// Google / Telegram 登录的 HTTP 端点。GitHub 的在 comments.go——
// 三个 Provider 共用同一套读者会话与 upsert 逻辑，只是凭据交换方式不同：
// GitHub / Google 是授权码换 token，Telegram 是官方 widget 直接带签名资料。
package api

import (
	"encoding/json"
	"errors"
	"io"
	"net/http"
	"strconv"

	"oneblog/internal/auth"
	"oneblog/internal/httpx"
	"oneblog/internal/model"
	"oneblog/internal/ratelimit"
	"oneblog/internal/store"
)

// authProviders 列出已配置的登录方式。
// redirect 型前端直接跳 /api/auth/{id}/login；widget 型（Telegram）
// 前端内联官方脚本，需要 bot 用户名。
func (a *API) authProviders(w http.ResponseWriter, r *http.Request) {
	providers := []map[string]any{}
	if a.GH.Enabled() {
		providers = append(providers, map[string]any{
			"id": "github", "label": "GitHub", "kind": "redirect",
		})
	}
	if a.GG.Enabled() {
		providers = append(providers, map[string]any{
			"id": "google", "label": "Google", "kind": "redirect",
		})
	}
	if a.TG.Enabled() {
		providers = append(providers, map[string]any{
			"id": "telegram", "label": "Telegram", "kind": "widget", "login": a.TG.Bot,
		})
	}
	httpx.OK(w, map[string]any{"providers": providers})
}

// googleLogin 跳 Google 授权页（state 防 CSRF 同 GitHub）
func (a *API) googleLogin(w http.ResponseWriter, r *http.Request) {
	if !a.GG.Enabled() {
		httpx.NotFound(w)
		return
	}
	a.startOAuth(w, r, func(state string) string {
		return a.GG.LoginURL(a.Cfg.SiteURL+"/api/auth/callback/google", state)
	})
}

// googleCallback 用 code 换身份，交给统一分流（绑定 / 已绑账号 / 新读者）。
func (a *API) googleCallback(w http.ResponseWriter, r *http.Request) {
	if !a.GG.Enabled() {
		httpx.NotFound(w)
		return
	}
	ip := ratelimit.SourceKey(r)
	if a.authFails.Blocked(ip) {
		httpx.Error(w, http.StatusTooManyRequests, "登录失败次数过多，请稍后再试")
		return
	}
	ck, err := r.Cookie(oauthStateCook)
	if err != nil || ck.Value == "" || ck.Value != r.FormValue("state") {
		a.authFails.Add(ip)
		httpx.BadRequest(w, "state 不匹配，请重新登录")
		return
	}
	accessToken, err := a.GG.Exchange(r.Context(), r.FormValue("code"), a.Cfg.SiteURL+"/api/auth/callback/google")
	if err != nil {
		a.authFails.Add(ip)
		httpx.ServerError(w, err)
		return
	}
	u, err := a.GG.FetchUser(r.Context(), accessToken)
	if err != nil {
		a.authFails.Add(ip)
		httpx.ServerError(w, err)
		return
	}
	// handle 优先用已验证邮箱（可读），否则退回 sub（Google 的稳定唯一 id）
	handle := u.Sub
	if u.EmailVerified && u.Email != "" {
		handle = u.Email
	}
	name := u.Name
	if name == "" {
		name = handle
	}
	persona := model.Reader{
		Provider: "google", Handle: handle, Name: name, AvatarURL: u.Picture,
	}
	if back := a.afterIdentity(w, r, "google", u.Sub, handle, persona); back != "" {
		http.Redirect(w, r, back, http.StatusFound)
	}
}

