diff --git a/browser/lib/Repository.js b/browser/lib/Repository.js
new file mode 100644
index 00000000..40077966
--- /dev/null
+++ b/browser/lib/Repository.js
@@ -0,0 +1,587 @@
+const keygen = require('browser/lib/keygen')
+const fs = require('fs')
+const path = require('path')
+const CSON = require('season')
+const _ = require('lodash')
+
+let repositories = []
+
+/**
+ * # Repository
+ *
+ * ## Life cycle
+ *
+ * ```js
+ * // Add reposiotry
+ * var repo = new Repository({name: 'test', path: '/Users/somebody/test'})
+ * repo
+ *   .mount()
+ *   .then(() => repo.load())
+ *
+ * // Update Cached
+ * repo.updateCache({name: 'renamed'})
+ *
+ * // Update JSON
+ * repo.updateJSON({author: 'Other user'})
+ *
+ * // Remove repository
+ * repo.unmount()
+ * ```
+ *
+ * ## `this.cached`
+ *
+ * Information of a Repository. It stores in `repoStats` key of localStorage
+ *
+ * ```js
+ * this.cached = {
+ *   "key":"523280a789404d430ce571ab9148fdd1343336cb",
+ *   "name":"test",
+ *   "path":"/Users/dickchoi/test"
+ * }
+ * ```
+ *
+ * ## `this.json`
+ *
+ * Parsed object from `boostrepo.json`. See `boostrepo.json`.
+ *
+ * ## Repository file structure
+ *
+ * The root directory of a Repository. It has several files and folders.
+ *
+ * ```
+ * root
+ *  |- data
+ *      |-note1.cson
+ *      |-note2.cson
+ *      |-note3.cson
+ *  |- boostrepo.json
+ * ```
+ *
+ * #### `boostrepo.json`
+ *
+ * ```js
+ * {
+ *   name: String,
+ *   author: String, // Same convention of package.json, `John Doe <email@example.com> (http://example.com)`
+ *   remotes: [{
+ *     name: String,
+ *     url: String, // url of git remote
+ *     branch: String // if branch isn't set, it will try to use `master` branch.
+ *   }],
+ *   folders: [{
+ *     key: String // Unique sha1 hash key to identify folder,
+ *     name: String,
+ *     color: String // All CSS color formats available.
+ *   }]
+ * }
+ * ```
+ *
+ * #### `data` directory
+ *
+ * Every note will be saved here as a single CSON file to `git diff` efficiently.
+ * > This is because CSON supports Multiline string.
+ * File name of each cson file will be used to identify note.
+ * Commonly, Boostnote will automatically generate sha1 key and use it as a file name when creating a new note.
+ *
+ * ##### `note.cson`
+ *
+ * ```cson
+ * name: String
+ * tags: [String] // tags
+ * folder: String // hash key of folder
+ * mode: String // syntax mode
+ * title: String
+ * content: String
+ * createdAt: Date
+ * updatedAt: Date
+ * ```
+ *
+ * ### Full data
+ *
+ * Full data of a Repository. It includes not only information also all data(notes). Redux will directly handle this data.
+ *
+ * ```js
+ * var repo = Object.assign({}, repoJSON, notesData, cached, {status: 'READY'})
+ *
+ * // repo
+ * {
+ *   {...repoJSON}
+ *   "key": "523280a789404d430ce571ab9148fdd1343336cb",
+ *   "name": "test",
+ *   "path": "/Users/dickchoi/test",
+ *   "notes": [], // See `note.cson`
+ *   "status": "READY" // If Boostnote failed to fetch data, It will be set `ERROR`
+ * }
+ * ```
+ */
+
+class Repository {
+  constructor (cached) {
+    this.cached = _.pick(cached, ['key', 'name', 'path'])
+    this.status = 'IDLE'
+    this.isMount = false
+  }
+
+  /**
+   * Reload and set all data of a repository
+   * @return {Promise} full data of a repository
+   */
+  load () {
+    if (!_.isString(this.cached.key)) {
+      console.warn('The key of this repository doesn\'t seem to be valid. You should input this data to Redux reducer after setting the key properly.')
