import { prisma } from '../config/database';
import { Prisma } from '@prisma/client';
import { config } from '../config';
import { logger } from '../config/logger';
import { UnauthorizedError, ValidationError, ForbiddenError, NotFoundError } from '../middleware/errorHandler';
import jwt from 'jsonwebtoken';
import { uploadFile, deleteFile, getPresignedUrl } from '../config/minio';
import {
    CreateCourseInput,
    UpdateCourseInput,
    createCourseResponse,
    GetMyCourseResponse,
    ListMyCourseResponse,
    addinstructorCourse,
    addinstructorCourseResponse,
    removeinstructorCourse,
    removeinstructorCourseResponse,
    setprimaryCourseInstructor,
    setprimaryCourseInstructorResponse,
    submitCourseResponse,
    listinstructorCourseResponse,
    sendCourseForReview,
    getmyCourse,
    listinstructorCourse,
} from "../types/CoursesInstructor.types";

export class CoursesInstructorService {
    static async createCourse(courseData: CreateCourseInput, userId: number, thumbnailFile?: Express.Multer.File): Promise<createCourseResponse> {
        try {
            let thumbnailUrl: string | undefined;

            // Upload thumbnail to MinIO if provided
            if (thumbnailFile) {
                const timestamp = Date.now();
                const uniqueId = Math.random().toString(36).substring(2, 15);
                const extension = thumbnailFile.originalname.split('.').pop() || 'jpg';
                const safeFilename = `${timestamp}-${uniqueId}.${extension}`;
                const filePath = `courses/thumbnails/${safeFilename}`;

                await uploadFile(filePath, thumbnailFile.buffer, thumbnailFile.mimetype || 'image/jpeg');
                thumbnailUrl = filePath;
            }

            // Use transaction to create course and instructor together
            const result = await prisma.$transaction(async (tx) => {
                // Create the course
                const courseCreated = await tx.course.create({
                    data: {
                        category_id: courseData.category_id,
                        title: courseData.title,
                        slug: courseData.slug,
                        description: courseData.description,
                        thumbnail_url: thumbnailUrl,
                        price: courseData.price || 0,
                        is_free: courseData.is_free ?? false,
                        have_certificate: courseData.have_certificate ?? false,
                        created_by: userId,
                        status: 'DRAFT'
                    }
                });

                // Add creator as primary instructor
                await tx.courseInstructor.create({
                    data: {
                        course_id: courseCreated.id,
                        user_id: userId,
                        is_primary: true,
                    }
                });

                return courseCreated;
            });

            return {
                code: 201,
                message: 'Course created successfully',
                data: result
            };
        } catch (error) {
            logger.error('Failed to create course', { error });
            throw error;
        }
    }

    static async listMyCourses(token: string): Promise<ListMyCourseResponse> {
        try {
            const decoded = jwt.verify(token, config.jwt.secret) as { id: number; type: string };
            const courseInstructors = await prisma.courseInstructor.findMany({
                where: {
                    user_id: decoded.id
                },
                include: {
                    course: true
                }
            });

            const courses = await Promise.all(
                courseInstructors.map(async (ci) => {
                    let thumbnail_presigned_url: string | null = null;
                    if (ci.course.thumbnail_url) {
                        try {
                            thumbnail_presigned_url = await getPresignedUrl(ci.course.thumbnail_url, 3600);
                        } catch (err) {
                            logger.warn(`Failed to generate presigned URL for thumbnail: ${err}`);
                        }
                    }
                    return {
                        ...ci.course,
                        thumbnail_url: thumbnail_presigned_url,
                    };
                })
            );

            return {
                code: 200,
                message: 'Courses retrieved successfully',
                data: courses,
                total: courses.length
            };
        } catch (error) {
            logger.error('Failed to retrieve courses', { error });
            throw error;
        }
    }

    static async getmyCourse(getmyCourse: getmyCourse): Promise<GetMyCourseResponse> {
        try {
            const decoded = jwt.verify(getmyCourse.token, config.jwt.secret) as { id: number; type: string };

