package gateway

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"net/http"
	"os"
	"path/filepath"
	"strings"
	"time"

	"git.yeij.top/AskaEth/Cyrene_v2/internal/auth"
	"git.yeij.top/AskaEth/Cyrene_v2/internal/db"
	apperr "git.yeij.top/AskaEth/Cyrene_v2/internal/errors"
)

// System management admin writes (owner-only, audited; design/11 §4 敏感操作代审 +
// design/10 §3 module 14 系统设置). Every handler audits a system.* action and never
// echoes a JWT secret or a database path back to the client.

// adminRevokeAllKeys revokes every currently registered API key. It is the
// `system.revoke_keys` admin write; the table is emptied so no prior key can
// authenticate afterward.
func (s *Server) adminRevokeAllKeys(w http.ResponseWriter, r *http.Request) {
	keys, ok := s.users.(*auth.APIKey)
	if !ok {
		s.auditClaims(r, "system.revoke_keys", "error")
		writeError(w, apperr.Wrap(apperr.ErrInternal, "users_unavailable", "用户服务未配置"))
		return
	}
	n := keys.RevokeAll()
	s.auditClaims(r, "system.revoke_keys", "ok")
	writeJSON(w, http.StatusOK, map[string]any{"revoked": n})
}

// rotateJWTRequest is the POST /api/v1/admin/system/rotate-jwt body. The new
// secret is accepted from the request so the owner can supply a fresh value; it
// is never echoed back or logged.
type rotateJWTRequest struct {
	NewSecret string `json:"newSecret"`
}

// adminRotateJWT replaces the JWT signing secret, invalidating every token issued
// under the old secret. It is the `system.rotate_jwt` admin write.
func (s *Server) adminRotateJWT(w http.ResponseWriter, r *http.Request) {
	var req rotateJWTRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeError(w, apperr.Wrap(apperr.ErrBadRequest, "bad_request", "invalid request body"))
		return
	}
	if strings.TrimSpace(req.NewSecret) == "" {
		s.auditClaims(r, "system.rotate_jwt", "error")
		writeError(w, apperr.Wrap(apperr.ErrBadRequest, "bad_request", "newSecret is required"))
		return
	}
	jwt, ok := s.auth.(*auth.JWTService)
	if !ok {
		s.auditClaims(r, "system.rotate_jwt", "error")
		writeError(w, apperr.Wrap(apperr.ErrInternal, "auth_unavailable", "认证服务未配置"))
		return
	}
	if err := jwt.RotateSecret(req.NewSecret); err != nil {
		s.auditClaims(r, "system.rotate_jwt", "error")
		if errors.Is(err, auth.ErrInvalidSecret) {
			writeError(w, apperr.Wrap(apperr.ErrBadRequest, "bad_request", "新密钥长度不足 32 位"))
			return
		}
		writeError(w, apperr.Wrap(apperr.ErrInternal, "rotate_failed", "failed to rotate jwt secret"))
		return
	}
	s.auditClaims(r, "system.rotate_jwt", "ok")
	writeJSON(w, http.StatusOK, map[string]any{
		"rotated": true,
		"note":    "现有 token 已全部失效，需重新登录",
	})
}

// adminBackup snapshots the SQLite database into the data directory using
// `VACUUM INTO` (which includes committed WAL content), returning the backup path
// and size. It is the `system.backup` admin write.
func (s *Server) adminBackup(w http.ResponseWriter, r *http.Request) {
	if strings.TrimSpace(s.dbPath) == "" {
		s.auditClaims(r, "system.backup", "error")
		writeError(w, apperr.Wrap(apperr.ErrInternal, "backup_unavailable", "数据库路径未配置"))
		return
	}
	path, size, err := s.backupDatabase(r.Context())
	if err != nil {
		s.auditClaims(r, "system.backup", "error")
		s.log.Error("backup", "err", err)
		writeError(w, apperr.Wrap(apperr.ErrInternal, "backup_failed", "备份失败"))
		return
	}
	s.auditClaims(r, "system.backup", "ok")
	writeJSON(w, http.StatusOK, map[string]any{"path": path, "size": size})
}

// restoreRequest is the POST /api/v1/admin/system/restore body. Path is the
// backup file to restore, expected to live inside the data directory.
type restoreRequest struct {
	Path string `json:"path"`
}