+    }
+    let name = this.cached.name
+    let targetPath = this.cached.path
+
+    targetPath = path.join(targetPath)
+    let dataPath = path.join(targetPath, 'data')
+
+    let initializeRepository = () => {
+      let resolveDataDirectory = this.constructor.resolveDirectory(path.join(targetPath, 'data'))
+      let resolveBoostrepoJSON = this.constructor.resolveJSON(path.join(targetPath, 'boostrepo.json'), {name: name})
+      return Promise.all([resolveDataDirectory, resolveBoostrepoJSON])
+        .then((data) => {
+          this.json = data[1]
+        })
+    }
+
+    let fetchNotes = () => {
+      let noteNames = fs.readdirSync(dataPath)
+      let notes = noteNames
+        .map((noteName) => {
+          let notePath = path.join(dataPath, noteNames)
+
+          return new Promise(function (resolve, reject) {
+            CSON.readFile(notePath, function (err, obj) {
+              if (err != null) {
+                console.log(err)
+                return resolve(null)
+              }
+              obj.key = path.basename(noteName, '.cson')
+              return resolve(obj)
+            })
+          })
+        })
+        .filter((note) => note != null)
+
+      return Promise.all(notes)
+        .then((notes) => {
+          this.notes = notes
+        })
+    }
+
+    return this.constructor.resolveDirectory(targetPath)
+      .then(initializeRepository)
+      .then(fetchNotes)
+      .then(() => {
+        this.status = 'READY'
+
+        return this.getData()
+      })
+      .catch(function handleError (err) {
+        this.status = 'ERROR'
+        this.error = err
+        return err
+      })
+  }
+
+  /**
+   * Add repository to localStorage
+   * If key doesn't exist, it will generate it.
+   * If a cache having same key extists in localStorage, override it.
+   *
+   * @return {Promise} added cache data
+   */
+  mount () {
+    let allCached = this.constructor.getAllCached()
+
+    // If key is not set, generate new one.
+    if (!_.isString(this.cached.key)) {
+      this.cached.key = keygen()
+      // Repeat utill generated key becomes unique.
+      while (_.findIndex(allCached, {key: this.cached.key}) > -1) {
+        this.cached.key = keygen()
+      }
+    }
+
+    let targetCachedIndex = _.findIndex(allCached, {key: this.cached.key})
+    if (targetCachedIndex > -1) {
+      allCached.splice(targetCachedIndex, 1, this.cached)
+    } else {
+      allCached.push(this.cached)
+    }
+    this.constructor.saveAllCached(allCached)
+    this.isMount = true
+
+    // Put in `repositories` array if it isn't in.
+    let targetIndex = _.findIndex(repositories, {cached: {key: this.cached.key}})
+    if (targetIndex < 0) {
+      repositories.push(this)
+    }
+
+    return Promise.resolve(this.cached)
+  }
+
+  /**
+   * Remove repository from localStorage
+   * @return {Promise} remoded cache data
+   */
+  unmount () {
+    let allCached = this.constructor.getAllCached()
+
+    let targetCachedIndex = _.findIndex(allCached, {key: this.cached.key})
+    if (targetCachedIndex > -1) {
+      allCached.splice(targetCachedIndex, 1)
+    }
+    this.constructor.saveAllCached(allCached)
+    this.isMount = false
+
+    // Discard from `repositories` array if it is in.
+    let targetIndex = _.findIndex(repositories, {cached: {key: this.cached.key}})
+    if (targetIndex > -1) {
+      repositories.splice(targetIndex, 1)
+    }
+
+    return Promise.resolve(this.cached)
+  }
+
+  /**
+   * Get all data of a repository
+   *
+   * If data is not ready, try to load it.
