package authz

import (
	"context"
	"errors"

	"github.com/jackc/pgx/v5/pgxpool"
)

const PermManage = "perm:manage"
const PermManageProjectMembers = "project:manage_members"

// Service 统一系统 RBAC 与项目成员授权判定。
type Service struct {
	pool       *pgxpool.Pool
	authorizer *Authorizer
}

func NewService(pool *pgxpool.Pool) *Service {
	return &Service{pool: pool, authorizer: NewAuthorizer(pool)}
}

func (s *Service) enabled() bool {
	return s != nil && s.pool != nil
}

// Enabled 暴露 RBAC 是否已连接数据库。
func (s *Service) Enabled() bool {
	return s.enabled()
}

// ListCapabilities 返回用户系统级 permission key 列表。
func (s *Service) ListCapabilities(ctx context.Context, userID int64) ([]string, error) {
	if userID <= 0 {
		return nil, errors.New("authz: invalid user id")
	}
	if !s.enabled() {
		return nil, nil
	}
	rows, err := s.pool.Query(ctx, `
		SELECT DISTINCT p.perm_key
		FROM user_role_bindings b
		JOIN system_roles sr ON sr.id = b.role_id AND sr.status = 'active'
		JOIN system_role_permissions rp ON rp.role_id = b.role_id AND rp.effect = 'allow'
		JOIN system_permissions p ON p.id = rp.permission_id
		WHERE b.user_id = $1
		  AND b.scope_type = 'system'
		  AND b.scope_id = 0
		  AND b.valid_from <= now()
		  AND (b.valid_until IS NULL OR b.valid_until > now())
		ORDER BY p.perm_key
	`, userID)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	out := make([]string, 0)
	for rows.Next() {
		var key string
		if err := rows.Scan(&key); err != nil {
			return nil, err
		}
		out = append(out, key)
	}
	return out, rows.Err()
}

// hasCapabilityBinding 仅查 DB 角色绑定（不含 role_id 兜底）。
func (s *Service) hasCapabilityBinding(ctx context.Context, userID int64, permKey string) (bool, error) {
	if userID <= 0 || permKey == "" {
		return false, nil
	}
	caps, err := s.ListCapabilities(ctx, userID)
	if err != nil {
		return false, err
	}
	for _, k := range caps {
		if k == permKey || k == PermManage {
			return true, nil
		}
	}
	return false, nil
}

// HasSystemPermission 判定用户是否具备系统级 permission。
//
// Phase-2 system:*：系统管理员授予全部；非管理员 fail-closed false。
// 本阶段不改 authz schema — 管理员 all-or-nothing，无按角色拆分绑定。
// 其它历史键（project:*、perm:manage 等）：管理员或 DB 绑定任一即可。
func (s *Service) HasSystemPermission(ctx context.Context, userID int64, roleID, permKey string) (bool, error) {
	if userID <= 0 || permKey == "" {
		return false, nil
	}
	admin, err := s.IsSystemAdmin(ctx, userID, roleID)
	if err != nil {
		return false, err
	}
	if admin {
		return true, nil
	}
	if IsSystemConsolePermission(permKey) {
		return false, nil
	}
	return s.hasCapabilityBinding(ctx, userID, permKey)
}

// IsSystemAdmin 系统管理员（role-admin 或 perm:manage）。
func (s *Service) IsSystemAdmin(ctx context.Context, userID int64, roleID string) (bool, error) {
	if roleID == "role-admin" {
		return true, nil
	}
	return s.hasCapabilityBinding(ctx, userID, PermManage)
}

// CanManageProjectMembers 项目 owner/创建人、系统管理员，或持有 project:manage_members 的用户可管理成员。
func (s *Service) CanManageProjectMembers(ctx context.Context, projectID, userID int64, roleID string) (bool, error) {
	if userID <= 0 || projectID <= 0 {
		return false, nil
	}
	admin, err := s.IsSystemAdmin(ctx, userID, roleID)
	if err != nil {
		return false, err
	}
	if admin {
		return true, nil
	}
	hasPerm, err := s.HasSystemPermission(ctx, userID, roleID, PermManageProjectMembers)
	if err != nil {
		return false, err
	}
	if hasPerm {
		return true, nil
	}
	if s.authorizer == nil {
		return !s.enabled() && userID > 0, nil
	}
	return s.authorizer.IsProjectOwner(ctx, projectID, userID)
}