package transportcfg

import (
	"fmt"
	"strings"
)

const (
	KindSingBox = "singbox"
	KindDNSTT   = "dnstt"
	KindPhoenix = "phoenix"

	defaultSingBoxUnitTemplate = "singbox@.service"
)

type Client struct {
	ID     string
	Kind   string
	Config map[string]any
}

func BackendUnit(client Client) string {
	kind := strings.ToLower(strings.TrimSpace(client.Kind))
	unit := strings.TrimSpace(ConfigString(client.Config, "unit"))
	if kind == KindSingBox {
		return resolveSingBoxBackendUnit(client.ID, unit)
	}
	if unit != "" {
		return unit
	}
	return DefaultBackendUnit(kind)
}

func DefaultBackendUnit(kind string) string {
	switch strings.ToLower(strings.TrimSpace(kind)) {
	case KindSingBox:
		return defaultSingBoxUnitTemplate
	case KindDNSTT:
		return "dnstt-client.service"
	case KindPhoenix:
		return "phoenix.service"
	default:
		return ""
	}
}

func resolveSingBoxBackendUnit(clientID, configuredUnit string) string {
	unit := strings.TrimSpace(configuredUnit)
	if unit == "" {
		unit = defaultSingBoxUnitTemplate
	}
	if strings.HasSuffix(unit, "@.service") {
		instance := sanitizeSystemdInstanceID(clientID)
		if instance == "" {
			instance = "client"
		}
		return strings.TrimSuffix(unit, "@.service") + "@" + instance + ".service"
	}
	return unit
}

func sanitizeSystemdInstanceID(in string) string {
	s := strings.ToLower(strings.TrimSpace(in))
	if s == "" {
		return ""
	}
	var b strings.Builder
	b.Grow(len(s))
	lastDash := false
	for i := 0; i < len(s); i++ {
		ch := s[i]
		if (ch >= 'a' && ch <= 'z') || (ch >= '0' && ch <= '9') || ch == '_' || ch == '.' {
			b.WriteByte(ch)
			lastDash = false
			continue
		}
		if ch == '-' {
			if lastDash {
				continue
			}
			b.WriteByte('-')
			lastDash = true
			continue
		}
		if !lastDash {
			b.WriteByte('-')
			lastDash = true
		}
	}
	return strings.Trim(b.String(), "-")
}

func DNSTTSSHTunnelEnabled(client Client) bool {
	if strings.ToLower(strings.TrimSpace(client.Kind)) != KindDNSTT {
		return false
	}
	return ConfigBool(client.Config, "ssh_tunnel") || ConfigBool(client.Config, "ssh_overlay")
}

func DNSTTSSHUnit(client Client) string {
	unit := strings.TrimSpace(ConfigString(client.Config, "ssh_unit"))
	if unit != "" {
		return unit
	}
	return "dnstt-ssh-tunnel.service"
}

func RuntimeMode(cfg map[string]any) string {
	mode := strings.ToLower(strings.TrimSpace(ConfigString(cfg, "runtime_mode")))
	switch mode {
	case "", "exec", "external", "companion":
		return "exec"
	case "embedded":
		return "embedded"
	case "sidecar":
		return "sidecar"
	default:
		return mode
	}
}

func SystemdActionUnits(client Client, action string) ([]string, string, string) {
	unit := BackendUnit(client)
	if unit == "" {
		return nil, "TRANSPORT_BACKEND_UNIT_REQUIRED", "systemd unit is required"
	}
	if !DNSTTSSHTunnelEnabled(client) {
		return []string{unit}, "", ""
	}
	sshUnit := DNSTTSSHUnit(client)
	if strings.TrimSpace(sshUnit) == "" {
		return nil, "TRANSPORT_BACKEND_UNIT_REQUIRED", "dnstt ssh tunnel unit is required"
	}
	switch action {
	case "stop":
		return []string{unit, sshUnit}, "", ""
	default:
		return []string{sshUnit, unit}, "", ""
	}
}

func SystemdHealthUnits(client Client) ([]string, string, string) {
	unit := BackendUnit(client)
	if unit == "" {
		return nil, "TRANSPORT_BACKEND_UNIT_REQUIRED", "systemd unit is required"
	}
	units := []string{unit}
	if DNSTTSSHTunnelEnabled(client) {
		sshUnit := DNSTTSSHUnit(client)
		if strings.TrimSpace(sshUnit) == "" {
			return nil, "TRANSPORT_BACKEND_UNIT_REQUIRED", "dnstt ssh tunnel unit is required"
		}
		units = append(units, sshUnit)
	}
	return units, "", ""
}

func ConfigString(cfg map[string]any, key string) string {
	if cfg == nil {
		return ""
	}
	raw, ok := cfg[key]
	if !ok || raw == nil {
		return ""
	}
	switch v := raw.(type) {
	case string:
		return strings.TrimSpace(v)
	default:
		return strings.TrimSpace(fmt.Sprint(v))
	}
}

func ConfigBool(cfg map[string]any, key string) bool {
	if cfg == nil {
		return false
	}
	raw, ok := cfg[key]
	if !ok || raw == nil {
		return false
	}
	switch v := raw.(type) {
	case bool:
		return v
	case string:
		s := strings.ToLower(strings.TrimSpace(v))
		return s == "1" || s == "true" || s == "yes" || s == "on"
	case float64:
		return v != 0
	case int:
		return v != 0
	default:
		s := strings.ToLower(strings.TrimSpace(fmt.Sprint(v)))
		return s == "1" || s == "true" || s == "yes" || s == "on"
	}
}

func ConfigHasKey(cfg map[string]any, key string) bool {
	if cfg == nil {
		return false
	}
	raw, ok := cfg[key]
	if !ok || raw == nil {
		return false
	}
	if s, ok := raw.(string); ok {
		return strings.TrimSpace(s) != ""
	}
	return true
}