import axios, { AxiosInstance, AxiosError, InternalAxiosRequestConfig } from 'axios';
import {
  User,
  LoginRequest,
  RegisterRequest,
  AuthTokens,
  Medication,
  CreateMedicationRequest,
  UpdateMedicationRequest,
  DrugInteraction,
  CheckInteractionRequest,
  CheckNewMedicationRequest,
  CreateHealthStatRequest,
  ApiError,
  DoseLog,
  LogDoseRequest,
  AdherenceStats,
  MedicationWireResponse,
  AppointmentWireResponse,
  ProfileWireResponse,
  CreateProfileRequest,
  UpdateProfileRequest,
  HealthStatWireResponse,
  UpdateHealthStatRequest,
  EncryptedFieldWire,
  CreateAppointmentRequest,
  UpdateAppointmentRequest,
} from '../types/api';

// API base URL. In dev this is "/api", proxied by the Vite dev server to the
// backend (see vite.config.ts). For a production build pointed at a remote
// backend, set VITE_API_URL to the absolute URL at build time.
const API_BASE = import.meta.env.VITE_API_URL || '/api';

class ApiService {
  private client: AxiosInstance;
  private token: string | null = null;
  private refreshToken: string | null = null;
  private refreshing: Promise<string | null> | null = null;

  constructor() {
    this.client = axios.create({
      baseURL: API_BASE,
      headers: {
        'Content-Type': 'application/json',
      },
    });

    // Load tokens from localStorage (single source of truth shared with the
    // zustand auth store's persist).
    this.token = localStorage.getItem('token');
    this.refreshToken = localStorage.getItem('refresh_token');
    if (this.token) {
      this.setAuthHeader(this.token);
    }

    // Request interceptor: attach the access token.
    this.client.interceptors.request.use(
      (config) => {
        if (this.token) {
          config.headers.Authorization = `Bearer ${this.token}`;
        }
        return config;
      },
      (error) => Promise.reject(error),
    );

    // Response interceptor: on 401, attempt ONE silent refresh; if it fails,
    // clear credentials and redirect to /login.
    this.client.interceptors.response.use(
      (response) => response,
      async (error: AxiosError) => {
        const original = error.config as InternalAxiosRequestConfig & {
          _retried?: boolean;
          _noRefresh?: boolean;
        };

        if (
          error.response?.status === 401 &&
          !original._retried &&
          !original._noRefresh &&
          this.refreshToken
        ) {
          original._retried = true;
          const newToken = await this.doRefresh();
          if (newToken) {
            original.headers!.Authorization = `Bearer ${newToken}`;
            return this.client.request(original);
          }
          // Refresh failed: drop credentials and bounce to login.
          this.clearCredentials();
          if (window.location.pathname !== '/login') {
            window.location.href = '/login';
          }
          return Promise.reject(this.handleError(error));
        }

        return Promise.reject(this.handleError(error));
      },
    );
  }

  private handleError(error: AxiosError): ApiError {
    if (error.response) {
      const data = error.response.data as Record<string, unknown>;
      return {
        message:
          (data.error as string) ||
          (data.message as string) ||
          'An error occurred',
        code: String(error.response.status),
        details: data,
      };
    } else if (error.request) {
      return {
        message: 'No response from server',
        code: 'NETWORK_ERROR',
      };
    } else {
      return {
        message: error.message || 'Unknown error',
        code: 'UNKNOWN',
      };
    }
  }

  private setAuthHeader(token: string) {
    this.client.defaults.headers.common['Authorization'] = `Bearer ${token}`;
  }

  setTokens(accessToken: string, refreshToken: string) {
    this.token = accessToken;
    this.refreshToken = refreshToken;
    localStorage.setItem('token', accessToken);
    localStorage.setItem('refresh_token', refreshToken);
    this.setAuthHeader(accessToken);
  }

  setToken(token: string) {
    this.token = token;
    localStorage.setItem('token', token);
    this.setAuthHeader(token);
  }

  getToken(): string | null {
    return this.token;
  }

  getRefreshToken(): string | null {
    return this.refreshToken;
  }

  clearCredentials() {
    this.token = null;
    this.refreshToken = null;
    localStorage.removeItem('token');
    localStorage.removeItem('refresh_token');
    delete this.client.defaults.headers.common['Authorization'];
  }

