package main

import (
	"fmt"
	"os"
	"path/filepath"
	"sort"
	"strings"

	"gopkg.in/yaml.v3"
)

// Route 同时描述一条反向代理及其在 Dashy 中的导航信息。
// Kind: proxy（普通反代）、portal（内置门户静态页）、auth（内置登录服务）。
type Route struct {
	Host         string   `yaml:"host" json:"host"`
	Kind         string   `yaml:"kind,omitempty" json:"kind,omitempty"`
	Upstream     string   `yaml:"upstream,omitempty" json:"upstream,omitempty"`
	RequireLogin bool     `yaml:"requireLogin" json:"requireLogin"`
	Websocket    bool     `yaml:"websocket" json:"websocket"`
	Streaming    bool     `yaml:"streaming,omitempty" json:"streaming,omitempty"`
	InsecureTLS  bool     `yaml:"insecureTls,omitempty" json:"insecureTls,omitempty"`
	MaxBodyMB    int      `yaml:"maxBodyMB,omitempty" json:"maxBodyMB,omitempty"`
	BypassPaths  []string `yaml:"bypassPaths,omitempty" json:"bypassPaths,omitempty"`
	InjectBeian  bool     `yaml:"injectBeian,omitempty" json:"injectBeian,omitempty"`
	Note         string   `yaml:"note,omitempty" json:"note,omitempty"`

	NavEnabled     bool   `yaml:"navEnabled,omitempty" json:"navEnabled,omitempty"`
	NavSection     string `yaml:"navSection,omitempty" json:"navSection,omitempty"`
	NavName        string `yaml:"navName,omitempty" json:"navName,omitempty"`
	NavDescription string `yaml:"navDescription,omitempty" json:"navDescription,omitempty"`
	NavURL         string `yaml:"navUrl,omitempty" json:"navUrl,omitempty"`
	NavIcon        string `yaml:"navIcon,omitempty" json:"navIcon,omitempty"`
	NavAutoIcon    bool   `yaml:"navAutoIcon,omitempty" json:"navAutoIcon,omitempty"`
}

// GatewayConfig 是统一入口的完整配置。ListenHTTPS=false 时 ListenPort 是普通
// HTTP 旁路端口；开启后 ListenPort/ListenTLSPort 都是 TLS 端口，RedirectPort
// 是 HTTP→HTTPS 入口。这样可复刻原 portal-nginx 的 3080/8443 + 3081 设计。
type GatewayConfig struct {
	ListenHTTPS bool   `yaml:"listenHttps" json:"listenHttps"`
	CertFile    string `yaml:"certFile,omitempty" json:"certFile,omitempty"`
	KeyFile     string `yaml:"keyFile,omitempty" json:"keyFile,omitempty"`
	AuthURL     string `yaml:"authUrl,omitempty" json:"authUrl,omitempty"`
	LoginURL    string `yaml:"loginUrl,omitempty" json:"loginUrl,omitempty"`

	ListenPort    int     `yaml:"listenPort,omitempty" json:"listenPort,omitempty"`
	ListenTLSPort int     `yaml:"listenTlsPort,omitempty" json:"listenTlsPort,omitempty"`
	RedirectPort  int     `yaml:"redirectPort,omitempty" json:"redirectPort,omitempty"`
	Routes        []Route `yaml:"routes" json:"routes"`
}

func defaultGatewayConfig() *GatewayConfig {
	return &GatewayConfig{
		ListenPort:    8081,
		ListenTLSPort: 8443,
		AuthURL:       "http://127.0.0.1:3005/auth/verify",
		LoginURL:      "https://login.example.com/login",
		Routes:        []Route{},
	}
}

var (
	gatewayFile   = envOr("NAVI_GATEWAY_FILE", filepath.Join(filepath.Dir(confFile), "gateway.yml"))
	gatewayOutDir = envOr("NAVI_GATEWAY_OUT", filepath.Join(filepath.Dir(confFile), "gateway"))
)

