# .cCCalcLL = function(mCPByS, nGByCP, s, z, K, nS, nG, alpha, beta)
.cCSplitZ <- function(counts,
                      mCPByS,
                      nGByCP,
                      nCP,
                      s,
                      z,
                      K,
                      nS,
                      nG,
                      alpha,
                      beta,
                      zProb,
                      maxClustersToTry = 10,
                      minCell = 3) {

  ## Identify clusters to split
  zTa <- tabulate(z, K)
  zToSplit <- which(zTa >= minCell)
  zNonEmpty <- which(zTa > 0)

  if (length(zToSplit) == 0) {
    m <- paste0(
      date(),
      " .... Cluster sizes too small. No additional splitting was",
      " performed."
    )
    return(list(
      z = z,
      mCPByS,
      nGByCP,
      nCP = nCP,
      message = m
    ))
  }

  ## Loop through each split-able Z and perform split
  clustSplit <- vector("list", K)
  for (i in zToSplit) {
    clustLabel <- .celda_C(
      counts[, z == i],
      K = 2,
      zInitialize = "random",
      maxIter = 5,
      splitOnIter = -1,
      splitOnLast = FALSE,
      verbose = FALSE
    )
    clustSplit[[i]] <- celdaClusters(clustLabel)$z
  }

  ## Find second best assignment give current assignments for each cell
  zProb[cbind(seq(nrow(zProb)), z)] <- NA
  zSecond <- apply(zProb, 1, which.max)

  ## Set up initial variables
  zSplit <- matrix(NA,
    nrow = length(z),
    ncol = length(zToSplit) * maxClustersToTry
  )
  zSplitLl <- rep(NA, times = length(zToSplit) * maxClustersToTry)
  zSplitLl[1] <- .cCCalcLL(mCPByS, nGByCP, s, z, K, nS, nG, alpha, beta)
  zSplit[, 1] <- z

  ## Select worst clusters to test for reshuffling
  previousZ <- z
  llShuffle <- rep(NA, K)
  for (i in zNonEmpty) {
    ix <- z == i
    newZ <- z
    newZ[ix] <- zSecond[ix]

    p <- .cCReDecomposeCounts(counts, s, newZ, previousZ, nGByCP, K)
    nGByCP <- p$nGByCP
    mCPByS <- p$mCPByS
    llShuffle[i] <- .cCCalcLL(mCPByS, nGByCP, s, z, K, nS, nG, alpha, beta)
    previousZ <- newZ
  }
  zToShuffle <- utils::head(order(llShuffle, decreasing = TRUE, na.last = NA),
    n = maxClustersToTry
  )

  pairs <- c(NA, NA)
  splitIx <- 2
  for (i in zToShuffle) {
    otherClusters <- setdiff(zToSplit, i)

    for (j in otherClusters) {
      newZ <- z

      ## Assign cluster i to the next most similar cluster (excluding
      ## cluster j)
      ## as defined above by the correlation
      ixToMove <- z == i
      newZ[ixToMove] <- zSecond[ixToMove]

      ## Split cluster j according to the clustering defined above
      ixToSplit <- z == j
      newZ[ixToSplit] <- ifelse(clustSplit[[j]] == 1, j, i)

      p <- .cCReDecomposeCounts(counts, s, newZ, previousZ, nGByCP, K)
      nGByCP <- p$nGByCP
      mCPByS <- p$mCPByS

      ## Calculate likelihood of split
      zSplitLl[splitIx] <- .cCCalcLL(
        mCPByS,
        nGByCP,
        s,
        z,
        K,
        nS,
        nG,
        alpha,
        beta
      )
      zSplit[, splitIx] <- newZ
      splitIx <- splitIx + 1L
      previousZ <- newZ

      pairs <- rbind(pairs, c(i, j))
    }
  }

  select <- which.max(zSplitLl)

  if (select == 1) {
    m <- paste0(date(), " .... No additional splitting was performed.")
  } else {
    m <- paste0(
      date(),
      " .... Cluster ",
      pairs[select, 1],
      " was reassigned and cluster ",
      pairs[select, 2],
      " was split in two."
    )
  }

  p <- .cCReDecomposeCounts(counts, s, zSplit[, select], previousZ, nGByCP, K)
  return(list(
    z = zSplit[, select],
    mCPByS = p$mCPByS,
    nGByCP = p$nGByCP,
    nCP = p$nCP,
    message = m
  ))
}


