var util = require('./util')
var slice = util.slice
var pluck = util.pluck
var each = util.each
var bind = util.bind
var create = util.create
var isList = util.isList
var isFunction = util.isFunction
var isObject = util.isObject

module.exports = {
	createStore: createStore
}

var storeAPI = {
	version: '2.0.12',
	enabled: false,
	
	// get returns the value of the given key. If that value
	// is undefined, it returns optionalDefaultValue instead.
	get: function(key, optionalDefaultValue) {
		var data = this.storage.read(this._namespacePrefix + key)
		return this._deserialize(data, optionalDefaultValue)
	},

	// set will store the given value at key and returns value.
	// Calling set with value === undefined is equivalent to calling remove.
	set: function(key, value) {
		if (value === undefined) {
			return this.remove(key)
		}
		this.storage.write(this._namespacePrefix + key, this._serialize(value))
		return value
	},

	// remove deletes the key and value stored at the given key.
	remove: function(key) {
		this.storage.remove(this._namespacePrefix + key)
	},

	// each will call the given callback once for each key-value pair
	// in this store.
	each: function(callback) {
		var self = this
		this.storage.each(function(val, namespacedKey) {
			callback.call(self, self._deserialize(val), (namespacedKey || '').replace(self._namespaceRegexp, ''))
		})
	},

	// clearAll will remove all the stored key-value pairs in this store.
	clearAll: function() {
		this.storage.clearAll()
	},

	// additional functionality that can't live in plugins
	// ---------------------------------------------------

	// hasNamespace returns true if this store instance has the given namespace.
	hasNamespace: function(namespace) {
		return (this._namespacePrefix == '__storejs_'+namespace+'_')
	},

	// createStore creates a store.js instance with the first
	// functioning storage in the list of storage candidates,
	// and applies the the given mixins to the instance.
	createStore: function() {
		return createStore.apply(this, arguments)
	},
	
	addPlugin: function(plugin) {
		this._addPlugin(plugin)
	},
	
	namespace: function(namespace) {
		return createStore(this.storage, this.plugins, namespace)
	}
}

function _warn() {
	var _console = (typeof console == 'undefined' ? null : console)
	if (!_console) { return }
	var fn = (_console.warn ? _console.warn : _console.log)
	fn.apply(_console, arguments)
}

function createStore(storages, plugins, namespace) {
	if (!namespace) {
		namespace = ''
	}
	if (storages && !isList(storages)) {
		storages = [storages]
	}
	if (plugins && !isList(plugins)) {
		plugins = [plugins]
	}

	var namespacePrefix = (namespace ? '__storejs_'+namespace+'_' : '')
	var namespaceRegexp = (namespace ? new RegExp('^'+namespacePrefix) : null)
	var legalNamespaces = /^[a-zA-Z0-9_\-]*$/ // alpha-numeric + underscore and dash
	if (!legalNamespaces.test(namespace)) {
		throw new Error('store.js namespaces can only have alphanumerics + underscores and dashes')
	}
	
	var _privateStoreProps = {
		_namespacePrefix: namespacePrefix,
		_namespaceRegexp: namespaceRegexp,

		_testStorage: function(storage) {
			try {
				var testStr = '__storejs__test__'
				storage.write(testStr, testStr)
				var ok = (storage.read(testStr) === testStr)
				storage.remove(testStr)
				return ok
			} catch(e) {
				return false
			}
		},

		_assignPluginFnProp: function(pluginFnProp, propName) {
			var oldFn = this[propName]
			this[propName] = function pluginFn() {
				var args = slice(arguments, 0)
				var self = this

				// super_fn calls the old function which was overwritten by
				// this mixin.
				function super_fn() {
					if (!oldFn) { return }
					each(arguments, function(arg, i) {
						args[i] = arg
					})
					return oldFn.apply(self, args)
				}

				// Give mixing function access to super_fn by prefixing all mixin function
				// arguments with super_fn.
				var newFnArgs = [super_fn].concat(args)

				return pluginFnProp.apply(self, newFnArgs)
			}
		},

		_serialize: function(obj) {
			return JSON.stringify(obj)
		},

		_deserialize: function(strVal, defaultVal) {
			if (!strVal) { return defaultVal }
			// It is possible that a raw string value has been previously stored
			// in a storage without using store.js, meaning it will be a raw
			// string value instead of a JSON serialized string. By defaulting
			// to the raw string value in case of a JSON parse error, we allow
			// for past stored values to be forwards-compatible with store.js
			var val = ''
			try { val = JSON.parse(strVal) }
			catch(e) { val = strVal }

			return (val !== undefined ? val : defaultVal)
		},
		
		_addStorage: function(storage) {
			if (this.enabled) { return }
			if (this._testStorage(storage)) {
				this.storage = storage
				this.enabled = true
			}
		},

		_addPlugin: function(plugin) {
			var self = this

			// If the plugin is an array, then add all plugins in the array.
			// This allows for a plugin to depend on other plugins.
			if (isList(plugin)) {
				each(plugin, function(plugin) {
					self._addPlugin(plugin)
				})
				return
			}

			// Keep track of all plugins we've seen so far, so that we
			// don't add any of them twice.
			var seenPlugin = pluck(this.plugins, function(seenPlugin) {
				return (plugin === seenPlugin)
			})
			if (seenPlugin) {
				return
			}
			this.plugins.push(plugin)

			// Check that the plugin is properly formed
			if (!isFunction(plugin)) {
				throw new Error('Plugins must be function values that return objects')
			}

			var pluginProperties = plugin.call(this)
			if (!isObject(pluginProperties)) {
				throw new Error('Plugins must return an object of function properties')
			}

			// Add the plugin function properties to this store instance.
			each(pluginProperties, function(pluginFnProp, propName) {
				if (!isFunction(pluginFnProp)) {
					throw new Error('Bad plugin property: '+propName+' from plugin '+plugin.name+'. Plugins should only return functions.')
				}
				self._assignPluginFnProp(pluginFnProp, propName)
			})
		},
		
		// Put deprecated properties in the private API, so as to not expose it to accidential
		// discovery through inspection of the store object.
		
		// Deprecated: addStorage
		addStorage: function(storage) {
			_warn('store.addStorage(storage) is deprecated. Use createStore([storages])')
			this._addStorage(storage)
		}
	}

	var store = create(_privateStoreProps, storeAPI, {
		plugins: []
	})
	store.raw = {}
	each(store, function(prop, propName) {
		if (isFunction(prop)) {
			store.raw[propName] = bind(store, prop)			
		}
	})
	each(storages, function(storage) {
		store._addStorage(storage)
	})
	each(plugins, function(plugin) {
		store._addPlugin(plugin)
	})
	return store
}