package twhelp

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

const (
	defaultUserAgent = "TWHelpDCBot/development"
	defaultTimeout   = 10 * time.Second

	endpointListVersions = "/api/v1/versions"
	endpointGetServer    = "/api/v1/versions/%s/servers/%s"
)

type Client struct {
	userAgent string
	client    *http.Client
	baseURL   *url.URL
}

type ClientOption func(c *Client)

func WithHTTPClient(hc *http.Client) ClientOption {
	return func(c *Client) {
		c.client = hc
	}
}

func WithUserAgent(ua string) ClientOption {
	return func(c *Client) {
		c.userAgent = ua
	}
}

func NewClient(baseURL *url.URL, opts ...ClientOption) *Client {
	c := &Client{
		baseURL:   baseURL,
		userAgent: defaultUserAgent,
		client: &http.Client{
			Timeout: defaultTimeout,
		},
	}
	for _, opt := range opts {
		opt(c)
	}
	return c
}

func (c *Client) ListVersions(ctx context.Context) ([]Version, error) {
	var resp listVersionsResp
	if err := c.getJSON(ctx, endpointListVersions, &resp); err != nil {
		return nil, err
	}
	return resp.Data, nil
}

func (c *Client) GetServer(ctx context.Context, version, server string) (Server, error) {
	var resp getServerResp
	if err := c.getJSON(ctx, fmt.Sprintf(endpointGetServer, version, server), &resp); err != nil {
		return Server{}, err
	}
	return resp.Data, nil
}

func (c *Client) getJSON(ctx context.Context, urlStr string, v any) error {
	u, err := c.baseURL.Parse(urlStr)
	if err != nil {
		return fmt.Errorf("c.baseURL.Parse: %w", err)
	}

	req, err := http.NewRequestWithContext(ctx, http.MethodGet, u.String(), nil)
	if err != nil {
		return fmt.Errorf("http.NewRequestWithContext: %w", err)
	}

	// headers
	req.Header.Set("User-Agent", c.userAgent)

	resp, err := c.client.Do(req)
	if err != nil {
		return fmt.Errorf("client.Do: %w", err)
	}
	defer func() {
		_ = resp.Body.Close()
	}()

	if resp.StatusCode != http.StatusOK {
		var errResp errorResp
		if err = json.NewDecoder(resp.Body).Decode(&errResp); err != nil {
			_, _ = io.Copy(io.Discard, resp.Body)
			return fmt.Errorf("got non-ok HTTP status: %d", resp.StatusCode)
		}
		return errResp.Error
	}

	if err = json.NewDecoder(resp.Body).Decode(v); err != nil {
		return fmt.Errorf("couldn't decode resp body: %w", err)
	}

	return nil
}