/* ============================================================================
   PAGE KIT - section primitives
   ----------------------------------------------------------------------------
   The handful of layout pieces every page module repeats: the centred content
   column, a vertical rhythm for sections, a section header, the page hero and
   the empty state that renders while the CMS has no entry yet.

   RULES THIS FILE FOLLOWS
   -----------------------
   * tier-2 semantic tokens only - no hex, no tier-1 primitive, no raw type
     size (the type role utilities carry family/size/leading/tracking/weight)
   * logical properties only (ps-/pe-/ms-/me-/start-/end-, text-start) so the
     Arabic pages mirror without a single `rtl:` override
   * no component here duplicates Button / Input / Card - those are imported
     from ~/components/ui by the pages themselves
   ========================================================================= */

import type { ReactNode } from "react";

import "./hero.css";
import "./motion.css";

export function cx(...parts: Array<string | false | null | undefined>): string {
  return parts.filter(Boolean).join(" ");
}

/* ---------------------------------------------------------------------------
   LAYOUT
   ------------------------------------------------------------------------ */

export interface ContainerProps {
  children: ReactNode;
  className?: string;
}

/** The centred content column every section shares. */
export function Container({ children, className }: ContainerProps) {
  return (
    <div
      className={cx(
        "mx-auto w-full max-w-[var(--layout-content-max)] px-[var(--layout-gutter)] lg:px-[var(--layout-gutter-lg)]",
        className,
      )}
    >
      {children}
    </div>
  );
}

export interface PageSectionProps {
  children: ReactNode;
  id?: string;
  /** Flip this section (and only this section) to the other surface. */
  surface?: "dark" | "light";
  className?: string;
  /**
   * Paint this section as one of the drafts' lighter #1D1D1B bands. Cards
   * inside it then draw themselves a step darker, as the drafts do.
   */
  band?: boolean;
  /** Content is placed directly in the section, without the centred column. */
  bleed?: boolean;
  "aria-labelledby"?: string;
  /** For a band whose heading is not on the page - a figures row, a logo wall. */
  "aria-label"?: string;
}

/**
 * One band of the page. `surface` re-points the whole tier-2 palette for the
 * subtree, so a light band needs no colour classes of its own.
 */
export function PageSection({
  children,
  id,
  surface,
  band = false,
  className,
  bleed = false,
  ...rest
}: PageSectionProps) {
  return (
    <section
      id={id}
      {...(surface ? { "data-surface": surface } : {})}
      className={cx("py-3xl md:py-4xl", band && "sh-band", className)}
      {...rest}
    >
      {bleed ? children : <Container>{children}</Container>}
    </section>
  );
}

/** A readable measure for long-form prose. */
export function Prose({ children, className }: ContainerProps) {
  return (
    <div className={cx("flex max-w-[var(--layout-prose-max)] flex-col gap-md", className)}>
      {children}
    </div>
  );
}

/* ---------------------------------------------------------------------------
   HEADINGS
   ------------------------------------------------------------------------ */

export interface SectionHeaderProps {
  title: string;
  id?: string;
  eyebrow?: string;
  lead?: string;
  titleAs?: "h1" | "h2" | "h3";
  /**
   * Type role of the title. "h2" is the Heading/H2 role every inner page uses;
   * "display" is Display/Small - the home page draws its band headings at the
   * same 44/52 as the hero (figma 361:11147, 393:14570) while keeping them
   * <h2> in the outline, which `titleAs` alone cannot express.
   */
  size?: "h2" | "display";
  /** Figma centres the home page's section headers; inner pages read start. */
  align?: "start" | "center";
  className?: string;
}

export function SectionHeader({
  title,
  id,
  eyebrow,
  lead,
  titleAs = "h2",
  size = "h2",
  align = "start",
  className,
}: SectionHeaderProps) {
  const Title = titleAs;
  const centred = align === "center";
  const display = size === "display" || titleAs === "h1";

  return (
    <header
      className={cx(
        "flex flex-col gap-sm",
        centred ? "items-center text-center" : "items-start text-start",
        className,
      )}
    >
      {eyebrow ? (
        <p className="label-md uppercase text-[var(--text-accent)]">{eyebrow}</p>
      ) : null}

