review-bot/gitea/client.go

// Package gitea provides a client for the Gitea API.
// It supports pull request operations, file content retrieval,
// and review submission.
package gitea

import (
	"bytes"
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"log/slog"
	"math"
	"net"
	"net/http"
	"net/url"
	"strings"
	"syscall"
	"time"
)

// APIError represents an HTTP error response from the Gitea API.
// It carries the status code so callers can distinguish between
// different failure modes (e.g. 404 vs 500).
type APIError struct {
	StatusCode int
	Body       string
}

func (e *APIError) Error() string {
	body := e.Body
	if len(body) > 200 {
		body = body[:200] + "...(truncated)"
	}
	return fmt.Sprintf("HTTP %d: %s", e.StatusCode, body)
}

// IsNotFound reports whether an error is an API 404 response.
func IsNotFound(err error) bool {
	var apiErr *APIError
	return errors.As(err, &apiErr) && apiErr.StatusCode == http.StatusNotFound
}

// IsServerError reports whether an error is an API 5xx response.
func IsServerError(err error) bool {
	var apiErr *APIError
	return errors.As(err, &apiErr) && apiErr.StatusCode >= 500 && apiErr.StatusCode < 600
}

// DefaultMaxDiffSize is the default maximum diff size in bytes (10 MB).
const DefaultMaxDiffSize = 10 * 1024 * 1024

// ErrDiffTooLarge is returned when a PR diff exceeds the configured MaxDiffSize.
var ErrDiffTooLarge = errors.New("diff size exceeds maximum allowed size")

// Client interacts with the Gitea API.
// A Client is safe for concurrent use by multiple goroutines.
type Client struct {
	baseURL string
	token   string
	http    *http.Client

	// RetryBackoff defines the delays between retry attempts.
	// RetryBackoff[i] is the delay before attempt i+1 (after attempt i fails).
	// If nil, defaults to {1s, 2s}. Set to shorter durations in tests.
	//
	// This field must be configured before the first request is made.
	// Modifying it while requests are in flight is not safe.
	RetryBackoff []time.Duration

	// MaxDiffSize is the maximum number of bytes allowed when fetching a PR diff.
	// If zero, defaults to DefaultMaxDiffSize (10 MB). Set to any negative value
	// (or math.MaxInt64) to disable the limit.
	//
	// This field must be configured before the first request is made.
	// Modifying it while requests are in flight is not safe.
	MaxDiffSize int64
}

// defaultCheckRedirect is the redirect policy used by NewClient.
// NOTE: This function is intentionally duplicated in github/client.go (and vice versa)
// because the packages are separate. Changes here must be mirrored there.
// It rejects HTTPS->HTTP protocol downgrades (to prevent plaintext leakage)
// and cross-host redirects (to prevent following responses from untrusted
// endpoints). Same-host, same-or-upgraded-scheme redirects are allowed.
func defaultCheckRedirect(req *http.Request, via []*http.Request) error {
	if len(via) >= 10 {
		return fmt.Errorf("stopped after 10 redirects")
	}
	// Guard for direct invocation in tests and any future callers;
	// net/http guarantees len(via) >= 1 during actual redirects.
	if len(via) == 0 {
		return nil
	}
	prev := via[len(via)-1]
	// Reject protocol downgrade: HTTPS->HTTP leaks request metadata over plaintext.
	if prev.URL.Scheme == "https" && req.URL.Scheme == "http" {
		return fmt.Errorf("refusing redirect: HTTPS to HTTP downgrade (%s -> %s)", prev.URL.Host, req.URL.Host)
	}
	// Reject cross-host redirect entirely to avoid consuming responses
	// from untrusted endpoints.
	if req.URL.Host != prev.URL.Host {
		return fmt.Errorf("refusing redirect: cross-host (%s -> %s)", prev.URL.Host, req.URL.Host)
	}
	return nil
}

// NewClient creates a new Gitea API client.
func NewClient(baseURL, token string) *Client {
	return &Client{
		baseURL: strings.TrimRight(baseURL, "/"),
		token:   token,
		http: &http.Client{
			Timeout:       30 * time.Second,
			CheckRedirect: defaultCheckRedirect,
		},
	}
}

