// Package auth 统一认证中心（UAC）控制器：api.yunzer.cn/auth
//
// 实现 OIDC 1.0（基于 OAuth 2.1 + PKCE）标准端点，
// 以后每开发一个新软件，只需在 yz_auth_client 注册一条即可接入。
package auth

import (
	"crypto/rand"
	"crypto/sha256"
	"encoding/base64"
	"encoding/json"
	"fmt"
	"strings"
	"time"

	authsvc "server/services/auth"

	"server/models"
	"server/pkg/jwtutil"

	beego "github.com/beego/beego/v2/server/web"
)

// 认证中心会话 Cookie（仅作用于认证中心域名，用于 authorize 阶段识别登录态）
const (
	sessionCookieName = "yz_sid"
	sessionCookieTTL  = 7200
)

// grant_type 常量
const (
	GrantAuthCode    = "authorization_code"
	GrantRefresh     = "refresh_token"
	ResponseTypeCode = "code"
)

// AuthOidcController OIDC 标准端点
type AuthOidcController struct {
	beego.Controller
}

func (c *AuthOidcController) serveJSON(data map[string]interface{}) {
	c.Data["json"] = data
	_ = c.ServeJSON()
}

func (c *AuthOidcController) fail(status int, msg string) {
	c.Ctx.Output.SetStatus(status)
	c.serveJSON(map[string]interface{}{"error": msg})
}

// Discovery OIDC 发现文档
// GET /auth/.well-known/openid-configuration
func (c *AuthOidcController) Discovery() {
	issuer := jwtutil.Issuer()
	if issuer == "" {
		issuer = fmt.Sprintf("https://%s/auth", c.Ctx.Request.Host)
	}
	c.Data["json"] = map[string]interface{}{
		"issuer":                                issuer,
		"authorization_endpoint":                issuer + "/authorize",
		"token_endpoint":                        issuer + "/token",
		"userinfo_endpoint":                     issuer + "/userinfo",
		"introspection_endpoint":                issuer + "/introspect",
		"revocation_endpoint":                   issuer + "/revoke",
		"end_session_endpoint":                  issuer + "/logout",
		"jwks_uri":                              issuer + "/jwks.json",
		"response_types_supported":              []string{"code"},
		"grant_types_supported":                 []string{GrantAuthCode, GrantRefresh},
		"subject_types_supported":               []string{"public"},
		"id_token_signing_alg_values_supported": []string{jwtutil.AlgRS256, jwtutil.AlgHS256},
		"code_challenge_methods_supported":      []string{"S256"},
		"scopes_supported":                      []string{"openid", "profile", "tenant"},
	}
	_ = c.ServeJSON()
}

// JWKS 公钥集合（各应用本地验签用）
// GET /auth/jwks.json
func (c *AuthOidcController) JWKS() {
	keys := jwtutil.JWKS()
	if keys == nil {
		keys = []jwtutil.JWK{}
	}
	c.Data["json"] = map[string]interface{}{"keys": keys}
	_ = c.ServeJSON()
}

// Authorize 授权端点
// GET /auth/authorize?client_id=&redirect_uri=&response_type=code&scope=&state=&code_challenge=&code_challenge_method=S256
//
// 未登录时重定向到统一登录页，登录后再回到本端点完成授权。
func (c *AuthOidcController) Authorize() {
	clientID := strings.TrimSpace(c.GetString("client_id"))
	redirectURI := strings.TrimSpace(c.GetString("redirect_uri"))
	responseType := strings.TrimSpace(c.GetString("response_type"))
	state := c.GetString("state")
	scope := c.GetString("scope")
	if scope == "" {
		scope = "openid"
	}
	challenge := c.GetString("code_challenge")
	challengeMethod := c.GetString("code_challenge_method")
	if challengeMethod == "" {
		challengeMethod = "S256"
	}
	nonce := c.GetString("nonce")

	if clientID == "" || redirectURI == "" {
		c.Ctx.Output.SetStatus(400)
		_, _ = c.Ctx.ResponseWriter.Write([]byte("缺少 client_id 或 redirect_uri"))
		return
	}
	if responseType != ResponseTypeCode {
		c.Ctx.Output.SetStatus(400)
		_, _ = c.Ctx.ResponseWriter.Write([]byte("仅支持 response_type=code"))
		return
	}

	client, err := findClient(clientID)
	if err != nil {
		c.Ctx.Output.SetStatus(400)
		_, _ = c.Ctx.ResponseWriter.Write([]byte("client_id 无效"))
		return
	}
	if !allowRedirect(client, redirectURI) {
		c.Ctx.Output.SetStatus(400)
		_, _ = c.Ctx.ResponseWriter.Write([]byte("redirect_uri 未登记"))
		return
	}

