var _ = require('lodash');
var Q = require('q');
var path = require('path');
var Ignore = require('ignore');
var parsers = require('gitbook-parsers');

var Logger = require('./logger');
var Config = require('./config');
var Readme = require('./backbone/readme');
var Glossary = require('./backbone/glossary');
var Summary = require('./backbone/summary');
var Langs = require('./backbone/langs');
var Page = require('./backbone/page');
var pathUtil = require('./utils/path');

function Book(opts) {
    if (!(this instanceof Book)) return new Book(opts);

    opts = _.defaults(opts || {}, {
        fs: null,

        // Root path for the book
        root: '',

        // Extend book configuration
        config: {},

        // Log function
        log: function(msg) {
            process.stdout.write(msg);
        },

        // Log level
        logLevel: 'info'
    });

    if (!opts.fs) throw new Error('Book requires a fs instance');

    // Root path for the book
    this.root = opts.root;

    // If multi-lingual, book can have a parent
    this.parent = opts.parent;

    // A book is linked to an fs, to access its content
    this.fs = opts.fs;

    // Rules to ignore some files
    this.ignore = Ignore();
    this.ignore.addPattern([
        // Skip Git stuff
        '.git/',
        '.gitignore',

        // Skip OS X meta data
        '.DS_Store',

        // Skip stuff installed by plugins
        'node_modules',

        // Skip book outputs
        '_book',
        '*.pdf',
        '*.epub',
        '*.mobi',

        // Skip config files
        '.ignore',
        '.bookignore',
        'book.json'
    ]);

    // Create a logger for the book
    this.log = new Logger(opts.log, opts.logLevel);

    // Create an interface to access the configuration
    this.config = new Config(this, opts.config);

    // Interfaces for the book structure
    this.readme = new Readme(this);
    this.summary = new Summary(this);
    this.glossary = new Glossary(this);

    // Multilinguals book
    this.langs = new Langs(this);
    this.books = [];

    // List of page in the book
    this.pages = {};

    _.bindAll(this);
}

// Parse and prepare the configuration, fail if invalid
Book.prototype.prepareConfig = function() {
    return this.config.load();
};

// Resolve a path in the book source
// Enforce that the output path in the root folder
Book.prototype.resolve = function() {
    return pathUtil.resolveInRoot.apply(null, [this.root].concat(_.toArray(arguments)));
};

// Parse .gitignore, etc to extract rules
Book.prototype.parseIgnoreRules = function() {
    var that = this;

    return _.reduce([
        '.ignore',
        '.gitignore',
        '.bookignore'
    ], function(prev, filename) {
        return prev.then(function() {
            return that.readFile(filename);
        })
        .then(function(content) {
            that.ignore.addPattern(content.toString().split(/\r?\n/));
        });
    }, Q());
};

// Parse the whole book
Book.prototype.parse = function() {
    var that = this;

    return Q()
    .then(this.prepareConfig)
    .then(this.parseIgnoreRules)

    // Parse languages
    .then(function() {
        return that.langs.load();
    })

    .then(function() {
        if (that.isMultilingual()) {
            that.log.info.ln('Parsing multilingual book, with', that.langs.count(), 'languages');
            return;
        }

        return Q()
        .then(that.readme.load)
        .then(function() {
            if (that.readme.exists()) return;

            throw new Error('No README file (or is ignored)');
        })

        .then(that.summary.load)
        .then(function() {
            if (that.summary.exists()) return;

            throw new Error('No SUMMARY file (or is ignored)');
        })

        .then(that.glossary.load);
    });
};

// Mark a filename as being parsable
Book.prototype.addPage = function(filename) {
    filename = pathUtil.normalize(filename);

    if (this.pages[filename]) return;
    this.pages[filename] = new Page(this, filename);
};

// Return a page by its filename (or undefined)
Book.prototype.getPage = function(filename) {
    filename = pathUtil.normalize(filename);
    return this.pages[filename];
};


// Return true, if has a specific page
Book.prototype.hasPage = function(filename) {
    return Boolean(this.getPage(filename));
};

// Test if a file is ignored, return true if it is
Book.prototype.isFileIgnored = function(filename) {
    return this.ignore.filter([filename]).length == 0;
};

// Read a file in the book, throw error if ignored
Book.prototype.readFile = function(filename) {
    if (this.isFileIgnored(filename)) return Q.reject(new Error('File "'+filename+'" is ignored'));
    return this.fs.readAsString(this.resolve(filename));
};

// Find a parsable file using a filename
Book.prototype.findParsableFile = function(filename) {
    var that = this;

    var ext = path.extname(filename);
    var basename = path.basename(filename, ext);

    // Ordered list of extensions to test
    var exts = parsers.extensions;
    if (ext) exts = _.uniq([ext].concat(exts));

    return _.reduce(exts, function(prev, ext) {
        return prev.then(function(output) {
            // Stop if already find a parser
            if (output) return output;

            var filepath = basename+ext;

            return that.fs.findFile(that.root, filepath)
            .then(function(realFilepath) {
                if (!realFilepath) return null;

                return {
                    parser: parsers.get(ext),
                    path: realFilepath
                };
            });
        });
    }, Q(null));
};

// Return true if book is associated to a language
Book.prototype.isLanguageBook = function() {
    return Boolean(this.parent);
};
Book.prototype.isSubBook = Book.prototype.isLanguageBook;

// Return true if the book is main instance of a multilingual book
Book.prototype.isMultilingual = function() {
    return this.langs.count() > 0;
};

module.exports = Book;