package service

import (
	"archive/tar"
	"bytes"
	"compress/gzip"
	"context"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"net/url"
	"os"
	"path/filepath"
	"regexp"
	"strings"
	"sync"
	"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/modelcap"
	"github.com/ez-api/foundation/routing"
	"github.com/pelletier/go-toml/v2"
	"github.com/redis/go-redis/v9"
	"gorm.io/gorm"
)

type ModelRegistryConfig struct {
	Enabled      bool
	RefreshEvery time.Duration

	ModelsDevBaseURL    string
	ModelsDevAPIBaseURL string
	ModelsDevRef        string

	CacheDir string
	Timeout  time.Duration
}

type ModelRegistryService struct {
	db  *gorm.DB
	rdb *redis.Client

	cfg    ModelRegistryConfig
	client *http.Client

	mu           sync.Mutex
	lastError    string
	lastRefresh  time.Time
	lastApplied  modelcap.Meta
	lastUpstream string
}

func NewModelRegistryService(db *gorm.DB, rdb *redis.Client, cfg ModelRegistryConfig) *ModelRegistryService {
	if cfg.RefreshEvery <= 0 {
		cfg.RefreshEvery = 30 * time.Minute
	}
	if strings.TrimSpace(cfg.ModelsDevBaseURL) == "" {
		cfg.ModelsDevBaseURL = "https://codeload.github.com/sst/models.dev/tar.gz"
	}
	if strings.TrimSpace(cfg.ModelsDevAPIBaseURL) == "" {
		cfg.ModelsDevAPIBaseURL = "https://api.github.com"
	}
	if strings.TrimSpace(cfg.ModelsDevRef) == "" {
		cfg.ModelsDevRef = "dev"
	}
	if strings.TrimSpace(cfg.CacheDir) == "" {
		cfg.CacheDir = "./data/model-registry"
	}
	if cfg.Timeout <= 0 {
		cfg.Timeout = 30 * time.Second
	}
	return &ModelRegistryService{
		db:  db,
		rdb: rdb,
		cfg: cfg,
		client: &http.Client{
			Timeout: cfg.Timeout,
		},
	}
}

func (s *ModelRegistryService) Start(ctx context.Context) {
	if !s.cfg.Enabled {
		return
	}
	go func() {
		ticker := time.NewTicker(s.cfg.RefreshEvery)
		defer ticker.Stop()

		// Best-effort initial refresh.
		_ = s.Refresh(ctx, "")

		for {
			select {
			case <-ctx.Done():
				return
			case <-ticker.C:
				_ = s.Refresh(ctx, "")
			}
		}
	}()
}

type ModelRegistryStatus struct {
	Enabled       bool               `json:"enabled"`
	ModelsDevRef  string             `json:"models_dev_ref"`
	ModelsDevURL  string             `json:"models_dev_url"`
	LastRefreshAt int64              `json:"last_refresh_at,omitempty"`
	LastError     string             `json:"last_error,omitempty"`
	RedisMeta     map[string]string  `json:"redis_meta,omitempty"`
	CacheCurrent  *modelRegistryFile `json:"cache_current,omitempty"`
	CachePrev     *modelRegistryFile `json:"cache_prev,omitempty"`
}

func (s *ModelRegistryService) Status(ctx context.Context) (*ModelRegistryStatus, error) {
	s.mu.Lock()
	lastErr := s.lastError
	lastRefresh := s.lastRefresh
	s.mu.Unlock()

	redisMeta, _ := s.rdb.HGetAll(ctx, "meta:models_meta").Result()

	current, _ := readModelRegistryFile(filepath.Join(s.cfg.CacheDir, "current.json"))
	prev, _ := readModelRegistryFile(filepath.Join(s.cfg.CacheDir, "prev.json"))

	out := &ModelRegistryStatus{
		Enabled:      s.cfg.Enabled,
		ModelsDevRef: s.cfg.ModelsDevRef,
		ModelsDevURL: strings.TrimRight(s.cfg.ModelsDevBaseURL, "/") + "/" + s.cfg.ModelsDevRef,
		LastError:    lastErr,
		RedisMeta:    redisMeta,
		CacheCurrent: current,
		CachePrev:    prev,
	}
	if !lastRefresh.IsZero() {
		out.LastRefreshAt = lastRefresh.Unix()
	}
	return out, nil
}

