overflows the chats card.
export const SEARCH_FORM_BASE_PX = 360;

// Breathing strip between the bottom of any header content (revealed
// chip pill, form's last actionable element) and the top of the
// curtain. Painted by the header's `SurfaceVariant.Container` (light-
// blue) so the chip / Create button / search results never visually
// touch the curtain's rounded top — the user reads chips that sit
// flush with the curtain as «зажатые» rather than two separate
// affordances. Not applied at `closed` (nothing to breathe to).
export const CURTAIN_BREATHER_PX = 20;

// Curtain snap transition. Tuned tight for an in-app reveal —
// emphasized-decelerate territory.
export const CURTAIN_SNAP_MS = 280;
export const CURTAIN_SNAP_EASING = 'cubic-bezier(0.22, 1, 0.36, 1)';

// Curtain card top-corner radius. Matches the composer card and the
// horseshoe surfaces elsewhere in the app.
export const CURTAIN_RADIUS_PX = 24;

// Total vertical travel of the curtain between `closed` and `peek` —
// the resting-top delta between the two snaps. Used as the basis for
// the peek-commit threshold: the user must drag (rubber-banded) at
// least COMMIT_THRESHOLD × PEEK_TRAVEL_PX before release for the snap
// to flip. Anything shorter reads as accidental and springs back.
export const PEEK_TRAVEL_PX = CHIP_ROW_PX + CHIP_GAP_PX + CHIP_ROW_PX + CURTAIN_BREATHER_PX;

// Touch gesture tuning. RUBBER_BAND dampens finger→curtain motion so
// the chip reveal feels resistive; COMMIT_THRESHOLD is the fraction of
// the full peek travel the user must cross on release for the snap to
// commit. Tuned high (≈90%) so anything below «дотянул почти до конца»
// reads as accidental and snaps back to `closed`.
export const RUBBER_BAND = 0.65;
export const DIRECTION_DEAD_ZONE_PX = 10;
export const COMMIT_THRESHOLD = 0.9;
// Pull-up distance (raw finger px) required to close an active form.
export const ACTIVE_CLOSE_THRESHOLD_PX = 100;

// Total vertical CURTAIN travel for the closed ↔ pinned gesture.
// Equals the tabs row height because pinning lifts the curtain by
// exactly that distance (from y = TABS_ROW_PX down to y = 0 inside
// the stage).
export const PIN_TRAVEL_PX = TABS_ROW_PX;

// Commit threshold for pin / unpin. Tuned very high (≈95%) so the
// user must drag the curtain almost-all-the-way to the cap before
// release for the snap to flip. Anything shorter reads as accidental
// and springs back to the previous resting snap.
//
// With 1:1 finger ↔ curtain tracking (no rubber-band on pin / unpin
// — see `useCurtainGesture` and `useCurtainHandleGesture`), the
// committing finger pull is `PIN_COMMIT_THRESHOLD × PIN_TRAVEL_PX` ≈
// 61 px — essentially «drag the curtain across the full tabs-row
// height». The anti-accidental gate that previously came from
// rubber-band amplification is now provided by the dedicated handle
// hit-zone (intentional surface) plus the list-bound scroll-aware
// bail (no list scroll = no scroll-up to confuse with pin).
export const PIN_COMMIT_THRESHOLD = 0.95;

// Drag-handle hit-zone at the top of the curtain. Hosts the pin /
// unpin gesture as a dedicated touch surface so it doesn't compete
// with the chat list's vertical scroll. Drag on this handle tracks
// the finger 1:1 (no rubber-band) — finger displacement equals
// curtain displacement. The list-bound gesture in
// `useCurtainGesture` still owns peek / form-close, plus the pin path
// when the list has no scrollable content (so single-screen lists
// keep the «drag-from-anywhere» pin behaviour).
//
// Size: 32 px tall — enough touch target to land on comfortably with
// a thumb (the visible grabber pill inside is much smaller, see
// `StreamHeader.css.ts::handleBar`). The list (or DirectEmpty / the
// equivalent placeholder) starts 32 px below the curtain's top edge.
export const HANDLE_HEIGHT_PX = 32;