# 1. Generate temporary Excel files ----

# Make a temporary spreadsheet with named sheets
make_temp_xlsx <- function(sheet_names) {
  wb <- openxlsx2::wb_workbook()
  for (sheet in sheet_names) wb <- wb |> openxlsx2::wb_add_worksheet(sheet)
  temp <- openxlsx::temp_xlsx()
  openxlsx2::wb_save(wb, temp)
}

# Make multiple spreadsheets, some sheet names vary
purrr::walk(
  list(LETTERS[1:3], LETTERS[1:3], LETTERS[1:4], LETTERS[1:5]),
  make_temp_xlsx
)

# Get the full paths to these temporary files
files <- list.files(tempdir(), ".xlsx", full.names = TRUE)

# 2. Compare all pairs of vectors, return differences ----

# Compare between all vector pairings, identify differences
compare_listed_vectors <- function(l) {
  
  pairs <- expand.grid(names(l), names(l))  # assuming l is named
  pairs <- pairs[with(pairs, which(Var1 != Var2)), ]  # don't compare self
  
  for (i in seq(nrow(pairs))) {
    vec1 <- pairs[i, 1]
    vec2 <- pairs[i, 2]
    diffs <- setdiff(l[[vec1]], l[[vec2]])
    diffs <- if (length(diffs) == 0) list(NULL) else list(diffs)
    pairs[i, "diffs"] <- list(diffs)
  }
  
  setNames(pairs, c("vec_a", "vec_b", "diffs"))  # a data.frame
  
}

# 3. Compare vectors ----

# List of sheet names, elements named after the file
l <- lapply(files, readxl::excel_sheets) |> setNames(basename(files))

# Output a data.frame with listcol of differences
compare_listed_vectors(l)  

# Clean up temp files
unlink(files)