// Copyright (C) MongoDB, Inc. 2017-present.
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may
// not use this file except in compliance with the License. You may obtain
// a copy of the License at http://www.apache.org/licenses/LICENSE-2.0

package command

import (
	"context"

	"github.com/mongodb/mongo-go-driver/bson"
	"github.com/mongodb/mongo-go-driver/x/bsonx"
	"github.com/mongodb/mongo-go-driver/x/mongo/driver/session"
	"github.com/mongodb/mongo-go-driver/x/network/description"
	"github.com/mongodb/mongo-go-driver/x/network/result"
	"github.com/mongodb/mongo-go-driver/x/network/wiremessage"
)

// KillCursors represents the killCursors command.
//
// The killCursors command kills a set of cursors.
type KillCursors struct {
	Clock *session.ClusterClock
	NS    Namespace
	IDs   []int64

	result result.KillCursors
	err    error
}

// Encode will encode this command into a wire message for the given server description.
func (kc *KillCursors) Encode(desc description.SelectedServer) (wiremessage.WireMessage, error) {
	encoded, err := kc.encode(desc)
	if err != nil {
		return nil, err
	}
	return encoded.Encode(desc)
}

func (kc *KillCursors) encode(desc description.SelectedServer) (*Read, error) {
	idVals := make([]bsonx.Val, 0, len(kc.IDs))
	for _, id := range kc.IDs {
		idVals = append(idVals, bsonx.Int64(id))
	}
	cmd := bsonx.Doc{
		{"killCursors", bsonx.String(kc.NS.Collection)},
		{"cursors", bsonx.Array(idVals)},
	}

	return &Read{
		Clock:   kc.Clock,
		DB:      kc.NS.DB,
		Command: cmd,
	}, nil
}

// Decode will decode the wire message using the provided server description. Errors during decoding
// are deferred until either the Result or Err methods are called.
func (kc *KillCursors) Decode(desc description.SelectedServer, wm wiremessage.WireMessage) *KillCursors {
	rdr, err := (&Read{}).Decode(desc, wm).Result()
	if err != nil {
		kc.err = err
		return kc
	}
	return kc.decode(desc, rdr)
}

func (kc *KillCursors) decode(desc description.SelectedServer, rdr bson.Raw) *KillCursors {
	err := bson.Unmarshal(rdr, &kc.result)
	if err != nil {
		kc.err = err
		return kc
	}
	return kc
}

// Result returns the result of a decoded wire message and server description.
func (kc *KillCursors) Result() (result.KillCursors, error) {
	if kc.err != nil {
		return result.KillCursors{}, kc.err
	}

	return kc.result, nil
}

// Err returns the error set on this command.
func (kc *KillCursors) Err() error { return kc.err }

// RoundTrip handles the execution of this command using the provided wiremessage.ReadWriter.
func (kc *KillCursors) RoundTrip(ctx context.Context, desc description.SelectedServer, rw wiremessage.ReadWriter) (result.KillCursors, error) {
	cmd, err := kc.encode(desc)
	if err != nil {
		return result.KillCursors{}, err
	}

	rdr, err := cmd.RoundTrip(ctx, desc, rw)
	if err != nil {
		return result.KillCursors{}, err
	}

	return kc.decode(desc, rdr).Result()
}