import { randomBytes, createHash } from "node:crypto";
import { BadRequestException, ForbiddenException, Inject, Injectable, UnauthorizedException } from "@nestjs/common";
import { usersRepo, sessionsRepo, auditRepo, type User } from "@eden/database";
import { sendMail } from "@eden/integrations";
import type { EdenEnv } from "@eden/config";
import { EDEN_ENV } from "../config/config.constants.js";
import { PasswordService } from "./password.service.js";
import { TokenService } from "./token.service.js";
import { MfaService } from "./mfa.service.js";
import { resolvePermissions } from "./permissions.js";

export interface RequestContext {
  ipAddress?: string | null;
  userAgent?: string | null;
}

export interface AuthResult {
  accessToken: string;
  expiresIn: number;
  refreshToken: string;
  user: PublicUser;
}

export interface MfaRequiredResult {
  mfaRequired: true;
  mfaChallenge: string;
  expiresIn: number;
}

export type LoginResult = AuthResult | MfaRequiredResult;

export interface PublicUser {
  id: string;
  email: string;
  fullName: string | null;
  roleKey: string;
}

function toPublicUser(user: User): PublicUser {
  return { id: user.id, email: user.email, fullName: user.full_name, roleKey: user.role_key };
}

const GENERIC_LOGIN_ERROR = "Credenciais inválidas";
const RESET_TOKEN_TTL_MS = 60 * 60 * 1000; // 1h — deliberately short-lived (this token grants a password change)

function hashResetToken(plaintext: string): string {
  return createHash("sha256").update(plaintext).digest("hex");
}

@Injectable()
export class AuthService {
  constructor(
    private readonly passwords: PasswordService,
    private readonly tokens: TokenService,
    private readonly mfa: MfaService,
    @Inject(EDEN_ENV) private readonly env: EdenEnv,
  ) {}

  async login(
    email: string,
    password: string,
    applicationKey: "core" | "reseller" | "subscriber",
    ctx: RequestContext,
  ): Promise<LoginResult> {
    const user = await usersRepo.findUserByEmail(email);

    // Same generic error whether the account doesn't exist or the password
    // is wrong — anti-enumeration, mirrors eden.md §4.1.
    if (!user || !user.password_hash) {
      throw new UnauthorizedException(GENERIC_LOGIN_ERROR);
    }

    const valid = await this.passwords.verify(user.password_hash, password);
    if (!valid) {
      throw new UnauthorizedException(GENERIC_LOGIN_ERROR);
    }

    if (this.passwords.needsRehash(user.password_algo_version)) {
      const { hash, algoVersion } = await this.passwords.hash(password);
      await usersRepo.updateUserPassword(user.id, hash, algoVersion);
    }

    const grantedApps = await usersRepo.getUserApplications(user.id);
    if (!grantedApps.includes(applicationKey)) {
      throw new ForbiddenException("Usuário sem acesso a esta aplicação");
    }

    if (user.mfa_enabled) {
      const challenge = this.tokens.signMfaChallenge({ sub: user.id, app: applicationKey });
      await auditRepo.appendAuditEvent({
        actorType: "user",
        actorId: user.id,
        action: "auth.mfa_challenge_issued",
        resourceType: "user",
        resourceId: user.id,
        metadata: { applicationKey },
        ipAddress: ctx.ipAddress,
      });
      return { mfaRequired: true, mfaChallenge: challenge.token, expiresIn: challenge.expiresIn };
    }

    const result = await this.issueTokens(user, applicationKey, ctx);

    await auditRepo.appendAuditEvent({
      actorType: "user",
      actorId: user.id,
      action: "auth.login",
      resourceType: "user",
      resourceId: user.id,
      metadata: { applicationKey },
      ipAddress: ctx.ipAddress,
    });

    return result;
  }

  /** Second step of login when the account has MFA enabled — exchanges a password-verified challenge + TOTP code for real tokens. */
  async completeMfaLogin(challengeToken: string, code: string, ctx: RequestContext): Promise<AuthResult> {
    let payload;
    try {
      payload = this.tokens.verifyMfaChallenge(challengeToken);
    } catch {
      throw new UnauthorizedException("Desafio MFA inválido ou expirado");
    }

    const user = await usersRepo.findUserById(payload.sub);
    if (!user || !user.is_active || !user.mfa_enabled || !user.mfa_secret_encrypted) {
      throw new UnauthorizedException("Desafio MFA inválido ou expirado");
    }

    if (!(await this.mfa.verifyCode(user.mfa_secret_encrypted, code))) {
      await auditRepo.appendAuditEvent({
        actorType: "user",
        actorId: user.id,
        action: "auth.mfa_challenge_failed",
        resourceType: "user",
        resourceId: user.id,
        ipAddress: ctx.ipAddress,
      });
      throw new UnauthorizedException("Código inválido");
    }

    const result = await this.issueTokens(user, payload.app, ctx);

    await auditRepo.appendAuditEvent({
      actorType: "user",
      actorId: user.id,
      action: "auth.login",
      resourceType: "user",
      resourceId: user.id,
      metadata: { applicationKey: payload.app, viaMfa: true },
      ipAddress: ctx.ipAddress,
    });

    return result;
  }

  async refresh(refreshTokenPlaintext: string, ctx: RequestContext): Promise<AuthResult> {
    const hash = this.tokens.hashRefreshToken(refreshTokenPlaintext);
    const active = await sessionsRepo.findActiveSessionByRefreshTokenHash(hash);

