package transportcfg

import (
	"fmt"
	"os"
	"os/exec"
	"path/filepath"
	"strconv"
	"strings"
)

func ResolvePrimaryExecStart(client Client, singBoxConfigPath, phoenixDefaultConfigPath string) (string, string, error) {
	if manual := strings.TrimSpace(ConfigString(client.Config, "exec_start")); manual != "" {
		return manual, "manual", nil
	}
	switch strings.ToLower(strings.TrimSpace(client.Kind)) {
	case KindSingBox:
		cmd, err := BuildSingBoxCommand(client, singBoxConfigPath)
		if err != nil {
			return "", "", err
		}
		return cmd, "template:singbox", nil
	case KindDNSTT:
		cmd, err := BuildDNSTTClientCommand(client)
		if err != nil {
			return "", "", err
		}
		return cmd, "template:dnstt", nil
	case KindPhoenix:
		cmd, err := BuildPhoenixClientCommand(client, phoenixDefaultConfigPath)
		if err != nil {
			return "", "", err
		}
		return cmd, "template:phoenix", nil
	default:
		return "", "", fmt.Errorf("no command template for transport kind %q", client.Kind)
	}
}

func BuildSingBoxCommand(client Client, configPath string) (string, error) {
	bin := strings.TrimSpace(ConfigString(client.Config, "singbox_bin"))
	if bin == "" {
		bin = strings.TrimSpace(ConfigString(client.Config, "bin"))
	}
	if bin == "" {
		var err error
		bin, err = ResolveBinary(client.Config, "singbox", "/usr/bin/sing-box", "/usr/local/bin/sing-box", "sing-box")
		if err != nil {
			return "", err
		}
	} else if err := ValidateRequiredBinary(client.Config, "singbox", bin); err != nil {
		return "", err
	}

	args := []string{bin, "run", "-c", strings.TrimSpace(configPath)}
	if extra := strings.TrimSpace(ConfigString(client.Config, "singbox_extra_args")); extra != "" {
		args = append(args, strings.Fields(extra)...)
	}
	return ShellJoinArgs(args, ShellQuoteArg), nil
}

func BuildPhoenixClientCommand(client Client, defaultConfigPath string) (string, error) {
	bin := strings.TrimSpace(ConfigString(client.Config, "phoenix_bin"))
	if bin == "" {
		bin = strings.TrimSpace(ConfigString(client.Config, "bin"))
	}
	if bin == "" {
		var err error
		bin, err = ResolveBinary(client.Config, "phoenix", "/usr/local/bin/phoenix-client", "/usr/bin/phoenix-client", "phoenix-client")
		if err != nil {
			return "", err
		}
	} else if err := ValidateRequiredBinary(client.Config, "phoenix", bin); err != nil {
		return "", err
	}

	configPath := strings.TrimSpace(ConfigString(client.Config, "phoenix_config_path"))
	if configPath == "" {
		configPath = strings.TrimSpace(ConfigString(client.Config, "config_path"))
	}
	if configPath == "" {
		configPath = strings.TrimSpace(defaultConfigPath)
	}

	args := []string{bin, "-config", configPath}
	if extra := strings.TrimSpace(ConfigString(client.Config, "phoenix_extra_args")); extra != "" {
		args = append(args, strings.Fields(extra)...)
	}
	return ShellJoinArgs(args, ShellQuoteArg), nil
}

func BuildDNSTTClientCommand(client Client) (string, error) {
	bin := strings.TrimSpace(ConfigString(client.Config, "dnstt_bin"))
	if bin == "" {
		bin = strings.TrimSpace(ConfigString(client.Config, "bin"))
	}
	if bin == "" {
		var err error
		bin, err = ResolveBinary(client.Config, "dnstt", "/usr/local/bin/dnstt-client", "/usr/bin/dnstt-client", "dnstt-client")
		if err != nil {
			return "", err
		}
	} else if err := ValidateRequiredBinary(client.Config, "dnstt", bin); err != nil {
		return "", err
	}
	if rawArgs := strings.TrimSpace(ConfigString(client.Config, "dnstt_args")); rawArgs != "" {
		args := append([]string{bin}, strings.Fields(rawArgs)...)
		return ShellJoinArgs(args, ShellQuoteArg), nil
	}

	resolverMode := strings.ToLower(strings.TrimSpace(ConfigString(client.Config, "resolver_mode")))
	dohURL := strings.TrimSpace(ConfigString(client.Config, "doh_url"))
	dotAddr := strings.TrimSpace(ConfigString(client.Config, "dot_addr"))
	udpAddr := strings.TrimSpace(ConfigString(client.Config, "udp_addr"))
	if dohURL == "" {
		dohURL = strings.TrimSpace(ConfigString(client.Config, "resolver_url"))
	}
	if dotAddr == "" {
		dotAddr = strings.TrimSpace(ConfigString(client.Config, "resolver_addr"))
	}
	if udpAddr == "" {
		udpAddr = strings.TrimSpace(ConfigString(client.Config, "resolver_addr"))
	}

