// Package admin serves the authenticated surface at /api/admin/*.
// It is mounted separately from the public API so the two never share a
// handler chain.
package admin

import (
	"context"
	"crypto/sha256"
	"crypto/subtle"
	"encoding/hex"
	"errors"
	"fmt"
	"io"
	"mime/multipart"
	"net/http"
	"os"
	"path/filepath"
	"strings"
	"sync"
	"time"

	"oneblog/internal/config"
	"oneblog/internal/httpx"
	"oneblog/internal/model"
	"oneblog/internal/storage"
	"oneblog/internal/store"
)

type API struct {
	Store    *store.Store
	Cfg      *config.Config
	Sessions *Sessions
	// 文件上传的存储后端与公开域名（main.go 装配，两个 API 共享同一实例）
	Blobs      storage.BlobStore
	PublicBase string

	loginOnce sync.Once
	logins    *loginLimiter
}

func NewAPI(st *store.Store, cfg *config.Config, sessions *Sessions) *API {
	a := &API{Store: st, Cfg: cfg, Sessions: sessions}
	a.limiter()
	return a
}

// limiter 惰性初始化，兼容测试里的 &API{...} 零值构造。
func (a *API) limiter() *loginLimiter {
	a.loginOnce.Do(func() {
		if a.logins == nil {
			a.logins = newLoginLimiter()
		}
	})
	return a.logins
}

const cookieName = "one_session"

func (a *API) Routes() http.Handler {
	mux := http.NewServeMux()
	mux.HandleFunc("/api/admin/login", a.login)
	mux.HandleFunc("/api/admin/logout", a.logout)
	mux.HandleFunc("/api/admin/me", a.guard(a.me))

	mux.HandleFunc("/api/admin/dashboard", a.guard(a.dashboard))
	mux.HandleFunc("/api/admin/posts", a.guard(a.listPosts))
	mux.HandleFunc("/api/admin/posts/", a.guard(a.postByID))
	mux.HandleFunc("/api/admin/tags", a.guard(a.listTags))
	mux.HandleFunc("/api/admin/tags/", a.guard(a.tagByID))
	mux.HandleFunc("/api/admin/projects", a.guard(a.listProjects))
	mux.HandleFunc("/api/admin/projects/", a.guard(a.projectByID))
	mux.HandleFunc("/api/admin/files", a.guard(a.files))
	mux.HandleFunc("/api/admin/files/", a.guard(a.fileByID))
	mux.HandleFunc("/api/admin/settings", a.guard(a.settings))
	return mux
}

// guard requires a valid session; the token may arrive as a cookie (browser)
// or as a Bearer token (CLI / API client).
func (a *API) guard(next http.HandlerFunc) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		token := bearer(r)
		if token == "" {
			if c, err := r.Cookie(cookieName); err == nil {
				token = c.Value
			}
		}
		if token == "" || !a.valid(token) {
			httpx.Unauthorized(w)
			return
		}
		next(w, r)
	}
}

func bearer(r *http.Request) string {
	h := r.Header.Get("Authorization")
	if strings.HasPrefix(strings.ToLower(h), "bearer ") {
		return strings.TrimSpace(h[7:])
	}
	return ""
}

func (a *API) valid(token string) bool {
	_, err := a.Sessions.Verify(token)
	return err == nil
}

// ---------- auth ----------

type loginRequest struct {
	Username string `json:"username"`
	Password string `json:"password"`
}

