library(igraph)
library(DiagrammeR)
library(DiagrammeRsvg)
library(rsvg)

# 1) Read data
edges <- read.csv("edges.csv", stringsAsFactors = FALSE)
nodes <- read.csv("nodes.csv", stringsAsFactors = FALSE)

# 2) Build graph (root -> leaves)
g <- graph_from_data_frame(edges, directed = TRUE, vertices = nodes)

# 3) Put demand on vertices (0 for non-terminals)
V(g)$demand_lps <- ifelse(is.na(V(g)$demand_lps), 0, V(g)$demand_lps)

# 4) Topological order (works for a tree/DAG)
ord <- topo_sort(g, mode = "out")  # root first, leaves last

# 5) Accumulate from leaves back to root
V(g)$acc_lps <- V(g)$demand_lps

for (v in rev(ord)) {
  kids <- neighbors(g, v, mode = "out")   # downstream nodes
  if (length(kids) > 0) {
    V(g)$acc_lps[v] <- V(g)$acc_lps[v] + sum(V(g)$acc_lps[kids])
  }
}

# 6) Edge flow = accumulated flow at the downstream end ("to" node)
E(g)$acc_lps <- V(g)$acc_lps[ head_of(g, E(g)) ]  # head_of = edge "to" in a directed graph

# 7) Write results (optional)
out_edges <- as_data_frame(g, what = "edges")
out_edges$acc_lps <- E(g)$acc_lps
write.csv(out_edges, "edges_with_accumulated_flow.csv", row.names = FALSE)

# 8) Plot to PDF with accumulated flow labels (optional)
pdf("graph_accumulated2.pdf", width = 10, height = 8)
plot(
  g,
  layout = layout_as_tree(g)*10,
  vertex.size = 5,
  vertex.label = V(g)$name,
  edge.arrow.size = 0.6,
  edge.label = paste0(round(E(g)$acc_lps, 1), " l/s"),
  edge.label.cex = 0.8
)
dev.off()

cat("Wrote edges_with_accumulated_flow.csv and graph_accumulated.pdf\n")
# 2) Write DOT file

write_graph(g, file = "network.dot", format = "dot")
#dot_file <- tempfile(fileext = ".dot")
#write_graph(g, file = dot_file, format = "dot")

# 3) Read DOT text and create DiagrammeR graph object

#dot_text <- paste(readLines("network.dot"), collapse = "\n")
#gr <- grViz(dot_text)

# 4) Export to PDF
#svg_txt <- export_svg(gr)
#rsvg_pdf(charToRaw(svg_txt), file = "tree_output.pdf")