package httpclient

import (
	"bytes"
	"context"
	"fmt"
	"io"
	"log"
	"net/http"
	"net/url"
	"strconv"
	"sync"
	"time"

	"github.com/sardanioss/httpcloak"
	"golang.org/x/time/rate"
)

const defaultUserAgent = "Mozilla/5.0 (Linux; Android 10; K) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/124.0.0.0 Mobile Safari/537.36"

var (
	verboseLog    bool
	defaultOnce   sync.Once
	defaultClient *Client
)

func SetVerboseLog(enabled bool) { verboseLog = enabled }

func DefaultClient() *Client {
	defaultOnce.Do(func() {
		defaultClient = newClient()
	})
	return defaultClient
}

func NewClient(opts ...Option) *Client {
	c := newClient()
	for _, o := range opts {
		o(c)
	}
	return c
}

func newClient() *Client {
	hc := httpcloak.NewSession("chrome-latest",
		httpcloak.WithSessionTimeout(30*time.Second),
	)
	c := &Client{
		hc:         hc,
		fsClient:   nil,
		rateLimit:  1,
		burst:      1,
		userAgent:  defaultUserAgent,
		limiters:   map[string]*rate.Limiter{},
		verboseLog: verboseLog,
	}
	fsClient, err := NewFlareSolverrClient()
	if err == nil {
		c.fsClient = fsClient
	}
	return c
}

type Client struct {
	hc        *httpcloak.Session
	fsClient  *FlareSolverrClient
	rateLimit float64
	burst     int
	userAgent string
	verboseLog bool

	mu       sync.Mutex
	limiters map[string]*rate.Limiter
}

type Option func(*Client)

func WithRateLimit(rps float64, burst int) Option {
	return func(c *Client) {
		c.rateLimit = rps
		c.burst = burst
	}
}

func WithTimeout(d time.Duration) Option {
	return func(c *Client) { c.hc = httpcloak.NewSession("chrome-latest",
		httpcloak.WithSessionTimeout(d),
	) }
}

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

func WithVerboseLog(enabled bool) Option {
	return func(c *Client) { c.verboseLog = enabled }
}

func (c *Client) limiter(host string) *rate.Limiter {
	c.mu.Lock()
	defer c.mu.Unlock()
	l, ok := c.limiters[host]
	if !ok {
		l = rate.NewLimiter(rate.Limit(c.rateLimit), c.burst)
		c.limiters[host] = l
	}
	return l
}

// Do tries a direct request via httpcloak (Chrome TLS fingerprint) first.
// httpcloak's TLS fingerprint matches Chrome, so if we already have a
// cf_clearance cookie from a previous FlareSolverr solve, Cloudflare won't
// challenge us. If we do get challenged (403/503), falls back to FlareSolverr.
func (c *Client) Do(req *http.Request) (*http.Response, error) {
	if err := c.limiter(req.URL.Host).Wait(req.Context()); err != nil {
		return nil, err
	}

	resp, err := c.doDirect(req)
	var directStatus int
	if err == nil {
		directStatus = resp.StatusCode
		if resp.StatusCode != http.StatusForbidden && resp.StatusCode != http.StatusServiceUnavailable {
			return resp, nil
		}
		resp.Body.Close()
	}

	if c.fsClient == nil {
		if err != nil {
			return nil, err
		}
		return nil, fmt.Errorf("HTTP %d (challenge detected but FlareSolverr not configured)", resp.StatusCode)
	}

	return c.doFS(req, directStatus)
}

func (c *Client) doDirect(req *http.Request) (*http.Response, error) {
	if c.verboseLog {
		log.Printf("[httpclient] DIRECT %s %s", req.Method, req.URL.String())
	}
	if req.Header.Get("User-Agent") == "" {
		req.Header.Set("User-Agent", c.userAgent)
	}

	hreq := &httpcloak.Request{
		Method:  req.Method,
		URL:     req.URL.String(),
		Headers: req.Header,
	}
	if req.Body != nil {
		hreq.Body = req.Body
	}

	hresp, err := c.hc.Do(req.Context(), hreq)
	if err != nil {
		return nil, err
	}

	body, err := hresp.Bytes()
	if err != nil {
		return nil, err
	}

	if c.verboseLog {
		log.Printf("[httpclient] DIRECT RESPONSE %s status=%d", req.URL.String(), hresp.StatusCode)
	}

	return &http.Response{
		StatusCode:    hresp.StatusCode,
		Header:        hresp.Headers,
		Body:          io.NopCloser(bytes.NewReader(body)),
		ContentLength: int64(len(body)),
		Request:       req,
	}, nil
}

func (c *Client) doFS(req *http.Request, directStatus int) (*http.Response, error) {
	if c.verboseLog {
		log.Printf("[httpclient] FS FALLBACK %s %s", req.Method, req.URL.String())
	}

	rawURL := req.URL.String()
	rawBody, statusCode, fsHeaders, cookies, fsRespURL, err := c.fsClient.GetRaw(req.Context(), rawURL)
	if err != nil {
		return nil, err
	}

	respURL := rawURL
	if fsRespURL != "" {
		respURL = fsRespURL
	}

	// Feed FS cookies into the httpcloak session for subsequent direct requests
	if len(cookies) > 0 {
		if parsedRespURL, uErr := url.Parse(respURL); uErr == nil {
			for _, ck := range cookies {
				if ck.Domain == "" {
					ck.Domain = parsedRespURL.Host
				}
				c.hc.SetCookie(ck.Name, ck.Value)
			}
		}
	}

