import NextAuth from 'next-auth';
import Credentials from 'next-auth/providers/credentials';
import Google from 'next-auth/providers/google';
import GitHub from 'next-auth/providers/github';
import { PrismaAdapter } from '@auth/prisma-adapter';
import bcrypt from 'bcryptjs';
import { db } from '@/lib/db';
import { ProjectMemberRole, WorkspaceMemberRole } from '@prisma/client';
import { hasBillingAccess } from '@/lib/billing';
import { isInviteCodeRequired } from '@/lib/feature-flags';
import { isEmailVerificationEnabled } from '@/lib/email-verification';

// Dummy hash for timing-safe comparison when user doesn't exist
// This prevents user enumeration via timing attacks
const DUMMY_HASH = '$2a$12$000000000000000000000uGG3k3xK2CVTxXrT7VW2sGd1XrY6Ky';

export const { handlers, signIn, signOut, auth } = NextAuth({
  // PrismaAdapter handles OAuth account linking and user creation in DB.
  // JWT strategy is still used for sessions (no DB sessions table needed).
  adapter: PrismaAdapter(db),
  providers: [
    Credentials({
      name: 'credentials',
      credentials: {
        email: { label: 'Email', type: 'email' },
        password: { label: 'Password', type: 'password' },
      },
      async authorize(credentials) {
        if (!credentials?.email || !credentials?.password) {
          return null;
        }

        const email = credentials.email as string;
        const password = credentials.password as string;

        // Find user by email
        const user = await db.user.findUnique({
          where: { email: email.toLowerCase() },
        });

        // Always perform bcrypt comparison to prevent timing attacks
        // If user doesn't exist, compare against dummy hash
        const hashToCompare = user?.password || DUMMY_HASH;
        const isValidPassword = await bcrypt.compare(password, hashToCompare);

        // Only return user if they exist AND password is valid
        if (!user || !user.password || !isValidPassword) {
          return null;
        }

        // Block sign-in when email verification is required but not yet completed
        if (isEmailVerificationEnabled() && !user.emailVerified) {
          return null;
        }

        return {
          id: user.id,
          name: user.name,
          email: user.email,
          image: user.image,
        };
      },
    }),
    ...(process.env.GOOGLE_CLIENT_ID && process.env.GOOGLE_CLIENT_SECRET
      ? [Google({ clientId: process.env.GOOGLE_CLIENT_ID, clientSecret: process.env.GOOGLE_CLIENT_SECRET })]
      : []),
    ...(process.env.GITHUB_CLIENT_ID && process.env.GITHUB_CLIENT_SECRET
      ? [{
          ...GitHub({ clientId: process.env.GITHUB_CLIENT_ID, clientSecret: process.env.GITHUB_CLIENT_SECRET }),
          // GitHub sends iss=https://github.com/login/oauth in callbacks (RFC 9207).
          // Auth.js v5 beta defaults to "https://authjs.dev" for OAuth providers, causing
          // a mismatch. Setting the correct issuer here fixes the CallbackRouteError.
          issuer: 'https://github.com/login/oauth',
        }]
      : []),
  ],
  session: {
    strategy: 'jwt',
    maxAge: 30 * 24 * 60 * 60, // 30 days
  },
  pages: {
    signIn: '/login',
    signOut: '/signout',
  },
  callbacks: {
    async signIn({ account, profile }) {
      // Credentials sign-in is handled by the authorize() function above
      if (account?.provider === 'credentials') return true;

      // Reject OAuth sign-ins where the provider email is not verified.
      // Google always sets email_verified: true. GitHub does not guarantee it.
      if (profile && profile.email_verified === false) {
        return '/login?error=OAuthEmailNotVerified';
      }

      // OAuth sign-in: allow existing OAuth accounts regardless of invite setting
      if (account?.providerAccountId && account?.provider) {
        const existingAccount = await db.account.findUnique({
          where: { provider_providerAccountId: { provider: account.provider, providerAccountId: account.providerAccountId } },
          select: { id: true },
        });
        if (existingAccount) return true;
      }

      // New OAuth user: block when invite-only mode is active
      if (isInviteCodeRequired()) {
        return '/login?error=RegistrationClosed';
      }

      return true;
    },
    async session({ session, token }) {
      if (token.sub && session.user) {
        session.user.id = token.sub;
        session.user.name = token.name || null;
        session.user.isAdmin = token.isAdmin as boolean;
      }
      return session;
    },
    async jwt({ token, user }) {
      if (user) {
        token.sub = user.id;
        token.name = user.name;
        token.email = user.email; // explicitly ensure email is in the token
      }

