package syncjobs

import (
	"context"
	"encoding/json"
	"errors"
	"log"
	"sync"
	"time"

	"server/internal/models"
	"server/internal/qldt"

	"gorm.io/gorm"
	"gorm.io/gorm/clause"
)

// Trạng thái đồng bộ sinh viên toàn hệ thống
type StudentsSyncStatus struct {
	Running   bool   `json:"running"`
	Done      bool   `json:"done"`
	Error     string `json:"error,omitempty"`
	Page      int    `json:"page"`
	PageSize  int    `json:"pageSize"`
	Total     int    `json:"total"`
	Synced    int    `json:"synced"`
	UpdatedAt int64  `json:"updatedAt"`
}

type StudentsSyncJob struct {
	mu     sync.RWMutex
	status StudentsSyncStatus
}

func NewStudentsSyncJob() *StudentsSyncJob {
	return &StudentsSyncJob{
		status: StudentsSyncStatus{UpdatedAt: time.Now().Unix()},
	}
}

func (j *StudentsSyncJob) Status() StudentsSyncStatus {
	j.mu.RLock()
	defer j.mu.RUnlock()
	return j.status
}

func (j *StudentsSyncJob) Start(db *gorm.DB, client *qldt.Client, token string) bool {
	j.mu.Lock()
	if j.status.Running {
		j.mu.Unlock()
		return false
	}
	j.status = StudentsSyncStatus{
		Running:   true,
		Done:      false,
		Page:      0,
		PageSize:  100,
		Total:     0,
		Synced:    0,
		UpdatedAt: time.Now().Unix(),
	}
	j.mu.Unlock()

	go j.run(db, client, token)
	return true
}

func (j *StudentsSyncJob) run(db *gorm.DB, client *qldt.Client, token string) {
	defer func() {
		j.mu.Lock()
		j.status.Running = false
		j.status.Done = j.status.Error == ""
		j.status.UpdatedAt = time.Now().Unix()
		j.mu.Unlock()
	}()

	ctx, cancel := context.WithTimeout(context.Background(), 20*time.Minute)
	defer cancel()

	pageSize := 100
	page := 1
	total := 0
	synced := 0

	for {
		res, err := client.GetStudents(ctx, token, page, pageSize)
		if err != nil {
			j.setError(err.Error())
			return
		}
		if total == 0 {
			total = res.Total
		}
		if len(res.Data) == 0 {
			break
		}

		batch := make([]models.Student, 0, len(res.Data))
		for _, s := range res.Data {
			var dob *time.Time
			if s.DateOfBirth != nil && *s.DateOfBirth != "" {
				if t, err := time.Parse("2006-01-02", *s.DateOfBirth); err == nil {
					dob = &t
				}
			}

			st := models.Student{
				RkID:        s.ID,
				StudentCode: s.StudentCode,
				FullName:    s.FullName,
				Phone:       s.Phone,
				Email:       s.Email,
				DateOfBirth: dob,
				Gender:      s.Gender,
				Status:      s.Status,
				Location:    s.Location,
			}
			if s.System != nil {
				sysID := s.System.ID
				sysName := s.System.Name
				st.SystemID = &sysID
				st.SystemName = &sysName
			}
			batch = append(batch, st)
		}

		if err := db.Clauses(clause.OnConflict{
			Columns: []clause.Column{{Name: "rk_id"}},
			DoUpdates: clause.AssignmentColumns([]string{
				"student_code",
				"full_name",
				"phone",
				"email",
				"date_of_birth",
				"gender",
				"status",
				"location",
				"system_id",
				"system_name",
				"updated_at",
			}),
		}).CreateInBatches(batch, 100).Error; err != nil {
			j.setError("Failed to save students to DB: " + err.Error())
			return
		}

		synced += len(batch)

		j.mu.Lock()
		j.status.Page = page
		j.status.PageSize = pageSize
		j.status.Total = total
		j.status.Synced = synced
		j.status.UpdatedAt = time.Now().Unix()
		j.mu.Unlock()

		if synced >= total || len(res.Data) < pageSize {
			break
		}
		page++
		time.Sleep(50 * time.Millisecond) // Tránh spam API quá tải
	}
}

func (j *StudentsSyncJob) setError(msg string) {
	j.mu.Lock()
	defer j.mu.Unlock()
	j.status.Error = msg
	j.status.UpdatedAt = time.Now().Unix()
}