func loadGateway() (*GatewayConfig, error) {
	cfg := defaultGatewayConfig()
	data, err := os.ReadFile(gatewayFile)
	if err != nil {
		if os.IsNotExist(err) {
			return cfg, nil
		}
		return nil, err
	}
	if err := yaml.Unmarshal(data, cfg); err != nil {
		return nil, fmt.Errorf("路由表解析失败: %w", err)
	}
	if cfg.ListenPort == 0 {
		cfg.ListenPort = 8081
	}
	if cfg.ListenTLSPort == 0 {
		cfg.ListenTLSPort = 8443
	}
	if cfg.Routes == nil {
		cfg.Routes = []Route{}
	}
	return cfg, nil
}

func saveGateway(cfg *GatewayConfig) error {
	data, err := yaml.Marshal(cfg)
	if err != nil {
		return err
	}
	if err := os.MkdirAll(filepath.Dir(gatewayFile), 0o755); err != nil {
		return err
	}
	tmp := gatewayFile + ".tmp"
	if err := os.WriteFile(tmp, data, 0o600); err != nil {
		return err
	}
	return os.Rename(tmp, gatewayFile)
}

func routeKind(r Route) string {
	k := strings.ToLower(strings.TrimSpace(r.Kind))
	if k == "" {
		return "proxy"
	}
	return k
}

func ValidateRoute(r Route) error {
	host := strings.TrimSpace(r.Host)
	if host == "" {
		return fmt.Errorf("域名不能为空")
	}
	if strings.ContainsAny(host, " \t/\\?#;\"'") || strings.Contains(host, "://") {
		return fmt.Errorf("域名格式不对: %q", r.Host)
	}
	kind := routeKind(r)
	if kind != "proxy" && kind != "portal" && kind != "auth" {
		return fmt.Errorf("%s: 未知服务类型 %q", host, r.Kind)
	}
	if kind == "proxy" {
		up := strings.TrimSpace(r.Upstream)
		if up == "" {
			return fmt.Errorf("%s: 后端地址不能为空", host)
		}
		if !strings.HasPrefix(up, "http://") && !strings.HasPrefix(up, "https://") {
			return fmt.Errorf("%s: 后端必须是 http:// 或 https:// 开头", host)
		}
		if strings.ContainsAny(up, " \t\"'") {
			return fmt.Errorf("%s: 后端地址含非法字符", host)
		}
	}
	if r.MaxBodyMB < 0 {
		return fmt.Errorf("%s: 上传上限不能为负", host)
	}
	for _, p := range r.BypassPaths {
		if !strings.HasPrefix(p, "/") || strings.ContainsAny(p, " \t\"';{}") {
			return fmt.Errorf("%s: 免认证路径格式不对: %q", host, p)
		}
	}
	if r.NavEnabled {
		if strings.TrimSpace(r.NavName) == "" {
			return fmt.Errorf("%s: 已加入导航但名称为空", host)
		}
		if strings.TrimSpace(r.NavSection) == "" {
			return fmt.Errorf("%s: 已加入导航但未选择分组", host)
		}
		if isHistorySectionName(r.NavSection) {
			return fmt.Errorf("%s: 历史访问是系统分组，不能放手工导航", host)
		}
	}
	return nil
}

func isHistorySectionName(name string) bool {
	n := strings.ToLower(strings.TrimSpace(name))
	return n == "历史访问" || n == "history" || n == "recent"
}

func nginxQuote(s string) string {
	return "'" + strings.ReplaceAll(s, "'", "") + "'"
}

func writeTLS(b *strings.Builder, cfg *GatewayConfig) {
	fmt.Fprintf(b, "    ssl_certificate %s;\n    ssl_certificate_key %s;\n", nginxQuote(cfg.CertFile), nginxQuote(cfg.KeyFile))
	b.WriteString("    ssl_protocols TLSv1.2 TLSv1.3;\n")
}

