package expo.modules.image.blurhash

import android.graphics.Bitmap
import android.graphics.Color
import kotlin.math.cos
import kotlin.math.pow
import kotlin.math.withSign

/**
 * Copied from https://github.com/woltapp/blurhash.
 */
object BlurhashDecoder {

  // cache Math.cos() calculations to improve performance.
  // The number of calculations can be huge for many bitmaps: width * height * numCompX * numCompY * 2 * nBitmaps
  // the cache is enabled by default, it is recommended to disable it only when just a few images are displayed
  private val cacheCosinesX = HashMap<Int, DoubleArray>()
  private val cacheCosinesY = HashMap<Int, DoubleArray>()

  /**
   * Clear calculations stored in memory cache.
   * The cache is not big, but will increase when many image sizes are used,
   * if the app needs memory it is recommended to clear it.
   */
  fun clearCache() {
    cacheCosinesX.clear()
    cacheCosinesY.clear()
  }

  /**
   * Decode a blur hash into a new bitmap.
   *
   * @param useCache use in memory cache for the calculated math, reused by images with same size.
   *                 if the cache does not exist yet it will be created and populated with new calculations.
   *                 By default it is true.
   */
  fun decode(blurHash: String?, width: Int, height: Int, punch: Float = 1f, useCache: Boolean = true): Bitmap? {
    if (blurHash == null || blurHash.length < 6) {
      return null
    }
    val numCompEnc = decode83(blurHash, 0, 1)
    val numCompX = (numCompEnc % 9) + 1
    val numCompY = (numCompEnc / 9) + 1
    if (blurHash.length != 4 + 2 * numCompX * numCompY) {
      return null
    }
    val maxAcEnc = decode83(blurHash, 1, 2)
    val maxAc = (maxAcEnc + 1) / 166f
    val colors = Array(numCompX * numCompY) { i ->
      if (i == 0) {
        val colorEnc = decode83(blurHash, 2, 6)
        decodeDc(colorEnc)
      } else {
        val from = 4 + i * 2
        val colorEnc = decode83(blurHash, from, from + 2)
        decodeAc(colorEnc, maxAc * punch)
      }
    }
    return composeBitmap(width, height, numCompX, numCompY, colors, useCache)
  }

  private fun decode83(str: String, from: Int = 0, to: Int = str.length): Int {
    var result = 0
    for (i in from until to) {
      val index = charMap[str[i]] ?: -1
      if (index != -1) {
        result = result * 83 + index
      }
    }
    return result
  }

  private fun decodeDc(colorEnc: Int): FloatArray {
    val r = colorEnc shr 16
    val g = (colorEnc shr 8) and 255
    val b = colorEnc and 255
    return floatArrayOf(BlurhashHelpers.srgbToLinear(r), BlurhashHelpers.srgbToLinear(g), BlurhashHelpers.srgbToLinear(b))
  }

  private fun decodeAc(value: Int, maxAc: Float): FloatArray {
    val r = value / (19 * 19)
    val g = (value / 19) % 19
    val b = value % 19
    return floatArrayOf(
      signedPow2((r - 9) / 9.0f) * maxAc,
      signedPow2((g - 9) / 9.0f) * maxAc,
      signedPow2((b - 9) / 9.0f) * maxAc
    )
  }

  private fun signedPow2(value: Float) = value.pow(2f).withSign(value)

  private fun composeBitmap(
    width: Int,
    height: Int,
    numCompX: Int,
    numCompY: Int,
    colors: Array<FloatArray>,
    useCache: Boolean
  ): Bitmap {
    // use an array for better performance when writing pixel colors
    val imageArray = IntArray(width * height)
    val calculateCosX = !useCache || !cacheCosinesX.containsKey(width * numCompX)
    val cosinesX = getArrayForCosinesX(calculateCosX, width, numCompX)
    val calculateCosY = !useCache || !cacheCosinesY.containsKey(height * numCompY)
    val cosinesY = getArrayForCosinesY(calculateCosY, height, numCompY)
    for (y in 0 until height) {
      for (x in 0 until width) {
        var r = 0f
        var g = 0f
        var b = 0f
        for (j in 0 until numCompY) {
          for (i in 0 until numCompX) {
            val cosX = cosinesX.getCos(calculateCosX, i, numCompX, x, width)
            val cosY = cosinesY.getCos(calculateCosY, j, numCompY, y, height)
            val basis = (cosX * cosY).toFloat()
            val color = colors[j * numCompX + i]
            r += color[0] * basis
            g += color[1] * basis
            b += color[2] * basis
          }
        }
        imageArray[x + width * y] = Color.rgb(linearToSrgb(r), linearToSrgb(g), linearToSrgb(b))
      }
    }
    return Bitmap.createBitmap(imageArray, width, height, Bitmap.Config.ARGB_8888)
  }

  private fun getArrayForCosinesY(calculate: Boolean, height: Int, numCompY: Int) = when {
    calculate -> {
      DoubleArray(height * numCompY).also {
        cacheCosinesY[height * numCompY] = it
      }
    }
    else -> {
      cacheCosinesY[height * numCompY]!!
    }
  }

  private fun getArrayForCosinesX(calculate: Boolean, width: Int, numCompX: Int) = when {
    calculate -> {
      DoubleArray(width * numCompX).also {
        cacheCosinesX[width * numCompX] = it
      }
    }
    else -> cacheCosinesX[width * numCompX]!!
  }

  private fun DoubleArray.getCos(
    calculate: Boolean,
    x: Int,
    numComp: Int,
    y: Int,
    size: Int
  ): Double {
    if (calculate) {
      this[x + numComp * y] = cos(Math.PI * y * x / size)
    }
    return this[x + numComp * y]
  }

  private fun linearToSrgb(value: Float): Int {
    val v = value.coerceIn(0f, 1f)
    return if (v <= 0.0031308f) {
      (v * 12.92f * 255f + 0.5f).toInt()
    } else {
      ((1.055f * v.pow(1 / 2.4f) - 0.055f) * 255 + 0.5f).toInt()
    }
  }

  private val charMap = listOf(
    '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F', 'G',
    'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X',
    'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o',
    'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '#', '$', '%', '*', '+', ',',
    '-', '.', ':', ';', '=', '?', '@', '[', ']', '^', '_', '{', '|', '}', '~'
  )
    .mapIndexed { i, c -> c to i }
    .toMap()
}