package realdebrid

import (
	"math"
	"net/http"
	"strings"
	"time"
)

func RetryUntilOk[T any](fn func() (T, error)) T {
	const initialDelay = 1 * time.Second
	const maxDelay = 128 * time.Second
	for i := 0; ; i++ {
		result, err := fn()
		if err == nil || !strings.Contains(err.Error(), "429") {
			return result
		}
		delay := time.Duration(math.Min(float64(initialDelay*time.Duration(math.Pow(2, float64(i)))), float64(maxDelay)))
		time.Sleep(delay)
	}
}

func canFetchFirstByte(url string) bool {
	// Create a new HTTP request
	req, err := http.NewRequest("GET", url, nil)
	if err != nil {
		return false
	}

	// Set the Range header to request only the first byte
	req.Header.Set("Range", "bytes=0-0")

	// Execute the request
	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		return false
	}
	defer resp.Body.Close()

	// If server supports partial content
	if resp.StatusCode == http.StatusPartialContent {
		buffer := make([]byte, 1)
		_, err := resp.Body.Read(buffer)
		return err == nil
	}
	if resp.StatusCode != http.StatusOK {
		return false
	}
	// If server doesn't support partial content, try reading the first byte and immediately close
	buffer := make([]byte, 1)
	_, err = resp.Body.Read(buffer)
	resp.Body.Close() // Close immediately after reading
	return err == nil
}