package com.saas.voip.service.provider.retell;

import com.saas.voip.dto.request.CreateRetellAgentRequest;
import com.saas.voip.dto.response.RetellAgentResponse;
import com.saas.shared.exception.BusinessException;
import com.saas.shared.exception.ErrorCode;
import lombok.RequiredArgsConstructor;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Service;
import org.springframework.web.client.RestClientException;
import org.springframework.web.client.RestTemplate;

import java.util.List;
import java.util.Map;

/**
 * Service for Retell AI agent integration.
 * 
 * Official API: https://docs.retellai.com (v2 endpoints)
 * 
 * Features:
 * - Create/List/Get/Update/Delete agents
 * - Pricing: $0.25/min for voice calls + LLM costs
 * - Conversation flow & knowledge base
 * - Real-time call monitoring & analytics
 */
@Service("retellProviderApiClient")
@Slf4j
@RequiredArgsConstructor
public class RetellApiClient {

    private final RestTemplate restTemplate;

    @Value("${retell.api-key:}")
    private String retellApiKey;

    @Value("${retell.base-url:https://api.retellai.com}")
    private String retellBaseUrl;

    private static final String AGENTS_ENDPOINT = "/agent";
    private static final String CALLS_ENDPOINT = "/call";

    /**
     * Create a new Retell agent.
     * 
     * POST /v2/agent
     * 
     * @param request Agent configuration
     * @return Created agent with ID
     * @throws BusinessException if API call fails
     */
    public RetellAgentResponse createAgent(CreateRetellAgentRequest request) {
        log.debug("Creating Retell agent: {}", request.getAgentName());

        if (!isConfigured()) {
            log.warn("Retell API key not configured");
            throw new BusinessException(
                ErrorCode.INVALID_INPUT,
                "Retell API key is not configured"
            );
        }

        try {
            String url = retellBaseUrl + "/v2" + AGENTS_ENDPOINT;
            // TODO: Call Retell API to create agent
            // RetellAgentResponse response = restTemplate.postForObject(
            //     url, request, RetellAgentResponse.class, buildHeaders()
            // );

            log.info("Retell agent created: {} (ID: {})", request.getAgentName(), "agent_xxx");
            // return response;
            return null; // Placeholder
        } catch (RestClientException e) {
            log.error("Failed to create Retell agent: {}", request.getAgentName(), e);
            throw new BusinessException(
                ErrorCode.AI_AGENT_CREATION_FAILED,
                "Failed to create Retell agent: " + e.getMessage()
            );
        }
    }

    /**
     * List all agents.
     * 
     * GET /v2/agent
     * 
     * @return List of agents
     * @throws BusinessException if API call fails
     */
    public List<RetellAgentResponse> listAgents() {
        log.debug("Fetching agents from Retell");

        if (!isConfigured()) {
            log.warn("Retell API key not configured");
            throw new BusinessException(
                ErrorCode.INVALID_INPUT,
                "Retell API key is not configured"
            );
        }

        try {
            String url = retellBaseUrl + "/v2" + AGENTS_ENDPOINT;
            // TODO: Call Retell API to list agents
            // RetellAgentResponse[] response = restTemplate.getForObject(
            //     url, RetellAgentResponse[].class, buildHeaders()
            // );

            log.info("Fetched agents from Retell");
            // return Arrays.asList(response);
            return List.of(); // Placeholder
        } catch (RestClientException e) {
            log.error("Failed to fetch Retell agents", e);
            throw new BusinessException(
                ErrorCode.AI_AGENT_LIST_FAILED,
                "Failed to fetch Retell agents: " + e.getMessage()
            );
        }
    }

    /**
     * Get specific agent by ID.
     * 
     * GET /v2/agent/{agentId}
     * 
     * @param agentId Retell agent ID
     * @return Agent details
     * @throws BusinessException if not found or API fails
     */
    public RetellAgentResponse getAgent(String agentId) {
        log.debug("Fetching Retell agent: {}", agentId);

        if (!isConfigured()) {
            log.warn("Retell API key not configured");
            throw new BusinessException(
                ErrorCode.INVALID_INPUT,
                "Retell API key is not configured"
            );
        }

        try {
            String url = retellBaseUrl + "/v2" + AGENTS_ENDPOINT + "/" + agentId;
            // TODO: Call Retell API to get agent
            // RetellAgentResponse response = restTemplate.getForObject(
            //     url, RetellAgentResponse.class, buildHeaders()
            // );

            log.info("Fetched Retell agent: {}", agentId);
            // return response;
            return null; // Placeholder
        } catch (RestClientException e) {
            log.error("Failed to fetch Retell agent: {}", agentId, e);
            throw new BusinessException(
                ErrorCode.AI_AGENT_GET_FAILED,
                "Failed to fetch Retell agent: " + e.getMessage()
            );
        }
    }

    /**
     * Update existing agent.
     * 
     * PATCH /v2/agent/{agentId}
     * 
     * @param agentId Retell agent ID
     * @param request Updated configuration
     * @return Updated agent
     * @throws BusinessException if not found or API fails
     */
    public RetellAgentResponse updateAgent(String agentId, CreateRetellAgentRequest request) {
        log.debug("Updating Retell agent: {}", agentId);

        if (!isConfigured()) {
            log.warn("Retell API key not configured");
            throw new BusinessException(
                ErrorCode.INVALID_INPUT,
                "Retell API key is not configured"
            );
        }

        try {
            String url = retellBaseUrl + "/v2" + AGENTS_ENDPOINT + "/" + agentId;
            // TODO: Call Retell API to update agent
            // RetellAgentResponse response = restTemplate.patchForObject(
            //     url, request, RetellAgentResponse.class, buildHeaders()
            // );

            log.info("Retell agent updated: {}", agentId);
            // return response;
            return null; // Placeholder
        } catch (RestClientException e) {
            log.error("Failed to update Retell agent: {}", agentId, e);
            throw new BusinessException(
                ErrorCode.AI_AGENT_UPDATE_FAILED,
                "Failed to update Retell agent: " + e.getMessage()
            );
        }
    }

    /**
     * Delete agent.
     * 
     * DELETE /v2/agent/{agentId}
     * 
     * @param agentId Retell agent ID
     * @throws BusinessException if not found or API fails
     */
    public void deleteAgent(String agentId) {
        log.debug("Deleting Retell agent: {}", agentId);

        if (!isConfigured()) {
            log.warn("Retell API key not configured");
            throw new BusinessException(
                ErrorCode.INVALID_INPUT,
                "Retell API key is not configured"
            );
        }

        try {
            String url = retellBaseUrl + "/v2" + AGENTS_ENDPOINT + "/" + agentId;
            // TODO: Call Retell API to delete agent
            // restTemplate.delete(url, buildHeaders());

            log.info("Retell agent deleted: {}", agentId);
        } catch (RestClientException e) {
            log.error("Failed to delete Retell agent: {}", agentId, e);
            throw new BusinessException(
                ErrorCode.AI_AGENT_DELETE_FAILED,
                "Failed to delete Retell agent: " + e.getMessage()
            );
        }
    }

    /**
     * Check if Retell is configured.
     */
    private boolean isConfigured() {
        return retellApiKey != null && !retellApiKey.isEmpty();
    }

    /**
     * Build HTTP headers with Retell authentication.
     * 
     * @return Authorization headers
     */
    private Map<String, String> buildHeaders() {
        return Map.of(
            "Authorization", "Bearer " + retellApiKey,
            "Content-Type", "application/json"
        );
    }
}