From 1ed5e7e478f7c9fb1a3f69f22624122ae5ef26da Mon Sep 17 00:00:00 2001
From: Mahmoud Al-Qudsi <mqudsi@neosmart.net>
Date: Wed, 18 Dec 2019 19:21:23 -0600
Subject: [PATCH] Dynamically choose units for `time` output

---
 src/builtin_time.cpp | 58 ++++++++++++++++++++++++++++++++++++++------
 1 file changed, 51 insertions(+), 7 deletions(-)

diff --git a/src/builtin_time.cpp b/src/builtin_time.cpp
index 3a5267a77..790c558d3 100644
--- a/src/builtin_time.cpp
+++ b/src/builtin_time.cpp
@@ -100,17 +100,61 @@ int builtin_time(parser_t &parser, io_streams_t &streams, wchar_t **argv) {
 
         uint64_t net_sys_micros = fish_sys_micros + child_sys_micros;
         uint64_t net_usr_micros = fish_usr_micros + child_usr_micros;
-        uint64_t wall_micros = micros(wall[1]) - micros(wall[0]);
+        uint64_t net_wall_micros = micros(wall[1]) - micros(wall[0]);
+
+        enum class unit {
+            minutes,
+            seconds,
+            milliseconds,
+            microseconds,
+        };
+
+        auto get_unit = [](uint64_t micros) {
+            if (micros > 900 * 1E6) {
+                return unit::minutes;
+            }
+            else if (micros > 1 * 1E6) {
+                return unit::seconds;
+            } else if (micros > 10E3) {
+                return unit::milliseconds;
+            } else {
+                return unit::microseconds;
+            }
+        };
+
+        auto unit_name = [](unit unit) {
+            switch (unit) {
+                case unit::minutes: return "minutes";
+                case unit::seconds: return "seconds";
+                case unit::milliseconds: return "milliseconds";
+                case unit::microseconds: return "microseconds";
+            }
+        };
+
+        auto convert = [](uint64_t micros, unit unit) {
+            switch (unit) {
+                case unit::minutes: return micros / 1.0E6 / 60.0;
+                case unit::seconds: return micros / 1.0E6;
+                case unit::milliseconds: return micros / 1.0E3;
+                case unit::microseconds: return micros / 1.0;
+            }
+        };
+
+        auto wall_unit = get_unit(net_wall_micros);
+        auto cpu_unit = get_unit((net_sys_micros + net_usr_micros) / 2);
+        auto wall_time = convert(net_wall_micros, wall_unit);
+        auto usr_time = convert(net_usr_micros, cpu_unit);
+        auto sys_time = convert(net_sys_micros, cpu_unit);
 
         streams.out.append_format(
             L"\n__________________________________"              \
-            L"\nExecution completed in %f seconds"               \
-            L"\nuser time     %f seconds"                        \
-            L"\nsystem time   %f seconds"                        \
+            L"\nExecuted in    %6.2F %s"               \
+            L"\n   usr time    %6.2F %s"                        \
+            L"\n   sys time    %6.2F %s"                        \
             L"\n\n",
-            wall_micros / 1.0E6,
-            net_usr_micros / 1.0E6,
-            net_sys_micros / 1.0E6
+            wall_time, unit_name(wall_unit),
+            usr_time, unit_name(cpu_unit),
+            sys_time, unit_name(cpu_unit)
         );
 
     }