package rpc

import (
	"fmt"
	"strings"

	"git.loafle.net/commons_go/rpc/protocol"
	cuc "git.loafle.net/commons_go/util/context"
)

type RPCServletHandlers struct {
	// The maximum number of pending messages in the queue.
	//
	// The number of pending requsts should exceed the expected number
	// of concurrent goroutines calling client's methods.
	// Otherwise a lot of ClientError.Overflow errors may appear.
	//
	// Default is DefaultPendingMessages.
	PendingResponses int

	codecs map[string]protocol.ServerCodec
}

func (sh *RPCServletHandlers) ServletContext(parent cuc.Context) RPCServletContext {
	return newRPCServletContext(parent)
}

func (sh *RPCServletHandlers) Init(servletCTX RPCServletContext) error {
	return nil
}

func (sh *RPCServletHandlers) ReadRequest(servletCTX RPCServletContext, codec protocol.ServerCodec, conn interface{}) (protocol.ServerRequestCodec, error) {
	return nil, fmt.Errorf("Servlet Handler: ReadRequest is not implemented")
}

func (sh *RPCServletHandlers) Invoke(servletCTX RPCServletContext, requestCodec protocol.RegistryCodec) (result interface{}, err error) {
	return nil, fmt.Errorf("Servlet Handler: Invoke is not implemented")
}

func (sh *RPCServletHandlers) WriteResponse(servletCTX RPCServletContext, conn interface{}, requestCodec protocol.ServerRequestCodec, result interface{}, err error) error {
	return fmt.Errorf("Servlet Handler: WriteResponse is not implemented")
}

func (sh *RPCServletHandlers) WriteNotification(servletCTX RPCServletContext, conn interface{}, codec protocol.ServerCodec, method string, args []interface{}) error {
	return fmt.Errorf("Servlet Handler: WriteNotification is not implemented")
}

func (sh *RPCServletHandlers) Destroy(servletCTX RPCServletContext) {
	// no op
}

// RegisterCodec adds a new codec to the server.
//
// Codecs are defined to process a given serialization scheme, e.g., JSON or
// XML. A codec is chosen based on the "Content-Type" header from the request,
// excluding the charset definition.
func (sh *RPCServletHandlers) RegisterCodec(contentType string, codec protocol.ServerCodec) {
	if nil == sh.codecs {
		sh.codecs = make(map[string]protocol.ServerCodec)
	}
	sh.codecs[strings.ToLower(contentType)] = codec
}

func (sh *RPCServletHandlers) getCodec(contentType string) (protocol.ServerCodec, error) {
	var codec protocol.ServerCodec
	if contentType == "" && len(sh.codecs) == 1 {
		// If Content-Type is not set and only one codec has been registered,
		// then default to that codec.
		for _, c := range sh.codecs {
			codec = c
		}
	} else if codec = sh.codecs[strings.ToLower(contentType)]; codec == nil {
		return nil, fmt.Errorf("Unrecognized Content-Type: %s", contentType)
	}

	return codec, nil
}

func (sh *RPCServletHandlers) GetPendingResponses() int {
	return sh.PendingResponses
}

func (sh *RPCServletHandlers) Validate() {
	if 0 >= sh.PendingResponses {
		sh.PendingResponses = DefaultPendingResponses
	}
}