import fs from "fs";
import path from "path";

export type SliderPhoto = { src: string; alt: string };

function slugToAlt(filename: string): string {
  const base = filename.replace(/\.[^.]+$/, "");
  const words = base.replace(/[-_]+/g, " ").trim();
  return words || "Slide";
}

export function parseManifest(data: unknown): SliderPhoto[] {
  if (!Array.isArray(data)) return [];
  const out: SliderPhoto[] = [];
  for (const item of data) {
    if (typeof item !== "object" || item === null || !("src" in item)) continue;
    const src = (item as { src: unknown }).src;
    if (typeof src !== "string" || !src.startsWith("/")) continue;
    const altRaw = (item as { alt?: unknown }).alt;
    const alt = typeof altRaw === "string" && altRaw.trim() ? altRaw.trim() : slugToAlt(src.split("/").pop() ?? "");
    out.push({ src, alt });
  }
  return out;
}

const IMAGE_EXT = /\.(jpe?g|png|webp|gif|avif)$/i;

function scanSliderDirectory(dir: string): SliderPhoto[] {
  let names: string[] = [];
  try {
    names = fs.readdirSync(dir);
  } catch {
    return [];
  }
  return names
    .filter((f) => IMAGE_EXT.test(f))
    .sort((a, b) => a.localeCompare(b, undefined, { sensitivity: "base" }))
    .map((f) => ({
      src: `/slider/${f}`,
      alt: slugToAlt(f),
    }));
}

/**
 * Reads `public/slider/manifest.json` when present (full control: order + alt).
 * Otherwise scans `public/slider` for image files (drop-in updates, no code edits).
 */
export function readSliderPhotos(): SliderPhoto[] {
  const dir = path.join(process.cwd(), "public", "slider");
  if (!fs.existsSync(dir)) return [];

  const manifestPath = path.join(dir, "manifest.json");
  if (fs.existsSync(manifestPath)) {
    try {
      const raw = JSON.parse(fs.readFileSync(manifestPath, "utf8")) as unknown;
      return parseManifest(raw);
    } catch {
      return [];
    }
  }

  return scanSliderDirectory(dir);
}