package service

import (
	"context"
	"crypto/sha256"
	"encoding/hex"
	"encoding/json"
	"fmt"
	"strings"

	"github.com/ez-api/ez-api/internal/model"
	"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()
	snap := keySnapshot{
		ID:        key.ID,
		TokenHash: hashToken(key.KeySecret),
		Group:     normalizeGroup(key.Group),
		Status:    key.Status,
		Weight:    key.Weight,
		Balance:   key.Balance,
	}

	if err := s.hsetJSON(ctx, "config:keys", snap.TokenHash, snap); err != nil {
		return err
	}

	fields := map[string]interface{}{
		"status":  snap.Status,
		"group":   snap.Group,
		"weight":  snap.Weight,
		"balance": snap.Balance,
	}
	if err := s.rdb.HSet(ctx, fmt.Sprintf("auth:token:%s", snap.TokenHash), fields).Err(); err != nil {
		return fmt.Errorf("write auth token: %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 := normalizeGroup(provider.Group)
	models := strings.Split(provider.Models, ",")

	snap := providerSnapshot{
		ID:      provider.ID,
		Name:    provider.Name,
		Type:    provider.Type,
		BaseURL: provider.BaseURL,
		APIKey:  provider.APIKey,
		Group:   group,
		Models:  models,
	}

	// 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
		}
		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"`
	Group   string   `json:"group"`
	Models  []string `json:"models"`
}

type keySnapshot struct {
	ID        uint    `json:"id"`
	TokenHash string  `json:"token_hash"`
	Group     string  `json:"group"`
	Status    string  `json:"status"`
	Weight    int     `json:"weight"`
	Balance   float64 `json:"balance"`
}

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

	pipe := s.rdb.TxPipeline()
	pipe.Del(ctx, "config:providers", "config:keys", "meta:models")

	// 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 := normalizeGroup(p.Group)
		models := strings.Split(p.Models, ",")

		snap := providerSnapshot{
			ID:      p.ID,
			Name:    p.Name,
			Type:    p.Type,
			BaseURL: p.BaseURL,
			APIKey:  p.APIKey,
			Group:   group,
			Models:  models,
		}
		payload, err := json.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
			}
			routeKey := fmt.Sprintf("route:group:%s:%s", group, m)
			pipe.SAdd(ctx, routeKey, p.ID)
		}
	}

	for _, k := range keys {
		snap := keySnapshot{
			ID:        k.ID,
			TokenHash: hashToken(k.KeySecret),
			Group:     normalizeGroup(k.Group),
			Status:    k.Status,
			Weight:    k.Weight,
			Balance:   k.Balance,
		}
		payload, err := json.Marshal(snap)
		if err != nil {
			return fmt.Errorf("marshal key %d: %w", k.ID, err)
		}
		pipe.HSet(ctx, "config:keys", snap.TokenHash, payload)
		pipe.HSet(ctx, fmt.Sprintf("auth:token:%s", snap.TokenHash), map[string]interface{}{
			"status":  snap.Status,
			"group":   snap.Group,
			"weight":  snap.Weight,
			"balance": snap.Balance,
		})
	}

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

	return nil
}

func (s *SyncService) hsetJSON(ctx context.Context, key, field string, val interface{}) error {
	payload, err := json.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 hashToken(token string) string {
	hasher := sha256.New()
	hasher.Write([]byte(token))
	return hex.EncodeToString(hasher.Sum(nil))
}

func normalizeGroup(group string) string {
	if strings.TrimSpace(group) == "" {
		return "default"
	}
	return group
}