// 读者登录与评论的公开接口。登录走 GitHub OAuth 整页跳转；
// 会话是 httpOnly cookie（one_reader），与后台会话（one_session）互不相通。
//
// 审核：设置里开了「先审后显」时，新评论 status=pending——
// 只有作者自己能在列表里看到（带「审核中」角标），站主通过后才公开。
package api

import (
	"crypto/rand"
	"encoding/hex"
	"errors"
	"net/http"
	"net/url"
	"strconv"
	"strings"
	"time"

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

const (
	readerCookie   = "one_reader"
	oauthStateCook = "one_oauth_state"
	oauthBackCook  = "one_oauth_back"
	maxCommentLen  = 500
	editWindow     = 10 * time.Minute
)

// readerID 从会话 cookie 解出读者 ID；匿名返回 false。
// 后台管理员已登录（one_session）时直接映射为站主读者身份——
// 站主发评论不必再走一遍 GitHub 登录。
func (a *API) readerID(r *http.Request) (int64, bool) {
	rd, ok, err := a.resolveReader(r)
	if err != nil || !ok {
		return 0, false
	}
	return rd.ID, true
}

// resolveReader 解出当前访客的读者身份：读者会话优先，
// 其次是后台管理员会话（自动 upsert 一个 provider=admin 的站主读者）。
func (a *API) resolveReader(r *http.Request) (model.Reader, bool, error) {
	if ck, err := r.Cookie(auth.ReaderCookie); err == nil && ck.Value != "" {
		if id, verr := a.ReaderSessions.Verify(ck.Value); verr == nil {
			rd, gerr := a.Store.GetReader(id)
			if gerr == nil {
				return rd, true, nil
			}
		}
	}
	if a.AdminSessions != nil {
		if ck, err := r.Cookie("one_session"); err == nil && ck.Value != "" {
			if _, verr := a.AdminSessions.Verify(ck.Value); verr == nil {
				rd, oerr := a.ownerReader()
				if oerr == nil {
					return rd, true, nil
				}
			}
		}
	}
	return model.Reader{}, false, nil
}

// ownerReader 取（或创建）站主评论身份：provider=admin，名字用站点作者名。
func (a *API) ownerReader() (model.Reader, error) {
	name := "站主"
	if st, err := a.Store.GetSettings(); err == nil && st.AuthorName != "" {
		name = st.AuthorName
	}
	return a.Store.UpsertReader(model.Reader{
		Provider: "admin", Handle: a.Cfg.AdminUser, Name: name,
	})
}

func (a *API) authMe(w http.ResponseWriter, r *http.Request) {
	var user any // 匿名时 {user: null}，前端判空即「未登录」
	if reader, ok, err := a.resolveReader(r); err == nil && ok {
		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.Provider == "admin", "banned": reader.Banned,
		}
	}
	httpx.OK(w, map[string]any{"user": user})
}

func (a *API) authLogout(w http.ResponseWriter, r *http.Request) {
	http.SetCookie(w, &http.Cookie{Name: auth.ReaderCookie, Value: "", Path: "/", MaxAge: -1})
	httpx.OK(w, map[string]any{"ok": true})
}

// githubLogin 跳转 GitHub 授权页。state 防 CSRF 存短命 cookie；
// 授权完成回到 callback 后必须带上同一个值。
// 同时把发起登录的前台 origin 记下来（one_oauth_back），
// callback 用它跳回去——开发时前端 3000 / 后端 8080 分离才不会落错站。
func (a *API) githubLogin(w http.ResponseWriter, r *http.Request) {
	if !a.GH.Enabled() {
		httpx.NotFound(w)
		return
	}
	state := randHex(16)
	http.SetCookie(w, &http.Cookie{Name: oauthStateCook, Value: state, Path: "/",
		HttpOnly: true, MaxAge: 600})
	if ref := r.Referer(); ref != "" {
		if u, err := url.Parse(ref); err == nil && u.Scheme != "" && u.Host != "" {
			http.SetCookie(w, &http.Cookie{Name: oauthBackCook,
				Value: u.Scheme + "://" + u.Host, Path: "/", HttpOnly: true, MaxAge: 600})
		}
	}
	http.Redirect(w, r, a.GH.LoginURL(a.Cfg.SiteURL+"/api/auth/callback/github", state), http.StatusFound)
}

