package metadata

import (
	"context"
	"crypto/sha256"
	"encoding/hex"
	"log/slog"
	"sort"
	"strings"
	"sync"
	"time"

	"github.com/Silo-Server/silo-server/internal/cache"
	"github.com/Silo-Server/silo-server/internal/catalog"

	pluginv1 "github.com/Silo-Server/silo-plugin-sdk/pkg/pluginproto/silo/plugin/v1"
	"golang.org/x/sync/singleflight"
	"google.golang.org/grpc/codes"
	"google.golang.org/grpc/status"
)

const (
	resolvedURLCacheSafetyMargin = 5 * time.Minute
	maxResolvedURLCacheTTL       = 24 * time.Hour
)

// PluginImageResolverSource provides image URL resolution for a single plugin.
type PluginImageResolverSource interface {
	ResolveImageURL(ctx context.Context, path string, variant string) (string, error)
	ResolveImageURLs(ctx context.Context, paths []string, variant string) (map[string]string, error)
}

type expiringPluginImageResolverSource interface {
	ResolveImageURLWithExpiry(ctx context.Context, path string, variant string) (catalog.ResolvedImageURL, error)
	ResolveImageURLsWithExpiry(ctx context.Context, paths []string, variant string) (map[string]catalog.ResolvedImageURL, error)
}

type PluginImageResolverSourceKind string

const (
	PluginImageResolverSourceExplicit PluginImageResolverSourceKind = "explicit"
	PluginImageResolverSourceLegacy   PluginImageResolverSourceKind = "legacy"
)

type PluginImageResolverSourceRegistration struct {
	Scheme         string
	Source         PluginImageResolverSource
	Kind           PluginImageResolverSourceKind
	Priority       int
	InstallationID int
	CapabilityID   string
}

type pluginImageResolverSourceEntry struct {
	source         PluginImageResolverSource
	kind           PluginImageResolverSourceKind
	priority       int
	installationID int
	capabilityID   string
}

// PluginImageResolver resolves plugin-prefixed image paths (e.g., "metadb://images/abc/original.jpg")
// by parsing the prefix, routing to the correct plugin, and returning resolved URLs.
// It implements catalog.ImageResolver and the catalog expiry-aware resolver extension.
type PluginImageResolver struct {
	mu           sync.RWMutex
	sources      map[string][]pluginImageResolverSourceEntry
	s3Presigner  s3ImagePresigner
	s3PresignTTL time.Duration
	urlCache     *cache.TTLCache[catalog.ResolvedImageURL]
	group        singleflight.Group
}

// NewPluginImageResolver creates a new resolver with no registered sources.
func NewPluginImageResolver() *PluginImageResolver {
	return &PluginImageResolver{
		sources:      make(map[string][]pluginImageResolverSourceEntry),
		s3PresignTTL: 15 * time.Minute,
		urlCache:     cache.NewTTLCache[catalog.ResolvedImageURL](),
	}
}

type s3ImagePresigner interface {
	PresignGetURL(ctx context.Context, bucket, key string, expiry time.Duration) (string, error)
	Bucket() string
}

// RegisterSource registers a plugin provider as a source for resolving images
// with the given plugin ID prefix.
func (r *PluginImageResolver) RegisterSource(pluginID string, source PluginImageResolverSource) {
	if source == nil || !ValidImageResolverScheme(pluginID) {
		return
	}
	r.mu.Lock()
	defer r.mu.Unlock()
	r.sources[pluginID] = append(r.sources[pluginID], pluginImageResolverSourceEntry{
		source: source,
		kind:   PluginImageResolverSourceLegacy,
	})
	sortImageResolverSources(r.sources[pluginID])
	r.urlCache.InvalidatePrefix("")
}

func (r *PluginImageResolver) ReplaceSources(registrations []PluginImageResolverSourceRegistration) {
	sources := make(map[string][]pluginImageResolverSourceEntry)
	for _, registration := range registrations {
		scheme := strings.TrimSpace(registration.Scheme)
		if registration.Source == nil || !ValidImageResolverScheme(scheme) {
			continue
		}
		kind := registration.Kind
		if kind == "" {
			kind = PluginImageResolverSourceLegacy
		}
		sources[scheme] = append(sources[scheme], pluginImageResolverSourceEntry{
			source:         registration.Source,
			kind:           kind,
			priority:       registration.Priority,
			installationID: registration.InstallationID,
			capabilityID:   registration.CapabilityID,
		})
	}
	for scheme := range sources {
		sortImageResolverSources(sources[scheme])
	}

	r.mu.Lock()
	r.sources = sources
	r.mu.Unlock()
	r.urlCache.InvalidatePrefix("")
}

func ValidImageResolverScheme(scheme string) bool {
	return scheme != "" &&
		scheme == strings.TrimSpace(scheme) &&
		scheme == strings.ToLower(scheme) &&
		!strings.Contains(scheme, "://")
}

func (r *PluginImageResolver) SetS3Presigner(presigner s3ImagePresigner, ttl time.Duration) {
	r.mu.Lock()
	defer r.mu.Unlock()
	r.s3Presigner = presigner
	if ttl > 0 {
		r.s3PresignTTL = ttl
	}
}

