"use client";

/**
 * Helpers shared by PostGridCard and PostScrollCard.
 *
 *   • postSourceHref       — synthesizes `?hl=` if the stored URL lacks one
 *   • themeGradientStyle   — picks one of four palette-aware gradients
 *                            deterministically from a seed (post id) so a
 *                            feed of image-less posts looks varied without
 *                            shifting between renders.
 */

import type { Post } from "@/lib/social";
import { appendHighlight, hasHighlight } from "@/lib/text-highlight";

export function postSourceHref(post: Post): string {
  return hasHighlight(post.source_url) || !post.caption
    ? post.source_url
    : appendHighlight(post.source_url, post.caption);
}

// Quote-card gradients.
//
// Four CSS custom properties (`--quote-gradient-1` … 4) are defined per
// palette in `app/globals.css`. Each palette ships its own hand-tuned
// gradient set so the cards swap colour with the active theme:
//
//   • Aged Parchment      → mahogany binding + temple gold
//   • Tulasī Garden       → peacock depths + temple gold
//   • Yamunā Mist         → river dusk navy + sandbank
//   • Ancient Manuscript  → midnight leather + saffron
//   • Nīlamaṇi            → peacock night over still water
//   • Vraja Twilight      → deep wine + rose dusk
//
// All variants are dark-leaning so `text-white` reads cleanly. The card
// picks one of the four deterministically from `post.id`.
const GRADIENT_VARS = [
  "var(--quote-gradient-1)",
  "var(--quote-gradient-2)",
  "var(--quote-gradient-3)",
  "var(--quote-gradient-4)",
];

/** Returns an inline-style object that applies the chosen gradient. The
 *  style approach (vs a className) lets us reference CSS custom properties
 *  that vary per palette — Tailwind can't generate utility classes for
 *  values that change at runtime via `:root` selectors. */
export function themeGradientStyle(seed: string): React.CSSProperties {
  // Cheap, stable hash — same seed always picks the same gradient.
  let h = 0;
  for (let i = 0; i < seed.length; i++) h = (h * 31 + seed.charCodeAt(i)) >>> 0;
  return { backgroundImage: GRADIENT_VARS[h % GRADIENT_VARS.length] };
}

/** Flat background for post cards without an image: pure white on every
 *  light palette, palette-specific darker contrast on dark palettes.
 *  Defined as `--quote-card-bg` per `:root` / `.dark` block in
 *  globals.css. Combine with `text-foreground` for legibility — both
 *  sides of the theme switch reverse together. */
export function quoteCardBgStyle(): React.CSSProperties {
  return { backgroundColor: "var(--quote-card-bg)" };
}

// ───────────────────────────────────────────────────────────────────────────
// Variable quote sizing
// ───────────────────────────────────────────────────────────────────────────
//
// A pithy two-word quote and a full paragraph need very different
// treatments inside a fixed-size card. We pick a tier from the caption's
// character count:
//
//   tier 1 (very short) — biggest font, dead-centre, no truncation needed
//   tier 2 (short)      — large font, centred, ~5-line clamp
//   tier 3 (medium)     — medium font, centred, ~6/7-line clamp
//   tier 4 (long)       — smallest font, anchored bottom-LEFT and left-
//                         aligned (a centred wall of small text would
//                         cover the entire card and look claustrophobic;
//                         bottom-left mimics the image variant's caption
//                         placement and breathes better).
//
// Two scales: "grid" for the small square card, "scroll" for the larger
// Instagram-style card.

export type QuoteSize = {
  /** Tailwind font-size classes, e.g. "text-xl sm:text-2xl" */
  fontClass: string;
  /** Tailwind line-clamp class limiting overflow */
  clampClass: string;
  /** Where to anchor the text block inside its container */
  alignment: "center" | "bottom-left";
};

export function quoteSize(text: string, variant: "grid" | "scroll"): QuoteSize {
  const len = (text ?? "").trim().length;
  if (variant === "grid") {
    if (len <= 50)
      return {
        fontClass: "text-xl sm:text-2xl",
        clampClass: "line-clamp-3",
        alignment: "center",
      };
    if (len <= 150)
      return {
        fontClass: "text-base sm:text-lg",
        clampClass: "line-clamp-5",
        alignment: "center",
      };
    if (len <= 300)
      return {
        fontClass: "text-sm sm:text-base",
        clampClass: "line-clamp-[7]",
        alignment: "center",
      };
    return {
      fontClass: "text-xs sm:text-sm",
      clampClass: "line-clamp-[9]",
      alignment: "bottom-left",
    };
  }
  // scroll — bigger card, larger fonts at every tier, higher thresholds
  // so paragraph-length quotes still get centred at a comfortable size.
  if (len <= 60)
    return {
      fontClass: "text-3xl sm:text-4xl",
      clampClass: "line-clamp-3",
      alignment: "center",
    };
  if (len <= 180)
    return {
      fontClass: "text-2xl sm:text-3xl",
      clampClass: "line-clamp-5",
      alignment: "center",
    };
  if (len <= 380)
    return {
      fontClass: "text-lg sm:text-xl",
      clampClass: "line-clamp-[8]",
      alignment: "center",
    };
  return {
    fontClass: "text-base sm:text-lg",
    clampClass: "line-clamp-[10]",
    alignment: "bottom-left",
  };
}