// SetHTTPClient sets the underlying HTTP client used for requests.
// This is intended for test setup only to inject mock transports; it must be
// called before any goroutines issue requests.
//
// Passing nil restores the default client (30s timeout + redirect-rejecting
// CheckRedirect policy matching NewClient).
//
// Callers providing a non-nil client are responsible for configuring a safe
// CheckRedirect policy. Without one, the default net/http behavior will follow
// redirects and may forward the Authorization header to untrusted hosts.
func (c *Client) SetHTTPClient(hc *http.Client) {
	if hc == nil {
		hc = &http.Client{
			Timeout:       30 * time.Second,
			CheckRedirect: defaultCheckRedirect,
		}
	}
	c.http = hc
}

// PullRequest holds relevant PR metadata.
type PullRequest struct {
	Title string `json:"title"`
	Body  string `json:"body"`
	Head  struct {
		Sha string `json:"sha"`
		Ref string `json:"ref"`
	} `json:"head"`
}

// CommitStatus represents a single CI status entry.
type CommitStatus struct {
	Status      string `json:"status"`
	Context     string `json:"context"`
	Description string `json:"description"`
	TargetURL   string `json:"target_url"`
}

// ChangedFile represents a file modified in a PR.
type ChangedFile struct {
	Filename string `json:"filename"`
	Status   string `json:"status"`
}

// ReviewComment represents an inline comment to attach to a review.
type ReviewComment struct {
	ID          int64  `json:"id,omitempty"`
	Path        string `json:"path"`
	NewPosition int64  `json:"new_position"`
	Body        string `json:"body"`
}

// GetPullRequest fetches PR metadata.
func (c *Client) GetPullRequest(ctx context.Context, owner, repo string, number int) (*PullRequest, error) {
	reqURL := fmt.Sprintf("%s/api/v1/repos/%s/%s/pulls/%d", c.baseURL, url.PathEscape(owner), url.PathEscape(repo), number)
	body, err := c.doGet(ctx, reqURL)
	if err != nil {
		return nil, fmt.Errorf("fetch PR: %w", err)
	}
	var pr PullRequest
	if err := json.Unmarshal(body, &pr); err != nil {
		return nil, fmt.Errorf("parse PR JSON: %w", err)
	}
	return &pr, nil
}

// GetPullRequestDiff fetches the unified diff for a PR.
// It enforces MaxDiffSize to prevent unbounded memory allocation.
// Returns ErrDiffTooLarge if the diff exceeds the configured limit.
func (c *Client) GetPullRequestDiff(ctx context.Context, owner, repo string, number int) (string, error) {
	reqURL := fmt.Sprintf("%s/api/v1/repos/%s/%s/pulls/%d.diff", c.baseURL, url.PathEscape(owner), url.PathEscape(repo), number)

	maxSize := c.MaxDiffSize
	if maxSize == 0 {
		maxSize = DefaultMaxDiffSize
	}

	// When the limit is disabled (negative) or set to math.MaxInt64 (which
	// would overflow the +1 detection and silently disable enforcement),
	// use the standard unlimited doGet path.
	if maxSize < 0 || maxSize == math.MaxInt64 {
		body, err := c.doGet(ctx, reqURL)
		if err != nil {
			return "", fmt.Errorf("fetch diff: %w", err)
		}
		return string(body), nil
	}

	body, err := c.doGetLimited(ctx, reqURL, maxSize)
	if err != nil {
		return "", fmt.Errorf("fetch diff: %w", err)
	}
	return string(body), nil
}

// GetPullRequestFiles fetches the list of files changed in a PR.
func (c *Client) GetPullRequestFiles(ctx context.Context, owner, repo string, number int) ([]ChangedFile, error) {
	reqURL := fmt.Sprintf("%s/api/v1/repos/%s/%s/pulls/%d/files", c.baseURL, url.PathEscape(owner), url.PathEscape(repo), number)
	body, err := c.doGet(ctx, reqURL)
	if err != nil {
		return nil, fmt.Errorf("fetch PR files: %w", err)
	}
	var files []ChangedFile
	if err := json.Unmarshal(body, &files); err != nil {
		return nil, fmt.Errorf("parse PR files JSON: %w", err)
	}
	return files, nil
}