func (a *API) login(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		httpx.Error(w, http.StatusMethodNotAllowed, "POST required")
		return
	}
	key := sourceKey(r)
	if a.limiter().blocked(key) {
		httpx.Error(w, http.StatusTooManyRequests, "失败次数过多，请 10 分钟后再试")
		return
	}
	var in loginRequest
	if err := httpx.Decode(r, &in); err != nil {
		httpx.BadRequest(w, "invalid body")
		return
	}
	userOK := subtle.ConstantTimeCompare([]byte(in.Username), []byte(a.Cfg.AdminUser)) == 1
	passOK := subtle.ConstantTimeCompare([]byte(in.Password), []byte(a.Cfg.AdminPass)) == 1
	if !userOK || !passOK {
		a.limiter().fail(key)
		httpx.Unauthorized(w)
		return
	}
	a.limiter().reset(key)
	token, exp := a.Sessions.Issue(a.Cfg.AdminUser)
	http.SetCookie(w, &http.Cookie{
		Name:     cookieName,
		Value:    token,
		Path:     "/",
		HttpOnly: true,
		Secure:   isTLS(r),
		SameSite: http.SameSiteLaxMode,
		Expires:  exp,
		MaxAge:   a.Sessions.TTL(),
	})
	httpx.OK(w, map[string]any{"token": token, "expires_at": exp.UTC().Format(rfc3339)})
}

const rfc3339 = "2006-01-02T15:04:05Z07:00"

func (a *API) logout(w http.ResponseWriter, r *http.Request) {
	http.SetCookie(w, &http.Cookie{
		Name:     cookieName,
		Value:    "",
		Path:     "/",
		HttpOnly: true,
		Secure:   isTLS(r),
		SameSite: http.SameSiteLaxMode,
		MaxAge:   -1,
	})
	httpx.OK(w, map[string]any{"ok": true})
}

func (a *API) me(w http.ResponseWriter, r *http.Request) {
	httpx.OK(w, map[string]any{"user": a.Cfg.AdminUser})
}

// ---------- posts ----------

func (a *API) listPosts(w http.ResponseWriter, r *http.Request) {
	switch r.Method {
	case http.MethodGet:
		o := store.ListOptions{
			Kind:    httpx.QueryString(r, "kind"),
			Tag:     httpx.QueryString(r, "tag"),
			Query:   httpx.QueryString(r, "q"),
			Status:  httpx.QueryString(r, "status"),
			OrderBy: httpx.QueryString(r, "order"),
			Page:    httpx.QueryInt(r, "page", 1),
			Size:    httpx.QueryInt(r, "size", 20),
		}
		if o.Status == "" {
			o.Status = "any"
		}
		page, err := a.Store.List(o)
		if err != nil {
			httpx.ServerError(w, err)
			return
		}
		httpx.OK(w, page)
	case http.MethodPost:
		var in model.PostInput
		if err := httpx.Decode(r, &in); err != nil {
			httpx.BadRequest(w, "invalid body")
			return
		}
		in.Status = store.NormalizeStatus(in.Status)
		p, err := a.Store.Create(in)
		if err != nil {
			httpx.ServerError(w, err)
			return
		}
		httpx.Created(w, p)
	default:
		httpx.Error(w, http.StatusMethodNotAllowed, "GET/POST required")
	}
}

func (a *API) postByID(w http.ResponseWriter, r *http.Request) {
	rest := strings.Trim(strings.TrimPrefix(r.URL.Path, "/api/admin/posts/"), "/")
	if rest == "" {
		a.listPosts(w, r)
		return
	}
	if rest == "bulk" {
		a.bulkPosts(w, r)
		return
	}
	id, err := parseInt(rest)
	if err != nil {
		httpx.BadRequest(w, "bad post id")
		return
	}
	switch r.Method {
	case http.MethodGet:
		p, err := a.Store.Get(id)
		writeOne(w, p, err)
	case http.MethodPut, http.MethodPatch:
		var in model.PostInput
		if err := httpx.Decode(r, &in); err != nil {
			httpx.BadRequest(w, "invalid body")
			return
		}
		if in.Status != "" {
			in.Status = store.NormalizeStatus(in.Status)
		}
		p, err := a.Store.Update(id, in)
		writeOne(w, p, err)
	case http.MethodDelete:
		if err := a.Store.Delete(id); err != nil {
			if errors.Is(err, store.ErrNotFound) {
				httpx.NotFound(w)
				return
			}
			httpx.ServerError(w, err)
			return
		}
		httpx.OK(w, map[string]any{"ok": true})
	default:
		httpx.Error(w, http.StatusMethodNotAllowed, "GET/PUT/DELETE required")
	}
}

func writeOne(w http.ResponseWriter, p model.Post, err error) {
	if err != nil {
		if errors.Is(err, store.ErrNotFound) {
			httpx.NotFound(w)
			return
		}
		httpx.ServerError(w, err)
		return
	}
	httpx.OK(w, p)
}