            // Check if user is instructor of this course
            const courseInstructor = await prisma.courseInstructor.findFirst({
                where: {
                    user_id: decoded.id,
                    course_id: getmyCourse.course_id
                },
                include: {
                    course: {
                        include: {
                            chapters: {
                                include: {
                                    lessons: {
                                        include: {
                                            attachments: true,
                                            progress: true,
                                            quiz: true
                                        }
                                    }
                                }
                            }
                        }
                    }
                }
            });

            if (!courseInstructor) {
                throw new ForbiddenError('You are not an instructor of this course');
            }

            // Generate presigned URL for thumbnail
            let thumbnail_presigned_url: string | null = null;
            if (courseInstructor.course.thumbnail_url) {
                try {
                    thumbnail_presigned_url = await getPresignedUrl(courseInstructor.course.thumbnail_url, 3600);
                } catch (err) {
                    logger.warn(`Failed to generate presigned URL for thumbnail: ${err}`);
                }
            }

            return {
                code: 200,
                message: 'Course retrieved successfully',
                data: {
                    ...courseInstructor.course,
                    thumbnail_url: thumbnail_presigned_url,
                }
            };
        } catch (error) {
            logger.error('Failed to retrieve course', { error });
            throw error;
        }
    }

    static async updateCourse(token: string, courseId: number, courseData: UpdateCourseInput): Promise<createCourseResponse> {
        try {
            const courseInstructorId = await this.validateCourseInstructor(token, courseId);

            const course = await prisma.course.update({
                where: {
                    id: courseId
                },
                data: courseData
            });

            // Generate presigned URL for thumbnail
            let thumbnail_presigned_url: string | null = null;
            if (course.thumbnail_url) {
                try {
                    thumbnail_presigned_url = await getPresignedUrl(course.thumbnail_url, 3600);
                } catch (err) {
                    logger.warn(`Failed to generate presigned URL for thumbnail: ${err}`);
                }
            }

            return {
                code: 200,
                message: 'Course updated successfully',
                data: {
                    ...course,
                    thumbnail_url: thumbnail_presigned_url,
                }
            };
        } catch (error) {
            logger.error('Failed to update course', { error });
            throw error;
        }
    }

    static async deleteCourse(token: string, courseId: number): Promise<createCourseResponse> {
        try {
            const courseInstructorId = await this.validateCourseInstructor(token, courseId);
            if (!courseInstructorId.is_primary) {
                throw new ForbiddenError('You have no permission to delete this course');
            }

            const course = await prisma.course.delete({
                where: {
                    id: courseId
                }
            });
            return {
                code: 200,
                message: 'Course deleted successfully',
                data: course
            };
        } catch (error) {
            logger.error('Failed to delete course', { error });
            throw error;
        }
    }

    static async sendCourseForReview(sendCourseForReview: sendCourseForReview): Promise<submitCourseResponse> {
        try {
            const decoded = jwt.verify(sendCourseForReview.token, config.jwt.secret) as { id: number; type: string };
            await prisma.courseApproval.create({
                data: {
                    course_id: sendCourseForReview.course_id,
                    submitted_by: decoded.id,
                }
            });
            await prisma.course.update({
                where: {
                    id: sendCourseForReview.course_id
                },
                data: {
                    status: 'PENDING'
                }
            });
            return {
                code: 200,
                message: 'Course sent for review successfully',
            };
        } catch (error) {
            logger.error('Failed to send course for review', { error });
            throw error;
        }
    }

    static async getCourseApprovals(token: string, courseId: number): Promise<{
        code: number;
        message: string;
        data: any[];
        total: number;
    }> {
        try {
            const decoded = jwt.verify(token, config.jwt.secret) as { id: number; type: string };

