load_embedding <- function(file_path){

    # load full file
    lines <- readLines(file_path)

    # create new environment
    embeddings_env <- new.env(hash = TRUE, parent = emptyenv())

    # this function is used to convert vectors to unit vectors
    # by dividing their components by vector length
    normalize_vector <- function(a){
        a/sqrt(sum(a**2))
    }

    # iterate through the whole file line by line
    for (i in 1:length(lines)) {
        line <- lines[[i]]
        values <- strsplit(line, " ")[[1]]
        label <- values[[1]]
        embeddings_env[[label]] <- normalize_vector(as.double(values[-1]))
    }

    embeddings_env
}

cosine_similarity <- function(a,b){
    # assuming unit vectors
    # the cosine is just the dot-product
    a %*% b
}


most_similar <- function(embeddings, ref_item, n_top = 10){
    # calculate cos similarity to ref_item for all elements
    cos_sims <- eapply(embeddings, cosine_similarity, b = ref_item)

    # only look at cos values smaller than 1
    # this will ignore the same element
    cos_sims <- cos_sims[cos_sims < 1]

    # return top elements
    cos_sims[order(unlist(cos_sims),decreasing=TRUE)][1:n_top]
}