From abce6f2ae0f5fa36ea2069e69a4a070156644ea1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Gustav=20S=C3=B6rn=C3=A4s?= <gustav@sornas.net>
Date: Sat, 31 Jul 2021 22:49:00 +0200
Subject: recursive inner_sort_by

---
 cli/src/main.rs | 37 ++++++++++++++++++-------------------
 1 file changed, 18 insertions(+), 19 deletions(-)

diff --git a/cli/src/main.rs b/cli/src/main.rs
index 12325e2..e405e48 100644
--- a/cli/src/main.rs
+++ b/cli/src/main.rs
@@ -1,5 +1,6 @@
 use chrono::naive::NaiveDate;
 use rust_decimal::Decimal;
+use std::cmp::Ordering;
 use std::path::PathBuf;
 use std::str::FromStr;
 use structopt::clap::AppSettings;
@@ -141,46 +142,44 @@ fn main() {
             if sort.is_empty() {
                 transactions.sort_by_key(|t| t.date);
             } else {
-                match &sort[0] {
-                    SortTarget::Amount => transactions.sort_by_key(|t| t.amount),
-                    SortTarget::Date => transactions.sort_by_key(|t| t.date),
-                }
-                for i in 1..sort.len() {
-                    //TODO This won't work with 3+ sorts in case key 2 are equal across a key 1
-                    //     border. We need to pass the earlier buckets for later sorts as well.
-                    //     `Vec<range>`?
-                    inner_sort_by(&mut transactions, sort_by_func(&sort[i-1]), sort_by_func(&sort[i]));
-                }
+                let mut sorts: Vec<_> = sort.iter().map(sort_by_func).collect();
+                inner_sort_by(&mut transactions, &mut sorts);
             }
             println!("{}", Table::new(transactions).with(Style::psql()));
         }
     }
 }
 
-fn sort_by_func(sort: &SortTarget) -> impl FnMut(&&Transaction, &&Transaction) -> std::cmp::Ordering {
+fn sort_by_func(sort: &SortTarget) -> impl FnMut(&&Transaction, &&Transaction) -> Ordering {
     match sort {
         SortTarget::Amount => |t1: &&Transaction, t2: &&Transaction| t1.amount.cmp(&t2.amount),
         SortTarget::Date => |t1: &&Transaction, t2: &&Transaction| t1.date.cmp(&t2.date),
     }
 }
 
-fn inner_sort_by<T, F>(v: &mut [T], mut outer_cmp: F, mut inner_cmp: F)
+fn inner_sort_by<T, F>(v: &mut [T], cmps: &mut [F])
 where
-    F: FnMut(&T, &T) -> std::cmp::Ordering,
+    F: FnMut(&T, &T) -> Ordering,
 {
     // Early out
-    if v.len() < 2 {
+    if v.len() < 2 || cmps.is_empty() {
         return;
     }
 
+    v.sort_by(&mut cmps[0]);
+
+    let mut ranges = Vec::new();
     let mut lower = 0; // Lower bound of current equal range
     for i in 0..v.len() {
-        if outer_cmp(&v[i], &v[lower]) != std::cmp::Ordering::Equal {
-            let upper = i;
-            if upper - lower > 1 {
-                v[lower..upper].sort_by(&mut inner_cmp);
-            }
+        if cmps[0](&v[i], &v[lower]) != Ordering::Equal {
+            ranges.push(lower..i);
             lower = i;
         }
     }
+
+    if cmps.len() != 1 {
+        for range in ranges {
+            inner_sort_by(&mut v[range], &mut cmps[1..]);
+        }
+    }
 }
-- 
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