/* from npm's redis-info, adding missing avg_ttl */

const fromPairs = require('lodash.frompairs')
const find = require('lodash.find')
const has = require('lodash.has')

module.exports = {
  parse: function (info) {
    return parseFields(splitStr(info))
  }
}


function startWith(pattern) {
  return function (value) {
    return value.indexOf(pattern) === 0
  }
}


function split(s) {
  return function (v) {
    return v.split(s)
  }
}

function orEmptyStr(v) {
  return v || ''
}


function takeN(func, n) {
  return function (v) {
    return func(v[n])
  }
}

function takeFirst(func) {
  return takeN(func, 0)
}

/**
 * Split the info string by \n and :
 * @param  {String} str the returned redis info
 * @return {Array}     Array of [key, value]
 */
function splitStr(str) {
  return str.split('\n')
    .filter(function (line) {
      return line.length > 0 && line.indexOf('#') !== 0
    })
    .map(function (line) {
      return line.trim().split(':')
    })
}

function parseDatabases(info) {
  return info
    .filter(takeFirst(startWith('db')))
    .map(function _parseDatabaseInfo(args) {
      var dbName = args[0]
      var value = args[1]
      var values = orEmptyStr(value).split(',')
      console.log({values})

      function extract(param) {
        return parseInt(orEmptyStr(find(values, startWith(param))).split('=')[1] || 0, 10)
      }

      return {
        index: parseInt(dbName.substr(2), 10),
        keys: extract('keys'),
        expires: extract('expires'),
        avg_ttl: extract('avg_ttl'),
      }
    })
    .reduce(function (m, v) {
      m[v.index] = {
        keys: v.keys,
        expires: v.expires,
        avg_ttl: v.avg_ttl,
      }
      return m
    }, {})
}

function parseCommands(info) {
  return fromPairs(info.filter(function (a) {
      return orEmptyStr(a[0]).indexOf('cmdstat_') === 0
    })
    .map(function _parseCommands(args) {
      var v = args[0]
      var a = args[1]
      var val = fromPairs(orEmptyStr(a).split(',').map(split('=')))
      if (has(val, 'calls')) {
        val.calls = parseInt(val.calls, 10)
      }
      if (has(val, 'usec')) {
        val.usec = parseInt(val.usec, 10)
      }
      if (has(val, 'usec_per_call')) {
        val.usec_per_call = parseFloat(val.usec_per_call, 10)
      }
      return [orEmptyStr(v).split('_')[1], val]
    }))
}

function parseFields(info) {
  var fields = info.reduce(function (m, v) {
    if (!v[0].trim() || v[0].indexOf('db') === 0 ||  v[0].indexOf('cmdstat_') === 0) {
      return m
    }
    m[v[0]] = v[1]
    return m
  }, {
    databases: parseDatabases(info),
    commands: parseCommands(info)
  })

  return fields
}