package config

import (
	"crypto/sha256"
	"encoding/hex"
	"encoding/json"
	"fmt"
	"os"
	"path/filepath"
	"strings"
)

const (
	PackageComponentRun = "run"

	PackageConfigEnv = "RUN_PACKAGE_CONFIG"
)

type PackageConfig struct {
	Kind             string `json:"kind"`
	ServerInstanceID string `json:"serverInstanceId"`
	PluginID         string `json:"pluginId"`
	RunEndpointID    string `json:"runEndpointId,omitempty"`
	ProfileKey       string `json:"profileKey,omitempty"`
	TargetOS         string `json:"targetOs"`
	TargetArch       string `json:"targetArch"`
	SecretRef        string `json:"secretRef"`
	KeyGeneration    int    `json:"keyGeneration"`
	AuthKey          string `json:"authKey"`
}

type PackageIdentity struct {
	Kind             string `json:"kind"`
	ServerInstanceID string `json:"serverInstanceId"`
	PluginID         string `json:"pluginId"`
	RunEndpointID    string `json:"runEndpointId,omitempty"`
	ProfileKey       string `json:"profileKey,omitempty"`
	TargetOS         string `json:"targetOs"`
	TargetArch       string `json:"targetArch"`
	SecretRef        string `json:"secretRef"`
	KeyGeneration    int    `json:"keyGeneration"`
	KeyFingerprint   string `json:"keyFingerprint"`
}

type ComponentAuthResult struct {
	ServerInstanceID string
	Kind             string
	ProfileKey       string
	KeyGeneration    int
	Allowed          bool
	Reason           string
}

func LoadPackageConfig(path string) (PackageConfig, error) {
	body, err := os.ReadFile(path)
	if err != nil {
		return PackageConfig{}, fmt.Errorf("read run package config: %w", err)
	}
	var cfg PackageConfig
	if err := json.Unmarshal(body, &cfg); err != nil {
		return PackageConfig{}, fmt.Errorf("decode run package config: %w", err)
	}
	if err := ValidatePackageConfig(cfg); err != nil {
		return PackageConfig{}, err
	}
	return cfg, nil
}

func LoadPackageConfigFromEnv() (PackageConfig, bool, error) {
	path := strings.TrimSpace(os.Getenv(PackageConfigEnv))
	if path == "" {
		return PackageConfig{}, false, nil
	}
	cfg, err := LoadPackageConfig(path)
	return cfg, true, err
}

func LoadPackageConfigBesideExecutable() (PackageConfig, bool, error) {
	executable, err := os.Executable()
	if err != nil {
		return PackageConfig{}, false, nil
	}
	path := filepath.Join(filepath.Dir(executable), "config.json")
	if _, err := os.Stat(path); err != nil {
		if os.IsNotExist(err) {
			return PackageConfig{}, false, nil
		}
		return PackageConfig{}, false, err
	}
	cfg, err := LoadPackageConfig(path)
	return cfg, true, err
}

func ValidatePackageConfig(cfg PackageConfig) error {
	var violations []string
	if cfg.Kind != PackageComponentRun {
		violations = append(violations, "kind is invalid")
	}
	if !safeIdentifier(cfg.ServerInstanceID) {
		violations = append(violations, "serverInstanceId is invalid")
	}
	if !safePluginID(cfg.PluginID) {
		violations = append(violations, "pluginId is invalid")
	}
	if cfg.RunEndpointID != "" && !safeIdentifier(cfg.RunEndpointID) {
		violations = append(violations, "runEndpointId is invalid")
	}
	if cfg.ProfileKey != "" && !safeLogicalKey(cfg.ProfileKey) {
		violations = append(violations, "profileKey is invalid")
	}
	if !safeRuntimeTarget(cfg.TargetOS, cfg.TargetArch) {
		violations = append(violations, "target platform is invalid")
	}
	if !strings.HasPrefix(cfg.SecretRef, "secret://runtime-keys/") || strings.ContainsAny(cfg.SecretRef, " \t\r\n") {
		violations = append(violations, "secretRef is invalid")
	}
	if cfg.KeyGeneration <= 0 {
		violations = append(violations, "keyGeneration must be positive")
	}
	if strings.TrimSpace(cfg.AuthKey) == "" {
		violations = append(violations, "authKey is required")
	}
	if len(violations) > 0 {
		return fmt.Errorf("invalid run package config: %s", strings.Join(violations, "; "))
	}
	return nil
}