	if resolverMode == "" {
		switch {
		case dohURL != "":
			resolverMode = "doh"
		case dotAddr != "":
			resolverMode = "dot"
		case udpAddr != "":
			resolverMode = "udp"
		default:
			resolverMode = "doh"
		}
	}
	args := []string{bin}
	switch resolverMode {
	case "doh":
		if dohURL == "" {
			return "", fmt.Errorf("dnstt template requires config.doh_url for resolver_mode=doh")
		}
		args = append(args, "-doh", dohURL)
	case "dot":
		if dotAddr == "" {
			return "", fmt.Errorf("dnstt template requires config.dot_addr or config.resolver_addr for resolver_mode=dot")
		}
		args = append(args, "-dot", dotAddr)
	case "udp":
		if udpAddr == "" {
			return "", fmt.Errorf("dnstt template requires config.udp_addr or config.resolver_addr for resolver_mode=udp")
		}
		args = append(args, "-udp", udpAddr)
	default:
		return "", fmt.Errorf("dnstt template resolver_mode must be doh|dot|udp")
	}

	pubkey := strings.TrimSpace(ConfigString(client.Config, "pubkey"))
	if pubkey == "" {
		pubkey = strings.TrimSpace(ConfigString(client.Config, "pubkey_hex"))
	}
	pubkeyFile := strings.TrimSpace(ConfigString(client.Config, "pubkey_file"))
	if pubkey == "" && pubkeyFile == "" {
		return "", fmt.Errorf("dnstt template requires config.pubkey or config.pubkey_file")
	}
	if pubkeyFile != "" {
		args = append(args, "-pubkey-file", pubkeyFile)
	} else {
		args = append(args, "-pubkey", pubkey)
	}

	utls := strings.TrimSpace(ConfigString(client.Config, "utls"))
	if utls != "" {
		args = append(args, "-utls", utls)
	}

	if extra := strings.TrimSpace(ConfigString(client.Config, "dnstt_extra_args")); extra != "" {
		args = append(args, strings.Fields(extra)...)
	}

	domain := strings.TrimSpace(ConfigString(client.Config, "domain"))
	if domain == "" {
		return "", fmt.Errorf("dnstt template requires config.domain")
	}
	localAddr := strings.TrimSpace(ConfigString(client.Config, "local_addr"))
	if localAddr == "" {
		localAddr = "127.0.0.1:7000"
	}
	args = append(args, domain, localAddr)
	return ShellJoinArgs(args, ShellQuoteArg), nil
}

func DefaultConfigPath(clientID, fileName string, sanitizeID func(string) string) string {
	id := strings.TrimSpace(clientID)
	if sanitizeID != nil {
		id = sanitizeID(id)
	}
	if strings.TrimSpace(id) == "" {
		id = "client"
	}
	return filepath.Join("/etc/selective-vpn/transports", id, fileName)
}

func ResolveBinary(cfg map[string]any, kind string, systemCandidates ...string) (string, error) {
	candidates := make([]string, 0, len(systemCandidates)+2)
	profile := PackagingProfile(cfg)
	switch profile {
	case "bundled":
		root := strings.TrimSpace(ConfigString(cfg, "bin_root"))
		if root == "" {
			root = "/opt/selective-vpn/bin"
		}
		if name := BinaryName(kind); name != "" {
			candidates = append(candidates, filepath.Join(root, name))
		}
		if ConfigBool(cfg, "packaging_system_fallback") || !ConfigHasKey(cfg, "packaging_system_fallback") {
			candidates = append(candidates, systemCandidates...)
		}
	default:
		candidates = append(candidates, systemCandidates...)
	}
	bin, found := FirstExistingBinaryCandidate(candidates...)
	if bin == "" {
		return "", fmt.Errorf("no binary candidates configured for transport kind %q", kind)
	}
	if ConfigBool(cfg, "require_binary") && !found {
		return "", fmt.Errorf("required %s binary not found (profile=%s)", kind, profile)
	}
	return bin, nil
}

func ValidateRequiredBinary(cfg map[string]any, kind, bin string) error {
	if !ConfigBool(cfg, "require_binary") {
		return nil
	}
	if BinaryExists(bin) {
		return nil
	}
	return fmt.Errorf("required %s binary not found: %s", kind, strings.TrimSpace(bin))
}

