## Code in public domain
## If you have questions about how to use this code,
## or if you want to suggest improvement, feel free to email me to
## francois.michonneau@gmail.com

## 'add.zeros' adds zeros to match a given length
## for instance add.zeros(4, 3) returns '004'.
add.zeros <- function(x, final.length) {
    zeros.to.add <- character(0)
    nb.zeros <- final.length - nchar(x)
    if(nb.zeros < 0) {
        stop("Final length must be positive")
    }
    else {
        if(nb.zeros == 0) {
            return(x)
        }
        else {
            for(i in 1:nb.zeros) {
                zeros.to.add <- paste(zeros.to.add, "0", sep="")
            }
            zeros.added <- paste(zeros.to.add, x, sep="")
            return(zeros.added)
        }
    }
}

## 'rename.jpg.nef' renames photo files in working directory with a 'prefix'
## and a number. The series of number is initiated by the value of counter.
## this function requires the function 'add.zeros'.
## If both JPG and NEF files are present, they are given the same numbers.
## User is prompted before files are renamed.
rename.jpg.nef <- function(prefix = character(0), counter = 1,
                           pattern = "DSC_", length.nb = 4) {


    i.each.file <- 1

    ## Get list of files
    list.img <- list.files(pattern = pattern)
    old.names <- new.names <- character(length(list.img))

    ## Get file names without the extension
    uniq.names <- unique(sapply(list.img, function(x) unlist(strsplit(x, "\\."))[1]))

    for(each.file in uniq.names) {

        counter.with.z <- add.zeros(counter, length.nb)

    ## If JPG
        old.jpg <- paste(each.file, "JPG", sep=".")
        if(file.exists(old.jpg)) {
            new.jpg <- paste(prefix, counter.with.z, ".JPG", sep="")
            old.names[i.each.file] <- old.jpg
            new.names[i.each.file] <- new.jpg
            i.each.file <- i.each.file + 1
        }

    ## If NEF
        old.nef <- paste(each.file, "NEF", sep=".")

        if(file.exists(old.nef)) {
            new.nef <- paste(prefix, counter.with.z, ".NEF", sep="")
            old.names[i.each.file] <- old.nef
            new.names[i.each.file] <- new.nef
            i.each.file <- i.each.file + 1
        }

        counter <- counter + 1
    }
    df.rename <- cbind(old.names, new.names)
    if(nrow(df.rename) == 0) stop("Nothing to rename")

    print(df.rename)

    ## Check if files already exist
    sapply(new.names, function(foo)
           if(file.exists(foo))
           stop(foo," already exists, check counter"))

    ## Rename files
    prt <- readline("Proceed (yes/no)? \n")
    if(prt == "yes" || prt == "y")
        apply(df.rename, 1, function(x) file.rename(x[1], x[2]))
    else
        cat("stopped by user \n")
}