// Interface สำหรับข้อมูลคอร์สเรียน (Public Course Data)
export interface Course {
  id: number
  title: string | { th: string; en: string } // รองรับ 2 ภาษา
  slug: string
  description: string | { th: string; en: string }
  thumbnail_url: string
  price: string
  is_free: boolean
  original_price?: string
  have_certificate: boolean
  status: string // DRAFT, PUBLISHED
  category_id: number
  created_at?: string
  updated_at?: string
  created_by?: number
  updated_by?: number
  approved_at?: string
  approved_by?: number
  rejection_reason?: string
  enrolled?: boolean
  total_lessons?: number
  

  rating?: string
  lessons?: number | string
  levelType?: 'neutral' | 'warning' | 'success' // ใช้สำหรับการแสดงผล Badge ระดับความยาก (Frontend Logic)
  
  // โครงสร้างบทเรียน (Chapters & Lessons)
  chapters?: {
    id: number
    title: string | { th: string; en: string }
    lessons: {
      id: number
      title: string | { th: string; en: string }
      duration_minutes: number
      video_url?: string
    }[]
  }[]

  // ข้อมูลผู้สอนและเจ้าของคอร์ส
  creator?: {
    id: number
    username: string
    email: string
    profile: {
      first_name: string
      last_name: string
      avatar_url: string
    }
  }
  instructors?: {
    user_id: number
    is_primary: boolean
    user: {
      id: number
      username: string
      email: string
      profile: {
        first_name: string
        last_name: string
        avatar_url: string
      }
    }
  }[]
}

interface CourseResponse {
  code: number
  message: string
  data: Course[]
  total: number
  page?: number
  limit?: number
  totalPages?: number
}

interface SingleCourseResponse {
  code: number
  message: string
  data: Course
}

// Interface สำหรับคอร์สที่ผู้ใช้ลงทะเบียนเรียนแล้ว (My Course)
export interface EnrolledCourse {
    id: number
    course_id: number
    course: Course
    status: 'ENROLLED' | 'IN_PROGRESS' | 'COMPLETED' | 'DROPPED'
    progress_percentage: number
    enrolled_at: string
    started_at?: string
    completed_at?: string
    last_accessed_at?: string
}

interface EnrolledCourseResponse {
    code: number
    message: string
    data: EnrolledCourse[]
    total: number
    page: number
    limit: number
}

// Interface สำหรับการส่งคำตอบแบบทดสอบ (Quiz Submission)
export interface QuizAnswerSubmission {
    question_id: number
    choice_id: number
}

export interface QuizSubmitRequest {
    answers: QuizAnswerSubmission[]
}

// Interface สำหรับผลลัพธ์การสอบ (Quiz Result)
export interface QuizResult {
    answers_review: {
        score: number
        is_correct: boolean
        correct_choice_id: number
        selected_choice_id: number
        question_id: number
    }[]
    completed_at: string
    started_at: string
    attempt_number: number
    passing_score: number
    is_passed: boolean
    correct_answers: number
    total_questions: number
    total_score: number
    score: number
    quiz_id: number
    attempt_id: number
}

// Interface สำหรับ Certificate
export interface Certificate {
    certificate_id: number
    course_id: number
    course_title: {
        en: string
        th: string
    }
    issued_at: string
    download_url: string
}

// ==========================================
// Composable: useCourse
// หน้าที่: จัดการ Logic ทุกอย่างเกี่ยวกับคอร์สเรียน
// - ดึงข้อมูลคอร์ส (Public & Protected)
// - ลงทะเบียนเรียน (Enroll)
// - ติดตามความคืบหน้าการเรียน (Progress tracking)
export const useCourse = () => {
    const config = useRuntimeConfig()
    const API_BASE_URL = config.public.apiBase as string
    const { token } = useAuth()

    // ใช้ useState เพื่อเก็บรายชื่อคอร์สทั้งหมดใน Memory (สำหรับกรณีดึงทั้งหมด)
    const coursesState = useState<Course[]>('courses_cache', () => [])
    const isCoursesLoaded = useState<boolean>('courses_loaded', () => false)

    /**
     * ดึงรายชื่อคอร์สทั้งหมด (Catalog)
     * รองรับการกรองด้วยหมวดหมู่ และ Pagination
     * Endpoint: GET /courses
     */
    const fetchCourses = async (params: { 
        category_id?: number; 
        page?: number; 
        limit?: number; 
        random?: boolean; 
        is_recommended?: boolean; 
        forceRefresh?: boolean 
    } = {}) => {
        const { forceRefresh = false, ...apiParams } = params