func ApplyPackageConfig(base Config, pkg PackageConfig) Config {
	base.RegistrationToken = pkg.AuthKey
	base.ServerInstanceID = pkg.ServerInstanceID
	base.PluginID = pkg.PluginID
	base.ComponentKind = pkg.Kind
	base.ComponentKey = packageComponentKey(pkg)
	base.KeyGeneration = pkg.KeyGeneration
	base.SecretRef = pkg.SecretRef
	if pkg.RunEndpointID != "" {
		base.RunEndpointID = pkg.RunEndpointID
	}
	if base.DisplayName == "" || base.DisplayName == DefaultDisplayName {
		base.DisplayName = "Run " + pkg.ServerInstanceID
	}
	return base
}

func (cfg PackageConfig) Identity() PackageIdentity {
	return PackageIdentity{
		Kind:             cfg.Kind,
		ServerInstanceID: cfg.ServerInstanceID,
		PluginID:         cfg.PluginID,
		RunEndpointID:    cfg.RunEndpointID,
		ProfileKey:       cfg.ProfileKey,
		TargetOS:         cfg.TargetOS,
		TargetArch:       cfg.TargetArch,
		SecretRef:        cfg.SecretRef,
		KeyGeneration:    cfg.KeyGeneration,
		KeyFingerprint:   fingerprint(cfg.AuthKey),
	}
}

func (cfg PackageConfig) IdentityDiagnostics() map[string]string {
	identity := cfg.Identity()
	return map[string]string{
		"kind":             identity.Kind,
		"serverInstanceId": identity.ServerInstanceID,
		"pluginId":         identity.PluginID,
		"runEndpointId":    identity.RunEndpointID,
		"profileKey":       identity.ProfileKey,
		"target":           identity.TargetOS + "/" + identity.TargetArch,
		"secretRef":        identity.SecretRef,
		"keyGeneration":    fmt.Sprintf("%d", identity.KeyGeneration),
		"keyFingerprint":   identity.KeyFingerprint,
	}
}

func AuthenticatePackageGeneration(pkg PackageConfig, auth ComponentAuthResult) error {
	if err := ValidatePackageConfig(pkg); err != nil {
		return err
	}
	if auth.ServerInstanceID != pkg.ServerInstanceID || auth.Kind != pkg.Kind || auth.ProfileKey != packageComponentKey(pkg) {
		return fmt.Errorf("component authentication scope does not match package")
	}
	if !auth.Allowed {
		return fmt.Errorf("component authentication rejected: %s", auth.Reason)
	}
	if auth.KeyGeneration != pkg.KeyGeneration {
		return fmt.Errorf("component key generation is no longer current")
	}
	return nil
}

func packageComponentKey(PackageConfig) string {
	return ""
}

func fingerprint(value string) string {
	sum := sha256.Sum256([]byte(value))
	return hex.EncodeToString(sum[:])[:12]
}

func safeIdentifier(value string) bool {
	value = strings.TrimSpace(value)
	if value == "" || len(value) > 120 {
		return false
	}
	for _, char := range value {
		if (char >= 'a' && char <= 'z') || (char >= 'A' && char <= 'Z') || (char >= '0' && char <= '9') || char == '_' || char == '-' || char == '.' {
			continue
		}
		return false
	}
	return true
}

func safePluginID(value string) bool {
	return strings.HasPrefix(value, "game.") && safeIdentifier(value)
}

func safeLogicalKey(value string) bool {
	value = strings.TrimSpace(value)
	if value == "" || len(value) > 120 || strings.HasPrefix(value, "/") || strings.Contains(value, "..") || strings.Contains(value, `\`) {
		return false
	}
	for _, char := range value {
		if (char >= 'a' && char <= 'z') || (char >= 'A' && char <= 'Z') || (char >= '0' && char <= '9') || char == '_' || char == '-' || char == '.' || char == '/' {
			continue
		}
		return false
	}
	return true
}

func safeRuntimeTarget(osName string, arch string) bool {
	switch osName {
	case "windows", "linux", "darwin":
	default:
		return false
	}
	switch arch {
	case "amd64", "arm64":
		return true
	default:
		return false
	}
}