import "server-only"

import { cache } from "react"
import { createId } from "@paralleldrive/cuid2"
import { and, asc, desc, eq, inArray, sql, type SQL } from "drizzle-orm"

import { db } from "@/shared/db"
import {
  electiveCourses,
  grades,
  subjects,
  users,
} from "@/shared/db/schema"
import type { DataScope } from "@/shared/types/permissions"

import type {
  ElectiveCourseWithDetails,
  GetElectiveCoursesParams,
} from "./types"
import type {
  CreateElectiveCourseInput,
  UpdateElectiveCourseInput,
} from "./schema"

const toIso = (d: Date | null | undefined): string | null =>
  d ? d.toISOString() : null

const toIsoRequired = (d: Date): string => d.toISOString()

const buildScopeFilter = (scope: DataScope, userId?: string): SQL | null => {
  if (scope.type === "all") return null
  if (scope.type === "owned" && userId) return eq(electiveCourses.teacherId, userId)
  if (scope.type === "class_taught" && userId) {
    return eq(electiveCourses.teacherId, userId)
  }
  if (scope.type === "grade_managed") {
    return scope.gradeIds.length > 0
      ? inArray(electiveCourses.gradeId, scope.gradeIds)
      : sql`1=0`
  }
  if (scope.type === "class_members") return null
  if (scope.type === "children") return null
  return sql`1=0`
}

const mapCourseRow = (
  r: typeof electiveCourses.$inferSelect & {
    teacherName: string | null
    subjectName: string | null
    gradeName: string | null
  }
): ElectiveCourseWithDetails => ({
  id: r.id,
  name: r.name,
  subjectId: r.subjectId,
  teacherId: r.teacherId,
  gradeId: r.gradeId,
  description: r.description,
  capacity: r.capacity,
  enrolledCount: r.enrolledCount,
  classroom: r.classroom,
  schedule: r.schedule,
  startDate: r.startDate ? new Date(r.startDate).toISOString().slice(0, 10) : null,
  endDate: r.endDate ? new Date(r.endDate).toISOString().slice(0, 10) : null,
  selectionStartAt: toIso(r.selectionStartAt),
  selectionEndAt: toIso(r.selectionEndAt),
  status: r.status,
  selectionMode: r.selectionMode,
  credit: String(r.credit),
  createdAt: toIsoRequired(r.createdAt),
  updatedAt: toIsoRequired(r.updatedAt),
  teacherName: r.teacherName,
  subjectName: r.subjectName,
  gradeName: r.gradeName,
})

const buildCourseSelect = () =>
  db
    .select({
      id: electiveCourses.id,
      name: electiveCourses.name,
      subjectId: electiveCourses.subjectId,
      teacherId: electiveCourses.teacherId,
      gradeId: electiveCourses.gradeId,
      description: electiveCourses.description,
      capacity: electiveCourses.capacity,
      enrolledCount: electiveCourses.enrolledCount,
      classroom: electiveCourses.classroom,
      schedule: electiveCourses.schedule,
      startDate: electiveCourses.startDate,
      endDate: electiveCourses.endDate,
      selectionStartAt: electiveCourses.selectionStartAt,
      selectionEndAt: electiveCourses.selectionEndAt,
      status: electiveCourses.status,
      selectionMode: electiveCourses.selectionMode,
      credit: electiveCourses.credit,
      createdAt: electiveCourses.createdAt,
      updatedAt: electiveCourses.updatedAt,
      teacherName: users.name,
      subjectName: subjects.name,
      gradeName: grades.name,
    })
    .from(electiveCourses)
    .leftJoin(users, eq(users.id, electiveCourses.teacherId))
    .leftJoin(subjects, eq(subjects.id, electiveCourses.subjectId))
    .leftJoin(grades, eq(grades.id, electiveCourses.gradeId))

export const getElectiveCourses = cache(
  async (
    params?: GetElectiveCoursesParams & { scope?: DataScope; currentUserId?: string }
  ): Promise<ElectiveCourseWithDetails[]> => {
    try {
      const conditions: SQL[] = []
      if (params?.status)
        conditions.push(
          eq(electiveCourses.status, params.status)
        )
      if (params?.gradeId) conditions.push(eq(electiveCourses.gradeId, params.gradeId))
      if (params?.subjectId)
        conditions.push(eq(electiveCourses.subjectId, params.subjectId))
      if (params?.teacherId)
        conditions.push(eq(electiveCourses.teacherId, params.teacherId))
      if (params?.scope) {
        const scopeFilter = buildScopeFilter(params.scope, params.currentUserId)
        if (scopeFilter) conditions.push(scopeFilter)
      }

