Enhance ParseDuration with configurable parsing options

Introduce ParseDuration() as the primary and simplest entrypoint for
parsing durations

.gitignore

@@ -19,3 +19,4 @@
 
 # Go workspace file
 go.work
+/haproxytimeout

Makefile

@@ -0,0 +1,17 @@
+DATE		:= $(shell date --iso-8601=seconds)
+GOVERSION	:= $(shell go version)
+COMMIT		:= $(shell git describe --tags --abbrev=8 --dirty --always --long)
+
+PREFIX		:= main
+LDFLAGS		:= -X '$(PREFIX).buildCommit=$(COMMIT)' -X '$(PREFIX).buildDate=$(DATE)' -X '$(PREFIX).buildGoVersion=$(GOVERSION)'
+
+build: test
+	go build -ldflags "$(LDFLAGS)" -o ./haproxytimeout ./cmd/haproxytimeout
+
+test:
+	go test ./...
+
+clean:
+	$(RM) ./haproxytimeout
+
+.PHONY: build test clean

README.md

@@ -1,62 +1,78 @@
-# parse time durations, with support for days
+# Parse time durations, with support for days
 
-This is a Go library that parses duration strings in a format similar
-to time.ParseDuration, with the additional capability of handling
-duration strings specifying a number of days ("d"). This functionality
-is not available in the built-in time.ParseDuration function. It also
-differs by not accepting negative values. This package was primarily
-created for validating HAProxy timeout values.
+A Go library to parse time duration values similar to
+time.ParseDuration, but with extended functionality. In addition to
+the standard duration units like "h", "m", and "s", it also supports
+days (represented as "d"), which are unavailable in the built-in
+time.ParseDuration function. All durations parsed by this package are
+ensured to be non-negative and won't overflow the time.Duration value
+type. Furthermore, the parsed value cannot exceed HAProxy's maximum
+timeout value, ensuring compatibility with HAProxy's configuration
+constraints.
 
-The CLI utility `haproxy-timeout-checker` is an example of using the
-package. It validates the time duration using `ParseDuration` and also
-checks to see if the duration exceeds HAProxy's maximum.
+The CLI utility `haproxytimeout` is an example of using the package.
+The utility parses a duration string, printing the parsed value as a
+pair; "human-readable duration" -> "millisecond duration".
 
 ```console
-$ go run cmd/haproxy-timeout-checker/haproxy-timeout-checker.go "9223372036s"
-duration 9223372036000ms exceeds HAProxy's maximum value of 2147483647ms
+$ go build ./cmd/haproxytimeout
+haproxytimeout - Convert human-readable durations to millisecond format
 
-$ go run cmd/haproxy-timeout-checker/haproxy-timeout-checker.go "2147483647ms"
-2147483647
+Usage:
+  haproxytimeout [-m] [-j] <duration>
 
-$ go run cmd/haproxy-timeout-checker/haproxy-timeout-checker.go "2147483648ms"
-duration 2147483648ms exceeds HAProxy's maximum value of 2147483647ms
+Options:
+  -m: Print the maximum duration HAProxy can tolerate and exit.
+  -j: Print results in JSON format. (e.g., haproxytimeout -j <duration> | jq .milliseconds)
 
-$ go run cmd/haproxy-timeout-checker/haproxy-timeout-checker.go "1d"
-86400000
+Input Assumptions:
+  If the input is a plain number (or a decimal without a unit), it's
+  assumed to be in milliseconds. For example: 'haproxytimeout 1500'
+  is assumed to be '1500ms'.
 
-$ go run cmd/haproxy-timeout-checker/haproxy-timeout-checker.go "1d 1s"
-86401000
+Output Format:
+  The output maps the human-readable format to the milliseconds
+  format. For example: 'haproxytimeout 2h30m' will output '2h30m ->
+  9000000ms'. The right-hand side is always in milliseconds, making it
+  suitable for direct use in a haproxy.cfg file.
 
-$ go run cmd/haproxy-timeout-checker/haproxy-timeout-checker.go "1d 3h 10m 20s 100ms 9999us"
-97820109
+Available units:
+  d   days
+  h:  hours
+  m:  minutes
+  s:  seconds
+  ms: milliseconds
+  us: microseconds
 
-$ go run cmd/haproxy-timeout-checker/haproxy-timeout-checker.go 5000
-5000
+Examples:
+  haproxytimeout 2h30m     -> Convert 2 hours 30 minutes to milliseconds
+  haproxytimeout 1500ms    -> Convert 1500 milliseconds to a human-readable format
+  haproxytimeout -j 1h17m  -> Get JSON output for 1h 17minutes
+  haproxytimeout -m        -> Show the maximum duration HAProxy can tolerate
+```
 
-$ go run cmd/haproxy-timeout-checker/haproxy-timeout-checker.go "5000 999999ms"
-5000 999999ms
-            ^
-error: invalid unit order
+## Examples
 
-$ go run cmd/haproxy-timeout-checker/haproxy-timeout-checker.go "1d 1f"
-1d 1f
-    ^
-error: invalid unit
+```sh
+$ ./haproxytimeout 30m
+30m -> 1800000ms
+```
 
-$ go run cmd/haproxy-timeout-checker/haproxy-timeout-checker.go "1d 1d"
-1d 1d
-    ^
-error: invalid unit order
+```sh
+$ ./haproxytimeout 1d12h
+1d12h -> 129600000ms
+```
 
-$ go run cmd/haproxy-timeout-checker/haproxy-timeout-checker.go "1d 5m 1230ms"
-86701230
+```sh
+# Print maximum value allowed by HAProxy.
+$ ./haproxytimeout -m
+24d20h31m23s647ms -> 2147483647ms
+```
 
-# Note: Spaces are optional.
-$ go run cmd/haproxy-timeout-checker/haproxy-timeout-checker.go "1d5m"
-86700000
+```sh
+% ./haproxytimeout -j 17m
+{"human_readable":"17m","milliseconds":1020000}
 
-$ go run cmd/haproxy-timeout-checker/haproxy-timeout-checker.go "9223372037s"
-9223372037s
-          ^
-error: underflow
+% ./haproxytimeout -j 17m | jq .milliseconds
+1020000
 ```