package internal

import (
	"context"
	"encoding/json"
	"fmt"
	"net/http"

	"github.com/envoyproxy/go-control-plane/pkg/cache/types"
	resourcev3 "github.com/envoyproxy/go-control-plane/pkg/resource/v3"
	"google.golang.org/protobuf/encoding/protojson"
	"google.golang.org/protobuf/reflect/protoreflect"

	internalapi "envoy-control-plane/internal/api"
	"envoy-control-plane/internal/storage"
)

// ---------------- Persistence Handlers ----------------

// loadSnapshotFromDB loads the full configuration from the persistent database
// into the SnapshotManager's Envoy Cache.
func (api *API) loadSnapshotFromDB(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
		return
	}
	w.Header().Set("Content-Type", "application/json")

	// Use context.Background() since this is a top-level operation
	if err := api.Manager.LoadSnapshotFromDB(context.Background()); err != nil {
		http.Error(w, fmt.Sprintf("failed to load from DB: %v", err), http.StatusInternalServerError)
		return
	}

	w.WriteHeader(http.StatusOK)
	json.NewEncoder(w).Encode(map[string]string{"status": "ok", "message": "Configuration loaded from DB and applied to cache."})
}

// flushCacheToDB saves the current configuration from the Envoy Cache (source of truth)
// to the persistent database.
func (api *API) flushCacheToDB(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
		return
	}
	w.Header().Set("Content-Type", "application/json")

	// Default to DeleteLogical (no physical deletion)
	deleteStrategy := storage.DeleteLogical // DeleteLogical is assumed to be defined elsewhere

	// Check for 'deleteMissing' query parameter. If "true" or "1", switch to DeleteActual.
	deleteMissingStr := r.URL.Query().Get("deleteMissing")
	if deleteMissingStr == "true" || deleteMissingStr == "1" {
		deleteStrategy = storage.DeleteActual // DeleteActual is assumed to be defined elsewhere
	}

	// Use context.Background() since this is a top-level operation
	// Pass the determined DeleteStrategy
	if err := api.Manager.FlushCacheToDB(context.Background(), deleteStrategy); err != nil {
		http.Error(w, fmt.Sprintf("failed to flush to DB: %v", err), http.StatusInternalServerError)
		return
	}

	w.WriteHeader(http.StatusOK)
	json.NewEncoder(w).Encode(map[string]string{"status": "ok", "message": "Configuration saved from cache to DB."})
}

// loadSnapshotFromFile loads a snapshot from a local file and applies it to the cache.
func (api *API) loadSnapshotFromFile(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
		return
	}
	w.Header().Set("Content-Type", "application/json")

	var req internalapi.SnapshotFileRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil || req.Path == "" {
		http.Error(w, "path required in request body", http.StatusBadRequest)
		return
	}

	resources, err := api.Manager.LoadSnapshotFromFile(context.Background(), req.Path)
	if err != nil {
		http.Error(w, fmt.Sprintf("failed to load snapshot from file: %v", err), http.StatusInternalServerError)
		return
	}

	// Use context.Background()
	if err := api.Manager.SetSnapshot(context.Background(), req.Path, resources); err != nil {
		http.Error(w, fmt.Sprintf("failed to set snapshot: %v", err), http.StatusInternalServerError)
		return
	}

	w.WriteHeader(http.StatusOK)
	json.NewEncoder(w).Encode(map[string]string{"status": "ok", "message": fmt.Sprintf("Snapshot loaded from %s and applied.", req.Path)})
}

// saveSnapshotToFile saves the current cache snapshot to a local file.
func (api *API) saveSnapshotToFile(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
		return
	}
	w.Header().Set("Content-Type", "application/json")

	var req internalapi.SnapshotFileRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil || req.Path == "" {
		http.Error(w, "path required in request body", http.StatusBadRequest)
		return
	}

	if err := api.Manager.SaveSnapshotToFile(req.Path); err != nil {
		http.Error(w, fmt.Sprintf("failed to save snapshot to file: %v", err), http.StatusInternalServerError)
		return
	}

	w.WriteHeader(http.StatusOK)
	json.NewEncoder(w).Encode(map[string]string{"status": "ok", "message": fmt.Sprintf("Snapshot saved to %s.", req.Path)})
}

