Ignore nested files when calculating the total

For the nested files:
 - folder/         (5 MB)
 - folder/big_file (15 MB)

The --total now outputs 15 MB instead of the previous 20 MB, because the
inner file is inside of the folder that was also passed as an argument.

Implemented with the Trie data structure, made of HashMap and PathBufs
that represent each path components of the canonicalized file paths.

Fixes cauebs#12.

src/lib.rs

@@ -3,6 +3,7 @@ use number_prefix::NumberPrefix;
 use walkdir::WalkDir;
 
 use std::{
+    collections::BTreeMap,
     fmt::Display,
     path::{Path, PathBuf},
 };
@@ -31,6 +32,7 @@ impl<T, E: Display> ResultExt<T, E> for Result<T, E> {
     }
 }
 
+#[derive(PartialEq, Eq, PartialOrd, Ord)]
 pub struct Entry {
     pub path: PathBuf,
     pub size: u64,
@@ -91,3 +93,105 @@ pub fn format_size(size: u64, binary: bool) -> String {
         NumberPrefix::Prefixed(prefix, number) => format!("{:.2} {}B", number, prefix),
     }
 }
+
+/// Calculate the sum of sizes of all entries
+///
+/// Ignore nested files when calculating the total
+///
+/// For the nested files:
+///  - `folder/         (5 MB)`
+///  - `folder/big_file (15 MB)`
+///
+/// The is 15 MB instead of 20 MB because the inner file is inside of the
+/// folder that was also received as an argument
+///
+/// Implemented with the Trie data structure, made of HashMap and PathBufs
+/// that represent each path components of the canonicalized file paths
+pub fn calculate_unique_total_size(entries: &[Entry]) -> u64 {
+    // Sorted to guarantee that files can only come after their parent directories
+    let sorted_entries = {
+        let mut entries_and_paths: Vec<(PathBuf, &Entry)> = vec![];
+
+        // Canonicalize each path, reporting and skipping errors
+        for entry in entries {
+            let canonical_path = entry.path.canonicalize().log_err(Some(&entry.path));
+            if let Ok(path) = canonical_path {
+                entries_and_paths.push((path, entry));
+            }
+        }
+        entries_and_paths.sort_unstable();
+        entries_and_paths
+    };
+
+    #[derive(PartialEq, Eq, PartialOrd, Ord)]
+    struct TriePathNode {
+        // Children nodes of this current path, accessed by path
+        children: BTreeMap<PathBuf, TriePathNode>,
+        // Size of the file that ends at this node
+        node_size: u64,
+    }
+
+    let mut trie_root = TriePathNode {
+        children: BTreeMap::new(),
+        node_size: 0,
+    };
+
+    // For each entry/path, add it to the Trie if it wasn't already inserted
+    //
+    // If the Trie receives a folder that is parent of a previously added file, then just consider
+    // the parent folder, removing the childs, this way, we do not count them twice towards the
+    // final total
+    for (path, entry) in sorted_entries {
+        // Necessary because we need to check when it's the last path piece
+        let mut path_iter = path.iter().peekable();
+        // Pointer to traverse the tree
+        let mut current_trie_node = &mut trie_root;
+        // Size to be added at the endif the current entry isn't children of any other
+        let size_of_current_file = entry.size;
+
+        while let Some(piece) = path_iter.next() {
+            // Query for the node in the Trie which matches the current path piece
+            let entry = current_trie_node.children.entry(PathBuf::from(piece));
+
+            // Keeps track if the current entry is child of another previously found
+            let mut already_considered = false;
+            let next_trie_node = entry
+                .and_modify(|_| {
+                    // If we are in this block, it means that the node size was already considered
+                    // because a parent of it was inserted. So we will skip this file
+                    already_considered = true;
+                })
+                // Add a node with 0 size, which may be changed after if it is the last piece
+                .or_insert(TriePathNode {
+                    children: BTreeMap::new(),
+                    node_size: 0,
+                });
+
+            // Skipping already accounted file, because it is nested inside of another one
+            if already_considered {
+                break;
+            }
+
+            // If we are at the last piece of the current entry path, it means that this is the tip
+            // that finally represents the file, and which path is the full file path
+            let is_the_last_piece = path_iter.peek().is_none();
+            if is_the_last_piece {
+                // Update the size of this piece
+                next_trie_node.node_size = size_of_current_file;
+                // Drop all the childrens so that their sizes won't be added
+                next_trie_node.children.clear();
+            }
+
+            // Update the pointer to keep traversing the trie
+            current_trie_node = next_trie_node;
+        }
+    }
+
+    fn trie_recursive_sum(node: &TriePathNode) -> u64 {
+        let children_sum: u64 = node.children.values().map(trie_recursive_sum).sum();
+        node.node_size + children_sum
+    }
+
+    // Traverse the trie tree to calculate the sum
+    trie_recursive_sum(&trie_root)
+}

src/main.rs

@@ -4,7 +4,7 @@ use wild;
 
 mod cli;
 use cli::Cli;
-use durt::{format_size, Entry};
+use durt::{calculate_unique_total_size, format_size, Entry};
 
 fn main() {
     #[cfg(windows)]
@@ -60,7 +60,7 @@ fn main() {
         Table::new("  {:>}  {:<}")
     };
 
-    let total_size = entries.iter().map(|e| e.size).sum();
+    let total_size = calculate_unique_total_size(&entries);
     let mut omitted_entries = 0;
 
     for entry in entries {