package platform

import (
	"crypto/ed25519"
	"crypto/rand"
	"encoding/json"
	"errors"
	"fmt"
	"net/url"
	"sort"
	"strconv"
	"strings"
	"time"

	"github.com/b1tsblog/license-platform/pkg/licensekit"
)

type IssueInput struct {
	CustomerUserID string           `json:"customerUserId,omitempty"`
	Customer       string           `json:"customer"`
	Product        string           `json:"product"`
	Edition        string           `json:"edition"`
	Features       []string         `json:"features,omitempty"`
	Limits         map[string]int64 `json:"limits,omitempty"`
	Domains        []string         `json:"domains,omitempty"`
	InstanceIDs    []string         `json:"instanceIds,omitempty"`
	Mode           string           `json:"mode"`
	Days           int              `json:"days"`
	LeaseMinutes   int              `json:"leaseMinutes"`
	GraceHours     int              `json:"graceHours"`
}

type LicenseView struct {
	LicenseID      string           `json:"licenseId"`
	Issuer         string           `json:"issuer"`
	Customer       string           `json:"customer"`
	CustomerUserID string           `json:"customerUserId,omitempty"`
	Product        string           `json:"product"`
	Edition        string           `json:"edition"`
	Features       []string         `json:"features,omitempty"`
	Limits         map[string]int64 `json:"limits,omitempty"`
	Domains        []string         `json:"domains,omitempty"`
	InstanceIDs    []string         `json:"instanceIds,omitempty"`
	Mode           string           `json:"mode"`
	ServerURL      string           `json:"serverUrl,omitempty"`
	ExpiresAt      int64            `json:"expiresAt"`
	Revoked        bool             `json:"revoked"`
	Reason         string           `json:"reason,omitempty"`
	Token          string           `json:"token,omitempty"`
	CreatedAt      int64            `json:"createdAt"`
	UpdatedAt      int64            `json:"updatedAt"`
}

type validateRequest struct {
	Token         string `json:"token"`
	Product       string `json:"product"`
	BaseURL       string `json:"baseUrl"`
	Host          string `json:"host,omitempty"`
	InstanceID    string `json:"instanceId,omitempty"`
	ClientVersion string `json:"clientVersion,omitempty"`
}

type validateResponse struct {
	Valid      bool   `json:"valid"`
	LeaseToken string `json:"leaseToken,omitempty"`
	ExpiresAt  string `json:"expiresAt,omitempty"`
	Reason     string `json:"reason,omitempty"`
}

func (s *Server) generateKeys(issuerKeyID, leaseKeyID string) error {
	issuerKeyID = strings.TrimSpace(issuerKeyID)
	leaseKeyID = strings.TrimSpace(leaseKeyID)
	if !validKeyID(issuerKeyID) || !validKeyID(leaseKeyID) {
		return errors.New("key IDs must be 1-120 URL-safe characters")
	}
	issuerPub, issuerPriv, err := ed25519.GenerateKey(rand.Reader)
	if err != nil {
		return err
	}
	leasePub, leasePriv, err := ed25519.GenerateKey(rand.Reader)
	if err != nil {
		return err
	}
	issuerCipher, err := s.vault.Encrypt(licensekit.EncodeKey(issuerPriv))
	if err != nil {
		return err
	}
	leaseCipher, err := s.vault.Encrypt(licensekit.EncodeKey(leasePriv))
	if err != nil {
		return err
	}
	return s.store.SetKeysOnce(KeySet{
		IssuerKeyID: issuerKeyID, IssuerPublicKey: licensekit.EncodeKey(issuerPub), IssuerPrivateCipher: issuerCipher,
		LeaseKeyID: leaseKeyID, LeasePublicKey: licensekit.EncodeKey(leasePub), LeasePrivateCipher: leaseCipher,
	})
}

