package app

import (
	"context"
	"crypto/sha256"
	"database/sql"
	"errors"
	"net/http"
	"strings"
	"time"
)

const (
	adminAccessTokenTTL   = 30 * time.Minute
	adminRefreshTokenTTL  = 7 * 24 * time.Hour
	adminRefreshCookieKey = "xingyu_admin_refresh"
)

func adminUserAgentHash(r *http.Request) []byte {
	sum := sha256.Sum256([]byte(strings.TrimSpace(r.UserAgent())))
	return sum[:]
}

func (a *App) setAdminRefreshCookie(w http.ResponseWriter, token string, expiresAt time.Time) {
	maxAge := int(time.Until(expiresAt).Seconds())
	if maxAge < 0 {
		maxAge = 0
	}
	sameSite := http.SameSiteLaxMode
	secure := a.config.Environment == "production"
	if secure {
		// Production supports a dedicated HTTPS API domain while keeping the
		// refresh token inaccessible to JavaScript.
		sameSite = http.SameSiteNoneMode
	}
	http.SetCookie(w, &http.Cookie{
		Name:     adminRefreshCookieKey,
		Value:    token,
		Path:     "/admin/v1/auth",
		Expires:  expiresAt,
		MaxAge:   maxAge,
		HttpOnly: true,
		Secure:   secure,
		SameSite: sameSite,
	})
}

func (a *App) clearAdminRefreshCookie(w http.ResponseWriter) {
	http.SetCookie(w, &http.Cookie{
		Name:     adminRefreshCookieKey,
		Value:    "",
		Path:     "/admin/v1/auth",
		Expires:  time.Unix(1, 0),
		MaxAge:   -1,
		HttpOnly: true,
		Secure:   a.config.Environment == "production",
		SameSite: func() http.SameSite {
			if a.config.Environment == "production" {
				return http.SameSiteNoneMode
			}
			return http.SameSiteLaxMode
		}(),
	})
}

func (a *App) adminRefreshTokenFromRequest(r *http.Request) string {
	if cookie, err := r.Cookie(adminRefreshCookieKey); err == nil {
		if token := strings.TrimSpace(cookie.Value); token != "" {
			return token
		}
	}
	if r.Body == nil || r.ContentLength == 0 {
		return ""
	}
	var req struct {
		RefreshToken string `json:"refreshToken"`
	}
	if decode(r, &req) != nil {
		return ""
	}
	return strings.TrimSpace(req.RefreshToken)
}

func (a *App) newAdminSession(ctx context.Context, w http.ResponseWriter, r *http.Request, adminID int64, realName string) (map[string]any, error) {
	refreshToken := randomToken()
	refreshHash := sha256.Sum256([]byte(refreshToken))
	expiresAt := time.Now().Add(adminRefreshTokenTTL)
	if _, err := a.db.ExecContext(ctx, `INSERT INTO admin_sessions(admin_user_id,refresh_token_hash,user_agent_hash,ip,expires_at) VALUES(?,?,?,?,?)`, adminID, refreshHash[:], adminUserAgentHash(r), clientIP(r), expiresAt); err != nil {
		return nil, err
	}
	accessToken, err := a.token(adminID, "admin", realName, adminAccessTokenTTL)
	if err != nil {
		_, _ = a.db.ExecContext(ctx, `UPDATE admin_sessions SET revoked_at=NOW(3) WHERE refresh_token_hash=?`, refreshHash[:])
		return nil, err
	}
	a.setAdminRefreshCookie(w, refreshToken, expiresAt)
	result := map[string]any{"accessToken": accessToken, "expiresIn": int(adminAccessTokenTTL.Seconds())}
	if a.config.Environment != "production" {
		// HTTP development across localhost/127.0.0.1 cannot use a SameSite=None
		// cookie. The fallback is sessionStorage-only on the admin client.
		result["refreshToken"] = refreshToken
	}
	return result, nil
}

func (a *App) rotateAdminSession(ctx context.Context, w http.ResponseWriter, r *http.Request, refreshToken string) (map[string]any, error) {
	oldHash := sha256.Sum256([]byte(refreshToken))
	tx, err := a.db.BeginTx(ctx, &sql.TxOptions{Isolation: sql.LevelReadCommitted})
	if err != nil {
		return nil, err
	}
	defer func() { _ = tx.Rollback() }()

	var sessionID, adminID int64
	var realName string
	var status int
	var expiresAt time.Time
	err = tx.QueryRowContext(ctx, `SELECT s.id,a.id,a.real_name,a.status,s.expires_at
		FROM admin_sessions s JOIN admin_users a ON a.id=s.admin_user_id
		WHERE s.refresh_token_hash=? AND s.revoked_at IS NULL AND s.expires_at>NOW(3)
		FOR UPDATE`, oldHash[:]).Scan(&sessionID, &adminID, &realName, &status, &expiresAt)
	if err != nil || status != 1 {
		return nil, errors.New("刷新令牌无效或已过期")
	}

	newRefreshToken := randomToken()
	newHash := sha256.Sum256([]byte(newRefreshToken))
	result, err := tx.ExecContext(ctx, `UPDATE admin_sessions SET refresh_token_hash=?,user_agent_hash=?,ip=?,last_active_at=NOW(3) WHERE id=? AND refresh_token_hash=? AND revoked_at IS NULL`, newHash[:], adminUserAgentHash(r), clientIP(r), sessionID, oldHash[:])
	if err != nil {
		return nil, err
	}
	affected, _ := result.RowsAffected()
	if affected != 1 {
		return nil, errors.New("刷新令牌已被使用")
	}
	if err = tx.Commit(); err != nil {
		return nil, err
	}

	accessToken, err := a.token(adminID, "admin", realName, adminAccessTokenTTL)
	if err != nil {
		return nil, err
	}
	a.setAdminRefreshCookie(w, newRefreshToken, expiresAt)
	payload := map[string]any{"accessToken": accessToken, "expiresIn": int(adminAccessTokenTTL.Seconds())}
	if a.config.Environment != "production" {
		payload["refreshToken"] = newRefreshToken
	}
	return payload, nil
}

func (a *App) revokeAdminSession(ctx context.Context, refreshToken string) {
	if strings.TrimSpace(refreshToken) == "" {
		return
	}
	hash := sha256.Sum256([]byte(refreshToken))
	_, _ = a.db.ExecContext(ctx, `UPDATE admin_sessions SET revoked_at=NOW(3) WHERE refresh_token_hash=? AND revoked_at IS NULL`, hash[:])
}

func (a *App) adminRefresh(w http.ResponseWriter, r *http.Request) {
	if !a.rateLimit(w, r, "admin_refresh", clientIP(r), 120, 10*time.Minute) {
		return
	}
	refreshToken := a.adminRefreshTokenFromRequest(r)
	if refreshToken == "" {
		a.clearAdminRefreshCookie(w)
		fail(w, http.StatusUnauthorized, 10001, "刷新令牌不存在")
		return
	}
	payload, err := a.rotateAdminSession(r.Context(), w, r, refreshToken)
	if err != nil {
		a.clearAdminRefreshCookie(w)
		fail(w, http.StatusUnauthorized, 10001, err.Error())
		return
	}
	reply(w, payload)
}

func (a *App) adminLogout(w http.ResponseWriter, r *http.Request) {
	a.revokeAdminSession(r.Context(), a.adminRefreshTokenFromRequest(r))
	a.clearAdminRefreshCookie(w)
	reply(w, map[string]bool{"success": true})
}