// Copyright 2018 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package cmd

import (
	"context"
	"flag"
	"fmt"
	"os"
	"strings"

	"golang.org/x/tools/internal/jsonrpc2"
	"golang.org/x/tools/internal/lsp/cache"
	"golang.org/x/tools/internal/lsp/lsprpc"
	"golang.org/x/tools/internal/lsp/protocol"
	"golang.org/x/tools/internal/tool"
)

// Serve is a struct that exposes the configurable parts of the LSP server as
// flags, in the right form for tool.Main to consume.
type Serve struct {
	Logfile string `flag:"logfile" help:"filename to log to. if value is \"auto\", then logging to a default output file is enabled"`
	Mode    string `flag:"mode" help:"no effect"`
	Port    int    `flag:"port" help:"port on which to run gopls for debugging purposes"`
	Address string `flag:"listen" help:"address on which to listen for remote connections. If prefixed by 'unix;', the subsequent address is assumed to be a unix domain socket. Otherwise, TCP is used."`
	Trace   bool   `flag:"rpc.trace" help:"print the full rpc trace in lsp inspector format"`
	Debug   string `flag:"debug" help:"serve debug information on the supplied address"`

	app *Application
}

func (s *Serve) Name() string  { return "serve" }
func (s *Serve) Usage() string { return "" }
func (s *Serve) ShortHelp() string {
	return "run a server for Go code using the Language Server Protocol"
}
func (s *Serve) DetailedHelp(f *flag.FlagSet) {
	fmt.Fprint(f.Output(), `
The server communicates using JSONRPC2 on stdin and stdout, and is intended to be run directly as
a child of an editor process.

gopls server flags are:
`)
	f.PrintDefaults()
}

// Run configures a server based on the flags, and then runs it.
// It blocks until the server shuts down.
func (s *Serve) Run(ctx context.Context, args ...string) error {
	if len(args) > 0 {
		return tool.CommandLineErrorf("server does not take arguments, got %v", args)
	}

	closeLog, err := s.app.debug.SetLogFile(s.Logfile)
	if err != nil {
		return err
	}
	defer closeLog()
	s.app.debug.ServerAddress = s.Address
	s.app.debug.DebugAddress = s.Debug
	s.app.debug.Serve(ctx)
	s.app.debug.MonitorMemory(ctx)

	var ss jsonrpc2.StreamServer
	if s.app.Remote != "" {
		network, addr := parseAddr(s.app.Remote)
		ss = lsprpc.NewForwarder(network, addr, true, s.app.debug)
	} else {
		ss = lsprpc.NewStreamServer(cache.New(s.app.options, s.app.debug.State), true, s.app.debug)
	}

	if s.Address != "" {
		network, addr := parseAddr(s.Address)
		return jsonrpc2.ListenAndServe(ctx, network, addr, ss)
	}
	if s.Port != 0 {
		addr := fmt.Sprintf(":%v", s.Port)
		return jsonrpc2.ListenAndServe(ctx, "tcp", addr, ss)
	}
	stream := jsonrpc2.NewHeaderStream(os.Stdin, os.Stdout)
	if s.Trace {
		stream = protocol.LoggingStream(stream, s.app.debug.LogWriter)
	}
	return ss.ServeStream(ctx, stream)
}

// parseAddr parses the -listen flag in to a network, and address.
func parseAddr(listen string) (network string, address string) {
	// Allow passing just -remote=auto, as a shorthand for using automatic remote
	// resolution.
	if listen == lsprpc.AutoNetwork {
		return lsprpc.AutoNetwork, ""
	}
	if parts := strings.SplitN(listen, ";", 2); len(parts) == 2 {
		return parts[0], parts[1]
	}
	return "tcp", listen
}