// Trạng thái đồng bộ lớp học và sinh viên của lớp
type ClassesSyncStatus struct {
	Running   bool   `json:"running"`
	Done      bool   `json:"done"`
	Error     string `json:"error,omitempty"`
	Total     int    `json:"total"`
	Synced    int    `json:"synced"`
	UpdatedAt int64  `json:"updatedAt"`
}

type ClassesSyncJob struct {
	mu     sync.RWMutex
	status ClassesSyncStatus
}

func NewClassesSyncJob() *ClassesSyncJob {
	return &ClassesSyncJob{
		status: ClassesSyncStatus{UpdatedAt: time.Now().Unix()},
	}
}

func (j *ClassesSyncJob) Status() ClassesSyncStatus {
	j.mu.RLock()
	defer j.mu.RUnlock()
	return j.status
}

func (j *ClassesSyncJob) Start(db *gorm.DB, client *qldt.Client, token string) bool {
	j.mu.Lock()
	if j.status.Running {
		j.mu.Unlock()
		return false
	}
	j.status = ClassesSyncStatus{
		Running:   true,
		Done:      false,
		Total:     0,
		Synced:    0,
		UpdatedAt: time.Now().Unix(),
	}
	j.mu.Unlock()

	go j.run(db, client, token)
	return true
}

func (j *ClassesSyncJob) run(db *gorm.DB, client *qldt.Client, token string) {
	defer func() {
		j.mu.Lock()
		j.status.Running = false
		j.status.Done = j.status.Error == ""
		j.status.UpdatedAt = time.Now().Unix()
		j.mu.Unlock()
	}()

	ctx, cancel := context.WithTimeout(context.Background(), 20*time.Minute)
	defer cancel()

	// 1. Lấy toàn bộ lớp học từ hệ thống chính (System ID = 0 đại diện cho tất cả)
	res, err := client.GetClassesBySystem(ctx, token, 0)
	if err != nil {
		j.setError("Failed to fetch classes: " + err.Error())
		return
	}

	j.mu.Lock()
	j.status.Total = len(res.Data)
	j.status.UpdatedAt = time.Now().Unix()
	j.mu.Unlock()

	var syncedClassIDs []int64
	for _, c := range res.Data {
		syncedClassIDs = append(syncedClassIDs, c.ID)
	}

	// Đồng bộ từng lớp
	for idx, cl := range res.Data {
		tx := db.Begin()
		if tx.Error != nil {
			j.setError("Failed to start transaction: " + tx.Error.Error())
			return
		}

		// Map thông tin class
		classRow := models.Class{
			RkID:         cl.ID,
			Name:         cl.Name,
			ClassCode:    cl.ClassCode,
			Type:         cl.Type,
			StudentCount: cl.StudentCount,
		}

		if cl.Specializes != nil {
			specID := cl.Specializes.ID
			specName := cl.Specializes.Name
			classRow.SpecializeRkID = &specID
			classRow.SpecializeName = &specName
			if cl.Specializes.Systems != nil {
				sysID := cl.Specializes.Systems.ID
				sysCode := cl.Specializes.Systems.SystemCode
				sysName := cl.Specializes.Systems.Name
				classRow.SystemRkID = &sysID
				classRow.SystemCode = &sysCode
				classRow.SystemName = &sysName
			}
		}

		// Xem lớp học hiện tại trong DB
		var existing models.Class
		err := tx.Where("rk_id = ?", cl.ID).First(&existing).Error
		if errors.Is(err, gorm.ErrRecordNotFound) {
			classRow.IsStudying = false // Lớp mới mặc định chưa học
			if err := tx.Create(&classRow).Error; err != nil {
				tx.Rollback()
				j.setError("Failed to insert class: " + err.Error())
				return
			}
		} else if err != nil {
			tx.Rollback()
			j.setError("Lookup class failed: " + err.Error())
			return
		} else {
			// Giữ trạng thái IsStudying cũ
			classRow.ID = existing.ID
			classRow.IsStudying = existing.IsStudying
			classRow.CreatedAt = existing.CreatedAt
			if err := tx.Save(&classRow).Error; err != nil {
				tx.Rollback()
				j.setError("Failed to update class: " + err.Error())
				return
			}
		}