// telegramAuth 校验 Login Widget 回传的签名资料并登录。
// 前端把 widget 的 user 对象原样 POST 过来（见 reader.js 的 oneTelegramAuth）。
func (a *API) telegramAuth(w http.ResponseWriter, r *http.Request) {
	if !a.TG.Enabled() {
		httpx.NotFound(w)
		return
	}
	// widget 回传是纯表单 POST，签名可被伪造重放——失败计数最必要的一路
	ip := ratelimit.SourceKey(r)
	if a.authFails.Blocked(ip) {
		httpx.Error(w, http.StatusTooManyRequests, "登录失败次数过多，请稍后再试")
		return
	}
	// 原样读 body：验签必须用收到的全部字段（官方规则），
	// 身份字段再单独解一次
	body, err := io.ReadAll(r.Body)
	if err != nil {
		httpx.BadRequest(w, "invalid body")
		return
	}
	var fields map[string]any
	if err := json.Unmarshal(body, &fields); err != nil || len(fields) == 0 {
		a.authFails.Add(ip)
		httpx.BadRequest(w, "invalid body")
		return
	}
	if err := a.TG.VerifyMap(fields); err != nil {
		a.authFails.Add(ip)
		httpx.Error(w, http.StatusForbidden, "Telegram 登录校验失败，请重试")
		return
	}
	var in auth.TelegramUser
	if err := json.Unmarshal(body, &in); err != nil || in.IDInt() == 0 {
		httpx.BadRequest(w, "invalid body")
		return
	}
	handle := in.Username
	if handle == "" {
		// 没有公开 username 的用户用数字 id，保证 provider+handle 稳定唯一
		handle = strconv.FormatInt(in.IDInt(), 10)
	}
	externUID := strconv.FormatInt(in.IDInt(), 10)

	// Telegram 是 XHR + JSON 响应（不是整页跳转），所以这里走与 afterIdentity
	// 同语义、但自己写响应的一份分流。
	if bindRequested(r) {
		if !a.adminSessionValid(r) {
			clearBindCookie(w)
			httpx.Unauthorized(w)
			return
		}
		owner, err := a.Store.EnsureOwner(a.Cfg.AdminUser)
		if err != nil {
			clearBindCookie(w)
			httpx.ServerError(w, err)
			return
		}
		err = a.Store.BindIdentity(owner.ID, "telegram", externUID, handle)
		clearBindCookie(w)
		if errors.Is(err, store.ErrConflict) {
			httpx.Error(w, http.StatusConflict, "该账号已绑定到其他用户")
			return
		}
		if err != nil {
			httpx.ServerError(w, err)
			return
		}
		httpx.OK(w, map[string]any{"ok": true, "bound": "telegram"})
		return
	}
	clearBindCookie(w)

	// 已绑定的身份优先：站主用绑定的 Telegram 登录要拿到后台会话
	if u, err := a.Store.GetUserByIdentity("telegram", externUID); err == nil {
		if u.Role == model.RoleOwner {
			a.issueAdminSession(w, r)
			httpx.OK(w, map[string]any{"ok": true, "role": u.Role})
			return
		}
		a.issueReaderSession(w, r, u.ID)
		httpx.OK(w, map[string]any{"ok": true, "role": u.Role})
		return
	} else if !errors.Is(err, store.ErrNotFound) {
		httpx.ServerError(w, err)
		return
	}

	reader, err := a.Store.UpsertReader(model.Reader{
		Provider: "telegram", Handle: handle, Name: in.DisplayName(),
		AvatarURL: in.PhotoURL,
		URL:       tgProfileURL(in.Username),
	})
	if err != nil {
		httpx.ServerError(w, err)
		return
	}
	// 会话同样落 httpOnly cookie，前端 POST 完刷新 /api/auth/me 即可见
	a.issueReaderSession(w, r, reader.ID)
	httpx.OK(w, map[string]any{"user": map[string]any{
		"id": reader.ID, "name": reader.Name, "handle": reader.Handle,
		"avatar_url": reader.AvatarURL, "url": reader.URL,
		"provider": reader.Provider, "is_owner": reader.Role == model.RoleOwner, "banned": reader.Banned,
	}})
}

func tgProfileURL(username string) string {
	if username == "" {
		return ""
	}
	return "https://t.me/" + username
}