const fs = require('fs');
const path = require('path');
const remark = require('remark');
const languages = require('./languages')

const excludes = [
    'README.md',
    'CONTRIBUTING.md',
    'CODE_OF_CONDUCT.md',
    'SUMMARY.md'
]

// TODO!!
/**
 * Summary TBD.
 * 
 * Desciption TBD.
 * 
 * @param {Object}  listItem - a listItem in AST format defined by remark-parse
 * 
 * @return {Object} Returns an Object containing details about the piece of media Exact format TBD.
 */
let parseListItem = function(listItem){
    let entry = {};
    const link = listItem[0];
    entry.url = link.url;
    entry.title = link.children[0].value;
    // remember to get OTHER STUFF!! remember there may be multiple links!
    return entry;
}

// from free-programming-books-lint
function getLangFromFilename (filename) {
    const dash = filename.lastIndexOf('-')
    const dot = filename.lastIndexOf('.')
    let lang = filename.slice(dash + 1, dot).replace(/_/, '-')
    if (!languages.hasOwnProperty(lang)) {
      if (/^[a-z]{2}$/.test(lang) || /^[a-z]{2}-[A-Z]{2}$/.test(lang)) {
        return ''
      }
      lang = 'en-US'
    }
    return lang
}

// from free-programming-books-lint
function getFilesFromDir (dir) {
    return fs.readdirSync(dir).filter(file => path.extname(file) === '.md' && excludes.indexOf(file) === -1).map(file => path.join(dir, file))
}

function getMediaFromDirectory(dir){
    const slash = dir.lastIndexOf('/');
    let mediaType = dir.slice(2, slash);
    return mediaType;
}

let parseMarkdown = function(doc){
    let tree = remark.parse(doc).children;
    let children = [];  // This will go into root object later
    let currentDepth = 3;

    // find where Index ends
    // probably could be done better, review later
    let i=0, count = 0;
    for(i; i < tree.length; i++){
        if(tree[i].type=='heading' && tree[i].depth=='3')
            count++;
        if(count == 2)
            break;
    }

    tree.slice(i).forEach( (item) => {
        try { 
            if(item.type == "heading" && item.children[0].value == 'Index')
            return;

        if(item.type == "heading"){
            if(item.depth == 3){
                currentDepth = 3;
                let newGroup = {group: item.children[0].value, entries: [], subsections: []};
                children.push(newGroup);
            }
            else if(item.depth == 4){
                currentDepth = 4;
                let newSubsection = {group: item.children[0].value, entries: []};
                children[children.length-1].subsections.push(newSubsection);
            }
        }
        else if(item.type == 'list'){
            item.children.forEach( (listItem) => {
                let content = listItem.children[0].children;
                // if(content[0].type !== 'link'){ // SKIPS OVER bad formatting
                //     return;
                // }
                if(currentDepth == 3){
                    let contentJson = parseListItem(content);
                    children[children.length-1].entries.push(contentJson);
                }
                else if(currentDepth == 4){
                    let lastChild = children.length-1;
                    let lastSubSec = children[lastChild].subsections.length-1;
                    let contentJson = parseListItem(content);
                    children[lastChild].subsections[lastSubSec].entries.push(contentJson);
                }
            });
        }
        } catch (e) {
            // if there was an error while parsing, print the error to an error log
            // looks really ugly, maybe try to refine output later
            str = JSON.stringify(item);
            fs.appendFileSync("errorlog.txt", `${str} had an error while parsing.\n`, (err) => {
                if (err)
                console.log(err);
               });
        }
    });
    return children;
}

function parseDirectory(directory){
    let dirChildren = [];
    
    let mediaType = getMediaFromDirectory(directory);
    const filenames = getFilesFromDir(path.resolve(directory));
    filenames.forEach((filename) => {
        const doc = fs.readFileSync(filename);
        let children = parseMarkdown(doc);
        const langCode = getLangFromFilename(filename);
        let docJson = {
            language: {
                code: langCode,
                name: languages[langCode],
            },
            index: {
                
            },
            children: children
        };
        dirChildren.push(docJson);
    });
    let dirJson = {
        type: mediaType,
        index: {

        },
        children: dirChildren
    };
    return dirJson
}

function parseAll(dirArray){
    let rootChildren = [];

    dirArray.forEach( (directory) => {
        let dirJson = parseDirectory(directory);
        rootChildren.push(dirJson);
    });
    let rootJson = {
        type: 'root',
        children: rootChildren
    }
    fs.writeFile('root.json', JSON.stringify(rootJson, null, 3), function(err) {
        if (err) {
            console.log(err);
        }
    });
}

console.time('Parse Time')
parseAll(['./books/']);
console.timeEnd('Parse Time');