type ModelRegistryCheckResult struct {
	Enabled            bool   `json:"enabled"`
	UpstreamRef        string `json:"upstream_ref"`
	CurrentVersion     string `json:"current_version,omitempty"`
	LatestVersion      string `json:"latest_version,omitempty"`
	NeedsRefresh       bool   `json:"needs_refresh"`
	CurrentUpstreamRef string `json:"current_upstream_ref,omitempty"`
}

func (s *ModelRegistryService) Check(ctx context.Context, ref string) (*ModelRegistryCheckResult, error) {
	if strings.TrimSpace(ref) == "" {
		ref = s.cfg.ModelsDevRef
	}

	latest, err := s.fetchModelsDevRefSHA(ctx, ref)
	if err != nil {
		return nil, err
	}

	meta, _ := s.rdb.HGetAll(ctx, "meta:models_meta").Result()
	currentVersion := strings.TrimSpace(meta["version"])
	currentUpstreamRef := strings.TrimSpace(meta["upstream_ref"])

	needsRefresh := currentVersion == "" || !versionsEqual(currentVersion, latest)

	return &ModelRegistryCheckResult{
		Enabled:            s.cfg.Enabled,
		UpstreamRef:        ref,
		CurrentVersion:     currentVersion,
		LatestVersion:      latest,
		NeedsRefresh:       needsRefresh,
		CurrentUpstreamRef: currentUpstreamRef,
	}, nil
}

func (s *ModelRegistryService) Refresh(ctx context.Context, ref string) error {
	if strings.TrimSpace(ref) == "" {
		ref = s.cfg.ModelsDevRef
	}

	s.mu.Lock()
	s.lastUpstream = ref
	s.mu.Unlock()

	tarballURL := strings.TrimRight(s.cfg.ModelsDevBaseURL, "/") + "/" + ref
	reg, version, err := s.fetchModelsDev(ctx, tarballURL)
	if err != nil {
		s.setError(err)
		return err
	}

	models, payloads, err := s.buildBindingModels(ctx, reg)
	if err != nil {
		s.setError(err)
		return err
	}

	// Overlay explicit DB entries (admin overrides).
	var dbModels []model.Model
	if err := s.db.Find(&dbModels).Error; err != nil {
		s.setError(fmt.Errorf("load db models: %w", err))
		return err
	}
	for _, m := range dbModels {
		snap := modelcap.Model{
			Name:               m.Name,
			Kind:               string(modelcap.NormalizeKind(m.Kind)),
			ContextWindow:      m.ContextWindow,
			CostPerToken:       m.CostPerToken,
			SupportsVision:     m.SupportsVision,
			SupportsFunction:   m.SupportsFunctions,
			SupportsToolChoice: m.SupportsToolChoice,
			SupportsFim:        m.SupportsFIM,
			SupportsStream:     true,
			MaxOutputTokens:    m.MaxOutputTokens,
		}.Normalized()
		b, err := jsoncodec.Marshal(snap)
		if err != nil {
			s.setError(fmt.Errorf("marshal db model %s: %w", m.Name, err))
			return err
		}
		models[snap.Name] = snap
		payloads[snap.Name] = string(b)
	}

	now := time.Now().Unix()
	meta := modelcap.Meta{
		Version:     version,
		UpdatedAt:   fmt.Sprintf("%d", now),
		Source:      "models.dev",
		Checksum:    modelcap.ChecksumFromPayloads(payloads),
		UpstreamURL: "https://github.com/sst/models.dev",
		UpstreamRef: ref,
	}

	if err := s.applyToRedis(ctx, models, payloads, meta); err != nil {
		s.setError(err)
		return err
	}
	if err := s.persistCache(models, meta); err != nil {
		s.setError(err)
		return err
	}

