package handlers

import (
	"errors"
	"net/http"
	"strconv"

	"veza-backend-api/internal/core/education"
	apperrors "veza-backend-api/internal/errors"

	"github.com/gin-gonic/gin"
	"github.com/google/uuid"
	"go.uber.org/zap"
)

// EducationHandler handles education HTTP endpoints (v0.12.3 F276-F305)
type EducationHandler struct {
	service *education.Service
	logger  *zap.Logger
}

// NewEducationHandler creates a new EducationHandler
func NewEducationHandler(service *education.Service, logger *zap.Logger) *EducationHandler {
	return &EducationHandler{
		service: service,
		logger:  logger,
	}
}

// --- Course endpoints ---

// CreateCourse handles POST /courses
func (h *EducationHandler) CreateCourse(c *gin.Context) {
	userID, ok := GetUserIDUUID(c)
	if !ok {
		return
	}

	var req education.CreateCourseRequest
	if err := c.ShouldBindJSON(&req); err != nil {
		RespondWithAppError(c, apperrors.NewValidationError("Invalid request: title is required"))
		return
	}

	course, err := h.service.CreateCourse(c.Request.Context(), userID, req)
	if err != nil {
		if errors.Is(err, education.ErrSlugAlreadyTaken) {
			RespondWithAppError(c, apperrors.NewValidationError("Slug is already taken"))
			return
		}
		RespondWithAppError(c, apperrors.NewInternalErrorWrap("Failed to create course", err))
		return
	}

	RespondSuccess(c, http.StatusCreated, course)
}

// UpdateCourse handles PUT /courses/:id
func (h *EducationHandler) UpdateCourse(c *gin.Context) {
	userID, ok := GetUserIDUUID(c)
	if !ok {
		return
	}

	courseID, err := uuid.Parse(c.Param("id"))
	if err != nil {
		RespondWithAppError(c, apperrors.NewValidationError("Invalid course ID"))
		return
	}

	var req education.UpdateCourseRequest
	if err := c.ShouldBindJSON(&req); err != nil {
		RespondWithAppError(c, apperrors.NewValidationError("Invalid request body"))
		return
	}

	course, err := h.service.UpdateCourse(c.Request.Context(), userID, courseID, req)
	if err != nil {
		h.handleCourseError(c, err)
		return
	}

	RespondSuccess(c, http.StatusOK, course)
}

// PublishCourse handles POST /courses/:id/publish
func (h *EducationHandler) PublishCourse(c *gin.Context) {
	userID, ok := GetUserIDUUID(c)
	if !ok {
		return
	}

	courseID, err := uuid.Parse(c.Param("id"))
	if err != nil {
		RespondWithAppError(c, apperrors.NewValidationError("Invalid course ID"))
		return
	}

	course, err := h.service.PublishCourse(c.Request.Context(), userID, courseID)
	if err != nil {
		h.handleCourseError(c, err)
		return
	}

	RespondSuccess(c, http.StatusOK, course)
}

// ArchiveCourse handles POST /courses/:id/archive
func (h *EducationHandler) ArchiveCourse(c *gin.Context) {
	userID, ok := GetUserIDUUID(c)
	if !ok {
		return
	}

	courseID, err := uuid.Parse(c.Param("id"))
	if err != nil {
		RespondWithAppError(c, apperrors.NewValidationError("Invalid course ID"))
		return
	}

	course, err := h.service.ArchiveCourse(c.Request.Context(), userID, courseID)
	if err != nil {
		h.handleCourseError(c, err)
		return
	}

	RespondSuccess(c, http.StatusOK, course)
}

// GetCourse handles GET /courses/:id
func (h *EducationHandler) GetCourse(c *gin.Context) {
	courseID, err := uuid.Parse(c.Param("id"))
	if err != nil {
		RespondWithAppError(c, apperrors.NewValidationError("Invalid course ID"))
		return
	}

	course, err := h.service.GetCourse(c.Request.Context(), courseID)
	if err != nil {
		if errors.Is(err, education.ErrCourseNotFound) {
			RespondWithAppError(c, apperrors.NewNotFoundError("Course"))
			return
		}
		RespondWithAppError(c, apperrors.NewInternalErrorWrap("Failed to get course", err))
		return
	}