+   *
+   * @return {Promise} all data of a repository
+   */
+  getData () {
+    if (this.status !== 'READY') {
+      return this.load()
+    }
+
+    return Promise.resolve(Object.assign({}, this.json, this.cached, {
+      status: this.status,
+      notes: this.notes
+    }))
+  }
+
+  /**
+   * Save Cached
+   * @param  {Object} newCached
+   * @return {Promies} updated Cached
+   */
+  saveCached (newCached) {
+    if (_.isObject(newCached)) {
+      Object.assign(this.cached, _.pick(newCached, ['name', 'path']))
+    }
+
+    if (this.isMount) {
+      this.mount()
+    }
+
+    return Promise.resolve(this.cached)
+  }
+
+  /**
+   * Save JSON
+   * @param  {Object}  newJSON
+   * @return {Promise} updated JSON
+   */
+  saveJSON (newJSON) {
+    let jsonPath = path.join(this.cached.path, 'boostrepo.json')
+    Object.assign(this.json, newJSON)
+
+    return new Promise(function (resolve, reject) {
+      CSON
+        .writeFile(jsonPath, this.json, function (err) {
+          if (err != null) return reject(err)
+          resolve(this.json)
+        })
+    })
+  }
+
+  /**
+   * Save both Cached and JSON
+   * @return {Promise} resolve array have cached and JSON
+   */
+  save () {
+    return Promise.all([this.saveCached(), this.saveJSON()])
+  }
+
+  /**
+   * Add a folder
+   * @param {Object} newFolder
+   * @return {Promise} new folder
+   */
+  addFolder (newFolder) {
+    let { folders } = this.json
+
+    newFolder = _.pick(newFolder, ['color', 'name'])
+    if (!_.isString(newFolder.name) || newFolder.name.trim().length === 0) newFolder.name = 'unnamed'
+    else newFolder.name = newFolder.trim()
+
+    if (!_.isString(newFolder.color)) newFolder.color = ''
+
+    newFolder.key = keygen()
+    while (_.findIndex(folders, {key: newFolder.key}) > -1) {
+      newFolder.key = keygen()
+    }
+
+    folders.push(newFolder)
+
+    return this.updateJSON(this.json)
+      .then(() => newFolder)
+  }
+
+  /**
+   * Update a folder
+   * @param  {String} folderKey [description]
+   * @param  {Object} override   [description]
+   * @return {[type]}           [description]
+   */
+  updateFolder (folderKey, override) {
+    let { folders } = this.json
+
+    let targetFolder = _.find(folders, {key: folderKey})
+    if (targetFolder == null) {
+      return this.addFolder(override)
+    }
+    if (_.isString(override.name) && override.name.trim().length > 0) targetFolder.name = override.name.trim()
+    if (_.isString(override.color)) targetFolder.color = override.color
+
+    return this.updateJSON(this.json)
+      .then(() => targetFolder)
+  }
+
+  /**
+   * Remove a folder
+   * @param  {String} folderKey
+   * @return {Promise} removed folder
+   */
+  removeFolder (folderKey) {
+    let { folders } = this.json
+    let targetFolder = null
+
+    let targetIndex = _.findIndex(folders, {key: folderKey})
+    if (targetIndex > -1) {
+      targetFolder = folders.splice(targetIndex, 1)[0]
+    }
+
+    return this.updateJSON(null)
+      .then(() => targetFolder)
+  }
+
+  addNote (newNote) {
+    newNote = Object.assign({}, _.pick(newNote, ['content', 'tags', 'folder', 'mode', 'title']))
+
+    if (!this.constructor.validateNote(newNote)) {
+      return Promise.reject(new Error('Invalid input'))
+    }
+
+    newNote.key = keygen()
+    while (_.find(this.notes, {key: newNote.key}) != null) {
+      newNote.key = keygen()
+    }
+    newNote.createdAt = new Date()
+    newNote.updatedAt = new Date()
+    this.notes.push(newNote)
+
+    return new Promise((resolve, reject) => {
+      CSON.writeFile(path.join(this.cached.path, 'data', newNote.key + '.cson'), _.omit(newNote, ['key']), function (err) {
+        if (err != null) return reject(err)
+        resolve(newNote)
+      })
+    })
+  }
+
+  static validateNote (note) {
+    if (!_.isString(note.title)) return false
+    if (!_.isString(note.content)) return false
+    if (!_.isArray(note.tags)) return false
+    if (!note.tags.every((tag) => _.isString(tag))) return false
+    if (!_.isString(note.folder)) return false
+    if (!_.isString(note.mode)) return false
+    return true
+  }
+
+  getNote (noteKey) {
+    let note = _.find(this.notes, {key: noteKey})
+
+    return Promise.resolve(note)
+  }
+
+  updateNote (noteKey, override) {
+    let note = _.find(this.notes, {key: noteKey})
+    let isNew = false
+    if (note == null) {
+      note = override
+      isNew = true
+    }
+
+    if (!this.constructor.validateNote(note)) {
+      return Promise.reject(new Error('Invalid input'))
+    }
+
+    if (isNew) this.notes.push(note)
+    note.updatedAt = new Date()
+
+    return new Promise((resolve, reject) => {
+      CSON.writeFile(path.join(this.cached.path, 'data', note.key + '.cson'), _.omit(note, ['key']), function (err) {
+        if (err != null) return reject(err)
+        resolve(note)
+      })
+    })
+  }
+
+  removeNote (noteKey) {
+    let noteIndex = _.findIndex(this.notes, {key: noteKey})
+
+    if (noteIndex < 0) return Promise.resolve(null)
+
+    let note = this.notes[noteIndex]
+    this.notes.splice(noteIndex, 1)
+
+    return new Promise((resolve, reject) => {
+      fs.unlink(path.join(this.cached.path, 'data', noteKey + '.cson'), function (err) {
+        if (err != null) return reject(err)
+        resolve(note)
+      })
+    })
+  }
+
+  getAllNotes () {
+    return Promise.resolve(this.notes)
+  }
+
+  static generateDefaultJSON (override) {
+    return Object.assign({
+      name: 'unnamed',
+      remotes: [],
+      folders: [{
+        key: keygen(),
+        name: 'general',
+        color: 'green'
+      }]
+    }, override)
+  }
+
+  /**
+   * # Resolve Repository JSON
+   *
+   * Fetch and parse JSON from given path.
