package main

import (
	"fmt"
	"os"
	"strings"
	"testing"
)

type Args struct {
	Options    map[string]string
	Flags      map[string]bool
	Positionals []string
}

// ParseArgs parses a compact CLI syntax:
// --key=value, --key value, --flag, -abc, and positional arguments.
// Parsing stops after "--"; remaining tokens are positionals.
func ParseArgs(argv []string) Args {
	out := Args{
		Options: make(map[string]string),
		Flags:   make(map[string]bool),
	}

	for i := 0; i < len(argv); i++ {
		arg := argv[i]

		if arg == "--" {
			out.Positionals = append(out.Positionals, argv[i+1:]...)
			break
		}

		if strings.HasPrefix(arg, "--") && len(arg) > 2 {
			name := arg[2:]

			if key, val, ok := strings.Cut(name, "="); ok {
				out.Options[key] = val
				continue
			}

			if i+1 < len(argv) && !strings.HasPrefix(argv[i+1], "-") {
				out.Options[name] = argv[i+1]
				i++
			} else {
				out.Flags[name] = true
			}
			continue
		}

		if strings.HasPrefix(arg, "-") && len(arg) > 1 {
			for _, ch := range arg[1:] {
				out.Flags[string(ch)] = true
			}
			continue
		}

		out.Positionals = append(out.Positionals, arg)
	}

	return out
}

func main() {
	args := ParseArgs(os.Args[1:])

	fmt.Println("options:", args.Options)
	fmt.Println("flags:", args.Flags)
	fmt.Println("positionals:", args.Positionals)
}

func TestParseArgs(t *testing.T) {
	args := ParseArgs([]string{
		"--name=demo",
		"--count", "3",
		"-vf",
		"input.txt",
	})

	if args.Options["name"] != "demo" {
		t.Fatalf("name = %q", args.Options["name"])
	}
	if args.Options["count"] != "3" {
		t.Fatalf("count = %q", args.Options["count"])
	}
	if !args.Flags["v"] || !args.Flags["f"] {
		t.Fatalf("flags = %#v", args.Flags)
	}
	if len(args.Positionals) != 1 || args.Positionals[0] != "input.txt" {
		t.Fatalf("positionals = %#v", args.Positionals)
	}
}

func TestParseArgsStopsAfterDoubleDash(t *testing.T) {
	args := ParseArgs([]string{"--verbose", "--", "--not-a-flag", "-x"})

	if !args.Flags["verbose"] {
		t.Fatalf("flags = %#v", args.Flags)
	}
	if len(args.Positionals) != 2 {
		t.Fatalf("positionals = %#v", args.Positionals)
	}
}