// ---------- tags ----------

func (a *API) listTags(w http.ResponseWriter, r *http.Request) {
	switch r.Method {
	case http.MethodGet:
		tags, err := a.Store.ListTags()
		if err != nil {
			httpx.ServerError(w, err)
			return
		}
		if tags == nil {
			tags = []model.Tag{}
		}
		httpx.OK(w, map[string]any{"tags": tags})
	case http.MethodPost:
		var in struct {
			Name string `json:"name"`
		}
		if err := httpx.Decode(r, &in); err != nil {
			httpx.BadRequest(w, "invalid body")
			return
		}
		name := strings.TrimSpace(in.Name)
		if name == "" {
			httpx.BadRequest(w, "name required")
			return
		}
		t, err := a.Store.CreateTag(name)
		if err != nil {
			httpx.ServerError(w, err)
			return
		}
		httpx.Created(w, t)
	default:
		httpx.Error(w, http.StatusMethodNotAllowed, "GET/POST required")
	}
}

func (a *API) tagByID(w http.ResponseWriter, r *http.Request) {
	rest := strings.Trim(strings.TrimPrefix(r.URL.Path, "/api/admin/tags/"), "/")
	parts := strings.SplitN(rest, "/", 2)
	id, err := parseInt(parts[0])
	if err != nil {
		httpx.BadRequest(w, "bad tag id")
		return
	}
	if len(parts) == 2 && parts[1] == "merge" {
		a.mergeTag(w, r, id)
		return
	}
	switch r.Method {
	case http.MethodPut, http.MethodPatch:
		var in struct {
			Name  string `json:"name"`
			Color string `json:"color"`
		}
		if err := httpx.Decode(r, &in); err != nil {
			httpx.BadRequest(w, "invalid body")
			return
		}
		t, err := a.Store.UpdateTag(id, in.Name, in.Color)
		writeTag(w, t, err)
	case http.MethodDelete:
		if err := a.Store.DeleteTag(id); err != nil {
			httpx.ServerError(w, err)
			return
		}
		httpx.OK(w, map[string]any{"ok": true})
	default:
		httpx.Error(w, http.StatusMethodNotAllowed, "PUT/DELETE required")
	}
}

func (a *API) mergeTag(w http.ResponseWriter, r *http.Request, fromID int64) {
	if r.Method != http.MethodPost {
		httpx.Error(w, http.StatusMethodNotAllowed, "POST required")
		return
	}
	var in struct {
		ToID int64 `json:"to_id"`
	}
	if err := httpx.Decode(r, &in); err != nil {
		httpx.BadRequest(w, "invalid body")
		return
	}
	if in.ToID == 0 {
		httpx.BadRequest(w, "to_id required")
		return
	}
	t, err := a.Store.MergeTags(fromID, in.ToID)
	writeTag(w, t, err)
}

func writeTag(w http.ResponseWriter, t model.Tag, err error) {
	if err != nil {
		if errors.Is(err, store.ErrNotFound) {
			httpx.NotFound(w)
			return
		}
		httpx.Error(w, http.StatusBadRequest, err.Error())
		return
	}
	httpx.OK(w, t)
}

// ---------- projects ----------

func (a *API) listProjects(w http.ResponseWriter, r *http.Request) {
	switch r.Method {
	case http.MethodGet:
		status := httpx.QueryString(r, "status")
		projects, err := a.Store.ListProjects(status)
		if err != nil {
			httpx.ServerError(w, err)
			return
		}
		if projects == nil {
			projects = []model.Project{}
		}
		httpx.OK(w, map[string]any{"projects": projects})
	case http.MethodPost:
		var in model.ProjectInput
		if err := httpx.Decode(r, &in); err != nil {
			httpx.BadRequest(w, "invalid body")
			return
		}
		if strings.TrimSpace(in.Title) == "" {
			httpx.BadRequest(w, "title required")
			return
		}
		p, err := a.Store.CreateProject(in)
		if err != nil {
			httpx.ServerError(w, err)
			return
		}
		httpx.Created(w, p)
	default:
		httpx.Error(w, http.StatusMethodNotAllowed, "GET/POST required")
	}
}

