find_last_existing_file_index <- function(ffns, start_index) {
  i <- start_index
  while (i > 0) {
    if (file.exists(ffns[i])) {
      return(i)
    }
    i <- i - 1
  }
  
  # If no files exist in the previous indices, check from the end
  i <- length(ffns)
  
  while (i > start_index) {
    if (file.exists(ffns[i])) {
      return(i)
    }
    i <- i - 1
  }
  
  return(0)  # If no files exist at all
}

#' Read CMFD file RDS, and write to .csv TSD.
#'
CMFD.rds2csv <- function(CV, fns){
  # fns = subdf[, 'FILENAME']
  msg = paste0('CMFD.rds2csv', ':: ')
  yrs = max(CV$json$start_year, 1979) : min(CV$json$end_year, 2018)
  ny=length(yrs)
  nf = length(fns)
  for(i in 1:nf){
    fn = fns[i]
    message(msg, i, '/', nf, '\t', fn)
    fn.out = file.path(CV$dirs$tsd, paste0(CV$json$meteorological_data, '_', fn, '.csv') )
    if(file.exists(fn.out)){
      # next
    }
    ffns = file.path(CV$files$ldas.dir, yrs, paste0(fn, '.RDS') )
    fe = file.exists(ffns)
    idx = which(!fe)
    if(length(idx) > 1){
      message(msg, 'Files missing: ')
      print(ffns)
      next;
    }else{
      # message(msg, 'All .RDS file exist.')
    }

    for(j in 1:ny){
      jj = find_last_existing_file_index(ffns, j)
      if(jj<=0){
        message(msg, 'All file is missing.')
        cat(ffns)
        stop('File ERROR')
      }
      if(jj!=j){
        message(msg, 'File ', ffns[j], ' DOES NOT exist.')
        message(msg, 'Replaced with ', basename(ffns[jj]))
      }
      x = readRDS(ffns[jj])
      if(j ==1){
        tsd=x;
      }else{
        tsd = rbind(tsd, x)
      }
    }
    tsd$RH_1[tsd$RH_1>1]=1
    write.tsd(x= round(tsd, 4), file = fn.out)
    if(i==1){
      png(filename = file.path(CV$dirs$fig, paste0('ETV_', 'LDAS_TSD', '.png')), type='cairo', height = 7, width = 7, units = 'in', res = 300)
      par(mar=c(2, 2, 1, 1) )
      plot.zoo(x = tsd, main=paste(fn))
      dev.off()
    }
  }
}

# iflag=try(ExtractETV(CV),TRUE)
NLDAS.rds2csv <- function(CV, fns){
  # fns = subdf[, 'FILENAME']
  msg = paste0('NLDAS.rds2csv', ':: ')
  yrs = CV$json$start_year : CV$json$end_year
  ny=length(yrs)
  nf = length(fns)
  i=1
  for(i in 1:nf){
    fn = fns[i]
    message(msg, i, '/', nf, '\t', fn)
    fn.out = file.path(CV$dirs$tsd, paste0(CV$json$meteorological_data, '_', fn, '.csv') )
    if(file.exists(fn.out)){
      next
    }
    ffns = file.path(CV$files$ldas.dir, yrs, paste0(fn, '.RDS') )
    fe = file.exists(ffns)
    idx = which(!fe)
    if(length(idx) > 1){
      message(msg, 'Files missing: ')
      print(ffns)
      next;
    }else{
      # message(msg, 'All .RDS file exist.')
    }
    ny
    for(j in 1:ny){
      if(file.exists(ffns[j])){
      x=readRDS(ffns[j])
      }else{
        message('File is missing: ', ffns[j])
        stop()
      }
      if(j ==1){
        tsd=x;
      }else{
        tsd = rbind(tsd, x)
      }
    }
    tsd$RH_1[tsd$RH_1>1]=1
    write.tsd(x= round(tsd, 4), file = fn.out)
    if(i==1){
      png(type='cairo',filename = file.path(CV$dirs$fig, paste0('ETV_', 'LDAS_TSD', '.png')), height = 7, width = 7, units = 'in', res = 300)
      par(mar=c(2, 2, 1, 1) )
      plot.zoo(x = tsd, main=paste(fn, ' - ', min(yrs)))
      dev.off()
    }
  }
}

GLDAS.rds2csv <- function(CV, fns){
  # fns = subdf[, 'FILENAME']
  msg = paste0('GLDAS.rds2csv', ':: ')
  yrs = CV$json$start_year : CV$json$end_year
  ny=length(yrs)
  nf = length(fns)
  i=1
  for(i in 1:nf){
    fn = fns[i]
    message(msg, i, '/', nf, '\t', fn)
    fn.out = file.path(CV$dirs$tsd, paste0(CV$json$meteorological_data, '_', fn, '.csv') )
    if(file.exists(fn.out)){
      next
    }
    ffns = file.path(CV$files$ldas.dir, yrs, paste0(fn, '.RDS') )
    fe = file.exists(ffns)
    idx = which(!fe)
    if(length(idx) > 1){
      message(msg, 'Files missing: ')
      print(ffns)
      next;
    }else{
      # message(msg, 'All .RDS file exist.')
    }
    for(j in 1:ny){
      # message('\t', j, '/', ny)
      jj = find_last_existing_file_index(ffns, j)
      message(jj)
      if(jj<=0){
        message(msg, 'All file is missing.')
        cat(ffns)
        stop('File ERROR')
      }
      if(jj!=j){
        message(msg, 'File ', ffns[j], ' DOES NOT exist.')
        message(msg, 'Replaced with ', basename(ffns[jj]))
      }
      x = readRDS(ffns[jj])
      if(j ==1){
        tsd=x;
      }else{
        tsd = rbind(tsd, x)
      }
    }
    tsd$RH_1[tsd$RH_1>1]=1
    write.tsd(x= round(tsd, 4), file = fn.out)
    if(i==1){
      png(type='cairo',filename = file.path(CV$dirs$fig, paste0('ETV_', 'LDAS_TSD', '.png')), height = 7, width = 7, units = 'in', res = 300)
      par(mar=c(2, 2, 1, 1) )
      plot.zoo(x = tsd, main=paste(fn))
      dev.off()
    }
  }
}

ERA5L.rds2csv <- function(CV, fns){}

FLDAS.rds2csv <- function(CV, fns){}
CLDAS.rds2csv <- function(CV, fns){}