Enhance ParseDuration with configurable parsing options

Introduce ParseDuration() as the primary and simplest entrypoint for
parsing durations. By default it operates in "single-unit mode",
meaning only one unit type is allowed per input string (e.g., "1d" as
opposed to permitting "1d3h5m"). Assumes milliseconds as the default
unit when none is specified.

In addition, a new parser configuration is introduced which provides
flexibility to specify a subset of permissible units. Allows custom
defaults and parsing behaviors tailored for specific use cases.

cmd/haproxy-timeout-checker/haproxy-timeout-checker.go

@@ -3,32 +3,47 @@ package main
 import (
 	"fmt"
 	"os"
-	"time"
 
 	"github.com/frobware/haproxytime"
 )
 
-const HAProxyMaxTimeoutValue = 2147483647 * time.Millisecond
+func printErrorWithPosition(input string, err error, position int) {
+	fmt.Fprintln(os.Stderr, err)
+	fmt.Fprintln(os.Stderr, input)
+	fmt.Fprintf(os.Stderr, "%"+fmt.Sprint(position)+"s", "")
+	fmt.Fprintln(os.Stderr, "^")
+}
 
 func main() {
 	if len(os.Args) < 2 {
-		fmt.Println(`usage: <duration>`)
+		fmt.Println("usage: <duration>")
 		os.Exit(1)
 	}
 
-	duration, position, err := haproxytime.ParseDuration(os.Args[1])
+	parserCfg, err := haproxytime.NewParserConfig(haproxytime.UnitMillisecond, haproxytime.MultiUnitMode)
 	if err != nil {
-		fmt.Fprintln(os.Stderr, os.Args[1])
-		fmt.Fprintf(os.Stderr, "%"+fmt.Sprint(position)+"s", "")
-		fmt.Fprintln(os.Stderr, "^")
-		fmt.Fprintln(os.Stderr, "error:", err)
-		os.Exit(1)
+		fmt.Fprintf(os.Stderr, "error: failed to created parser configuration: %v\n", err)
+		os.Exit(2)
 	}
 
-	if duration.Milliseconds() > HAProxyMaxTimeoutValue.Milliseconds() {
-		fmt.Fprintf(os.Stderr, "duration %vms exceeds HAProxy's maximum value of %vms\n", duration.Milliseconds(), HAProxyMaxTimeoutValue.Milliseconds())
-		os.Exit(1)
+	duration, err := haproxytime.ParseDurationWithConfig(os.Args[1], parserCfg)
+	if err != nil {
+		switch actualErr := err.(type) {
+		case *haproxytime.SyntaxError:
+			printErrorWithPosition(os.Args[1], actualErr, actualErr.Position)
+			os.Exit(3)
+		case *haproxytime.OverflowError:
+			printErrorWithPosition(os.Args[1], actualErr, actualErr.Position)
+			os.Exit(4)
+		}
+	}
+
+	if haproxytime.DurationExceedsMaxTimeout(duration) {
+		fmt.Fprintf(os.Stderr, "%vms exceeds HAProxy's maximum duration (%vms)\n",
+			duration.Milliseconds(),
+			haproxytime.MaxTimeoutInMilliseconds.Milliseconds())
+		os.Exit(5)
 	}
 
-	fmt.Println(duration.Milliseconds())
+	fmt.Printf("%vms\n", duration.Milliseconds())
 }