package client

import (
	"bytes"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"net/url"
	"time"
)

type Client struct {
	baseURL string
	http    *http.Client
}

func New(baseURL string) *Client {
	return &Client{
		baseURL: baseURL,
		http:    &http.Client{Timeout: 10 * time.Second},
	}
}

type listResponse struct {
	Servers []string `json:"servers"`
}

type addRequest struct {
	Address string `json:"address"`
}

type errorResponse struct {
	Error string `json:"error"`
}

func (c *Client) List() ([]string, error) {
	req, err := http.NewRequest(http.MethodGet, c.baseURL+"/dns", nil)
	if err != nil {
		return nil, err
	}
	resp, err := c.http.Do(req)
	if err != nil {
		return nil, err
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		return nil, decodeError(resp)
	}
	var lr listResponse
	if err := json.NewDecoder(resp.Body).Decode(&lr); err != nil {
		return nil, fmt.Errorf("decode response: %w", err)
	}
	return lr.Servers, nil
}

func (c *Client) Add(addr string) error {
	body, err := json.Marshal(addRequest{Address: addr})
	if err != nil {
		return err
	}
	req, err := http.NewRequest(http.MethodPost, c.baseURL+"/dns", bytes.NewReader(body))
	if err != nil {
		return err
	}
	req.Header.Set("Content-Type", "application/json")

	resp, err := c.http.Do(req)
	if err != nil {
		return err
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusCreated {
		return decodeError(resp)
	}
	return nil
}

func (c *Client) Remove(addr string) error {
	u := c.baseURL + "/dns/" + url.PathEscape(addr)
	req, err := http.NewRequest(http.MethodDelete, u, nil)
	if err != nil {
		return err
	}
	resp, err := c.http.Do(req)
	if err != nil {
		return err
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusNoContent {
		return decodeError(resp)
	}
	return nil
}

func decodeError(resp *http.Response) error {
	body, _ := io.ReadAll(resp.Body)
	var er errorResponse
	if json.Unmarshal(body, &er) == nil && er.Error != "" {
		return fmt.Errorf("server returned %s: %s", resp.Status, er.Error)
	}
	return fmt.Errorf("server returned %s: %s", resp.Status, string(body))
}