var check = require('./util/check')
var isTypedArray = require('./util/is-typed-array')
var isNDArrayLike = require('./util/is-ndarray')
var values = require('./util/values')
var pool = require('./util/pool')
var flattenUtil = require('./util/flatten')

var arrayFlatten = flattenUtil.flatten
var arrayShape = flattenUtil.shape

var arrayTypes = require('./constants/arraytypes.json')
var bufferTypes = require('./constants/dtypes.json')
var usageTypes = require('./constants/usage.json')

var GL_STATIC_DRAW = 0x88E4
var GL_STREAM_DRAW = 0x88E0

var GL_UNSIGNED_BYTE = 5121
var GL_FLOAT = 5126

var DTYPES_SIZES = []
DTYPES_SIZES[5120] = 1 // int8
DTYPES_SIZES[5122] = 2 // int16
DTYPES_SIZES[5124] = 4 // int32
DTYPES_SIZES[5121] = 1 // uint8
DTYPES_SIZES[5123] = 2 // uint16
DTYPES_SIZES[5125] = 4 // uint32
DTYPES_SIZES[5126] = 4 // float32

function typedArrayCode (data) {
  return arrayTypes[Object.prototype.toString.call(data)] | 0
}

function copyArray (out, inp) {
  for (var i = 0; i < inp.length; ++i) {
    out[i] = inp[i]
  }
}

function transpose (
  result, data, shapeX, shapeY, strideX, strideY, offset) {
  var ptr = 0
  for (var i = 0; i < shapeX; ++i) {
    for (var j = 0; j < shapeY; ++j) {
      result[ptr++] = data[strideX * i + strideY * j + offset]
    }
  }
}

module.exports = function wrapBufferState (gl, stats, config, destroyBuffer) {
  var bufferCount = 0
  var bufferSet = {}

  function REGLBuffer (type) {
    this.id = bufferCount++
    this.buffer = gl.createBuffer()
    this.type = type
    this.usage = GL_STATIC_DRAW
    this.byteLength = 0
    this.dimension = 1
    this.dtype = GL_UNSIGNED_BYTE

    this.persistentData = null

    if (config.profile) {
      this.stats = { size: 0 }
    }
  }

  REGLBuffer.prototype.bind = function () {
    gl.bindBuffer(this.type, this.buffer)
  }

  REGLBuffer.prototype.destroy = function () {
    destroy(this)
  }

  var streamPool = []

  function createStream (type, data) {
    var buffer = streamPool.pop()
    if (!buffer) {
      buffer = new REGLBuffer(type)
    }
    buffer.bind()
    initBufferFromData(buffer, data, GL_STREAM_DRAW, 0, 1, false)
    return buffer
  }

  function destroyStream (stream) {
    streamPool.push(stream)
  }

  function initBufferFromTypedArray (buffer, data, usage) {
    buffer.byteLength = data.byteLength
    gl.bufferData(buffer.type, data, usage)
  }

  function initBufferFromData (buffer, data, usage, dtype, dimension, persist) {
    var shape
    buffer.usage = usage
    if (Array.isArray(data)) {
      buffer.dtype = dtype || GL_FLOAT
      if (data.length > 0) {
        var flatData
        if (Array.isArray(data[0])) {
          shape = arrayShape(data)
          var dim = 1
          for (var i = 1; i < shape.length; ++i) {
            dim *= shape[i]
          }
          buffer.dimension = dim
          flatData = arrayFlatten(data, shape, buffer.dtype)
          initBufferFromTypedArray(buffer, flatData, usage)
          if (persist) {
            buffer.persistentData = flatData
          } else {
            pool.freeType(flatData)
          }
        } else if (typeof data[0] === 'number') {
          buffer.dimension = dimension
          var typedData = pool.allocType(buffer.dtype, data.length)
          copyArray(typedData, data)
          initBufferFromTypedArray(buffer, typedData, usage)
          if (persist) {
            buffer.persistentData = typedData
          } else {
            pool.freeType(typedData)
          }
        } else if (isTypedArray(data[0])) {
          buffer.dimension = data[0].length
          buffer.dtype = dtype || typedArrayCode(data[0]) || GL_FLOAT
          flatData = arrayFlatten(
            data,
            [data.length, data[0].length],
            buffer.dtype)
          initBufferFromTypedArray(buffer, flatData, usage)
          if (persist) {
            buffer.persistentData = flatData
          } else {
            pool.freeType(flatData)
          }
        } else {
          check.raise('invalid buffer data')
        }
      }
    } else if (isTypedArray(data)) {
      buffer.dtype = dtype || typedArrayCode(data)
      buffer.dimension = dimension
      initBufferFromTypedArray(buffer, data, usage)
      if (persist) {
        buffer.persistentData = new Uint8Array(new Uint8Array(data.buffer))
      }
    } else if (isNDArrayLike(data)) {
      shape = data.shape
      var stride = data.stride
      var offset = data.offset