	s.mu.Lock()
	s.lastError = ""
	s.lastRefresh = time.Now()
	s.lastApplied = meta
	s.mu.Unlock()
	return nil
}

func (s *ModelRegistryService) Rollback(ctx context.Context) error {
	prevPath := filepath.Join(s.cfg.CacheDir, "prev.json")
	prev, err := readModelRegistryFile(prevPath)
	if err != nil {
		s.setError(fmt.Errorf("read prev cache: %w", err))
		return err
	}
	if prev == nil {
		s.setError(fmt.Errorf("no prev cache"))
		return fmt.Errorf("no prev cache")
	}

	payloads := make(map[string]string, len(prev.Models))
	for name, m := range prev.Models {
		m = m.Normalized()
		b, err := jsoncodec.Marshal(m)
		if err != nil {
			s.setError(fmt.Errorf("marshal cached model %s: %w", name, err))
			return err
		}
		prev.Models[name] = m
		payloads[name] = string(b)
	}
	prev.Meta.Checksum = modelcap.ChecksumFromPayloads(payloads)
	prev.Meta.Source = "rollback"
	prev.Meta.UpdatedAt = fmt.Sprintf("%d", time.Now().Unix())

	if err := s.applyToRedis(ctx, prev.Models, payloads, prev.Meta); err != nil {
		s.setError(err)
		return err
	}
	// Swap cache current/prev to reflect rollback.
	if err := s.persistCache(prev.Models, prev.Meta); err != nil {
		s.setError(err)
		return err
	}
	s.mu.Lock()
	s.lastError = ""
	s.lastRefresh = time.Now()
	s.lastApplied = prev.Meta
	s.mu.Unlock()
	return nil
}

func (s *ModelRegistryService) setError(err error) {
	s.mu.Lock()
	defer s.mu.Unlock()
	s.lastError = err.Error()
	s.lastRefresh = time.Now()
}

func (s *ModelRegistryService) fetchModelsDevRefSHA(ctx context.Context, ref string) (string, error) {
	base := strings.TrimRight(strings.TrimSpace(s.cfg.ModelsDevAPIBaseURL), "/")
	if base == "" {
		base = "https://api.github.com"
	}

	u := base + "/repos/sst/models.dev/commits/" + url.PathEscape(strings.TrimSpace(ref))
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, u, nil)
	if err != nil {
		return "", err
	}
	req.Header.Set("Accept", "application/vnd.github+json")
	req.Header.Set("User-Agent", "ez-api")

	resp, err := s.client.Do(req)
	if err != nil {
		return "", err
	}
	defer resp.Body.Close()
	if resp.StatusCode/100 != 2 {
		b, _ := io.ReadAll(io.LimitReader(resp.Body, 8<<10))
		return "", fmt.Errorf("models.dev commit check failed: %s body=%s", resp.Status, string(b))
	}

	var payload struct {
		SHA string `json:"sha"`
	}
	if err := json.NewDecoder(io.LimitReader(resp.Body, 1<<20)).Decode(&payload); err != nil {
		return "", fmt.Errorf("decode github commit: %w", err)
	}
	sha := strings.TrimSpace(payload.SHA)
	if sha == "" {
		return "", fmt.Errorf("github commit sha missing for ref %q", ref)
	}
	return sha, nil
}

func versionsEqual(current, latest string) bool {
	c := strings.TrimSpace(current)
	l := strings.TrimSpace(latest)
	if c == "" || l == "" {
		return false
	}
	if len(c) <= len(l) && strings.HasPrefix(l, c) {
		return true
	}
	if len(l) <= len(c) && strings.HasPrefix(c, l) {
		return true
	}
	return false
}

type boolVal struct {
	Known bool
	Val   bool
}

type intVal struct {
	Known bool
	Val   int
}

type upstreamCap struct {
	ContextWindow   intVal
	MaxOutputTokens intVal
	SupportsVision  boolVal
	SupportsTools   boolVal
}

type modelsDevRegistry struct {
	ByProviderModel map[string]upstreamCap // key: providerID|modelID
	ByModel         map[string]upstreamCap // fallback: modelID
}

