#!/usr/bin/env node

/*
Copyright 2017 New Vector Ltd

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

/**
 * Regenerates the translations en_EN file by walking the source tree and
 * parsing each file with flow-parser. Emits a JSON file with the
 * translatable strings mapped to themselves in the order they appeared
 * in the files and grouped by the file they appeared in.
 *
 * Usage: node scripts/gen-i18n.js
 */
const fs = require('fs');
const path = require('path');

const walk = require('walk');

const flowParser = require('flow-parser');
const estreeWalker = require('estree-walker');

const TRANSLATIONS_FUNCS = ['_t', '_td', '_tJsx'];

const INPUT_TRANSLATIONS_FILE = 'src/i18n/strings/en_EN.json';
const OUTPUT_FILE = 'src/i18n/strings/en_EN.json';

// NB. The sync version of walk is broken for single files so we walk
// all of res rather than just res/home.html.
// https://git.daplie.com/Daplie/node-walk/merge_requests/1 fixes it,
// or if we get bored waiting for it to be merged, we could switch
// to a project that's actively maintained.
const SEARCH_PATHS = ['src', 'res'];

const FLOW_PARSER_OPTS = {
  esproposal_class_instance_fields: true,
  esproposal_class_static_fields: true,
  esproposal_decorators: true,
  esproposal_export_star_as: true,
  types: true,
};

function getObjectValue(obj, key) {
    for (const prop of obj.properties) {
        if (prop.key.type == 'Identifier' && prop.key.name == key) {
            return prop.value;
        }
    }
    return null;
}

function getTKey(arg) {
    if (arg.type == 'Literal') {
        return arg.value;
    } else if (arg.type == 'BinaryExpression' && arg.operator == '+') {
        return getTKey(arg.left) + getTKey(arg.right);
    } else if (arg.type == 'TemplateLiteral') {
        return arg.quasis.map((q) => {
            return q.value.raw;
        }).join('');
    }
    return null;
}

function getFormatStrings(str) {
    // Match anything that starts with %
    // We could make a regex that matched the full placeholder, but this
    // would just not match invalid placeholders and so wouldn't help us
    // detect the invalid ones.
    // Also note that for simplicity, this just matches a % character and then
    // anything up to the next % character (or a single %, or end of string).
    const formatStringRe = /%([^%]+|%|$)/g;
    const formatStrings = new Set();

    let match;
    while ( (match = formatStringRe.exec(str)) !== null ) {
        const placeholder = match[1]; // Minus the leading '%'
        if (placeholder === '%') continue; // Literal % is %%

        const placeholderMatch = placeholder.match(/^\((.*?)\)(.)/);
        if (placeholderMatch === null) {
            throw new Error("Invalid format specifier: '"+match[0]+"'");
        }
        if (placeholderMatch.length < 3) {
            throw new Error("Malformed format specifier");
        }
        const placeholderName = placeholderMatch[1];
        const placeholderFormat = placeholderMatch[2];

        if (placeholderFormat !== 's') {
            throw new Error(`'${placeholderFormat}' used as format character: you probably meant 's'`);
        }

        formatStrings.add(placeholderName);
    }

    return formatStrings;
}

function getTranslationsJs(file) {
    const tree = flowParser.parse(fs.readFileSync(file, { encoding: 'utf8' }), FLOW_PARSER_OPTS);

    const trs = new Set();

    estreeWalker.walk(tree, {
        enter: function(node, parent) {
            if (
                node.type == 'CallExpression' &&
                TRANSLATIONS_FUNCS.includes(node.callee.name)
            ) {
                const tKey = getTKey(node.arguments[0]);
                // This happens whenever we call _t with non-literals (ie. whenever we've
                // had to use a _td to compensate) so is expected.
                if (tKey === null) return;

                // check the format string against the args
                // We only check _t: _tJsx is much more complex and _td has no args
                if (node.callee.name === '_t') {
                    try {
                        const placeholders = getFormatStrings(tKey);
                        for (const placeholder of placeholders) {
                            if (node.arguments.length < 2) {
                                throw new Error(`Placeholder found ('${placeholder}') but no substitutions given`);
                            }
                            const value = getObjectValue(node.arguments[1], placeholder);
                            if (value === null) {
                                throw new Error(`No value found for placeholder '${placeholder}'`);
                            }
                        }
                    } catch (e) {
                        console.log();
                        console.error(`ERROR: ${file}:${node.loc.start.line} ${tKey}`);
                        process.exit(1);
                    }
                }

                let isPlural = false;
                if (node.arguments.length > 1 && node.arguments[1].type == 'ObjectExpression') {
                    const countVal = getObjectValue(node.arguments[1], 'count');
                    if (countVal) {
                        isPlural = true;
                    }
                }

                if (isPlural) {
                    trs.add(tKey + "|other");
                    const plurals = enPlurals[tKey];
                    if (plurals) {
                        for (const pluralType of Object.keys(plurals)) {
                            trs.add(tKey + "|" + pluralType);
                        }
                    }
                } else {
                    trs.add(tKey);
                }
            }
        }
    });

    return trs;
}

function getTranslationsOther(file) {
    const contents = fs.readFileSync(file, { encoding: 'utf8' });

    const trs = new Set();

    // Taken from riot-web src/components/structures/HomePage.js
    const translationsRegex = /_t\(['"]([\s\S]*?)['"]\)/mg;
    let matches;
    while (matches = translationsRegex.exec(contents)) {
        trs.add(matches[1]);
    }
    return trs;
}

// gather en_EN plural strings from the input translations file:
// the en_EN strings are all in the source with the exception of
// pluralised strings, which we need to pull in from elsewhere.
const inputTranslationsRaw = JSON.parse(fs.readFileSync(INPUT_TRANSLATIONS_FILE, { encoding: 'utf8' }));
const enPlurals = {};

for (const key of Object.keys(inputTranslationsRaw)) {
    const parts = key.split("|");
    if (parts.length > 1) {
        const plurals = enPlurals[parts[0]] || {};
        plurals[parts[1]] = inputTranslationsRaw[key];
        enPlurals[parts[0]] = plurals;
    }
}

const translatables = new Set();

const walkOpts = {
    listeners: {
        file: function(root, fileStats, next) {
            const fullPath = path.join(root, fileStats.name);

            let ltrs;
            if (fileStats.name.endsWith('.js')) {
                trs = getTranslationsJs(fullPath);
            } else if (fileStats.name.endsWith('.html')) {
                trs = getTranslationsOther(fullPath);
            } else {
                return;
            }
            console.log(`${fullPath} (${trs.size} strings)`);
            for (const tr of trs.values()) {
                translatables.add(tr);
            }
        },
    }
};

for (const path of SEARCH_PATHS) {
    if (fs.existsSync(path)) {
        walk.walkSync(path, walkOpts);
    }
}

const trObj = {};
for (const tr of translatables) {
    trObj[tr] = tr;
    if (tr.includes("|") && inputTranslationsRaw[tr]) {
        trObj[tr] = inputTranslationsRaw[tr];
    }
}

fs.writeFileSync(
    OUTPUT_FILE,
    JSON.stringify(trObj, translatables.values(), 4) + "\n"
);

console.log();
console.log(`Wrote ${translatables.size} strings to ${OUTPUT_FILE}`);