        // ใช้ Cache เฉพาะกรณีดึง "ทั้งหมด" แบบปกติ (ไม่มี params)
        const isRequestingAll = Object.keys(apiParams).length === 0
        if (isRequestingAll && isCoursesLoaded.value && !forceRefresh && coursesState.value.length > 0) {
            return {
                success: true,
                data: coursesState.value,
                total: coursesState.value.length
            }
        }

        try {
            // สร้าง Query String
            const queryParams = new URLSearchParams()
            if (apiParams.category_id) queryParams.append('category_id', apiParams.category_id.toString())
            if (apiParams.page) queryParams.append('page', apiParams.page.toString())
            if (apiParams.limit) queryParams.append('limit', apiParams.limit.toString())
            if (apiParams.random !== undefined) queryParams.append('random', apiParams.random.toString())
            if (apiParams.is_recommended !== undefined) queryParams.append('is_recommended', apiParams.is_recommended.toString())

            const queryString = queryParams.toString()
            const url = `${API_BASE_URL}/courses${queryString ? `?${queryString}` : ''}`

            const data = await $fetch<CourseResponse>(url, {
                method: 'GET',
                headers: token.value ? {
                    Authorization: `Bearer ${token.value}`
                } : {}
            })

            const courses = data.data || []
            
            // เก็บลง State เฉพาะกรณีดึง "ทั้งหมด"
            if (isRequestingAll) {
                coursesState.value = courses
                isCoursesLoaded.value = true
            }

            return { 
                success: true, 
                data: courses, 
                total: data.total || 0,
                page: data.page,
                limit: data.limit,
                totalPages: data.totalPages
            }
        } catch (err: any) {
            console.error('Fetch courses failed:', err)
            
            // Retry logic logic for 429
            if (err.statusCode === 429 || err.status === 429) {
                await new Promise(resolve => setTimeout(resolve, 1500))
                return fetchCourses(params) // Recursive retry
            }

             return { 
                success: false, 
                error: err.data?.message || err.message || 'Error fetching courses' 
            }
        }
    }

    /**
     * ดึงรายละเอียดคอร์สตาม ID
     * Endpoint: GET /courses/:id
     */
    const fetchCourseById = async (id: number) => {
        try {
            const data = await $fetch<SingleCourseResponse>(`${API_BASE_URL}/courses/${id}`, {
                method: 'GET',
                headers: token.value ? {
                    Authorization: `Bearer ${token.value}`
                } : {}
            })

            if (!data.data) throw new Error('Course not found')

            return { 
                success: true, 
                data: data.data // ข้อมูลคอร์สตัวเดียว
            }
        } catch (err: any) {
             console.error('Fetch course details failed:', err)
             return { 
                success: false, 
                error: err.data?.message || err.message || 'Error fetching course details' 
            }
        }
    }

    // ฟังก์ชันลงทะเบียนเรียน (Enroll)
    // Endpoint: POST /students/courses/:id/enroll
    const enrollCourse = async (courseId: number) => {
        try {
            const data = await $fetch<{ code: number; message: string; data: any }>(`${API_BASE_URL}/students/courses/${courseId}/enroll`, {
                method: 'POST',
                headers: token.value ? {
                    Authorization: `Bearer ${token.value}`
                } : {}
            })

            return {
                success: true,
                data: data.data,
                message: data.message
            }
        } catch (err: any) {
            const status = err.statusCode || err.status || err.response?.status
            const errorData = err.data?.error || err.data
            
            // เช็ค Error 409 Conflict หรือ 400 Bad Request (กรณีลงทะเบียนไปแล้ว)
            // สำหรับกรณีนี้ เราจะไม่ log console.error ให้รกหน้าจอเพราะเป็นเรื่องที่ดักจับได้
            if (status === 409 || (status === 400 && errorData?.message?.includes('Already enrolled'))) {
                return {
                    success: false,
                    error: 'ท่านได้ลงทะเบียนไปแล้ว',
                    code: 409 // treat internally as conflict
                }
            }

            console.error('Enroll course failed:', err)
            return {
                success: false,
                error: errorData?.message || err.message || 'Error enrolling in course',
                code: errorData?.code || err.data?.code
            }
        }
    }

