// Seeder
// -------

'use strict';

var fs = require('fs');
var path = require('path');
var _ = require('lodash');
var mkdirp = require('mkdirp');
var Promise = require('../promise');

// The new seeds we're performing, typically called from the `knex.seed`
// interface on the main `knex` object. Passes the `knex` instance performing
// the seeds.
function Seeder(knex) {
  this.knex = knex;
  this.config = this.setConfig(knex.client.config.seeds);
}

// Runs all seed files for the given environment.
Seeder.prototype.run = Promise.method(function (config) {
  this.config = this.setConfig(config);
  return this._seedData().bind(this).spread(function (all) {
    return this._runSeeds(all);
  });
});

// Creates a new seed file, with a given name.
Seeder.prototype.make = function (name, config) {
  this.config = this.setConfig(config);
  if (!name) Promise.rejected(new Error('A name must be specified for the generated seed'));
  return this._ensureFolder(config).bind(this).then(this._generateStubTemplate).then(this._writeNewSeed(name));
};

// Lists all available seed files as a sorted array.
Seeder.prototype._listAll = Promise.method(function (config) {
  this.config = this.setConfig(config);
  return Promise.promisify(fs.readdir, fs)(this._absoluteConfigDir()).bind(this).then(function (seeds) {
    return _.filter(seeds, function (value) {
      var extension = path.extname(value);
      return _.contains(['.co', '.coffee', '.eg', '.iced', '.js', '.litcoffee', '.ls'], extension);
    }).sort();
  });
});

// Gets the seed file list from the specified seed directory.
Seeder.prototype._seedData = function () {
  return Promise.join(this._listAll());
};

// Ensures a folder for the seeds exist, dependent on the
// seed config settings.
Seeder.prototype._ensureFolder = function () {
  var dir = this._absoluteConfigDir();
  return Promise.promisify(fs.stat, fs)(dir)['catch'](function () {
    return Promise.promisify(mkdirp)(dir);
  });
};

// Run seed files, in sequence.
Seeder.prototype._runSeeds = function (seeds) {
  return Promise.all(_.map(seeds, this._validateSeedStructure, this)).bind(this).then(function (seeds) {
    return Promise.bind(this).then(function () {
      return this._waterfallBatch(seeds);
    });
  });
};

// Validates seed files by requiring and checking for a `seed` function.
Seeder.prototype._validateSeedStructure = function (name) {
  var seed = require(path.join(this._absoluteConfigDir(), name));
  if (typeof seed.seed !== 'function') {
    throw new Error('Invalid seed file: ' + name + ' must have a seed function');
  }
  return name;
};

// Generates the stub template for the current seed file, returning a compiled template.
Seeder.prototype._generateStubTemplate = function () {
  var stubPath = this.config.stub || path.join(__dirname, 'stub', this.config.extension + '.stub');
  return Promise.promisify(fs.readFile, fs)(stubPath).then(function (stub) {
    return _.template(stub.toString(), null, { variable: 'd' });
  });
};

// Write a new seed to disk, using the config and generated filename,
// passing any `variables` given in the config to the template.
Seeder.prototype._writeNewSeed = function (name) {
  var config = this.config;
  var dir = this._absoluteConfigDir();
  return function (tmpl) {
    if (name[0] === '-') name = name.slice(1);
    var filename = name + '.' + config.extension;
    return Promise.promisify(fs.writeFile, fs)(path.join(dir, filename), tmpl(config.variables || {}))['return'](path.join(dir, filename));
  };
};

// Runs a batch of seed files.
Seeder.prototype._waterfallBatch = function (seeds) {
  var knex = this.knex;
  var seedDirectory = this._absoluteConfigDir();
  var current = Promise.bind({ failed: false, failedOn: 0 });
  var log = [];
  _.each(seeds, function (seed) {
    var name = path.join(seedDirectory, seed);
    seed = require(name);

    // Run each seed file.
    current = current.then(function () {
      return seed.seed(knex, Promise);
    }).then(function () {
      log.push(name);
    });
  });

  return current.thenReturn([log]);
};

Seeder.prototype._absoluteConfigDir = function () {
  return path.resolve(process.cwd(), this.config.directory);
};

Seeder.prototype.setConfig = function (config) {
  return _.extend({
    extension: 'js',
    directory: './seeds'
  }, this.config || {}, config);
};

module.exports = Seeder;