package main

import (
	"flag"
	"fmt"
	"io"
	"os"

	"github.com/wzray/dns/internal/client"
)

const defaultServer = "http://localhost:8080"

func main() {
	os.Exit(run(os.Args[1:], os.Stdout, os.Stderr))
}

func run(args []string, stdout, stderr io.Writer) int {
	fs := flag.NewFlagSet("dns-cli", flag.ContinueOnError)
	fs.SetOutput(stderr)
	server := fs.String("server", envOr("DNS_SERVER_URL", defaultServer),
		"Base URL of the dns-server (env: DNS_SERVER_URL)")
	fs.Usage = func() { printRootUsage(stderr, fs) }

	if err := fs.Parse(args); err != nil {
		return 2
	}
	rest := fs.Args()
	if len(rest) == 0 {
		printRootUsage(stderr, fs)
		return 2
	}

	cmd, cmdArgs := rest[0], rest[1:]
	c := client.New(*server)

	switch cmd {
	case "help", "-h", "--help":
		printRootUsage(stdout, fs)
		return 0
	case "list", "ls":
		return runList(c, cmdArgs, stdout, stderr)
	case "add":
		return runAdd(c, cmdArgs, stdout, stderr)
	case "remove", "rm", "delete":
		return runRemove(c, cmdArgs, stdout, stderr)
	default:
		fmt.Fprintf(stderr, "unknown command: %q\n\n", cmd)
		printRootUsage(stderr, fs)
		return 2
	}
}

func runList(c *client.Client, args []string, stdout, stderr io.Writer) int {
	fs := flag.NewFlagSet("list", flag.ContinueOnError)
	fs.SetOutput(stderr)
	fs.Usage = func() {
		fmt.Fprintln(stderr, "Usage: dns-cli list")
		fmt.Fprintln(stderr, "\nList configured DNS nameservers.")
	}
	if err := fs.Parse(args); err != nil {
		return 2
	}
	if fs.NArg() != 0 {
		fmt.Fprintln(stderr, "list: unexpected arguments")
		fs.Usage()
		return 2
	}
	servers, err := c.List()
	if err != nil {
		fmt.Fprintf(stderr, "error: %v\n", err)
		return 1
	}
	if len(servers) == 0 {
		fmt.Fprintln(stdout, "(no nameservers configured)")
		return 0
	}
	for _, s := range servers {
		fmt.Fprintln(stdout, s)
	}
	return 0
}

func runAdd(c *client.Client, args []string, stdout, stderr io.Writer) int {
	fs := flag.NewFlagSet("add", flag.ContinueOnError)
	fs.SetOutput(stderr)
	fs.Usage = func() {
		fmt.Fprintln(stderr, "Usage: dns-cli add <address>")
		fmt.Fprintln(stderr, "\nAdd a DNS nameserver (IPv4 or IPv6).")
	}
	if err := fs.Parse(args); err != nil {
		return 2
	}
	if fs.NArg() != 1 {
		fmt.Fprintln(stderr, "add: exactly one <address> argument is required")
		fs.Usage()
		return 2
	}
	addr := fs.Arg(0)
	if err := c.Add(addr); err != nil {
		fmt.Fprintf(stderr, "error: %v\n", err)
		return 1
	}
	fmt.Fprintf(stdout, "added: %s\n", addr)
	return 0
}

func runRemove(c *client.Client, args []string, stdout, stderr io.Writer) int {
	fs := flag.NewFlagSet("remove", flag.ContinueOnError)
	fs.SetOutput(stderr)
	fs.Usage = func() {
		fmt.Fprintln(stderr, "Usage: dns-cli remove <address>")
		fmt.Fprintln(stderr, "\nRemove a DNS nameserver. Aliases: rm, delete.")
	}
	if err := fs.Parse(args); err != nil {
		return 2
	}
	if fs.NArg() != 1 {
		fmt.Fprintln(stderr, "remove: exactly one <address> argument is required")
		fs.Usage()
		return 2
	}
	addr := fs.Arg(0)
	if err := c.Remove(addr); err != nil {
		fmt.Fprintf(stderr, "error: %v\n", err)
		return 1
	}
	fmt.Fprintf(stdout, "removed: %s\n", addr)
	return 0
}

func printRootUsage(w io.Writer, fs *flag.FlagSet) {
	fmt.Fprintln(w, "dns-cli — manage DNS nameservers on a remote host via the dns-server REST API.")
	fmt.Fprintln(w)
	fmt.Fprintln(w, "Usage:")
	fmt.Fprintln(w, "  dns-cli [global flags] <command> [args]")
	fmt.Fprintln(w)
	fmt.Fprintln(w, "Commands:")
	fmt.Fprintln(w, "  list            List configured DNS nameservers")
	fmt.Fprintln(w, "  add <address>   Add a DNS nameserver")
	fmt.Fprintln(w, "  remove <addr>   Remove a DNS nameserver (aliases: rm, delete)")
	fmt.Fprintln(w, "  help            Show this help")
	fmt.Fprintln(w)
	fmt.Fprintln(w, "Global flags:")
	fs.PrintDefaults()
	fmt.Fprintln(w)
	fmt.Fprintln(w, "Run 'dns-cli <command> --help' for command-specific help.")
}

func envOr(key, def string) string {
	if v := os.Getenv(key); v != "" {
		return v
	}
	return def
}