import { Prisma } from "@prisma/client";
import { db } from "@/lib/db";

/**
 * The still that stands for a project.
 *
 * There is no poster field on Project, and adding one would mean somebody
 * maintaining it. The shots already carry the images, and one of them is
 * already marked as the shot that represents the show — `isKeyShot` — so the
 * poster is chosen rather than uploaded:
 *
 *   1. a key shot with a still, then
 *   2. the most recently touched shot with a still.
 *
 * Within each, `thumbnailUrl` beats `generatedThumbnailUrl`, the same
 * precedence the rest of the app displays shots by (lib/shot-thumbnail.ts):
 * the reference frame from the brief is a deliberate choice, a promoted render
 * frame is whatever the pipeline happened to land on.
 *
 * The choice is deterministic, not random — a card whose image changes between
 * two loads of the same page reads as a glitch, and the eye stops using the
 * image to find the project.
 */
export interface ProjectPoster {
  url: string;
  shotCode: string;
  /** True when this is the show's marked key shot rather than a fallback. */
  isKeyShot: boolean;
}

/**
 * One poster per project in a single query.
 *
 * DISTINCT ON is Postgres-only and deliberate: the alternative is either a
 * query per project or dragging back every shot that has a still just to keep
 * the first of each in memory.
 */
export async function getProjectPosters(
  projectIds: string[]
): Promise<Map<string, ProjectPoster>> {
  if (projectIds.length === 0) return new Map();

  const rows = await db.$queryRaw<
    { projectId: string; url: string; shotCode: string; isKeyShot: boolean }[]
  >(Prisma.sql`
    SELECT DISTINCT ON (s."projectId")
      s."projectId"  AS "projectId",
      COALESCE(NULLIF(s."thumbnailUrl", ''), NULLIF(s."generatedThumbnailUrl", '')) AS "url",
      s."shotCode"   AS "shotCode",
      s."isKeyShot"  AS "isKeyShot"
    FROM "shots" s
    WHERE s."projectId" IN (${Prisma.join(projectIds)})
      AND COALESCE(NULLIF(s."thumbnailUrl", ''), NULLIF(s."generatedThumbnailUrl", '')) IS NOT NULL
    ORDER BY s."projectId", s."isKeyShot" DESC, s."updatedAt" DESC
  `);

  return new Map(
    rows.map((row) => [
      row.projectId,
      { url: row.url, shotCode: row.shotCode, isKeyShot: row.isKeyShot },
    ])
  );
}