package coredeno

import (
	"context"
	"fmt"

	pb "forge.lthn.ai/core/go/pkg/coredeno/proto"
	"forge.lthn.ai/core/go/pkg/io"
	"forge.lthn.ai/core/go/pkg/manifest"
	"forge.lthn.ai/core/go/pkg/store"
)

// Server implements the CoreService gRPC interface with permission gating.
// Every I/O request is checked against the calling module's declared permissions.
type Server struct {
	pb.UnimplementedCoreServiceServer
	medium    io.Medium
	store     *store.Store
	manifests map[string]*manifest.Manifest
}

// NewServer creates a CoreService server backed by the given Medium and Store.
func NewServer(medium io.Medium, st *store.Store) *Server {
	return &Server{
		medium:    medium,
		store:     st,
		manifests: make(map[string]*manifest.Manifest),
	}
}

// RegisterModule adds a module's manifest to the permission registry.
func (s *Server) RegisterModule(m *manifest.Manifest) {
	s.manifests[m.Code] = m
}

// getManifest looks up a module and returns an error if unknown.
func (s *Server) getManifest(code string) (*manifest.Manifest, error) {
	m, ok := s.manifests[code]
	if !ok {
		return nil, fmt.Errorf("unknown module: %s", code)
	}
	return m, nil
}

// FileRead implements CoreService.FileRead with permission gating.
func (s *Server) FileRead(_ context.Context, req *pb.FileReadRequest) (*pb.FileReadResponse, error) {
	m, err := s.getManifest(req.ModuleCode)
	if err != nil {
		return nil, err
	}
	if !CheckPath(req.Path, m.Permissions.Read) {
		return nil, fmt.Errorf("permission denied: %s cannot read %s", req.ModuleCode, req.Path)
	}
	content, err := s.medium.Read(req.Path)
	if err != nil {
		return nil, err
	}
	return &pb.FileReadResponse{Content: content}, nil
}

// FileWrite implements CoreService.FileWrite with permission gating.
func (s *Server) FileWrite(_ context.Context, req *pb.FileWriteRequest) (*pb.FileWriteResponse, error) {
	m, err := s.getManifest(req.ModuleCode)
	if err != nil {
		return nil, err
	}
	if !CheckPath(req.Path, m.Permissions.Write) {
		return nil, fmt.Errorf("permission denied: %s cannot write %s", req.ModuleCode, req.Path)
	}
	if err := s.medium.Write(req.Path, req.Content); err != nil {
		return nil, err
	}
	return &pb.FileWriteResponse{Ok: true}, nil
}

// FileList implements CoreService.FileList with permission gating.
func (s *Server) FileList(_ context.Context, req *pb.FileListRequest) (*pb.FileListResponse, error) {
	m, err := s.getManifest(req.ModuleCode)
	if err != nil {
		return nil, err
	}
	if !CheckPath(req.Path, m.Permissions.Read) {
		return nil, fmt.Errorf("permission denied: %s cannot list %s", req.ModuleCode, req.Path)
	}
	entries, err := s.medium.List(req.Path)
	if err != nil {
		return nil, err
	}
	var pbEntries []*pb.FileEntry
	for _, e := range entries {
		info, _ := e.Info()
		pbEntries = append(pbEntries, &pb.FileEntry{
			Name:  e.Name(),
			IsDir: e.IsDir(),
			Size:  info.Size(),
		})
	}
	return &pb.FileListResponse{Entries: pbEntries}, nil
}

// FileDelete implements CoreService.FileDelete with permission gating.
func (s *Server) FileDelete(_ context.Context, req *pb.FileDeleteRequest) (*pb.FileDeleteResponse, error) {
	m, err := s.getManifest(req.ModuleCode)
	if err != nil {
		return nil, err
	}
	if !CheckPath(req.Path, m.Permissions.Write) {
		return nil, fmt.Errorf("permission denied: %s cannot delete %s", req.ModuleCode, req.Path)
	}
	if err := s.medium.Delete(req.Path); err != nil {
		return nil, err
	}
	return &pb.FileDeleteResponse{Ok: true}, nil
}

// StoreGet implements CoreService.StoreGet.
func (s *Server) StoreGet(_ context.Context, req *pb.StoreGetRequest) (*pb.StoreGetResponse, error) {
	val, err := s.store.Get(req.Group, req.Key)
	if err != nil {
		return &pb.StoreGetResponse{Found: false}, nil
	}
	return &pb.StoreGetResponse{Value: val, Found: true}, nil
}

// StoreSet implements CoreService.StoreSet.
func (s *Server) StoreSet(_ context.Context, req *pb.StoreSetRequest) (*pb.StoreSetResponse, error) {
	if err := s.store.Set(req.Group, req.Key, req.Value); err != nil {
		return nil, err
	}
	return &pb.StoreSetResponse{Ok: true}, nil
}