	RespondSuccess(c, http.StatusOK, course)
}

// GetCourseBySlug handles GET /courses/slug/:slug
func (h *EducationHandler) GetCourseBySlug(c *gin.Context) {
	slug := c.Param("slug")
	if slug == "" {
		RespondWithAppError(c, apperrors.NewValidationError("Slug is required"))
		return
	}

	course, err := h.service.GetCourseBySlug(c.Request.Context(), slug)
	if err != nil {
		if errors.Is(err, education.ErrCourseNotFound) {
			RespondWithAppError(c, apperrors.NewNotFoundError("Course"))
			return
		}
		RespondWithAppError(c, apperrors.NewInternalErrorWrap("Failed to get course", err))
		return
	}

	RespondSuccess(c, http.StatusOK, course)
}

// ListPublishedCourses handles GET /courses
func (h *EducationHandler) ListPublishedCourses(c *gin.Context) {
	limit, _ := strconv.Atoi(c.DefaultQuery("limit", "20"))
	limit = clampLimit(limit) // SECURITY(MEDIUM-004)
	offset, _ := strconv.Atoi(c.DefaultQuery("offset", "0"))

	var category *string
	if cat := c.Query("category"); cat != "" {
		category = &cat
	}
	var level *education.CourseLevel
	if lvl := c.Query("level"); lvl != "" {
		l := education.CourseLevel(lvl)
		level = &l
	}
	var language *string
	if lang := c.Query("language"); lang != "" {
		language = &lang
	}

	courses, total, err := h.service.ListPublishedCourses(c.Request.Context(), category, level, language, limit, offset)
	if err != nil {
		RespondWithAppError(c, apperrors.NewInternalErrorWrap("Failed to list courses", err))
		return
	}

	page := (offset / max(limit, 1)) + 1
	totalPages := int((total + int64(limit) - 1) / int64(limit))

	RespondSuccess(c, http.StatusOK, gin.H{
		"data": courses,
		"pagination": gin.H{
			"page":        page,
			"limit":       limit,
			"total":       total,
			"total_pages": totalPages,
		},
	})
}

// ListCreatorCourses handles GET /creators/me/courses
func (h *EducationHandler) ListCreatorCourses(c *gin.Context) {
	userID, ok := GetUserIDUUID(c)
	if !ok {
		return
	}

	limit, _ := strconv.Atoi(c.DefaultQuery("limit", "20"))
	limit = clampLimit(limit) // SECURITY(MEDIUM-004)
	offset, _ := strconv.Atoi(c.DefaultQuery("offset", "0"))

	courses, total, err := h.service.ListCreatorCourses(c.Request.Context(), userID, limit, offset)
	if err != nil {
		RespondWithAppError(c, apperrors.NewInternalErrorWrap("Failed to list courses", err))
		return
	}

	page := (offset / max(limit, 1)) + 1
	totalPages := int((total + int64(limit) - 1) / int64(limit))

	RespondSuccess(c, http.StatusOK, gin.H{
		"data": courses,
		"pagination": gin.H{
			"page":        page,
			"limit":       limit,
			"total":       total,
			"total_pages": totalPages,
		},
	})
}

// DeleteCourse handles DELETE /courses/:id
func (h *EducationHandler) DeleteCourse(c *gin.Context) {
	userID, ok := GetUserIDUUID(c)
	if !ok {
		return
	}

	courseID, err := uuid.Parse(c.Param("id"))
	if err != nil {
		RespondWithAppError(c, apperrors.NewValidationError("Invalid course ID"))
		return
	}

	if err := h.service.DeleteCourse(c.Request.Context(), userID, courseID); err != nil {
		h.handleCourseError(c, err)
		return
	}

	RespondSuccess(c, http.StatusOK, gin.H{"message": "Course deleted"})
}

// --- Lesson endpoints ---

// CreateLesson handles POST /courses/:id/lessons
func (h *EducationHandler) CreateLesson(c *gin.Context) {
	userID, ok := GetUserIDUUID(c)
	if !ok {
		return
	}

	courseID, err := uuid.Parse(c.Param("id"))
	if err != nil {
		RespondWithAppError(c, apperrors.NewValidationError("Invalid course ID"))
		return
	}

	var req education.CreateLessonRequest
	if err := c.ShouldBindJSON(&req); err != nil {
		RespondWithAppError(c, apperrors.NewValidationError("Invalid request: title is required"))
		return
	}

	lesson, err := h.service.CreateLesson(c.Request.Context(), userID, courseID, req)
	if err != nil {
		h.handleCourseError(c, err)
		return
	}