// adminRestore validates a backup path (must be inside the data directory — a
// path-traversal guard), snapshots the current database first, then replaces the
// live DB file. Because the running process holds the SQLite file handle open, the
// replace takes effect on restart; it is reported as such. It is the
// `system.restore` admin write.
func (s *Server) adminRestore(w http.ResponseWriter, r *http.Request) {
	var req restoreRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeError(w, apperr.Wrap(apperr.ErrBadRequest, "bad_request", "invalid request body"))
		return
	}
	if strings.TrimSpace(s.dbPath) == "" {
		s.auditClaims(r, "system.restore", "error")
		writeError(w, apperr.Wrap(apperr.ErrInternal, "backup_unavailable", "数据库路径未配置"))
		return
	}
	src := strings.TrimSpace(req.Path)
	if src == "" {
		s.auditClaims(r, "system.restore", "error")
		writeError(w, apperr.Wrap(apperr.ErrBadRequest, "bad_request", "path is required"))
		return
	}
	absSrc, ok := s.restorePathWithinDataDir(src)
	if !ok {
		s.auditClaims(r, "system.restore", "error")
		writeError(w, apperr.Wrap(apperr.ErrBadRequest, "bad_request", "恢复路径必须在数据目录内"))
		return
	}
	if _, err := os.Stat(absSrc); err != nil {
		s.auditClaims(r, "system.restore", "error")
		writeError(w, apperr.Wrap(apperr.ErrNotFound, "not_found", "备份文件不存在"))
		return
	}
	// Snapshot the current database before touching it, so an accidental restore
	// of the wrong file is recoverable.
	curPath, _, err := s.backupDatabase(r.Context())
	if err != nil {
		s.auditClaims(r, "system.restore", "error")
		s.log.Error("restore pre-backup", "err", err)
		writeError(w, apperr.Wrap(apperr.ErrInternal, "restore_failed", "恢复前备份失败"))
		return
	}
	if err := replaceDatabase(absSrc, s.dbPath); err != nil {
		s.auditClaims(r, "system.restore", "error")
		s.log.Error("restore replace", "err", err)
		writeError(w, apperr.Wrap(apperr.ErrInternal, "restore_failed", "替换数据库失败"))
		return
	}
	s.auditClaims(r, "system.restore", "ok")
	writeJSON(w, http.StatusOK, map[string]any{
		"restored": true,
		"backup":   curPath,
		"note":     "已安排恢复，需重启服务后生效",
	})
}

// restorePathWithinDataDir resolves src to an absolute path and reports whether it
// lives inside the data directory (the parent of s.dbPath). It is the path-
// traversal guard for the restore endpoint: only paths under the data dir are
// accepted.
func (s *Server) restorePathWithinDataDir(src string) (string, bool) {
	dataDir, err := filepath.Abs(filepath.Dir(s.dbPath))
	if err != nil {
		return "", false
	}
	dataDir = filepath.Clean(dataDir)
	absSrc, err := filepath.Abs(src)
	if err != nil {
		return "", false
	}
	absSrc = filepath.Clean(absSrc)
	rel, err := filepath.Rel(dataDir, absSrc)
	if err != nil || rel == ".." || strings.HasPrefix(rel, ".."+string(filepath.Separator)) {
		return "", false
	}
	return absSrc, true
}

// backupDatabase snapshots the live SQLite database into
// <dataDir>/backup-<ts>.db via `VACUUM INTO`, which includes every committed WAL
// transaction, and returns the new file's path and size. Opening a second
// connection to the file-backed database is safe: SQLite serializes access, and
// busy_timeout handles a momentarily locked source.
func (s *Server) backupDatabase(ctx context.Context) (string, int64, error) {
	dir := filepath.Dir(s.dbPath)
	if err := os.MkdirAll(dir, 0o755); err != nil {
		return "", 0, fmt.Errorf("create backup dir: %w", err)
	}
	dest := filepath.Join(dir, fmt.Sprintf("backup-%s.db", time.Now().UTC().Format("20060102T150405.000000000Z")))
	conn, err := db.Open(ctx, s.dbPath, s.log)
	if err != nil {
		return "", 0, fmt.Errorf("open db for backup: %w", err)
	}
	defer conn.Close()
	// VACUUM INTO takes a string literal, not a bound parameter; escape the
	// generated filename (safe characters, but escape defensively).
	query := fmt.Sprintf("VACUUM INTO '%s'", escapeSQLString(dest))
	if _, err := conn.ExecContext(ctx, query); err != nil {
		return "", 0, fmt.Errorf("vacuum into: %w", err)
	}
	info, err := os.Stat(dest)
	if err != nil {
		return "", 0, fmt.Errorf("stat backup: %w", err)
	}
	return dest, info.Size(), nil
}

// replaceDatabase atomically replaces the live DB file at dest with a copy of src,
// writing to a temp file first so a failure never leaves dest truncated. On Linux
// a running SQLite connection keeps its open handle to the old inode, so the new
// data becomes visible only after the process restarts — which the restore
// endpoint reports.
func replaceDatabase(src, dest string) error {
	in, err := os.Open(src)
	if err != nil {
		return fmt.Errorf("open source: %w", err)
	}
	defer in.Close()
	tmp := dest + ".restore.tmp"
	out, err := os.Create(tmp)
	if err != nil {
		return fmt.Errorf("create temp: %w", err)
	}
	if _, err := io.Copy(out, in); err != nil {
		_ = out.Close()
		_ = os.Remove(tmp)
		return fmt.Errorf("copy: %w", err)
	}
	if err := out.Close(); err != nil {
		_ = os.Remove(tmp)
		return fmt.Errorf("close temp: %w", err)
	}
	if err := os.Rename(tmp, dest); err != nil {
		_ = os.Remove(tmp)
		return fmt.Errorf("rename: %w", err)
	}
	return nil
}

// escapeSQLString doubles any single quote so a filename can be safely embedded
// in a SQL string literal for VACUUM INTO.
func escapeSQLString(s string) string {
	return strings.ReplaceAll(s, "'", "''")
}