import { defineStore } from 'pinia'
import { ref } from 'vue'

export interface CourseRecord {
  code: string
  name: string
  credits: number
  score: number
}

export interface SemesterRecord {
  id: number
  studentId: number
  semesterName: string
  courses: CourseRecord[]
  rank: number
  average: number
}

const seedSemesters: SemesterRecord[] = []

const randomScore = (min = 60, max = 99) => Math.floor(Math.random() * (max - min + 1)) + min

export function generateMockSemesters(studentId: number) {
  const semesters = [
    { name: '111 學年度第 1 學期', baseId: 1000 },
    { name: '111 學年度第 2 學期', baseId: 2000 },
    { name: '112 學年度第 1 學期', baseId: 3000 },
    { name: '112 學年度第 2 學期', baseId: 4000 },
    { name: '113 學年度第 1 學期', baseId: 5000 },
    { name: '113 學年度第 2 學期', baseId: 6000 },
  ]

  const subjects = [
    { name: '資料結構', credits: 3 },
    { name: '演算法', credits: 3 },
    { name: '作業系統', credits: 3 },
    { name: '計算機組織', credits: 3 },
    { name: '線性代數', credits: 3 },
    { name: '機率與統計', credits: 3 },
    { name: '資料庫系統', credits: 3 },
    { name: '人工智慧導論', credits: 3 },
    { name: '網頁程式設計', credits: 3 },
    { name: '計算機網路', credits: 3 },
  ]

  const count = 5 + (studentId % 2)
  const result: SemesterRecord[] = []

  for (let i = 0; i < count; i++) {
    const sem = semesters[i]
    if (!sem) continue
    const courseCount = 8 + (studentId % 3)
    const courses: CourseRecord[] = []
    const usedSubjects = new Set<number>()

    let totalScore = 0
    let totalCredits = 0

    while (courses.length < courseCount) {
      const idx = Math.floor(Math.random() * subjects.length)
      if (usedSubjects.has(idx)) continue
      usedSubjects.add(idx)

      const score = randomScore()
      const subject = subjects[idx]
      if (!subject) continue

      courses.push({
        code: `CS${1000 + idx}`,
        name: subject.name,
        credits: subject.credits,
        score,
      })

      totalScore += score * subject.credits
      totalCredits += subject.credits
    }

    result.push({
      id: sem.baseId + studentId,
      studentId,
      semesterName: sem.name,
      courses,
      rank: Math.floor(Math.random() * 20) + 1,
      average: Number((totalScore / totalCredits).toFixed(2)),
    })
  }
  return result
}

for (let i = 1; i <= 20; i++) {
  seedSemesters.push(...generateMockSemesters(i))
}

export const useSemesterStore = defineStore('semesters', () => {
  const semesters = ref<SemesterRecord[]>([...seedSemesters])

  const getStudentSemesters = (studentId: number) => {
    return semesters.value.filter((s) => s.studentId === studentId)
  }

  const generateForStudent = (studentId: number) => {
    const newSemesters = generateMockSemesters(studentId)
    semesters.value.push(...newSemesters)
  }

  const addSemester = (studentId: number) => {
    const newId = Math.max(...semesters.value.map((s) => s.id), 0) + 1
    const newSemester: SemesterRecord = {
      id: newId,
      studentId,
      semesterName: '新學期',
      courses: [],
      rank: 0,
      average: 0,
    }
    semesters.value.push(newSemester)
    return newSemester
  }

  const updateSemester = (id: number, payload: Partial<SemesterRecord>) => {
    const index = semesters.value.findIndex((s) => s.id === id)
    if (index === -1) return
    const current = semesters.value[index]
    if (!current) return

    if (payload.courses) {
      const totalScore = payload.courses.reduce((sum, c) => sum + c.score * c.credits, 0)
      const totalCredits = payload.courses.reduce((sum, c) => sum + c.credits, 0)
      payload.average = totalCredits > 0 ? Number((totalScore / totalCredits).toFixed(2)) : 0
    }

    Object.assign(current, payload)
  }

  const removeSemester = (id: number) => {
    const index = semesters.value.findIndex((s) => s.id === id)
    if (index !== -1) {
      semesters.value.splice(index, 1)
    }
  }

  const removeByStudentId = (studentId: number) => {
    semesters.value = semesters.value.filter((s) => s.studentId !== studentId)
  }

  return {
    semesters,
    getStudentSemesters,
    generateForStudent,
    addSemester,
    updateSemester,
    removeSemester,
    removeByStudentId,
  }
})