import { db } from "@/shared/db"
import { exams } from "@/shared/db/schema"
import { eq, desc, like, and, or } from "drizzle-orm"
import { cache } from "react"

import type { Exam, ExamDifficulty, ExamStatus } from "./types"

export type GetExamsParams = {
  q?: string
  status?: string
  difficulty?: string
  page?: number
  pageSize?: number
}

const isRecord = (v: unknown): v is Record<string, unknown> => typeof v === "object" && v !== null

const parseExamMeta = (description: string | null): Record<string, unknown> => {
  if (!description) return {}
  try {
    const parsed: unknown = JSON.parse(description)
    return isRecord(parsed) ? parsed : {}
  } catch {
    return {}
  }
}

const getString = (obj: Record<string, unknown>, key: string): string | undefined => {
  const v = obj[key]
  return typeof v === "string" ? v : undefined
}

const getNumber = (obj: Record<string, unknown>, key: string): number | undefined => {
  const v = obj[key]
  return typeof v === "number" ? v : undefined
}

const getStringArray = (obj: Record<string, unknown>, key: string): string[] | undefined => {
  const v = obj[key]
  if (!Array.isArray(v)) return undefined
  const items = v.filter((x): x is string => typeof x === "string")
  return items.length === v.length ? items : undefined
}

const toExamDifficulty = (n: number | undefined): ExamDifficulty => {
  if (n === 1 || n === 2 || n === 3 || n === 4 || n === 5) return n
  return 1
}


export const getExams = cache(async (params: GetExamsParams) => {
  const conditions = []

  if (params.q) {
    const search = `%${params.q}%`
    conditions.push(or(like(exams.title, search), like(exams.description, search)))
  }

  if (params.status && params.status !== "all") {
    conditions.push(eq(exams.status, params.status))
  }

  // Note: Difficulty is stored in JSON description field in current schema, 
  // so we might need to filter in memory or adjust schema. 
  // For now, let's fetch and filter in memory if difficulty is needed, 
  // or just ignore strict DB filtering for JSON fields to keep it simple.

  const data = await db.query.exams.findMany({
    where: conditions.length ? and(...conditions) : undefined,
    orderBy: [desc(exams.createdAt)],
    with: {
      subject: true,
      gradeEntity: true,
    }
  })

  // Transform and Filter (especially for JSON fields)
  let result: Exam[] = data.map((exam) => {
    const meta = parseExamMeta(exam.description || null)

    return {
      id: exam.id,
      title: exam.title,
      status: (exam.status as ExamStatus) || "draft",
      subject: exam.subject?.name ?? getString(meta, "subject") ?? "General",
      grade: exam.gradeEntity?.name ?? getString(meta, "grade") ?? "General",
      difficulty: toExamDifficulty(getNumber(meta, "difficulty")),
      totalScore: getNumber(meta, "totalScore") || 100,
      durationMin: getNumber(meta, "durationMin") || 60,
      questionCount: getNumber(meta, "questionCount") || 0,
      scheduledAt: exam.startTime?.toISOString(),
      createdAt: exam.createdAt.toISOString(),
      updatedAt: exam.updatedAt?.toISOString(),
      tags: getStringArray(meta, "tags") || [],
    }
  })

  if (params.difficulty && params.difficulty !== "all") {
    const d = parseInt(params.difficulty)
    result = result.filter((e) => e.difficulty === d)
  }

  return result
})

export const getExamById = cache(async (id: string) => {
  const exam = await db.query.exams.findFirst({
    where: eq(exams.id, id),
    with: {
      subject: true,
      gradeEntity: true,
      questions: {
        orderBy: (examQuestions, { asc }) => [asc(examQuestions.order)],
        with: {
            question: true
        }
      }
    }
  })

  if (!exam) return null

  const meta = parseExamMeta(exam.description || null)

  return {
    id: exam.id,
    title: exam.title,
    status: (exam.status as ExamStatus) || "draft",
    subject: exam.subject?.name ?? getString(meta, "subject") ?? "General",
    grade: exam.gradeEntity?.name ?? getString(meta, "grade") ?? "General",
    difficulty: toExamDifficulty(getNumber(meta, "difficulty")),
    totalScore: getNumber(meta, "totalScore") || 100,
    durationMin: getNumber(meta, "durationMin") || 60,
    scheduledAt: exam.startTime?.toISOString(),
    createdAt: exam.createdAt.toISOString(),
    updatedAt: exam.updatedAt?.toISOString(),
    tags: getStringArray(meta, "tags") || [],
    structure: exam.structure as unknown,
    questions: exam.questions.map((eqRel) => ({
      id: eqRel.questionId,
      score: eqRel.score ?? 0,
      order: eqRel.order ?? 0,
    })),
  }
})

export const omitScheduledAtFromDescription = (description: string | null): string => {
  if (!description) return "{}"
  try {
    const meta = JSON.parse(description)
    if (typeof meta === "object" && meta !== null) {
      const rest = { ...(meta as Record<string, unknown>) }
      delete rest.scheduledAt
      return JSON.stringify(rest)
    }
    return description
  } catch {
    return description || "{}"
  }
}