// GetCommitStatuses fetches CI statuses for a commit SHA.
func (c *Client) GetCommitStatuses(ctx context.Context, owner, repo, sha string) ([]CommitStatus, error) {
	reqURL := fmt.Sprintf("%s/api/v1/repos/%s/%s/commits/%s/statuses", c.baseURL, url.PathEscape(owner), url.PathEscape(repo), url.PathEscape(sha))
	body, err := c.doGet(ctx, reqURL)
	if err != nil {
		return nil, fmt.Errorf("fetch commit statuses: %w", err)
	}
	var statuses []CommitStatus
	if err := json.Unmarshal(body, &statuses); err != nil {
		return nil, fmt.Errorf("parse statuses JSON: %w", err)
	}
	return statuses, nil
}

// GetFileContent fetches a file from the default branch of a repo.
func (c *Client) GetFileContent(ctx context.Context, owner, repo, filepath string) (string, error) {
	reqURL := fmt.Sprintf("%s/api/v1/repos/%s/%s/raw/%s", c.baseURL, url.PathEscape(owner), url.PathEscape(repo), escapePath(filepath))
	body, err := c.doGet(ctx, reqURL)
	if err != nil {
		return "", fmt.Errorf("fetch file %s: %w", filepath, err)
	}
	return string(body), nil
}

// GetFileContentRef fetches a file from a specific ref (branch/tag/sha) in a repo.
func (c *Client) GetFileContentRef(ctx context.Context, owner, repo, filepath, ref string) (string, error) {
	reqURL := fmt.Sprintf("%s/api/v1/repos/%s/%s/raw/%s?ref=%s", c.baseURL, url.PathEscape(owner), url.PathEscape(repo), escapePath(filepath), url.QueryEscape(ref))
	body, err := c.doGet(ctx, reqURL)
	if err != nil {
		return "", fmt.Errorf("fetch file %s@%s: %w", filepath, ref, err)
	}
	return string(body), nil
}

// PostReview submits a review to a PR and returns the created review.
// event should be one of "APPROVED", "REQUEST_CHANGES", or "COMMENT".
// commitID anchors the review to a specific commit SHA. If empty, Gitea
// defaults to the current PR head.
// comments are optional inline comments attached to specific lines.
func (c *Client) PostReview(ctx context.Context, owner, repo string, number int, event, body, commitID string, comments []ReviewComment) (*Review, error) {
	reqURL := fmt.Sprintf("%s/api/v1/repos/%s/%s/pulls/%d/reviews", c.baseURL, url.PathEscape(owner), url.PathEscape(repo), number)

	payload := struct {
		Body     string          `json:"body"`
		Event    string          `json:"event"`
		CommitID string          `json:"commit_id,omitempty"`
		Comments []ReviewComment `json:"comments,omitempty"`
	}{
		Body:     body,
		Event:    event,
		CommitID: commitID,
		Comments: comments,
	}

	data, err := json.Marshal(payload)
	if err != nil {
		return nil, fmt.Errorf("marshal review payload: %w", err)
	}

	req, err := http.NewRequestWithContext(ctx, http.MethodPost, reqURL, bytes.NewReader(data))
	if err != nil {
		return nil, fmt.Errorf("create review request: %w", err)
	}
	req.Header.Set("Authorization", "token "+c.token)
	req.Header.Set("Content-Type", "application/json")

	resp, err := c.http.Do(req)
	if err != nil {
		return nil, fmt.Errorf("post review: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
		respBody, _ := io.ReadAll(resp.Body)
		return nil, fmt.Errorf("post review failed (status %d): %s", resp.StatusCode, string(respBody))
	}

	respBody, err := io.ReadAll(resp.Body)
	if err != nil {
		return nil, fmt.Errorf("read review response: %w", err)
	}
	var review Review
	if err := json.Unmarshal(respBody, &review); err != nil {
		return nil, fmt.Errorf("parse review response: %w", err)
	}
	return &review, nil
}

// isTemporaryNetError reports whether err is a temporary network error worth retrying.
// This includes connection refused, network unreachable, connection reset, and DNS
// timeouts. It explicitly excludes permanent errors like permission denied or
// "no such host" DNS failures.
func isTemporaryNetError(err error) bool {
	if err == nil {
		return false
	}

	// Check for OpError and inspect the underlying syscall error.
	// Not all OpErrors are transient — permission denied, for example, is permanent.
	var opErr *net.OpError
	if errors.As(err, &opErr) {
		return isRetriableSyscallError(opErr.Err)
	}