    // ฟังก์ชันดึงคอร์สที่ฉันลงทะเบียนเรียน (My Courses)
    // รองรับ Pagination และการกรอง Status (ENROLLED, IN_PROGRESS, COMPLETED)
    const fetchEnrolledCourses = async (params: { page?: number; limit?: number; status?: string } = {}) => {
        try {
            const queryParams = new URLSearchParams()
            if (params.page) queryParams.append('page', params.page.toString())
            if (params.limit) queryParams.append('limit', params.limit.toString())
            if (params.status && params.status !== 'ALL') queryParams.append('status', params.status)

            const data = await $fetch<EnrolledCourseResponse>(`${API_BASE_URL}/students/courses?${queryParams.toString()}`, {
                method: 'GET',
                headers: token.value ? {
                    Authorization: `Bearer ${token.value}`
                } : {}
            })

            return {
                success: true,
                data: data.data || [],
                total: data.total || 0,
                page: data.page,
                limit: data.limit
            }
        } catch (err: any) {
            console.error('Fetch enrolled courses failed:', err)

            // Retry for 429
            if (err.statusCode === 429 || err.status === 429) {
                 await new Promise(resolve => setTimeout(resolve, 1500));
                 try {
                     const queryParams = new URLSearchParams()
                     if (params.page) queryParams.append('page', params.page.toString())
                     if (params.limit) queryParams.append('limit', params.limit.toString())
                     if (params.status && params.status !== 'ALL') queryParams.append('status', params.status)
                     
                     const retryData = await $fetch<EnrolledCourseResponse>(`${API_BASE_URL}/students/courses?${queryParams.toString()}`, {
                        method: 'GET',
                        headers: token.value ? { Authorization: `Bearer ${token.value}` } : {}
                    })
                    return { success: true, data: retryData.data || [], total: retryData.total || 0, page: retryData.page, limit: retryData.limit }
                 } catch (retryErr) {
                     console.error('Retry fetch enrolled courses failed:', retryErr)
                 }
            }

            return {
                success: false,
                error: err.data?.message || err.message || 'Error fetching enrolled courses'
            }
        }
    }

    // ฟังก์ชันดึงข้อมูลสำหรับการเรียน (Chapters, Lessons, Progress)
    // Endpoint: GET /students/courses/:id/learn
    const fetchCourseLearningInfo = async (courseId: number) => {
        try {
            const data = await $fetch<{ code: number; message: string; data: any }>(`${API_BASE_URL}/students/courses/${courseId}/learn`, {
                method: 'GET',
                headers: token.value ? {
                    Authorization: `Bearer ${token.value}`
                } : {}
            })

            return {
                success: true,
                data: data.data
            }
        } catch (err: any) {
            console.error('Fetch course learning info failed:', err)
            
            // Retry for 429
            if (err.statusCode === 429 || err.status === 429) {
                await new Promise(resolve => setTimeout(resolve, 1500));
                try {
                     const retryData = await $fetch<{ code: number; message: string; data: any }>(`${API_BASE_URL}/students/courses/${courseId}/learn`, {
                        method: 'GET',
                        headers: token.value ? { Authorization: `Bearer ${token.value}` } : {}
                    })
                    return { success: true, data: retryData.data }
                } catch (retryErr) {
                     console.error('Retry fetch course learning info failed:', retryErr)
                }
            }

            return {
                success: false,
                error: err.data?.message || err.message || 'Error fetching course learning info',
                code: err.data?.code
            }
        }
    }

    // ฟังก์ชันดึงเนื้อหาบทเรียน (Video, Content)
    // Endpoint: GET /students/courses/:cid/lessons/:lid
    const fetchLessonContent = async (courseId: number, lessonId: number) => {
        try {
            const data = await $fetch<{ code: number; message: string; data: any; progress?: any }>(`${API_BASE_URL}/students/courses/${courseId}/lessons/${lessonId}`, {
                method: 'GET',
                headers: token.value ? {
                    Authorization: `Bearer ${token.value}`
                } : {}
            })

            return {
                success: true,
                data: data.data,
                progress: data.progress
            }
        } catch (err: any) {
            console.error('Fetch lesson content failed:', err)
            return {
                success: false,
                error: err.data?.message || err.message || 'Error fetching lesson content',
                code: err.data?.code,
                status: err.status
            }
        }
    }

