/**
 * @author n1474335 [n1474335@gmail.com]
 * @copyright Crown Copyright 2016
 * @license Apache-2.0
 */

import Operation from "../Operation.mjs";
import Utils from "../Utils.mjs";
import * as JsDiff from "diff";
import OperationError from "../errors/OperationError.mjs";

/**
 * Diff operation
 */
class Diff extends Operation {

    /**
     * Diff constructor
     */
    constructor() {
        super();

        this.name = "Diff";
        this.module = "Diff";
        this.description = "Compares two inputs (separated by the specified delimiter) and highlights the differences between them.";
        this.infoURL = "https://wikipedia.org/wiki/File_comparison";
        this.inputType = "string";
        this.outputType = "html";
        this.args = [
            {
                "name": "Sample delimiter",
                "type": "binaryString",
                "value": "\\n\\n"
            },
            {
                "name": "Diff by",
                "type": "option",
                "value": ["Character", "Word", "Line", "Sentence", "CSS", "JSON"]
            },
            {
                "name": "Show added",
                "type": "boolean",
                "value": true
            },
            {
                "name": "Show removed",
                "type": "boolean",
                "value": true
            },
            {
                "name": "Show subtraction",
                "type": "boolean",
                "value": false
            },
            {
                "name": "Ignore whitespace",
                "type": "boolean",
                "value": false,
                "hint": "Relevant for word and line"
            },
            {
                "name": "Show +/- notation",
                "hint": "Works only in Line diff mode.",
                "type": "boolean",
                "value": false
            }
        ];
    }

    /**
     * @param {string} input
     * @param {Object[]} args
     * @returns {html}
     */
    run(input, args) {
        const [
                sampleDelim,
                diffBy,
                showAdded,
                showRemoved,
                showSubtraction,
                ignoreWhitespace,
                showNotation
            ] = args,
            samples = input.split(sampleDelim);
        let output = "",
            diff;

        // Node and Webpack load modules slightly differently
        const jsdiff = JsDiff.default ? JsDiff.default : JsDiff;

        if (!samples || samples.length !== 2) {
            throw new OperationError("Incorrect number of samples, perhaps you need to modify the sample delimiter or add more samples?");
        }

        // +/- notation only works properly with Line diff mode
        // For other modes, it falls back to HTML format and this option is ignored (see hint).
        const useNotation = showNotation && diffBy === "Line";

        if (useNotation) {
            const patch = jsdiff.createTwoFilesPatch("original", "modified", samples[0], samples[1], "", "", {
                context: Infinity,
                ignoreWhitespace: ignoreWhitespace,
            });

            const lines = patch.split("\n");
            for (let i = 0; i < lines.length; i++) {
                const line = lines[i];
                if (line.startsWith("@@")) {
                    if (showSubtraction) output += line + "\n";
                } else if (line.startsWith("+") && !line.startsWith("+++")) {
                    if (showAdded) output += line + "\n";
                } else if (line.startsWith("-") && !line.startsWith("---")) {
                    if (showRemoved) output += line + "\n";
                } else if (line.startsWith("===") || line.startsWith("---") || line.startsWith("+++") || line.startsWith("\\")) {
                    continue;
                } else if (line.length > 0 && !showSubtraction) {
                    output += line.substring(1) + "\n";
                }
            }
            return output.slice(0, -1);
        }

        switch (diffBy) {
            case "Character":
                diff = jsdiff.diffChars(samples[0], samples[1]);
                break;
            case "Word":
                if (ignoreWhitespace) {
                    diff = jsdiff.diffWords(samples[0], samples[1]);
                } else {
                    diff = jsdiff.diffWordsWithSpace(samples[0], samples[1]);
                }
                break;
            case "Line":
                if (ignoreWhitespace) {
                    diff = jsdiff.diffTrimmedLines(samples[0], samples[1]);
                } else {
                    diff = jsdiff.diffLines(samples[0], samples[1]);
                }
                break;
            case "Sentence":
                diff = jsdiff.diffSentences(samples[0], samples[1]);
                break;
            case "CSS":
                diff = jsdiff.diffCss(samples[0], samples[1]);
                break;
            case "JSON":
                diff = jsdiff.diffJson(samples[0], samples[1]);
                break;
            default:
                throw new OperationError("Invalid 'Diff by' option.");
        }

        for (let i = 0; i < diff.length; i++) {
            if (diff[i].added) {
                if (showAdded) output += "<ins>" + Utils.escapeHtml(diff[i].value) + "</ins>";
            } else if (diff[i].removed) {
                if (showRemoved) output += "<del>" + Utils.escapeHtml(diff[i].value) + "</del>";
            } else if (!showSubtraction) {
                output += Utils.escapeHtml(diff[i].value);
            }
        }

        return output;
    }

}

export default Diff;