# .cCGCalcLL = function(K, L, mCPByS, nTSByCP, nByG, nByTS, nGByTS,
# nS, nG, alpha, beta, delta, gamma)
.cCGSplitZ <- function(counts,
                       mCPByS,
                       nTSByC,
                       nTSByCP,
                       nByG,
                       nByTS,
                       nGByTS,
                       nCP,
                       s,
                       z,
                       K,
                       L,
                       nS,
                       nG,
                       alpha,
                       beta,
                       delta,
                       gamma,
                       zProb,
                       maxClustersToTry = 10,
                       minCell = 3) {

  ## Identify clusters to split
  zTa <- tabulate(z, K)
  zToSplit <- which(zTa >= minCell)
  zNonEmpty <- which(zTa > 0)

  if (length(zToSplit) == 0) {
    m <- paste0(
      date(),
      " .... Cluster sizes too small. No additional splitting was",
      " performed."
    )
    return(list(
      z = z,
      mCPByS = mCPByS,
      nTSByCP = nTSByCP,
      nCP = nCP,
      message = m
    ))
  }

  ## Loop through each split-able Z and perform split
  clustSplit <- vector("list", K)
  for (i in zToSplit) {
    clustLabel <- .celda_C(counts[, z == i],
      K = 2,
      zInitialize = "random",
      maxIter = 5,
      splitOnIter = -1,
      splitOnLast = FALSE,
      verbose = FALSE
    )
    clustSplit[[i]] <- celdaClusters(clustLabel)$z
  }

  ## Find second best assignment give current assignments for each cell
  zProb[cbind(seq(nrow(zProb)), z)] <- NA
  zSecond <- apply(zProb, 1, which.max)

  ## Set up initial variables
  zSplit <- matrix(NA,
    nrow = length(z),
    ncol = length(zToSplit) * maxClustersToTry
  )
  zSplitLl <- rep(NA, ncol = length(zToSplit) * maxClustersToTry)
  zSplitLl[1] <- .cCGCalcLL(
    K,
    L,
    mCPByS,
    nTSByCP,
    nByG,
    nByTS,
    nGByTS,
    nS,
    nG,
    alpha,
    beta,
    delta,
    gamma
  )
  zSplit[, 1] <- z

  ## Select worst clusters to test for reshuffling
  previousZ <- z
  llShuffle <- rep(NA, K)
  for (i in zNonEmpty) {
    ix <- z == i
    newZ <- z
    newZ[ix] <- zSecond[ix]

    p <- .cCReDecomposeCounts(nTSByC, s, newZ, previousZ, nTSByCP, K)
    nTSByCP <- p$nGByCP
    mCPByS <- p$mCPByS
    llShuffle[i] <- .cCGCalcLL(
      K,
      L,
      mCPByS,
      nTSByCP,
      nByG,
      nByTS,
      nGByTS,
      nS,
      nG,
      alpha,
      beta,
      delta,
      gamma
    )
    previousZ <- newZ
  }
  zToShuffle <- utils::head(order(llShuffle, decreasing = TRUE, na.last = NA),
    n = maxClustersToTry
  )


  pairs <- c(NA, NA)
  splitIx <- 2
  for (i in zToShuffle) {
    otherClusters <- setdiff(zToSplit, i)

    for (j in otherClusters) {
      newZ <- z

      ## Assign cluster i to the next most similar cluster (excluding
      ## cluster j)
      ## as defined above by the correlation
      ixToMove <- z == i
      newZ[ixToMove] <- zSecond[ixToMove]

      ## Split cluster j according to the clustering defined above
      ixToSplit <- z == j
      newZ[ixToSplit] <- ifelse(clustSplit[[j]] == 1, j, i)

      p <- .cCReDecomposeCounts(nTSByC, s, newZ, previousZ, nTSByCP, K)
      nTSByCP <- p$nGByCP
      mCPByS <- p$mCPByS