		// Lưu liên kết Course
		if err := tx.Where("class_rk_id = ?", cl.ID).Delete(&models.ClassCourseLink{}).Error; err != nil {
			tx.Rollback()
			j.setError("Failed to clear old class course links: " + err.Error())
			return
		}

		var courseLinks []models.ClassCourseLink
		for ord, co := range cl.Courses {
			if co.ID == 0 {
				continue
			}
			courseLinks = append(courseLinks, models.ClassCourseLink{
				ClassRkID:   cl.ID,
				CourseRkID:  co.ID,
				CourseName:  co.Name,
				CourseOrder: ord,
			})
		}
		if len(courseLinks) > 0 {
			if err := tx.Create(&courseLinks).Error; err != nil {
				tx.Rollback()
				j.setError("Failed to insert class course links: " + err.Error())
				return
			}
		}

		// Đồng bộ sinh viên của lớp: Gọi class dashboard để trích xuất sinh viên
		// Ta chọn course đầu tiên của lớp để kéo thông tin sinh viên
		var classStudentsToMap []models.ClassStudent
		if len(cl.Courses) > 0 && cl.Courses[0].ID > 0 {
			dashboardJSON, err := client.GetClassDashboard(ctx, token, cl.ID, cl.Courses[0].ID)
			if err != nil {
				// Nếu lấy dashboard lỗi thì log lại nhưng không dừng tiến trình sync lớp
				log.Printf("Warning: failed to get dashboard for class ID %d, course ID %d: %v", cl.ID, cl.Courses[0].ID, err)
			} else {
				stList, err := extractStudentsFromDashboard(dashboardJSON)
				if err != nil {
					log.Printf("Warning: failed to parse students from dashboard class %d: %v", cl.ID, err)
				} else if len(stList) > 0 {
					// Upsert sinh viên vào table students
					if err := tx.Clauses(clause.OnConflict{
						Columns: []clause.Column{{Name: "rk_id"}},
						DoUpdates: clause.AssignmentColumns([]string{
							"student_code",
							"full_name",
							"phone",
							"email",
							"date_of_birth",
							"gender",
							"status",
							"location",
							"system_id",
							"system_name",
							"updated_at",
						}),
					}).Create(&stList).Error; err != nil {
						tx.Rollback()
						j.setError("Failed to save class students: " + err.Error())
						return
					}

					// Lưu map Class-Student
					for _, st := range stList {
						classStudentsToMap = append(classStudentsToMap, models.ClassStudent{
							ClassRkID:   cl.ID,
							StudentRkID: st.RkID,
						})
					}
				}
			}
		}

		// Cập nhật map Class-Student trong DB (xóa map cũ, insert map mới)
		if err := tx.Where("class_rk_id = ?", cl.ID).Delete(&models.ClassStudent{}).Error; err != nil {
			tx.Rollback()
			j.setError("Failed to clear old class students mapping: " + err.Error())
			return
		}
		if len(classStudentsToMap) > 0 {
			if err := tx.Clauses(clause.OnConflict{
				DoNothing: true, // Tránh trùng lặp do lỗi nào đó
			}).Create(&classStudentsToMap).Error; err != nil {
				tx.Rollback()
				j.setError("Failed to map class students: " + err.Error())
				return
			}
		}

		if err := tx.Commit().Error; err != nil {
			j.setError("Transaction commit failed: " + err.Error())
			return
		}

		j.mu.Lock()
		j.status.Synced = idx + 1
		j.status.UpdatedAt = time.Now().Unix()
		j.mu.Unlock()

		time.Sleep(50 * time.Millisecond) // Thở tí tránh spam API
	}

	// 2. Xóa các lớp học không còn tồn tại trên QLĐT
	if len(syncedClassIDs) > 0 {
		db.Where("rk_id NOT IN ?", syncedClassIDs).Delete(&models.Class{})
	} else {
		db.Session(&gorm.Session{AllowGlobalUpdate: true}).Delete(&models.Class{})
	}
}

func (j *ClassesSyncJob) setError(msg string) {
	j.mu.Lock()
	defer j.mu.Unlock()
	j.status.Error = msg
	j.status.UpdatedAt = time.Now().Unix()
}

