var path = require('path'),
    Promise = require('bluebird'),
    db = require('../db'),
    errors = require('../../errors'),
    i18n = require('../../i18n'),
    ghostVersion = require('../../utils/ghost-version');

/**
 * Database version has always two digits
 * Database version is Ghost Version X.X
 *
 * @TODO: remove alpha text!
 * @TODO: extend database validation
 */
function validateDatabaseVersion(version) {
    if (version === null) {
        throw new errors.DatabaseNotSeededError({
            message: i18n.t('errors.data.versioning.index.databaseNotSeeded')
        });
    }

    if (!version.match(/\d\.\d/gi)) {
        throw new errors.DatabaseVersionError({
            message: 'Your database version is not compatible with Ghost 1.0.0 Alpha (master branch)',
            context: 'Want to keep your DB? Use Ghost < 1.0.0 or the "stable" branch. Otherwise please delete your DB and restart Ghost',
            help: 'More information on the Ghost 1.0.0 Alpha at https://support.ghost.org/v1-0-alpha'
        });
    }

    return version;
}

/**
 * If the database version is null, the database was never seeded.
 * The seed migration script will set your database to current Ghost Version.
 */
function getDatabaseVersion() {
    return db.knex.schema.hasTable('settings').then(function (exists) {
        if (!exists) {
            return Promise.reject(new errors.DatabaseNotPopulatedError({
                message: i18n.t('errors.data.versioning.index.databaseNotPopulated')
            }));
        }

        return db.knex('settings')
            .where('key', 'databaseVersion')
            .first('value')
            .then(function (version) {
                return validateDatabaseVersion(version.value);
            });
    });
}

function getNewestDatabaseVersion() {
    return ghostVersion.safe;
}

/**
 * Database version cannot set from outside.
 * If this function get called, we set the database version to your current Ghost version.
 */
function setDatabaseVersion(transaction) {
    return (transaction || db.knex)('settings')
        .where('key', 'databaseVersion')
        .update({
            value: getNewestDatabaseVersion()
        });
}

/**
 * return the versions which need migration
 * when on 1.1 and we update to 1.4, we expect [1.2, 1.3, 1.4]
 */
function getMigrationVersions(fromVersion, toVersion) {
    var versions = [],
        i;

    for (i = (fromVersion * 10) + 1; i <= toVersion * 10; i += 1) {
        versions.push((i / 10).toString());
    }

    return versions;
}

/**
 * ### Get Version Tasks
 * Tries to require a directory matching the version number
 *
 * This was split from update to make testing easier
 *
 * @param {String} version
 * @param {String} relPath
 * @param {Function} logger
 * @returns {Array}
 */
function getVersionTasks(version, relPath, logger) {
    var tasks = [];

    try {
        tasks = require(path.join(relPath, version));
    } catch (e) {
        logger.info('No tasks found for version', version);
    }

    return tasks;
}

function getUpdateDatabaseTasks(version, logger) {
    return getVersionTasks(version, '../migration/', logger);
}

function getUpdateFixturesTasks(version, logger) {
    return getVersionTasks(version, '../migration/fixtures/', logger);
}

module.exports = {
    canMigrateFromVersion: '1.0',
    getNewestDatabaseVersion: getNewestDatabaseVersion,
    getDatabaseVersion: getDatabaseVersion,
    setDatabaseVersion: setDatabaseVersion,
    getMigrationVersions: getMigrationVersions,
    getUpdateDatabaseTasks: getUpdateDatabaseTasks,
    getUpdateFixturesTasks: getUpdateFixturesTasks
};