var path = require('path');
var format = require('util').format;
var withTrailingSlash = require('okutil').withTrailingSlash;
var withoutTrailingSlash = require('okutil').withoutTrailingSlash;
var assign = require('object-assign');
var express = require('express');
var OKQuery = require('okquery');
var OKView = require('okview');
var OKDB = require('okdb');
var OKResource = require('okresource')
var OKTemplate = require('oktemplate');
var OKServer = require('okserver');
var OKRestEndpoint = require('okrest');
var OKSchema = require('okschema');

/**
 * OKCMS!
 * Basically takes configuration and gives you a server.
 */
function OKCMS(options) {
  if (!(this instanceof OKCMS)) return new OKCMS(options);
  options = options || {};

  var app = express();
  app.enable('strict routing');

  var root = this._root = options.root || 'public';
  var adminConfig = options.admin || {};
  var adminRoot = this._adminRoot = adminConfig.root ||
      path.join(__dirname, '../themes/okadmin/public');
  var adminPath = this._adminPath = adminConfig.path || '/_admin'
  var templateRoot = options.templateRoot || 'templates';
  var adminTemplateRoot = options.templateRoot ||
    path.join(__dirname, '../themes/okadmin/templates');

  var schemaConfig = options.schemas || {};
  var resourceConfig = options.resources || [];
  var viewConfig = options.views || {
    '/': { template: 'index' }
  };

  var templateProvider = this._templateProvider =
      new OKTemplate({root: templateRoot});
  var adminTemplateProvider = this._adminTemplateProvider =
      new OKTemplate({root: adminTemplateRoot});

  var db = new OKDB(options.db || 'fs');
  // Special query to get project wide meta data
  var meta = this._meta = {
    type: 'meta',
    get: function() {
      return db.getMeta();
    }
  };
  var schemas = this._schemas = this._createSchemas(schemaConfig);
  var resourceCache = this._resourceCache =
      this._createResources(resourceConfig, db, schemas);

  // Create view instances from config
  var views = this._views =
      this._createViews(viewConfig, db, meta, resourceCache, templateProvider);

  var server = this._server = new OKServer({
    express: express,
    app: app,
    views: views,
    root: root,
    adminRoot: adminRoot,
    adminPath: adminPath
  });
}

OKCMS.prototype.listen = function listen(port, options) {
  options = options || {};
  this._server.listen(port);
};

OKCMS.prototype._createSchemas = function(schemaConfig) {
  schemaConfig = schemaConfig || {};
  return Object.keys(schemaConfig).reduce(function(cache, key) {
    var spec = schemaConfig[key];
    cache[key] = OKSchema(spec);
    return cache;
  }, {});
}

OKCMS.prototype._createResources = function(resourceConfig, db, schemaCache) {
  resourceConfig = resourceConfig || {};
  var resources = resourceConfig.map(function(config) {
    var type = config.type;
    var schema = schemaCache[type];
    if (!schema)
      throw new Error('Resource config references nonexistent schema');
    var resource = OKResource({
      type: type,
      db: db,
      schema: schema
    });
    // Static resources have some data defined by configuration and
    // are a special case
    if (config.static) {
      resource = resource.instance({static: config.static});
    }
    return resource;
  });
  return ResourceCache(resources);
};

OKCMS.prototype._createViews = function(viewConfig, db,
    meta, resourceCache, templateProvider) {
  viewConfig = viewConfig || {};
  var self = this;
  var createQueries = this._createQueries.bind(this);
  return Object.keys(viewConfig).reduce(function(cache, route) {
    var config = viewConfig[route];
    var templateName = config.template || getDefaultTemplate(route, config);
    var template = templateProvider.getTemplate(templateName);
    if (!template) {
      throw new Error(format('No template named "%s" found', templateName));
    }
    var queryConfig = config.data || [];
    var queries = createQueries(queryConfig, resourceCache);
    // Don't forget to add that trailing slash if the user forgot
    cache[withTrailingSlash(route)] = OKView({
      mount: 'get', // User defined views are read only
      route: route,
      template: template,
      queries: queries,
      meta: meta
    });
    return cache;
  }, {});

  /**
   * Returns the default template for a view config
   */
  function getDefaultTemplate(route, config) {
    // Root route defaults to index
    if (/^\/?$/.test(route))
      return 'index';
    // Otherwise default to the backing resource name
    else if (config && config.data && config.data.type)
      return config.data.type;
    // Otherwise dunno
    else
      return '404';
  }
}

OKCMS.prototype._createQueries = function(queryConfig, resourceCache) {
  queryConfig = queryConfig || {};
  if (!queryConfig.length)
    queryConfig = [queryConfig];
  return queryConfig.map(function(config) {
    var type = config.type;
    var resource = resourceCache.get(type);
    if (!resource)
      throw new Error('Query configured with nonexistent resource');
    // Default to "select all" query
    var query = config.query || '*';
    return new OKQuery({
      resource: resource,
      query: query
    });
  });
};

/**
 * Stupid lil cache to help deal with the fact that
 * resources can be indexed by either type or a type + id combo.
 */
function ResourceCache(resources) {
  if (!(this instanceof ResourceCache)) return new ResourceCache(resources);
  resources = resources || [];
  var cache = this._cache = {};
  resources.forEach(function(resource) {
    if (!resource)
      throw new Error('Undefined resource given to ResourceCache');
    if (resource.bound) {
      cache[resource.type] = resource.parent;
      cache[resource.type + ':' + resource.id] = resource;
    } else {
      cache[resource.type] = resource;
    }
  });
}

ResourceCache.prototype.get = function(type, id) {
  if (!type) return;
  if (id && this._cache[type + ':' + id]) {
    return this._cache[type + ':' + id];
  } else {
    return this._cache[type];
  }
};

module.exports = {

  createApp: function(options) {
    return new OKCMS(options);
  },

  OKResource: OKResource,

  OKView: OKView,

  OKRestEndpoint: OKRestEndpoint

};