// Helper giải nén danh sách sinh viên từ Dashboard JSON
func extractStudentsFromDashboard(payloadJSON []byte) ([]models.Student, error) {
	var root interface{}
	if err := json.Unmarshal(payloadJSON, &root); err != nil {
		return nil, err
	}

	var arr []interface{}
	if m, ok := root.(map[string]interface{}); ok {
		if dataVal, exists := m["data"]; exists {
			if dArr, ok := dataVal.([]interface{}); ok {
				arr = dArr
			} else if dMap, ok := dataVal.(map[string]interface{}); ok {
				for _, k := range []string{"studentsInClass", "students", "rows", "items"} {
					if val, exists := dMap[k]; exists {
						if innerArr, ok := val.([]interface{}); ok {
							arr = innerArr
							break
						}
					}
				}
			}
		}
		if len(arr) == 0 {
			for _, k := range []string{"studentsInClass", "students", "rows", "items"} {
				if val, exists := m[k]; exists {
					if dArr, ok := val.([]interface{}); ok {
						arr = dArr
						break
					}
				}
			}
		}
	} else if sliceVal, ok := root.([]interface{}); ok {
		arr = sliceVal
	}

	var students []models.Student
	for _, item := range arr {
		m, ok := item.(map[string]interface{})
		if !ok || m == nil {
			continue
		}
		studentObj, ok := m["student"].(map[string]interface{})
		if !ok || studentObj == nil {
			continue
		}

		var rkID int64
		if idVal, exists := studentObj["id"]; exists {
			switch v := idVal.(type) {
			case float64:
				rkID = int64(v)
			case json.Number:
				if id64, err := v.Int64(); err == nil {
					rkID = id64
				}
			case int:
				rkID = int64(v)
			case int64:
				rkID = v
			}
		}
		if rkID == 0 {
			continue
		}

		stCode, _ := studentObj["studentCode"].(string)
		fullName, _ := studentObj["fullName"].(string)
		email, _ := studentObj["email"].(string)

		var phone *string
		if p, ok := studentObj["phone"].(string); ok && p != "" {
			phone = &p
		}

		var dob *time.Time
		if dobStr, ok := studentObj["dateOfBirth"].(string); ok && dobStr != "" {
			if t, err := time.Parse("2006-01-02", dobStr); err == nil {
				dob = &t
			}
		}

		var gender *int
		if gVal, exists := studentObj["gender"]; exists {
			var g int
			switch v := gVal.(type) {
			case float64:
				g = int(v)
			case json.Number:
				if i64, err := v.Int64(); err == nil {
					g = int(i64)
				}
			case int:
				g = v
			}
			gender = &g
		}

		status, _ := studentObj["status"].(string)
		location, _ := studentObj["location"].(string)

		student := models.Student{
			RkID:        rkID,
			StudentCode: stCode,
			FullName:    fullName,
			Phone:       phone,
			Email:       email,
			DateOfBirth: dob,
			Gender:      gender,
			Status:      &status,
			Location:    &location,
		}

		if sysVal, ok := studentObj["system"].(map[string]interface{}); ok && sysVal != nil {
			var sysID int64
			if sID, exists := sysVal["id"]; exists {
				switch v := sID.(type) {
				case float64:
					sysID = int64(v)
				case int64:
					sysID = v
				}
			}
			sysName, _ := sysVal["name"].(string)
			if sysID > 0 {
				student.SystemID = &sysID
				student.SystemName = &sysName
			}
		}

		students = append(students, student)
	}
	return students, nil
}