// The channel manager's layout vocabulary (E4 S3). Named `ChannelLayout` — NOT `ChannelView` — on
// purpose: the manager already has a `ChannelsView` (the subscribed/discovery/blocked TAB), and a
// one-letter-apart type would be a footgun. This is the table-vs-card density switch, riding the
// same generic `ViewSwitcher` as the feed. Two layouts: the DataTable, and a virtualized card grid.
// (A `rows` variant existed briefly but was retired — it barely differed from the table.)
export type ChannelLayout = "table" | "cards";

export const CHANNEL_LAYOUTS: readonly ChannelLayout[] = ["table", "cards"] as const;

const CHANNEL_LAYOUT_DEFAULT: ChannelLayout = "table";

/** The `cards` layout's grid spec, consumed by VirtualGrid. `table` has no entry — it keeps the
 * numbered-pager DataTable, not the virtualized grid. */
export interface ChannelLayoutSpec {
  /** Narrowest grid column in px. */
  minCol: number;
  /** First-paint row-height estimate; real heights are measured per-row after. Measured in the
   * browser (channel heading + About line + meta + tags + actions), not guessed. */
  rowEst: number;
}

export const CHANNEL_LAYOUT_SPEC: Record<Exclude<ChannelLayout, "table">, ChannelLayoutSpec> = {
  cards: { minCol: 320, rowEst: 232 },
};

/** Coerce a stored value to a layout; anything unknown (corrupt, a rolled-back future layout, or the
 * retired "rows") falls back to the default rather than rendering nothing. */
export function parseChannelLayout(raw: unknown): ChannelLayout {
  return (CHANNEL_LAYOUTS as readonly string[]).includes(raw as string)
    ? (raw as ChannelLayout)
    : CHANNEL_LAYOUT_DEFAULT;
}

/** Cards-per-page choices for the card layout's pager (0 = "All"), shared by both manager tabs. */
export const CARD_PAGE_SIZES = [10, 25, 50, 100];
const CARD_SIZE_DEFAULT = 25;

/** Coerce a stored cards-per-page value to one the pager actually OFFERS (the sizes above, or 0 =
 * "All"). Clamped against the allowed set — like `clampView`/`clampStatus` — not merely type-checked:
 * a corrupt entry would make the page count NaN and slice the grid down to nothing, and an
 * off-menu number (a hand-edited 7, or an option a future build dropped) would page by a value the
 * `<select>` cannot show, so the control and the behaviour would silently disagree. */
export function parseCardSize(raw: unknown): number {
  return typeof raw === "number" && (raw === 0 || CARD_PAGE_SIZES.includes(raw))
    ? raw
    : CARD_SIZE_DEFAULT;
}