package migrate

import (
	"crypto/rand"
	"encoding/hex"
	"encoding/json"
	"errors"
	"fmt"
	"os"
	"strings"

	"github.com/ez-api/ez-api/internal/model"
	"github.com/ez-api/foundation/tokenhash"
	"golang.org/x/crypto/bcrypt"
	"gorm.io/gorm"
)

const (
	ConflictSkip      = "skip"
	ConflictOverwrite = "overwrite"
)

type ImportOptions struct {
	DryRun          bool
	ConflictPolicy  string
	IncludeBindings bool
}

type MasterCredential struct {
	Name      string `json:"name"`
	MasterKey string `json:"master_key"`
}

type ImportSummary struct {
	ProvidersCreated int `json:"providers_created"`
	ProvidersUpdated int `json:"providers_updated"`
	ProvidersSkipped int `json:"providers_skipped"`

	MastersCreated int `json:"masters_created"`
	MastersUpdated int `json:"masters_updated"`
	MastersSkipped int `json:"masters_skipped"`

	KeysCreated int `json:"keys_created"`
	KeysUpdated int `json:"keys_updated"`
	KeysSkipped int `json:"keys_skipped"`

	BindingsCreated int `json:"bindings_created"`
	BindingsUpdated int `json:"bindings_updated"`
	BindingsSkipped int `json:"bindings_skipped"`

	NamespacesCreated int `json:"namespaces_created"`

	MasterKeys []MasterCredential `json:"master_keys,omitempty"`
	Warnings   []string           `json:"warnings,omitempty"`
}

type Importer struct {
	db   *gorm.DB
	opts ImportOptions
}

func NewImporter(db *gorm.DB, opts ImportOptions) *Importer {
	opts.ConflictPolicy = strings.ToLower(strings.TrimSpace(opts.ConflictPolicy))
	if opts.ConflictPolicy == "" {
		opts.ConflictPolicy = ConflictSkip
	}
	return &Importer{db: db, opts: opts}
}

func (i *Importer) ImportFile(path string) (*ImportSummary, error) {
	raw, err := os.ReadFile(path)
	if err != nil {
		return nil, fmt.Errorf("read file: %w", err)
	}
	var payload ExportResult
	if err := json.Unmarshal(raw, &payload); err != nil {
		return nil, fmt.Errorf("parse json: %w", err)
	}
	return i.Import(&payload)
}

func (i *Importer) Import(payload *ExportResult) (*ImportSummary, error) {
	if payload == nil {
		return nil, errors.New("empty payload")
	}
	if i.db == nil {
		return nil, errors.New("db is required")
	}

	summary := &ImportSummary{}
	if len(payload.Warnings) > 0 {
		summary.Warnings = append(summary.Warnings, payload.Warnings...)
	}

	if err := i.ensureNamespaces(payload, summary); err != nil {
		return nil, err
	}

	masterMap, err := i.importMasters(payload.Data.Masters, summary)
	if err != nil {
		return nil, err
	}
	if err := i.importProviders(payload.Data.Providers, summary); err != nil {
		return nil, err
	}
	if err := i.importKeys(payload.Data.Keys, masterMap, summary); err != nil {
		return nil, err
	}
	if i.opts.IncludeBindings {
		if err := i.importBindings(payload.Data.Bindings, summary); err != nil {
			return nil, err
		}
	}

	return summary, nil
}

func (i *Importer) ensureNamespaces(payload *ExportResult, summary *ImportSummary) error {
	namespaceSet := make(map[string]struct{})
	namespaceSet["default"] = struct{}{}
	for _, master := range payload.Data.Masters {
		addNamespaces(namespaceSet, master.DefaultNamespace)
		addNamespaces(namespaceSet, master.Namespaces...)
	}
	for _, key := range payload.Data.Keys {
		addNamespaces(namespaceSet, key.Namespaces...)
	}
	if i.opts.IncludeBindings {
		for _, binding := range payload.Data.Bindings {
			addNamespaces(namespaceSet, binding.Namespace)
		}
	}

	for name := range namespaceSet {
		if err := i.ensureNamespace(name, summary); err != nil {
			return err
		}
	}
	return nil
}

func (i *Importer) ensureNamespace(name string, summary *ImportSummary) error {
	name = strings.TrimSpace(name)
	if name == "" {
		return nil
	}
	var existing model.Namespace
	err := i.db.Where("name = ?", name).First(&existing).Error
	if err == nil {
		return nil
	}
	if !errors.Is(err, gorm.ErrRecordNotFound) {
		return err
	}
	if i.opts.DryRun {
		summary.NamespacesCreated++
		return nil
	}
	ns := &model.Namespace{Name: name, Status: "active"}
	if err := i.db.Create(ns).Error; err != nil {
		return err
	}
	summary.NamespacesCreated++
	return nil
}

