package rpc

import (
	"bufio"
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"net"
	"net/http"
	"os"
	"time"
)

const Version = 1

type Request struct {
	Version int             `json:"version"`
	Method  string          `json:"method"`
	Params  json.RawMessage `json:"params,omitempty"`
}

type Response struct {
	OK     bool            `json:"ok"`
	Result json.RawMessage `json:"result,omitempty"`
	Error  *ErrorResponse  `json:"error,omitempty"`
}

type ErrorResponse struct {
	Code    string `json:"code"`
	Message string `json:"message"`
}

func NewResult(v any) (Response, error) {
	data, err := json.Marshal(v)
	if err != nil {
		return Response{}, err
	}
	return Response{OK: true, Result: data}, nil
}

func NewError(code, message string) Response {
	return Response{OK: false, Error: &ErrorResponse{Code: code, Message: message}}
}

func DecodeParams[T any](req Request) (T, error) {
	var zero T
	if len(req.Params) == 0 {
		return zero, nil
	}
	var out T
	if err := json.Unmarshal(req.Params, &out); err != nil {
		return zero, err
	}
	return out, nil
}

func Call[T any](ctx context.Context, socketPath, method string, params any) (T, error) {
	var zero T
	conn, err := net.DialTimeout("unix", socketPath, 2*time.Second)
	if err != nil {
		return zero, err
	}
	defer conn.Close()

	if deadline, ok := ctx.Deadline(); ok {
		_ = conn.SetDeadline(deadline)
	}

	request := Request{Version: Version, Method: method}
	if params != nil {
		raw, err := json.Marshal(params)
		if err != nil {
			return zero, err
		}
		request.Params = raw
	}

	if err := json.NewEncoder(conn).Encode(request); err != nil {
		return zero, err
	}

	var response Response
	if err := json.NewDecoder(bufio.NewReader(conn)).Decode(&response); err != nil {
		return zero, err
	}
	if !response.OK {
		if response.Error == nil {
			return zero, errors.New("rpc error")
		}
		return zero, fmt.Errorf("%s: %s", response.Error.Code, response.Error.Message)
	}
	if len(response.Result) == 0 {
		return zero, nil
	}
	var result T
	if err := json.Unmarshal(response.Result, &result); err != nil {
		return zero, err
	}
	return result, nil
}

func WaitForSocket(path string, timeout time.Duration) error {
	deadline := time.Now().Add(timeout)
	for {
		if _, err := os.Stat(path); err == nil {
			conn, err := net.DialTimeout("unix", path, 500*time.Millisecond)
			if err == nil {
				_ = conn.Close()
				return nil
			}
		}
		if time.Now().After(deadline) {
			return fmt.Errorf("socket %s not ready", path)
		}
		time.Sleep(100 * time.Millisecond)
	}
}

func NewUnixHTTPClient(socketPath string) *http.Client {
	return &http.Client{
		Transport: &http.Transport{
			DialContext: func(ctx context.Context, network, addr string) (net.Conn, error) {
				return (&net.Dialer{}).DialContext(ctx, "unix", socketPath)
			},
		},
	}
}