'use strict'

var bsearch   = require('binary-search-bounds')
var m4interp  = require('mat4-interpolate')
var invert44  = require('gl-mat4/invert')
var rotateX   = require('gl-mat4/rotateX')
var rotateY   = require('gl-mat4/rotateY')
var rotateZ   = require('gl-mat4/rotateZ')
var lookAt    = require('gl-mat4/lookAt')
var translate = require('gl-mat4/translate')
var scale     = require('gl-mat4/scale')
var normalize = require('gl-vec3/normalize')

var DEFAULT_CENTER = [0,0,0]

module.exports = createMatrixCameraController

function MatrixCameraController(initialMatrix) {
  this._components    = initialMatrix.slice()
  this._time          = [0]
  this.prevMatrix     = initialMatrix.slice()
  this.nextMatrix     = initialMatrix.slice()
  this.computedMatrix = initialMatrix.slice()
  this.computedInverse = initialMatrix.slice()
  this.computedEye    = [0,0,0]
  this.computedUp     = [0,0,0]
  this.computedCenter = [0,0,0]
  this.computedRadius = [0]
  this._limits        = [-Infinity, Infinity]
}

var proto = MatrixCameraController.prototype

proto.recalcMatrix = function(t) {
  var time = this._time
  var tidx = bsearch.le(time, t)
  var mat = this.computedMatrix
  if(tidx < 0) {
    return
  }
  var comps = this._components
  if(tidx === time.length-1) {
    var ptr = 16*tidx
    for(var i=0; i<16; ++i) {
      mat[i] = comps[ptr++]
    }
  } else {
    var dt = (time[tidx+1] - time[tidx])
    var ptr = 16*tidx
    var prev = this.prevMatrix
    var allEqual = true
    for(var i=0; i<16; ++i) {
      prev[i] = comps[ptr++]
    }
    var next = this.nextMatrix
    for(var i=0; i<16; ++i) {
      next[i] = comps[ptr++]
      allEqual = allEqual && (prev[i] === next[i])
    }
    if(dt < 1e-6 || allEqual) {
      for(var i=0; i<16; ++i) {
        mat[i] = prev[i]
      }
    } else {
      m4interp(mat, prev, next, (t - time[tidx])/dt)
    }
  }

  var up = this.computedUp
  up[0] = mat[1]
  up[1] = mat[5]
  up[2] = mat[9]
  normalize(up, up)

  var imat = this.computedInverse
  invert44(imat, mat)
  var eye = this.computedEye
  var w = imat[15]
  eye[0] = imat[12]/w
  eye[1] = imat[13]/w
  eye[2] = imat[14]/w

  var center = this.computedCenter
  var radius = Math.exp(this.computedRadius[0])
  for(var i=0; i<3; ++i) {
    center[i] = eye[i] - mat[2+4*i] * radius
  }
}

proto.idle = function(t) {
  if(t < this.lastT()) {
    return
  }
  var mc = this._components
  var ptr = mc.length-16
  for(var i=0; i<16; ++i) {
    mc.push(mc[ptr++])
  }
  this._time.push(t)
}

proto.flush = function(t) {
  var idx = bsearch.gt(this._time, t) - 2
  if(idx < 0) {
    return
  }
  this._time.splice(0, idx)
  this._components.splice(0, 16*idx)
}

proto.lastT = function() {
  return this._time[this._time.length-1]
}

proto.lookAt = function(t, eye, center, up) {
  this.recalcMatrix(t)
  eye    = eye || this.computedEye
  center = center || DEFAULT_CENTER
  up     = up || this.computedUp
  this.setMatrix(t, lookAt(this.computedMatrix, eye, center, up))
  var d2 = 0.0
  for(var i=0; i<3; ++i) {
    d2 += Math.pow(center[i] - eye[i], 2)
  }
  d2 = Math.log(Math.sqrt(d2))
  this.computedRadius[0] = d2
}

proto.rotate = function(t, yaw, pitch, roll) {
  this.recalcMatrix(t)
  var mat = this.computedInverse
  if(yaw)   rotateY(mat, mat, yaw)
  if(pitch) rotateX(mat, mat, pitch)
  if(roll)  rotateZ(mat, mat, roll)
  this.setMatrix(t, invert44(this.computedMatrix, mat))
}

var tvec = [0,0,0]

proto.pan = function(t, dx, dy, dz) {
  tvec[0] = -(dx || 0.0)
  tvec[1] = -(dy || 0.0)
  tvec[2] = -(dz || 0.0)
  this.recalcMatrix(t)
  var mat = this.computedInverse
  translate(mat, mat, tvec)
  this.setMatrix(t, invert44(mat, mat))
}

proto.translate = function(t, dx, dy, dz) {
  tvec[0] = dx || 0.0
  tvec[1] = dy || 0.0
  tvec[2] = dz || 0.0
  this.recalcMatrix(t)
  var mat = this.computedMatrix
  translate(mat, mat, tvec)
  this.setMatrix(t, mat)
}

proto.setMatrix = function(t, mat) {
  if(t < this.lastT()) {
    return
  }
  this._time.push(t)
  for(var i=0; i<16; ++i) {
    this._components.push(mat[i])
  }
}

proto.setDistance = function(t, d) {
  this.computedRadius[0] = d
}

proto.setDistanceLimits = function(a,b) {
  var lim = this._limits
  lim[0] = a
  lim[1] = b
}

proto.getDistanceLimits = function(out) {
  var lim = this._limits
  if(out) {
    out[0] = lim[0]
    out[1] = lim[1]
    return out
  }
  return lim
}

function createMatrixCameraController(options) {
  options = options || {}
  var matrix = options.matrix || 
              [1,0,0,0,
               0,1,0,0,
               0,0,1,0,
               0,0,0,1]
  return new MatrixCameraController(matrix)
}