      // Check if user is admin based on emails list on EVERY request to ensure env changes are picked up
      if (token.email) {
        const adminEmails = process.env.ADMIN_EMAILS
          ? process.env.ADMIN_EMAILS.split(',').map((e: string) => e.trim().toLowerCase())
          : [];
        token.isAdmin = adminEmails.includes((token.email as string).toLowerCase());
      }

      return token;
    },
  },
});

type ProjectAccessIntent = 'view' | 'manage' | 'delete';

// ---------------------------------------------------------------------------
// Fast-path: pre-fetch access data alongside any existing DB query so that
// computeProjectAccess() can resolve the result with zero extra round-trips.
// ---------------------------------------------------------------------------

/** Prisma include fragment to attach to any project fetch. */
export function projectAccessInclude(userId: string | undefined) {
  return {
    workspace: {
      select: {
        id: true,
        ownerId: true,
        owner: {
          select: {
            subscriptionStatus: true,
            trialEndsAt: true,
            stripeCurrentPeriodEnd: true,
            billingAccessEndedAt: true,
          },
        },
        members: userId
          ? { where: { userId }, take: 1, orderBy: { createdAt: 'asc' as const }, select: { role: true } }
          : { take: 0, select: { role: true } },
      },
    },
    members: userId
      ? { where: { userId }, take: 1, orderBy: { createdAt: 'asc' as const }, select: { role: true } }
      : { take: 0, select: { role: true } },
  };
}

type ProjectAccessIncludes = ReturnType<typeof projectAccessInclude>;
type WorkspaceForAccess = ProjectAccessIncludes['workspace']['select'] extends object
  ? {
      id: string;
      ownerId: string;
      owner: Parameters<typeof hasBillingAccess>[0] | null;
      members: Array<{ role: WorkspaceMemberRole }>;
    }
  : never;

export type EnrichedProjectForAccess = {
  id: string;
  ownerId: string;
  workspaceId: string;
  visibility: string;
  workspace: WorkspaceForAccess;
  members: Array<{ role: ProjectMemberRole }>;
};

/**
 * Pure access computation — no DB queries.
 * Use after fetching a project with `projectAccessInclude(userId)`.
 */
export function computeProjectAccess(
  project: EnrichedProjectForAccess,
  userId: string | undefined,
) {
  const isOwner = userId === project.ownerId;
  const isPublic = project.visibility === 'PUBLIC';

  const projectMember = project.members[0] ?? null;
  const isProjectMember = !!projectMember;
  const isProjectAdmin = projectMember?.role === ProjectMemberRole.ADMIN;

  const workspaceOwnerBillingAccess = project.workspace.owner
    ? hasBillingAccess(project.workspace.owner)
    : false;

  let workspaceRole: WorkspaceMemberRole | 'OWNER' | null = null;
  if (userId === project.workspace.ownerId) {
    workspaceRole = 'OWNER';
  } else {
    const wsMember = project.workspace.members[0] ?? null;
    if (wsMember) workspaceRole = wsMember.role;
  }

  const isWorkspaceMember = !!workspaceRole;
  const isWorkspaceAdmin =
    workspaceRole === WorkspaceMemberRole.ADMIN || workspaceRole === 'OWNER';

  const hasAccess =
    workspaceOwnerBillingAccess &&
    (isOwner || isProjectMember || isPublic || isWorkspaceMember);
  const canEdit =
    workspaceOwnerBillingAccess && (isOwner || isProjectAdmin || isWorkspaceAdmin);
  const canDelete =
    workspaceOwnerBillingAccess && (isOwner || workspaceRole === 'OWNER');

  return {
    isOwner,
    isProjectMember,
    isProjectAdmin,
    isWorkspaceMember,
    isWorkspaceAdmin,
    hasAccess,
    canEdit,
    canDelete,
    ownerBillingActive: workspaceOwnerBillingAccess,
  };
}

// Helper to check project access including workspace membership
export async function checkProjectAccess(
  project: { id: string; ownerId: string; workspaceId: string; visibility: string },
  userId: string | undefined,
  options?: { intent?: ProjectAccessIntent }
) {
  const intent = options?.intent ?? 'view';
  const isOwner = userId === project.ownerId;
  const isPublic = project.visibility === 'PUBLIC';

