package com.rit.whatsapp.service;

import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
import org.springframework.http.HttpEntity;
import org.springframework.http.HttpHeaders;
import org.springframework.http.MediaType;
import org.springframework.http.ResponseEntity;
import org.springframework.stereotype.Service;
import org.springframework.web.client.RestTemplate;

import java.util.HashMap;
import java.util.Map;

@Service
public class ImsApiService {

    private final String BASE_URL = "https://ims-api.sidharthprabhu.co.in";
    private final RestTemplate restTemplate;
    private final ObjectMapper objectMapper;

    public ImsApiService() {
        this.restTemplate = new RestTemplate();
        this.objectMapper = new ObjectMapper();
    }

    /**
     * Authenticates the user against the real IMS backend.
     * @param imsId The user ID
     * @param passcode The passcode
     * @return The API session token if successful, null otherwise.
     */
    public String authenticate(String imsId, String passcode) {
        String url = BASE_URL + "/api/auth/login";

        HttpHeaders headers = new HttpHeaders();
        headers.setContentType(MediaType.APPLICATION_JSON);

        Map<String, String> requestBody = new HashMap<>();
        requestBody.put("username", imsId);
        requestBody.put("password", passcode);

        HttpEntity<Map<String, String>> request = new HttpEntity<>(requestBody, headers);

        try {
            ResponseEntity<String> response = restTemplate.postForEntity(url, request, String.class);
            if (response.getStatusCode().is2xxSuccessful() && response.getBody() != null) {
                JsonNode rootNode = objectMapper.readTree(response.getBody());
                if (rootNode.has("success") && rootNode.get("success").asBoolean()) {
                    if (rootNode.has("session")) {
                        return rootNode.get("session").asText();
                    }
                }
            }
        } catch (Exception e) {
            System.err.println("Failed to authenticate with IMS API: " + e.getMessage());
        }
        
        return null;
    }

    private String fetchFromIms(String endpoint, String token) {
        String url = BASE_URL + endpoint;
        HttpHeaders headers = new HttpHeaders();
        headers.setBearerAuth(token);
        
        HttpEntity<String> request = new HttpEntity<>(headers);
        
        try {
            ResponseEntity<String> response = restTemplate.exchange(url, org.springframework.http.HttpMethod.GET, request, String.class);
            if (response.getStatusCode().is2xxSuccessful()) {
                return response.getBody();
            }
        } catch (Exception e) {
            System.err.println("Failed to fetch from IMS API (" + endpoint + "): " + e.getMessage());
        }
        return null;
    }

    public String getAttendance(String token) {
        return fetchFromIms("/api/student/attendance", token);
    }

    public String getTimetable(String token) {
        return fetchFromIms("/api/student/timetable", token);
    }

    public String getResults(String token, int semester) {
        return fetchFromIms("/api/student/results?semester=" + semester, token);
    }

    public void logout(String token) {
        String url = BASE_URL + "/api/auth/logout";
        HttpHeaders headers = new HttpHeaders();
        headers.setBearerAuth(token);
        
        HttpEntity<String> request = new HttpEntity<>(headers);
        
        try {
            restTemplate.postForEntity(url, request, String.class);
        } catch (Exception e) {
            System.err.println("Failed to logout from IMS API: " + e.getMessage());
        }
    }
}