	// 登录态：Cookie 优先（浏览器跳转），其次 Authorization（服务端调用）
	sid := strings.TrimSpace(c.Ctx.GetCookie(sessionCookieName))
	if sid == "" {
		if claims := claimsFromHeader(c); claims != nil {
			sid = claims.Sid
		}
	}
	if sid == "" {
		// 未登录 → 去登录页，登录后带着参数回来
		back := fmt.Sprintf("%s?%s", authorizePath(c), c.Ctx.Request.URL.RawQuery)
		target := fmt.Sprintf("/auth/login?redirect=%s&client_id=%s",
			base64.RawURLEncoding.EncodeToString([]byte(back)), clientID)
		c.Redirect(target, 302)
		return
	}

	session, err := authsvc.GetSession(sid)
	if err != nil {
		clearSessionCookie(c)
		back := fmt.Sprintf("%s?%s", authorizePath(c), c.Ctx.Request.URL.RawQuery)
		target := fmt.Sprintf("/auth/login?redirect=%s&client_id=%s",
			base64.RawURLEncoding.EncodeToString([]byte(back)), clientID)
		c.Redirect(target, 302)
		return
	}

	// 已登录但未选择企业：跳登录页的企业选择步骤
	if session.Tid == authsvc.PendingTenantID {
		back := fmt.Sprintf("%s?%s", authorizePath(c), c.Ctx.Request.URL.RawQuery)
		target := fmt.Sprintf("/auth/login?step=tenant&redirect=%s&client_id=%s",
			base64.RawURLEncoding.EncodeToString([]byte(back)), clientID)
		c.Redirect(target, 302)
		return
	}

	code, err := issueAuthCode(client.ClientID, session.IdentityID, session.Tid, redirectURI, challenge, challengeMethod, scope, nonce)
	if err != nil {
		c.Ctx.Output.SetStatus(500)
		_, _ = c.Ctx.ResponseWriter.Write([]byte("签发授权码失败"))
		return
	}

	sep := "?"
	if strings.Contains(redirectURI, "?") {
		sep = "&"
	}
	c.Redirect(fmt.Sprintf("%s%scode=%s&state=%s", redirectURI, sep, code, state), 302)
}

// Token 令牌端点
// POST /auth/token
//   - grant_type=authorization_code：code + code_verifier（PKCE）+ client_id
//   - grant_type=refresh_token：refresh_token + client_id
func (c *AuthOidcController) Token() {
	grantType := strings.TrimSpace(c.GetString("grant_type"))
	clientID := strings.TrimSpace(c.GetString("client_id"))
	if clientID == "" {
		// 兼容表单/JSON 以外的取参方式
		clientID = strings.TrimSpace(c.Ctx.Request.FormValue("client_id"))
	}
	if grantType == "" {
		grantType = strings.TrimSpace(c.Ctx.Request.FormValue("grant_type"))
	}

	switch grantType {
	case GrantAuthCode:
		code := strings.TrimSpace(c.GetString("code"))
		verifier := strings.TrimSpace(c.GetString("code_verifier"))
		if code == "" || verifier == "" || clientID == "" {
			c.fail(400, "invalid_request")
			return
		}
		pair, claims, err := exchangeCode(code, verifier, clientID)
		if err != nil {
			c.fail(400, err.Error())
			return
		}
		idToken, _ := buildIDToken(claims, clientID)
		c.serveJSON(map[string]interface{}{
			"access_token":  pair.AccessToken,
			"refresh_token": pair.RefreshToken,
			"token_type":    pair.TokenType,
			"expires_in":    pair.ExpiresIn,
			"id_token":      idToken,
			"sid":           pair.Sid,
		})
	case GrantRefresh:
		refresh := strings.TrimSpace(c.GetString("refresh_token"))
		if refresh == "" || clientID == "" {
			c.fail(400, "invalid_request")
			return
		}
		pair, err := authsvc.RefreshTokens(refresh, clientID)
		if err != nil {
			c.fail(400, err.Error())
			return
		}
		c.serveJSON(map[string]interface{}{
			"access_token":  pair.AccessToken,
			"refresh_token": pair.RefreshToken,
			"token_type":    pair.TokenType,
			"expires_in":    pair.ExpiresIn,
			"sid":           pair.Sid,
		})
	default:
		c.fail(400, "unsupported_grant_type")
	}
}