+   * If boostrepo.json doesn't exist, create new one.
+   *
+   * @param  {String} targetPath [description]
+   * @param  {Object} defaultOverrides Overrided to default value of RepoJSON when creating new one.
+   * @return {Promise} resolving parsed data
+   */
+  static resolveJSON (targetPath, defaultOverrides) {
+    return new Promise(function checkIfExists (resolve, reject) {
+      // If JSON doesn't exist, make a new one.
+      if (CSON.resolve(targetPath) == null) {
+        let newRepoJSON = this.constructor.generateDefaultJSON(defaultOverrides)
+        CSON.writeFile(targetPath, newRepoJSON, function (err) {
+          if (err != null) return reject(err)
+          resolve(newRepoJSON)
+        })
+      } else {
+        CSON.readFile(targetPath, function (err, obj) {
+          if (err != null) return reject(err)
+          resolve(obj)
+        })
+      }
+    })
+  }
+
+  /**
+   * # Resolve directory.
+   *
+   * Make sure the directory exists.
+   * If directory doesn't exist, it will try to make a new one.
+   * If failed, it return rejected promise
+   *
+   * @param  {String} targetPath Target path of directory
+   * @return {Promise} resolving targetPath
+   */
+  static resolveDirectory (targetPath) {
+    return new Promise(function (resolve, reject) {
+      // check the directory exists
+      fs.stat(targetPath, function (err, stat) {
+        // Reject errors except `ENOENT`
+        if (err != null && err.code !== 'ENOENT') {
+          return reject(err)
+        }
+
+        // Handle no suchfile error only
+        // Make new Folder by given path
+        if (err != null) {
+          return fs.mkdir(targetPath, function (err, stat) {
+            // If failed to make a new directory, reject it.
+            if (err != null) {
+              return reject(err)
+            }
+            resolve(targetPath)
+          })
+        }
+
+        // Check the target is not a directory
+        if (!stat.isDirectory()) {
+          return reject(new Error(targetPath + ' path is not a directory'))
+        }
+        resolve(targetPath)
+      })
+    })
+  }
+
+  /**
+   * Get all repository stats from localStorage
+   * it is stored to `repositories` key.
+   * if the data is corrupted, re-intialize it.
+   *
+   * @return {Array} registered repositories
+   * ```
+   * [{
+   *   key: String,
+   *   name: String,
+   *   path: String // path of repository
+   * }]
+   * ```
+   */
+  static getAllCached () {
+    let data
+    try {
+      data = JSON.parse(localStorage.getItem('repositories'))
+      if (!_.isArray(data)) {
+        throw new Error('Data is corrupted. it must be an array.')
+      }
+    } catch (err) {
+      console.log(err)
+      data = []
+      this.saveAllCached(data)
+    }
+    return data
+  }
+
+  static saveAllCached (allCached) {
+    localStorage.setItem('repositories', JSON.stringify(allCached))
+  }
+
+  static loadAll () {
+    repositories = []
+    return Promise.all(this.getAllCached().map((cached) => {
+      let repo = new this(cached)
+      repositories.push(repo)
+
+      return repo.load()
+    }))
+  }
+
+  static list () {
+    return Promise.resolve(repositories)
+  }
+
+  static find (repoKey) {
+    let repository = _.find(repositories, {cached: {key: repoKey}})
+    return Promise.resolve(repository)
+  }
+}
+
+export default Repository