package main

import (
	"encoding/json"
	"fmt"
	"net/http"
	"regexp"
	"strconv"
	"strings"
)

// ── 从现有 nginx 配置导入路由 ──
//
// 迁移期需要把老的统一入口（portal-nginx）里已有的域名→后端映射一次性读进来，
// 否则后台"统一入口"永远是空的（本轮实际发生过）。这里不去猜文件位置，
// 而是让使用者把老的 nginx 配置贴在界面上，服务端只做解析：
// 解析结果先回给界面供确认，用户点保存/应用才真正落盘——不做任何隐式写入。

var (
	reMapEntry   = regexp.MustCompile(`(?m)^\s*([A-Za-z0-9*._-]+)\s+(https?://[^\s;]+)\s*;`)
	reServerName = regexp.MustCompile(`(?m)^\s*server_name\s+([^;]+);`)
	reProxyPass  = regexp.MustCompile(`proxy_pass\s+(\$backend|\$[A-Za-z_]+|https?://[^\s;]+)\s*;`)
)

// parseNginxConf 把老配置解析成路由初稿。
//
// 返回的 Route 一律 NavEnabled=false：导航项归 Dashy 管，导入只负责"域名→后端"，
// 勾选「加入导航」才会接管对应导航项，避免一导入就把手工维护的导航改掉。
func parseNginxConf(text string) ([]Route, error) {
	if strings.TrimSpace(text) == "" {
		return nil, fmt.Errorf("配置内容为空")
	}
	upstreams := map[string]string{}
	for _, m := range reMapEntry.FindAllStringSubmatch(text, -1) {
		host := strings.ToLower(strings.TrimSpace(m[1]))
		if host == "default" || host == "hostnames" {
			continue
		}
		upstreams[host] = m[2]
	}

	// 逐块扫描 server { }，用大括号计数找边界（配置里没有嵌套 server）
	var routes []Route
	idx := 0
	for {
		start := strings.Index(text[idx:], "server")
		if start < 0 {
			break
		}
		start += idx
		brace := strings.Index(text[start:], "{")
		if brace < 0 {
			break
		}
		open := start + brace
		depth, end := 0, -1
		for i := open; i < len(text); i++ {
			switch text[i] {
			case '{':
				depth++
			case '}':
				depth--
				if depth == 0 {
					end = i
				}
			}
			if end >= 0 {
				break
			}
		}
		if end < 0 {
			break
		}
		body := text[open+1 : end]
		idx = end + 1

		sn := reServerName.FindStringSubmatch(body)
		if sn == nil {
			continue
		}
		hosts := strings.Fields(strings.TrimSpace(sn[1]))
		if len(hosts) == 0 || (len(hosts) == 1 && hosts[0] == "_") {
			continue // 默认/兜底段不是具体服务
		}

		hasAuth := strings.Contains(body, "auth_request /_auth;")
		hasSSE := strings.Contains(body, "postpone_output 0")
		hasBeian := strings.Contains(body, "sub_filter")
		hasWS := strings.Contains(body, "Upgrade $http_upgrade")
		insecure := strings.Contains(body, "proxy_ssl_verify off")
		proxyLit := ""
		if pm := reProxyPass.FindStringSubmatch(body); pm != nil {
			proxyLit = pm[1]
		}
		bypass := []string{}
		if strings.Contains(body, "location /search") {
			bypass = append(bypass, "/search")
		}
		if strings.Contains(body, "autocompleter") {
			bypass = append(bypass, "/api/", "/autocompleter/", "/static/")
		}

		for _, host := range hosts {
			h := strings.ToLower(strings.TrimSpace(host))
			if h == "" {
				continue
			}
			up := upstreams[h]
			if up == "" && strings.HasPrefix(proxyLit, "http") {
				up = proxyLit
			}
			r := Route{
				Host:         h,
				Upstream:     up,
				RequireLogin: hasAuth,
				Websocket:    hasWS,
				Streaming:    hasSSE,
				InsecureTLS:  insecure,
				InjectBeian:  hasBeian,
				BypassPaths:  bypass,
			}
			// 登录服务与纯静态门户段没有内网后端：分别归为 auth / portal 类型
			if strings.HasPrefix(h, "login.") || strings.Contains(up, ":4001") {
				r.Kind, r.Upstream = "auth", ""
				r.RequireLogin = false
			} else if up == "" {
				r.Kind = "portal"
				r.RequireLogin = false
			}
			r.Note = "导入"
			routes = append(routes, r)
		}
	}
	if len(routes) == 0 {
		return nil, fmt.Errorf("没有解析到任何 server_name（请确认贴的是完整 nginx 配置）")
	}

	// 去重：同一域名只保留第一条
	seen := map[string]bool{}
	out := make([]Route, 0, len(routes))
	for _, r := range routes {
		if seen[r.Host] {
			continue
		}
		seen[r.Host] = true
		out = append(out, r)
	}
	// 校验一遍，早发现问题（缺后端等）比等用户点应用时才发现好
	for _, r := range out {
		if err := ValidateRoute(r); err != nil {
			return nil, err
		}
	}
	return out, nil
}

// handleGatewayImport 解析贴进来的 nginx 配置，返回路由初稿（不写盘）。
func handleGatewayImport(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		jsonErr(w, 405, "method not allowed")
		return
	}
	if !requireAdminToken(w, r) {
		return
	}
	var req struct {
		Conf string `json:"conf"`
	}
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		jsonErr(w, 400, "请求体解析失败")
		return
	}
	routes, err := parseNginxConf(req.Conf)
	if err != nil {
		jsonErr(w, 400, err.Error())
		return
	}
	jsonResp(w, map[string]any{
		"routes": routes, "count": len(routes),
		"hint": "已解析 " + strconv.Itoa(len(routes)) + " 个域名（未写入）。确认后点「保存并应用」；勾选「加入导航」的条目才会同时接管 Dashy 导航项。",
	})
}