var shaSuffix = regexp.MustCompile(`-([0-9a-f]{7,40})$`)

func (s *ModelRegistryService) fetchModelsDev(ctx context.Context, tarballURL string) (*modelsDevRegistry, string, error) {
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, tarballURL, nil)
	if err != nil {
		return nil, "", err
	}
	resp, err := s.client.Do(req)
	if err != nil {
		return nil, "", err
	}
	defer resp.Body.Close()
	if resp.StatusCode/100 != 2 {
		b, _ := io.ReadAll(io.LimitReader(resp.Body, 8<<10))
		return nil, "", fmt.Errorf("models.dev fetch failed: %s body=%s", resp.Status, string(b))
	}
	tarball, err := io.ReadAll(resp.Body)
	if err != nil {
		return nil, "", err
	}

	gr, err := gzip.NewReader(bytes.NewReader(tarball))
	if err != nil {
		return nil, "", err
	}
	defer gr.Close()

	tr := tar.NewReader(gr)
	reg := &modelsDevRegistry{
		ByProviderModel: make(map[string]upstreamCap),
		ByModel:         make(map[string]upstreamCap),
	}

	version := ""
	for {
		hdr, err := tr.Next()
		if err == io.EOF {
			break
		}
		if err != nil {
			return nil, "", err
		}
		name := hdr.Name
		if version == "" {
			if parts := strings.SplitN(name, "/", 2); len(parts) > 0 {
				if m := shaSuffix.FindStringSubmatch(parts[0]); len(m) == 2 {
					version = m[1]
				}
			}
		}
		if hdr.Typeflag != tar.TypeReg {
			continue
		}
		if !strings.HasSuffix(name, ".toml") {
			continue
		}
		providerID, modelID, ok := parseModelsDevModelPath(name)
		if !ok {
			continue
		}

		data, err := io.ReadAll(io.LimitReader(tr, 1<<20))
		if err != nil {
			return nil, "", err
		}
		cap, ok := parseModelsDevTOML(data)
		if !ok {
			continue
		}
		key := providerID + "|" + modelID
		reg.ByProviderModel[key] = cap
		if _, exists := reg.ByModel[modelID]; !exists {
			reg.ByModel[modelID] = cap
		}
		// Also store a flattened variant for providers that may use subdirs.
		if alt := strings.ReplaceAll(modelID, "/", "-"); alt != modelID {
			if _, exists := reg.ByModel[alt]; !exists {
				reg.ByModel[alt] = cap
			}
			altKey := providerID + "|" + alt
			if _, exists := reg.ByProviderModel[altKey]; !exists {
				reg.ByProviderModel[altKey] = cap
			}
		}
	}
	if version == "" {
		version = fmt.Sprintf("%d", time.Now().Unix())
	}
	return reg, version, nil
}

func parseModelsDevModelPath(path string) (providerID string, modelID string, ok bool) {
	parts := strings.Split(path, "/")
	for i := 0; i < len(parts); i++ {
		if parts[i] != "providers" {
			continue
		}
		if i+3 >= len(parts) {
			return "", "", false
		}
		providerID = strings.TrimSpace(parts[i+1])
		if providerID == "" {
			return "", "", false
		}
		if parts[i+2] != "models" {
			return "", "", false
		}
		modelPart := strings.Join(parts[i+3:], "/")
		modelPart = strings.TrimSuffix(modelPart, ".toml")
		modelPart = strings.TrimSpace(modelPart)
		if modelPart == "" {
			return "", "", false
		}
		return providerID, modelPart, true
	}
	return "", "", false
}

func parseModelsDevTOML(data []byte) (upstreamCap, bool) {
	var doc map[string]any
	if err := toml.Unmarshal(data, &doc); err != nil {
		return upstreamCap{}, false
	}