func (s *Server) importKeys(issuerKeyID, issuerPrivateEncoded, leaseKeyID, leasePrivateEncoded string) error {
	issuerKeyID = strings.TrimSpace(issuerKeyID)
	leaseKeyID = strings.TrimSpace(leaseKeyID)
	if !validKeyID(issuerKeyID) || !validKeyID(leaseKeyID) {
		return errors.New("key IDs must be 1-120 URL-safe characters")
	}
	issuerPrivate, err := licensekit.DecodePrivateKey(strings.TrimSpace(issuerPrivateEncoded))
	if err != nil {
		return fmt.Errorf("issuer private key: %w", err)
	}
	leasePrivate, err := licensekit.DecodePrivateKey(strings.TrimSpace(leasePrivateEncoded))
	if err != nil {
		return fmt.Errorf("lease private key: %w", err)
	}
	issuerCipher, err := s.vault.Encrypt(licensekit.EncodeKey(issuerPrivate))
	if err != nil {
		return err
	}
	leaseCipher, err := s.vault.Encrypt(licensekit.EncodeKey(leasePrivate))
	if err != nil {
		return err
	}
	return s.store.SetKeysOnce(KeySet{
		IssuerKeyID: issuerKeyID, IssuerPublicKey: licensekit.EncodeKey(issuerPrivate.Public().(ed25519.PublicKey)), IssuerPrivateCipher: issuerCipher,
		LeaseKeyID: leaseKeyID, LeasePublicKey: licensekit.EncodeKey(leasePrivate.Public().(ed25519.PublicKey)), LeasePrivateCipher: leaseCipher,
	})
}

func (s *Server) trustStore() (licensekit.TrustStore, error) {
	keys, ok := s.store.KeySet()
	if !ok {
		return licensekit.TrustStore{}, errors.New("key pairs have not been initialized")
	}
	store := licensekit.NewTrustStore()
	store.LicenseKeys[keys.IssuerKeyID] = keys.IssuerPublicKey
	store.LeaseKeys[keys.LeaseKeyID] = keys.LeasePublicKey
	return store, nil
}