            // Validate instructor access
            await this.validateCourseInstructor(token, courseId);

            const approvals = await prisma.courseApproval.findMany({
                where: { course_id: courseId },
                orderBy: { created_at: 'desc' },
                include: {
                    submitter: {
                        select: { id: true, username: true, email: true }
                    },
                    reviewer: {
                        select: { id: true, username: true, email: true }
                    }
                }
            });

            return {
                code: 200,
                message: 'Course approvals retrieved successfully',
                data: approvals,
                total: approvals.length,
            };
        } catch (error) {
            logger.error('Failed to retrieve course approvals', { error });
            throw error;
        }
    }



    static async addInstructorToCourse(addinstructorCourse: addinstructorCourse): Promise<addinstructorCourseResponse> {
        try {
            const decoded = jwt.verify(addinstructorCourse.token, config.jwt.secret) as { id: number; type: string };
            await prisma.courseInstructor.create({
                data: {
                    course_id: addinstructorCourse.course_id,
                    user_id: decoded.id,
                }
            });
            return {
                code: 200,
                message: 'Instructor added to course successfully',
            };
        } catch (error) {
            logger.error('Failed to add instructor to course', { error });
            throw error;
        }
    }

    static async removeInstructorFromCourse(removeinstructorCourse: removeinstructorCourse): Promise<removeinstructorCourseResponse> {
        try {
            const decoded = jwt.verify(removeinstructorCourse.token, config.jwt.secret) as { id: number; type: string };
            await prisma.courseInstructor.delete({
                where: {
                    course_id_user_id: {
                        course_id: removeinstructorCourse.course_id,
                        user_id: removeinstructorCourse.user_id,
                    },
                }
            });
            return {
                code: 200,
                message: 'Instructor removed from course successfully',
            };
        } catch (error) {
            logger.error('Failed to remove instructor from course', { error });
            throw error;
        }
    }

    static async listInstructorsOfCourse(listinstructorCourse: listinstructorCourse): Promise<listinstructorCourseResponse> {
        try {
            const decoded = jwt.verify(listinstructorCourse.token, config.jwt.secret) as { id: number; type: string };
            const courseInstructors = await prisma.courseInstructor.findMany({
                where: {
                    course_id: listinstructorCourse.course_id,
                },
                include: {
                    user: true,
                }
            });
            return {
                code: 200,
                message: 'Instructors retrieved successfully',
                data: courseInstructors,
            };
        } catch (error) {
            logger.error('Failed to retrieve instructors of course', { error });
            throw error;
        }
    }

    static async setPrimaryInstructor(setprimaryCourseInstructor: setprimaryCourseInstructor): Promise<setprimaryCourseInstructorResponse> {
        try {
            const decoded = jwt.verify(setprimaryCourseInstructor.token, config.jwt.secret) as { id: number; type: string };
            await prisma.courseInstructor.update({
                where: {
                    course_id_user_id: {
                        course_id: setprimaryCourseInstructor.course_id,
                        user_id: setprimaryCourseInstructor.user_id,
                    },
                },
                data: {
                    is_primary: true,
                }
            });
            return {
                code: 200,
                message: 'Primary instructor set successfully',
            };
        } catch (error) {
            logger.error('Failed to set primary instructor', { error });
            throw error;
        }
    }

    static async validateCourseInstructor(token: string, courseId: number): Promise<{ user_id: number; is_primary: boolean }> {
        const decoded = jwt.verify(token, config.jwt.secret) as { id: number; type: string };
        const courseInstructor = await prisma.courseInstructor.findFirst({
            where: {
                user_id: decoded.id,
                course_id: courseId
            }
        });

        if (!courseInstructor) {
            throw new ForbiddenError('You are not an instructor of this course');
        } else return { user_id: courseInstructor.user_id, is_primary: courseInstructor.is_primary };
    }

    static async validateCourseStatus(courseId: number): Promise<void> {
        const course = await prisma.course.findUnique({ where: { id: courseId } });
        if (!course) {
            throw new NotFoundError('Course not found');
        }
        if (course.status === 'APPROVED' || course.status === 'PENDING') {
            throw new ForbiddenError('Course is already approved Cannot Edit');
        }
    }
}