	var cap upstreamCap

	if v, ok := getBool(doc, "tool_call"); ok {
		cap.SupportsTools = boolVal{Known: true, Val: v}
	}
	if limit, ok := getMap(doc, "limit"); ok {
		if v, ok := getInt(limit, "context"); ok {
			cap.ContextWindow = intVal{Known: true, Val: v}
		}
		if v, ok := getInt(limit, "output"); ok {
			cap.MaxOutputTokens = intVal{Known: true, Val: v}
		}
	}
	if mods, ok := getMap(doc, "modalities"); ok {
		if input, ok := getStringSlice(mods["input"]); ok {
			hasImage := false
			for _, it := range input {
				if strings.EqualFold(strings.TrimSpace(it), "image") {
					hasImage = true
					break
				}
			}
			cap.SupportsVision = boolVal{Known: true, Val: hasImage}
		}
	}

	if !cap.SupportsTools.Known && !cap.SupportsVision.Known && !cap.ContextWindow.Known && !cap.MaxOutputTokens.Known {
		return upstreamCap{}, false
	}
	return cap, true
}

func getMap(doc map[string]any, key string) (map[string]any, bool) {
	if doc == nil {
		return nil, false
	}
	v, ok := doc[key]
	if !ok || v == nil {
		return nil, false
	}
	m, ok := v.(map[string]any)
	return m, ok
}

func getBool(doc map[string]any, key string) (bool, bool) {
	v, ok := doc[key]
	if !ok || v == nil {
		return false, false
	}
	switch b := v.(type) {
	case bool:
		return b, true
	default:
		return false, false
	}
}

func getInt(doc map[string]any, key string) (int, bool) {
	v, ok := doc[key]
	if !ok || v == nil {
		return 0, false
	}
	switch n := v.(type) {
	case int64:
		return int(n), true
	case int:
		return n, true
	case float64:
		return int(n), true
	default:
		return 0, false
	}
}

func getStringSlice(v any) ([]string, bool) {
	if v == nil {
		return nil, false
	}
	switch s := v.(type) {
	case []any:
		out := make([]string, 0, len(s))
		for _, it := range s {
			if str, ok := it.(string); ok {
				out = append(out, str)
			}
		}
		return out, true
	case []string:
		return append([]string(nil), s...), true
	default:
		return nil, false
	}
}

type capAgg struct {
	kind string

	visionAnyTrue  bool
	visionAllKnown bool
	visionKnownAny bool

	toolsAnyTrue  bool
	toolsAllKnown bool
	toolsKnownAny bool

	maxOutputKnown bool
	maxOutputMax   int

	contextKnown bool
	contextMax   int
}

func inferKindFromPublicModel(publicModel string) string {
	pm := strings.ToLower(strings.TrimSpace(publicModel))
	if strings.Contains(pm, "embedding") {
		return string(modelcap.KindEmbedding)
	}
	if strings.Contains(pm, "rerank") {
		return string(modelcap.KindRerank)
	}
	return string(modelcap.KindChat)
}

func (a *capAgg) merge(cap upstreamCap, ok bool) {
	if ok {
		// vision
		if cap.SupportsVision.Known {
			a.visionKnownAny = true
			if cap.SupportsVision.Val {
				a.visionAnyTrue = true
			}
		} else {
			a.visionAllKnown = false
		}
		// tools
		if cap.SupportsTools.Known {
			a.toolsKnownAny = true
			if cap.SupportsTools.Val {
				a.toolsAnyTrue = true
			}
		} else {
			a.toolsAllKnown = false
		}
		// limits
		if cap.MaxOutputTokens.Known && cap.MaxOutputTokens.Val > 0 {
			a.maxOutputKnown = true
			if cap.MaxOutputTokens.Val > a.maxOutputMax {
				a.maxOutputMax = cap.MaxOutputTokens.Val
			}
		}
		if cap.ContextWindow.Known && cap.ContextWindow.Val > 0 {
			a.contextKnown = true
			if cap.ContextWindow.Val > a.contextMax {
				a.contextMax = cap.ContextWindow.Val
			}
		}
		return
	}
	// Unknown upstream capability: do not force blocking, treat as "not all known".
	a.visionAllKnown = false
	a.toolsAllKnown = false
}

