Implement HTTP request helper with retry logic

Add internal HTTP helpers to client.go:
- doRequest(ctx, method, path, body, result) for all API calls
- doGet, doPost, doPut, doDelete convenience methods
- Automatic authentication check before each request
- JSON marshaling of request body and unmarshaling of response

Retry logic with exponential backoff:
- Retries on HTTP 429 (Too Many Requests)
- Retries on HTTP 5xx (Server Errors)
- Retries on network errors (timeout, connection reset)
- Respects context cancellation during retry delays
- Configurable via RetryConfig (MaxRetries, BaseDelay, MaxDelay, Jitter)

Debug logging via slog for request/response tracking.

Closes checkvist-api-8u6

.beads/issues.jsonl

@@ -10,7 +10,7 @@
 {"id":"checkvist-api-8bn","title":"Write unit tests for Client and Auth","description":"Create client_test.go with tests using httptest.Server:\n- TestNewClient_Defaults\n- TestNewClient_WithOptions\n- TestAuthenticate_Success\n- TestAuthenticate_InvalidCredentials\n- TestAuthenticate_2FA\n- TestTokenRefresh_Auto\n- TestTokenRefresh_Manual\n- TestCurrentUser\n- TestRetryLogic_429\n- TestRetryLogic_5xx\n- TestRetryLogic_NetworkError\nUse table-driven tests. Create testdata/auth/ fixtures.","status":"open","priority":0,"issue_type":"task","owner":"mail@oliverjakoubek.de","created_at":"2026-01-14T12:31:36.964610587+01:00","created_by":"Oliver Jakoubek","updated_at":"2026-01-14T12:31:36.964610587+01:00","dependencies":[{"issue_id":"checkvist-api-8bn","depends_on_id":"checkvist-api-lpn","type":"blocks","created_at":"2026-01-14T12:33:12.783142853+01:00","created_by":"Oliver Jakoubek"},{"issue_id":"checkvist-api-8bn","depends_on_id":"checkvist-api-8u6","type":"blocks","created_at":"2026-01-14T12:33:13.232028837+01:00","created_by":"Oliver Jakoubek"}]}
 {"id":"checkvist-api-8jh","title":"Implement repeating tasks configuration","description":"Add P2 (nice-to-have) repeat support to TaskBuilder:\n- WithRepeat(pattern string) *TaskBuilder\nSupport Checkvist smart syntax for repeats.\nDocument common patterns in GoDoc.","status":"open","priority":2,"issue_type":"feature","owner":"mail@oliverjakoubek.de","created_at":"2026-01-14T12:30:56.826106108+01:00","created_by":"Oliver Jakoubek","updated_at":"2026-01-14T12:30:56.826106108+01:00","dependencies":[{"issue_id":"checkvist-api-8jh","depends_on_id":"checkvist-api-tjk","type":"blocks","created_at":"2026-01-14T12:33:03.159849575+01:00","created_by":"Oliver Jakoubek"}]}
 {"id":"checkvist-api-8q3","title":"Set up Mage build targets","description":"Create magefiles/magefile.go with:\n- Test() - run go test -v ./...\n- Coverage() - run go test -coverprofile=coverage.out ./...\n- Lint() - run staticcheck ./...\n- Fmt() - run gofmt -w .\n- Check() - run all quality checks (fmt, vet, staticcheck, test)\nEnsure magefiles has its own go.mod importing magefile.org/mage","status":"open","priority":0,"issue_type":"task","owner":"mail@oliverjakoubek.de","created_at":"2026-01-14T12:31:09.228450637+01:00","created_by":"Oliver Jakoubek","updated_at":"2026-01-14T12:31:09.228450637+01:00","dependencies":[{"issue_id":"checkvist-api-8q3","depends_on_id":"checkvist-api-5wr","type":"blocks","created_at":"2026-01-14T12:32:48.556022687+01:00","created_by":"Oliver Jakoubek"}]}
