package jsonrpc

import (
	"bytes"
	"encoding/json"
	"fmt"
	"io/ioutil"
	"log"
	"net/http"
)

// Client json rpc client
type Client struct {
	// URL is remote url, ex http://username:password@192.168.1.3:1001/jsonrpc
	URL string
	// http client, default is http.DefaultClient
	HTTPClient *http.Client
	id         uint64
	// Debug set to true, log the send/recevied http data
	Debug bool
}

type request struct {
	Version string      `json:"jsonrpc"`
	Method  string      `json:"method"`
	Params  interface{} `json:"params"`
	ID      uint64      `json:"id"`
}

type response struct {
	Version string          `json:"jsonrpc"`
	Result  json.RawMessage `json:"result"`
	Error   *errorObj       `json:"error"`
	ID      uint64          `json:"id"`
}

type errorObj struct {
	Code    int         `json:"code"`
	Message string      `json:"message"`
	Data    interface{} `json:"data"`
}

// NewClient create a new jsonrpc client
func NewClient(url string) (*Client, error) {
	return &Client{URL: url, HTTPClient: http.DefaultClient}, nil
}

func (c *Client) nextID() uint64 {
	c.id++
	return c.id
}

// Call invoke a method with args and return reply
func (c *Client) Call(method string, args interface{}, reply interface{}) error {
	client := c.HTTPClient
	if client == nil {
		client = http.DefaultClient
	}

	if args == nil {
		args = []string{}
	}

	r := &request{
		Version: "2.0",
		Method:  method,
		Params:  args,
		ID:      c.nextID(),
	}

	data, err := json.Marshal(r)
	if err != nil {
		return err
	}

	if c.Debug {
		log.Println("send", string(data))
	}

	body := bytes.NewBuffer(data)

	req, err := http.NewRequest("POST", c.URL, body)
	if err != nil {
		return err
	}

	req.Header.Set("Content-Type", "application/json")

	resp, err := client.Do(req)
	if err != nil {
		return err
	}

	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		return fmt.Errorf("http error: %s", resp.Status)
	}

	data, err = ioutil.ReadAll(resp.Body)
	if err != nil {
		return err
	}

	if c.Debug {
		log.Println("recevied", string(data))
	}

	var res response

	if err = json.Unmarshal(data, &res); err != nil {
		return err
	}

	if res.Error != nil {
		return fmt.Errorf("%d: %s", res.Error.Code, res.Error.Message)
	}

	return json.Unmarshal(res.Result, &reply)
}