    // ฟังก์ชันเช็คสิทธิ์การเข้าถึงบทเรียน (Access Control)
    // ต้อง Enrolled ก่อนถึงจะเข้าได้ และต้องผ่านเงื่อนไข Prerequisites (ถ้ามี)
    // Endpoint: GET /students/courses/:cid/lessons/:lid/access-check
    const checkLessonAccess = async (courseId: number, lessonId: number) => {
        try {
            const data = await $fetch<{ code: number; message: string; data: any }>(`${API_BASE_URL}/students/courses/${courseId}/lessons/${lessonId}/access-check`, {
                method: 'GET',
                headers: token.value ? {
                    Authorization: `Bearer ${token.value}`
                } : {}
            })

            return {
                success: true,
                data: data.data
            }
        } catch (err: any) {
            console.error('Check lesson access failed:', err)
            return {
                success: false,
                error: err.data?.message || err.message || 'Error checking lesson access',
                code: err.data?.code,
                status: err.status
            }
        }
    }

    // ฟังก์ชันบันทึกเวลาที่ดูวิดีโอ (Video Progress)
    // Endpoint: POST /students/lessons/:id/progress
    const saveVideoProgress = async (lessonId: number, progressSeconds: number, durationSeconds: number, keepalive: boolean = false) => {
        try {
            const data = await $fetch<{ code: number; message: string; data: any }>(`${API_BASE_URL}/students/lessons/${lessonId}/progress`, {
                method: 'POST',
                headers: token.value ? {
                    Authorization: `Bearer ${token.value}`
                } : {},
                body: {
                    video_progress_seconds: progressSeconds,
                    video_duration_seconds: durationSeconds
                },
                keepalive: keepalive 
            })

            return {
                success: true,
                data: data.data
            }
        } catch (err: any) {
            console.error('Save video progress failed:', err)
            return {
                success: false,
                error: err.data?.message || err.message || 'Error saving video progress',
                code: err.data?.code
            }
        }
    }

    // ฟังก์ชันดึง Video Progress ปัจจุบันของบทเรียน
    // Endpoint: GET /students/lessons/:id/progress
    const fetchVideoProgress = async (lessonId: number) => {
        try {
             const data = await $fetch<{ code: number; message: string; data: any }>(`${API_BASE_URL}/students/lessons/${lessonId}/progress`, {
                method: 'GET',
                headers: token.value ? {
                    Authorization: `Bearer ${token.value}`
                } : {}
            })

            return {
                success: true,
                data: data.data
            }
        } catch (err: any) {
            console.error('Fetch video progress failed:', err)
            return {
                success: false,
                error: err.data?.message || err.message || 'Error fetching video progress',
                code: err.data?.code,
                status: err.status
            }
        }
    }

    // ฟังก์ชันบันทึกว่าเรียนจบบทเรียนแล้ว (Mark Complete)
    // Endpoint: POST /students/courses/:cid/lessons/:lid/complete
    const markLessonComplete = async (courseId: number, lessonId: number) => {
        try {
            const data = await $fetch<{ code: number; message: string; data: any }>(`${API_BASE_URL}/students/courses/${courseId}/lessons/${lessonId}/complete`, {
                method: 'POST',
                headers: token.value ? {
                    Authorization: `Bearer ${token.value}`
                } : {}
            })

            return {
                success: true,
                data: data.data
            }
        } catch (err: any) {
            console.error('Mark lesson complete failed:', err)
            return {
                success: false,
                error: err.data?.message || err.message || 'Error marking lesson as complete',
                code: err.data?.code,
                status: err.status
            }
        }
    }




    // ฟังก์ชันส่งคำตอบ Quiz
    // Endpoint: POST /students/courses/:cid/lessons/:lid/quiz/submit
    const submitQuiz = async (courseId: number, lessonId: number, answers: QuizAnswerSubmission[], alreadyPassed: boolean = false) => {
        try {
            // NOTE: Backend crashes with 500 if we send extra fields like 'already_passed'. 
            // Reverting to strict body structure.
            const body = { answers }

            const data = await $fetch<{ code: number; message: string; data: QuizResult }>(`${API_BASE_URL}/students/courses/${courseId}/lessons/${lessonId}/quiz/submit`, {
                method: 'POST',
                headers: token.value ? {
                    Authorization: `Bearer ${token.value}`
                } : {},
                body: body
            })

            return {
                success: true,
                data: data.data
            }
        } catch (err: any) {
            console.error('Submit quiz failed:', err)
             return {
                success: false,
                error: err.data?.message || err.message || 'Error submitting quiz',
                code: err.data?.code,
                status: err.status
            }
        }
    }