	RespondSuccess(c, http.StatusCreated, lesson)
}

// UpdateLesson handles PUT /courses/:id/lessons/:lesson_id
func (h *EducationHandler) UpdateLesson(c *gin.Context) {
	userID, ok := GetUserIDUUID(c)
	if !ok {
		return
	}

	courseID, err := uuid.Parse(c.Param("id"))
	if err != nil {
		RespondWithAppError(c, apperrors.NewValidationError("Invalid course ID"))
		return
	}

	lessonID, err := uuid.Parse(c.Param("lesson_id"))
	if err != nil {
		RespondWithAppError(c, apperrors.NewValidationError("Invalid lesson ID"))
		return
	}

	var req education.UpdateLessonRequest
	if err := c.ShouldBindJSON(&req); err != nil {
		RespondWithAppError(c, apperrors.NewValidationError("Invalid request body"))
		return
	}

	lesson, err := h.service.UpdateLesson(c.Request.Context(), userID, courseID, lessonID, req)
	if err != nil {
		h.handleCourseError(c, err)
		return
	}

	RespondSuccess(c, http.StatusOK, lesson)
}

// DeleteLesson handles DELETE /courses/:id/lessons/:lesson_id
func (h *EducationHandler) DeleteLesson(c *gin.Context) {
	userID, ok := GetUserIDUUID(c)
	if !ok {
		return
	}

	courseID, err := uuid.Parse(c.Param("id"))
	if err != nil {
		RespondWithAppError(c, apperrors.NewValidationError("Invalid course ID"))
		return
	}

	lessonID, err := uuid.Parse(c.Param("lesson_id"))
	if err != nil {
		RespondWithAppError(c, apperrors.NewValidationError("Invalid lesson ID"))
		return
	}

	if err := h.service.DeleteLesson(c.Request.Context(), userID, courseID, lessonID); err != nil {
		h.handleCourseError(c, err)
		return
	}

	RespondSuccess(c, http.StatusOK, gin.H{"message": "Lesson deleted"})
}

// GetCourseLessons handles GET /courses/:id/lessons
func (h *EducationHandler) GetCourseLessons(c *gin.Context) {
	courseID, err := uuid.Parse(c.Param("id"))
	if err != nil {
		RespondWithAppError(c, apperrors.NewValidationError("Invalid course ID"))
		return
	}

	lessons, err := h.service.GetCourseLessons(c.Request.Context(), courseID)
	if err != nil {
		RespondWithAppError(c, apperrors.NewInternalErrorWrap("Failed to get lessons", err))
		return
	}

	RespondSuccess(c, http.StatusOK, gin.H{"lessons": lessons})
}

// ReorderLessons handles POST /courses/:id/lessons/reorder
func (h *EducationHandler) ReorderLessons(c *gin.Context) {
	userID, ok := GetUserIDUUID(c)
	if !ok {
		return
	}

	courseID, err := uuid.Parse(c.Param("id"))
	if err != nil {
		RespondWithAppError(c, apperrors.NewValidationError("Invalid course ID"))
		return
	}

	var req education.ReorderLessonsRequest
	if err := c.ShouldBindJSON(&req); err != nil {
		RespondWithAppError(c, apperrors.NewValidationError("Invalid request: lesson_ids is required"))
		return
	}

	if err := h.service.ReorderLessons(c.Request.Context(), userID, courseID, req); err != nil {
		h.handleCourseError(c, err)
		return
	}

