'use strict';

const config = require('config');
const dateFns = require('date-fns');

const extensions = {
    'image/jpeg': '.jpg',
    'image/gif': '.gif',
    'video/mp4': '.mp4',
    'video/webm': '.webm'
};

function interpolate(path, post, item) {
    const dateFormat = config.patterns.dateformat || 'YYYYMMDD';

    const vars = {
        $postId: post.id,
        $postTitle: post.title,
        $postUser: post.user,
        $postDate: dateFns.format(post.datetime, dateFormat),
        $postIndex: post.index + config.patterns.indexOffset
    };

    if(post.content.album) {
        Object.assign(vars, {
            $albumId: post.content.album.id,
            $albumTitle: post.content.album.title,
            $albumDescription: post.content.album.description,
            $albumDate: dateFns.format(post.content.album.datetime, dateFormat)
        });
    }

    if(item) {
        Object.assign(vars, {
            $itemId: item.id,
            $itemTitle: item.title,
            $itemDescription: item.description,
            $itemDate: dateFns.format(item.datetime, dateFormat),
            $itemIndex: item.index + config.patterns.indexOffset,
            $ext: extensions[item.type]
        });
    }

    return Object.entries(vars).reduce((acc, [key, value], index) =>  {
        // strip slashes for filesystem compatability
        value = (value || '').toString().replace(/\//g, config.patterns.slashSubstitute);

        return acc.replace(key, value);
    }, path);
};

module.exports = interpolate;