# load sparse matrix package
suppressPackageStartupMessages(library("Matrix"))

# access a numeric column
get_numeric <- function(table, column_key) {
    column <- as.numeric(column_key)
    column_data <- suppressWarnings(as.numeric(as.character(table[column][[1]])))
    return(c(column_data))
}

# access a label column
get_label <- function(table, column_key) {
    column <- as.numeric(column_key)
    column_data <- as.character(table[column][[1]])
    return(c(column_data))
}

# inflate three columns into matrix
matrify <- function(data) {
    if (ncol(data) != 3)
        stop("Data frame must have three column format")
    plt <- data[, 1]
    spc <- data[, 2]
    abu <- data[, 3]
    plt_codes <- levels(factor(plt))
    spc_codes <- levels(factor(spc))
    taxa <- Matrix(0, nrow = length(plt_codes), ncol = length(spc_codes), sparse = TRUE)
    row <- match(plt, plt_codes)
    col <- match(spc, spc_codes)
    for (i in seq_len(length(abu))) {
        taxa[row[i], col[i]] <- abu[i]
    }
    colnames(taxa) <- spc_codes
    rownames(taxa) <- plt_codes
    taxa
}

# flatten data.frame into three column format
flatten <- function(my_matrix) {
    summ <- summary(my_matrix)
    summ <- data.frame(i = rownames(my_matrix)[summ$i], j = colnames(my_matrix)[summ$j], x = summ$x)
    summ
}

# wrapper
wrapper <- function(table, columns, options) {

    # initialize output list
    l <- list()

    # get number of columns
    n <- length(columns)

    # consistency check
    if (n %% 3 != 0) {
        print("heatmap::wrapper() - Data not consistent (n mod 3 != 0)")
        return(l)
    }

    # create index sequence
    index <- seq(1, n, by = 3)

    # get keys
    keys <- names(columns)

    # loop through blocks
    for (i in index) {
        # create columns
        ci <- get_label(table, columns[keys[i]])
        cj <- get_label(table, columns[keys[i + 1]])
        cx <- get_numeric(table, columns[keys[i + 2]])

        # create a frame from columns
        my_frame <- data.frame(ci = ci, cj = cj, cx = cx)

        # create matrix out of the frame
        my_matrix <- matrify(my_frame)

        # create/cluster matrix
        row_order <- hclust(dist(my_matrix))$order
        col_order <- hclust(dist(t(my_matrix)))$order

        # reorder matrix
        my_matrix <- my_matrix[row_order, col_order]

        # transform back to three columns
        my_flatmatrix <- flatten(my_matrix)

        # append to result list
        l <- append(l, list(my_flatmatrix$i))
        l <- append(l, list(my_flatmatrix$j))
        l <- append(l, list(my_flatmatrix$x))
    }

    # return
    return(l)
}