package rpc

import (
	"github.com/mitchellh/packer/packer"
	"log"
	"net/rpc"
)

// An implementation of packer.Builder where the builder is actually executed
// over an RPC connection.
type builder struct {
	client *rpc.Client
	mux    *MuxConn
}

// BuilderServer wraps a packer.Builder implementation and makes it exportable
// as part of a Golang RPC server.
type BuilderServer struct {
	builder packer.Builder
	mux     *MuxConn
}

type BuilderPrepareArgs struct {
	Configs []interface{}
}

type BuilderPrepareResponse struct {
	Warnings []string
	Error    error
}

func (b *builder) Prepare(config ...interface{}) ([]string, error) {
	var resp BuilderPrepareResponse
	cerr := b.client.Call("Builder.Prepare", &BuilderPrepareArgs{config}, &resp)
	if cerr != nil {
		return nil, cerr
	}

	return resp.Warnings, resp.Error
}

func (b *builder) Run(ui packer.Ui, hook packer.Hook, cache packer.Cache) (packer.Artifact, error) {
	nextId := b.mux.NextId()
	server := newServerWithMux(b.mux, nextId)
	server.RegisterCache(cache)
	server.RegisterHook(hook)
	server.RegisterUi(ui)
	go server.Serve()

	var responseId uint32
	if err := b.client.Call("Builder.Run", nextId, &responseId); err != nil {
		return nil, err
	}

	if responseId == 0 {
		return nil, nil
	}

	client, err := newClientWithMux(b.mux, responseId)
	if err != nil {
		return nil, err
	}

	return client.Artifact(), nil
}

func (b *builder) Cancel() {
	if err := b.client.Call("Builder.Cancel", new(interface{}), new(interface{})); err != nil {
		log.Printf("Error cancelling builder: %s", err)
	}
}

func (b *BuilderServer) Prepare(args *BuilderPrepareArgs, reply *BuilderPrepareResponse) error {
	warnings, err := b.builder.Prepare(args.Configs...)
	if err != nil {
		err = NewBasicError(err)
	}

	*reply = BuilderPrepareResponse{
		Warnings: warnings,
		Error:    err,
	}
	return nil
}

func (b *BuilderServer) Run(streamId uint32, reply *uint32) error {
	client, err := newClientWithMux(b.mux, streamId)
	if err != nil {
		return NewBasicError(err)
	}
	defer client.Close()

	artifact, err := b.builder.Run(client.Ui(), client.Hook(), client.Cache())
	if err != nil {
		return NewBasicError(err)
	}

	*reply = 0
	if artifact != nil {
		streamId = b.mux.NextId()
		server := newServerWithMux(b.mux, streamId)
		server.RegisterArtifact(artifact)
		go server.Serve()
		*reply = streamId
	}

	return nil
}

func (b *BuilderServer) Cancel(args *interface{}, reply *interface{}) error {
	b.builder.Cancel()
	return nil
}
