cli: turn action and target into positional arguments

3 files changed, 40 insertions, 19 deletions

diff --git a/changelog.md b/changelog.md
index b8af052..02a405f 100644
--- a/changelog.md
+++ b/changelog.md
@@ -2,6 +2,7 @@ Changelog
 =========
 
 ## Next release
+* The monitor and target are now positional CLI arguments instead of options
 * Fixed issue emitting pings when the system's IP address changed during exec
 * Added `--timestamp=datetime|unix|none` param to set line header format
 
diff --git a/main.nim b/main.nim
index 115808d..07686ed 100644
--- a/main.nim
+++ b/main.nim
@@ -9,6 +9,7 @@ import std/net
 import std/posix
 import std/paths
 import std/strutils
+import std/sequtils
 import std/parseopt
 
 import file
@@ -33,17 +34,24 @@ proc registerTerminationHandlers() =
   for signal in [SIGTERM, SIGHUP, SIGQUIT, SIGINT]:
     discard sigaction(signal, action)
 
+func getArg(
+  args: seq[tuple[kind: CmdLineKind, key, val: string]],
+  index: int,
+  label: string
+): string =
+  try: args[index].key
+  except: raise newException(ValueError, "Missing " & label & " argument")
+
 proc main() =
   var
     scale: Scale = log2
     symbols = UNICODE_SYMBOLS
     timestampHeader = formatTimestampDateTime
     (min, max) = (0, 1000)
-    probe: (timeout: Duration) -> int
 
   for optKind, key, val in getopt():
     if optKind notin {cmdLongOption, cmdShortOption}:
-      raise newException(ValueError, "Invalid argument: " & key)
+      continue
 
     case key:
 
@@ -81,21 +89,33 @@ proc main() =
       if parts.len != 2: raise newException(ValueError, "Invalid range")
       (min, max) = (parseInt(parts[0]), parseInt(parts[1]))
 
+    else:
+      raise newException(ValueError, "Unrecognised option")
+
+  let
+    args = getopt().toSeq.filterIt(it.kind == cmdArgument)
+    monitor = args.getArg(0, "monitor")
+    target = args.getArg(1, "target")
+
+  if args.len > 2:
+    raise newException(ValueError, "Invalid number of arguments")
+
+  let probe = case monitor:
     of "ping":
-      let targetIp = resolve(val)
+      let targetIp = resolve(target)
       let mon = initPingMonitor(targetIp, procIdent())
-      probe = (timeout: Duration) => mon.ping(timeout).inMilliseconds.int
+      (timeout: Duration) => mon.ping(timeout).inMilliseconds.int
 
     of "value":
-      let mon = initFileValueMonitor(Path val)
-      probe = (timeout: Duration) => mon.readValue()
+      let mon = initFileValueMonitor(Path target)
+      (timeout: Duration) => mon.readValue()
 
     of "change":
-      let mon = initFileChangeMonitor(Path val)
-      probe = (timeout: Duration) => mon.readValue()
+      let mon = initFileChangeMonitor(Path target)
+      (timeout: Duration) => mon.readValue()
 
-  if probe == nil:
-    raise newException(ValueError, "Missing monitor argument")
+    else:
+      raise newException(ValueError, "Unrecognised monitor argument")
 
   loop(
     probe,
diff --git a/readme.md b/readme.md
index a105b43..52c8a9e 100644
--- a/readme.md
+++ b/readme.md
@@ -22,13 +22,13 @@ CLI usage
 ```helptext
 tickwatch: A monitoring and visualization tool
 
-Usage: tickwatch [OPTIONS]
+Usage: tickwatch [OPTIONS] MONITOR TARGET
 
-Monitor options:
-  --ping=HOST         Monitor ping latency to specified IP or hostname
-                      Prefix hostname with 4/ or 6/ to force IP version
-  --value=PATH        Monitor a sysfs file's value
-  --change=PATH       Monitor changes in a sysfs file's value
+Monitors:
+  ping                Monitor ping latency to specified IP or hostname
+                      Prefix target hostname with 4/ or 6/ to force IP version
+  value               Monitor a sysfs file's value
+  change              Monitor changes in a sysfs file's value
 
 Display options:
   --range=MIN:MAX     Set range of values (default: 0:1000)
@@ -44,13 +44,13 @@ Other options:
   --version, -v       Display the version
 
 Examples:
-  tickwatch --ping=6/euxane.net
+  tickwatch ping 6/euxane.net
 
   tickwatch --range=0:100000 \
-    --change=/sys/class/net/eth0/statistics/rx_packets
+    change /sys/class/net/eth0/statistics/rx_packets
 
   tickwatch --scale=linear --range=0:50000 \
-    --value=/sys/class/thermal/thermal_zone0/temp
+    value /sys/class/thermal/thermal_zone0/temp
 ```