library(igraph)
library(purrr)

consolidate_names <- function(graphs, prefix = "V") {
  have_names <- map_lgl(graphs, function(g) "name" %in% vertex_attr_names(g))
  if (all(have_names)) {
    all_names <- list_c(map(graphs, function(g) V(g)$name))

    if (any(duplicated(all_names))) {
      cli::cli_abort("Duplicated vertex names found across graphs.")
    }
    return(graphs)
  }

  existing_names <- list_c(map(graphs, function(g) V(g)$name))

  # Create a counter for generating new names (check if named graph already has generic names)
  name_counter <- if (any(grepl(paste0(prefix, "[0-9]+"), existing_names))) {
    max(as.integer(gsub(paste0(prefix, "([0-9]+)"), "\\1", existing_names)), na.rm = TRUE) + 1
  } else {
    1
  }

  for (i in seq_along(graphs)) {
    if (!have_names[i]) {
      n <- vcount(graphs[[i]])
      num_id <- seq(name_counter, length.out = n)
      V(graphs[[i]])$name <- paste0(prefix, num_id)
      name_counter <- name_counter + n + 1
    }
  }

  return(graphs)
}

g1 <- g2 <- make_ring(4)
V(g1)$name <- c("A", "B", "C", "D")
graphs <- list(g1, g2)
consolidate_names(graphs)
#> [[1]]
#> IGRAPH 467efa4 UN-- 4 4 -- Ring graph
#> + attr: name (g/c), mutual (g/l), circular (g/l), name (v/c)
#> + edges from 467efa4 (vertex names):
#> [1] A--B B--C C--D A--D
#> 
#> [[2]]
#> IGRAPH 467efa4 UN-- 4 4 -- Ring graph
#> + attr: name (g/c), mutual (g/l), circular (g/l), name (v/c)
#> + edges from 467efa4 (vertex names):
#> [1] V1--V2 V2--V3 V3--V4 V1--V4

V(g1)$name <- c("V1", "V2", "V3", "V4")
graphs <- list(g1, g2)
consolidate_names(graphs)
#> [[1]]
#> IGRAPH 467efa4 UN-- 4 4 -- Ring graph
#> + attr: name (g/c), mutual (g/l), circular (g/l), name (v/c)
#> + edges from 467efa4 (vertex names):
#> [1] V1--V2 V2--V3 V3--V4 V1--V4
#> 
#> [[2]]
#> IGRAPH 467efa4 UN-- 4 4 -- Ring graph
#> + attr: name (g/c), mutual (g/l), circular (g/l), name (v/c)
#> + edges from 467efa4 (vertex names):
#> [1] V5--V6 V6--V7 V7--V8 V5--V8