-{"id":"checkvist-api-8u6","title":"Implement HTTP request helper with retry logic","description":"Add internal HTTP helper to client.go:\n- doRequest(ctx, method, path, body) helper for all API calls\n- Automatic authentication check before requests\n- JSON marshaling/unmarshaling\n- Exponential backoff retry for:\n  - HTTP 429 (Too Many Requests)\n  - HTTP 5xx (Server Errors)\n  - Network errors (timeout, connection reset)\n- Respect context cancellation\n- Optional debug logging of requests/responses via slog","status":"open","priority":0,"issue_type":"task","owner":"mail@oliverjakoubek.de","created_at":"2026-01-14T12:31:08.780244392+01:00","created_by":"Oliver Jakoubek","updated_at":"2026-01-14T12:31:08.780244392+01:00","dependencies":[{"issue_id":"checkvist-api-8u6","depends_on_id":"checkvist-api-ymg","type":"blocks","created_at":"2026-01-14T12:32:47.973194416+01:00","created_by":"Oliver Jakoubek"},{"issue_id":"checkvist-api-8u6","depends_on_id":"checkvist-api-mnh","type":"blocks","created_at":"2026-01-14T12:32:48.268500727+01:00","created_by":"Oliver Jakoubek"}]}
+{"id":"checkvist-api-8u6","title":"Implement HTTP request helper with retry logic","description":"Add internal HTTP helper to client.go:\n- doRequest(ctx, method, path, body) helper for all API calls\n- Automatic authentication check before requests\n- JSON marshaling/unmarshaling\n- Exponential backoff retry for:\n  - HTTP 429 (Too Many Requests)\n  - HTTP 5xx (Server Errors)\n  - Network errors (timeout, connection reset)\n- Respect context cancellation\n- Optional debug logging of requests/responses via slog","status":"closed","priority":0,"issue_type":"task","owner":"mail@oliverjakoubek.de","created_at":"2026-01-14T12:31:08.780244392+01:00","created_by":"Oliver Jakoubek","updated_at":"2026-01-14T13:27:52.914675409+01:00","closed_at":"2026-01-14T13:27:52.914675409+01:00","close_reason":"Closed","dependencies":[{"issue_id":"checkvist-api-8u6","depends_on_id":"checkvist-api-ymg","type":"blocks","created_at":"2026-01-14T12:32:47.973194416+01:00","created_by":"Oliver Jakoubek"},{"issue_id":"checkvist-api-8u6","depends_on_id":"checkvist-api-mnh","type":"blocks","created_at":"2026-01-14T12:32:48.268500727+01:00","created_by":"Oliver Jakoubek"}]}
 {"id":"checkvist-api-93m","title":"Create CHANGELOG","description":"Create CHANGELOG.md following Keep a Changelog format:\n- [Unreleased] section for ongoing work\n- Initial release preparation notes\n- Document all features implemented","status":"open","priority":0,"issue_type":"task","owner":"mail@oliverjakoubek.de","created_at":"2026-01-14T12:31:39.009748936+01:00","created_by":"Oliver Jakoubek","updated_at":"2026-01-14T12:31:39.009748936+01:00"}
 {"id":"checkvist-api-bbx","title":"Write unit tests for Notes","description":"Create notes_test.go with tests:\n- TestNotes_List\n- TestNotes_Create\n- TestNotes_Update\n- TestNotes_Delete\nUse table-driven tests. Create testdata/notes/ fixtures.","status":"open","priority":0,"issue_type":"task","owner":"mail@oliverjakoubek.de","created_at":"2026-01-14T12:31:37.829382141+01:00","created_by":"Oliver Jakoubek","updated_at":"2026-01-14T12:31:37.829382141+01:00","dependencies":[{"issue_id":"checkvist-api-bbx","depends_on_id":"checkvist-api-5ab","type":"blocks","created_at":"2026-01-14T12:33:14.119755191+01:00","created_by":"Oliver Jakoubek"}]}
 {"id":"checkvist-api-br3","title":"Core API Operations","description":"Phase 2: Implement CRUD operations for Checklists, Tasks, and Notes. All P0 (must-have) features for the library.","status":"open","priority":0,"issue_type":"epic","owner":"mail@oliverjakoubek.de","created_at":"2026-01-14T12:30:53.20627925+01:00","created_by":"Oliver Jakoubek","updated_at":"2026-01-14T12:30:53.20627925+01:00"}