	// DNS errors: only retry on timeout, not on "no such host" which is permanent.
	var dnsErr *net.DNSError
	if errors.As(err, &dnsErr) {
		return dnsErr.IsTimeout
	}

	// Check for net.Error with Timeout() (Temporary is deprecated)
	var netErr net.Error
	if errors.As(err, &netErr) {
		return netErr.Timeout()
	}

	return false
}

// isRetriableSyscallError reports whether the underlying error from a net.OpError
// is a transient syscall error worth retrying.
func isRetriableSyscallError(err error) bool {
	if err == nil {
		return false
	}

	// Check for syscall.Errno directly or wrapped
	var errno syscall.Errno
	if errors.As(err, &errno) {
		switch errno {
		case syscall.ECONNREFUSED, // connection refused — server not listening
			syscall.ECONNRESET,   // connection reset by peer
			syscall.ENETUNREACH,  // network unreachable
			syscall.EHOSTUNREACH, // host unreachable
			syscall.ETIMEDOUT:    // connection timed out
			return true
		default:
			// EACCES, EPERM, etc. are permanent — don't retry
			return false
		}
	}

	// If we can't identify the specific syscall error, be conservative and retry.
	// This handles wrapped errors or platform-specific error types.
	// The retry count is limited, so erring on the side of retrying is safe.
	return true
}

// redactURL strips query parameters and userinfo credentials from a URL for
// safe logging. This prevents accidental exposure of sensitive data (tokens in
// query strings, or user:pass in the authority) in log output.
func redactURL(rawURL string) string {
	parsed, err := url.Parse(rawURL)
	if err != nil {
		// If we cannot parse it, return a safe placeholder rather than
		// potentially logging something sensitive.
		return "[invalid URL]"
	}
	if parsed.User != nil {
		parsed.User = url.User("REDACTED")
	}
	if parsed.RawQuery != "" {
		parsed.RawQuery = "[redacted]"
	}
	return parsed.String()
}

// sanitizeErrorForLog returns a loggable version of an error that omits
// potentially sensitive content like response bodies. For APIError, only
// the status code is included; for other errors, the type is preserved.
func sanitizeErrorForLog(err error) string {
	if err == nil {
		return "<nil>"
	}
	var apiErr *APIError
	if errors.As(err, &apiErr) {
		return fmt.Sprintf("HTTP %d", apiErr.StatusCode)
	}
	return err.Error()
}

// doGetWithReader performs an HTTP GET request with retry on 5xx errors and
// temporary network errors. Retries up to 3 times with exponential backoff
// (1s, 2s delays by default; configurable via Client.RetryBackoff for testing).
// The readBody function is called with the response body on success (2xx) and
// is responsible for reading and closing it.
func (c *Client) doGetWithReader(ctx context.Context, reqURL string, readBody func(io.ReadCloser) ([]byte, error)) ([]byte, error) {
	const maxAttempts = 3
	// backoff[i] is the delay before attempt i+1 (i.e., after attempt i fails).
	// First attempt (i=0) has no delay; retries wait 1s then 2s by default.
	backoff := c.RetryBackoff
	if backoff == nil {
		backoff = []time.Duration{1 * time.Second, 2 * time.Second}
	}

	// maxErrorBodyBytes limits how much of an error response body we read
	// to protect against malicious servers sending unbounded data.
	const maxErrorBodyBytes = 64 * 1024 // 64 KB

	var lastErr error
	for attempt := 0; attempt < maxAttempts; attempt++ {
		if attempt > 0 {
			// Determine delay: use backoff slice if available, otherwise retry immediately.
			// An empty RetryBackoff slice means "retry without delay" — this is intentional
			// as the caller explicitly configured no delays.
			var delay time.Duration
			if attempt-1 < len(backoff) {
				delay = backoff[attempt-1]
			}

			if delay > 0 {
				slog.Warn("retrying request after error",
					"attempt", attempt+1,
					"url", redactURL(reqURL),
					"delay", delay.String(),
					"lastError", sanitizeErrorForLog(lastErr))

				timer := time.NewTimer(delay)
				select {
				case <-timer.C:
				case <-ctx.Done():
					timer.Stop()
					return nil, ctx.Err()
				}
			}
		}

		req, err := http.NewRequestWithContext(ctx, http.MethodGet, reqURL, nil)
		if err != nil {
			return nil, err
		}
		req.Header.Set("Authorization", "token "+c.token)

		resp, err := c.http.Do(req)
		if err != nil {
			// Always capture the error for consistent return at loop end.
			// This ensures both network errors and HTTP 5xx return lastErr.
			lastErr = err

