package router

import (
	"fmt"
	"net/http"
	"os"
	"path/filepath"
	"strings"

	"github.com/gin-gonic/gin"
	"go.uber.org/zap"
)

type agentStaticPaths struct {
	binDir    string
	deployDir string
}

var agentBinaryFiles = map[string]string{
	"linux-amd64":   "aiops-agent-linux-amd64",
	"linux-arm64":   "aiops-agent-linux-arm64",
	"windows-amd64": "aiops-agent-windows-amd64.exe",
}

// registerAgentDownloads 注册 Agent 安装脚本和二进制下载路由，避免维护 backend/agent 重复目录。 // Logan.Li
func registerAgentDownloads(r *gin.Engine, log *zap.Logger) {
	paths := resolveAgentStaticPaths(log)

	r.GET("/agent/arch", func(c *gin.Context) {
		base := requestBaseURL(c)
		if base == "" {
			c.JSON(http.StatusBadRequest, gin.H{"error": "request host is required"})
			return
		}
		downloads := availableAgentDownloads(paths.binDir)
		c.JSON(http.StatusOK, gin.H{
			"version":   "1.0.0",
			"downloads": downloads,
			"install":   fmt.Sprintf("curl -fsSL %s/agent/install.sh | sudo bash -s -- --server %s --token <token>", base, base),
		})
	})

	r.GET("/agent/install.sh", func(c *gin.Context) {
		serveAgentStaticFile(c, paths.deployDir, "install.sh")
	})
	r.GET("/agent/install.ps1", func(c *gin.Context) {
		serveAgentStaticFile(c, paths.deployDir, "install.ps1")
	})
	for _, fileName := range agentBinaryFiles {
		name := fileName
		r.GET("/agent/"+name, func(c *gin.Context) {
			serveAgentStaticFile(c, paths.binDir, name)
		})
	}
	r.GET("/agent/bin/:file", func(c *gin.Context) {
		serveAgentStaticFile(c, paths.binDir, c.Param("file"))
	})
	r.GET("/api/agent/bin/:file", func(c *gin.Context) {
		serveAgentStaticFile(c, paths.binDir, c.Param("file"))
	})
}

// resolveAgentStaticPaths 按部署形态寻找唯一 Agent 资源目录：容器优先，其次项目根目录。 // Logan.Li
func resolveAgentStaticPaths(log *zap.Logger) agentStaticPaths {
	paths := agentStaticPaths{
		binDir: firstExistingDir([]string{
			"/app/agent/bin",
			"./agent/bin",
			"../agent/bin",
		}),
		deployDir: firstExistingDir([]string{
			"/app/agent/deploy",
			"./agent/deploy",
			"../agent/deploy",
		}),
	}
	if log != nil {
		log.Info("Agent 静态资源目录已解析",
			zap.String("bin_dir", paths.binDir),
			zap.String("deploy_dir", paths.deployDir),
		)
	}
	return paths
}

func firstExistingDir(candidates []string) string {
	for _, candidate := range candidates {
		info, err := os.Stat(candidate)
		if err == nil && info.IsDir() {
			return candidate
		}
	}
	return ""
}

func availableAgentDownloads(binDir string) gin.H {
	downloads := gin.H{}
	for platform, fileName := range agentBinaryFiles {
		if binDir == "" {
			continue
		}
		fullPath := filepath.Join(binDir, fileName)
		if info, err := os.Stat(fullPath); err == nil && !info.IsDir() {
			downloads[platform] = "/agent/" + fileName
		}
	}
	return downloads
}

func requestBaseURL(c *gin.Context) string {
	scheme := "http"
	if c.Request.TLS != nil {
		scheme = "https"
	}
	if proto := c.GetHeader("X-Forwarded-Proto"); proto != "" {
		// 多级代理可能传逗号列表，首项是客户端最初使用的协议。 // Logan.Li
		scheme = strings.TrimSpace(strings.Split(proto, ",")[0])
	}
	host := c.Request.Host
	if forwardedHost := c.GetHeader("X-Forwarded-Host"); forwardedHost != "" {
		// 多级代理可能传逗号列表，首项是客户端最初访问的域名。 // Logan.Li
		host = strings.TrimSpace(strings.Split(forwardedHost, ",")[0])
	}
	if host == "" {
		// HTTP/1.1 正常请求必须带 Host，缺失时不再伪造本机地址。 // Logan.Li
		return ""
	}
	return fmt.Sprintf("%s://%s", scheme, host)
}

func serveAgentStaticFile(c *gin.Context, dir string, fileName string) {
	if dir == "" {
		c.JSON(http.StatusNotFound, gin.H{"error": "agent static directory not found"})
		return
	}
	if strings.Contains(fileName, "/") || strings.Contains(fileName, "\\") || fileName == "" {
		c.JSON(http.StatusBadRequest, gin.H{"error": "invalid agent file"})
		return
	}
	fullPath := filepath.Join(dir, fileName)
	if info, err := os.Stat(fullPath); err != nil || info.IsDir() {
		c.JSON(http.StatusNotFound, gin.H{"error": "agent file not found"})
		return
	}
	c.File(fullPath)
}