// githubCallback 用 code 换身份：GitHub 用户 → upsert 读者 → 发会话 →
// 回到首页。
func (a *API) githubCallback(w http.ResponseWriter, r *http.Request) {
	if !a.GH.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
	}
	gh, err := a.GH.Exchange(r.Context(), r.FormValue("code"), a.Cfg.SiteURL+"/api/auth/callback/github")
	if err != nil {
		a.authFails.Add(ip)
		httpx.ServerError(w, err)
		return
	}
	u, err := a.GH.FetchUser(r.Context(), gh)
	if err != nil {
		a.authFails.Add(ip)
		httpx.ServerError(w, err)
		return
	}
	name := u.Name
	if name == "" {
		name = u.Login
	}
	reader, err := a.Store.UpsertReader(model.Reader{
		Provider: "github", Handle: u.Login, Name: name,
		AvatarURL: u.AvatarURL, URL: u.HTMLURL,
	})
	if err != nil {
		httpx.ServerError(w, err)
		return
	}
	http.Redirect(w, r, a.issueReaderCookie(w, r, reader.ID), http.StatusFound)
}

func randHex(n int) string {
	b := make([]byte, n)
	_, _ = rand.Read(b)
	return hex.EncodeToString(b)
}

// ---------- comments（评论的读取与发表） ----------

func (a *API) comments(w http.ResponseWriter, r *http.Request) {
	switch r.Method {
	case http.MethodGet:
		a.listComments(w, r)
	case http.MethodPost:
		a.createComment(w, r)
	default:
		httpx.Error(w, http.StatusMethodNotAllowed, "GET/POST required")
	}
}

func (a *API) listComments(w http.ResponseWriter, r *http.Request) {
	postID := httpx.QueryInt(r, "post_id", 0)
	if postID <= 0 {
		httpx.BadRequest(w, "post_id required")
		return
	}
	viewer, _ := a.readerID(r)
	newest := httpx.QueryString(r, "sort") == "newest"
	roots, err := a.Store.ListCommentsByPost(int64(postID), viewer, newest)
	if err != nil {
		httpx.ServerError(w, err)
		return
	}
	httpx.OK(w, map[string]any{
		"items": roots, "total": len(roots),
		"page": 1, "size": len(roots),
	})
}

// createComment 发表评论（含回复）。登录 + 未禁言 + 评论开关开着；
// 审核开关开着时新评论进「待审」。站主身份（管理员会话）不受禁言与审核约束。
func (a *API) createComment(w http.ResponseWriter, r *http.Request) {
	reader, ok, err := a.resolveReader(r)
	if err != nil {
		httpx.Error(w, http.StatusUnauthorized, "登录已过期，刷新页面重新登录")
		return
	}
	if !ok {
		httpx.Error(w, http.StatusUnauthorized, "登录后才能评论")
		return
	}
	isOwner := reader.Provider == "admin"
	if reader.Banned && !isOwner {
		httpx.Error(w, http.StatusForbidden, "你已被禁言，暂时无法评论")
		return
	}
	// 写入限速：每读者每分钟最多 maxComments 条（站主豁免，批量回复不该被卡）
	var rateKey string
	if !isOwner {
		rateKey = strconv.FormatInt(reader.ID, 10)
		if a.commentNew.Blocked(rateKey) {
			httpx.Error(w, http.StatusTooManyRequests, "发得太快了，休息一分钟再试")
			return
		}
	}
	st, err := a.Store.GetSettings()
	if err != nil {
		httpx.ServerError(w, err)
		return
	}
	if !st.CommentsEnabled {
		httpx.Error(w, http.StatusForbidden, "评论未开放")
		return
	}
	var in struct {
		PostID   int64  `json:"post_id"`
		ParentID int64  `json:"parent_id"`
		BodyMd   string `json:"body_md"`
	}
	if err := httpx.Decode(r, &in); err != nil {
		httpx.BadRequest(w, "invalid body")
		return
	}
	body := strings.TrimSpace(in.BodyMd)
	if body == "" {
		httpx.BadRequest(w, "评论内容不能为空")
		return
	}
	if len([]rune(body)) > maxCommentLen {
		httpx.BadRequest(w, "评论最多 500 字")
		return
	}
	if _, err := a.Store.Get(in.PostID); err != nil {
		httpx.BadRequest(w, "文章不存在")
		return
	}
	var parent model.Comment
	root := int64(0)
	if in.ParentID > 0 {
		p, err := a.Store.GetComment(in.ParentID)
		if err != nil {
			httpx.BadRequest(w, "回复的评论不存在")
			return
		}
		if p.PostID != in.PostID {
			httpx.BadRequest(w, "回复的评论不属于这篇文章")
			return
		}
		parent = p
		root = parent.RootID
		if root == 0 {
			root = parent.ID
		}
	}
	status := "visible"
	if st.CommentsReview && !isOwner {
		status = "pending"
	}
	c, err := a.Store.CreateComment(model.Comment{
		PostID: in.PostID, UserID: reader.ID, ParentID: in.ParentID, RootID: root,
		BodyMd: body, BodyHTML: render.Markdown(body), Status: status,
	})
	if err != nil {
		httpx.ServerError(w, err)
		return
	}
	a.Hub.Broadcast(in.PostID)
	if rateKey != "" {
		a.commentNew.Add(rateKey) // 只计成功写入：空正文这类手滑不扣配额
	}
	httpx.Created(w, c)
}

