package service

import (
	"context"
	"fmt"
	"strings"
	"time"

	"github.com/ez-api/ez-api/internal/model"
	groupx "github.com/ez-api/foundation/group"
	"github.com/ez-api/foundation/jsoncodec"
	"github.com/ez-api/foundation/tokenhash"
	"github.com/redis/go-redis/v9"
	"gorm.io/gorm"
)

type SyncService struct {
	rdb *redis.Client
}

func NewSyncService(rdb *redis.Client) *SyncService {
	return &SyncService{rdb: rdb}
}

// SyncKey writes a single key into Redis without rebuilding the entire snapshot.
func (s *SyncService) SyncKey(key *model.Key) error {
	ctx := context.Background()
	tokenHash := key.TokenHash
	if strings.TrimSpace(tokenHash) == "" {
		tokenHash = tokenhash.HashToken(key.KeySecret) // backward compatibility
	}
	if strings.TrimSpace(tokenHash) == "" {
		return fmt.Errorf("token hash missing for key %d", key.ID)
	}

	fields := map[string]interface{}{
		"master_id":       key.MasterID,
		"issued_at_epoch": key.IssuedAtEpoch,
		"status":          key.Status,
		"group":           key.Group,
		"scopes":          key.Scopes,
		"default_namespace": key.DefaultNamespace,
		"namespaces":        key.Namespaces,
	}
	if err := s.rdb.HSet(ctx, fmt.Sprintf("auth:token:%s", tokenHash), fields).Err(); err != nil {
		return fmt.Errorf("write auth token: %w", err)
	}
	return nil
}

// SyncMaster writes master metadata into Redis used by the balancer for validation.
func (s *SyncService) SyncMaster(master *model.Master) error {
	ctx := context.Background()
	key := fmt.Sprintf("auth:master:%d", master.ID)
	if err := s.rdb.HSet(ctx, key, map[string]interface{}{
		"epoch":      master.Epoch,
		"status":     master.Status,
		"global_qps": master.GlobalQPS,
	}).Err(); err != nil {
		return fmt.Errorf("write master metadata: %w", err)
	}
	return nil
}

// SyncProvider writes a single provider into Redis hash storage and updates routing tables.
func (s *SyncService) SyncProvider(provider *model.Provider) error {
	ctx := context.Background()
	group := groupx.Normalize(provider.Group)
	models := strings.Split(provider.Models, ",")

	snap := providerSnapshot{
		ID:             provider.ID,
		Name:           provider.Name,
		Type:           provider.Type,
		BaseURL:        provider.BaseURL,
		APIKey:         provider.APIKey,
		GoogleProject:  provider.GoogleProject,
		GoogleLocation: provider.GoogleLocation,
		Group:          group,
		Models:         models,
		Status:         normalizeStatus(provider.Status),
		AutoBan:        provider.AutoBan,
		BanReason:      provider.BanReason,
	}
	if provider.BanUntil != nil {
		snap.BanUntil = provider.BanUntil.UTC().Unix()
	}

	// 1. Update Provider Config
	if err := s.hsetJSON(ctx, "config:providers", fmt.Sprintf("%d", provider.ID), snap); err != nil {
		return err
	}

	// 2. Update Routing Table: route:group:{group}:{model} -> Set(provider_id)
	// Note: This is an additive operation. Removing models requires full sync or smarter logic.
	pipe := s.rdb.Pipeline()
	for _, m := range models {
		m = strings.TrimSpace(m)
		if m == "" {
			continue
		}
		if snap.Status != "active" {
			continue
		}
		if snap.BanUntil > 0 && time.Now().Unix() < snap.BanUntil {
			continue
		}
		routeKey := fmt.Sprintf("route:group:%s:%s", group, m)
		pipe.SAdd(ctx, routeKey, provider.ID)
	}
	_, err := pipe.Exec(ctx)
	return err
}