			// Only retry temporary network errors when attempts remain.
			if attempt < maxAttempts-1 && isTemporaryNetError(err) {
				slog.Warn("temporary network error, will retry",
					"attempt", attempt+1,
					"url", redactURL(reqURL),
					"error", err)
				continue
			}
			// Non-retryable network error or final attempt exhausted.
			return nil, lastErr
		}
		if resp.StatusCode >= 200 && resp.StatusCode < 300 {
			return readBody(resp.Body)
		}

		// Error path: limit how much we read from potentially malicious server
		errBody, _ := io.ReadAll(io.LimitReader(resp.Body, maxErrorBodyBytes))
		resp.Body.Close()

		lastErr = &APIError{StatusCode: resp.StatusCode, Body: string(errBody)}

		// Only retry on 5xx server errors
		if resp.StatusCode < 500 || resp.StatusCode >= 600 {
			return nil, lastErr
		}
	}

	return nil, lastErr
}

// doGet performs an HTTP GET request with retry, reading the full response body.
func (c *Client) doGet(ctx context.Context, reqURL string) ([]byte, error) {
	return c.doGetWithReader(ctx, reqURL, func(body io.ReadCloser) ([]byte, error) {
		defer body.Close()
		return io.ReadAll(body)
	})
}

// doGetLimited performs an HTTP GET request with retry but enforces a maximum
// response body size. Returns ErrDiffTooLarge if the response exceeds maxBytes.
// It reads maxBytes+1 (clamped to avoid overflow) to detect truncation without
// buffering the entire body.
func (c *Client) doGetLimited(ctx context.Context, reqURL string, maxBytes int64) ([]byte, error) {
	return c.doGetWithReader(ctx, reqURL, func(body io.ReadCloser) ([]byte, error) {
		defer body.Close()
		// Read up to maxBytes+1 to detect overflow.
		// Clamp to prevent integer overflow when maxBytes == math.MaxInt64.
		limitBytes := maxBytes + 1
		if limitBytes <= 0 {
			limitBytes = math.MaxInt64
		}
		limited := io.LimitReader(body, limitBytes)
		data, err := io.ReadAll(limited)
		if err != nil {
			return nil, err
		}
		if int64(len(data)) > maxBytes {
			return nil, fmt.Errorf("%w: response exceeds %d bytes", ErrDiffTooLarge, maxBytes)
		}
		return data, nil
	})
}

// escapePath escapes each segment of a relative file path for use in URLs.
// Slashes are preserved as path separators; other special characters are escaped.
// Input should be a relative path (no leading slash). Already-encoded segments
// will be double-encoded, which is the desired behavior for user-provided paths.
func escapePath(p string) string {
	parts := strings.Split(p, "/")
	for i, part := range parts {
		parts[i] = url.PathEscape(part)
	}
	return strings.Join(parts, "/")
}

// ContentEntry represents a file or directory entry from the contents API.
type ContentEntry struct {
	Name string `json:"name"`
	Path string `json:"path"`
	Type string `json:"type"` // "file" or "dir"
}

// ListContents lists files and directories at a given path in a repo.
// Pass an empty path to list the repository root.
// If the path points to a file (not a directory), Gitea returns a single
// object instead of an array; this method normalizes both cases to a slice.
func (c *Client) ListContents(ctx context.Context, owner, repo, path string) ([]ContentEntry, error) {
	// Normalize "." to empty string — Gitea API rejects "." with 500
	if path == "." {
		path = ""
	}
	var reqURL string
	if path == "" {
		reqURL = fmt.Sprintf("%s/api/v1/repos/%s/%s/contents", c.baseURL, url.PathEscape(owner), url.PathEscape(repo))
	} else {
		reqURL = fmt.Sprintf("%s/api/v1/repos/%s/%s/contents/%s", c.baseURL, url.PathEscape(owner), url.PathEscape(repo), escapePath(path))
	}
	body, err := c.doGet(ctx, reqURL)
	if err != nil {
		return nil, fmt.Errorf("list contents %s: %w", path, err)
	}
	var entries []ContentEntry
	if err := json.Unmarshal(body, &entries); err != nil {
		// Gitea returns a single object (not an array) when path is a file
		var single ContentEntry
		if err2 := json.Unmarshal(body, &single); err2 != nil {
			return nil, fmt.Errorf("parse contents JSON: %w", err)
		}
		// Guard against empty/malformed responses
		if single.Name == "" && single.Path == "" {
			return nil, fmt.Errorf("parse contents JSON: empty response for path %q", path)
		}
		entries = []ContentEntry{single}
	}
	return entries, nil
}