  /** Log out: revoke the refresh token server-side, then clear local state. */
  async logout() {
    if (this.refreshToken) {
      try {
        await this.client.post('/auth/logout', { refresh_token: this.refreshToken });
      } catch {
        // Best-effort: even if the server call fails, drop local credentials.
      }
    }
    this.clearCredentials();
  }

  /** Perform a single in-flight refresh, deduped across concurrent requests. */
  private async doRefresh(): Promise<string | null> {
    if (this.refreshing) return this.refreshing;
    if (!this.refreshToken) return null;

    this.refreshing = (async () => {
      try {
        const response = await this.client.post<AuthTokens>('/auth/refresh', {
          refresh_token: this.refreshToken,
        });
        const { token, refresh_token } = response.data;
        this.setTokens(token, refresh_token);
        return token;
      } catch {
        return null;
      } finally {
        this.refreshing = null;
      }
    })();

    return this.refreshing;
  }

  // ---- Authentication ----

  async login(email: string, _password: string): Promise<AuthTokens> {
    // _password is used in the request body below; renamed only to satisfy the
    // interface signature kept for store compatibility.
    const response = await this.client.post<AuthTokens>('/auth/login', {
      email,
      password: _password,
    });
    this.setTokens(response.data.token, response.data.refresh_token);
    return response.data;
  }

  async register(data: RegisterRequest): Promise<AuthTokens> {
    const response = await this.client.post<AuthTokens>('/auth/register', data);
    this.setTokens(response.data.token, response.data.refresh_token);
    return response.data;
  }

  async getCurrentUser(): Promise<User> {
    const response = await this.client.get<User>('/users/me');
    return response.data;
  }

  // ---- Recovery (zero-knowledge) ----

  async getRecoveryInfo(email: string): Promise<{ recovery_enabled: boolean; recovery_wrapped_dek?: string; recovery_wrapped_dek_iv?: string }> {
    const response = await this.client.get('/auth/recovery-info', { params: { email } });
    return response.data;
  }

  async recoverPassword(email: string, recoveryProof: string, newAuthSecret: string, newWrappedDek?: string, newWrappedDekIv?: string): Promise<void> {
    await this.client.post('/auth/recover-password', {
      email,
      recovery_phrase: recoveryProof,
      new_password: newAuthSecret,
      new_wrapped_dek: newWrappedDek,
      new_wrapped_dek_iv: newWrappedDekIv,
    });
  }

  // ---- Profiles (Phase A2: multi-profile, per-profile DEKs) ----

  async listProfiles(): Promise<ProfileWireResponse[]> {
    const response = await this.client.get<ProfileWireResponse[]>('/profiles');
    return response.data;
  }

  async createProfile(req: CreateProfileRequest): Promise<ProfileWireResponse> {
    const response = await this.client.post<ProfileWireResponse>('/profiles', req);
    return response.data;
  }

  async getProfile(profileId: string): Promise<ProfileWireResponse> {
    const response = await this.client.get<ProfileWireResponse>(`/profiles/${profileId}`);
    return response.data;
  }

  async updateProfile(profileId: string, req: UpdateProfileRequest): Promise<ProfileWireResponse> {
    const response = await this.client.put<ProfileWireResponse>(`/profiles/${profileId}`, req);
    return response.data;
  }

  async deleteProfile(profileId: string): Promise<void> {
    await this.client.delete(`/profiles/${profileId}`);
  }

  // ---- Medications (zero-knowledge: opaque encrypted blobs) ----

  async getMedications(profileId?: string): Promise<MedicationWireResponse[]> {
    const params = profileId ? { profile_id: profileId } : undefined;
    const response = await this.client.get<MedicationWireResponse[]>('/medications', { params });
    return response.data;
  }

  async getMedication(id: string): Promise<MedicationWireResponse> {
    const response = await this.client.get<MedicationWireResponse>(`/medications/${id}`);
    return response.data;
  }

  async createMedication(data: CreateMedicationRequest): Promise<MedicationWireResponse> {
    const response = await this.client.post<MedicationWireResponse>('/medications', data);
    return response.data;
  }

  async updateMedication(id: string, data: UpdateMedicationRequest): Promise<MedicationWireResponse> {
    const response = await this.client.post<MedicationWireResponse>(`/medications/${id}`, data);
    return response.data;
  }

  async deleteMedication(id: string): Promise<void> {
    await this.client.post(`/medications/${id}/delete`);
  }