// UserInfo 用户信息端点，需 Bearer Token
// GET /auth/userinfo
func (c *AuthOidcController) UserInfo() {
	claims := claimsFromHeader(c)
	if claims == nil {
		c.Ctx.Output.SetStatus(401)
		c.serveJSON(map[string]interface{}{"error": "invalid_token"})
		return
	}
	if claims.UserID <= 0 {
		c.fail(401, "invalid_token")
		return
	}
	var identity models.AuthIdentity
	if err := models.Orm.QueryTable(new(models.AuthIdentity)).
		Filter("id", claims.UserID).One(&identity); err != nil {
		c.fail(401, "invalid_token")
		return
	}
	profile, err := authsvc.BuildProfile(&identity)
	if err != nil {
		c.fail(500, "server_error")
		return
	}
	c.serveJSON(map[string]interface{}{
		"sub":       fmt.Sprintf("%d", identity.ID),
		"union_id":  identity.UnionID,
		"tid":       claims.TenantId,
		"nickname":  profile.Nickname,
		"mobile":    profile.Mobile,
		"email":     profile.Email,
		"avatar":    profile.Avatar,
		"tenants":   profile.Tenants,
		"client_id": claims.ClientID,
	})
}

// Introspect 令牌校验，供资源服务（各业务后端）调用
// POST /auth/token 之外的独立端点；比本地 JWKS 验签更实时（可查黑名单）
func (c *AuthOidcController) Introspect() {
	token := strings.TrimSpace(c.GetString("token"))
	if token == "" {
		token = strings.TrimSpace(c.Ctx.Request.FormValue("token"))
	}
	if token == "" {
		c.fail(400, "invalid_request")
		return
	}
	claims, err := jwtutil.ParseToken(token)
	if err != nil {
		c.serveJSON(map[string]interface{}{"active": false})
		return
	}
	if authsvc.IsBlacklisted(claims.ID) {
		c.serveJSON(map[string]interface{}{"active": false})
		return
	}
	c.serveJSON(map[string]interface{}{
		"active":    true,
		"sub":       claims.Subject,
		"user_id":   claims.UserID,
		"tid":       claims.TenantId,
		"client_id": claims.ClientID,
		"sid":       claims.Sid,
		"scope":     claims.Scope,
		"amr":       claims.Amr,
		"exp":       claims.ExpiresAt.Unix(),
	})
}

// Revoke 吊销令牌（登出/踢下线）
// POST /auth/revoke
func (c *AuthOidcController) Revoke() {
	token := strings.TrimSpace(c.GetString("token"))
	refresh := strings.TrimSpace(c.GetString("refresh_token"))
	if token == "" {
		token = strings.TrimSpace(c.Ctx.Request.FormValue("token"))
	}
	if token == "" && refresh == "" {
		c.fail(400, "invalid_request")
		return
	}
	_ = authsvc.RevokeTokenPair(refresh, token, models.RevokeReasonLogout)
	c.serveJSON(map[string]interface{}{"code": 200, "msg": "已吊销"})
}

// ---------------------------------------------------------------- 内部工具

func authorizePath(c *AuthOidcController) string {
	return "/auth/authorize"
}

// clearSessionCookie 清除认证中心会话 Cookie
func clearSessionCookie(c *AuthOidcController) {
	c.Ctx.Output.Header("Set-Cookie",
		fmt.Sprintf("%s=; Path=/; Max-Age=0; HttpOnly; Secure; SameSite=Lax", sessionCookieName))
}

// setSessionCookie 写入认证中心会话 Cookie
func setSessionCookie(c *AuthOidcController, sid string) {
	c.Ctx.Output.Header("Set-Cookie",
		fmt.Sprintf("%s=%s; Path=/; Max-Age=%d; HttpOnly; Secure; SameSite=Lax",
			sessionCookieName, sid, sessionCookieTTL))
}

func bearerToken(c *AuthOidcController) string {
	header := c.Ctx.Request.Header.Get("Authorization")
	if header == "" {
		return ""
	}
	parts := strings.SplitN(header, " ", 2)
	if len(parts) != 2 || parts[0] != "Bearer" {
		return ""
	}
	return strings.TrimSpace(parts[1])
}

func claimsFromHeader(c *AuthOidcController) *jwtutil.Claims {
	token := bearerToken(c)
	if token == "" {
		return nil
	}
	claims, err := jwtutil.ParseToken(token)
	if err != nil {
		return nil
	}
	return claims
}

// findClient 查询启用状态的应用
func findClient(clientID string) (*models.AuthClient, error) {
	var client models.AuthClient
	err := models.Orm.QueryTable(new(models.AuthClient)).
		Filter("client_id", clientID).
		Filter("status", 1).
		One(&client)
	if err != nil {
		return nil, err
	}
	return &client, nil
}

// allowRedirect 校验回跳地址是否在白名单内（精确匹配，防钓鱼）
func allowRedirect(client *models.AuthClient, uri string) bool {
	if client.RedirectURIs == nil || *client.RedirectURIs == "" {
		return false
	}
	var list []string
	if err := json.Unmarshal([]byte(*client.RedirectURIs), &list); err != nil {
		return false
	}
	for _, item := range list {
		if strings.TrimSpace(item) == strings.TrimSpace(uri) {
			return true
		}
	}
	return false
}

