import { NextRequest, NextResponse } from "next/server";
import { db, recipes, users, favorites, ratings, userFollows, eq, and, or, ne, gte, notInArray, inArray, desc, isNotNull } from "@epicure/db";
import { requireSessionOrApiKey } from "@/lib/api-auth";
import { buildPreferenceMap, rankForYou } from "@/lib/for-you-ranking";
import { attachCardExtras } from "@/lib/recipe-card-extras";

export async function GET(req: NextRequest) {
  const { session, response } = await requireSessionOrApiKey(req);
  if (response) return response;
  const userId = session!.user.id;

  const { searchParams } = new URL(req.url);
  const limit = Math.min(parseInt(searchParams.get("limit") ?? "20"), 50);
  const offsetRaw = parseInt(searchParams.get("offset") ?? "0");
  const offset = Number.isNaN(offsetRaw) ? 0 : Math.max(0, offsetRaw);

  // Recipes the user has favorited, or rated 4+, define their taste profile.
  const [favoritedRows, highRatedRows] = await Promise.all([
    db.select({ recipeId: favorites.recipeId }).from(favorites).where(eq(favorites.userId, userId)),
    db.select({ recipeId: ratings.recipeId }).from(ratings).where(and(eq(ratings.userId, userId), gte(ratings.score, 4))),
  ]);

  const likedIds = [...new Set([...favoritedRows.map((r) => r.recipeId), ...highRatedRows.map((r) => r.recipeId)])];

  const likedRecipes = likedIds.length > 0
    ? await db.select({ tags: recipes.tags, dietaryTags: recipes.dietaryTags }).from(recipes).where(inArray(recipes.id, likedIds))
    : [];

  const preferences = buildPreferenceMap(likedRecipes);

  const excludeIds = likedIds.length > 0 ? likedIds : ["__none__"];

  const candidates = await db
    .select({
      id: recipes.id,
      title: recipes.title,
      description: recipes.description,
      baseServings: recipes.baseServings,
      prepMins: recipes.prepMins,
      cookMins: recipes.cookMins,
      difficulty: recipes.difficulty,
      visibility: recipes.visibility,
      aiGenerated: recipes.aiGenerated,
      createdAt: recipes.createdAt,
      authorId: recipes.authorId,
      authorName: users.name,
      authorUsername: users.username,
      authorAvatarUrl: users.avatarUrl,
      tags: recipes.tags,
      dietaryTags: recipes.dietaryTags,
      isBatchCook: recipes.isBatchCook,
      sourceUrl: recipes.sourceUrl,
      recipeType: recipes.recipeType,
      coverIcon: recipes.coverIcon,
      coverColor: recipes.coverColor,
    })
    .from(recipes)
    .innerJoin(users, eq(recipes.authorId, users.id))
    .leftJoin(
      userFollows,
      and(eq(userFollows.followingId, recipes.authorId), eq(userFollows.followerId, userId))
    )
    .where(and(
      eq(recipes.visibility, "public"),
      ne(recipes.authorId, userId),
      notInArray(recipes.id, excludeIds),
      // Private authors are excluded from discovery unless the viewer already follows them.
      or(eq(users.isPrivate, false), isNotNull(userFollows.followerId))
    ))
    .orderBy(desc(recipes.createdAt))
    .limit(200); // score a bounded recent window rather than the whole table

  const ranked = preferences.size > 0
    ? rankForYou(candidates, preferences)
    : [...candidates].sort((a, b) => b.createdAt.getTime() - a.createdAt.getTime());

  const page = ranked.slice(offset, offset + limit).map(({ dietaryTags: _dietaryTags, ...r }) => ({
    ...r,
    createdAt: r.createdAt.toISOString(),
  }));
  const data = await attachCardExtras(page, userId);

  // `ranked` is capped to a bounded recent window (see `candidates` query above), so this
  // total reflects the size of that ranked window rather than every eligible recipe.
  return NextResponse.json({ data, total: ranked.length, limit, offset });
}