func (i *Importer) importMasters(items []Master, summary *ImportSummary) (map[string]model.Master, error) {
	out := make(map[string]model.Master)
	for _, item := range items {
		name := strings.TrimSpace(item.Name)
		if name == "" {
			summary.Warnings = append(summary.Warnings, "skip master with empty name")
			continue
		}
		var existing model.Master
		err := i.db.Where("name = ?", name).First(&existing).Error
		if err != nil && !errors.Is(err, gorm.ErrRecordNotFound) {
			return nil, err
		}
		if err == nil {
			out[name] = existing
			defaultNS := normalizeNamespace(item.DefaultNamespace)
			switch i.opts.ConflictPolicy {
			case ConflictOverwrite:
				if i.opts.DryRun {
					summary.MastersUpdated++
					continue
				}
				update := map[string]any{
					"group":             normalizeGroup(item.Group),
					"default_namespace": defaultNS,
					"namespaces":        normalizeNamespaces(item.Namespaces, defaultNS),
					"max_child_keys":    normalizeMaxChildKeys(item.MaxChildKeys),
					"global_qps":        item.GlobalQPS,
					"status":            normalizeStatus(item.Status, "active"),
				}
				if err := i.db.Model(&existing).Updates(update).Error; err != nil {
					return nil, err
				}
				out[name] = existing
				summary.MastersUpdated++
			default:
				summary.MastersSkipped++
			}
			continue
		}

		defaultNS := normalizeNamespace(item.DefaultNamespace)
		normalizedNamespaces := normalizeNamespaces(item.Namespaces, defaultNS)
		if i.opts.DryRun {
			summary.MastersCreated++
			out[name] = model.Master{
				Name:             name,
				Group:            normalizeGroup(item.Group),
				DefaultNamespace: defaultNS,
				Namespaces:       normalizedNamespaces,
				MaxChildKeys:     normalizeMaxChildKeys(item.MaxChildKeys),
				GlobalQPS:        item.GlobalQPS,
				Status:           normalizeStatus(item.Status, "active"),
				Epoch:            1,
			}
			continue
		}

		rawKey, err := generateRandomKey(32)
		if err != nil {
			return nil, err
		}
		hashedKey, err := bcrypt.GenerateFromPassword([]byte(rawKey), bcrypt.DefaultCost)
		if err != nil {
			return nil, err
		}
		digest := tokenhash.HashToken(rawKey)

		master := model.Master{
			Name:             name,
			MasterKey:        string(hashedKey),
			MasterKeyDigest:  digest,
			Group:            normalizeGroup(item.Group),
			DefaultNamespace: defaultNS,
			Namespaces:       normalizedNamespaces,
			MaxChildKeys:     normalizeMaxChildKeys(item.MaxChildKeys),
			GlobalQPS:        item.GlobalQPS,
			Status:           normalizeStatus(item.Status, "active"),
			Epoch:            1,
		}
		if err := i.db.Create(&master).Error; err != nil {
			return nil, err
		}
		out[name] = master
		summary.MastersCreated++
		summary.MasterKeys = append(summary.MasterKeys, MasterCredential{
			Name:      master.Name,
			MasterKey: rawKey,
		})
	}
	return out, nil
}

func (i *Importer) importProviders(items []Provider, summary *ImportSummary) error {
	groupCache := make(map[string]model.ProviderGroup)
	for _, item := range items {
		groupName := normalizeGroup(item.PrimaryGroup)
		if strings.TrimSpace(groupName) == "" {
			groupName = "default"
		}
		group, ok := groupCache[groupName]
		if !ok {
			var existing model.ProviderGroup
			err := i.db.Where("name = ?", groupName).First(&existing).Error
			if err != nil && !errors.Is(err, gorm.ErrRecordNotFound) {
				return err
			}
			if err == nil {
				group = existing
			} else {
				group = model.ProviderGroup{
					Name:    groupName,
					Type:    strings.TrimSpace(item.Type),
					BaseURL: strings.TrimSpace(item.BaseURL),
					Models:  strings.Join(item.Models, ","),
					Status:  normalizeStatus(item.Status, "active"),
				}
				if !i.opts.DryRun {
					if err := i.db.Create(&group).Error; err != nil {
						return err
					}
				}
			}
			groupCache[groupName] = group
		}

