package falseknees

import (
	"context"
	"errors"
	"fmt"
	"io/ioutil"
	"math/rand"
	"net/http"
	"regexp"
	"strconv"
	"time"
)

var (
	updateInterval = time.Minute * 30
	baseURL        = "https://www.falseknees.com/"
	currentRe      = regexp.MustCompile(`window\.location\.href.+"(.+)\.html"`)
	imageRe        = regexp.MustCompile(`src="(imgs.+\.png)".+title="(.+)"`)

	current    int
	lastUpdate time.Time
)

// Comic is a FalseKnees comic
type Comic struct {
	Num   int
	Title string
	Img   string
}

// Comic returns a specific Comic
func (c *Client) Comic(ctx context.Context, num int) (*Comic, error) {
	return c.comic(ctx, num)
}

// Current returns the current Comic
func (c *Client) Current(ctx context.Context) (*Comic, error) {
	if err := c.updateCurrent(ctx); err != nil {
		return nil, err
	}
	return c.Comic(ctx, current)
}

// Random returns a random Comic
func (c *Client) Random(ctx context.Context) (*Comic, error) {
	if err := c.updateCurrent(ctx); err != nil {
		return nil, err
	}
	rand.Seed(time.Now().UnixNano())
	return c.Comic(ctx, rand.Intn(current)+1)
}

func (c *Client) updateCurrent(ctx context.Context) error {
	now := time.Now()
	if !lastUpdate.IsZero() && lastUpdate.After(now.Add(-updateInterval)) {
		return nil
	}
	lastUpdate = now

	u := fmt.Sprintf("%sindex.html", baseURL)

	req, err := http.NewRequestWithContext(ctx, http.MethodGet, u, nil)
	if err != nil {
		return err
	}

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

	if resp.StatusCode != http.StatusOK {
		return fmt.Errorf("could not get page for index: %s", resp.Status)
	}

	body, err := ioutil.ReadAll(resp.Body)
	if err != nil {
		return err
	}
	defer resp.Body.Close()

	match := currentRe.FindStringSubmatch(string(body))
	if len(match) == 0 {
		return errors.New("could not find current comic")
	}

	curr, err := strconv.Atoi(match[1])
	if err != nil {
		return err
	}

	current = curr
	return nil
}

func (c *Client) comic(ctx context.Context, num int) (*Comic, error) {
	u := fmt.Sprintf("%s%d.html", baseURL, num)

	req, err := http.NewRequestWithContext(ctx, http.MethodGet, u, nil)
	if err != nil {
		return nil, err
	}

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

	if resp.StatusCode != http.StatusOK {
		return nil, fmt.Errorf("could not get page for comic %d: %s", num, resp.Status)
	}

	body, err := ioutil.ReadAll(resp.Body)
	if err != nil {
		return nil, err
	}
	defer resp.Body.Close()

	match := imageRe.FindStringSubmatch(string(body))
	if len(match) == 0 {
		return nil, fmt.Errorf("could not find comic #%d", num)
	}

	return &Comic{
		Num:   num,
		Title: match[2],
		Img:   fmt.Sprintf("%s%s", baseURL, match[1]),
	}, nil
}