const PizZip = require('pizzip');
const Docxtemplater = require('docxtemplater');
const fs = require('fs');
const path = require('path');
const _ = require("lodash");

// The error object contains additional information when logged with JSON.stringify (it contains a properties object containing all suberrors).
function replaceErrors(key, value) {
    if (value instanceof Error) {
        return Object.getOwnPropertyNames(value).reduce(function (error, key) {
            error[key] = value[key];
            return error;
        }, {});
    }
    return value;
}

function errorHandler(error) {
    console.log(JSON.stringify({
        error: error
    }, replaceErrors));

    if (error.properties && error.properties.errors instanceof Array) {
        const errorMessages = error.properties.errors.map(function (error) {
            return error.properties.explanation;
        }).join("\n");
        console.log('errorMessages', errorMessages);
        // errorMessages is a humanly readable message looking like this :
        // 'The tag beginning with "foobar" is unopened'
    }
    throw error;
}

class InspectModule {
    constructor() {
        this.inspect = {};
    }
    set(obj) {
        if (obj.inspect) {
            this.inspect = _.merge({}, this.inspect, obj.inspect);
        }
    }
}

const getTags = function (postParsed) {
    return postParsed.filter(function (part) {
        return part.type === "placeholder";
    }).reduce(function (tags, part) {
        tags[part.value] = {};
        if (part.subparsed) {
            tags[part.value] = getTags(part.subparsed);
        }
        return tags;
    }, {});
}

module.exports = function (templateInfo, fileName) {
    return new Promise((resolve, reject) => {

        //check empty fields
        for (const key in templateInfo) {
            if (!templateInfo[key]) {
                throw ({
                    eCode: 412,
                    eText: 'هیچ یک از فیلدها نباید خالی باشند'
                })
            }
        }

        let content = fs.readFileSync(path.resolve(__dirname, `../template/${fileName}`), 'binary');
        let zip = new PizZip(content);
        let doc;
        let inspectModule = new InspectModule();

        try {
            doc = new Docxtemplater(zip, {
                modules: [inspectModule]
            });
        } catch (error) {

            errorHandler(error);
        }

        let postParsed = inspectModule.inspect.postparsed;
        let placeholders = Object.keys(getTags(postParsed))
        let templateInfoKeys = Object.keys(templateInfo)

        //compare template placeholders and received fields from client(templateInfo)
        for (let i = 0; i < placeholders.length; i++) {
            if (!templateInfoKeys.includes(placeholders[i])) {
                throw ({
                    eCode: 400,
                    eText: 'اطلاعات وارد شده ناقص است'
                })
            };
        };

        doc.setData(templateInfo);

        try {
            doc.render()
        } catch (error) {
            errorHandler(error);
        }

        let buf = doc.getZip().generate({
            type: 'nodebuffer'
        });
        fs.writeFileSync(path.resolve(__dirname, `../public/files/${templateInfo.firstName}-${templateInfo.lastName}-${fileName}`), buf);
        resolve(`http://localhost:3000/users/download/${templateInfo.firstName}-${templateInfo.lastName}-${fileName}`)

            .catch(err => {
                reject({
                    eCode: 500,
                    eText: err
                })
            })
    })

}