      var shapeX = 0
      var shapeY = 0
      var strideX = 0
      var strideY = 0
      if (shape.length === 1) {
        shapeX = shape[0]
        shapeY = 1
        strideX = stride[0]
        strideY = 0
      } else if (shape.length === 2) {
        shapeX = shape[0]
        shapeY = shape[1]
        strideX = stride[0]
        strideY = stride[1]
      } else {
        check.raise('invalid shape')
      }

      buffer.dtype = dtype || typedArrayCode(data.data) || GL_FLOAT
      buffer.dimension = shapeY

      var transposeData = pool.allocType(buffer.dtype, shapeX * shapeY)
      transpose(transposeData,
        data.data,
        shapeX, shapeY,
        strideX, strideY,
        offset)
      initBufferFromTypedArray(buffer, transposeData, usage)
      if (persist) {
        buffer.persistentData = transposeData
      } else {
        pool.freeType(transposeData)
      }
    } else if (data instanceof ArrayBuffer) {
      buffer.dtype = GL_UNSIGNED_BYTE
      buffer.dimension = dimension
      initBufferFromTypedArray(buffer, data, usage)
      if (persist) {
        buffer.persistentData = new Uint8Array(new Uint8Array(data))
      }
    } else {
      check.raise('invalid buffer data')
    }
  }

  function destroy (buffer) {
    stats.bufferCount--

    // remove attribute link
    destroyBuffer(buffer)

    var handle = buffer.buffer
    check(handle, 'buffer must not be deleted already')
    gl.deleteBuffer(handle)
    buffer.buffer = null
    delete bufferSet[buffer.id]
  }

  function createBuffer (options, type, deferInit, persistent) {
    stats.bufferCount++

    var buffer = new REGLBuffer(type)
    bufferSet[buffer.id] = buffer

    function reglBuffer (options) {
      var usage = GL_STATIC_DRAW
      var data = null
      var byteLength = 0
      var dtype = 0
      var dimension = 1
      if (Array.isArray(options) ||
          isTypedArray(options) ||
          isNDArrayLike(options) ||
          options instanceof ArrayBuffer) {
        data = options
      } else if (typeof options === 'number') {
        byteLength = options | 0
      } else if (options) {
        check.type(
          options, 'object',
          'buffer arguments must be an object, a number or an array')

        if ('data' in options) {
          check(
            data === null ||
            Array.isArray(data) ||
            isTypedArray(data) ||
            isNDArrayLike(data),
            'invalid data for buffer')
          data = options.data
        }

        if ('usage' in options) {
          check.parameter(options.usage, usageTypes, 'invalid buffer usage')
          usage = usageTypes[options.usage]
        }

        if ('type' in options) {
          check.parameter(options.type, bufferTypes, 'invalid buffer type')
          dtype = bufferTypes[options.type]
        }

        if ('dimension' in options) {
          check.type(options.dimension, 'number', 'invalid dimension')
          dimension = options.dimension | 0
        }

        if ('length' in options) {
          check.nni(byteLength, 'buffer length must be a nonnegative integer')
          byteLength = options.length | 0
        }
      }