// Close stops the resolver cache sweeper.
func (r *PluginImageResolver) Close() {
	if r.urlCache != nil {
		r.urlCache.Close()
	}
}

// ResolveImageURL resolves a single plugin-prefixed image path.
func (r *PluginImageResolver) ResolveImageURL(ctx context.Context, path string, variant string) string {
	return r.ResolveImageURLWithExpiry(ctx, path, variant).URL
}

// ResolveImageURLWithExpiry resolves a single image path and returns validity metadata when known.
func (r *PluginImageResolver) ResolveImageURLWithExpiry(ctx context.Context, path string, variant string) catalog.ResolvedImageURL {
	if path == "" {
		return catalog.ResolvedImageURL{}
	}
	resolved := r.ResolveImageURLsWithExpiry(ctx, []string{path}, variant)
	return resolved[path]
}

// ResolveImageURLs resolves multiple plugin-prefixed image paths.
func (r *PluginImageResolver) ResolveImageURLs(ctx context.Context, paths []string, variant string) map[string]string {
	resolvedWithExpiry := r.ResolveImageURLsWithExpiry(ctx, paths, variant)
	resolved := make(map[string]string, len(resolvedWithExpiry))
	for path, value := range resolvedWithExpiry {
		resolved[path] = value.URL
	}
	return resolved
}

// ResolveImageURLsWithExpiry resolves multiple image paths, caches only URLs
// with known expiry, and coalesces concurrent identical batch misses.
func (r *PluginImageResolver) ResolveImageURLsWithExpiry(ctx context.Context, paths []string, variant string) map[string]catalog.ResolvedImageURL {
	if len(paths) == 0 {
		return map[string]catalog.ResolvedImageURL{}
	}

	result := make(map[string]catalog.ResolvedImageURL, len(paths))
	grouped := make(map[string]map[string]resolveEntry)
	for _, path := range paths {
		if path == "" {
			continue
		}
		if value, ok := r.urlCache.Get(resolvedImageCacheKey(variant, path)); ok {
			result[path] = value
			continue
		}
		pluginID, barePath := parsePluginPrefix(path)
		if pluginID == "" {
			barePath = path
		}
		if grouped[pluginID] == nil {
			grouped[pluginID] = make(map[string]resolveEntry)
		}
		grouped[pluginID][path] = resolveEntry{
			barePath:     barePath,
			originalPath: path,
		}
	}
	if len(grouped) == 0 {
		return result
	}

	r.mu.RLock()
	presigner := r.s3Presigner
	s3TTL := r.s3PresignTTL
	sourcesSnapshot := make(map[string][]pluginImageResolverSourceEntry, len(grouped))
	for pluginID := range grouped {
		if pluginID == "" {
			continue
		}
		if sources, ok := r.sources[pluginID]; ok {
			sourcesSnapshot[pluginID] = append([]pluginImageResolverSourceEntry(nil), sources...)
		}
	}
	r.mu.RUnlock()

	for pluginID, groupedEntries := range grouped {
		entries := sortedResolveEntries(groupedEntries)
		flightKey := resolvedImageBatchFlightKey(pluginID, variant, entries)
		value, err, _ := r.group.Do(flightKey, func() (any, error) {
			if pluginID == "" {
				return r.resolveS3Batch(ctx, presigner, s3TTL, entries), nil
			}
			sources := sourcesSnapshot[pluginID]
			if len(sources) == 0 {
				slog.WarnContext(ctx, "no image resolver registered for scheme", "component", "metadata", "scheme", pluginID)
				return map[string]catalog.ResolvedImageURL{}, nil
			}
			return r.resolvePluginBatchWithFallback(ctx, pluginID, sources, entries, variant), nil
		})
		if err != nil {
			slog.ErrorContext(ctx, "image batch resolution failed", "component", "metadata", "plugin_id", pluginID, "error", err)
			continue
		}

		resolvedBatch, ok := value.(map[string]catalog.ResolvedImageURL)
		if !ok {
			continue
		}
		now := time.Now()
		for path, resolvedURL := range resolvedBatch {
			result[path] = resolvedURL
			if ttl := cacheTTLForResolvedURL(resolvedURL, now); ttl > 0 {
				r.urlCache.Set(resolvedImageCacheKey(variant, path), resolvedURL, ttl)
			}
		}
	}

	return result
}

func (r *PluginImageResolver) resolvePluginBatchWithFallback(
	ctx context.Context,
	pluginID string,
	sources []pluginImageResolverSourceEntry,
	entries []resolveEntry,
	variant string,
) map[string]catalog.ResolvedImageURL {
	resolved := make(map[string]catalog.ResolvedImageURL, len(entries))
	remaining := append([]resolveEntry(nil), entries...)