// SyncModel writes a single model metadata record.
func (s *SyncService) SyncModel(m *model.Model) error {
	ctx := context.Background()
	snap := modelSnapshot{
		Name:               m.Name,
		ContextWindow:      m.ContextWindow,
		CostPerToken:       m.CostPerToken,
		SupportsVision:     m.SupportsVision,
		SupportsFunction:   m.SupportsFunctions,
		SupportsToolChoice: m.SupportsToolChoice,
		SupportsFIM:        m.SupportsFIM,
		MaxOutputTokens:    m.MaxOutputTokens,
	}
	return s.hsetJSON(ctx, "meta:models", snap.Name, snap)
}

type providerSnapshot struct {
	ID             uint     `json:"id"`
	Name           string   `json:"name"`
	Type           string   `json:"type"`
	BaseURL        string   `json:"base_url"`
	APIKey         string   `json:"api_key"`
	GoogleProject  string   `json:"google_project,omitempty"`
	GoogleLocation string   `json:"google_location,omitempty"`
	Group          string   `json:"group"`
	Models         []string `json:"models"`
	Status         string   `json:"status"`
	AutoBan        bool     `json:"auto_ban"`
	BanReason      string   `json:"ban_reason,omitempty"`
	BanUntil       int64    `json:"ban_until,omitempty"` // unix seconds
}

// keySnapshot is no longer needed as we write directly to auth:token:*

type modelSnapshot struct {
	Name               string  `json:"name"`
	ContextWindow      int     `json:"context_window"`
	CostPerToken       float64 `json:"cost_per_token"`
	SupportsVision     bool    `json:"supports_vision"`
	SupportsFunction   bool    `json:"supports_functions"`
	SupportsToolChoice bool    `json:"supports_tool_choice"`
	SupportsFIM        bool    `json:"supports_fim"`
	MaxOutputTokens    int     `json:"max_output_tokens"`
}

// SyncAll rebuilds Redis hashes from the database; use for cold starts or forced refreshes.
func (s *SyncService) SyncAll(db *gorm.DB) error {
	ctx := context.Background()

	var providers []model.Provider
	if err := db.Find(&providers).Error; err != nil {
		return fmt.Errorf("load providers: %w", err)
	}

	var keys []model.Key
	if err := db.Find(&keys).Error; err != nil {
		return fmt.Errorf("load keys: %w", err)
	}

	var masters []model.Master
	if err := db.Find(&masters).Error; err != nil {
		return fmt.Errorf("load masters: %w", err)
	}

	var models []model.Model
	if err := db.Find(&models).Error; err != nil {
		return fmt.Errorf("load models: %w", err)
	}

	var bindings []model.Binding
	if err := db.Find(&bindings).Error; err != nil {
		return fmt.Errorf("load bindings: %w", err)
	}

	pipe := s.rdb.TxPipeline()
	pipe.Del(ctx, "config:providers", "config:keys", "meta:models", "config:bindings", "meta:bindings_meta")
	// Also clear master keys
	var masterKeys []string
	iter := s.rdb.Scan(ctx, 0, "auth:master:*", 0).Iterator()
	for iter.Next(ctx) {
		masterKeys = append(masterKeys, iter.Val())
	}
	if err := iter.Err(); err != nil {
		return fmt.Errorf("scan master keys: %w", err)
	}
	if len(masterKeys) > 0 {
		pipe.Del(ctx, masterKeys...)
	}

	// Clear old routing tables (pattern scan would be better in prod, but keys are predictable if we knew them)
	// For MVP, we rely on the fact that we are rebuilding.
	// Ideally, we should scan "route:group:*" and del, but let's just rebuild.