	// Check if FS returned challenge page instead of real content
	if statusCode == 200 && isCloudflareChallenge([]byte(rawBody)) {
		if directStatus >= 400 {
			statusCode = directStatus
		} else {
			return nil, fmt.Errorf("FlareSolverr returned challenge page for %s", rawURL)
		}
	}

	hdr := make(http.Header)
	if len(fsHeaders) > 0 {
		for k, v := range fsHeaders {
			switch val := v.(type) {
			case string:
				hdr.Set(k, val)
			case []any:
				for _, sv := range val {
					hdr.Add(k, fmt.Sprint(sv))
				}
			}
		}
	}
	if len(cookies) > 0 {
		for _, ck := range cookies {
			hdr.Add("Set-Cookie", ck.String())
		}
	}
	for k, v := range req.Header {
		if hdr.Get(k) == "" {
			hdr[k] = v
		}
	}

	body := stripFSWrapper([]byte(rawBody))

	return &http.Response{
		StatusCode: statusCode,
		Header:     hdr,
		Body:       io.NopCloser(bytes.NewReader(body)),
		Request:    req,
	}, nil
}

func (c *Client) HTTPClient() *http.Client {
	return &http.Client{
		Transport: hcTransport{c.hc},
		Timeout:   30 * time.Second,
	}
}

// hcTransport wraps httpcloak.Session as an http.RoundTripper
type hcTransport struct {
	hc *httpcloak.Session
}

func (t hcTransport) RoundTrip(req *http.Request) (*http.Response, error) {
	var body io.Reader
	if req.Body != nil {
		body = req.Body
	}
	hreq := &httpcloak.Request{
		Method:  req.Method,
		URL:     req.URL.String(),
		Headers: req.Header,
		Body:    body,
	}
	hresp, err := t.hc.Do(req.Context(), hreq)
	if err != nil {
		return nil, err
	}
	bodyBytes, err := hresp.Bytes()
	if err != nil {
		return nil, err
	}
	return &http.Response{
		StatusCode:    hresp.StatusCode,
		Header:        hresp.Headers,
		Body:          io.NopCloser(bytes.NewReader(bodyBytes)),
		ContentLength: int64(len(bodyBytes)),
		Request:       req,
	}, nil
}

func (c *Client) Cookie(name, host string) string {
	cks := c.hc.GetCookies()
	if v, ok := cks[name]; ok {
		return v
	}
	return ""
}

// Get is a convenience wrapper around Do.
func (c *Client) Get(ctx context.Context, urlStr string) (*http.Response, error) {
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, urlStr, nil)
	if err != nil {
		return nil, err
	}
	return c.Do(req)
}

// Post is a convenience wrapper around Do.
func (c *Client) Post(ctx context.Context, urlStr string, bodyType string, body io.Reader) (*http.Response, error) {
	req, err := http.NewRequestWithContext(ctx, http.MethodPost, urlStr, body)
	if err != nil {
		return nil, err
	}
	req.Header.Set("Content-Type", bodyType)
	return c.Do(req)
}

// isCloudflareChallenge detects whether the response body is a Cloudflare
// challenge page (i.e. FS failed to solve it and Chrome rendered the challenge).
func isCloudflareChallenge(body []byte) bool {
	indicators := []string{
		"Just a moment...",
		"cf_chl_opt",
		"challenges.cloudflare.com",
		"/cdn-cgi/challenge-platform",
		"Enable JavaScript and cookies",
	}
	for _, ind := range indicators {
		if bytes.Contains(body, []byte(ind)) {
			return true
		}
	}
	return false
}

// stripFSWrapper removes FlareSolverr's Chrome HTML wrapper.
func stripFSWrapper(body []byte) []byte {
	if !bytes.HasPrefix(bytes.TrimSpace(body), []byte("<html")) {
		return body
	}
	preStart := bytes.Index(body, []byte("<pre>"))
	if preStart < 0 {
		return body
	}
	preEnd := bytes.LastIndex(body, []byte("</pre>"))
	if preEnd <= preStart {
		return body
	}
	return body[preStart+5 : preEnd]
}

func retryAfter(resp *http.Response) time.Duration {
	ra := resp.Header.Get("Retry-After")
	if ra == "" {
		return 5 * time.Second
	}
	if secs, err := strconv.ParseFloat(ra, 64); err == nil {
		return time.Duration(secs * float64(time.Second))
	}
	if t, err := http.ParseTime(ra); err == nil {
		d := time.Until(t)
		if d > 0 {
			return d
		}
	}
	return 5 * time.Second
}