    // ฟังก์ชันสร้างใบ Certificate (Create/Generate)
    // Endpoint: POST /certificates/:courseId/generate
    const generateCertificate = async (courseId: number) => {
        try {
            const data = await $fetch<{ code: number; message: string; data: Certificate }>(`${API_BASE_URL}/certificates/${courseId}/generate`, {
                method: 'POST',
                headers: token.value ? {
                    Authorization: `Bearer ${token.value}`
                } : {}
            })

            return {
                success: true,
                data: data.data
            }
        } catch (err: any) {
            console.error('Generate certificate failed:', err)
            return {
                success: false,
                error: err.data?.message || err.message || 'Error generating certificate',
                code: err.data?.code,
                status: err.status
            }
        }
    }

    // ฟังก์ชันดึงใบ Certificate ของคอร์สที่ระบุ (แบบเดี่ยว - ใหม่)
    // Endpoint: GET /certificates/:courseId
    const getCertificate = async (courseId: number) => {
        try {
            const data = await $fetch<{ code: number; message: string; data: Certificate }>(`${API_BASE_URL}/certificates/${courseId}`, {
                method: 'GET',
                headers: token.value ? {
                    Authorization: `Bearer ${token.value}`
                } : {}
            })

            return {
                success: true,
                data: data.data // Return single certificate object
            }
        } catch (err: any) {
            console.error('Get certificate failed:', err)
            return {
                success: false,
                error: err.data?.message || err.message || 'Error getting certificate',
                code: err.data?.code,
                status: err.status
            }
        }
    }

    // ฟังก์ชันดึงประกาศของคอร์ส (Announcements)
    // Endpoint: GET /student/courses/:id/announcements (Note: 'student' singular based on recent API update)
    const fetchCourseAnnouncements = async (courseId: number) => {
        try {
            const data = await $fetch<{ code: number; message: string; data: any[] }>(`${API_BASE_URL}/student/courses/${courseId}/announcements`, {
                method: 'GET',
                headers: token.value ? {
                    Authorization: `Bearer ${token.value}`
                } : {}
            })

            return {
                success: true,
                data: data.data
            }
        } catch (err: any) {
            console.error('Fetch course announcements failed:', err)
            return {
                success: false,
                error: err.data?.message || err.message || 'Error fetching announcements',
                code: err.data?.code,
                status: err.status
            }
        }
    }

    // ฟังก์ชันดึงรายการใบ Certificate ทั้งหมดของผู้ใช้ (ใหม่)
    // Endpoint: GET /certificates
    const fetchAllCertificates = async () => {
        try {
            const data = await $fetch<{ code: number; message: string; data: Certificate[] }>(`${API_BASE_URL}/certificates`, {
                method: 'GET',
                headers: token.value ? {
                    Authorization: `Bearer ${token.value}`
                } : {}
            })

            return {
                success: true,
                data: data.data || []
            }
        } catch (err: any) {
            console.error('Fetch all certificates failed:', err)
            return {
                success: false,
                error: err.data?.message || err.message || 'Error fetching certificates',
                code: err.data?.code,
                status: err.status
            }
        }
    }

    const { locale } = useI18n()

    /**
     * Helper: แปลงข้อมูล 2 ภาษาเป็นข้อความตาม locale ปัจจุบัน หรือค่าที่มีอยู่
     */
    const getLocalizedText = (text: string | { th: string; en: string } | undefined | null) => {
        if (!text) return ''
        if (typeof text === 'string') return text
        
        // Return based on current locale, fallback to th then en
        const currentLocale = locale.value as 'th' | 'en'
        // @ts-ignore
        return text[currentLocale] || text.th || text.en || ''
    }

    return {
        getLocalizedText,
        fetchCourses,
        fetchCourseById,
        enrollCourse,
        fetchEnrolledCourses,
        fetchCourseLearningInfo,
        fetchLessonContent,
        checkLessonAccess,
        saveVideoProgress,
        fetchVideoProgress,
        markLessonComplete,
        submitQuiz,
        generateCertificate,
        getCertificate,
        fetchAllCertificates,
        fetchCourseAnnouncements
    }
}