client.go

@@ -11,11 +11,14 @@
 package checkvist
 
 import (
+	"bytes"
 	"context"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"io"
 	"log/slog"
+	"math/rand"
 	"net/http"
 	"net/url"
 	"strings"
@@ -255,3 +258,165 @@ func (c *Client) CurrentUser(ctx context.Context) (*User, error) {
 
 	return &user, nil
 }
+
+// doRequest performs an HTTP request with automatic authentication and retry logic.
+// It handles JSON marshaling of the request body and unmarshaling of the response.
+func (c *Client) doRequest(ctx context.Context, method, path string, body any, result any) error {
+	if err := c.ensureAuthenticated(ctx); err != nil {
+		return err
+	}
+
+	var bodyReader io.Reader
+	if body != nil {
+		bodyBytes, err := json.Marshal(body)
+		if err != nil {
+			return fmt.Errorf("marshaling request body: %w", err)
+		}
+		bodyReader = bytes.NewReader(bodyBytes)
+	}
+
+	var lastErr error
+	for attempt := 0; attempt <= c.retryConf.MaxRetries; attempt++ {
+		if attempt > 0 {
+			delay := c.calculateRetryDelay(attempt)
+			c.logger.Debug("retrying request",
+				"attempt", attempt,
+				"delay", delay,
+				"path", path,
+			)
+
+			select {
+			case <-ctx.Done():
+				return ctx.Err()
+			case <-time.After(delay):
+			}
+
+			// Reset body reader for retry
+			if body != nil {
+				bodyBytes, _ := json.Marshal(body)
+				bodyReader = bytes.NewReader(bodyBytes)
+			}
+		}
+
+		req, err := http.NewRequestWithContext(ctx, method, c.baseURL+path, bodyReader)
+		if err != nil {
+			return fmt.Errorf("creating request: %w", err)
+		}
+
+		req.Header.Set("X-Client-Token", c.getToken())
+		if body != nil {
+			req.Header.Set("Content-Type", "application/json")
+		}
+
+		c.logger.Debug("sending request",
+			"method", method,
+			"path", path,
+			"attempt", attempt,
+		)
+
+		resp, err := c.httpClient.Do(req)
+		if err != nil {
+			if c.shouldRetry(err, nil) {
+				lastErr = err
+				continue
+			}
+			return fmt.Errorf("request failed: %w", err)
+		}
+
+		respBody, err := io.ReadAll(resp.Body)
+		resp.Body.Close()
+
+		if err != nil {
+			lastErr = fmt.Errorf("reading response body: %w", err)
+			continue
+		}
+
+		c.logger.Debug("received response",
+			"status", resp.StatusCode,
+			"path", path,
+		)
+
+		if resp.StatusCode >= 200 && resp.StatusCode < 300 {
+			if result != nil && len(respBody) > 0 {
+				if err := json.Unmarshal(respBody, result); err != nil {
+					return fmt.Errorf("decoding response: %w", err)
+				}
+			}
+			return nil
+		}
+
+		apiErr := NewAPIError(resp, string(respBody))
+		if c.shouldRetry(nil, resp) {
+			lastErr = apiErr
+			continue
+		}
+
+		return apiErr
+	}
+
+	if lastErr != nil {
+		return fmt.Errorf("request failed after %d retries: %w", c.retryConf.MaxRetries, lastErr)
+	}
+	return errors.New("request failed: unknown error")
+}
+
+// shouldRetry determines if a request should be retried based on the error or response.
+func (c *Client) shouldRetry(err error, resp *http.Response) bool {
+	if err != nil {
+		// Retry on network errors (timeout, connection reset, etc.)
+		return true
+	}
+
+	if resp != nil {
+		// Retry on rate limiting
+		if resp.StatusCode == http.StatusTooManyRequests {
+			return true
+		}
+		// Retry on server errors
+		if resp.StatusCode >= 500 {
+			return true
+		}
+	}
+
+	return false
+}
+
+// calculateRetryDelay calculates the delay before the next retry attempt
+// using exponential backoff with optional jitter.
+func (c *Client) calculateRetryDelay(attempt int) time.Duration {
+	// Exponential backoff: baseDelay * 2^attempt
+	delay := c.retryConf.BaseDelay * time.Duration(1<<uint(attempt))
+
+	// Cap at max delay
+	if delay > c.retryConf.MaxDelay {
+		delay = c.retryConf.MaxDelay
+	}
+
+	// Add jitter (0-25% of delay)
+	if c.retryConf.Jitter {
+		jitter := time.Duration(rand.Int63n(int64(delay / 4)))
+		delay += jitter
+	}
+
+	return delay
+}
+
+// doGet performs a GET request and decodes the response into result.
+func (c *Client) doGet(ctx context.Context, path string, result any) error {
+	return c.doRequest(ctx, http.MethodGet, path, nil, result)
+}
+
+// doPost performs a POST request with a JSON body and decodes the response.
+func (c *Client) doPost(ctx context.Context, path string, body any, result any) error {
+	return c.doRequest(ctx, http.MethodPost, path, body, result)
+}
+
+// doPut performs a PUT request with a JSON body and decodes the response.
+func (c *Client) doPut(ctx context.Context, path string, body any, result any) error {
+	return c.doRequest(ctx, http.MethodPut, path, body, result)
+}
+
+// doDelete performs a DELETE request.
+func (c *Client) doDelete(ctx context.Context, path string) error {
+	return c.doRequest(ctx, http.MethodDelete, path, nil, nil)
+}