package splithttp

import (
	"crypto/rand"
	"math/big"
	"net/http"
	"net/url"
	"strings"

	"github.com/xtls/xray-core/common"
	"github.com/xtls/xray-core/core"
	"github.com/xtls/xray-core/transport/internet"
)

const paddingQuery = "x_padding"

func (c *Config) GetNormalizedPath() string {
	pathAndQuery := strings.SplitN(c.Path, "?", 2)
	path := pathAndQuery[0]

	if path == "" || path[0] != '/' {
		path = "/" + path
	}

	if path[len(path)-1] != '/' {
		path = path + "/"
	}

	return path
}

func (c *Config) GetNormalizedQuery() string {
	pathAndQuery := strings.SplitN(c.Path, "?", 2)
	query := ""

	if len(pathAndQuery) > 1 {
		query = pathAndQuery[1]
	}

	if query != "" {
		query += "&"
	}
	query += "x_version=" + core.Version()

	return query
}

func (c *Config) GetRequestHeader() http.Header {
	header := http.Header{}
	for k, v := range c.Headers {
		header.Add(k, v)
	}

	paddingLen := c.GetNormalizedXPaddingBytes().rand()
	if paddingLen > 0 {
		query, err := url.ParseQuery(c.GetNormalizedQuery())
		if err != nil {
			query = url.Values{}
		}
		// https://www.rfc-editor.org/rfc/rfc7541.html#appendix-B
		// h2's HPACK Header Compression feature employs a huffman encoding using a static table.
		// 'X' is assigned an 8 bit code, so HPACK compression won't change actual padding length on the wire.
		// https://www.rfc-editor.org/rfc/rfc9204.html#section-4.1.2-2
		// h3's similar QPACK feature uses the same huffman table.
		query.Set(paddingQuery, strings.Repeat("X", int(paddingLen)))

		referrer := url.URL{
			Scheme:   "https", // maybe http actually, but this part is not being checked
			Host:     c.Host,
			Path:     c.GetNormalizedPath(),
			RawQuery: query.Encode(),
		}

		header.Set("Referer", referrer.String())
	}
	return header
}

func (c *Config) WriteResponseHeader(writer http.ResponseWriter) {
	// CORS headers for the browser dialer
	writer.Header().Set("Access-Control-Allow-Origin", "*")
	writer.Header().Set("Access-Control-Allow-Methods", "GET, POST")
	writer.Header().Set("X-Version", core.Version())
	paddingLen := c.GetNormalizedXPaddingBytes().rand()
	if paddingLen > 0 {
		writer.Header().Set("X-Padding", strings.Repeat("X", int(paddingLen)))
	}
}

func (c *Config) GetNormalizedXPaddingBytes() RangeConfig {
	if c.XPaddingBytes == nil || c.XPaddingBytes.To == 0 {
		return RangeConfig{
			From: 100,
			To:   1000,
		}
	}

	return *c.XPaddingBytes
}

func (c *Config) GetNormalizedScMaxEachPostBytes() RangeConfig {
	if c.ScMaxEachPostBytes == nil || c.ScMaxEachPostBytes.To == 0 {
		return RangeConfig{
			From: 1000000,
			To:   1000000,
		}
	}

	return *c.ScMaxEachPostBytes
}

func (c *Config) GetNormalizedScMinPostsIntervalMs() RangeConfig {
	if c.ScMinPostsIntervalMs == nil || c.ScMinPostsIntervalMs.To == 0 {
		return RangeConfig{
			From: 30,
			To:   30,
		}
	}

	return *c.ScMinPostsIntervalMs
}

func (c *Config) GetNormalizedScMaxBufferedPosts() int {
	if c.ScMaxBufferedPosts == 0 {
		return 30
	}

	return int(c.ScMaxBufferedPosts)
}

func (m *XmuxConfig) GetNormalizedMaxConcurrency() RangeConfig {
	if m.MaxConcurrency == nil {
		return RangeConfig{
			From: 0,
			To:   0,
		}
	}

	return *m.MaxConcurrency
}

func (m *XmuxConfig) GetNormalizedMaxConnections() RangeConfig {
	if m.MaxConnections == nil {
		return RangeConfig{
			From: 0,
			To:   0,
		}
	}

	return *m.MaxConnections
}

func (m *XmuxConfig) GetNormalizedCMaxReuseTimes() RangeConfig {
	if m.CMaxReuseTimes == nil {
		return RangeConfig{
			From: 0,
			To:   0,
		}
	}

	return *m.CMaxReuseTimes
}

func (m *XmuxConfig) GetNormalizedHMaxRequestTimes() RangeConfig {
	if m.HMaxRequestTimes == nil {
		return RangeConfig{
			From: 0,
			To:   0,
		}
	}

	return *m.HMaxRequestTimes
}

func (m *XmuxConfig) GetNormalizedHMaxReusableSecs() RangeConfig {
	if m.HMaxReusableSecs == nil {
		return RangeConfig{
			From: 0,
			To:   0,
		}
	}

	return *m.HMaxReusableSecs
}

func init() {
	common.Must(internet.RegisterProtocolConfigCreator(protocolName, func() interface{} {
		return new(Config)
	}))
}

func (c RangeConfig) rand() int32 {
	if c.From == c.To {
		return c.From
	}
	bigInt, _ := rand.Int(rand.Reader, big.NewInt(int64(c.To-c.From)))
	return c.From + int32(bigInt.Int64())
}