  // ---- Dose logging + adherence (not encrypted — counts/flags only) ----

  async logDose(medicationId: string, req: LogDoseRequest): Promise<DoseLog> {
    const response = await this.client.post<DoseLog>(`/medications/${medicationId}/log`, req);
    return response.data;
  }

  async getAdherence(medicationId: string): Promise<AdherenceStats> {
    const response = await this.client.get<AdherenceStats>(`/medications/${medicationId}/adherence`);
    return response.data;
  }

  // ---- Appointments (zero-knowledge: opaque encrypted blobs) ----

  async getAppointments(status?: string, profileId?: string): Promise<AppointmentWireResponse[]> {
    const params: Record<string, string> = {};
    if (status) params.status = status;
    if (profileId) params.profile_id = profileId;
    const response = await this.client.get<AppointmentWireResponse[]>('/appointments', {
      params: Object.keys(params).length ? params : undefined,
    });
    return response.data;
  }

  async getAppointment(id: string): Promise<AppointmentWireResponse> {
    const response = await this.client.get<AppointmentWireResponse>(`/appointments/${id}`);
    return response.data;
  }

  async createAppointment(data: CreateAppointmentRequest): Promise<AppointmentWireResponse> {
    const response = await this.client.post<AppointmentWireResponse>('/appointments', data);
    return response.data;
  }

  async updateAppointment(id: string, data: UpdateAppointmentRequest): Promise<AppointmentWireResponse> {
    const response = await this.client.post<AppointmentWireResponse>(`/appointments/${id}`, data);
    return response.data;
  }

  async deleteAppointment(id: string): Promise<void> {
    await this.client.post(`/appointments/${id}/delete`);
  }

  // ---- Drug Interactions (Phase 2.8) ----

  async checkInteractions(medications: string[]): Promise<DrugInteraction[]> {
    const response = await this.client.post<DrugInteraction[]>('/interactions/check', {
      medications,
    });
    return response.data;
  }

  async checkNewMedication(name: string, dosage: string): Promise<DrugInteraction[]> {
    const response = await this.client.post<DrugInteraction[]>('/interactions/check-new', {
      name,
      dosage,
    });
    return response.data;
  }

  // ---- Health Statistics (zero-knowledge: opaque encrypted blobs) ----

  async getHealthStats(profileId?: string): Promise<HealthStatWireResponse[]> {
    const params = profileId ? { profile_id: profileId } : undefined;
    const response = await this.client.get<HealthStatWireResponse[]>('/health-stats', { params });
    return response.data;
  }

  async getHealthStat(id: string): Promise<HealthStatWireResponse> {
    const response = await this.client.get<HealthStatWireResponse>(`/health-stats/${id}`);
    return response.data;
  }

  async createHealthStat(data: CreateHealthStatRequest): Promise<HealthStatWireResponse> {
    const response = await this.client.post<HealthStatWireResponse>('/health-stats', data);
    return response.data;
  }

  async updateHealthStat(id: string, data: UpdateHealthStatRequest): Promise<HealthStatWireResponse> {
    const response = await this.client.put<HealthStatWireResponse>(`/health-stats/${id}`, data);
    return response.data;
  }

  async deleteHealthStat(id: string): Promise<void> {
    await this.client.delete(`/health-stats/${id}`);
  }

  // NOTE: lab-results endpoints are intentionally absent — the backend has no
  // /lab-results routes yet. The LabResult type stays in types/api.ts for when
  // those routes land.
}

// Export singleton instance
export const apiService = new ApiService();
export default apiService;

// Satisfy the unused-import linter for types referenced only via generics above.
export type {
  LoginRequest,
  CheckInteractionRequest,
  CheckNewMedicationRequest,
};