package notification

import (
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"time"
)

// HTTPClient defines the interface for HTTP operations
type HTTPClient interface {
	Do(req *http.Request) (*http.Response, error)
}

// Client represents the notification service HTTP client
type Client struct {
	config     *Config
	httpClient HTTPClient
	logger     Logger
}

// Logger interface for structured logging
type Logger interface {
	Info(msg string, fields map[string]interface{})
	Error(msg string, fields map[string]interface{})
	Debug(msg string, fields map[string]interface{})
	Warn(msg string, fields map[string]interface{})
}

// NewClient creates a new notification client
func NewClient(config *Config, logger Logger) (*Client, error) {
	if config == nil {
		config = DefaultConfig()
	}

	if err := config.Validate(); err != nil {
		return nil, fmt.Errorf("invalid configuration: %w", err)
	}

	httpClient := &http.Client{
		Timeout: config.Timeout,
	}

	return &Client{
		config:     config,
		httpClient: httpClient,
		logger:     logger,
	}, nil
}

// NewClientWithHTTPClient creates a new notification client with custom HTTP client
func NewClientWithHTTPClient(config *Config, httpClient HTTPClient, logger Logger) (*Client, error) {
	if config == nil {
		config = DefaultConfig()
	}

	if err := config.Validate(); err != nil {
		return nil, fmt.Errorf("invalid configuration: %w", err)
	}

	return &Client{
		config:     config,
		httpClient: httpClient,
		logger:     logger,
	}, nil
}

// SendNotification sends a notification request to the notification service
func (c *Client) SendNotification(ctx context.Context, req *NotificationRequest) (*NotificationResponse, error) {
	// Validate request
	if err := req.Validate(); err != nil {
		return nil, fmt.Errorf("request validation failed: %w", err)
	}

	var lastErr error
	start := time.Now()

	for attempt := 0; attempt <= c.config.RetryAttempts; attempt++ {
		if c.config.EnableLogging && c.logger != nil {
			c.logger.Debug("Sending notification request", map[string]interface{}{
				"attempt":    attempt + 1,
				"event_type": req.EventType,
				"user_id":    req.UserID,
				"base_url":   c.config.BaseURL,
			})
		}

		response, err := c.sendRequest(ctx, req)
		if err == nil {
			if c.config.EnableLogging && c.logger != nil {
				c.logger.Info("Notification sent successfully", map[string]interface{}{
					"event_type":   req.EventType,
					"user_id":      req.UserID,
					"attempts":     attempt + 1,
					"elapsed_time": time.Since(start).String(),
				})
			}
			return response, nil
		}

		lastErr = err

		// Log retry attempt
		if c.config.EnableLogging && c.logger != nil {
			c.logger.Warn("Notification attempt failed", map[string]interface{}{
				"attempt":    attempt + 1,
				"error":      err.Error(),
				"event_type": req.EventType,
				"user_id":    req.UserID,
			})
		}

		// Don't retry on certain errors
		if !c.shouldRetry(err) {
			break
		}

		// Don't sleep on last attempt
		if attempt < c.config.RetryAttempts {
			select {
			case <-ctx.Done():
				return nil, ctx.Err()
			case <-time.After(c.config.RetryDelay):
				// Continue to next attempt
			}
		}
	}

	if c.config.EnableLogging && c.logger != nil {
		c.logger.Error("All notification attempts failed", map[string]interface{}{
			"attempts":     c.config.RetryAttempts + 1,
			"elapsed_time": time.Since(start).String(),
			"last_error":   lastErr.Error(),
			"event_type":   req.EventType,
			"user_id":      req.UserID,
		})
	}

	return nil, ErrRetryExhausted{
		Attempts:    c.config.RetryAttempts + 1,
		LastError:   lastErr,
		ElapsedTime: time.Since(start).String(),
	}
}

// sendRequest performs the actual HTTP request
func (c *Client) sendRequest(ctx context.Context, req *NotificationRequest) (*NotificationResponse, error) {
	// Marshal request body
	requestBody, err := json.Marshal(req)
	if err != nil {
		return nil, fmt.Errorf("failed to marshal request: %w", err)
	}

	// Create HTTP request
	url := fmt.Sprintf("%s/api/v1/notifications", c.config.BaseURL)
	httpReq, err := http.NewRequestWithContext(ctx, "POST", url, bytes.NewBuffer(requestBody))
	if err != nil {
		return nil, fmt.Errorf("failed to create HTTP request: %w", err)
	}

	// Set headers
	httpReq.Header.Set("Content-Type", "application/json")
	httpReq.Header.Set("User-Agent", c.config.UserAgent)

	// Send request
	resp, err := c.httpClient.Do(httpReq)
	if err != nil {
		return nil, fmt.Errorf("HTTP request failed: %w", err)
	}
	defer resp.Body.Close()

	// Read response body
	body, err := io.ReadAll(resp.Body)
	if err != nil {
		return nil, fmt.Errorf("failed to read response body: %w", err)
	}

	// Handle non-2xx status codes
	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
		// Try to parse error response
		var errorResp NotificationErrorResponse
		if json.Unmarshal(body, &errorResp) == nil && errorResp.Error != "" {
			return nil, MapHTTPError(resp.StatusCode, errorResp.Error)
		}
		return nil, MapHTTPError(resp.StatusCode, string(body))
	}

	// Parse success response
	var notificationResp NotificationResponse
	if err := json.Unmarshal(body, &notificationResp); err != nil {
		return nil, fmt.Errorf("failed to unmarshal response: %w", err)
	}

	return &notificationResp, nil
}

// shouldRetry determines if a request should be retried based on the error
func (c *Client) shouldRetry(err error) bool {
	switch e := err.(type) {
	case ErrHTTP:
		// Retry on server errors (5xx) and certain client errors
		return e.StatusCode >= 500 || e.StatusCode == http.StatusTooManyRequests
	default:
		// Retry on network errors, timeouts, etc.
		return true
	}
}