var path = require('path');
var Immutable = require('immutable');

var Output = require('../models/output');
var Config = require('../models/config');
var Promise = require('../utils/promise');
var fs = require('../utils/fs');

var callHook = require('./callHook');
var preparePlugins = require('./preparePlugins');
var preparePages = require('./preparePages');
var prepareAssets = require('./prepareAssets');
var generateAssets = require('./generateAssets');
var generatePages = require('./generatePages');

/**
    Process an output to generate the book

    @param {Generator} generator
    @param {Output} output

    @return {Promise<Output>}
*/
function processOutput(generator, startOutput) {
    return Promise(startOutput)
    .then(preparePlugins)
    .then(preparePages)
    .then(prepareAssets)

    .then(
        callHook.bind(null,
            'config',
            function(output) {
                var book = output.getBook();
                var config = book.getConfig();
                var values = config.getValues();

                return values.toJS();
            },
            function(output, result) {
                var book = output.getBook();
                var config = book.getConfig();

                config = Config.updateValues(config, result);
                book = book.set('config', config);
                return output.set('book', book);
            }
        )
    )

    .then(
        callHook.bind(null,
            'init',
            function(output) {
                return {};
            },
            function(output) {
                return output;
            }
        )
    )

    .then(function(output) {
        if (!generator.onInit) {
            return output;
        }

        return generator.onInit(output);
    })

    .then(generateAssets.bind(null, generator))
    .then(generatePages.bind(null, generator))

    .tap(function(output) {
        var book = output.getBook();

        if (!book.isMultilingual()) {
            return;
        }

        var books = book.getBooks();
        var outputRoot = output.getRoot();
        var plugins = output.getPlugins();
        var state = output.getState();
        var options = output.getOptions();

        return Promise.forEach(books, function(langBook) {
            // Inherits plugins list, options and state
            var langOptions = options.set('root', path.join(outputRoot, langBook.getLanguage()));
            var langOutput = new Output({
                book:       langBook,
                options:    langOptions,
                state:      state,
                generator:  generator.name,
                plugins:    plugins
            });

            return processOutput(generator, langOutput);
        });
    })

    .then(callHook.bind(null,
        'finish:before',
            function(output) {
                return {};
            },
            function(output) {
                return output;
            }
        )
    )

    .then(function(output) {
        if (!generator.onFinish) {
            return output;
        }

        return generator.onFinish(output);
    })

    .then(callHook.bind(null,
        'finish',
            function(output) {
                return {};
            },
            function(output) {
                return output;
            }
        )
    );
}

/**
    Generate a book using a generator.

    The overall process is:
        1. List and load plugins for this book
        2. Call hook "config"
        3. Call hook "init"
        4. Initialize generator
        5. List all assets and pages
        6. Copy all assets to output
        7. Generate all pages
        8. Call hook "finish:before"
        9. Finish generation
        10. Call hook "finish"


    @param {Generator} generator
    @param {Book} book
    @param {Object} options

    @return {Promise<Output>}
*/
function generateBook(generator, book, options) {
    options = generator.Options(options);
    var state = generator.State? generator.State({}) : Immutable.Map();
    var start = Date.now();

    return Promise(
        new Output({
            book: book,
            options: options,
            state: state,
            generator: generator.name
        })
    )

    // Cleanup output folder
    .then(function(output) {
        var logger = output.getLogger();
        var rootFolder = output.getRoot();

        logger.debug.ln('cleanup folder "' + rootFolder + '"');
        return fs.ensureFolder(rootFolder)
            .thenResolve(output);
    })

    .then(processOutput.bind(null, generator))

    // Log duration and end message
    .then(function(output) {
        var logger = output.getLogger();
        var end = Date.now();
        var duration = (end - start)/1000;

        logger.info.ok('generation finished with success in ' + duration.toFixed(1) + 's !');

        return output;
    });
}

module.exports = generateBook;