func (a *API) projectByID(w http.ResponseWriter, r *http.Request) {
	rest := strings.Trim(strings.TrimPrefix(r.URL.Path, "/api/admin/projects/"), "/")
	if rest == "" {
		a.listProjects(w, r)
		return
	}
	id, err := parseInt(rest)
	if err != nil {
		httpx.BadRequest(w, "bad project id")
		return
	}
	switch r.Method {
	case http.MethodGet:
		p, err := a.Store.GetProject(id)
		writeProject(w, p, err)
	case http.MethodPut, http.MethodPatch:
		var in model.ProjectInput
		if err := httpx.Decode(r, &in); err != nil {
			httpx.BadRequest(w, "invalid body")
			return
		}
		p, err := a.Store.UpdateProject(id, in)
		writeProject(w, p, err)
	case http.MethodDelete:
		if err := a.Store.DeleteProject(id); err != nil {
			if errors.Is(err, store.ErrNotFound) {
				httpx.NotFound(w)
				return
			}
			httpx.ServerError(w, err)
			return
		}
		httpx.OK(w, map[string]any{"ok": true})
	default:
		httpx.Error(w, http.StatusMethodNotAllowed, "GET/PUT/DELETE required")
	}
}

func writeProject(w http.ResponseWriter, p model.Project, err error) {
	if err != nil {
		if errors.Is(err, store.ErrNotFound) {
			httpx.NotFound(w)
			return
		}
		httpx.ServerError(w, err)
		return
	}
	httpx.OK(w, p)
}

// ---------- settings ----------

func (a *API) settings(w http.ResponseWriter, r *http.Request) {
	switch r.Method {
	case http.MethodGet:
		st, err := a.Store.GetSettings()
		if err != nil {
			httpx.ServerError(w, err)
			return
		}
		httpx.OK(w, st)
	case http.MethodPut, http.MethodPost:
		var in model.Settings
		if err := httpx.Decode(r, &in); err != nil {
			httpx.BadRequest(w, "invalid body")
			return
		}
		if err := a.Store.UpdateSettings(in); err != nil {
			httpx.ServerError(w, err)
			return
		}
		st, err := a.Store.GetSettings()
		if err != nil {
			httpx.ServerError(w, err)
			return
		}
		httpx.OK(w, st)
	default:
		httpx.Error(w, http.StatusMethodNotAllowed, "GET/PUT required")
	}
}

func parseInt(s string) (int64, error) {
	if s == "" {
		return 0, errors.New("empty")
	}
	var n int64
	for _, c := range s {
		if c < '0' || c > '9' {
			return 0, errors.New("not a number")
		}
		n = n*10 + int64(c-'0')
	}
	return n, nil
}

// ---------- dashboard ----------

func (a *API) dashboard(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodGet {
		httpx.Error(w, http.StatusMethodNotAllowed, "GET required")
		return
	}
	d, err := a.Store.Dashboard()
	if err != nil {
		httpx.ServerError(w, err)
		return
	}
	httpx.OK(w, d)
}

// ---------- bulk posts ----------

type bulkPostsRequest struct {
	IDs    []int64 `json:"ids"`
	Action string  `json:"action"` // "publish" | "draft" | "delete"
}

func (a *API) bulkPosts(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		httpx.Error(w, http.StatusMethodNotAllowed, "POST required")
		return
	}
	var in bulkPostsRequest
	if err := httpx.Decode(r, &in); err != nil {
		httpx.BadRequest(w, "invalid body")
		return
	}
	if len(in.IDs) == 0 {
		httpx.BadRequest(w, "ids required")
		return
	}
	switch in.Action {
	case "publish", "draft":
		n, err := a.Store.BulkUpdateStatus(in.IDs, store.NormalizeStatus(in.Action))
		if err != nil {
			httpx.ServerError(w, err)
			return
		}
		httpx.OK(w, map[string]any{"ok": true, "updated": n})
	case "delete":
		var failed int
		for _, id := range in.IDs {
			if err := a.Store.Delete(id); err != nil {
				failed++
			}
		}
		httpx.OK(w, map[string]any{"ok": true, "deleted": len(in.IDs) - failed, "failed": failed})
	default:
		httpx.BadRequest(w, "action must be one of publish|draft|delete")
	}
}

