'use strict';
const {promisify} = require('util');
const fs = require('fs');
const path = require('path');
const fastGlob = require('fast-glob');
const gitIgnore = require('ignore');
const slash = require('slash');

const DEFAULT_IGNORE = [
    '**/node_modules/**',
    '**/flow-typed/**',
    '**/coverage/**',
    '**/.git'
];

const readFileP = promisify(fs.readFile);

const mapGitIgnorePatternTo = base => ignore => {
    if (ignore.startsWith('!')) {
        return '!' + path.posix.join(base, ignore.slice(1));
    }

    return path.posix.join(base, ignore);
};

const parseGitIgnore = (content, options) => {
    const base = slash(path.relative(options.cwd, path.dirname(options.fileName)));

    return content
        .split(/\r?\n/)
        .filter(Boolean)
        .filter(line => !line.startsWith('#'))
        .map(mapGitIgnorePatternTo(base));
};

const reduceIgnore = files => {
    const ignores = gitIgnore();
    for (const file of files) {
        ignores.add(parseGitIgnore(file.content, {
            cwd: file.cwd,
            fileName: file.filePath
        }));
    }

    return ignores;
};

const ensureAbsolutePathForCwd = (cwd, p) => {
    cwd = slash(cwd);
    if (path.isAbsolute(p)) {
        if (slash(p).startsWith(cwd)) {
            return p;
        }

        throw new Error(`Path ${p} is not in cwd ${cwd}`);
    }

    return path.join(cwd, p);
};

const getIsIgnoredPredecate = (ignores, cwd) => {
    return p => ignores.ignores(slash(path.relative(cwd, ensureAbsolutePathForCwd(cwd, p.path || p))));
};

const getFile = async (file, cwd) => {
    const filePath = path.join(cwd, file);
    const content = await readFileP(filePath, 'utf8');

    return {
        cwd,
        filePath,
        content
    };
};

const getFileSync = (file, cwd) => {
    const filePath = path.join(cwd, file);
    const content = fs.readFileSync(filePath, 'utf8');

    return {
        cwd,
        filePath,
        content
    };
};

const normalizeOptions = ({
    ignore = [],
    cwd = slash(process.cwd())
} = {}) => {
    return {ignore, cwd};
};

module.exports = async options => {
    options = normalizeOptions(options);

    const paths = await fastGlob('**/.gitignore', {
        ignore: DEFAULT_IGNORE.concat(options.ignore),
        cwd: options.cwd
    });

    const files = await Promise.all(paths.map(file => getFile(file, options.cwd)));
    const ignores = reduceIgnore(files);

    return getIsIgnoredPredecate(ignores, options.cwd);
};

module.exports.sync = options => {
    options = normalizeOptions(options);

    const paths = fastGlob.sync('**/.gitignore', {
        ignore: DEFAULT_IGNORE.concat(options.ignore),
        cwd: options.cwd
    });

    const files = paths.map(file => getFileSync(file, options.cwd));
    const ignores = reduceIgnore(files);

    return getIsIgnoredPredecate(ignores, options.cwd);
};