import 'server-only';

import { db } from "@/shared/db";
import { questions, questionsToKnowledgePoints } from "@/shared/db/schema";
import { and, count, desc, eq, inArray, sql, type SQL } from "drizzle-orm";
import { cache } from "react";
import type { Question, QuestionType } from "./types";

export type GetQuestionsParams = {
  q?: string;
  page?: number;
  pageSize?: number;
  ids?: string[];
  knowledgePointId?: string;
  type?: QuestionType;
  difficulty?: number;
};

export const getQuestions = cache(async ({
  q,
  page = 1,
  pageSize = 50,
  ids,
  knowledgePointId,
  type,
  difficulty,
}: GetQuestionsParams = {}) => {
  const offset = (page - 1) * pageSize;

  const conditions: SQL[] = [];

  if (ids && ids.length > 0) {
    conditions.push(inArray(questions.id, ids));
  }

  if (q && q.trim().length > 0) {
    const needle = `%${q.trim().toLowerCase()}%`;
    conditions.push(
      sql`LOWER(CAST(${questions.content} AS CHAR)) LIKE ${needle}`
    );
  }

  if (type) {
    conditions.push(eq(questions.type, type));
  }

  if (difficulty) {
    conditions.push(eq(questions.difficulty, difficulty));
  }

  if (knowledgePointId) {
    const subQuery = db
      .select({ questionId: questionsToKnowledgePoints.questionId })
      .from(questionsToKnowledgePoints)
      .where(eq(questionsToKnowledgePoints.knowledgePointId, knowledgePointId));
    
    conditions.push(inArray(questions.id, subQuery));
  }

  if (!ids || ids.length === 0) {
    conditions.push(sql`${questions.parentId} IS NULL`)
  }

  const whereClause = conditions.length > 0 ? and(...conditions) : undefined;

  const [totalResult] = await db
    .select({ count: count() })
    .from(questions)
    .where(whereClause);
  
  const total = Number(totalResult?.count ?? 0);

  const rows = await db.query.questions.findMany({
    where: whereClause,
    limit: pageSize,
    offset: offset,
    orderBy: [desc(questions.createdAt)],
    with: {
      questionsToKnowledgePoints: {
        with: {
          knowledgePoint: true,
        },
      },
      author: {
        columns: {
          id: true,
          name: true,
          image: true,
        },
      },
      children: true, 
    },
  });

  return {
    data: rows.map((row) => {
      const knowledgePoints =
        row.questionsToKnowledgePoints?.map((rel) => rel.knowledgePoint) ?? [];

      const author = row.author
        ? {
            id: row.author.id,
            name: row.author.name,
            image: row.author.image,
          }
        : null;

      const mapped: Question = {
        id: row.id,
        content: row.content,
        type: row.type,
        difficulty: row.difficulty ?? 1,
        createdAt: row.createdAt,
        updatedAt: row.updatedAt,
        author,
        knowledgePoints: knowledgePoints.map((kp) => ({ id: kp.id, name: kp.name })),
        childrenCount: row.children?.length ?? 0,
      };

      return mapped;
    }),
    meta: {
      page,
      pageSize,
      total,
      totalPages: Math.ceil(total / pageSize),
    },
  };
});