func (a *capAgg) finalize(name string) modelcap.Model {
	// Safe defaults: unknown -> allow (true) so we avoid false blocking.
	supportsVision := true
	if a.visionKnownAny {
		if a.visionAnyTrue {
			supportsVision = true
		} else if a.visionAllKnown {
			supportsVision = false
		}
	}

	supportsTools := true
	if a.toolsKnownAny {
		if a.toolsAnyTrue {
			supportsTools = true
		} else if a.toolsAllKnown {
			supportsTools = false
		}
	}

	out := modelcap.Model{
		Name:               name,
		Kind:               string(modelcap.NormalizeKind(a.kind)),
		ContextWindow:      0,
		CostPerToken:       0,
		SupportsVision:     supportsVision,
		SupportsFunction:   supportsTools,
		SupportsToolChoice: true,
		SupportsFim:        true,
		SupportsStream:     true,
		MaxOutputTokens:    0,
	}
	if a.contextKnown {
		out.ContextWindow = a.contextMax
	}
	if a.maxOutputKnown {
		out.MaxOutputTokens = a.maxOutputMax
	}
	return out.Normalized()
}

func (s *ModelRegistryService) buildBindingModels(ctx context.Context, reg *modelsDevRegistry) (map[string]modelcap.Model, map[string]string, error) {
	var providers []model.Provider
	if err := s.db.Find(&providers).Error; err != nil {
		return nil, nil, fmt.Errorf("load providers: %w", err)
	}
	var bindings []model.Binding
	if err := s.db.Find(&bindings).Error; err != nil {
		return nil, nil, fmt.Errorf("load bindings: %w", err)
	}

	type providerLite struct {
		id     uint
		group  string
		ptype  string
		models []string
	}
	providersByGroup := make(map[string][]providerLite)
	now := time.Now().Unix()
	for _, p := range providers {
		if strings.TrimSpace(p.Status) != "" && strings.TrimSpace(p.Status) != "active" {
			continue
		}
		if p.BanUntil != nil && p.BanUntil.UTC().Unix() > now {
			continue
		}
		group := groupx.Normalize(p.Group)
		rawModels := strings.Split(p.Models, ",")
		var outModels []string
		for _, m := range rawModels {
			m = strings.TrimSpace(m)
			if m != "" {
				outModels = append(outModels, m)
			}
		}
		if group == "" || len(outModels) == 0 {
			continue
		}
		providersByGroup[group] = append(providersByGroup[group], providerLite{
			id:     p.ID,
			group:  group,
			ptype:  strings.TrimSpace(p.Type),
			models: outModels,
		})
	}

	modelsOut := make(map[string]modelcap.Model)
	payloads := make(map[string]string)

	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
		}
		key := ns + "." + pm
		rg := groupx.Normalize(b.RouteGroup)
		if rg == "" {
			continue
		}
		pgroup := providersByGroup[rg]
		if len(pgroup) == 0 {
			continue
		}

		agg := &capAgg{
			kind:           inferKindFromPublicModel(pm),
			visionAllKnown: true,
			toolsAllKnown:  true,
		}

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

		for _, p := range pgroup {
			up, err := routing.ResolveUpstreamModel(selectorType, selectorValue, pm, p.models)
			if err != nil {
				continue
			}
			cap, ok := lookupModelsDevCap(reg, modelsDevProviderKey(p.ptype), up)
			agg.merge(cap, ok)
		}

		out := agg.finalize(key)
		bs, err := jsoncodec.Marshal(out)
		if err != nil {
			return nil, nil, fmt.Errorf("marshal model %s: %w", key, err)
		}
		modelsOut[key] = out
		payloads[key] = string(bs)
	}

	return modelsOut, payloads, nil
}

func modelsDevProviderKey(providerType string) string {
	pt := strings.ToLower(strings.TrimSpace(providerType))
	switch pt {
	case "openai", "compatible":
		return "openai"
	case "anthropic", "claude":
		return "anthropic"
	case "gemini", "vertex", "vertex-express":
		return "google"
	default:
		return ""
	}
}

