// Package fingerprint 提供每节点稳定的浏览器身份模版（P0）。
//
// 自洽：impersonate / User-Agent / sec-ch-ua / platform 钉在同一 Chrome 大版本。
// 上限跟 curl_cffi 能仿的桌面档（chrome136），禁止再写 Chrome/151 + Go TLS。
package fingerprint

import (
	"crypto/sha256"
	"encoding/binary"
	"fmt"
	"os"
	"strconv"
)

// 钉死与 curl_cffi 0.13 桌面上限对齐（DaaS fp-v2 同代）。
const (
	ChromeMajor        = 136
	DefaultImpersonate = "chrome136"
	TemplateCount      = 8 // 每节点落库套数，便于切换；内存只持有 active
)

// Profile 一张自洽脸。字段均可落库。
type Profile struct {
	ID              string `json:"id"`
	OS              string `json:"os"` // Windows | macOS
	ChromeMajor     int    `json:"chrome_major"`
	Impersonate     string `json:"impersonate"`
	UserAgent       string `json:"user_agent"`
	SecCHUA         string `json:"sec_ch_ua"`
	SecCHUAMobile   string `json:"sec_ch_ua_mobile"`
	SecCHUAPlatform string `json:"sec_ch_ua_platform"`
	AcceptLanguage  string `json:"accept_language"`
}

var (
	viewLangs = []string{
		"en-US,en;q=0.9",
		"en-US,en;q=0.8",
		"en-US,en;q=0.9,zh-CN;q=0.6",
		"zh-CN,zh;q=0.9,en;q=0.8",
		"en-GB,en;q=0.9,en-US;q=0.8",
	}
	winNT  = []string{"10.0", "10.0", "11.0"}
	macOSX = []string{"10_15_7", "13_6_1", "14_4_0", "14_2_1"}
)

// NodeID 生产节点稳定种子（Swarm HOSTNAME；缺省本机 hostname）。
func NodeID() string {
	if v := os.Getenv("HOSTNAME"); v != "" {
		return v
	}
	h, err := os.Hostname()
	if err != nil || h == "" {
		return "unknown-node"
	}
	return h
}

// Allocate 由 seed 确定性生成一张脸（同 seed 永同脸）。
func Allocate(seed string) Profile {
	s := seedInt(seed)
	osFamily := "Windows"
	if s%2 == 1 {
		osFamily = "macOS"
	}
	major := ChromeMajor
	impersonate := DefaultImpersonate
	lang := viewLangs[(s>>8)%uint64(len(viewLangs))]
	buildPatch := (s >> 16) % 10000
	buildMinor := (s >> 4) % 10000
	var ua, platform, tid string
	if osFamily == "Windows" {
		nt := winNT[(s>>12)%uint64(len(winNT))]
		ua = fmt.Sprintf(
			"Mozilla/5.0 (Windows NT %s; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/%d.0.%d.%d Safari/537.36",
			nt, major, buildPatch, buildMinor)
		platform = `"Windows"`
		tid = fmt.Sprintf("win-chrome%d-%06d", major, s%1_000_000)
	} else {
		osx := macOSX[(s>>12)%uint64(len(macOSX))]
		ua = fmt.Sprintf(
			"Mozilla/5.0 (Macintosh; Intel Mac OS X %s) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/%d.0.%d.%d Safari/537.36",
			osx, major, buildPatch, buildMinor)
		platform = `"macOS"`
		tid = fmt.Sprintf("mac-chrome%d-%06d", major, s%1_000_000)
	}
	return Profile{
		ID:              tid,
		OS:              osFamily,
		ChromeMajor:     major,
		Impersonate:     impersonate,
		UserAgent:       ua,
		SecCHUA:         secCHUA(major),
		SecCHUAMobile:   "?0",
		SecCHUAPlatform: platform,
		AcceptLanguage:  lang,
	}
}

// AllocateSet 为节点生成 n 套互异模版。
func AllocateSet(nodeID string, n int) []Profile {
	if n <= 0 {
		n = TemplateCount
	}
	out := make([]Profile, n)
	for i := 0; i < n; i++ {
		out[i] = Allocate(nodeID + "|" + strconv.Itoa(i))
	}
	return out
}

// PickActive 从集合里按节点 hash 选主模版（重启不变）。
func PickActive(nodeID string, set []Profile) Profile {
	if len(set) == 0 {
		return Allocate(nodeID)
	}
	return set[int(seedInt(nodeID+"|active")%uint64(len(set)))]
}

// Headers 与 impersonate 对齐的导航头（顺序接近桌面 Chrome）。
func Headers(p Profile) map[string]string {
	return map[string]string{
		"User-Agent":                p.UserAgent,
		"Accept":                    "text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8",
		"Accept-Language":           p.AcceptLanguage,
		"Accept-Encoding":           "gzip, deflate, br",
		"Upgrade-Insecure-Requests": "1",
		"Sec-Fetch-Dest":            "document",
		"Sec-Fetch-Mode":            "navigate",
		"Sec-Fetch-Site":            "none",
		"Sec-Fetch-User":            "?1",
		"sec-ch-ua":                 p.SecCHUA,
		"sec-ch-ua-mobile":          p.SecCHUAMobile,
		"sec-ch-ua-platform":        p.SecCHUAPlatform,
	}
}

func secCHUA(major int) string {
	return fmt.Sprintf(`"Google Chrome";v="%d", "Chromium";v="%d", "Not_A Brand";v="24"`, major, major)
}

func seedInt(s string) uint64 {
	sum := sha256.Sum256([]byte("fp-v2|" + s))
	return binary.BigEndian.Uint64(sum[:8])
}