package ssh

import (
	"fmt"
	"regexp"
	"sort"
	"strings"

	"git.zb-server.de/Sebi/ssh-netbox-wrapper/internal/config"
)

// WrapperFlags are netssh's own long options. OpenSSH has no long options,
// so these never collide with flags meant for ssh.
type WrapperFlags struct {
	DryRun bool
	Jump   string // --jump HOST overrides the configured jump host
	NoJump bool   // --no-jump disables any jump host, including ~/.ssh/config
}

// ExtractWrapperFlags removes netssh's long options that appear before the
// destination. Anything after the destination belongs to the remote command.
func ExtractWrapperFlags(args []string) (WrapperFlags, []string, error) {
	var flags WrapperFlags
	out := make([]string, 0, len(args))
	for i := 0; i < len(args); i++ {
		arg := args[i]
		switch {
		case arg == "--dry-run":
			flags.DryRun = true
		case arg == "--no-jump":
			flags.NoJump = true
		case arg == "--jump":
			if i+1 >= len(args) {
				return flags, nil, fmt.Errorf("--jump requires a host")
			}
			i++
			flags.Jump = args[i]
		case strings.HasPrefix(arg, "--jump="):
			flags.Jump = strings.TrimPrefix(arg, "--jump=")
		case arg == "--" || !strings.HasPrefix(arg, "-") || len(arg) < 2:
			// Destination or end of options: keep the rest unchanged.
			return flags, append(out, args[i:]...), validateJump(flags)
		case strings.HasPrefix(arg, "--"):
			return flags, nil, fmt.Errorf("unknown option %s", arg)
		default:
			out = append(out, arg)
			// Keep the value of an ssh option such as -l USER together with it.
			if takesSeparateValue(arg) && i+1 < len(args) {
				i++
				out = append(out, args[i])
			}
		}
	}
	return flags, out, validateJump(flags)
}

func validateJump(flags WrapperFlags) error {
	if flags.Jump == "" && flags.NoJump {
		return nil
	}
	if flags.Jump != "" && flags.NoJump {
		return fmt.Errorf("--jump and --no-jump are mutually exclusive")
	}
	if strings.HasPrefix(flags.Jump, "-") {
		return fmt.Errorf("--jump: invalid host %q", flags.Jump)
	}
	return nil
}

// takesSeparateValue reports whether a short option cluster ends with a flag
// whose value is the next argument (e.g. "-l" or "-vp").
func takesSeparateValue(arg string) bool {
	for j := 1; j < len(arg); j++ {
		if flagsWithArg[arg[j]] {
			return j == len(arg)-1
		}
	}
	return false
}

// Host is a resolved NetBox host.
type Host struct {
	Name string // NetBox name without the instance prefix
	IP   string
}

// Result is the final ssh argument list and an optional notice for stderr.
type Result struct {
	Args   []string
	Notice string
}

var plainHostname = regexp.MustCompile(`^[A-Za-z0-9]([A-Za-z0-9._-]*[A-Za-z0-9])?$`)

// Apply replaces the destination at destIdx and inserts the configured -o
// options directly before it. Explicit options given by the user come first,
// and ssh uses the first -o value it obtains, so the user's choice wins.
func Apply(args []string, destIdx int, host Host, opts config.SSHOptions, flags WrapperFlags) Result {
	var inserted []string
	add := func(keyword, value string) {
		if !hasOption(args[:destIdx], 0, keyword) {
			inserted = append(inserted, "-o", keyword+"="+value)
		}
	}

	dest := host.IP
	if opts.Target == "name" || opts.Target == "hostname" {
		if plainHostname.MatchString(host.Name) {
			dest = host.Name
			if opts.Target == "name" {
				add("HostName", host.IP)
				add("HostKeyAlias", host.Name)
			}
		}
	}

	userJump := hasOption(args[:destIdx], 'J', "ProxyJump") || hasOption(args[:destIdx], 0, "ProxyCommand")
	switch {
	case userJump:
	case flags.NoJump:
		inserted = append(inserted, "-o", "ProxyJump=none")
	case flags.Jump != "":
		inserted = append(inserted, "-J", flags.Jump)
	case opts.ProxyJump != "" && opts.ProxyJump != "none":
		inserted = append(inserted, "-J", opts.ProxyJump)
	}

	var notice string
	switch opts.HostKeyChecking {
	case "strict":
		add("StrictHostKeyChecking", "yes")
	case "accept-new":
		add("StrictHostKeyChecking", "accept-new")
	case "off":
		if !hasOption(args[:destIdx], 0, "StrictHostKeyChecking") {
			add("StrictHostKeyChecking", "no")
			add("UserKnownHostsFile", "/dev/null")
			add("LogLevel", "ERROR")
			notice = "host key checking is disabled for this connection (ssh.host_key_checking: off)"
		}
	}

	if opts.AddressFamily != "" && !hasBoolFlag(args[:destIdx], '4') && !hasBoolFlag(args[:destIdx], '6') {
		add("AddressFamily", opts.AddressFamily)
	}

	keys := make([]string, 0, len(opts.Options))
	for key := range opts.Options {
		keys = append(keys, key)
	}
	sort.Strings(keys)
	for _, key := range keys {
		add(key, opts.Options[key])
	}

	// Extra arguments go first: short flags such as -4 or -A take the last
	// value given, so the user's own flags later on the line still win.
	replaced := ReplaceHost(args, destIdx, dest)
	out := make([]string, 0, len(opts.ExtraArgs)+len(replaced)+len(inserted))
	out = append(out, opts.ExtraArgs...)
	out = append(out, replaced[:destIdx]...)
	out = append(out, inserted...)
	out = append(out, replaced[destIdx:]...)
	return Result{Args: out, Notice: notice}
}

// hasBoolFlag reports whether a flag without a value, such as -4, was given.
func hasBoolFlag(args []string, wanted byte) bool {
	for i := 0; i < len(args); i++ {
		arg := args[i]
		if arg == "--" || len(arg) < 2 || arg[0] != '-' {
			break
		}
		for j := 1; j < len(arg); j++ {
			if arg[j] == wanted {
				return true
			}
			if flagsWithArg[arg[j]] {
				if j == len(arg)-1 {
					i++
				}
				break
			}
		}
	}
	return false
}

// Quote renders an argument list as a copy-pasteable POSIX shell command.
func Quote(argv []string) string {
	quoted := make([]string, len(argv))
	for i, arg := range argv {
		if arg != "" && strings.Trim(arg, "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789@%+=:,./_-") == "" {
			quoted[i] = arg
			continue
		}
		quoted[i] = "'" + strings.ReplaceAll(arg, "'", `'\''`) + "'"
	}
	return strings.Join(quoted, " ")
}