// commentSub /api/comments/{id} 与 /api/comments/{root}/thread 的分发
func (a *API) commentSub(w http.ResponseWriter, r *http.Request) {
	rest := strings.Trim(strings.TrimPrefix(r.URL.Path, "/api/comments/"), "/")
	if rest == "" {
		httpx.NotFound(w)
		return
	}
	// {root}/thread：楼内回复翻页（当前实现全量内嵌，这里兜底返回剩余）
	if strings.HasSuffix(rest, "/thread") {
		rootID, err := strconv.ParseInt(strings.TrimSuffix(rest, "/thread"), 10, 64)
		if err != nil {
			httpx.BadRequest(w, "bad root id")
			return
		}
		a.commentThread(w, r, rootID)
		return
	}
	id, err := strconv.ParseInt(rest, 10, 64)
	if err != nil {
		httpx.BadRequest(w, "bad comment id")
		return
	}
	switch r.Method {
	case http.MethodPut:
		a.editComment(w, r, id)
	case http.MethodDelete:
		a.deleteComment(w, r, id)
	default:
		httpx.Error(w, http.StatusMethodNotAllowed, "PUT/DELETE required")
	}
}

func (a *API) commentThread(w http.ResponseWriter, r *http.Request, rootID int64) {
	root, err := a.Store.GetComment(rootID)
	if err != nil {
		httpx.ServerError(w, err)
		return
	}
	cursor := httpx.QueryInt(r, "cursor", 0)
	items := []model.Comment{}
	if cursor >= 0 && cursor < len(root.Replies) {
		items = root.Replies[cursor:]
	}
	httpx.OK(w, map[string]any{"items": items, "cursor": "", "reply_count": root.ReplyCount})
}

// editComment 作者改自己的评论：10 分钟内有效，且未被禁言未删除
func (a *API) editComment(w http.ResponseWriter, r *http.Request, id int64) {
	readerID, ok := a.readerID(r)
	if !ok {
		httpx.Error(w, http.StatusUnauthorized, "登录已过期")
		return
	}
	c, err := a.Store.GetComment(id)
	if errors.Is(err, store.ErrNotFound) {
		httpx.NotFound(w)
		return
	}
	if err != nil {
		httpx.ServerError(w, err)
		return
	}
	if c.UserID != readerID {
		httpx.Error(w, http.StatusForbidden, "只能编辑自己的评论")
		return
	}
	if c.IsDeleted {
		httpx.NotFound(w)
		return
	}
	if time.Since(mustParse(c.CreatedAt)) > editWindow {
		httpx.Error(w, http.StatusForbidden, "超过可编辑时间")
		return
	}
	var in struct {
		BodyMd string `json:"body_md"`
	}
	if err := httpx.Decode(r, &in); err != nil {
		httpx.BadRequest(w, "invalid body")
		return
	}
	body := strings.TrimSpace(in.BodyMd)
	if body == "" {
		httpx.BadRequest(w, "评论内容不能为空")
		return
	}
	if len([]rune(body)) > maxCommentLen {
		httpx.BadRequest(w, "评论最多 500 字")
		return
	}
	if err := a.Store.UpdateCommentBody(id, body, render.Markdown(body)); err != nil {
		httpx.ServerError(w, err)
		return
	}
	updated, err := a.Store.GetComment(id)
	if err != nil {
		httpx.ServerError(w, err)
		return
	}
	a.Hub.Broadcast(updated.PostID)
	httpx.OK(w, updated)
}

// deleteComment 作者软删自己的评论（留壳保楼层）
func (a *API) deleteComment(w http.ResponseWriter, r *http.Request, id int64) {
	readerID, ok := a.readerID(r)
	if !ok {
		httpx.Error(w, http.StatusUnauthorized, "登录已过期")
		return
	}
	c, err := a.Store.GetComment(id)
	if errors.Is(err, store.ErrNotFound) {
		httpx.NotFound(w)
		return
	}
	if err != nil {
		httpx.ServerError(w, err)
		return
	}
	if c.UserID != readerID {
		httpx.Error(w, http.StatusForbidden, "只能删除自己的评论")
		return
	}
	if err := a.Store.DeleteComment(id); err != nil {
		httpx.ServerError(w, err)
		return
	}
	a.Hub.Broadcast(c.PostID)
	httpx.OK(w, map[string]any{"ok": true})
}

func mustParse(s string) time.Time {
	t, err := time.Parse(time.RFC3339, s)
	if err != nil {
		return time.Time{}
	}
	return t
}