// GetAllFilesInPath recursively fetches all file contents under a path.
// If the path is a file, returns just that file's content.
// If the path is a directory, recursively fetches all files within it.
func (c *Client) GetAllFilesInPath(ctx context.Context, owner, repo, path string) (map[string]string, error) {
	results := make(map[string]string)

	// Try listing as directory first
	entries, err := c.ListContents(ctx, owner, repo, path)
	if err != nil {
		// Only fall back to single-file fetch on 404 (path is a file, not a dir).
		// Propagate all other errors (auth failures, server errors, rate limits).
		if !IsNotFound(err) {
			return nil, fmt.Errorf("list contents %q: %w", path, err)
		}
		// 404 means the path might be a file — try fetching directly
		content, fileErr := c.GetFileContent(ctx, owner, repo, path)
		if fileErr != nil {
			return nil, fmt.Errorf("path %q is neither a file nor directory: %w", path, fileErr)
		}
		results[path] = content
		return results, nil
	}

	for _, entry := range entries {
		switch entry.Type {
		case "file":
			content, err := c.GetFileContent(ctx, owner, repo, entry.Path)
			if err != nil {
				slog.Warn("could not fetch file from patterns repo", "file", entry.Path, "error", err)
				continue
			}
			results[entry.Path] = content
		case "dir":
			subResults, err := c.GetAllFilesInPath(ctx, owner, repo, entry.Path)
			if err != nil {
				slog.Warn("could not recurse into directory", "dir", entry.Path, "error", err)
				continue
			}
			for k, v := range subResults {
				results[k] = v
			}
		}
	}
	return results, nil
}

// Review represents a pull request review from the Gitea API.
type Review struct {
	ID   int64  `json:"id"`
	Body string `json:"body"`
	User struct {
		Login string `json:"login"`
	} `json:"user"`
	State    string `json:"state"`
	Stale    bool   `json:"stale"`
	CommitID string `json:"commit_id"`
}

// ListReviews returns all reviews on a pull request.
// Paginates through all pages to ensure no reviews are missed.
func (c *Client) ListReviews(ctx context.Context, owner, repo string, number int) ([]Review, error) {
	const pageSize = 50
	var all []Review
	for page := 1; ; page++ {
		reqURL := fmt.Sprintf("%s/api/v1/repos/%s/%s/pulls/%d/reviews?limit=%d&page=%d",
			c.baseURL,
			url.PathEscape(owner),
			url.PathEscape(repo),
			number,
			pageSize,
			page)
		body, err := c.doGet(ctx, reqURL)
		if err != nil {
			return nil, fmt.Errorf("list reviews (page %d): %w", page, err)
		}
		var batch []Review
		if err := json.Unmarshal(body, &batch); err != nil {
			return nil, fmt.Errorf("parse reviews (page %d): %w", page, err)
		}
		all = append(all, batch...)
		if len(batch) < pageSize {
			break
		}
	}
	return all, nil
}

// DeleteReview deletes a review by ID. The token must belong to the review author.
func (c *Client) DeleteReview(ctx context.Context, owner, repo string, number int, reviewID int64) error {
	reqURL := fmt.Sprintf("%s/api/v1/repos/%s/%s/pulls/%d/reviews/%d",
		c.baseURL,
		url.PathEscape(owner),
		url.PathEscape(repo),
		number,
		reviewID)

	req, err := http.NewRequestWithContext(ctx, http.MethodDelete, reqURL, nil)
	if err != nil {
		return fmt.Errorf("create delete request: %w", err)
	}
	req.Header.Set("Authorization", "token "+c.token)

	resp, err := c.http.Do(req)
	if err != nil {
		return fmt.Errorf("delete review: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
		respBody, _ := io.ReadAll(resp.Body)
		return fmt.Errorf("delete review failed (status %d): %s", resp.StatusCode, string(respBody))
	}
	return nil
}