	RespondSuccess(c, http.StatusOK, gin.H{"message": "Lessons reordered"})
}

// --- Enrollment endpoints ---

// Enroll handles POST /courses/:id/enroll
func (h *EducationHandler) Enroll(c *gin.Context) {
	userID, ok := GetUserIDUUID(c)
	if !ok {
		return
	}

	courseID, err := uuid.Parse(c.Param("id"))
	if err != nil {
		RespondWithAppError(c, apperrors.NewValidationError("Invalid course ID"))
		return
	}

	var req education.EnrollRequest
	if err := c.ShouldBindJSON(&req); err != nil {
		// Allow empty body for free courses
		req = education.EnrollRequest{}
	}

	enrollment, err := h.service.Enroll(c.Request.Context(), userID, courseID, req)
	if err != nil {
		switch {
		case errors.Is(err, education.ErrCourseNotFound):
			RespondWithAppError(c, apperrors.NewNotFoundError("Course"))
		case errors.Is(err, education.ErrCourseNotPublished):
			RespondWithAppError(c, apperrors.NewValidationError("Course is not published"))
		case errors.Is(err, education.ErrAlreadyEnrolled):
			RespondWithAppError(c, apperrors.NewValidationError("Already enrolled in this course"))
		case errors.Is(err, education.ErrCannotEnrollOwnCourse):
			RespondWithAppError(c, apperrors.NewValidationError("Cannot enroll in your own course"))
		default:
			RespondWithAppError(c, apperrors.NewInternalErrorWrap("Failed to enroll", err))
		}
		return
	}

	RespondSuccess(c, http.StatusCreated, enrollment)
}

// GetMyEnrollments handles GET /enrollments
func (h *EducationHandler) GetMyEnrollments(c *gin.Context) {
	userID, ok := GetUserIDUUID(c)
	if !ok {
		return
	}

	limit, _ := strconv.Atoi(c.DefaultQuery("limit", "20"))
	limit = clampLimit(limit) // SECURITY(MEDIUM-004)
	offset, _ := strconv.Atoi(c.DefaultQuery("offset", "0"))

	enrollments, total, err := h.service.GetUserEnrollments(c.Request.Context(), userID, limit, offset)
	if err != nil {
		RespondWithAppError(c, apperrors.NewInternalErrorWrap("Failed to get enrollments", err))
		return
	}

	page := (offset / max(limit, 1)) + 1
	totalPages := int((total + int64(limit) - 1) / int64(limit))

	RespondSuccess(c, http.StatusOK, gin.H{
		"data": enrollments,
		"pagination": gin.H{
			"page":        page,
			"limit":       limit,
			"total":       total,
			"total_pages": totalPages,
		},
	})
}

// --- Progress endpoints ---

// UpdateProgress handles POST /lessons/:lesson_id/progress
func (h *EducationHandler) UpdateProgress(c *gin.Context) {
	userID, ok := GetUserIDUUID(c)
	if !ok {
		return
	}

	lessonID, err := uuid.Parse(c.Param("lesson_id"))
	if err != nil {
		RespondWithAppError(c, apperrors.NewValidationError("Invalid lesson ID"))
		return
	}

	var req education.UpdateProgressRequest
	if err := c.ShouldBindJSON(&req); err != nil {
		RespondWithAppError(c, apperrors.NewValidationError("Invalid request body"))
		return
	}

	progress, err := h.service.UpdateProgress(c.Request.Context(), userID, lessonID, req)
	if err != nil {
		switch {
		case errors.Is(err, education.ErrLessonNotFound):
			RespondWithAppError(c, apperrors.NewNotFoundError("Lesson"))
		case errors.Is(err, education.ErrNotEnrolled):
			RespondWithAppError(c, apperrors.NewForbiddenError("Not enrolled in this course"))
		default:
			RespondWithAppError(c, apperrors.NewInternalErrorWrap("Failed to update progress", err))
		}
		return
	}

	RespondSuccess(c, http.StatusOK, progress)
}

// GetCourseProgress handles GET /courses/:id/progress
func (h *EducationHandler) GetCourseProgress(c *gin.Context) {
	userID, ok := GetUserIDUUID(c)
	if !ok {
		return
	}

	courseID, err := uuid.Parse(c.Param("id"))
	if err != nil {
		RespondWithAppError(c, apperrors.NewValidationError("Invalid course ID"))
		return
	}

	progress, err := h.service.GetCourseProgress(c.Request.Context(), userID, courseID)
	if err != nil {
		if errors.Is(err, education.ErrNotEnrolled) {
			RespondWithAppError(c, apperrors.NewForbiddenError("Not enrolled in this course"))
			return
		}
		RespondWithAppError(c, apperrors.NewInternalErrorWrap("Failed to get progress", err))
		return
	}