func PackagingProfile(cfg map[string]any) string {
	profile := strings.ToLower(strings.TrimSpace(ConfigString(cfg, "packaging_profile")))
	switch profile {
	case "", "system":
		return "system"
	case "bundled", "bundle":
		return "bundled"
	default:
		return "system"
	}
}

func BinaryName(kind string) string {
	switch strings.ToLower(strings.TrimSpace(kind)) {
	case "singbox":
		return "sing-box"
	case "dnstt":
		return "dnstt-client"
	case "phoenix":
		return "phoenix-client"
	default:
		return ""
	}
}

func FirstExistingBinaryCandidate(candidates ...string) (string, bool) {
	firstNonEmpty := ""
	for _, candidate := range candidates {
		c := strings.TrimSpace(candidate)
		if c == "" {
			continue
		}
		if firstNonEmpty == "" {
			firstNonEmpty = c
		}
		if resolved, ok := FindBinaryPath(c); ok {
			return resolved, true
		}
	}
	return firstNonEmpty, false
}

func FindBinaryPath(candidate string) (string, bool) {
	c := strings.TrimSpace(candidate)
	if c == "" {
		return "", false
	}
	if strings.ContainsRune(c, '/') {
		if _, err := os.Stat(c); err == nil {
			return c, true
		}
		return "", false
	}
	path, err := exec.LookPath(c)
	if err != nil {
		return "", false
	}
	return path, true
}

func BinaryExists(candidate string) bool {
	_, ok := FindBinaryPath(candidate)
	return ok
}

func ShellJoinArgs(args []string, quoteArg func(string) string) string {
	q := quoteArg
	if q == nil {
		q = ShellQuoteArg
	}
	out := make([]string, 0, len(args))
	for _, arg := range args {
		arg = strings.TrimSpace(arg)
		if arg == "" {
			continue
		}
		out = append(out, q(arg))
	}
	return strings.Join(out, " ")
}

func ShellQuoteArg(in string) string {
	s := strings.ReplaceAll(in, "'", "'\"'\"'")
	return "'" + s + "'"
}

func BuildSSHOverlayCommand(cfg map[string]any, configInt func(map[string]any, string, int) int, quoteArg func(string) string) (string, error) {
	intGetter := configInt
	if intGetter == nil {
		intGetter = ConfigInt
	}
	q := quoteArg
	if q == nil {
		q = ShellQuoteArg
	}

	host := strings.TrimSpace(ConfigString(cfg, "ssh_host"))
	if host == "" {
		return "", fmt.Errorf("config.ssh_host is required for ssh overlay")
	}
	user := strings.TrimSpace(ConfigString(cfg, "ssh_user"))
	if user == "" {
		user = "root"
	}
	socksHost := strings.TrimSpace(ConfigString(cfg, "socks_host"))
	if socksHost == "" {
		socksHost = "127.0.0.1"
	}
	socksPort := intGetter(cfg, "socks_port", 1080)
	if socksPort <= 0 || socksPort > 65535 {
		return "", fmt.Errorf("config.socks_port must be in 1..65535")
	}
	sshPort := intGetter(cfg, "ssh_port", 22)
	if sshPort <= 0 || sshPort > 65535 {
		return "", fmt.Errorf("config.ssh_port must be in 1..65535")
	}
	sshBin := strings.TrimSpace(ConfigString(cfg, "ssh_bin"))
	if sshBin == "" {
		sshBin = "/usr/bin/ssh"
	}
	args := []string{
		sshBin,
		"-N",
		"-o", "ExitOnForwardFailure=yes",
		"-o", "ServerAliveInterval=30",
		"-o", "ServerAliveCountMax=3",
		"-D", fmt.Sprintf("%s:%d", socksHost, socksPort),
		"-p", strconv.Itoa(sshPort),
	}
	sshKey := strings.TrimSpace(ConfigString(cfg, "ssh_key"))
	if sshKey != "" {
		args = append(args, "-i", sshKey)
	}
	extra := strings.TrimSpace(ConfigString(cfg, "ssh_extra_args"))
	if extra != "" {
		args = append(args, strings.Fields(extra)...)
	}
	args = append(args, user+"@"+host)

	quoted := make([]string, 0, len(args))
	for _, arg := range args {
		quoted = append(quoted, q(arg))
	}
	return strings.Join(quoted, " "), nil
}

func ConfigInt(cfg map[string]any, key string, defaultVal int) int {
	if cfg == nil {
		return defaultVal
	}
	raw, ok := cfg[key]
	if !ok || raw == nil {
		return defaultVal
	}
	switch v := raw.(type) {
	case int:
		return v
	case int64:
		return int(v)
	case float64:
		return int(v)
	case string:
		n, err := strconv.Atoi(strings.TrimSpace(v))
		if err == nil {
			return n
		}
	}
	return defaultVal
}