		apiKey := strings.TrimSpace(item.APIKey)
		if apiKey == "" {
			summary.Warnings = append(summary.Warnings, "skip api key with empty api_key")
			continue
		}
		var existingKey model.APIKey
		err := i.db.Where("group_id = ? AND api_key = ?", group.ID, apiKey).First(&existingKey).Error
		if err != nil && !errors.Is(err, gorm.ErrRecordNotFound) {
			return err
		}
		if err == nil {
			switch i.opts.ConflictPolicy {
			case ConflictOverwrite:
				if i.opts.DryRun {
					summary.ProvidersUpdated++
					continue
				}
				update := map[string]any{
					"weight":   resolveWeight(item.Weight, item.Priority),
					"status":   normalizeProviderStatus(item.Status),
					"auto_ban": item.AutoBan,
				}
				if err := i.db.Model(&existingKey).Updates(update).Error; err != nil {
					return err
				}
				summary.ProvidersUpdated++
			default:
				summary.ProvidersSkipped++
			}
			continue
		}

		if i.opts.DryRun {
			summary.ProvidersCreated++
			continue
		}

		key := model.APIKey{
			GroupID: group.ID,
			APIKey:  apiKey,
			Weight:  resolveWeight(item.Weight, item.Priority),
			Status:  normalizeProviderStatus(item.Status),
			AutoBan: item.AutoBan,
		}
		if err := i.db.Create(&key).Error; err != nil {
			return err
		}
		summary.ProvidersCreated++
	}
	return nil
}

func (i *Importer) importKeys(items []Key, masters map[string]model.Master, summary *ImportSummary) error {
	for _, item := range items {
		masterName := strings.TrimSpace(item.MasterRef)
		if masterName == "" {
			summary.Warnings = append(summary.Warnings, "skip key with empty master_ref")
			continue
		}
		master, ok := masters[masterName]
		if !ok {
			return fmt.Errorf("master not found for key: %s", masterName)
		}
		rawToken := strings.TrimSpace(item.OriginalToken)
		if rawToken == "" || !item.TokenPlaintextAvailable {
			summary.Warnings = append(summary.Warnings, fmt.Sprintf("skip key for master %s: missing plaintext token", masterName))
			continue
		}
		tokenHash := tokenhash.HashToken(rawToken)

		var existing model.Key
		err := i.db.Where("token_hash = ?", tokenHash).First(&existing).Error
		if err != nil && !errors.Is(err, gorm.ErrRecordNotFound) {
			return err
		}
		if err == nil {
			switch i.opts.ConflictPolicy {
			case ConflictOverwrite:
				if i.opts.DryRun {
					summary.KeysUpdated++
					continue
				}
				update := map[string]any{
					"master_id":            master.ID,
					"group":                normalizeGroup(item.Group, master.Group),
					"scopes":               strings.Join(item.Scopes, ","),
					"default_namespace":    normalizeNamespace(master.DefaultNamespace),
					"namespaces":           normalizeNamespaces(item.Namespaces, master.DefaultNamespace),
					"issued_at_epoch":      master.Epoch,
					"status":               normalizeStatus(item.Status, "active"),
					"issued_by":            "import",
					"model_limits":         strings.Join(item.ModelLimits, ","),
					"model_limits_enabled": item.ModelLimitsEnabled,
					"expires_at":           item.ExpiresAt,
					"allow_ips":            strings.Join(item.AllowIPs, ","),
					"quota_limit":          normalizeQuotaLimit(item.QuotaLimit, item.UnlimitedQuota, summary),
					"quota_used":           normalizeQuotaUsed(item.QuotaUsed),
				}
				if err := i.db.Model(&existing).Updates(update).Error; err != nil {
					return err
				}
				summary.KeysUpdated++
			default:
				summary.KeysSkipped++
			}
			continue
		}

		if i.opts.DryRun {
			summary.KeysCreated++
			continue
		}

		hashedKey, err := bcrypt.GenerateFromPassword([]byte(rawToken), bcrypt.DefaultCost)
		if err != nil {
			return err
		}

		key := model.Key{
			MasterID:           master.ID,
			KeySecret:          string(hashedKey),
			TokenHash:          tokenHash,
			Group:              normalizeGroup(item.Group, master.Group),
			Scopes:             strings.Join(item.Scopes, ","),
			DefaultNamespace:   normalizeNamespace(master.DefaultNamespace),
			Namespaces:         normalizeNamespaces(item.Namespaces, master.DefaultNamespace),
			IssuedAtEpoch:      master.Epoch,
			Status:             normalizeStatus(item.Status, "active"),
			IssuedBy:           "import",
			ModelLimits:        strings.Join(item.ModelLimits, ","),
			ModelLimitsEnabled: item.ModelLimitsEnabled,
			ExpiresAt:          item.ExpiresAt,
			AllowIPs:           strings.Join(item.AllowIPs, ","),
			QuotaLimit:         normalizeQuotaLimit(item.QuotaLimit, item.UnlimitedQuota, summary),
			QuotaUsed:          normalizeQuotaUsed(item.QuotaUsed),
		}
		if err := i.db.Create(&key).Error; err != nil {
			return err
		}
		summary.KeysCreated++
	}
	return nil
}

