# **[flo](https://github.com/FLOChip/flo)** is an redis powered node.js autocompleter inspired by [soulmate](https://github.com/seatgeek/soulmate).
# You can check out some examples [here](https://github.com/FLOChip/flo/tree/master/examples).
_ = require "underscore"
async = require "async"

# Sets up a new Redis Connection.
#
# options - Optional Hash of options.
#
# * `redis`       - An existing redis connection to use.
# * `host`        - String Redis host.  (Default: Redis' default)
# * `port`        - Integer Redis port.  (Default: Redis' default)
# * `password`    - String Redis password.
# * `namespace`   - String namespace prefix for Redis keys.
#               (Default: flo).
# * `mincomplete` - Minimum completion of keys required for auto completion.
#               (Default: 1)
# * `database`    - Integer of the Redis database to select.
#
# Returns a Connection instance.
exports.connect = (options) ->
  new exports.Connection options || {}

# Handles the connection to the Redis server.
class Connection
  constructor: (options) ->
    @helper      = new Helper
    @redis       = options.redis       || connectToRedis options
    @namespace   = options.namespace   || 'flo'
    @mincomplete = options.mincomplete || 1
    @redis.select options.database if options.database?

  # Public: Get all prefixes for a phrase
  #
  # * `phrase` - the phrase that needs to be parsed into many prefixes
  #
  # Returns an array of unique prefixes for the phrase
  prefixes_for_phrase: (phrase) ->
    words = @helper.normalize(phrase).split(' ')
    _.uniq(
      _.flatten(
        _.map(words, (w) =>
          _.map([(@mincomplete-1)..(w.length-1)], (l) ->
            w[0..l]
          )
        )
      )
    )

  # Public: Search for a term
  #
  # * `types` - types of term that you are looking for (Array of String)
  # * `phrase` - the phrase or phrases you want to be autocompleted
  # * `limit` - the count of the number you want to return (optional, default: 5)
  # * `callback(err, result)` - err is the error and results is the results
  search_term: (types, phrase, args...) ->
    if typeof(args[0]) == 'number'
      limit = args[0]
    else
      limit = 5
    callback = args[args.length-1]

    async.map types, (type, callb) =>
      words = _.uniq(
        @helper.normalize(phrase).split(' ')
      ).sort()

      # for caching purpose
      cachekey = @key(type, "cache", words.join('|'))
      async.waterfall([
        ((cb) =>
          @redis.exists cachekey, cb
        ),
        ((exists, cb) =>
          if !exists
            interkeys = _.map(words, (w) =>
              @key(type, "index", w)
            )
            @redis.zinterstore cachekey, interkeys.length, interkeys..., (err, count) =>
              @redis.expire cachekey, 10 * 60, -> # expire after 10 minutes
                cb()
          else
            cb()
        ),
        ((cb) =>
          @redis.zrevrange cachekey, 0, (limit - 1), (err, ids) =>
            if ids.length > 0
              @redis.hmget @key(type, "data"), ids..., cb
            else
              cb(null, [])
        )
      ], (err, results) ->
        data = {}
        data[type] = results
        callb(err, data)
      )
    , (err, results) ->
      results = _.extend results...
      results.term = phrase
      callback(err, results)

  # Public: Add a new term
  #
  # * `type`     - the type of data of this term (String)
  # * `id`       - unique identifier(within the specific type)
  # * `term`     - the phrase you wish to provide completions for
  # * `score`    - user specified ranking metric (redis will order things lexicographically for items with the same score)
  # * `data`     - container for metadata that you would like to return when this item is matched (optional)
  # * `callback` - callback to be run (optional)
  #
  # Returns nothing.
  add_term: (type, id, term, score, args...) ->
    if typeof(args[0]) != 'function'
      data = args[0]
      callback = args[args.length-1]
    else if typeof(args[0]) == 'function'
      callback = args[0]

    # store the data in parallel
    async.parallel([
      ((callb) =>
        @redis.hset @key(type, "data"), id,
          JSON.stringify id: id, term: term, score: score, data: (data || []),
          ->
            callb()
      ),
      ((callb) =>
        async.forEach @prefixes_for_phrase(term),
        ((w, cb) =>
          @redis.zadd @key(type, "index", w), score, id, # sorted set
          -> cb()
        ), ->
          callb()
      ),
      ((callb) =>
        key = @key(type, @helper.normalize(term))
        # do we already have this term?
        @redis.get key, (err, result) =>
          if (err)
            return callb(err)

          if (result)
            # append to existing ids (without duplicates)
            arr = JSON.parse(result)
            arr.push(id)
            arr = _.uniq(arr)
          else
            arr = [id]

