package toolhost

import (
	"bufio"
	"context"
	"encoding/json"
	"errors"
	"io"
	"sort"
	"strings"
	"sync"

	"laodingbot/internal/logger"
	"laodingbot/internal/tools"
)

type Server struct {
	registry *tools.Registry
	log      *logger.Logger

	writeMu sync.Mutex
}

func NewServer(registry *tools.Registry, log *logger.Logger) *Server {
	return &Server{registry: registry, log: log}
}

func (s *Server) Serve(ctx context.Context, reader io.Reader, writer io.Writer) error {
	dec := json.NewDecoder(bufio.NewReader(reader))
	for {
		select {
		case <-ctx.Done():
			return ctx.Err()
		default:
		}

		var req rpcRequest
		if err := dec.Decode(&req); err != nil {
			if errors.Is(err, io.EOF) {
				return nil
			}
			if s.log != nil {
				s.log.Errorf("toolhost decode request failed err=%v", err)
			}
			return err
		}

		resp := s.handleRequest(ctx, req)
		if err := s.writeResponse(writer, resp); err != nil {
			if s.log != nil {
				s.log.Errorf("toolhost write response failed err=%v", err)
			}
			return err
		}
	}
}

func (s *Server) handleRequest(ctx context.Context, req rpcRequest) rpcResponse {
	resp := rpcResponse{JSONRPC: "2.0", ID: req.ID}

	switch req.Method {
	case "ping":
		resp.Result = map[string]string{"status": "ok"}
		return resp
	case "tool.list":
		list := s.registry.List()
		sort.Slice(list, func(i, j int) bool {
			return strings.ToLower(list[i].Name()) < strings.ToLower(list[j].Name())
		})
		infos := make([]toolInfo, 0, len(list))
		for _, t := range list {
			infos = append(infos, toolInfo{Name: t.Name(), Description: t.Description()})
		}
		resp.Result = infos
		return resp
	case "tool.call":
		var p toolCallParams
		if err := json.Unmarshal(req.Params, &p); err != nil {
			resp.Error = &rpcError{Code: -32602, Message: "invalid params"}
			return resp
		}
		name := strings.TrimSpace(strings.ToLower(p.Name))
		tool, ok := s.registry.Get(name)
		if !ok {
			resp.Error = &rpcError{Code: -32004, Message: "tool not found"}
			return resp
		}
		out, err := tool.Call(ctx, p.Input)
		result := toolCallResult{Output: out}
		if err != nil {
			result.Error = err.Error()
		}
		resp.Result = result
		return resp
	default:
		resp.Error = &rpcError{Code: -32601, Message: "method not found"}
		return resp
	}
}

func (s *Server) writeResponse(writer io.Writer, resp rpcResponse) error {
	s.writeMu.Lock()
	defer s.writeMu.Unlock()
	enc := json.NewEncoder(writer)
	return enc.Encode(resp)
}