	RespondSuccess(c, http.StatusOK, gin.H{"progress": progress})
}

// --- Certificate endpoints ---

// IssueCertificate handles POST /courses/:id/certificate
func (h *EducationHandler) IssueCertificate(c *gin.Context) {
	userID, ok := GetUserIDUUID(c)
	if !ok {
		return
	}

	courseID, err := uuid.Parse(c.Param("id"))
	if err != nil {
		RespondWithAppError(c, apperrors.NewValidationError("Invalid course ID"))
		return
	}

	cert, err := h.service.IssueCertificate(c.Request.Context(), userID, courseID)
	if err != nil {
		switch {
		case errors.Is(err, education.ErrNotEnrolled):
			RespondWithAppError(c, apperrors.NewForbiddenError("Not enrolled in this course"))
		case errors.Is(err, education.ErrCourseNotCompleted):
			RespondWithAppError(c, apperrors.NewValidationError("Course is not fully completed"))
		case errors.Is(err, education.ErrCertificateExists):
			RespondWithAppError(c, apperrors.NewValidationError("Certificate already issued"))
		default:
			RespondWithAppError(c, apperrors.NewInternalErrorWrap("Failed to issue certificate", err))
		}
		return
	}

	RespondSuccess(c, http.StatusCreated, cert)
}

// VerifyCertificate handles GET /certificates/:code
func (h *EducationHandler) VerifyCertificate(c *gin.Context) {
	code := c.Param("code")
	if code == "" {
		RespondWithAppError(c, apperrors.NewValidationError("Certificate code is required"))
		return
	}

	cert, err := h.service.GetCertificate(c.Request.Context(), code)
	if err != nil {
		if errors.Is(err, education.ErrCertificateNotFound) {
			RespondWithAppError(c, apperrors.NewNotFoundError("Certificate"))
			return
		}
		RespondWithAppError(c, apperrors.NewInternalErrorWrap("Failed to verify certificate", err))
		return
	}

	RespondSuccess(c, http.StatusOK, cert)
}

// GetMyCertificates handles GET /certificates
func (h *EducationHandler) GetMyCertificates(c *gin.Context) {
	userID, ok := GetUserIDUUID(c)
	if !ok {
		return
	}

	certs, err := h.service.GetUserCertificates(c.Request.Context(), userID)
	if err != nil {
		RespondWithAppError(c, apperrors.NewInternalErrorWrap("Failed to get certificates", err))
		return
	}

	RespondSuccess(c, http.StatusOK, gin.H{"certificates": certs})
}

// --- Review endpoints ---

// CreateReview handles POST /courses/:id/reviews
func (h *EducationHandler) CreateReview(c *gin.Context) {
	userID, ok := GetUserIDUUID(c)
	if !ok {
		return
	}

	courseID, err := uuid.Parse(c.Param("id"))
	if err != nil {
		RespondWithAppError(c, apperrors.NewValidationError("Invalid course ID"))
		return
	}

	var req education.CreateReviewRequest
	if err := c.ShouldBindJSON(&req); err != nil {
		RespondWithAppError(c, apperrors.NewValidationError("Invalid request: rating and content are required"))
		return
	}

	review, err := h.service.CreateReview(c.Request.Context(), userID, courseID, req)
	if err != nil {
		switch {
		case errors.Is(err, education.ErrNotEnrolled):
			RespondWithAppError(c, apperrors.NewForbiddenError("Must be enrolled to review"))
		case errors.Is(err, education.ErrReviewAlreadyExists):
			RespondWithAppError(c, apperrors.NewValidationError("Already reviewed this course"))
		case errors.Is(err, education.ErrInvalidRating):
			RespondWithAppError(c, apperrors.NewValidationError("Rating must be between 1 and 5"))
		default:
			RespondWithAppError(c, apperrors.NewInternalErrorWrap("Failed to create review", err))
		}
		return
	}