func (s *Server) issueLicense(actor User, input IssueInput) (LicenseRecord, string, error) {
	if actor.Role != RoleAdmin && actor.Role != RoleReseller {
		return LicenseRecord{}, "", errors.New("issuer role required")
	}
	keys, ok := s.store.KeySet()
	if !ok {
		return LicenseRecord{}, "", errors.New("key pairs have not been initialized")
	}
	input.Customer = strings.TrimSpace(input.Customer)
	input.Product = strings.TrimSpace(input.Product)
	input.Edition = strings.TrimSpace(input.Edition)
	if input.Customer == "" || input.Product == "" || input.Edition == "" {
		return LicenseRecord{}, "", errors.New("customer, product and edition are required")
	}
	if len(input.Customer) > 300 || len(input.Product) > 200 || len(input.Edition) > 100 {
		return LicenseRecord{}, "", errors.New("customer, product or edition is too long")
	}
	for _, value := range append(append([]string{}, input.Features...), append(input.Domains, input.InstanceIDs...)...) {
		if len(strings.TrimSpace(value)) > 300 {
			return LicenseRecord{}, "", errors.New("feature, domain or instance value is too long")
		}
	}
	mode, err := licensekit.ParseMode(input.Mode)
	if err != nil {
		return LicenseRecord{}, "", err
	}
	if input.Days < 1 || input.Days > 3650 {
		return LicenseRecord{}, "", errors.New("days must be between 1 and 3650")
	}
	if input.LeaseMinutes <= 0 {
		input.LeaseMinutes = 60
	}
	if input.LeaseMinutes > 1440 || input.GraceHours < 0 || input.GraceHours > 8760 {
		return LicenseRecord{}, "", errors.New("lease or grace duration is outside the allowed range")
	}
	if input.CustomerUserID != "" {
		customerUser, ok := s.store.GetUser(input.CustomerUserID)
		if !ok || customerUser.Role != RoleCustomer || !customerUser.Active {
			return LicenseRecord{}, "", errors.New("customer portal account was not found")
		}
		if actor.Role == RoleReseller && customerUser.ParentUserID != actor.ID {
			return LicenseRecord{}, "", errors.New("customer portal account is not assigned to this reseller")
		}
	}
	privateEncoded, err := s.vault.Decrypt(keys.IssuerPrivateCipher)
	if err != nil {
		return LicenseRecord{}, "", err
	}
	privateKey, err := licensekit.DecodePrivateKey(privateEncoded)
	if err != nil {
		return LicenseRecord{}, "", err
	}
	now := time.Now().UTC()
	licenseID := newID("lic")
	serverURL := ""
	if mode != licensekit.ModeOffline {
		serverURL = s.cfg.PublicURL
	}
	claims := licensekit.Claims{
		Version: 1, LicenseID: licenseID, Issuer: actor.DisplayName, Customer: input.Customer,
		Product: input.Product, Edition: input.Edition, Features: unique(input.Features), Limits: input.Limits,
		Domains: unique(input.Domains), InstanceIDs: unique(input.InstanceIDs), IssuedAt: now.Unix(),
		ExpiresAt:    now.Add(time.Duration(input.Days) * 24 * time.Hour).Unix(),
		Verification: licensekit.VerificationPolicy{Mode: mode, LeaseTTLSeconds: int64(time.Duration(input.LeaseMinutes) * time.Minute / time.Second), OfflineGraceSeconds: int64(time.Duration(input.GraceHours) * time.Hour / time.Second), ServerURL: serverURL},
		Metadata:     map[string]string{"issuedByUserId": actor.ID},
	}
	token, err := licensekit.SignLicense(privateKey, keys.IssuerKeyID, claims)
	if err != nil {
		return LicenseRecord{}, "", err
	}
	ciphertext, err := s.vault.Encrypt(token)
	if err != nil {
		return LicenseRecord{}, "", err
	}
	record := LicenseRecord{
		LicenseID: licenseID, TokenCipher: ciphertext, TokenHash: licensekit.TokenHash(token), Issuer: claims.Issuer,
		Customer: claims.Customer, CustomerUserID: input.CustomerUserID, IssuedByUserID: actor.ID,
		Product: claims.Product, Edition: claims.Edition, Features: claims.Features, Limits: claims.Limits,
		Domains: claims.Domains, InstanceIDs: claims.InstanceIDs, Mode: string(mode), ServerURL: serverURL, ExpiresAt: claims.ExpiresAt,
	}
	if err := s.store.PutLicense(record); err != nil {
		return LicenseRecord{}, "", err
	}
	stored, _ := s.store.GetLicense(licenseID)
	return stored, token, nil
}

func (s *Server) importLicense(actor User, token, customerUserID string) (LicenseRecord, error) {
	if actor.Role != RoleAdmin && actor.Role != RoleReseller {
		return LicenseRecord{}, errors.New("issuer role required")
	}
	token = strings.TrimSpace(token)
	if token == "" {
		return LicenseRecord{}, errors.New("license token is required")
	}
	trust, err := s.trustStore()
	if err != nil {
		return LicenseRecord{}, err
	}
	verified, err := licensekit.VerifyLicense(trust, token, time.Now().UTC())
	if err != nil {
		return LicenseRecord{}, err
	}
	claims := verified.Claims
	if existing, ok := s.store.GetLicense(claims.LicenseID); ok {
		if existing.TokenHash == licensekit.TokenHash(token) {
			return existing, nil
		}
		return LicenseRecord{}, errors.New("license ID already exists with another token")
	}
	if customerUserID != "" {
		customer, ok := s.store.GetUser(customerUserID)
		if !ok || customer.Role != RoleCustomer || !customer.Active {
			return LicenseRecord{}, errors.New("customer portal account was not found")
		}
		if actor.Role == RoleReseller && customer.ParentUserID != actor.ID {
			return LicenseRecord{}, errors.New("customer portal account is not assigned to this reseller")
		}
	}
	ciphertext, err := s.vault.Encrypt(token)
	if err != nil {
		return LicenseRecord{}, err
	}
	record := LicenseRecord{
		LicenseID: claims.LicenseID, TokenCipher: ciphertext, TokenHash: licensekit.TokenHash(token),
		Issuer: claims.Issuer, Customer: claims.Customer, CustomerUserID: customerUserID, IssuedByUserID: actor.ID,
		Product: claims.Product, Edition: claims.Edition, Features: claims.Features, Limits: claims.Limits,
		Domains: claims.Domains, InstanceIDs: claims.InstanceIDs, Mode: string(claims.Verification.Mode),
		ServerURL: strings.TrimRight(strings.TrimSpace(claims.Verification.ServerURL), "/"), ExpiresAt: claims.ExpiresAt,
	}
	if err := s.store.PutLicense(record); err != nil {
		return LicenseRecord{}, err
	}
	stored, _ := s.store.GetLicense(record.LicenseID)
	return stored, nil
}