      ## Calculate likelihood of split
      zSplitLl[splitIx] <- .cCGCalcLL(
        K,
        L,
        mCPByS,
        nTSByCP,
        nByG,
        nByTS,
        nGByTS,
        nS,
        nG,
        alpha,
        beta,
        delta,
        gamma
      )
      zSplit[, splitIx] <- newZ
      splitIx <- splitIx + 1L
      previousZ <- newZ

      pairs <- rbind(pairs, c(i, j))
    }
  }

  select <- which.max(zSplitLl)

  if (select == 1) {
    m <- paste0(date(), " .... No additional splitting was performed.")
  } else {
    m <- paste0(
      date(),
      " .... Cluster ",
      pairs[select, 1],
      " was reassigned and cluster ",
      pairs[select, 2],
      " was split in two."
    )
  }

  p <- .cCReDecomposeCounts(
    nTSByC,
    s,
    zSplit[, select],
    previousZ,
    nTSByCP,
    K
  )
  return(list(
    z = zSplit[, select],
    mCPByS = p$mCPByS,
    nTSByCP = p$nGByCP,
    nCP = p$nCP,
    message = m
  ))
}


.cCGSplitY <- function(counts,
                       y,
                       mCPByS,
                       nGByCP,
                       nTSByC,
                       nTSByCP,
                       nByG,
                       nByTS,
                       nGByTS,
                       nCP,
                       s,
                       z,
                       K,
                       L,
                       nS,
                       nG,
                       alpha,
                       beta,
                       delta,
                       gamma,
                       yProb,
                       maxClustersToTry = 10,
                       KSubclusters = 10,
                       minCell = 3) {

  #########################
  ## First, the cell dimension of the original matrix will be reduced by
  ## splitting each z cluster into 'KSubclusters'.
  #########################

  ## This will not be as big as the original matrix (which can take a lot of
  ## time to process with large number of cells), but not as small as the
  ## 'nGByCP' with current z assignments

  zTa <- tabulate(z, K)
  zNonEmpty <- which(zTa > 0)
  tempZ <- rep(0, length(z))
  currentTopZ <- 0
  for (i in zNonEmpty) {
    ix <- z == i
    if (zTa[i] <= KSubclusters) {
      tempZ[ix] <- seq(currentTopZ + 1, currentTopZ + zTa[i])
    } else {
      clustLabel <- .celda_C(counts[, z == i],
        K = KSubclusters,
        zInitialize = "random",
        maxIter = 5,
        splitOnIter = -1,
        splitOnLast = FALSE,
        verbose = FALSE
      )
      tempZ[ix] <- celdaClusters(clustLabel)$z + currentTopZ
    }
    currentTopZ <- max(tempZ, na.rm = TRUE)
  }

  ## Decompose counts according to new/temp z labels
  tempNGByCP <- .colSumByGroup(counts, group = tempZ, K = currentTopZ)

  #########################
  ## Second, different y splits will be estimated and tested
  #########################

  ## Identify clusters to split
  yTa <- tabulate(y, L)
  yToSplit <- which(yTa >= minCell)
  yNonEmpty <- which(yTa > 0)

  if (length(yToSplit) == 0) {
    m <- paste0(
      date(),
      " .... Cluster sizes too small. No additional splitting was",
      " performed."
    )
    return(list(
      y = y,
      mCPByS = mCPByS,
      nTSByCP = nTSByCP,
      nCP = nCP,
      message = m
    ))
  }

  ## Loop through each split-able Z and perform split
  clustSplit <- vector("list", L)
  for (i in yToSplit) {
    clustLabel <- .celda_G(tempNGByCP[y == i, ],
      L = 2,
      yInitialize = "random",
      maxIter = 5,
      splitOnIter = -1,
      splitOnLast = FALSE,
      verbose = FALSE
    )
    clustSplit[[i]] <- celdaClusters(clustLabel)$y
  }