func writeListeners(b *strings.Builder, cfg *GatewayConfig, defaultServer bool) {
	suffix := ""
	if defaultServer {
		suffix = " default_server"
	}
	if cfg.ListenHTTPS {
		// 注意：http2 只能作为 listen 的参数写。容器里是 nginx 1.22，
		// 独立的 `http2 on;` 会直接报 unknown directive（本轮实测踩到）。
		fmt.Fprintf(b, "    listen %d ssl http2%s;\n", cfg.ListenPort, suffix)
		if cfg.ListenTLSPort > 0 && cfg.ListenTLSPort != cfg.ListenPort {
			fmt.Fprintf(b, "    listen %d ssl http2%s;\n", cfg.ListenTLSPort, suffix)
		}
		return
	}
	fmt.Fprintf(b, "    listen %d%s;\n", cfg.ListenPort, suffix)
}

func writeErrorPages(b *strings.Builder, include404 bool) {
	b.WriteString("    root /app/portal;\n")
	// 关键：错误页与它自己的静态资源必须 `auth_request off`。
	// 上游故障时 nginx 会内部跳转到 /500.html，而服务端的 auth_request 会被
	// 这个内部请求继承 —— 于是"上游 502"最终以 401（认证失败）呈现给用户，
	// 自定义错误页永远显示不出来。本轮实测踩到（日志里能看到 connect() refused，
	// 客户端却收到 nginx 的默认 401 页）。
	if include404 {
		b.WriteString("    error_page 404 /404.html;\n")
		b.WriteString("    location = /404.html { internal; auth_request off; }\n")
	}
	b.WriteString("    error_page 500 502 503 504 /500.html;\n")
	b.WriteString("    location = /500.html { internal; auth_request off; }\n")
	b.WriteString("    location ^~ /css/ { auth_request off; try_files $uri =404; }\n")
	b.WriteString("    location = /favicon.svg { auth_request off; try_files $uri =404; }\n")
	b.WriteString("    location = /favicon.ico { auth_request off; try_files $uri =404; }\n")
}

func writeProxyLocation(b *strings.Builder, r Route, path string, authOff bool) {
	if path == "" {
		b.WriteString("    location / {\n")
	} else {
		fmt.Fprintf(b, "    location ^~ %s {\n", path)
	}
	if authOff {
		b.WriteString("        auth_request off;\n")
	}
	fmt.Fprintf(b, "        proxy_pass %s;\n", strings.TrimSpace(r.Upstream))
	b.WriteString("        proxy_http_version 1.1;\n")
	b.WriteString("        proxy_set_header Host $host;\n")
	b.WriteString("        proxy_set_header X-Real-IP $remote_addr;\n")
	b.WriteString("        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;\n")
	b.WriteString("        proxy_set_header X-Forwarded-Proto $scheme;\n")
	if r.Websocket {
		b.WriteString("        proxy_set_header Upgrade $http_upgrade;\n")
		b.WriteString("        proxy_set_header Connection \"upgrade\";\n")
	}
	if r.Streaming {
		b.WriteString("        postpone_output 0;\n        tcp_nopush off;\n        tcp_nodelay on;\n")
		b.WriteString("        sendfile off;\n        proxy_buffering off;\n        proxy_request_buffering off;\n")
		b.WriteString("        gzip off;\n        chunked_transfer_encoding on;\n")
	}
	b.WriteString("        proxy_read_timeout 86400s;\n        proxy_send_timeout 86400s;\n")
	if r.InsecureTLS || strings.HasPrefix(strings.ToLower(r.Upstream), "https://") {
		b.WriteString("        proxy_ssl_verify off;\n")
	}
	if r.InjectBeian {
		b.WriteString("        sub_filter '</footer>' '</footer><div class=\"navi-proxy-beian\"><a href=\"https://beian.miit.gov.cn\" target=\"_blank\">京ICP备00000000号-1</a> | <a href=\"https://beian.mps.gov.cn\" target=\"_blank\">京公网安备00000000000000号</a></div>';\n")
		b.WriteString("        sub_filter_once off;\n")
		b.WriteString("        proxy_set_header Accept-Encoding \"\";\n")
	}
	b.WriteString("        proxy_redirect off;\n    }\n")
}