      <Title
        id={id}
        className={cx(
          "text-[var(--text-primary)]",
          display ? "heading-h1 md:display-sm" : "heading-h2",
        )}
      >
        {title}
      </Title>

      {lead ? (
        <p className="body-lg max-w-[var(--layout-prose-max)] text-[var(--text-secondary)]">
          {lead}
        </p>
      ) : null}
    </header>
  );
}

/* ---------------------------------------------------------------------------
   HERO
   ------------------------------------------------------------------------ */

export interface PageHeroWordmark {
  src: string;
  /**
   * Empty when the headline already names the project - the lockup is then
   * decorative and a screen reader would otherwise read the name twice.
   */
  alt: string;
  /** Intrinsic pixels of the asset, for the aspect ratio the browser reserves. */
  width: number;
  height: number;
  /** Drawn width in CSS pixels. Figma 253:4800 draws the hero lockup at 406. */
  drawnWidth: number;
  /**
   * A second mark drawn flush after this one at the same scale, faded in once
   * the page has rendered, sliding out from behind it - the home hero's
   * "-ER". Always decorative.
   */
  suffix?: PageHeroWordmarkSuffix;
}

export interface PageHeroWordmarkSuffix {
  src: string;
  /** Intrinsic pixels of the asset, for the aspect ratio the browser reserves. */
  width: number;
  height: number;
  /** Drawn width in CSS pixels when the lockup is at full size. */
  drawnWidth: number;
}

/**
 * One soft radial wash drifting behind a hero. Every draft positions its own
 * differently - which edge it hangs from, how far in, how big and how slowly
 * it drifts - so the geometry travels with the page rather than being baked
 * into the hero.
 *
 * `offset` is measured from the INLINE start or end, so the wash mirrors in
 * Arabic along with the rest of the page.
 */
export interface HeroWash {
  /** Offset from the hero's top edge in px; negative pulls it above. */
  top: number;
  /** Which inline edge the wash hangs from. */
  from: "start" | "end";
  /** How far in from that edge - the draft's own value, e.g. "8%" or "-160px". */
  offset: string;
  width: number;
  height: number;
  /** Which brand wash. The drafts use green everywhere and red once, on home. */
  tone?: "accent" | "danger";
  /** Seconds one drift cycle takes; the drafts vary this from 18s to 24s. */
  durationSeconds?: number;
  /** Drift the other way round, as the home hero's red wash does. */
  reverse?: boolean;
}

export interface PageHeroMedia {
  src: string;
  alt: string;
  width?: number;
  height?: number;
}

/**
 * How the picture is drawn.
 *   "rounded" - a 16:9 card with the surface radius. The default, and what the
 *               inner pages have always rendered.
 *   "banner"  - the home treatment (figma 253:4800): square corners, a wide
 *               band, and the two flat washes the frame paints over the photo.
 */
export type PageHeroMediaTreatment = "rounded" | "banner";

export interface PageHeroProps {
  title: string;
  eyebrow?: string;
  lead?: string;
  /**
   * Brand lockup drawn above the headline. Only the home hero carries one
   * (figma 253:4800, a 406x86 wordmark 48px above the headline row).
   */
  wordmark?: PageHeroWordmark;
  /**
   * Funding attribution, drawn 24px directly above the wordmark (figma
   * 478:15951). Only the home hero carries one; every other page relies on the
   * footer for EU visibility.
   */
  funderBadge?: ReactNode;
  /**
   * A short status line drawn as a pill above the headline - the redesign's
   * "Now live" chip. Only rendered when the caller passes one, so it can never
   * announce a state the CMS has not authored.
   */
  statusPill?: ReactNode;
  /** Buttons, rendered inline-end of the headline on wide viewports. */
  actions?: ReactNode;
  /**
   * Put the lead on its own row, opposite the buttons, instead of under the
   * headline. The home draft lays the hero out this way - headline across the
   * top, then the lead and the CTA pair sharing a row, baseline aligned. Every
   * interior hero stacks eyebrow / headline / lead in one column.
   */
  leadWithActions?: boolean;
  /**
   * The washes drifting behind this hero, in the page's own geometry.
   * Decorative and opt-in: omit it and the hero is flat.
   */
  ambient?: readonly HeroWash[];
  /**
   * Tone of the lead. The drafts set it quiet almost everywhere, but What We
   * Do prints it in the primary tone, a step up from the body colour.
   */
  leadTone?: "secondary" | "primary";
  /**
   * Stagger the hero's own content in on first paint. Opt-in for the same
   * reason: only the home hero is designed as an arrival moment.
   */
  reveal?: boolean;
  /** Wide picture below the headline row, as in Figma 253:4800. */
  media?: PageHeroMedia;
  /**
   * Content closing the hero band, under the picture and its brand stripe -
   * the redesign puts the figures row here so it sits on the hero's own
   * surface rather than opening a band of its own.
   */
  below?: ReactNode;
  mediaTreatment?: PageHeroMediaTreatment;
  className?: string;
}

