package toolinstaller

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

// ============================================
// 工具镜像源管理 — 每工具 ≥2 国内源 + 官方源
// 下载前先 HEAD 验证 URL 可达，再 fallback 重试
// ============================================

// ToolMirror 单个镜像源定义
type ToolMirror struct {
	Name string // 镜像名称（日志用）
	URL  string // 下载地址模板，{version} 占位符
	// Location 标记：domestic(国内)/global(国际)/internal(内网)
	Location string
}

// 工具镜像源清单
// 每个工具至少 2 个国内源 + 官方源
var toolMirrors = map[string][]ToolMirror{
	"kubectl": {
		{Name: "K8s官方", URL: "https://dl.k8s.io/release/{version}/bin/linux/amd64/kubectl", Location: "global"},
		{Name: "GCS直链", URL: "https://storage.googleapis.com/kubernetes-release/release/{version}/bin/linux/amd64/kubectl", Location: "global"},
		// 国内无 kubectl 直链镜像（阿里云/清华只托管 yum/apt 源），此处预留给内网 Harbor
		// {Name: "内网Harbor", URL: "https://harbor.ops.net/static/kubectl-{version}-linux-amd64", Location: "internal"},
	},
	"maven": {
		{Name: "Apache官方", URL: "https://dlcdn.apache.org/maven/maven-3/{version}/binaries/apache-maven-{version}-bin.tar.gz", Location: "global"},
		{Name: "清华镜像", URL: "https://mirrors.tuna.tsinghua.edu.cn/apache/maven/maven-3/{version}/binaries/apache-maven-{version}-bin.tar.gz", Location: "domestic"},
		{Name: "阿里云镜像", URL: "https://mirrors.aliyun.com/apache/maven/maven-3/{version}/binaries/apache-maven-{version}-bin.tar.gz", Location: "domestic"},
		{Name: "华为云镜像", URL: "https://repo.huaweicloud.com/apache/maven/maven-3/{version}/binaries/apache-maven-{version}-bin.tar.gz", Location: "domestic"},
	},
	"nodejs": {
		{Name: "Node官方", URL: "https://nodejs.org/dist/{version}/node-{version}-linux-x64.tar.xz", Location: "global"},
		{Name: "npmmirror", URL: "https://npmmirror.com/mirrors/node/{version}/node-{version}-linux-x64.tar.xz", Location: "domestic"},
		{Name: "清华镜像", URL: "https://mirrors.tuna.tsinghua.edu.cn/nodejs-release/{version}/node-{version}-linux-x64.tar.xz", Location: "domestic"},
		{Name: "华为云镜像", URL: "https://repo.huaweicloud.com/nodejs/{version}/node-{version}-linux-x64.tar.xz", Location: "domestic"},
		{Name: "阿里云镜像", URL: "https://mirrors.aliyun.com/nodejs-release/{version}/node-{version}-linux-x64.tar.xz", Location: "domestic"},
	},
	"helm": {
		{Name: "Helm官方", URL: "https://get.helm.sh/helm-{version}-linux-amd64.tar.gz", Location: "global"},
		{Name: "阿里云镜像", URL: "https://mirrors.aliyun.com/kubernetes/helm/{version}/helm-{version}-linux-amd64.tar.gz", Location: "domestic"},
	},
	"golang": {
		{Name: "Go官方", URL: "https://go.dev/dl/go{version}.linux-amd64.tar.gz", Location: "global"},
		{Name: "Google CN", URL: "https://golang.google.cn/dl/go{version}.linux-amd64.tar.gz", Location: "domestic"},
		{Name: "阿里云镜像", URL: "https://mirrors.aliyun.com/golang/go{version}.linux-amd64.tar.gz", Location: "domestic"},
		{Name: "中科大镜像", URL: "https://mirrors.ustc.edu.cn/golang/go{version}.linux-amd64.tar.gz", Location: "domestic"},
	},
}