// ---------- files（上传与文件管理） ----------

// 单文件上限与类型白名单。SVG 拒绝：同源内联可执行脚本。
const (
	maxFileUpload = 50 << 20
)

var allowFileExt = map[string]string{
	".jpg":  "image/jpeg",
	".jpeg": "image/jpeg",
	".png":  "image/png",
	".webp": "image/webp",
	".gif":  "image/gif",
	".avif": "image/avif",
	".pdf":  "application/pdf",
	".zip":  "application/zip",
	".txt":  "text/plain",
}

func (a *API) files(w http.ResponseWriter, r *http.Request) {
	switch r.Method {
	case http.MethodGet:
		fp, err := a.Store.ListFiles(httpx.QueryInt(r, "page", 1), httpx.QueryInt(r, "size", 20), httpx.QueryString(r, "q"))
		if err != nil {
			httpx.ServerError(w, err)
			return
		}
		for i := range fp.Items {
			fp.Items[i].URL = storage.FileURL(fp.Items[i].Store, fp.Items[i].Key, a.Cfg.UploadsPublicBase)
		}
		httpx.OK(w, fp)
	case http.MethodPost:
		a.uploadFiles(w, r)
	default:
		httpx.Error(w, http.StatusMethodNotAllowed, "GET/POST required")
	}
}

func (a *API) uploadFiles(w http.ResponseWriter, r *http.Request) {
	// 64MB = 50MB 文件 + multipart 编码开销
	r.Body = http.MaxBytesReader(w, r.Body, maxFileUpload+(8<<20))
	if err := r.ParseMultipartForm(8 << 20); err != nil {
		httpx.BadRequest(w, "上传失败：请求体超过上限（单文件 50MB）")
		return
	}
	if r.MultipartForm != nil {
		defer r.MultipartForm.RemoveAll()
	}
	fhs := r.MultipartForm.File["file"]
	if len(fhs) == 0 {
		httpx.BadRequest(w, "没有收到文件")
		return
	}
	out := make([]model.File, 0, len(fhs))
	for _, fh := range fhs {
		f, err := a.storeOne(r.Context(), fh)
		if err != nil {
			if bu, ok := err.(badUpload); ok {
				httpx.BadRequest(w, string(bu))
				return
			}
			httpx.ServerError(w, err)
			return
		}
		out = append(out, f)
	}
	// URL 统一在这里解析：storeOne 的「去重复用已有行」路径也不例外
	for i := range out {
		out[i].URL = storage.FileURL(out[i].Store, out[i].Key, a.Cfg.UploadsPublicBase)
	}
	httpx.Created(w, out)
}

// badUpload 区分「文件本身的问题」（类型 / 大小 → 400 直接告诉站主）与
// 服务器故障（500，已入库的部分保留）。
type badUpload string

func (e badUpload) Error() string { return string(e) }

// storeOne 校验、哈希、落盘单个文件。内容哈希做 key（同年月分目录），
// 同内容重复上传直接复用已有行，不产生孤儿对象。
func (a *API) storeOne(ctx context.Context, fh *multipart.FileHeader) (model.File, error) {
	if fh.Size > maxFileUpload {
		return model.File{}, badUpload(fmt.Sprintf("%s：超过单文件 50MB 上限", fh.Filename))
	}
	ext := strings.ToLower(filepath.Ext(fh.Filename))
	mime, ok := allowFileExt[ext]
	if !ok {
		return model.File{}, badUpload(fmt.Sprintf("%s：不支持的类型 %q", fh.Filename, ext))
	}
	src, err := fh.Open()
	if err != nil {
		return model.File{}, err
	}
	defer src.Close()