  ## Find second best assignment give current assignments for each cell
  yProb[cbind(seq(nrow(yProb)), y)] <- NA
  ySecond <- apply(yProb, 1, which.max)

  ## Set up initial variables
  ySplit <- matrix(NA,
    nrow = length(y),
    ncol = length(yToSplit) * maxClustersToTry
  )
  ySplitLl <- rep(NA, ncol = length(yToSplit) * maxClustersToTry)
  ySplitLl[1] <- .cCGCalcLL(
    K,
    L,
    mCPByS,
    nTSByCP,
    nByG,
    nByTS,
    nGByTS,
    nS,
    nG,
    alpha,
    beta,
    delta,
    gamma
  )
  ySplit[, 1] <- y

  ## Select worst clusters to test for reshuffling
  previousY <- y
  llShuffle <- rep(NA, L)
  for (i in yNonEmpty) {
    ix <- y == i
    newY <- y
    newY[ix] <- ySecond[ix]

    p <- .cGReDecomposeCounts(nGByCP, newY, previousY, nTSByCP, nByG, L)
    nTSByCP <- p$nTSByC
    nByTS <- p$nByTS
    nGByTS <- p$nGByTS

    llShuffle[i] <- .cCGCalcLL(
      K,
      L,
      mCPByS,
      nTSByCP,
      nByG,
      nByTS,
      nGByTS,
      nS,
      nG,
      alpha,
      beta,
      delta,
      gamma
    )
    previousY <- newY
  }
  yToShuffle <- utils::head(order(llShuffle, decreasing = TRUE, na.last = NA),
    n = maxClustersToTry
  )

  pairs <- c(NA, NA)
  splitIx <- 2
  for (i in yToShuffle) {
    otherClusters <- setdiff(yToSplit, i)

    for (j in otherClusters) {
      newY <- y

      ## Assign cluster i to the next most similar cluster (excluding
      ## cluster j)
      ## as defined above by the correlation
      ixToMove <- y == i
      newY[ixToMove] <- ySecond[ixToMove]

      ## Split cluster j according to the clustering defined above
      ixToSplit <- y == j
      newY[ixToSplit] <- ifelse(clustSplit[[j]] == 1, j, i)

      p <- .cGReDecomposeCounts(nGByCP, newY, previousY, nTSByCP, nByG, L)
      nTSByCP <- p$nTSByC
      nByTS <- p$nByTS
      nGByTS <- p$nGByTS

      ## Calculate likelihood of split
      ySplitLl[splitIx] <- .cCGCalcLL(
        K,
        L,
        mCPByS,
        nTSByCP,
        nByG,
        nByTS,
        nGByTS,
        nS,
        nG,
        alpha,
        beta,
        delta,
        gamma
      )
      ySplit[, splitIx] <- newY
      splitIx <- splitIx + 1L
      previousY <- newY

      pairs <- rbind(pairs, c(i, j))
    }
  }

  select <- which.max(ySplitLl)

  if (select == 1) {
    m <- paste0(date(), " .... No additional splitting was performed.")
  } else {
    m <- paste0(
      date(),
      " .... Cluster ",
      pairs[select, 1],
      " was reassigned and cluster ",
      pairs[select, 2],
      " was split in two."
    )
  }

  p <- .cGReDecomposeCounts(
    nGByCP,
    ySplit[, select],
    previousY,
    nTSByCP,
    nByG,
    L
  )
  return(list(
    y = ySplit[, select],
    nTSByCP = p$nTSByC,
    nByTS = p$nByTS,
    nGByTS = p$nGByTS,
    message = m
  ))
}


# .cGCalcLL = function(nTSByC, nByTS, nByG, nGByTS, nM, nG, L, beta, delta,
# gamma) {
.cGSplitY <- function(counts,
                      y,
                      nTSByC,
                      nByTS,
                      nByG,
                      nGByTS,
                      nM,
                      nG,
                      L,
                      beta,
                      delta,
                      gamma,
                      yProb,
                      minFeature = 3,
                      maxClustersToTry = 10) {