      buffer.bind()
      if (!data) {
        // #475
        if (byteLength) gl.bufferData(buffer.type, byteLength, usage)
        buffer.dtype = dtype || GL_UNSIGNED_BYTE
        buffer.usage = usage
        buffer.dimension = dimension
        buffer.byteLength = byteLength
      } else {
        initBufferFromData(buffer, data, usage, dtype, dimension, persistent)
      }

      if (config.profile) {
        buffer.stats.size = buffer.byteLength * DTYPES_SIZES[buffer.dtype]
      }

      return reglBuffer
    }

    function setSubData (data, offset) {
      check(offset + data.byteLength <= buffer.byteLength,
        'invalid buffer subdata call, buffer is too small. ' + ' Can\'t write data of size ' + data.byteLength + ' starting from offset ' + offset + ' to a buffer of size ' + buffer.byteLength)

      gl.bufferSubData(buffer.type, offset, data)
    }

    function subdata (data, offset_) {
      var offset = (offset_ || 0) | 0
      var shape
      buffer.bind()
      if (isTypedArray(data) || data instanceof ArrayBuffer) {
        setSubData(data, offset)
      } else if (Array.isArray(data)) {
        if (data.length > 0) {
          if (typeof data[0] === 'number') {
            var converted = pool.allocType(buffer.dtype, data.length)
            copyArray(converted, data)
            setSubData(converted, offset)
            pool.freeType(converted)
          } else if (Array.isArray(data[0]) || isTypedArray(data[0])) {
            shape = arrayShape(data)
            var flatData = arrayFlatten(data, shape, buffer.dtype)
            setSubData(flatData, offset)
            pool.freeType(flatData)
          } else {
            check.raise('invalid buffer data')
          }
        }
      } else if (isNDArrayLike(data)) {
        shape = data.shape
        var stride = data.stride

        var shapeX = 0
        var shapeY = 0
        var strideX = 0
        var strideY = 0
        if (shape.length === 1) {
          shapeX = shape[0]
          shapeY = 1
          strideX = stride[0]
          strideY = 0
        } else if (shape.length === 2) {
          shapeX = shape[0]
          shapeY = shape[1]
          strideX = stride[0]
          strideY = stride[1]
        } else {
          check.raise('invalid shape')
        }
        var dtype = Array.isArray(data.data)
          ? buffer.dtype
          : typedArrayCode(data.data)

        var transposeData = pool.allocType(dtype, shapeX * shapeY)
        transpose(transposeData,
          data.data,
          shapeX, shapeY,
          strideX, strideY,
          data.offset)
        setSubData(transposeData, offset)
        pool.freeType(transposeData)
      } else {
        check.raise('invalid data for buffer subdata')
      }
      return reglBuffer
    }

    if (!deferInit) {
      reglBuffer(options)
    }

    reglBuffer._reglType = 'buffer'
    reglBuffer._buffer = buffer
    reglBuffer.subdata = subdata
    if (config.profile) {
      reglBuffer.stats = buffer.stats
    }
    reglBuffer.destroy = function () { destroy(buffer) }

    return reglBuffer
  }

  function restoreBuffers () {
    values(bufferSet).forEach(function (buffer) {
      buffer.buffer = gl.createBuffer()
      gl.bindBuffer(buffer.type, buffer.buffer)
      gl.bufferData(
        buffer.type, buffer.persistentData || buffer.byteLength, buffer.usage)
    })
  }

  if (config.profile) {
    stats.getTotalBufferSize = function () {
      var total = 0
      // TODO: Right now, the streams are not part of the total count.
      Object.keys(bufferSet).forEach(function (key) {
        total += bufferSet[key].stats.size
      })
      return total
    }
  }

  return {
    create: createBuffer,

    createStream: createStream,
    destroyStream: destroyStream,

    clear: function () {
      values(bufferSet).forEach(destroy)
      streamPool.forEach(destroy)
    },

    getBuffer: function (wrapper) {
      if (wrapper && wrapper._buffer instanceof REGLBuffer) {
        return wrapper._buffer
      }
      return null
    },

    restore: restoreBuffers,

    _initBuffer: initBufferFromData
  }
}