/**
 * The lockup above the hero headline. Its size is a graphic dimension, not a
 * spacing value - set the way Brand.tsx and the footer size their lockups, with
 * the intrinsic box on each <img> so the browser reserves the right height.
 *
 * With a `suffix`, the two marks share one row. The row is pinned to
 * `dir="ltr"` because a Latin wordmark never mirrors (its position on the page
 * still follows the page's direction), and each mark takes the share of the
 * row its drawn width gives it, so the pair shrinks together on a narrow screen
 * and stays at one scale at every width.
 */
function HeroWordmark({ wordmark }: { wordmark: PageHeroWordmark }) {
  const { suffix } = wordmark;

  if (!suffix) {
    return (
      <img
        src={wordmark.src}
        alt={wordmark.alt}
        width={wordmark.width}
        height={wordmark.height}
        loading="eager"
        decoding="async"
        draggable={false}
        style={{ maxWidth: `${wordmark.drawnWidth}px` }}
        className="block h-auto w-full"
      />
    );
  }

  return (
    <div
      dir="ltr"
      style={{ maxWidth: `${wordmark.drawnWidth + suffix.drawnWidth}px` }}
      className="flex w-full items-start"
    >
      <img
        src={wordmark.src}
        alt={wordmark.alt}
        width={wordmark.width}
        height={wordmark.height}
        loading="eager"
        decoding="async"
        draggable={false}
        style={{ flex: `${wordmark.drawnWidth} 1 0%` }}
        className="block h-auto min-w-0"
      />
      {/* The clipping box starts at the P's right edge, so the mark inside it
          can slide out from behind the P (hero.css). */}
      <span
        style={{ flex: `${suffix.drawnWidth} 1 0%` }}
        className="sh-hero-suffix block min-w-0"
      >
        <img
          src={suffix.src}
          alt=""
          width={suffix.width}
          height={suffix.height}
          loading="eager"
          decoding="async"
          draggable={false}
          className="sh-hero-suffix__mark block h-auto w-full"
        />
      </span>
    </div>
  );
}

/**
 * The page hero - Figma "Hero header" (253:4800): headline on the inline-start
 * side, the call-to-action group on the inline-end side, and a full-width
 * picture underneath. The picture is only rendered when the CMS supplies one;
 * an empty media box would otherwise ship as a grey rectangle.
 */
export function PageHero({
  title,
  eyebrow,
  lead,
  wordmark,
  funderBadge,
  statusPill,
  actions,
  leadWithActions = false,
  ambient,
  leadTone = "secondary",
  reveal = false,
  media,
  mediaTreatment = "rounded",
  below,
  className,
}: PageHeroProps) {
  /** Only paid for when the caller asks for the arrival treatment. */
  const rise = (step?: 2 | 3 | 4 | 5) =>
    reveal ? cx("sh-rise", step && `sh-rise--${step}`) : undefined;

  const washes = ambient ?? [];