	for _, p := range providers {
		group := groupx.Normalize(p.Group)
		models := strings.Split(p.Models, ",")

		snap := providerSnapshot{
			ID:             p.ID,
			Name:           p.Name,
			Type:           p.Type,
			BaseURL:        p.BaseURL,
			APIKey:         p.APIKey,
			GoogleProject:  p.GoogleProject,
			GoogleLocation: p.GoogleLocation,
			Group:          group,
			Models:         models,
			Status:         normalizeStatus(p.Status),
			AutoBan:        p.AutoBan,
			BanReason:      p.BanReason,
		}
		if p.BanUntil != nil {
			snap.BanUntil = p.BanUntil.UTC().Unix()
		}
		payload, err := jsoncodec.Marshal(snap)
		if err != nil {
			return fmt.Errorf("marshal provider %d: %w", p.ID, err)
		}
		pipe.HSet(ctx, "config:providers", fmt.Sprintf("%d", p.ID), payload)

		// Rebuild Routing Table
		for _, m := range models {
			m = strings.TrimSpace(m)
			if m == "" {
				continue
			}
			if snap.Status != "active" {
				continue
			}
			if snap.BanUntil > 0 && time.Now().Unix() < snap.BanUntil {
				continue
			}
			routeKey := fmt.Sprintf("route:group:%s:%s", group, m)
			pipe.SAdd(ctx, routeKey, p.ID)
		}
	}

	for _, k := range keys {
		tokenHash := strings.TrimSpace(k.TokenHash)
		if tokenHash == "" {
			tokenHash = tokenhash.HashToken(k.KeySecret) // fallback for legacy rows
		}
		if tokenHash == "" {
			return fmt.Errorf("token hash missing for key %d", k.ID)
		}
		pipe.HSet(ctx, fmt.Sprintf("auth:token:%s", tokenHash), map[string]interface{}{
			"master_id":       k.MasterID,
			"issued_at_epoch": k.IssuedAtEpoch,
			"status":          k.Status,
			"group":           k.Group,
			"scopes":          k.Scopes,
			"default_namespace": k.DefaultNamespace,
			"namespaces":        k.Namespaces,
		})
	}

	for _, m := range masters {
		pipe.HSet(ctx, fmt.Sprintf("auth:master:%d", m.ID), map[string]interface{}{
			"epoch":      m.Epoch,
			"status":     m.Status,
			"global_qps": m.GlobalQPS,
		})
	}

	for _, m := range models {
		snap := modelSnapshot{
			Name:               m.Name,
			ContextWindow:      m.ContextWindow,
			CostPerToken:       m.CostPerToken,
			SupportsVision:     m.SupportsVision,
			SupportsFunction:   m.SupportsFunctions,
			SupportsToolChoice: m.SupportsToolChoice,
			SupportsFIM:        m.SupportsFIM,
			MaxOutputTokens:    m.MaxOutputTokens,
		}
		payload, err := jsoncodec.Marshal(snap)
		if err != nil {
			return fmt.Errorf("marshal model %s: %w", m.Name, err)
		}
		pipe.HSet(ctx, "meta:models", snap.Name, payload)
	}

	if err := s.writeBindingsSnapshot(ctx, pipe, bindings, providers); err != nil {
		return err
	}

	if _, err := pipe.Exec(ctx); err != nil {
		return fmt.Errorf("write snapshots: %w", err)
	}

	return nil
}

// SyncBindings rebuilds the binding snapshot for DP routing.
// This is intentionally a rebuild to avoid stale entries on deletes/updates.
func (s *SyncService) SyncBindings(db *gorm.DB) error {
	ctx := context.Background()

	var providers []model.Provider
	if err := db.Find(&providers).Error; err != nil {
		return fmt.Errorf("load providers: %w", err)
	}
	var bindings []model.Binding
	if err := db.Find(&bindings).Error; err != nil {
		return fmt.Errorf("load bindings: %w", err)
	}

	pipe := s.rdb.TxPipeline()
	pipe.Del(ctx, "config:bindings", "meta:bindings_meta")
	if err := s.writeBindingsSnapshot(ctx, pipe, bindings, providers); err != nil {
		return err
	}
	if _, err := pipe.Exec(ctx); err != nil {
		return fmt.Errorf("write bindings snapshot: %w", err)
	}
	return nil
}

