/*
CSV Generate - main module

Please look at the [project documentation](https://csv.js.org/generate/) for
additional information.
*/

const stream = require('stream')
const util = require('util')

module.exports = function(){
  let options
  let callback
  if(arguments.length === 2){
    options = arguments[0]
    callback = arguments[1]
  }else if(arguments.length === 1){
    if(typeof arguments[0] === 'function'){
      options = {}
      callback = arguments[0]
    }else{
      options = arguments[0]
    }
  }else if(arguments.length === 0){
    options = {}
  }
  const generator = new Generator(options)
  if(callback){
    const data = []
    generator.on('readable', function(){
      let d; while(d = generator.read()){
        data.push(d)
      }
    })
    generator.on('error', callback)
    generator.on('end', function(){
      if(generator.options.objectMode){
        callback(null, data)
      }else{
        if(generator.options.encoding){
          callback(null, data.join(''))
        }else{
          callback(null, Buffer.concat(data))
        }
      }
    })
  }
  return generator
}

Generator = function(options = {}){
  // Convert Stream Readable options if underscored
  if(options.high_water_mark){
    options.highWaterMark = options.high_water_mark
  }
  if(options.object_mode){
    options.objectMode = options.object_mode
  }
  // Call parent constructor
  stream.Readable.call(this, options)
  // Clone and camelize options
  this.options = {}
  for(let k in options){
    this.options[Generator.camelize(k)] = options[k]
  }
  // Normalize options
  const dft = {
    columns: 8,
    delimiter: ',',
    duration: null,
    encoding: null,
    end: null,
    eof: false,
    fixedSize: false,
    length: -1,
    maxWordLength: 16,
    rowDelimiter: '\n',
    seed: false,
    sleep: 0,
  }
  for(const k in dft){
    if(this.options[k] === undefined){
      this.options[k] = dft[k]
    }
  }
  // Default values
  if(this.options.eof === true){
    this.options.eof = this.options.rowDelimiter
  }
  // State
  this._ = {
    start_time: this.options.duration ? Date.now() : null,
    fixed_size_buffer: '',
    count_written: 0,
    count_created: 0,
  }
  if(typeof this.options.columns === 'number'){
    this.options.columns = new Array(this.options.columns)
  }
  const accepted_header_types = Object.keys(Generator).filter( (t) => ( !['super_', 'camelize'].includes(t) ))
  for(let i = 0; i < this.options.columns.length; i++){
    const v = this.options.columns[i] || 'ascii'
    if(typeof v === 'string'){
      if(!accepted_header_types.includes(v)){
        throw Error(`Invalid column type: got "${v}", default values are ${JSON.stringify(accepted_header_types)}`)
      }
      this.options.columns[i] = Generator[v]
    }
  }
  return this
}
util.inherits(Generator, stream.Readable)
// Export the class
module.exports.Generator = Generator
// Generate a random number between 0 and 1 with 2 decimals. The function is idempotent if it detect the "seed" option.
Generator.prototype.random = function(){
  if(this.options.seed){
    return this.options.seed = this.options.seed * Math.PI * 100 % 100 / 100
  }else{
    return Math.random()
  }
}
// Stop the generation.
Generator.prototype.end = function(){
  this.push(null)
}
// Put new data into the read queue.
Generator.prototype._read = function(size){
  // Already started
  const data = []
  let length = this._.fixed_size_buffer.length
  if(length !== 0){
    data.push(this._.fixed_size_buffer)
  }
  while(true){
    // Time for some rest: flush first and stop later
    if( (this._.count_created === this.options.length) || (this.options.end && Date.now() > this.options.end) || (this.options.duration && Date.now() > this._.start_time + this.options.duration) ){
      // Flush
      if(data.length){
        if(this.options.objectMode){
          for(const line of data){
            this.__push(line)
          }
        }else{
          this.__push(data.join('') + (this.options.eof ? this.options.eof : ''))
        }
      }
      // Stop
      return this.push(null)
    }
    // Create the line
    let line = []
    let lineLength
    this.options.columns.forEach((fn) => {
      line.push(fn(this))
    })
    // for(const header in this.options.columns){
    //   // Create the field
    //   line.push(header(this))
    // }
    // Obtain line length
    if(this.options.objectMode){
      lineLength = 0
      for(const column of line)
        lineLength += column.length
    }else{
      // Stringify the line
      line = (this._.count_created === 0 ? '' : this.options.rowDelimiter)+line.join(this.options.delimiter)
      lineLength = line.length
    }
    this._.count_created++
    if(length + lineLength > size){
      if(this.options.objectMode){
        data.push(line)
        for(const line of data){
          this.__push(line)
        }
      }else{
        if(this.options.fixedSize){
          this._.fixed_size_buffer = line.substr(size - length)
          data.push(line.substr(0, size - length))
        }else{
          data.push(line)
        }
        this.__push(data.join(''))
      }
      return
    }
    length += lineLength
    data.push(line)
  }
}
// Put new data into the read queue.
Generator.prototype.__push = function(record){
  this._.count_written++
  if(this.options.sleep > 0){
    setTimeout( () => {
      this.push(record)
    }, this.options.sleep)
  }else{
    this.push(record)
  }
}
// Generate an ASCII value.
Generator.ascii = function(gen){
  // Column
  const column = []
  const nb_chars = Math.ceil(gen.random() * gen.options.maxWordLength)
  for(let i=0; i<nb_chars; i++){
    const char = Math.floor(gen.random() * 32)
    column.push(String.fromCharCode(char + (char < 16 ? 65 : 97 - 16)))
  }
  return column.join('')
}
// Generate an integer value.
Generator.int = function(gen){
  return Math.floor(gen.random() * Math.pow(2, 52))
}
// Generate an boolean value.
Generator.bool = function(gen){
  return Math.floor(gen.random() * 2)
}
// Camelize option properties
Generator.camelize = function(str){
  return str.replace(/_([a-z])/gi, function(_, match, index){
    return match.toUpperCase()
  })
}