package global

import (
	"context"
	"io"
	"log/slog"
	"reflect"
	"sync"

	"github.com/redis/go-redis/v9"
	"go.mongodb.org/mongo-driver/mongo"
	"gorm.io/gorm"
	platformmq "kra/pkg/mq"
	platformws "kra/pkg/websocket"
)

// FileStorage is the transport-neutral subset shared by every file storage
// implementation. Domain operations that return business models remain in
// the biz-owned FileStorage interface instead of making global depend on biz.
type FileStorage interface {
	Open(context.Context, string) (io.ReadCloser, error)
	Delete(context.Context, string) error
	DeletePrefix(context.Context, string) error
}

// Scheduler owns the lifecycle of the process-wide task scheduler. Scheduling
// business operations remain behind the task domain interfaces.
type Scheduler interface {
	Start(context.Context) error
	Stop(context.Context) error
}

// Resources is an immutable snapshot from the registry's point of view.
// Replacing a resource publishes a new snapshot; it does not close the old
// resource because lifecycle ownership belongs to the composition root.
type Resources struct {
	Logger     *slog.Logger
	DB         *gorm.DB
	NamedDBs   map[string]*gorm.DB
	Redis      redis.UniversalClient
	NamedRedis map[string]redis.UniversalClient
	Mongo      *mongo.Client
	Storage    FileStorage
	MQ         platformmq.Registry
	WebSocket  platformws.Hub
	Scheduler  Scheduler
}

// ResourceRegistry provides concurrency-safe access to process-wide runtime
// resources. Prefer constructor injection for domain code; the registry is for
// framework callbacks and integration points that cannot be wired directly.
type ResourceRegistry struct {
	mu        sync.RWMutex
	resources Resources
}

func NewResourceRegistry() *ResourceRegistry {
	return &ResourceRegistry{resources: normalizeResources(Resources{})}
}

func (r *ResourceRegistry) Snapshot() Resources {
	if r == nil {
		return normalizeResources(Resources{})
	}
	r.mu.RLock()
	resources := cloneResources(r.resources)
	r.mu.RUnlock()
	return resources
}

func (r *ResourceRegistry) Replace(resources Resources) {
	if r == nil {
		return
	}
	r.mu.Lock()
	r.resources = normalizeResources(resources)
	r.mu.Unlock()
}

func normalizeResources(resources Resources) Resources {
	if resources.Logger == nil {
		resources.Logger = slog.Default()
	}
	resources.Redis = normalizeInterface(resources.Redis)
	resources.Storage = normalizeInterface(resources.Storage)
	resources.MQ = normalizeInterface(resources.MQ)
	resources.WebSocket = normalizeInterface(resources.WebSocket)
	resources.Scheduler = normalizeInterface(resources.Scheduler)
	resources.NamedDBs = cloneDBMap(resources.NamedDBs)
	resources.NamedRedis = cloneRedisMap(resources.NamedRedis)
	return resources
}

func cloneResources(resources Resources) Resources {
	resources.NamedDBs = cloneDBMap(resources.NamedDBs)
	resources.NamedRedis = cloneRedisMap(resources.NamedRedis)
	return resources
}

func cloneDBMap(source map[string]*gorm.DB) map[string]*gorm.DB {
	if len(source) == 0 {
		return nil
	}
	copyOf := make(map[string]*gorm.DB, len(source))
	for name, db := range source {
		if name != "" && db != nil {
			copyOf[name] = db
		}
	}
	if len(copyOf) == 0 {
		return nil
	}
	return copyOf
}

func cloneRedisMap(source map[string]redis.UniversalClient) map[string]redis.UniversalClient {
	if len(source) == 0 {
		return nil
	}
	copyOf := make(map[string]redis.UniversalClient, len(source))
	for name, client := range source {
		if name == "" {
			continue
		}
		client = normalizeInterface(client)
		if client != nil {
			copyOf[name] = client
		}
	}
	if len(copyOf) == 0 {
		return nil
	}
	return copyOf
}

func normalizeInterface[T any](value T) T {
	reflected := reflect.ValueOf(value)
	if reflected.IsValid() {
		switch reflected.Kind() {
		case reflect.Chan, reflect.Func, reflect.Interface, reflect.Map, reflect.Pointer, reflect.Slice:
			if !reflected.IsNil() {
				return value
			}
		default:
			return value
		}
	}
	var zero T
	return zero
}

var defaultResources = NewResourceRegistry()

// Install publishes resources assembled by the composition root and returns
// the process-wide registry for lifecycle wiring.
func Install(resources Resources) *ResourceRegistry {
	defaultResources.Replace(resources)
	return defaultResources
}

func DefaultRegistry() *ResourceRegistry { return defaultResources }

func ResourceSnapshot() Resources { return defaultResources.Snapshot() }