# R/tree_helpers.R

# Buchungsanzahl rekursiv für einen Knoten und alle Nachkommen
count_recursive <- function(num, df, counts) {
  # Alle Nachkommen: alles im Bereich (num, num+1000) je nach Ebene
  divisor <- ifelse(num %% 1000 == 0, 1000,
    ifelse(num %% 100  == 0, 100,
      ifelse(num %% 10   == 0, 10, 1)))
  
  descendants <- df$id[
    df$num >= num & 
      df$num <  num + divisor
  ]
  
  sum(counts$n[counts$account_id %in% descendants], na.rm = TRUE)
}

# Label mit Buchungsanzahl
make_label <- function(num, df, counts) {
  name  <- df$account_name[df$num == num]
  total <- count_recursive(num, df, counts)
  ifelse(total > 0,
    paste0(name, " (", total, ")"),
    name
  )
}

# Baum rekursiv aufbauen
build_level <- function(df, counts, parent_num, divisor) {
  if (divisor < 1) return(list())
  
  children <- df[
    df$num >  parent_num &
      df$num <  parent_num + divisor * 10 &
      df$num %% divisor == 0 &
      df$num %% (divisor * 10) != 0,
  ]
  
  if (nrow(children) == 0) return(list())
  
  result <- lapply(seq_len(nrow(children)), function(i) {
    child_num <- children$num[i]
    subtree   <- build_level(df, counts, child_num, divisor / 10)
    if (length(subtree) == 0)
      structure(list(), sttype = "default")
    else
      subtree
  })
  
  setNames(result, sapply(children$num, make_label, df = df, counts = counts))
}

# Hauptfunktion: kompletten Baum aus accounts-Tabelle bauen
build_account_tree <- function(conn) {
  df     <- dbReadTable(conn, "accounts")
  df$num <- as.integer(substr(df$account_name, 1, 4))
  
  counts <- tbl(conn, "postings") %>%
    count(account_id) %>%
    collect()
  
  tops <- df[df$num %% 1000 == 0, ]
  
  tree <- lapply(seq_len(nrow(tops)), function(i) {
    build_level(df, counts, tops$num[i], 100)
  })
  
  setNames(
    tree, 
    sapply(tops$num, make_label, df = df, counts = counts)
  )
}