import { usersTable, tasksTable, clientsTable } from "@workspace/db";
import { eq, or } from "drizzle-orm";

export type User = typeof usersTable.$inferSelect;
export type Task = typeof tasksTable.$inferSelect;
export type Client = typeof clientsTable.$inferSelect;

export const ROLES = {
  ADMIN: "admin",
  HEAD_OF_TEAM: "head_of_team",
  TEAM_LEAD: "team_lead",
  MEMBER: "member",
} as const;

/**
 * Check if a user is an admin.
 */
export function isAdmin(user: User): boolean {
  return user.role === ROLES.ADMIN;
}

/**
 * Check if a user is Head of Team (operational supervisor).
 */
export function isHeadOfTeam(user: User): boolean {
  return user.role === ROLES.HEAD_OF_TEAM;
}

/**
 * Check if a user is a Team Lead.
 * Includes legacy 'dept_manager' role compatibility.
 */
export function isTeamLead(user: User): boolean {
  return user.role === ROLES.TEAM_LEAD || user.role === "dept_manager";
}

/**
 * Check if a user is a Member.
 */
export function isMember(user: User): boolean {
  return user.role === ROLES.MEMBER;
}

/**
 * Determines if a user has access to see tasks from all teams.
 */
export function canAccessAllTeams(user: User): boolean {
  return isAdmin(user) || isHeadOfTeam(user);
}

/**
 * Determines if a user can grant admin privileges.
 */
export function canGrantAdmin(requestingUser: User): boolean {
  return isAdmin(requestingUser);
}

/**
 * Determines if a user can manage sensitive system configuration.
 */
export function canManageSystemConfig(user: User): boolean {
  return isAdmin(user);
}

/**
 * Determines if a user can view a specific task.
 */
export function canAccessTask(user: User, task: Task): boolean {
  if (canAccessAllTeams(user)) return true;
  if (isTeamLead(user)) {
    return task.fromTeam === user.team || task.assignedTeam === user.team;
  }
  // Member: Only assigned, created, or involved.
  // Currently schema supports assigned and created fields.
  return (
    task.createdByUserId === user.id ||
    task.assignedUserId === user.id
  );
}

/**
 * Determines if a user can modify a specific task.
 */
export function canModifyTask(user: User, task: Task): boolean {
  if (isAdmin(user)) return true;
  if (isHeadOfTeam(user)) return true; // Supervise full operations
  
  if (isTeamLead(user)) {
    return task.fromTeam === user.team || task.assignedTeam === user.team;
  }
  
  // Members can update tasks they created or are assigned to
  return task.createdByUserId === user.id || task.assignedUserId === user.id;
}

/**
 * Determines if a user can view another user's profile/data.
 */
export function canAccessUser(requestingUser: User, targetUser: User): boolean {
  if (isAdmin(requestingUser)) return true;
  if (isHeadOfTeam(requestingUser)) return true;
  if (isTeamLead(requestingUser) && requestingUser.team === targetUser.team) return true;
  return requestingUser.id === targetUser.id;
}

/**
 * Returns a Drizzle filter expression for task visibility based on the new role model.
 */
export function getTaskVisibilityFilter(user: User) {
  if (canAccessAllTeams(user)) return undefined;
  
  if (isTeamLead(user)) {
    return or(
      eq(tasksTable.fromTeam, user.team),
      eq(tasksTable.assignedTeam, user.team)
    );
  }
  
  // Member: ONLY assigned or created
  return or(
    eq(tasksTable.createdByUserId, user.id),
    eq(tasksTable.assignedUserId, user.id)
  );
}