// ---------------- Generic REST Handlers ----------------

// addResourceHandler handles adding a resource (Cluster, Listener) to the cache and persisting it.
func (api *API) addResourceHandler(w http.ResponseWriter, r *http.Request, typ resourcev3.Type, createFn func(interface{}) types.Resource) {
	if r.Method != http.MethodPost {
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
		return
	}
	w.Header().Set("Content-Type", "application/json")

	var req interface{}
	switch typ {
	case resourcev3.ClusterType:
		req = &internalapi.AddClusterRequest{}
	// case resourcev3.RouteType:
	//  req = &AddRouteRequest{}
	case resourcev3.ListenerType:
		req = &internalapi.AddListenerRequest{}
	default:
		http.Error(w, "unsupported type", http.StatusBadRequest)
		return
	}

	if err := json.NewDecoder(r.Body).Decode(req); err != nil {
		http.Error(w, "invalid request", http.StatusBadRequest)
		return
	}

	res := createFn(req)
	if err := api.Manager.AddResourceToSnapshot(res, typ); err != nil {
		http.Error(w, fmt.Sprintf("failed to add resource: %v", err), http.StatusInternalServerError)
		return
	}
	// Persist immediately using DeleteLogical (mark as disabled in DB)
	if err := api.Manager.FlushCacheToDB(context.Background(), storage.DeleteLogical); err != nil {
		http.Error(w, fmt.Sprintf("failed to persist resource to DB: %v", err), http.StatusInternalServerError)
		return
	}

	w.WriteHeader(http.StatusCreated)
	json.NewEncoder(w).Encode(map[string]string{"name": res.(interface{ GetName() string }).GetName()})
}

// disableResourceHandler handles disabling a resource (logical removal from cache/DB).
func (api *API) disableResourceHandler(w http.ResponseWriter, r *http.Request, typ resourcev3.Type) {
	if r.Method != http.MethodPost {
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
		return
	}
	w.Header().Set("Content-Type", "application/json")

	var req struct{ Name string }
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil || req.Name == "" {
		http.Error(w, "name required", http.StatusBadRequest)
		return
	}

	// Use DeleteLogical to remove from cache and mark as disabled in DB
	if err := api.Manager.RemoveResource(req.Name, typ, storage.DeleteLogical); err != nil {
		http.Error(w, fmt.Sprintf("failed to disable resource: %v", err), http.StatusInternalServerError)
		return
	}

	w.WriteHeader(http.StatusOK)
	json.NewEncoder(w).Encode(map[string]string{"status": "ok", "message": fmt.Sprintf("Resource '%s' disabled.", req.Name)})
}

// enableResourceHandler fetches a disabled resource from the DB and enables it (adds to cache).
func (api *API) enableResourceHandler(w http.ResponseWriter, r *http.Request, typ resourcev3.Type) {
	if r.Method != http.MethodPost {
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
		return
	}
	w.Header().Set("Content-Type", "application/json")

	var req internalapi.EnableResourceRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil || req.Name == "" {
		http.Error(w, "name required", http.StatusBadRequest)
		return
	}

	// Call the Manager function to pull the resource from DB, enable it, and add to the cache.
	if err := api.Manager.EnableResourceFromDB(req.Name, typ); err != nil {
		// NOTE: Exact error string check is brittle but necessary to replicate original logic's status code.
		if err.Error() == fmt.Sprintf("disabled resource %s not found in DB for type %s", req.Name, typ) {
			http.Error(w, fmt.Sprintf("disabled resource '%s' not found or already enabled: %v", req.Name, err), http.StatusNotFound)
		} else {
			http.Error(w, fmt.Sprintf("failed to enable resource '%s' from DB: %v", req.Name, err), http.StatusInternalServerError)
		}
		return
	}

	// Reload the cache again from DB to ensure consistency.
	if err := api.Manager.LoadSnapshotFromDB(context.Background()); err != nil {
		http.Error(w, fmt.Sprintf("failed to reload snapshot from DB after enabling resource: %v", err), http.StatusInternalServerError)
		return
	}

	w.WriteHeader(http.StatusOK)
	json.NewEncoder(w).Encode(map[string]string{"status": "ok", "message": fmt.Sprintf("Resource '%s' enabled and applied to cache.", req.Name)})
}

// removeResourceHandler removes a resource completely from the DB (DeleteActual).
// It requires the resource to be disabled (not in the cache) before actual deletion.
func (api *API) removeResourceHandler(w http.ResponseWriter, r *http.Request, typ resourcev3.Type) {
	if r.Method != http.MethodPost {
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
		return
	}
	w.Header().Set("Content-Type", "application/json")

	var req internalapi.RemoveResourceRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil || req.Name == "" {
		http.Error(w, "name required", http.StatusBadRequest)
		return
	}