// GetMirrorsForTool 返回工具的镜像源列表（按网络环境排序）。
// 国内网络 → 国内源优先；国际网络 → 官方源优先。
// 同时过滤掉不可达的镜像。
func GetMirrorsForTool(toolName, downloadURL string) []string {
	mirrors, ok := toolMirrors[toolName]
	if !ok {
		// 未配置镜像列表的工具，只返回 downloadURL
		if downloadURL != "" {
			return []string{downloadURL}
		}
		return nil
	}

	isChina := IsChinaNetwork()

	// 排序：国内网络 → 国内源排前面；国际网络 → 官方源排前面
	sorted := make([]ToolMirror, len(mirrors))
	copy(sorted, mirrors)

	// 冒泡排序（简单场景足够）
	for i := 0; i < len(sorted); i++ {
		for j := i + 1; j < len(sorted); j++ {
			// 国内网络：domestic 优先
			if isChina && sorted[j].Location == "domestic" && sorted[i].Location != "domestic" {
				sorted[i], sorted[j] = sorted[j], sorted[i]
			}
			// 国际网络：global 优先
			if !isChina && sorted[j].Location == "global" && sorted[i].Location != "global" {
				sorted[i], sorted[j] = sorted[j], sorted[i]
			}
		}
	}

	// 过滤掉不可达的镜像（HEAD 验证）
	urls := make([]string, 0, len(sorted))
	for _, m := range sorted {
		if verifyURLReachable(m.URL) {
			urls = append(urls, m.URL)
			log.Printf("[ToolMirror] ✓ %s (%s) reachable", m.Name, m.URL)
		} else {
			log.Printf("[ToolMirror] ✗ %s (%s) unreachable, skip", m.Name, m.URL)
		}
	}

	// 如果所有镜像都不可达，仍然返回全部（让下载阶段报错，而非提前过滤掉）
	if len(urls) == 0 {
		log.Printf("[ToolMirror] WARNING: all mirrors unreachable for %s, falling back to raw list", toolName)
		for _, m := range sorted {
			urls = append(urls, m.URL)
		}
	}

	// 把 downloadURL 也作为兜底放在最后（如果不在 mirrors 中）
	if downloadURL != "" && !containsURL(urls, downloadURL) {
		urls = append(urls, downloadURL)
	}

	return urls
}

// verifyURLReachable 通过 HEAD 请求（带重定向跟随）验证 URL 是否可达。
// 返回 true 表示 URL 可访问（HTTP 2xx/3xx）。
func verifyURLReachable(urlTemplate string) bool {
	// 对 URL 模板做简单替换，用已知存在的版本测试
	testURL := strings.ReplaceAll(urlTemplate, "{version}", "v1.32.0")
	testURL = strings.ReplaceAll(testURL, "{version}", "3.9.9") // maven 版本格式不同

	client := &http.Client{
		Timeout: 5 * time.Second,
		CheckRedirect: func(req *http.Request, via []*http.Request) error {
			if len(via) >= 3 {
				return http.ErrUseLastResponse
			}
			return nil
		},
	}

	resp, err := client.Head(testURL)
	if err != nil {
		return false
	}
	defer resp.Body.Close()

	// 2xx 或 3xx 都算可达
	return resp.StatusCode >= 200 && resp.StatusCode < 400
}

func containsURL(urls []string, target string) bool {
	for _, u := range urls {
		if u == target {
			return true
		}
	}
	return false
}

// VerifyAndGetBestMirror 综合检测：先 HEAD 测试所有镜像，返回第一个可达的。
// 如果全不可达，返回空字符串。
func VerifyAndGetBestMirror(toolName string, mirrors []string) string {
	for _, url := range mirrors {
		if verifyURLReachable(url) {
			return url
		}
	}
	log.Printf("[ToolMirror] WARNING: no reachable mirror found for %s", toolName)
	return ""
}