import { Injectable, InternalServerErrorException, Logger } from '@nestjs/common';
import fs from 'fs';
import path from 'path';
import pug from 'pug';
import { StartUpException } from '../../exceptions/StartUpException';
import { SettingsService } from '../settings/settings.service';
import {
    AttendanceAttributes,
    CredentialsAttributes,
    MailAttribtutes,
    ScheinexamAttributes,
    ScheinstatusAttributes,
    Template,
} from './template.types';

@Injectable()
export class TemplateService {
    private readonly logger = new Logger(TemplateService.name);
    private readonly TEMPLATE_FILES = {
        attendance: 'attendance.pug',
        credentials: 'credentials.pug',
        mail: 'mail.pug',
        scheinexam: 'scheinexam.pug',
        scheinstatus: 'scheinstatus.pug',
    };

    constructor(private readonly settings: SettingsService) {}

    getAttendanceTemplate(): Template<AttendanceAttributes> {
        return this.getTemplate(this.TEMPLATE_FILES.attendance);
    }

    getCredentialsTemplate(): Template<CredentialsAttributes> {
        return this.getTemplate(this.TEMPLATE_FILES.credentials);
    }

    getMailTemplate(): Template<MailAttribtutes> {
        return this.getTemplate(this.TEMPLATE_FILES.mail);
    }

    getScheinexamTemplate(): Template<ScheinexamAttributes> {
        return this.getTemplate(this.TEMPLATE_FILES.scheinexam);
    }

    getScheinstatusTemplate(): Template<ScheinstatusAttributes> {
        return this.getTemplate(this.TEMPLATE_FILES.scheinstatus);
    }

    checkAllTemplatesPresent(): void {
        const notExisting: string[] = [];

        for (const [, value] of Object.entries(this.TEMPLATE_FILES)) {
            const filePath = this.getPathToTemplateFile(value);
            try {
                fs.accessSync(filePath);

                this.logger.log(`Template file '${value}' found.`);
            } catch {
                notExisting.push(filePath);
            }
        }

        if (notExisting.length > 0) {
            throw new StartUpException(
                `The following template files could not be found: \n\t- ${notExisting.join(
                    '\n\t- '
                )}`
            );
        }
    }

    private getTemplate(file: string): pug.compileTemplate {
        const filePath = this.getPathToTemplateFile(file);

        this.assertFileExists(filePath);
        return pug.compileFile(filePath);
    }

    private getPathToTemplateFile(file: string): string {
        return path.join(this.settings.getConfigPath(), 'templates', file);
    }

    private assertFileExists(filePath: string) {
        try {
            fs.accessSync(filePath);
        } catch (err) {
            this.logger.error(`Could not find the template file at '${filePath}'`);
            throw new InternalServerErrorException(
                `Could not find the template file at '${filePath}'`
            );
        }
    }
}