  return (
    <section
      className={cx(
        "pt-[var(--layout-hero-top)] pb-[var(--layout-hero-bottom)]",
        washes.length > 0 && "relative isolate overflow-hidden",
        className,
      )}
    >
      {washes.length > 0 ? (
        /* Flat washes of the brand colours, drifting. Purely decorative:
           behind the content, never catching the pointer, and hidden from
           assistive technology. The geometry is the page's own; only the
           drift itself is shared (motion.css). */
        <div aria-hidden="true" className="pointer-events-none absolute inset-0 -z-10">
          {washes.map((wash, index) => (
            <span
              key={`${wash.from}-${wash.offset}-${index}`}
              className={cx(
                "sh-glow absolute rounded-pill",
                wash.tone === "danger"
                  ? "bg-[radial-gradient(closest-side,var(--surface-danger-subtle),transparent)]"
                  : "bg-[radial-gradient(closest-side,var(--surface-accent-subtle),transparent)]",
              )}
              style={{
                top: `${wash.top}px`,
                width: `${wash.width}px`,
                height: `${wash.height}px`,
                ...(wash.from === "end"
                  ? { insetInlineEnd: wash.offset }
                  : { insetInlineStart: wash.offset }),
                ...(wash.durationSeconds
                  ? { animationDuration: `${wash.durationSeconds}s` }
                  : {}),
                ...(wash.reverse ? { animationDirection: "reverse" } : {}),
              }}
            />
          ))}
        </div>
      ) : null}

      <Container className="flex flex-col gap-2xl">
        {funderBadge || wordmark ? (
          /* Figma groups the two (478:16183): the badge, then 24px, then the
             lockup. The group as a whole keeps the 48px the Container's gap
             already provides above the headline row. */
          <div className={cx("flex flex-col gap-lg", rise())}>
            {funderBadge}

            {wordmark ? <HeroWordmark wordmark={wordmark} /> : null}
          </div>
        ) : null}

        {statusPill ? <div className={rise(2)}>{statusPill}</div> : null}

        {leadWithActions ? (
          <>
            {/* Headline across the top ... */}
            <div className={cx("flex max-w-[43.75rem] flex-col gap-sm", rise(3))}>
              {eyebrow ? (
                <p className="label-md uppercase text-[var(--text-accent)]">{eyebrow}</p>
              ) : null}

              <h1 className="heading-h1 text-[var(--text-primary)] md:display-sm">
                {title}
              </h1>
            </div>

            {/* ... then the lead and the buttons sharing a row, sitting on the
                same baseline, as the home draft draws them. */}
            {lead || actions ? (
              <div
                className={cx(
                  "flex flex-col gap-xl lg:flex-row lg:items-end lg:justify-between",
                  rise(4),
                )}
              >
                {lead ? (
                  <p
                    className={cx(
                      "body-lg max-w-[40rem]",
                      leadTone === "primary"
                        ? "text-[var(--text-primary)]"
                        : "text-[var(--text-secondary)]",
                    )}
                  >
                    {lead}
                  </p>
                ) : null}

                {actions ? (
                  <div className="flex flex-wrap items-center gap-lg lg:justify-end">
                    {actions}
                  </div>
                ) : null}
              </div>
            ) : null}
          </>
        ) : (
          <div className="flex flex-col gap-lg lg:flex-row lg:items-end lg:justify-between">
            <div className={cx("flex max-w-[46rem] flex-col gap-sm", rise(3))}>
              {eyebrow ? (
                <p className="label-md uppercase text-[var(--text-accent)]">{eyebrow}</p>
              ) : null}

              <h1 className="heading-h1 text-[var(--text-primary)] md:display-sm">
                {title}
              </h1>

              {lead ? (
                <p
                  className={cx(
                    "body-lg max-w-[var(--layout-prose-max)]",
                    leadTone === "primary"
                      ? "text-[var(--text-primary)]"
                      : "text-[var(--text-secondary)]",
                  )}
                >
                  {lead}
                </p>
              ) : null}
            </div>

            {actions ? (
              <div
                className={cx(
                  "flex flex-wrap items-center gap-lg lg:justify-end",
                  rise(4),
                )}
              >
                {actions}
              </div>
            ) : null}
          </div>
        )}

