package services

import (
	"time"

	"git.saqut.com/saqut/mwse/internal/datastore"
	"git.saqut.com/saqut/mwse/internal/protocol"
	"git.saqut.com/saqut/mwse/internal/ws"
)

// registerDatastore wires the #45 shared data layer: active sync (collections with
// CRUD broadcast), passive sync (a fast merge pool), and temp/permanent
// datastores. The returned store is handed back so a janitor can reclaim expired
// temp stores/pools.
//
// Wire surface (additive):
//
//	Active sync / collection / datastore:
//	  data/open   {id?, kind?, primary?, expires?} -> {status, id, primary, kind, records}
//	    (kind = "temp" | "permanent". The payload field is "kind", NOT "type":
//	     "type" is reserved by WSTS to select the handler.)
//	  data/set    {id, record}                    -> {status, key, seq}   + broadcast data/op(set)
//	  data/delete {id, key}                        -> {status, seq}        + broadcast data/op(delete)
//	  data/get    {id, key?}                        -> {status, record|records}
//
//	Passive sync (merge pool):
//	  sync/open   {id?, expires?}                  -> {status, id, items}
//	  sync/push   {id, items}                       -> {status, added}     + broadcast sync/add
//	  sync/pull   {id}                              -> {status, items}
//
// Broadcasts are server signals delivered to every *other* subscriber:
//
//	[ {id, op, record|key, seq}, "data/op" ]
//	[ {id, items}, "sync/add" ]
func registerDatastore(hub *ws.Hub) *datastore.Store {
	store := datastore.NewStore()

	// Signal a set of subscriber ids, skipping the originator (it already holds the
	// change and learns the authoritative seq from its own reply).
	broadcast := func(subs []string, except, name string, payload map[string]any) {
		for _, id := range subs {
			if id == except {
				continue
			}
			if cl, ok := hub.Client(id); ok {
				cl.Signal(name, payload)
			}
		}
	}

	// A departed client must leave no residual subscription anywhere.
	hub.OnDisconnect(func(c *ws.Client) { store.UnsubscribeAll(c.ID) })

	// ---- active sync / collection / datastore -------------------------------

	hub.Register("data/open", func(c *ws.Client, m protocol.Message) any {
		kind := datastore.Temp
		if m.Str("kind") == string(datastore.Permanent) {
			kind = datastore.Permanent
		}
		ttl := time.Duration(m.Int("expires")) * time.Second
		ds := store.Open(m.Str("id"), kind, m.Str("primary"), ttl)
		ds.Subscribe(c.ID)
		return map[string]any{
			"status":  "success",
			"id":      ds.ID,
			"primary": ds.Primary,
			"kind":    string(ds.Kind),
			"records": ds.Snapshot(),
		}
	})

	hub.Register("data/set", func(c *ws.Client, m protocol.Message) any {
		ds, ok := store.Get(m.Str("id"))
		if !ok {
			return fail("NOT_FOUND")
		}
		rec, ok := ds.Set(toMap(m.Get("record")), store.Now())
		if !ok {
			return fail("PRIMARY_KEY_REQUIRED")
		}
		broadcast(ds.Subscribers(), c.ID, "data/op", map[string]any{
			"id":     ds.ID,
			"op":     "set",
			"record": rec,
			"seq":    rec.Seq,
		})
		return map[string]any{"status": "success", "key": rec.Key, "seq": rec.Seq}
	})

	hub.Register("data/delete", func(c *ws.Client, m protocol.Message) any {
		ds, ok := store.Get(m.Str("id"))
		if !ok {
			return fail("NOT_FOUND")
		}
		key := m.Str("key")
		seq, ok := ds.Delete(key)
		if !ok {
			return fail("NO_SUCH_KEY")
		}
		broadcast(ds.Subscribers(), c.ID, "data/op", map[string]any{
			"id":  ds.ID,
			"op":  "delete",
			"key": key,
			"seq": seq,
		})
		return map[string]any{"status": "success", "seq": seq}
	})

	hub.Register("data/get", func(c *ws.Client, m protocol.Message) any {
		ds, ok := store.Get(m.Str("id"))
		if !ok {
			return fail("NOT_FOUND")
		}
		if key := m.Str("key"); key != "" {
			rec, ok := ds.Get(key)
			if !ok {
				return fail("NO_SUCH_KEY")
			}
			return map[string]any{"status": "success", "record": rec}
		}
		return map[string]any{"status": "success", "records": ds.Snapshot()}
	})

	// ---- passive sync (merge pool) ------------------------------------------

	hub.Register("sync/open", func(c *ws.Client, m protocol.Message) any {
		ttl := time.Duration(m.Int("expires")) * time.Second
		p := store.OpenPool(m.Str("id"), ttl)
		p.Subscribe(c.ID)
		return map[string]any{"status": "success", "id": p.ID, "items": p.Items()}
	})

	hub.Register("sync/push", func(c *ws.Client, m protocol.Message) any {
		items := toSlice(m.Get("items"))
		added, subs, ok := store.PushPool(m.Str("id"), items)
		if !ok {
			return fail("NOT_FOUND")
		}
		if len(added) > 0 {
			broadcast(subs, c.ID, "sync/add", map[string]any{"id": m.Str("id"), "items": added})
		}
		return map[string]any{"status": "success", "added": len(added)}
	})

	hub.Register("sync/pull", func(c *ws.Client, m protocol.Message) any {
		p, ok := store.GetPool(m.Str("id"))
		if !ok {
			return fail("NOT_FOUND")
		}
		return map[string]any{"status": "success", "items": p.Items()}
	})

	return store
}

// toSlice coerces a decoded JSON value to a slice, returning nil when it is not
// an array.
func toSlice(v any) []any {
	if s, ok := v.([]any); ok {
		return s
	}
	return nil
}