      const query = buildCourseSelect()
      const rows = await (conditions.length > 0
        ? query.where(and(...conditions))
        : query
      ).orderBy(desc(electiveCourses.createdAt))

      return rows.map(mapCourseRow)
    } catch (error) {
      console.error("getElectiveCourses failed:", error)
      return []
    }
  }
)

export const getElectiveCourseById = cache(
  async (id: string): Promise<ElectiveCourseWithDetails | null> => {
    try {
      const [row] = await buildCourseSelect()
        .where(eq(electiveCourses.id, id))
        .limit(1)
      if (!row) return null
      return mapCourseRow(row)
    } catch (error) {
      console.error("getElectiveCourseById failed:", error)
      return null
    }
  }
)

export async function createElectiveCourse(
  data: CreateElectiveCourseInput,
  teacherId: string
): Promise<string> {
  const id = createId()
  await db.insert(electiveCourses).values({
    id,
    name: data.name,
    subjectId: data.subjectId,
    teacherId: data.teacherId ?? teacherId,
    gradeId: data.gradeId,
    description: data.description,
    capacity: data.capacity,
    enrolledCount: 0,
    classroom: data.classroom,
    schedule: data.schedule,
    startDate: data.startDate ? new Date(data.startDate) : null,
    endDate: data.endDate ? new Date(data.endDate) : null,
    selectionStartAt: data.selectionStartAt ? new Date(data.selectionStartAt) : null,
    selectionEndAt: data.selectionEndAt ? new Date(data.selectionEndAt) : null,
    status: "draft",
    selectionMode: data.selectionMode,
    credit: data.credit,
  })
  return id
}

export async function updateElectiveCourse(
  id: string,
  data: Partial<UpdateElectiveCourseInput>
): Promise<void> {
  const update: Partial<typeof electiveCourses.$inferSelect> = {}
  if (data.name !== undefined) update.name = data.name
  if (data.subjectId !== undefined) update.subjectId = data.subjectId
  if (data.teacherId !== undefined) update.teacherId = data.teacherId
  if (data.gradeId !== undefined) update.gradeId = data.gradeId
  if (data.description !== undefined) update.description = data.description
  if (data.capacity !== undefined) update.capacity = data.capacity
  if (data.classroom !== undefined) update.classroom = data.classroom
  if (data.schedule !== undefined) update.schedule = data.schedule
  if (data.startDate !== undefined)
    update.startDate = data.startDate ? new Date(data.startDate) : null
  if (data.endDate !== undefined)
    update.endDate = data.endDate ? new Date(data.endDate) : null
  if (data.selectionStartAt !== undefined)
    update.selectionStartAt = data.selectionStartAt ? new Date(data.selectionStartAt) : null
  if (data.selectionEndAt !== undefined)
    update.selectionEndAt = data.selectionEndAt ? new Date(data.selectionEndAt) : null
  if (data.status !== undefined) update.status = data.status
  if (data.selectionMode !== undefined) update.selectionMode = data.selectionMode
  if (data.credit !== undefined) update.credit = data.credit

  if (Object.keys(update).length === 0) return
  await db.update(electiveCourses).set(update).where(eq(electiveCourses.id, id))
}

export async function deleteElectiveCourse(id: string): Promise<void> {
  await db.delete(electiveCourses).where(eq(electiveCourses.id, id))
}

export async function openSelection(courseId: string): Promise<void> {
  await db
    .update(electiveCourses)
    .set({ status: "open", updatedAt: new Date() })
    .where(eq(electiveCourses.id, courseId))
}

export async function closeSelection(courseId: string): Promise<void> {
  await db
    .update(electiveCourses)
    .set({ status: "closed", updatedAt: new Date() })
    .where(eq(electiveCourses.id, courseId))
}

export async function getSubjectOptions(): Promise<{ id: string; name: string }[]> {
  try {
    const rows = await db
      .select({ id: subjects.id, name: subjects.name })
      .from(subjects)
      .orderBy(asc(subjects.order), asc(subjects.name))
    return rows.map((r) => ({ id: r.id, name: r.name }))
  } catch (error) {
    console.error("getSubjectOptions failed:", error)
    return []
  }
}

export type { ElectiveCourseWithDetails }