        {media ? (
          mediaTreatment === "banner" ? (
            /* Figma draws a 1244x700 picture inside an 800px frame that clips
               it, so what the page actually shows is a wide band. The band is
               kept at 16:9 on a phone, where a 2.9:1 strip would be a sliver.
               The two washes are flat fills in the frame, not gradients: a
               mint tint over a shade, both painted on the photograph. */
            <div className={cx("w-full", rise(5))}>
              <div className="relative w-full overflow-hidden">
                <img
                  src={media.src}
                  alt={media.alt}
                  {...(media.width ? { width: media.width } : {})}
                  {...(media.height ? { height: media.height } : {})}
                  fetchPriority="high"
                  className="aspect-[16/9] w-full object-cover md:aspect-[1244/415]"
                />
                <span
                  aria-hidden="true"
                  className="pointer-events-none absolute inset-0 bg-[var(--overlay-picture-shade)]"
                />
                <span
                  aria-hidden="true"
                  className="pointer-events-none absolute inset-0 bg-[var(--overlay-picture-tint)]"
                />
                {/* A highlight travelling across the picture - the draft's
                    `sheen`. Decorative, and it rides on top of both washes. */}
                <span
                  aria-hidden="true"
                  className="sh-sheen pointer-events-none absolute inset-0 bg-[linear-gradient(100deg,transparent_35%,var(--overlay-veil)_50%,transparent_65%)]"
                />
              </div>

              {/* The colour band (478:16360): three blocks flush under the
                  picture, 6px tall. Figma lays out 390 / 495 / 363 inside a
                  1244-wide clipping frame, so the last block loses 4px and the
                  split that is actually drawn is 390 : 495 : 359 - carried here
                  as flex-grow ratios so it holds at every width instead of only
                  at 1244. The three fills are `background/accent`,
                  `background/inverse` and `background/danger`, which is why the
                  middle block reads white on the dark hero and near-black on a
                  light surface.

                  Purely decorative, so it is hidden from assistive technology;
                  as an ordinary flex row it mirrors in Arabic along with the
                  rest of the page. */}
              <div aria-hidden="true" className="sh-bar-grow flex h-[6px] w-full">
                <span className="basis-0 grow-[390] bg-[var(--surface-accent)]" />
                {/* The middle block is the raised dark, not the inverse:
                    the redesign drops pure white from the page entirely, so
                    the stripe reads green / dark / red on the near-black
                    band instead of green / white / red. */}
                <span className="basis-0 grow-[495] bg-[var(--surface-raised)]" />
                <span className="basis-0 grow-[359] bg-[var(--surface-danger)]" />
              </div>
            </div>
          ) : (
            <img
              src={media.src}
              alt={media.alt}
              {...(media.width ? { width: media.width } : {})}
              {...(media.height ? { height: media.height } : {})}
              fetchPriority="high"
              className="aspect-[16/9] w-full max-w-full rounded-surface object-cover"
            />
          )
        ) : null}

        {below}
      </Container>
    </section>
  );
}

/* ---------------------------------------------------------------------------
   PANELS
   ------------------------------------------------------------------------ */

export interface InfoPanelProps {
  title: string;
  children?: ReactNode;
  /** Small line above the title - a number, a partner name, a role. */
  eyebrow?: string;
  /**
   * How the eyebrow is drawn. "chip" is the redesign's filled role tag on the
   * subtle accent surface; "plain" is the bare accent label inner pages use.
   */
  eyebrowVariant?: "plain" | "chip";
  titleAs?: "h2" | "h3" | "h4";
  className?: string;
}