// issueAuthCode 生成一次性授权码（明文返回，库中只存哈希）
func issueAuthCode(clientID string, identityID, tid uint64, redirectURI, challenge, method, scope, nonce string) (string, error) {
	plain, err := randomString(32)
	if err != nil {
		return "", err
	}
	sum := sha256.Sum256([]byte(plain))
	code := &models.AuthCode{
		CodeHash:            fmt.Sprintf("%x", sum[:]),
		ClientID:            clientID,
		IdentityID:          identityID,
		Tid:                 tid,
		RedirectURI:         redirectURI,
		CodeChallenge:       challenge,
		CodeChallengeMethod: method,
		ExpiresAt:           time.Now().Add(60 * time.Second),
	}
	if scope != "" {
		code.Scope = &scope
	}
	if nonce != "" {
		code.Nonce = &nonce
	}
	if _, err := models.Orm.Insert(code); err != nil {
		return "", err
	}
	return plain, nil
}

// exchangeCode 用授权码换令牌（校验 PKCE、一次性、有效期）
func exchangeCode(code, verifier, clientID string) (*authsvc.TokenPair, *jwtutil.Claims, error) {
	sum := sha256.Sum256([]byte(code))
	var stored models.AuthCode
	if err := models.Orm.QueryTable(new(models.AuthCode)).
		Filter("code_hash", fmt.Sprintf("%x", sum[:])).One(&stored); err != nil {
		return nil, nil, fmt.Errorf("invalid_grant")
	}
	if stored.Used != 0 || stored.ExpiresAt.Before(time.Now()) {
		return nil, nil, fmt.Errorf("invalid_grant")
	}
	if stored.ClientID != clientID {
		return nil, nil, fmt.Errorf("invalid_client")
	}
	if !verifyPKCE(verifier, stored.CodeChallenge, stored.CodeChallengeMethod) {
		return nil, nil, fmt.Errorf("invalid_grant")
	}
	// 一次性：立即标记已用
	_, _ = models.Orm.QueryTable(new(models.AuthCode)).
		Filter("code_hash", stored.CodeHash).
		Update(map[string]interface{}{"used": 1})

	session, err := authsvc.CreateSession(authsvc.SessionInfo{
		IdentityID: stored.IdentityID,
		Tid:        stored.Tid,
		ClientID:   clientID,
		LoginType:  authsvc.LoginTypePassword,
		Amr:        authsvc.AmrPwd,
	})
	if err != nil {
		return nil, nil, err
	}

	client, err := findClient(clientID)
	accessTTL := 1800
	refreshTTL := 2592000
	if err == nil {
		accessTTL = client.AccessTTL
		refreshTTL = client.RefreshTTL
	}

	pair, err := authsvc.IssueTokens(authsvc.TokenIssue{
		IdentityID: stored.IdentityID,
		Tid:        stored.Tid,
		ClientID:   clientID,
		Sid:        session.Sid,
		UserType:   "tenant",
		Amr:        authsvc.AmrPwd,
		AccessTTL:  accessTTL,
		RefreshTTL: refreshTTL,
	})
	if err != nil {
		return nil, nil, err
	}

	claims, err := jwtutil.ParseToken(pair.AccessToken)
	if err != nil {
		return nil, nil, err
	}
	return pair, claims, nil
}

// verifyPKCE 校验 PKCE（S256 或 plain）
func verifyPKCE(verifier, challenge, method string) bool {
	if challenge == "" {
		return false
	}
	if method == "S256" {
		sum := sha256.Sum256([]byte(verifier))
		return base64.RawURLEncoding.EncodeToString(sum[:]) == challenge
	}
	return verifier == challenge
}

// buildIDToken 生成 OIDC ID Token
func buildIDToken(claims *jwtutil.Claims, clientID string) (string, error) {
	return jwtutil.SignToken(jwtutil.TokenOptions{
		Alg:      jwtutil.AlgRS256,
		UserID:   claims.UserID,
		TenantID: claims.TenantId,
		UserType: claims.UserType,
		ClientID: clientID,
		Sid:      claims.Sid,
		Subject:  claims.Subject,
		Audience: []string{clientID},
		Amr:      claims.Amr,
		TTL:      time.Hour,
	})
}

// randomString 生成随机串
func randomString(n int) (string, error) {
	buf := make([]byte, n)
	if _, err := rand.Read(buf); err != nil {
		return "", err
	}
	return base64.RawURLEncoding.EncodeToString(buf), nil
}