  ## Identify clusters to split
  yTa <- table(factor(y, levels = seq(L)))
  yToSplit <- which(yTa >= minFeature)
  yNonEmpty <- which(yTa > 0)

  if (length(yToSplit) == 0) {
    m <- paste0(
      date(),
      " .... Cluster sizes too small. No additional splitting was",
      " performed."
    )
    return(list(
      y = y,
      nTSByC = nTSByC,
      nByTS = nByTS,
      nGByTS = nGByTS,
      message = m
    ))
  }

  ## Loop through each split-able y and find best split
  clustSplit <- vector("list", L)
  for (i in yToSplit) {
    clustLabel <- .celda_G(counts[y == i, ],
      L = 2,
      yInitialize = "random",
      maxIter = 5,
      splitOnIter = -1,
      splitOnLast = FALSE,
      verbose = FALSE
    )
    clustSplit[[i]] <- celdaClusters(clustLabel)$y
  }

  ## Find second best assignment give current assignments for each cell
  yProb[cbind(seq(nrow(yProb)), y)] <- NA
  ySecond <- apply(yProb, 1, which.max)

  ## Set up initial variables
  ySplit <- matrix(NA,
    nrow = length(y),
    ncol = length(yToSplit) * maxClustersToTry
  )
  ySplitLl <- rep(NA, ncol = length(yToSplit) * maxClustersToTry)
  ySplitLl[1] <- .cGCalcLL(
    nTSByC,
    nByTS,
    nByG,
    nGByTS,
    nM,
    nG,
    L,
    beta,
    delta,
    gamma
  )
  ySplit[, 1] <- y

  ## Select worst clusters to test for reshuffling
  llShuffle <- rep(NA, L)
  previousY <- y
  for (i in yNonEmpty) {
    ix <- y == i
    newY <- y
    newY[ix] <- ySecond[ix]
    p <- .cGReDecomposeCounts(counts, newY, previousY, nTSByC, nByG, L)
    llShuffle[i] <- .cGCalcLL(
      p$nTSByC,
      p$nByTS,
      nByG,
      p$nGByTS,
      nM,
      nG,
      L,
      beta,
      delta,
      gamma
    )
    previousY <- newY
  }
  yToShuffle <- utils::head(order(llShuffle, decreasing = TRUE, na.last = NA),
    n = maxClustersToTry
  )

  pairs <- c(NA, NA)
  splitIx <- 2
  for (i in yToShuffle) {
    otherClusters <- setdiff(yToSplit, i)

    for (j in otherClusters) {
      newY <- y

      ## Assign cluster i to the next most similar cluster (excluding
      ## cluster j)
      ## as defined above by the spearman correlation
      ixToMove <- y == i
      newY[ixToMove] <- ySecond[ixToMove]

      ## Split cluster j according to the clustering defined above
      ixToSplit <- y == j
      newY[ixToSplit] <- ifelse(clustSplit[[j]] == 1, j, i)

      ## Calculate likelihood of split
      p <- .cGReDecomposeCounts(counts, newY, previousY, nTSByC, nByG, L)
      ySplitLl[splitIx] <- .cGCalcLL(
        p$nTSByC,
        p$nByTS,
        nByG,
        p$nGByTS,
        nM,
        nG,
        L,
        beta,
        delta,
        gamma
      )
      ySplit[, splitIx] <- newY
      splitIx <- splitIx + 1L
      previousY <- newY

      pairs <- rbind(pairs, c(i, j))
    }
  }

  select <- which.max(ySplitLl)

  if (select == 1) {
    m <- paste0(date(), " .... No additional splitting was performed.")
  } else {
    m <- paste0(
      date(),
      " .... Cluster ",
      pairs[select, 1],
      " was reassigned and cluster ",
      pairs[select, 2],
      " was split in two."
    )
  }

  p <- .cGReDecomposeCounts(
    counts,
    ySplit[, select],
    previousY,
    nTSByC,
    nByG,
    L
  )
  return(list(
    y = ySplit[, select],
    nTSByC = p$nTSByC,
    nByTS = p$nByTS,
    nGByTS = p$nGByTS,
    message = m
  ))
}