          # store the id
          @redis.set key, JSON.stringify(arr), callb
      )
    ], ->
      callback() if callback?
    )

  # Public: Remove a term
  #
  # * `type`     - the type of data of this term (String)
  # * `id`       - unique identifier (within the specific type)
  # * `callback(err)` - callback to be run (optional)
  #
  # Returns nothing.
  remove_term: (type, id, callback) ->
    #get the term
    @redis.hget @key(type, "data"), id,
      (err, result) =>
        if err
          return callback(err)
        if result == null
          return callback(new Error("Invalid term id"))

        term = JSON.parse(result).term

        # remove 
        async.parallel([
          ((callb) =>
            @redis.hdel @key(type, "data"), id, callb
          ),
          ((callb) =>
            async.forEach @prefixes_for_phrase(term),
            ((w, cb) =>
              @redis.zrem @key(type, "index", w), id,
              -> cb()
            ), callb
          ),
          ((callb) =>
            key = @key(type, @helper.normalize(term))
            @redis.get key, (err, result) =>
              if (err)
                return callb(err)

              if (result == null)
                return cb(new Error("Couldn't delete "+ id +". No such entry."))

              arr = JSON.parse(result)

              if (arr.toString() == [id].toString())
                # delete it
                return @redis.del key, callb

              @redis.set key, JSON.stringify(_.without(arr, id)), callb
          )
        ], (err) ->
          callback(err) if callback?
        )

  # Public: Returns an array of IDs for a term
  
  # * 'type'    - the type of data for this term
  # * 'term'    - the term to find the unique identifiers for
  # * 'callback(err, result)' - result is the ID for the term
  
  # Returns nothing.
  get_ids: (type, term, callback) ->
    @redis.get @key(type, @helper.normalize(term)), (err, result) ->
      if (err)
        return callback(err)

      arr = JSON.parse(result)

      if (arr == null)
        return callback(null, [])

      callback(null, arr)


  # Public: Returns the data for an ID
  
  # * 'type'    - the type of data for this term
  # * `id`       - unique identifier (within the specific type)
  # * 'callback(err, result)' - result is the data
  
  # Returns nothing.
  get_data: (type, id, callback) ->
    @redis.hget @key(type, "data"), id,
      (err, result) ->
        if err
          return callback(err)

        callback(null, JSON.parse(result))

  # Public: Get the redis instance
  #
  # Returns the redis instance.
  redis: ->
    @redis

  # Public: Quits the connection to the Redis server.
  #
  # Returns nothing.
  end: ->
    @redis.quit()

  # Builds a namespaced Redis key with the given arguments.
  #
  # * `type` - Type of the param
  # * `args` - Array of Strings.
  #
  # Returns an assembled String key.
  key: (args...) ->
    args.unshift @namespace
    args.join ":"

class Helper
  # Public: Normalize a term to remove all other characters than a-z and 0-9.
  #
  # * `term` - the term to be normalized
  #
  # Returns a normalized term.
  normalize: (term) ->
    @strip(@gsub(term.toLowerCase(), /[^a-z0-9 ]/i, ''))

  # Public: This function partially simulates the Ruby's String gsub method.
  #
  # * `source` - the source string
  # * `pattern` - the Regex pattern
  # * `replacement` - the replacement text
  #
  # Example:
  #
  #     gsub("-abc-abc-", /[^a-z0-9 ]/i, '')  # returns "abcabc"
  #     gsub("-abc-abc-", /[^a-z0-9 ]/i, '*') # returns "*abc*abc*"
  #
  # Returns the modified string.
  gsub: (source, pattern, replacement) ->
    unless pattern? and replacement?
      return source

    result = ''
    while source.length > 0
      if (match = source.match(pattern))
        result += source.slice(0, match.index)
        result += replacement
        source  = source.slice(match.index + match[0].length)
      else
        result += source
        source = ''

    result

  # Public: Strip out leading and trailing whitespaces.
  #
  # * `source` - string to be stripped
  #
  # Returns a copy of str with leading and trailing whitespace removed.
  strip: (source) ->
    source.replace(/^\s+/, '').replace(/\s+$/, '')

connectToRedis = (options) ->
  redis = require('redis').createClient options.port, options.host
  redis.auth options.password if options.password?
  redis

exports.Helper = new Helper
exports.Connection = Connection