  // Get project membership
  const projectMember = userId
    ? await db.projectMember.findUnique({
      where: { projectId_userId: { projectId: project.id, userId } },
    })
    : null;
  const isProjectMember = !!projectMember;
  const isProjectAdmin = projectMember?.role === ProjectMemberRole.ADMIN;

  const needsWorkspaceForAccess = !!userId && !isOwner && !isProjectMember && !isPublic;
  const needsWorkspaceForActions = !!userId && !isOwner && intent !== 'view';
  const shouldLoadWorkspaceRole = needsWorkspaceForAccess || needsWorkspaceForActions;

  // Check workspace membership/role
  let workspaceRole: WorkspaceMemberRole | 'OWNER' | null = null;
  let workspaceOwnerBillingAccess = false;
  if (shouldLoadWorkspaceRole && userId) {
    const [wsMember, wsOwner] = await Promise.all([
      db.workspaceMember.findUnique({
        where: { workspaceId_userId: { workspaceId: project.workspaceId, userId } },
      }),
      db.workspace.findUnique({
        where: { id: project.workspaceId },
        select: {
          ownerId: true,
          owner: {
            select: {
              subscriptionStatus: true,
              trialEndsAt: true,
              stripeCurrentPeriodEnd: true,
              billingAccessEndedAt: true,
            },
          },
        },
      }),
    ]);

    if (wsOwner?.ownerId === userId) {
      workspaceRole = 'OWNER';
    } else if (wsMember) {
      workspaceRole = wsMember.role;
    }

    if (wsOwner?.owner) {
      workspaceOwnerBillingAccess = hasBillingAccess(wsOwner.owner);
    }
  } else {
    const wsOwner = await db.workspace.findUnique({
      where: { id: project.workspaceId },
      select: {
        owner: {
          select: {
            subscriptionStatus: true,
            trialEndsAt: true,
            stripeCurrentPeriodEnd: true,
            billingAccessEndedAt: true,
          },
        },
      },
    });
    workspaceOwnerBillingAccess = wsOwner?.owner ? hasBillingAccess(wsOwner.owner) : false;
  }
  const isWorkspaceMember = !!workspaceRole;
  const isWorkspaceAdmin = workspaceRole === WorkspaceMemberRole.ADMIN || workspaceRole === 'OWNER';

  const hasAccess = workspaceOwnerBillingAccess && (isOwner || isProjectMember || isPublic || isWorkspaceMember);
  const canEdit = workspaceOwnerBillingAccess && (isOwner || isProjectAdmin || isWorkspaceAdmin);
  const canDelete = workspaceOwnerBillingAccess && (isOwner || workspaceRole === 'OWNER');

  return {
    isOwner,
    isProjectMember,
    isProjectAdmin,
    isWorkspaceMember,
    isWorkspaceAdmin,
    hasAccess,
    canEdit,
    canDelete,
    ownerBillingActive: workspaceOwnerBillingAccess,
  };
}

// Helper to check workspace access
export async function checkWorkspaceAccess(
  workspace: { id: string; ownerId: string },
  userId: string | undefined
) {
  const isOwner = userId === workspace.ownerId;

  // Get workspace membership
  const workspaceMember = userId
    ? await db.workspaceMember.findUnique({
      where: { workspaceId_userId: { workspaceId: workspace.id, userId } },
    })
    : null;
  const isMember = !!workspaceMember;
  const isAdmin = workspaceMember?.role === WorkspaceMemberRole.ADMIN;

  const owner = await db.user.findUnique({
    where: { id: workspace.ownerId },
    select: {
      subscriptionStatus: true,
      trialEndsAt: true,
      stripeCurrentPeriodEnd: true,
      billingAccessEndedAt: true,
    },
  });
  const ownerBillingActive = owner ? hasBillingAccess(owner) : false;

  const hasAccess = ownerBillingActive && (isOwner || isMember);
  const canEdit = ownerBillingActive && (isOwner || isAdmin);
  const canDelete = ownerBillingActive && isOwner;

  return {
    isOwner,
    isMember,
    isAdmin,
    hasAccess,
    canEdit,
    canDelete,
    ownerBillingActive,
  };
}