func (i *Importer) importBindings(items []Binding, summary *ImportSummary) error {
	for _, item := range items {
		ns := normalizeNamespace(item.Namespace, "default")
		publicModel := strings.TrimSpace(item.Model)
		if publicModel == "" {
			summary.Warnings = append(summary.Warnings, "skip binding with empty model")
			continue
		}
		groupName := normalizeGroup(item.RouteGroup)
		var group model.ProviderGroup
		if err := i.db.Where("name = ?", groupName).First(&group).Error; err != nil {
			summary.Warnings = append(summary.Warnings, "skip binding with missing provider group: "+groupName)
			continue
		}
		var existing model.Binding
		err := i.db.Where("namespace = ? AND public_model = ? AND group_id = ?", ns, publicModel, group.ID).First(&existing).Error
		if err != nil && !errors.Is(err, gorm.ErrRecordNotFound) {
			return err
		}
		if err == nil {
			switch i.opts.ConflictPolicy {
			case ConflictOverwrite:
				if i.opts.DryRun {
					summary.BindingsUpdated++
					continue
				}
				update := map[string]any{
					"group_id":       group.ID,
					"weight":         1,
					"selector_type":  "exact",
					"selector_value": publicModel,
					"status":         normalizeStatus(item.Status, "active"),
				}
				if err := i.db.Model(&existing).Updates(update).Error; err != nil {
					return err
				}
				summary.BindingsUpdated++
			default:
				summary.BindingsSkipped++
			}
			continue
		}

		if i.opts.DryRun {
			summary.BindingsCreated++
			continue
		}

		binding := model.Binding{
			Namespace:     ns,
			PublicModel:   publicModel,
			GroupID:       group.ID,
			Weight:        1,
			SelectorType:  "exact",
			SelectorValue: publicModel,
			Status:        normalizeStatus(item.Status, "active"),
		}
		if err := i.db.Create(&binding).Error; err != nil {
			return err
		}
		summary.BindingsCreated++
	}
	return nil
}

func addNamespaces(set map[string]struct{}, names ...string) {
	for _, name := range names {
		name = strings.TrimSpace(name)
		if name == "" {
			continue
		}
		set[name] = struct{}{}
	}
}

func normalizeGroup(values ...string) string {
	for _, v := range values {
		v = strings.TrimSpace(v)
		if v != "" {
			return v
		}
	}
	return "default"
}

func normalizeNamespace(values ...string) string {
	for _, v := range values {
		v = strings.TrimSpace(v)
		if v != "" {
			return v
		}
	}
	return "default"
}

func normalizeNamespaces(values []string, defaultNamespace string) string {
	if len(values) == 0 {
		return normalizeNamespace(defaultNamespace)
	}
	seen := make(map[string]struct{}, len(values))
	out := make([]string, 0, len(values))
	for _, v := range values {
		v = strings.TrimSpace(v)
		if v == "" {
			continue
		}
		if _, ok := seen[v]; ok {
			continue
		}
		seen[v] = struct{}{}
		out = append(out, v)
	}
	if len(out) == 0 {
		return normalizeNamespace(defaultNamespace)
	}
	if defaultNamespace != "" {
		if _, ok := seen[defaultNamespace]; !ok {
			out = append(out, defaultNamespace)
		}
	}
	return strings.Join(out, ",")
}

func normalizeMaxChildKeys(value int) int {
	if value > 0 {
		return value
	}
	return 5
}

func normalizeWeight(value int) int {
	if value > 0 {
		return value
	}
	return 1
}

func resolveWeight(weight int, priority int) int {
	if weight > 0 {
		return weight
	}
	if priority > 0 {
		return priority
	}
	return normalizeWeight(weight)
}

func normalizeProviderStatus(value string) string {
	value = strings.ToLower(strings.TrimSpace(value))
	if value == "" || value == "active" {
		return "active"
	}
	if value == "disabled" {
		return "manual_disabled"
	}
	return value
}

func normalizeStatus(value string, fallback string) string {
	value = strings.ToLower(strings.TrimSpace(value))
	if value == "" {
		return fallback
	}
	return value
}

func normalizeQuotaLimit(limit *int64, unlimited bool, summary *ImportSummary) int64 {
	if unlimited {
		return -1
	}
	if limit != nil {
		return *limit
	}
	if summary != nil {
		summary.Warnings = append(summary.Warnings, "quota_limit missing for limited key, defaulting to -1")
	}
	return -1
}

func normalizeQuotaUsed(used *int64) int64 {
	if used == nil {
		return 0
	}
	return *used
}

func generateRandomKey(length int) (string, error) {
	if length <= 0 {
		return "", errors.New("invalid key length")
	}
	buf := make([]byte, length)
	if _, err := rand.Read(buf); err != nil {
		return "", err
	}
	return hex.EncodeToString(buf), nil
}