func writeRouteServer(b *strings.Builder, cfg *GatewayConfig, r Route) error {
	host := strings.TrimSpace(r.Host)
	b.WriteString("server {\n")
	writeListeners(b, cfg, false)
	fmt.Fprintf(b, "    server_name %s;\n", host)
	if cfg.ListenHTTPS {
		writeTLS(b, cfg)
	}
	if r.MaxBodyMB > 0 {
		fmt.Fprintf(b, "    client_max_body_size %dm;\n", r.MaxBodyMB)
	}
	writeErrorPages(b, routeKind(r) == "portal")

	if routeKind(r) == "portal" {
		b.WriteString("    index index.html;\n    location / { try_files $uri $uri/ /404.html; }\n}\n\n")
		return nil
	}
	if routeKind(r) == "auth" {
		// 登录域名由容器内自带的登录服务直接响应，替代原先的 portal-auth 容器
		r.Upstream = "http://127.0.0.1:3005"
		r.RequireLogin = false
	}
	if r.RequireLogin {
		if strings.TrimSpace(cfg.AuthURL) == "" || strings.TrimSpace(cfg.LoginURL) == "" {
			return fmt.Errorf("%s: 需要认证但未配置认证/登录地址", host)
		}
		fmt.Fprintf(b, "    location = /_auth { internal; proxy_pass %s; proxy_pass_request_body off;\n", cfg.AuthURL)
		b.WriteString("        proxy_set_header Content-Length \"\";\n")
		b.WriteString("        proxy_set_header Cookie $http_cookie;\n")
		b.WriteString("        proxy_set_header X-Original-URI $request_uri;\n    }\n")
		b.WriteString("    auth_request /_auth;\n    error_page 401 = @login;\n")
		fmt.Fprintf(b, "    location @login { return 302 %s?redirect=$scheme://$host$request_uri; }\n", cfg.LoginURL)
	}
	for _, p := range r.BypassPaths {
		writeProxyLocation(b, r, p, true)
	}
	writeProxyLocation(b, r, "", false)
	b.WriteString("}\n\n")
	return nil
}

// RenderGatewayConf 生成完整统一入口配置。未知域名使用内置自定义 404 页面，
// 反向代理故障使用自定义 500 页面；不会再返回一行纯文本。
func RenderGatewayConf(cfg *GatewayConfig) (string, error) {
	if cfg == nil {
		return "", fmt.Errorf("配置为空")
	}
	if cfg.ListenPort == 0 {
		cfg.ListenPort = 8081
	}
	if cfg.ListenHTTPS && (cfg.CertFile == "" || cfg.KeyFile == "") {
		return "", fmt.Errorf("启用 HTTPS 但未配置证书路径")
	}
	hosts := make(map[string]bool, len(cfg.Routes))
	for _, r := range cfg.Routes {
		if err := ValidateRoute(r); err != nil {
			return "", err
		}
		h := strings.ToLower(strings.TrimSpace(r.Host))
		if hosts[h] {
			return "", fmt.Errorf("域名重复: %s", h)
		}
		hosts[h] = true
	}

	routes := append([]Route(nil), cfg.Routes...)
	sort.SliceStable(routes, func(i, j int) bool { return routes[i].Host < routes[j].Host })
	var b strings.Builder
	b.WriteString("# 由 HomeDash 后台生成，请勿手改。源: " + gatewayFile + "\n\n")

	if cfg.ListenHTTPS && cfg.RedirectPort > 0 {
		fmt.Fprintf(&b, "server {\n    listen %d default_server;\n    server_name _;\n    return 302 https://$host$request_uri;\n}\n\n", cfg.RedirectPort)
	}

	// 默认服务器：保留原统一代理的自定义错误页设计。
	b.WriteString("server {\n")
	writeListeners(&b, cfg, true)
	b.WriteString("    server_name _;\n")
	if cfg.ListenHTTPS {
		writeTLS(&b, cfg)
	}
	writeErrorPages(&b, true)
	b.WriteString("    location / { return 404; }\n}\n\n")

	for _, r := range routes {
		if err := writeRouteServer(&b, cfg, r); err != nil {
			return "", err
		}
	}
	return b.String(), nil
}

func gatewayFileFor() string {
	return filepath.Join(gatewayOutDir, "gateway.conf")
}