func (s *Server) tokenFor(record LicenseRecord) (string, error) {
	return s.vault.Decrypt(record.TokenCipher)
}

func (s *Server) validateLicense(request validateRequest) (validateResponse, error) {
	store, err := s.trustStore()
	if err != nil {
		return validateResponse{Reason: err.Error()}, err
	}
	now := time.Now().UTC()
	verified, err := licensekit.VerifyLicense(store, request.Token, now)
	if err != nil {
		return validateResponse{Reason: err.Error()}, err
	}
	claims := verified.Claims
	if err := licensekit.ValidateLicenseContext(claims, request.Product, request.BaseURL, request.InstanceID); err != nil {
		return validateResponse{Reason: err.Error()}, err
	}
	record, ok := s.store.GetLicense(claims.LicenseID)
	if !ok {
		err := errors.New("license is not registered")
		return validateResponse{Reason: err.Error()}, err
	}
	if record.TokenHash != licensekit.TokenHash(request.Token) {
		err := errors.New("registered token does not match")
		return validateResponse{Reason: err.Error()}, err
	}
	if record.Revoked {
		reason := "license is revoked"
		if record.RevocationReason != "" {
			reason += ": " + record.RevocationReason
		}
		return validateResponse{Reason: reason}, errors.New(reason)
	}
	keys, _ := s.store.KeySet()
	leaseEncoded, err := s.vault.Decrypt(keys.LeasePrivateCipher)
	if err != nil {
		return validateResponse{Reason: "lease signing unavailable"}, err
	}
	leaseKey, err := licensekit.DecodePrivateKey(leaseEncoded)
	if err != nil {
		return validateResponse{Reason: "lease signing unavailable"}, err
	}
	ttl := s.cfg.DefaultLeaseTTL
	if claims.Verification.LeaseTTLSeconds > 0 {
		ttl = time.Duration(claims.Verification.LeaseTTLSeconds) * time.Second
	}
	if ttl > s.cfg.MaxLeaseTTL {
		ttl = s.cfg.MaxLeaseTTL
	}
	if remaining := time.Until(time.Unix(claims.ExpiresAt, 0)); ttl > remaining {
		ttl = remaining
	}
	if ttl <= 0 {
		return validateResponse{Reason: "license has expired"}, errors.New("license has expired")
	}
	host, _ := licensekit.HostFromBaseURL(request.BaseURL)
	leaseClaims := licensekit.LeaseClaims{Version: 1, LeaseID: newID("lease"), LicenseID: claims.LicenseID, Product: claims.Product, Customer: claims.Customer, Edition: claims.Edition, Features: claims.Features, Host: host, InstanceID: request.InstanceID, IssuedAt: now.Unix(), ExpiresAt: now.Add(ttl).Unix()}
	lease, err := licensekit.SignLease(leaseKey, keys.LeaseKeyID, leaseClaims)
	if err != nil {
		return validateResponse{Reason: "lease signing failed"}, err
	}
	return validateResponse{Valid: true, LeaseToken: lease, ExpiresAt: time.Unix(leaseClaims.ExpiresAt, 0).UTC().Format(time.RFC3339)}, nil
}