    if (!active) {
      // Replay detection: a token that exists but is revoked/expired being
      // reused is a signal the refresh token chain may be compromised —
      // revoke every session of that user defensively (ADR-0003).
      const anyState = await sessionsRepo.findSessionByRefreshTokenHashAnyState(hash);
      if (anyState?.revoked_at) {
        await sessionsRepo.revokeAllUserSessions(anyState.user_id);
        await auditRepo.appendAuditEvent({
          actorType: "system",
          actorId: anyState.user_id,
          action: "auth.refresh_replay_detected",
          resourceType: "session",
          resourceId: anyState.id,
          ipAddress: ctx.ipAddress,
        });
      }
      throw new UnauthorizedException("Sessão inválida ou expirada");
    }

    const user = await usersRepo.findUserById(active.user_id);
    if (!user || !user.is_active) {
      throw new UnauthorizedException("Sessão inválida ou expirada");
    }

    await sessionsRepo.touchSession(active.id);
    const result = await this.issueTokens(user, active.application_key, ctx, active.id);

    await auditRepo.appendAuditEvent({
      actorType: "user",
      actorId: user.id,
      action: "auth.refresh",
      resourceType: "session",
      resourceId: active.id,
      ipAddress: ctx.ipAddress,
    });

    return result;
  }

  async logout(refreshTokenPlaintext: string, ctx: RequestContext): Promise<void> {
    const hash = this.tokens.hashRefreshToken(refreshTokenPlaintext);
    const session = await sessionsRepo.findActiveSessionByRefreshTokenHash(hash);
    if (!session) return; // idempotent — already logged out
    await sessionsRepo.revokeSession(session.id);
    await auditRepo.appendAuditEvent({
      actorType: "user",
      actorId: session.user_id,
      action: "auth.logout",
      resourceType: "session",
      resourceId: session.id,
      ipAddress: ctx.ipAddress,
    });
  }

  async getProfile(userId: string) {
    const user = await usersRepo.findUserById(userId);
    if (!user || !user.is_active) throw new UnauthorizedException();
    const permissions = await resolvePermissions(user.role_key);
    const applications = await usersRepo.getUserApplications(user.id);
    return {
      user: toPublicUser(user),
      permissions: permissions.superAdmin
        ? ("ALL" as const)
        : permissions.grants.map((g) => ({ resource: g.resource, action: g.action, scope: g.scope })),
      applications,
    };
  }

  private async issueTokens(
    user: User,
    applicationKey: "core" | "reseller" | "subscriber",
    ctx: RequestContext,
    replacesSessionId?: string,
  ): Promise<AuthResult> {
    const access = this.tokens.signAccessToken({ sub: user.id, app: applicationKey });
    const refresh = this.tokens.generateRefreshToken();

    await sessionsRepo.createSession({
      userId: user.id,
      applicationKey,
      refreshTokenHash: refresh.hash,
      expiresAt: refresh.expiresAt,
      ipAddress: ctx.ipAddress,
      userAgent: ctx.userAgent,
      replacesSessionId,
    });

    return {
      accessToken: access.token,
      expiresIn: access.expiresIn,
      refreshToken: refresh.plaintext,
      user: toPublicUser(user),
    };
  }

  /**
   * Always resolves the same way whether or not the email is registered —
   * same anti-enumeration discipline as login (eden.md §4.1). If the
   * account exists (and is active), stages a reset token and emails a
   * link; the mailer is fail-soft (packages/integrations), so a delivery
   * failure never surfaces as an error here either.
   */
  async forgotPassword(email: string, ctx: RequestContext): Promise<void> {
    const user = await usersRepo.findUserByEmail(email);
    if (!user) return;

    const plaintextToken = randomBytes(32).toString("hex");
    const tokenHash = hashResetToken(plaintextToken);
    const expiresAt = new Date(Date.now() + RESET_TOKEN_TTL_MS);
    await usersRepo.setResetToken(user.id, tokenHash, expiresAt);

    const resetUrl = `${this.env.PUBLIC_BASE_URL ?? "http://localhost:3001"}/reset-password?token=${plaintextToken}`;
    await sendMail({
      to: user.email,
      subject: "EDEN — Redefinição de senha",
      html: `
        <p>Olá${user.full_name ? `, ${user.full_name}` : ""},</p>
        <p>Recebemos um pedido para redefinir sua senha no EDEN. Se foi você, clique no link abaixo (válido por 1 hora):</p>
        <p><a href="${resetUrl}">${resetUrl}</a></p>
        <p>Se você não pediu essa redefinição, pode ignorar este e-mail — sua senha continua a mesma.</p>
      `,
    });

    await auditRepo.appendAuditEvent({
      actorType: "user",
      actorId: user.id,
      action: "auth.password_reset_requested",
      resourceType: "user",
      resourceId: user.id,
      ipAddress: ctx.ipAddress,
    });
  }

  /**
   * Consumes a reset token issued by forgotPassword(). The token is
   * cleared whether or not this call succeeds past validation, so a
   * token can never be replayed — and every existing session is revoked
   * (a password change invalidates any session that might have been
   * established under the old, possibly-compromised credential).
   */
  async resetPassword(plaintextToken: string, newPassword: string, ctx: RequestContext): Promise<void> {
    const tokenHash = hashResetToken(plaintextToken);
    const user = await usersRepo.findUserByResetTokenHash(tokenHash);
    if (!user) {
      throw new BadRequestException("Token inválido ou expirado");
    }

    const { hash, algoVersion } = await this.passwords.hash(newPassword);
    await usersRepo.updateUserPassword(user.id, hash, algoVersion);
    await usersRepo.clearResetToken(user.id);
    await sessionsRepo.revokeAllUserSessions(user.id);

    await auditRepo.appendAuditEvent({
      actorType: "user",
      actorId: user.id,
      action: "auth.password_reset_completed",
      resourceType: "user",
      resourceId: user.id,
      ipAddress: ctx.ipAddress,
    });
  }
}