/**
 * A titled block of text with no destination - a pillar, a workstream, a
 * principle. Deliberately NOT a Card: every card in the design system is a
 * link, and these are not.
 */
export function InfoPanel({
  title,
  children,
  eyebrow,
  eyebrowVariant = "plain",
  titleAs = "h3",
  className,
}: InfoPanelProps) {
  const Title = titleAs;

  return (
    <div
      className={cx(
        "flex h-full flex-col gap-xs rounded-card border border-[var(--border-subtle)] bg-[var(--surface-card)] p-lg",
        className,
      )}
    >
      {eyebrow ? (
        <p
          className={cx(
            "label-md uppercase text-[var(--text-accent)]",
            eyebrowVariant === "chip" &&
              "self-start rounded-control bg-[var(--surface-accent-subtle)] px-xs py-2xs",
          )}
        >
          {eyebrow}
        </p>
      ) : null}
      <Title className="heading-h3 text-[var(--text-primary)]">{title}</Title>
      {children ? (
        <div className="body-md text-[var(--text-secondary)]">{children}</div>
      ) : null}
    </div>
  );
}

export interface EmptyStateProps {
  /** Localised - never an English default. */
  message: string;
  title?: string;
  className?: string;
  children?: ReactNode;
}

/**
 * What renders where the CMS has nothing yet. It states plainly that the
 * content is still to come rather than showing an empty grid, and it is always
 * passed a localised string by the caller.
 */
export function EmptyState({ message, title, className, children }: EmptyStateProps) {
  return (
    <div
      className={cx(
        "flex flex-col items-start gap-sm rounded-card border border-dashed border-[var(--border-default)] bg-[var(--surface-sunken)] p-lg text-start",
        className,
      )}
    >
      {title ? (
        <p className="body-md-bold text-[var(--text-primary)]">{title}</p>
      ) : null}
      <p className="body-md text-[var(--text-secondary)]">{message}</p>
      {children}
    </div>
  );
}

/* ---------------------------------------------------------------------------
   SMALL PIECES
   ------------------------------------------------------------------------ */

export interface ValueChipsProps {
  values: readonly string[];
  label?: string;
  /** The redesign centres the row on What We Do; inner pages read start. */
  align?: "start" | "center";
  className?: string;
}

/** The "What guides us" row: Dialogue · Community Leadership · Learning · … */
export function ValueChips({
  values,
  label,
  align = "start",
  className,
}: ValueChipsProps) {
  if (values.length === 0) return null;

  const centred = align === "center";

  return (
    <div
      className={cx(
        "flex flex-col gap-sm",
        centred && "items-center text-center",
        className,
      )}
    >
      {/* Accent, like every other eyebrow in the system (SectionHeader). */}
      {label ? (
        <p className="label-md uppercase text-[var(--text-accent)]">{label}</p>
      ) : null}
      <ul className={cx("flex flex-wrap gap-sm", centred && "justify-center")}>
        {values.map((value) => (
          <li
            key={value}
            /* The drafts rest a chip as a plain outline on the band and only
               fill it under the pointer, where it also takes the 3px lift
               every other control has. */
            className={cx(
              "rounded-pill border border-[var(--border-default)] bg-transparent",
              "px-md py-2xs body-sm-bold text-[var(--text-primary)]",
              "transition duration-[var(--motion-duration-base)]",
              "hover:-translate-y-[3px] hover:border-[var(--border-accent)]",
              "hover:bg-[var(--surface-accent-subtle)]",
            )}
          >
            {value}
          </li>
        ))}
      </ul>
    </div>
  );
}

export interface StatStripProps {
  stats: readonly { value: string; label: string }[];
  className?: string;
}

/**
 * The figures band. `value` is authored in the CMS as a string, already
 * formatted for its locale, because the site must never invent or re-derive a
 * project figure - see the note the pages render when this list is empty.
 */
export function StatStrip({ stats, className }: StatStripProps) {
  if (stats.length === 0) return null;

  return (
    <dl
      className={cx(
        "grid grid-cols-2 gap-lg border-y border-[var(--border-subtle)] py-xl md:grid-cols-4",
        className,
      )}
    >
      {stats.map((stat) => (
        /* Source order is term-then-description, as the spec requires; the
           reversed column paints the figure above its label without repeating
           the label for a screen reader. */
        <div
          key={`${stat.value}-${stat.label}`}
          className="flex flex-col-reverse gap-2xs text-start"
        >
          <dt className="body-sm text-[var(--text-secondary)]">{stat.label}</dt>
          <dd className="heading-h1 text-[var(--text-accent)]">{stat.value}</dd>
        </div>
      ))}
    </dl>
  );
}