	// Use DeleteActual strategy for permanent removal from the DB.
	if err := api.Manager.RemoveResource(req.Name, typ, storage.DeleteActual); err != nil {
		// NOTE: Exact error string check is brittle but necessary to replicate original logic's status code.
		if err.Error() == fmt.Sprintf("resource %s for type %s is enabled and must be disabled before removal", req.Name, typ) {
			http.Error(w, fmt.Sprintf("resource '%s' must be disabled first before permanent removal: %v", req.Name, err), http.StatusBadRequest)
		} else {
			http.Error(w, fmt.Sprintf("failed to permanently remove resource: %v", err), http.StatusInternalServerError)
		}
		return
	}

	w.WriteHeader(http.StatusOK)
	json.NewEncoder(w).Encode(map[string]string{"status": "ok", "message": fmt.Sprintf("Resource '%s' permanently removed.", req.Name)})
}

// ---------------- Query / List Handlers ----------------

// listResourceHandler returns a list of enabled and disabled resources of a given type.
func (api *API) listResourceHandler(w http.ResponseWriter, r *http.Request, typ resourcev3.Type) {
	if r.Method != http.MethodGet {
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
		return
	}
	w.Header().Set("Content-Type", "application/json")

	enabledResources, disabledResources, err := api.Manager.ListResources(typ)
	if err != nil {
		http.Error(w, fmt.Sprintf("failed to list resources: %v", err), http.StatusInternalServerError)
		return
	}

	// Create the final response object structure
	response := struct {
		Enabled  []types.Resource `json:"enabled"`
		Disabled []types.Resource `json:"disabled"`
	}{
		Enabled:  enabledResources,
		Disabled: disabledResources,
	}

	w.WriteHeader(http.StatusOK)
	if err := json.NewEncoder(w).Encode(response); err != nil {
		http.Error(w, "failed to encode response", http.StatusInternalServerError)
	}
}

// getResourceHandler returns a single resource by name, allowing for different output formats.
func (api *API) getResourceHandler(w http.ResponseWriter, r *http.Request, typ resourcev3.Type) {
	if r.Method != http.MethodGet {
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
		return
	}

	name := r.URL.Query().Get("name")
	if name == "" {
		http.Error(w, "name query parameter required", http.StatusBadRequest)
		return
	}

	format := r.URL.Query().Get("format")
	if format == "" {
		format = "json" // default format
	}

	res, err := api.Manager.GetResourceFromCache(name, typ)
	if err != nil {
		http.Error(w, fmt.Sprintf("resource not found: %v", err), http.StatusNotFound)
		return
	}

	pb, ok := res.(interface{ ProtoReflect() protoreflect.Message })
	if !ok {
		http.Error(w, "resource is not a protobuf message", http.StatusInternalServerError)
		return
	}

	var output []byte
	switch format {
	case "yaml":
		// ConvertProtoToYAML is assumed to be defined elsewhere
		yamlStr, err := ConvertProtoToYAML(pb)
		if err != nil {
			http.Error(w, fmt.Sprintf("failed to convert resource to YAML: %v", err), http.StatusInternalServerError)
			return
		}
		w.Header().Set("Content-Type", "application/x-yaml")
		output = []byte(yamlStr)
	default: // json
		data, err := protojson.Marshal(pb)
		if err != nil {
			http.Error(w, fmt.Sprintf("failed to marshal protobuf to JSON: %v", err), http.StatusInternalServerError)
			return
		}
		w.Header().Set("Content-Type", "application/json")
		output = data
	}

	w.WriteHeader(http.StatusOK)
	w.Write(output)
}

// ---------------- Consistency Handler ----------------

// isConsistentHandler checks whether the current in-memory cache is consistent with the database.
func (api *API) isConsistentHandler(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodGet {
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
		return
	}
	w.Header().Set("Content-Type", "application/json")

	// ConsistencyReport is assumed to be defined elsewhere
	consistent, err := api.Manager.CheckCacheDBConsistency(context.TODO())
	if err != nil {
		http.Error(w, fmt.Sprintf("failed to check consistency: %v", err), http.StatusInternalServerError)
		return
	}

	response := struct {
		Consistent *internalapi.ConsistencyReport `json:"consistent"` // ConsistencyReport is assumed to be defined elsewhere
	}{
		Consistent: consistent,
	}

	w.WriteHeader(http.StatusOK)
	if err := json.NewEncoder(w).Encode(response); err != nil {
		http.Error(w, "failed to encode response", http.StatusInternalServerError)
	}
}