#! /usr/local/bin/Rscript

args <- commandArgs(TRUE)
.libPaths(args[1])
if(!file.exists(args[2]))
    stop("no previous snapshot")
nmax <- 250L
old <- readRDS(args[2])
old <- as.data.frame(old, stringsAsFactors = FALSE)
new <- installed.packages(args[1])[, c("Package", "Version")]
new <- as.data.frame(new, stringsAsFactors = FALSE)
both <- merge(old, new, by = "Package")
updated <- with(both, Package[Version.x != Version.y])
## new packages might be in Suggests
added <- setdiff(row.names(new), row.names(old))
## and removed packages might have (a few) dependents
removed <- setdiff(row.names(old), row.names(new))
if(!length(c(updated, added, removed))) {
    message("no changed packages")
    q("no")
}
cur <- gsub("[.]out", "", dir(dirname(args[2]), patt = "[.]out"))
foo <- character()
for (u in c(updated, added, removed)) {
    foo1 <- tools::dependsOnPkgs(u, , TRUE)
    foo2 <- c(foo1, tools::dependsOnPkgs(c(u, foo1), 'all', FALSE))
    foo2 <- intersect(foo2, cur)
    if(length(foo2) <= nmax) foo <- c(foo, foo2)
    else {
        foo1 <- tools::dependsOnPkgs(u, 'all', FALSE)
        foo1 <- intersect(foo1, cur)
	if(length(foo1) <= nmax) {
	    foo <- c(foo, foo1)
            message(sprintf("re-checking %d/%d revdeps of %s",
                            length(foo1), length(foo2), sQuote(u)))
	} else
            message(sprintf("not re-checking %d revdeps of %s",
                            length(foo2), sQuote(u)))
    }
}
foo <- sort(unique(foo))

if(length(foo)) {
    message ("re-checking ", paste(sQuote(foo), collapse =" "))
    unlink(file.path(dirname(args[2]), paste0(foo, ".*")))
} else
   message("no re-checking needed")