	// 头 512 字节给 http.DetectContentType 嗅探真实类型，全文流过 sha256，
	// 同时落到临时文件（S3 PutObject 需要确定的 ContentLength）。
	tmp, err := os.CreateTemp("", "one-upload-*")
	if err != nil {
		return model.File{}, err
	}
	defer os.Remove(tmp.Name())
	hasher := sha256.New()
	head := make([]byte, 512)
	hn, _ := io.ReadFull(src, head)
	head = head[:hn]
	for _, w := range []io.Writer{tmp, hasher} {
		if _, err := w.Write(head); err != nil {
			tmp.Close()
			return model.File{}, err
		}
	}
	copied, err := io.Copy(io.MultiWriter(tmp, hasher), src)
	if err != nil {
		tmp.Close()
		return model.File{}, err
	}
	if err := tmp.Close(); err != nil {
		return model.File{}, err
	}
	size := int64(hn) + copied

	// 嗅探结果必须与扩展名声明的类型完全一致（防改后缀绕过白名单）。
	// 不给 octet-stream 留口子：一张「image/png」嗅探出 octet-stream
	// 就绝不是 PNG——随机字节改名上传就是这么溜进来的。
	detected := strings.SplitN(http.DetectContentType(head), ";", 2)[0]
	if detected != mime {
		return model.File{}, badUpload(fmt.Sprintf("%s：文件内容与扩展名不符", fh.Filename))
	}

	sum := hex.EncodeToString(hasher.Sum(nil))
	key := fmt.Sprintf("%s/%s%s", time.Now().UTC().Format("2006/01"), sum[:12], ext)
	// S3Api 端点带路径段时（如 .../oss），该段会折进对象 key——
	// 数据库必须记录同样的完整 key，直链才不会 404
	if p := storage.EndpointKeyPrefix(a.Cfg.S3Endpoint); p != "" {
		key = p + "/" + key
	}

	// 内容去重：同一份内容只存一份，复用已有行
	if exist, err := a.Store.GetFileByKey(key); err == nil {
		return exist, nil
	}

	f, err := os.Open(tmp.Name())
	if err != nil {
		return model.File{}, err
	}
	defer f.Close()
	if err := a.Blobs.Put(ctx, key, f, size, mime); err != nil {
		return model.File{}, err
	}

	created, err := a.Store.CreateFile(model.File{
		Key:    key,
		Name:   fh.Filename,
		Mime:   mime,
		Size:   size,
		SHA256: sum,
		Store:  a.Cfg.StorageDriver,
	})
	if err != nil {
		return model.File{}, err
	}
	created.URL = storage.FileURL(created.Store, created.Key, a.Cfg.UploadsPublicBase)
	return created, nil
}

func (a *API) fileByID(w http.ResponseWriter, r *http.Request) {
	id, err := parseInt(strings.Trim(strings.TrimPrefix(r.URL.Path, "/api/admin/files/"), "/"))
	if err != nil {
		httpx.BadRequest(w, "bad file id")
		return
	}
	switch r.Method {
	case http.MethodGet:
		f, err := a.Store.GetFile(id)
		if errors.Is(err, store.ErrNotFound) {
			httpx.NotFound(w)
			return
		}
		if err != nil {
			httpx.ServerError(w, err)
			return
		}
		f.URL = storage.FileURL(f.Store, f.Key, a.Cfg.UploadsPublicBase)
		httpx.OK(w, f)
	case http.MethodDelete:
		f, err := a.Store.GetFile(id)
		if errors.Is(err, store.ErrNotFound) {
			httpx.NotFound(w)
			return
		}
		if err != nil {
			httpx.ServerError(w, err)
			return
		}
		// 先删对象存储再删行：存储端失败时行保留，可以重试
		if err := a.Blobs.Delete(r.Context(), f.Key); err != nil {
			httpx.ServerError(w, err)
			return
		}
		if _, err := a.Store.DeleteFile(id); err != nil {
			httpx.ServerError(w, err)
			return
		}
		httpx.OK(w, map[string]any{"ok": true})
	default:
		httpx.Error(w, http.StatusMethodNotAllowed, "GET/DELETE required")
	}
}