managarten/services/mana-matrix-bot/internal/services/backend.go

package services

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

// BackendClient is a generic HTTP client for calling NestJS backends.
type BackendClient struct {
	baseURL    string
	httpClient *http.Client
}

// NewBackendClient creates a new backend client.
func NewBackendClient(baseURL string) *BackendClient {
	return &BackendClient{
		baseURL: baseURL,
		httpClient: &http.Client{
			Timeout: 30 * time.Second,
		},
	}
}

// Get sends a GET request and decodes the JSON response.
func (c *BackendClient) Get(ctx context.Context, path string, token string, result any) error {
	req, err := http.NewRequestWithContext(ctx, "GET", c.baseURL+path, nil)
	if err != nil {
		return err
	}
	if token != "" {
		req.Header.Set("Authorization", "Bearer "+token)
	}
	req.Header.Set("Accept", "application/json")

	resp, err := c.httpClient.Do(req)
	if err != nil {
		return fmt.Errorf("backend GET %s: %w", path, err)
	}
	defer resp.Body.Close()

	if resp.StatusCode >= 400 {
		body, _ := io.ReadAll(resp.Body)
		return fmt.Errorf("backend GET %s: %d %s", path, resp.StatusCode, string(body))
	}

	if result != nil {
		return json.NewDecoder(resp.Body).Decode(result)
	}
	return nil
}

// Post sends a POST request with a JSON body and decodes the response.
func (c *BackendClient) Post(ctx context.Context, path string, token string, body any, result any) error {
	var reqBody io.Reader
	if body != nil {
		data, err := json.Marshal(body)
		if err != nil {
			return fmt.Errorf("marshal body: %w", err)
		}
		reqBody = bytes.NewReader(data)
	}

	req, err := http.NewRequestWithContext(ctx, "POST", c.baseURL+path, reqBody)
	if err != nil {
		return err
	}
	if token != "" {
		req.Header.Set("Authorization", "Bearer "+token)
	}
	req.Header.Set("Content-Type", "application/json")
	req.Header.Set("Accept", "application/json")

	resp, err := c.httpClient.Do(req)
	if err != nil {
		return fmt.Errorf("backend POST %s: %w", path, err)
	}
	defer resp.Body.Close()

	if resp.StatusCode >= 400 {
		body, _ := io.ReadAll(resp.Body)
		return fmt.Errorf("backend POST %s: %d %s", path, resp.StatusCode, string(body))
	}

	if result != nil {
		return json.NewDecoder(resp.Body).Decode(result)
	}
	return nil
}

// Put sends a PUT request with a JSON body.
func (c *BackendClient) Put(ctx context.Context, path string, token string, body any, result any) error {
	var reqBody io.Reader
	if body != nil {
		data, err := json.Marshal(body)
		if err != nil {
			return fmt.Errorf("marshal body: %w", err)
		}
		reqBody = bytes.NewReader(data)
	}

	req, err := http.NewRequestWithContext(ctx, "PUT", c.baseURL+path, reqBody)
	if err != nil {
		return err
	}
	if token != "" {
		req.Header.Set("Authorization", "Bearer "+token)
	}
	req.Header.Set("Content-Type", "application/json")
	req.Header.Set("Accept", "application/json")

	resp, err := c.httpClient.Do(req)
	if err != nil {
		return fmt.Errorf("backend PUT %s: %w", path, err)
	}
	defer resp.Body.Close()

	if resp.StatusCode >= 400 {
		respBody, _ := io.ReadAll(resp.Body)
		return fmt.Errorf("backend PUT %s: %d %s", path, resp.StatusCode, string(respBody))
	}

	if result != nil {
		return json.NewDecoder(resp.Body).Decode(result)
	}
	return nil
}

// Delete sends a DELETE request.
func (c *BackendClient) Delete(ctx context.Context, path string, token string) error {
	req, err := http.NewRequestWithContext(ctx, "DELETE", c.baseURL+path, nil)
	if err != nil {
		return err
	}
	if token != "" {
		req.Header.Set("Authorization", "Bearer "+token)
	}

	resp, err := c.httpClient.Do(req)
	if err != nil {
		return fmt.Errorf("backend DELETE %s: %w", path, err)
	}
	defer resp.Body.Close()

	if resp.StatusCode >= 400 {
		body, _ := io.ReadAll(resp.Body)
		return fmt.Errorf("backend DELETE %s: %d %s", path, resp.StatusCode, string(body))
	}
	return nil
}