func lookupModelsDevCap(reg *modelsDevRegistry, providerID, modelID string) (upstreamCap, bool) {
	modelID = strings.TrimSpace(modelID)
	if modelID == "" || reg == nil {
		return upstreamCap{}, false
	}
	if strings.TrimSpace(providerID) != "" {
		if cap, ok := reg.ByProviderModel[providerID+"|"+modelID]; ok {
			return cap, true
		}
	}
	if cap, ok := reg.ByModel[modelID]; ok {
		return cap, true
	}
	return upstreamCap{}, false
}

func (s *ModelRegistryService) applyToRedis(ctx context.Context, models map[string]modelcap.Model, payloads map[string]string, meta modelcap.Meta) error {
	pipe := s.rdb.TxPipeline()
	pipe.Del(ctx, "meta:models", "meta:models_meta")

	for name := range models {
		if strings.TrimSpace(name) == "" {
			continue
		}
		payload := payloads[name]
		if payload == "" {
			b, err := jsoncodec.Marshal(models[name].Normalized())
			if err != nil {
				return fmt.Errorf("marshal model %s: %w", name, err)
			}
			payload = string(b)
		}
		pipe.HSet(ctx, "meta:models", name, payload)
	}

	fields := map[string]string{
		"version":      strings.TrimSpace(meta.Version),
		"updated_at":   strings.TrimSpace(meta.UpdatedAt),
		"source":       strings.TrimSpace(meta.Source),
		"checksum":     strings.TrimSpace(meta.Checksum),
		"upstream_url": strings.TrimSpace(meta.UpstreamURL),
		"upstream_ref": strings.TrimSpace(meta.UpstreamRef),
	}
	for k, v := range fields {
		if v == "" {
			delete(fields, k)
		}
	}
	if fields["version"] == "" {
		fields["version"] = fmt.Sprintf("%d", time.Now().Unix())
	}
	if fields["updated_at"] == "" {
		fields["updated_at"] = fmt.Sprintf("%d", time.Now().Unix())
	}
	if fields["source"] == "" {
		fields["source"] = "models.dev"
	}
	if fields["checksum"] == "" {
		fields["checksum"] = modelcap.ChecksumFromPayloads(payloads)
	}
	if err := pipe.HSet(ctx, "meta:models_meta", fields).Err(); err != nil {
		return fmt.Errorf("write meta:models_meta: %w", err)
	}

	if _, err := pipe.Exec(ctx); err != nil {
		return fmt.Errorf("apply registry to redis: %w", err)
	}
	return nil
}

type modelRegistryFile struct {
	Meta   modelcap.Meta             `json:"meta"`
	Models map[string]modelcap.Model `json:"models"`
}

func readModelRegistryFile(path string) (*modelRegistryFile, error) {
	b, err := os.ReadFile(path)
	if err != nil {
		return nil, err
	}
	var out modelRegistryFile
	if err := jsoncodec.Unmarshal(b, &out); err != nil {
		return nil, err
	}
	if out.Models == nil {
		out.Models = make(map[string]modelcap.Model)
	}
	return &out, nil
}

func (s *ModelRegistryService) persistCache(models map[string]modelcap.Model, meta modelcap.Meta) error {
	if err := os.MkdirAll(s.cfg.CacheDir, 0o755); err != nil {
		return err
	}
	currentPath := filepath.Join(s.cfg.CacheDir, "current.json")
	prevPath := filepath.Join(s.cfg.CacheDir, "prev.json")
	tmpPath := filepath.Join(s.cfg.CacheDir, "current.json.tmp")

	if _, err := os.Stat(currentPath); err == nil {
		_ = os.Remove(prevPath)
		_ = os.Rename(currentPath, prevPath)
	}

	out := modelRegistryFile{
		Meta:   meta,
		Models: models,
	}
	b, err := json.MarshalIndent(out, "", "  ")
	if err != nil {
		return err
	}
	if err := os.WriteFile(tmpPath, b, 0o644); err != nil {
		return err
	}
	if err := os.Rename(tmpPath, currentPath); err != nil {
		return err
	}
	return nil
}