	for _, source := range sources {
		if len(remaining) == 0 {
			break
		}
		resolvedBatch, err := r.resolvePluginBatch(ctx, source.source, remaining, variant)
		if err != nil {
			if status.Code(err) == codes.Unimplemented {
				slog.DebugContext(ctx, "plugin image resolver source does not implement image resolution", "component", "metadata",
					"scheme", pluginID,
					"source_kind", source.kind,
					"installation_id", source.installationID,
					"capability_id", source.capabilityID)
				continue
			}
			slog.ErrorContext(ctx, "plugin batch image resolution failed", "component", "metadata",
				"scheme", pluginID,
				"source_kind", source.kind,
				"installation_id", source.installationID,
				"capability_id", source.capabilityID,
				"error", err)
			continue
		}

		nextRemaining := remaining[:0]
		for _, entry := range remaining {
			if value, ok := resolvedBatch[entry.originalPath]; ok && value.URL != "" {
				resolved[entry.originalPath] = value
				continue
			}
			nextRemaining = append(nextRemaining, entry)
		}
		remaining = nextRemaining
	}

	return resolved
}

func (r *PluginImageResolver) resolveS3Batch(
	ctx context.Context,
	presigner s3ImagePresigner,
	ttl time.Duration,
	entries []resolveEntry,
) map[string]catalog.ResolvedImageURL {
	resolved := make(map[string]catalog.ResolvedImageURL, len(entries))
	if presigner == nil {
		return resolved
	}
	expiresAt := time.Now().Add(ttl)
	for _, entry := range entries {
		url, err := presigner.PresignGetURL(ctx, presigner.Bucket(), entry.originalPath, ttl)
		if err != nil {
			slog.ErrorContext(ctx, "s3 image resolution failed", "component", "metadata", "path", entry.originalPath, "error", err)
			continue
		}
		expiry := expiresAt
		resolved[entry.originalPath] = catalog.ResolvedImageURL{URL: url, ExpiresAt: &expiry}
	}
	return resolved
}

func (r *PluginImageResolver) resolvePluginBatch(
	ctx context.Context,
	source PluginImageResolverSource,
	entries []resolveEntry,
	variant string,
) (map[string]catalog.ResolvedImageURL, error) {
	barePaths := make([]string, len(entries))
	for i, entry := range entries {
		barePaths[i] = entry.barePath
	}

	var (
		resolvedByBare map[string]catalog.ResolvedImageURL
		err            error
	)
	if expiringSource, ok := source.(expiringPluginImageResolverSource); ok {
		resolvedByBare, err = expiringSource.ResolveImageURLsWithExpiry(ctx, barePaths, variant)
	} else {
		legacyURLs, legacyErr := source.ResolveImageURLs(ctx, barePaths, variant)
		err = legacyErr
		resolvedByBare = make(map[string]catalog.ResolvedImageURL, len(legacyURLs))
		for barePath, url := range legacyURLs {
			resolvedByBare[barePath] = catalog.ResolvedImageURL{URL: url}
		}
	}
	if err != nil {
		return nil, err
	}

	resolved := make(map[string]catalog.ResolvedImageURL, len(entries))
	for _, entry := range entries {
		if value, ok := resolvedByBare[entry.barePath]; ok {
			resolved[entry.originalPath] = value
		}
	}
	return resolved, nil
}

type resolveEntry struct {
	barePath     string
	originalPath string
}

func sortedResolveEntries(entriesByOriginal map[string]resolveEntry) []resolveEntry {
	entries := make([]resolveEntry, 0, len(entriesByOriginal))
	for _, entry := range entriesByOriginal {
		entries = append(entries, entry)
	}
	sort.Slice(entries, func(i, j int) bool {
		return entries[i].originalPath < entries[j].originalPath
	})
	return entries
}

func sortImageResolverSources(sources []pluginImageResolverSourceEntry) {
	sort.SliceStable(sources, func(i, j int) bool {
		if sourceKindRank(sources[i].kind) != sourceKindRank(sources[j].kind) {
			return sourceKindRank(sources[i].kind) < sourceKindRank(sources[j].kind)
		}
		if sources[i].priority != sources[j].priority {
			return sources[i].priority > sources[j].priority
		}
		if sources[i].installationID != sources[j].installationID {
			return sources[i].installationID < sources[j].installationID
		}
		return sources[i].capabilityID < sources[j].capabilityID
	})
}