func (s *SyncService) writeBindingsSnapshot(ctx context.Context, pipe redis.Pipeliner, bindings []model.Binding, providers []model.Provider) error {
	// Group providers by route group for selector resolution.
	type providerLite struct {
		id     uint
		group  string
		models []string
	}
	providersByGroup := make(map[string][]providerLite)
	for _, p := range providers {
		group := groupx.Normalize(p.Group)
		models := strings.Split(p.Models, ",")
		var outModels []string
		for _, m := range models {
			m = strings.TrimSpace(m)
			if m != "" {
				outModels = append(outModels, m)
			}
		}
		providersByGroup[group] = append(providersByGroup[group], providerLite{
			id:     p.ID,
			group:  group,
			models: outModels,
		})
	}

	now := time.Now().Unix()
	for _, b := range bindings {
		if strings.TrimSpace(b.Status) != "" && strings.TrimSpace(b.Status) != "active" {
			continue
		}
		ns := strings.TrimSpace(b.Namespace)
		pm := strings.TrimSpace(b.PublicModel)
		if ns == "" || pm == "" {
			continue
		}
		rg := groupx.Normalize(b.RouteGroup)
		if rg == "" {
			continue
		}

		snap := struct {
			Namespace     string            `json:"namespace"`
			PublicModel   string            `json:"public_model"`
			RouteGroup    string            `json:"route_group"`
			SelectorType  string            `json:"selector_type,omitempty"`
			SelectorValue string            `json:"selector_value,omitempty"`
			Status        string            `json:"status,omitempty"`
			UpdatedAt     int64             `json:"updated_at,omitempty"`
			Upstreams     map[string]string `json:"upstreams"`
		}{
			Namespace:     ns,
			PublicModel:   pm,
			RouteGroup:    rg,
			SelectorType:  strings.TrimSpace(b.SelectorType),
			SelectorValue: strings.TrimSpace(b.SelectorValue),
			Status:        "active",
			UpdatedAt:     now,
			Upstreams:     make(map[string]string),
		}

		selectorType := strings.TrimSpace(b.SelectorType)
		selectorValue := strings.TrimSpace(b.SelectorValue)

		for _, p := range providersByGroup[rg] {
			up, err := routing.ResolveUpstreamModel(routing.SelectorType(selectorType), selectorValue, pm, p.models)
			if err != nil {
				continue
			}
			snap.Upstreams[fmt.Sprintf("%d", p.id)] = up
		}

		// Only write bindings that have at least one usable upstream mapping.
		if len(snap.Upstreams) == 0 {
			continue
		}

		key := ns + "." + pm
		if err := s.hsetJSON(ctx, "config:bindings", key, snap); err != nil {
			return err
		}
	}

	meta := map[string]string{
		"version":    fmt.Sprintf("%d", now),
		"updated_at": fmt.Sprintf("%d", now),
		"source":     "cp_builtin",
	}
	if err := pipe.HSet(ctx, "meta:bindings_meta", meta).Err(); err != nil {
		return fmt.Errorf("write meta:bindings_meta: %w", err)
	}
	return nil
}

func (s *SyncService) hsetJSON(ctx context.Context, key, field string, val interface{}) error {
	payload, err := jsoncodec.Marshal(val)
	if err != nil {
		return fmt.Errorf("marshal %s:%s: %w", key, field, err)
	}
	if err := s.rdb.HSet(ctx, key, field, payload).Err(); err != nil {
		return fmt.Errorf("write %s:%s: %w", key, field, err)
	}
	return nil
}

func normalizeStatus(status string) string {
	st := strings.ToLower(strings.TrimSpace(status))
	if st == "" {
		return "active"
	}
	switch st {
	case "active", "auto_disabled", "manual_disabled":
		return st
	default:
		return st
	}
}