var util = require("util");
var path = require("path");
var Q = require("q");
var _ = require("lodash");

var nunjucks = require("nunjucks");
var AutoEscapeExtension = require("nunjucks-autoescape");
var FilterExtension = require("nunjucks-filter");
var I18nExtension = require("nunjucks-i18n");

var fs = require("../utils/fs");
var BaseGenerator = require("../generator");
var links = require("../utils/links");
var pageUtil = require("../utils/page");

var pkg = require("../../package.json");

var Generator = function() {
    BaseGenerator.apply(this, arguments);

    // revision
    this.revision = new Date();

    // Style to integrates in the output
    this.styles = ["website"];

    // Convert images (svg -> png)
    this.convertImages = false;

    // Templates
    this.templates = {};
};
util.inherits(Generator, BaseGenerator);

// Prepare the genertor
Generator.prototype.prepare = function() {
    return BaseGenerator.prototype.prepare.apply(this)
    .then(this.prepareStyles)
    .then(this.prepareTemplates)
    .then(this.prepareTemplateEngine);
};

// Prepare all styles
Generator.prototype.prepareStyles = function() {
    var that = this;

    this.styles = _.chain(this.styles)
        .map(function(style) {
            var stylePath = that.options.styles[style];
            if (fs.existsSync(path.resolve(that.book.root, stylePath))) {
                return stylePath;
            }
            return null;
        })
        .compact()
        .value();

    return Q();
};

// Prepare templates
Generator.prototype.prepareTemplates = function() {
	this.templates["page"] = this.book.plugins.template("site:page") || path.resolve(this.options.theme, 'templates/website/page.html');
    this.templates["langs"] = this.book.plugins.template("site:langs") || path.resolve(this.options.theme, 'templates/website/langs.html');
    this.templates["glossary"] = this.book.plugins.template("site:glossary") || path.resolve(this.options.theme, 'templates/website/glossary.html');

	return Q();
};

// Prepare template engine
Generator.prototype.prepareTemplateEngine = function() {
    var that = this;

    return fs.readdir(path.resolve(__dirname, "../../theme/i18n"))
    .then(function(locales) {
        var language = that.book.config.normalizeLanguage();

        locales = _.chain(locales)
            .map(function(local) {
                local = path.basename(local, ".json");
                return [local, require("../../theme/i18n/"+local)];
            })
            .object()
            .value();

        if (!_.contains(_.keys(locales), language) && language != "en") {
            that.book.log.warn.ln("Language '"+language+"' is not available as a layout locales (en, "+_.keys(locales).join(", ")+")");
        }

        var folders = _.chain(that.templates)
            .values()
            .map(path.dirname)
            .uniq()
            .value();

        that.env = new nunjucks.Environment(
            new nunjucks.FileSystemLoader(folders),
            {
                autoescape: true
            }
        );

        // Add filter
        that.env.addFilter("contentLink", that.book.contentLink.bind(that.book));
        that.env.addFilter('lvl', function(lvl) {
            return lvl.split(".").length;
        });

        // Add extension
        that.env.addExtension('AutoEscapeExtension', new AutoEscapeExtension(that.env));
        that.env.addExtension('FilterExtension', new FilterExtension(that.env));
        that.env.addExtension('I18nExtension', new I18nExtension({
            env: that.env,
            translations: locales,
            locale: "language"
        }));
    });
};

// Finis generation
Generator.prototype.finish = function() {
    return this.copyAssets()
    .then(this.copyCover)
    .then(this.writeGlossary)
    .then(this.writeSearchIndex);
};

// Convert an input file
Generator.prototype.convertFile = function(input) {
    var that = this;

    return that.book.parsePage(input, {
        convertImages: that.convertImages,
        interpolateTemplate: function(page) {
            return that.callHook("page:before", page);
        },
        interpolateContent: function(page) {
            return that.callHook("page", page);
        }
    })
    .then(function(page) {
        var relativeOutput = that.book.contentLink(page.path);
        var output = path.join(that.options.output, relativeOutput);

        var basePath = path.relative(path.dirname(output), that.options.output) || ".";
        if (process.platform === 'win32') basePath = basePath.replace(/\\/g, '/');

        that.book.log.info.ln("write parsed file", page.path, "to", relativeOutput);

        return that._writeTemplate(that.templates["page"], {
            progress: page.progress,

            _input: page.path,
            content: page.sections,

            basePath: basePath,
            staticBase: links.join(basePath, "gitbook")
        }, output);
    });
};

// Write the index for langs
Generator.prototype.langsIndex = function(langs) {
    var that = this;

    return this._writeTemplate(this.templates["langs"], {
        langs: langs
    }, path.join(this.options.output, "index.html"));
};

// Write glossary
Generator.prototype.writeGlossary = function() {
    var that = this;

    // No glossary
    if (this.book.glossary.length == 0) return Q();

    return this._writeTemplate(this.templates["glossary"], {}, path.join(this.options.output, "GLOSSARY.html"));
};

// Write the search index
Generator.prototype.writeSearchIndex = function() {
    var that = this;

    return fs.writeFile(
        path.join(this.options.output, "search_index.json"),
        JSON.stringify(this.book.searchIndex)
    );
};

// Convert a page into a normalized data set
Generator.prototype.normalizePage  = function(page) {
    var that = this;

    var _callHook = function(name) {
        return that.callHook(name, page)
        .then(function(_page) {
            page = _page;
            return page;
        });
    };

    return Q()
    .then(function() {
        return _callHook("page");
    })
    .then(function() {
        return page;
    });
};

// Generate a template
Generator.prototype._writeTemplate = function(tpl, options, output, interpolate) {
    var that = this;

    interpolate = interpolate || _.identity;
    return Q()
    .then(function(sections) {
    	return that.env.render(
    		tpl,
    		_.extend({
                gitbook: {
                    version: pkg.version
                },

	            styles: that.styles,

	            revision: that.revision,

	            title: that.options.title,
	            description: that.options.description,
                language: that.book.config.normalizeLanguage(),

	            glossary: that.book.glossary,

	            summary: that.book.summary,
	            allNavigation: that.book.navigation,

	            plugins: that.book.plugins,
	            pluginsConfig: JSON.stringify(that.options.pluginsConfig),
	            htmlSnippet: _.partialRight(that.book.plugins.html, that, options),

	            options: that.options,

                basePath: ".",
                staticBase: path.join(".", "gitbook"),
	        }, options)
	    );
    })
    .then(interpolate)
    .then(function(html) {
        return fs.writeFile(
            output,
            html
        );
    });
};

// Copy assets
Generator.prototype.copyAssets = function() {
    var that = this;

    // Copy gitbook assets
    return fs.copy(
        path.join(that.options.theme, "assets"),
        path.join(that.options.output, "gitbook")
    )

    // Copy plugins assets
    .then(function() {
        return Q.all(
            _.map(that.book.plugins.list, function(plugin) {
                var pluginAssets = path.join(that.options.output, "gitbook/plugins/", plugin.name);
                return plugin.copyAssets(pluginAssets, {
                    base: "book"
                });
            })
        );
    });
};

module.exports = Generator;