package weed_server

import (
	"encoding/json"
	"net/http"
	"time"

	"github.com/seaweedfs/seaweedfs/weed/storage/blockvol"
)

// ShipperDebugInfo is the real-time shipper state for one replica.
type ShipperDebugInfo struct {
	DataAddr   string `json:"data_addr"`
	State      string `json:"state"`
	FlushedLSN uint64 `json:"flushed_lsn"`
}

// BlockVolumeDebugInfo is the real-time block volume state.
type BlockVolumeDebugInfo struct {
	Path      string             `json:"path"`
	Role      string             `json:"role"`
	Epoch     uint64             `json:"epoch"`
	HeadLSN   uint64             `json:"head_lsn"`
	Degraded  bool               `json:"degraded"`
	Shippers  []ShipperDebugInfo `json:"shippers,omitempty"`
	Timestamp string             `json:"timestamp"`
}

// debugBlockShipperHandler returns real-time shipper state for all block volumes.
// Unlike the master's replica_degraded (heartbeat-lagged), this reads directly
// from the shipper's atomic state field — no heartbeat delay.
//
// GET /debug/block/shipper
func (vs *VolumeServer) debugBlockShipperHandler(w http.ResponseWriter, r *http.Request) {
	if vs.blockService == nil {
		w.Header().Set("Content-Type", "application/json")
		json.NewEncoder(w).Encode([]BlockVolumeDebugInfo{})
		return
	}

	store := vs.blockService.Store()
	if store == nil {
		w.Header().Set("Content-Type", "application/json")
		json.NewEncoder(w).Encode([]BlockVolumeDebugInfo{})
		return
	}

	var infos []BlockVolumeDebugInfo
	store.IterateBlockVolumes(func(path string, vol *blockvol.BlockVol) {
		status := vol.Status()
		info := BlockVolumeDebugInfo{
			Path:      path,
			Role:      status.Role.String(),
			Epoch:     status.Epoch,
			HeadLSN:   status.WALHeadLSN,
			Degraded:  status.ReplicaDegraded,
			Timestamp: time.Now().UTC().Format(time.RFC3339Nano),
		}

		// Get per-shipper state from ShipperGroup if available.
		sg := vol.GetShipperGroup()
		if sg != nil {
			for _, ss := range sg.ShipperStates() {
				info.Shippers = append(info.Shippers, ShipperDebugInfo{
					DataAddr:   ss.DataAddr,
					State:      ss.State,
					FlushedLSN: ss.FlushedLSN,
				})
			}
		}

		infos = append(infos, info)
	})

	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(infos)
}