func licenseView(record LicenseRecord, token string) LicenseView {
	return LicenseView{LicenseID: record.LicenseID, Issuer: record.Issuer, Customer: record.Customer, CustomerUserID: record.CustomerUserID, Product: record.Product, Edition: record.Edition, Features: record.Features, Limits: record.Limits, Domains: record.Domains, InstanceIDs: record.InstanceIDs, Mode: record.Mode, ServerURL: record.ServerURL, ExpiresAt: record.ExpiresAt, Revoked: record.Revoked, Reason: record.RevocationReason, Token: token, CreatedAt: record.CreatedAt, UpdatedAt: record.UpdatedAt}
}

func parseIssueForm(values url.Values) (IssueInput, error) {
	days, err := parseBoundedInt(values.Get("days"), 1, 3650)
	if err != nil {
		return IssueInput{}, fmt.Errorf("days: %w", err)
	}
	leaseMinutes, err := parseBoundedInt(values.Get("leaseMinutes"), 1, 1440)
	if err != nil {
		return IssueInput{}, fmt.Errorf("lease minutes: %w", err)
	}
	graceHours, err := parseBoundedInt(values.Get("graceHours"), 0, 8760)
	if err != nil {
		return IssueInput{}, fmt.Errorf("grace hours: %w", err)
	}
	limits, err := parseLimits(values.Get("limits"))
	if err != nil {
		return IssueInput{}, err
	}
	return IssueInput{CustomerUserID: strings.TrimSpace(values.Get("customerUserId")), Customer: values.Get("customer"), Product: values.Get("product"), Edition: values.Get("edition"), Features: csv(values.Get("features")), Limits: limits, Domains: csv(values.Get("domains")), InstanceIDs: csv(values.Get("instances")), Mode: values.Get("mode"), Days: days, LeaseMinutes: leaseMinutes, GraceHours: graceHours}, nil
}

func parseBoundedInt(value string, min, max int) (int, error) {
	n, err := strconv.Atoi(strings.TrimSpace(value))
	if err != nil || n < min || n > max {
		return 0, fmt.Errorf("must be between %d and %d", min, max)
	}
	return n, nil
}

func parseLimits(value string) (map[string]int64, error) {
	limits := map[string]int64{}
	for _, line := range strings.Split(value, "\n") {
		line = strings.TrimSpace(line)
		if line == "" {
			continue
		}
		parts := strings.SplitN(line, "=", 2)
		if len(parts) != 2 || strings.TrimSpace(parts[0]) == "" {
			return nil, fmt.Errorf("invalid limit %q; expected name=value", line)
		}
		value, err := strconv.ParseInt(strings.TrimSpace(parts[1]), 10, 64)
		if err != nil || value < 0 {
			return nil, fmt.Errorf("invalid limit %q", line)
		}
		limits[strings.TrimSpace(parts[0])] = value
	}
	return limits, nil
}

func csv(value string) []string { return unique(strings.Split(value, ",")) }

func unique(values []string) []string {
	seen := map[string]bool{}
	out := make([]string, 0, len(values))
	for _, value := range values {
		value = strings.TrimSpace(value)
		if value != "" && !seen[value] {
			seen[value] = true
			out = append(out, value)
		}
	}
	sort.Strings(out)
	return out
}

func newID(prefix string) string {
	raw, err := randomToken(12)
	if err != nil {
		return fmt.Sprintf("%s_%d", prefix, time.Now().UTC().UnixNano())
	}
	return prefix + "_" + raw
}

func trustStoreJSON(store licensekit.TrustStore) string {
	data, _ := json.MarshalIndent(store, "", "  ")
	return string(data)
}

func validKeyID(value string) bool {
	if len(value) < 1 || len(value) > 120 {
		return false
	}
	for _, r := range value {
		if (r >= 'a' && r <= 'z') || (r >= 'A' && r <= 'Z') || (r >= '0' && r <= '9') || r == '.' || r == '-' || r == '_' || r == ':' {
			continue
		}
		return false
	}
	return true
}