func sourceKindRank(kind PluginImageResolverSourceKind) int {
	if kind == PluginImageResolverSourceExplicit {
		return 0
	}
	return 1
}

func resolvedImageCacheKey(variant, path string) string {
	return variant + "\x00" + path
}

func resolvedImageBatchFlightKey(pluginID, variant string, entries []resolveEntry) string {
	paths := make([]string, len(entries))
	for i, entry := range entries {
		paths[i] = entry.barePath
	}
	sort.Strings(paths)
	sum := sha256.Sum256([]byte(strings.Join(paths, "\x00")))
	return pluginID + "|" + variant + "|" + hex.EncodeToString(sum[:])
}

func cacheTTLForResolvedURL(value catalog.ResolvedImageURL, now time.Time) time.Duration {
	if value.URL == "" || value.ExpiresAt == nil {
		return 0
	}
	ttl := value.ExpiresAt.Sub(now) - resolvedURLCacheSafetyMargin
	if ttl <= 0 {
		return 0
	}
	if ttl > maxResolvedURLCacheTTL {
		return maxResolvedURLCacheTTL
	}
	return ttl
}

// PluginMetadataClient is the public interface for image resolution RPC calls.
type PluginMetadataClient interface {
	ResolveImageURL(ctx context.Context, req *pluginv1.ResolveImageURLRequest) (*pluginv1.ResolveImageURLResponse, error)
	ResolveImageURLs(ctx context.Context, req *pluginv1.ResolveImageURLsRequest) (*pluginv1.ResolveImageURLsResponse, error)
}

// PluginMetadataClientFactory creates a PluginMetadataClient for a given plugin installation.
type PluginMetadataClientFactory func(ctx context.Context, installationID int, capabilityID string) (PluginMetadataClient, error)

// pluginClientSource wraps a PluginMetadataClientFactory to satisfy PluginImageResolverSource.
type pluginClientSource struct {
	installationID int
	capabilityID   string
	clientFactory  PluginMetadataClientFactory
}

// NewPluginClientSource creates a PluginImageResolverSource from a plugin metadata client factory.
func NewPluginClientSource(installationID int, capabilityID string, factory PluginMetadataClientFactory) PluginImageResolverSource {
	return &pluginClientSource{
		installationID: installationID,
		capabilityID:   capabilityID,
		clientFactory:  factory,
	}
}

func (s *pluginClientSource) ResolveImageURL(ctx context.Context, path string, variant string) (string, error) {
	resolved, err := s.ResolveImageURLWithExpiry(ctx, path, variant)
	if err != nil {
		return "", err
	}
	return resolved.URL, nil
}

func (s *pluginClientSource) ResolveImageURLWithExpiry(ctx context.Context, path string, variant string) (catalog.ResolvedImageURL, error) {
	client, err := s.clientFactory(ctx, s.installationID, s.capabilityID)
	if err != nil {
		return catalog.ResolvedImageURL{}, err
	}

	resp, err := client.ResolveImageURL(ctx, &pluginv1.ResolveImageURLRequest{Path: path, Variant: variant})
	if err != nil {
		return catalog.ResolvedImageURL{}, err
	}
	return catalog.ResolvedImageURL{URL: resp.GetUrl()}, nil
}

func (s *pluginClientSource) ResolveImageURLs(ctx context.Context, paths []string, variant string) (map[string]string, error) {
	resolvedWithExpiry, err := s.ResolveImageURLsWithExpiry(ctx, paths, variant)
	if err != nil {
		return nil, err
	}
	resolved := make(map[string]string, len(resolvedWithExpiry))
	for path, value := range resolvedWithExpiry {
		resolved[path] = value.URL
	}
	return resolved, nil
}

func (s *pluginClientSource) ResolveImageURLsWithExpiry(ctx context.Context, paths []string, variant string) (map[string]catalog.ResolvedImageURL, error) {
	client, err := s.clientFactory(ctx, s.installationID, s.capabilityID)
	if err != nil {
		return nil, err
	}

	resp, err := client.ResolveImageURLs(ctx, &pluginv1.ResolveImageURLsRequest{Paths: paths, Variant: variant})
	if err != nil {
		return nil, err
	}

	resolved := make(map[string]catalog.ResolvedImageURL, len(paths))
	for path, url := range resp.GetUrls() {
		resolved[path] = catalog.ResolvedImageURL{URL: url}
	}
	return resolved, nil
}

// parsePluginPrefix extracts the plugin ID and bare path from a prefixed path.
// Input: "metadb://images/abc/original.jpg"
// Returns: ("metadb", "images/abc/original.jpg")
func parsePluginPrefix(path string) (pluginID, barePath string) {
	idx := strings.Index(path, "://")
	if idx <= 0 {
		return "", ""
	}
	return path[:idx], path[idx+3:]
}