	RespondSuccess(c, http.StatusCreated, review)
}

// GetCourseReviews handles GET /courses/:id/reviews
func (h *EducationHandler) GetCourseReviews(c *gin.Context) {
	courseID, err := uuid.Parse(c.Param("id"))
	if err != nil {
		RespondWithAppError(c, apperrors.NewValidationError("Invalid course ID"))
		return
	}

	limit, _ := strconv.Atoi(c.DefaultQuery("limit", "20"))
	limit = clampLimit(limit) // SECURITY(MEDIUM-004)
	offset, _ := strconv.Atoi(c.DefaultQuery("offset", "0"))

	reviews, total, err := h.service.GetCourseReviews(c.Request.Context(), courseID, limit, offset)
	if err != nil {
		RespondWithAppError(c, apperrors.NewInternalErrorWrap("Failed to get reviews", err))
		return
	}

	page := (offset / max(limit, 1)) + 1
	totalPages := int((total + int64(limit) - 1) / int64(limit))

	RespondSuccess(c, http.StatusOK, gin.H{
		"data": reviews,
		"pagination": gin.H{
			"page":        page,
			"limit":       limit,
			"total":       total,
			"total_pages": totalPages,
		},
	})
}

// UploadLessonVideo handles POST /courses/:id/lessons/:lesson_id/video
func (h *EducationHandler) UploadLessonVideo(c *gin.Context) {
	userID, ok := GetUserIDUUID(c)
	if !ok {
		return
	}

	courseID, err := uuid.Parse(c.Param("id"))
	if err != nil {
		RespondWithAppError(c, apperrors.NewValidationError("Invalid course ID"))
		return
	}

	lessonID, err := uuid.Parse(c.Param("lesson_id"))
	if err != nil {
		RespondWithAppError(c, apperrors.NewValidationError("Invalid lesson ID"))
		return
	}

	fileHeader, err := c.FormFile("video")
	if err != nil {
		RespondWithAppError(c, apperrors.NewValidationError("No video file provided"))
		return
	}

	// Validate file size (max 500MB)
	const maxVideoSize = 500 * 1024 * 1024
	if fileHeader.Size > maxVideoSize {
		RespondWithAppError(c, apperrors.NewValidationError("Video file too large (max 500MB)"))
		return
	}

	// Validate content type
	contentType := fileHeader.Header.Get("Content-Type")
	allowedTypes := map[string]bool{
		"video/mp4":  true,
		"video/webm": true,
		"video/ogg":  true,
		"video/avi":  true,
	}
	if !allowedTypes[contentType] {
		RespondWithAppError(c, apperrors.NewValidationError("Unsupported video format. Accepted: mp4, webm, ogg, avi"))
		return
	}

	// Save file to upload directory
	uploadDir := "/tmp/veza-uploads/videos"
	filename := lessonID.String() + "_" + fileHeader.Filename
	savePath := uploadDir + "/" + filename

	if err := c.SaveUploadedFile(fileHeader, savePath); err != nil {
		h.logger.Error("Failed to save video file",
			zap.Error(err),
			zap.String("lesson_id", lessonID.String()),
		)
		RespondWithAppError(c, apperrors.NewInternalErrorWrap("Failed to save video", err))
		return
	}

	// Update lesson with video path (triggers transcoding pipeline)
	lesson, err := h.service.SetLessonVideoPath(c.Request.Context(), userID, courseID, lessonID, savePath, 0)
	if err != nil {
		h.handleCourseError(c, err)
		return
	}

	h.logger.Info("Lesson video uploaded",
		zap.String("lesson_id", lessonID.String()),
		zap.String("course_id", courseID.String()),
		zap.Int64("file_size", fileHeader.Size),
	)

	RespondSuccess(c, http.StatusOK, lesson)
}

// handleCourseError maps common course errors to HTTP responses
func (h *EducationHandler) handleCourseError(c *gin.Context, err error) {
	switch {
	case errors.Is(err, education.ErrCourseNotFound):
		RespondWithAppError(c, apperrors.NewNotFoundError("Course"))
	case errors.Is(err, education.ErrLessonNotFound):
		RespondWithAppError(c, apperrors.NewNotFoundError("Lesson"))
	case errors.Is(err, education.ErrNotCourseOwner):
		RespondWithAppError(c, apperrors.NewForbiddenError("You are not the owner of this course"))
	default:
		RespondWithAppError(c, apperrors.NewInternalErrorWrap("Operation failed", err))
	}
}