// TimelineEvent represents an entry from the issue timeline API.
type TimelineEvent struct {
	ID   int64  `json:"id"`
	Type string `json:"type"`
	Body string `json:"body"`
	User struct {
		Login string `json:"login"`
	} `json:"user"`
}

// GetTimelineReviewCommentID finds the comment ID for a review body by
// scanning the issue timeline for a review event containing the sentinel.
func (c *Client) GetTimelineReviewCommentID(ctx context.Context, owner, repo string, number int, sentinel string) (int64, error) {
	const pageSize = 50
	for page := 1; ; page++ {
		reqURL := fmt.Sprintf("%s/api/v1/repos/%s/%s/issues/%d/timeline?limit=%d&page=%d",
			c.baseURL,
			url.PathEscape(owner),
			url.PathEscape(repo),
			number,
			pageSize,
			page)
		body, err := c.doGet(ctx, reqURL)
		if err != nil {
			return 0, fmt.Errorf("get timeline (page %d): %w", page, err)
		}
		var events []TimelineEvent
		if err := json.Unmarshal(body, &events); err != nil {
			return 0, fmt.Errorf("parse timeline (page %d): %w", page, err)
		}
		for _, ev := range events {
			if ev.Type == "review" && strings.Contains(ev.Body, sentinel) {
				return ev.ID, nil
			}
		}
		if len(events) < pageSize {
			break
		}
	}
	return 0, fmt.Errorf("no timeline event found with sentinel")
}

// GetTimelineReviewCommentIDForReview finds the timeline comment ID for a
// specific review by matching its body content in the timeline.
func (c *Client) GetTimelineReviewCommentIDForReview(ctx context.Context, owner, repo string, number int, reviewID int64) (int64, error) {
	// Use the reviews API to get the review body, then find in timeline
	reqURL := fmt.Sprintf("%s/api/v1/repos/%s/%s/pulls/%d/reviews/%d",
		c.baseURL,
		url.PathEscape(owner),
		url.PathEscape(repo),
		number,
		reviewID)
	body, err := c.doGet(ctx, reqURL)
	if err != nil {
		return 0, fmt.Errorf("get review %d: %w", reviewID, err)
	}
	var review struct {
		Body string `json:"body"`
		User struct {
			Login string `json:"login"`
		} `json:"user"`
	}
	if err := json.Unmarshal(body, &review); err != nil {
		return 0, fmt.Errorf("parse review %d: %w", reviewID, err)
	}
	if review.Body == "" {
		return 0, fmt.Errorf("review %d has empty body", reviewID)
	}

	// Use a prefix for matching (handles minor trailing whitespace differences)
	matchPrefix := review.Body
	if len(matchPrefix) > 200 {
		matchPrefix = matchPrefix[:200]
	}

	const pageSize = 50
	for page := 1; ; page++ {
		timelineURL := fmt.Sprintf("%s/api/v1/repos/%s/%s/issues/%d/timeline?limit=%d&page=%d",
			c.baseURL,
			url.PathEscape(owner),
			url.PathEscape(repo),
			number,
			pageSize,
			page)
		tlBody, err := c.doGet(ctx, timelineURL)
		if err != nil {
			return 0, fmt.Errorf("get timeline (page %d): %w", page, err)
		}
		var events []TimelineEvent
		if err := json.Unmarshal(tlBody, &events); err != nil {
			return 0, fmt.Errorf("parse timeline (page %d): %w", page, err)
		}
		for _, ev := range events {
			if ev.Type == "review" && ev.User.Login == review.User.Login && strings.HasPrefix(ev.Body, matchPrefix) {
				return ev.ID, nil
			}
		}
		if len(events) < pageSize {
			break
		}
	}
	return 0, fmt.Errorf("no timeline event found for review %d", reviewID)
}

// EditComment updates the body of an issue/review comment.
func (c *Client) EditComment(ctx context.Context, owner, repo string, commentID int64, newBody string) error {
	reqURL := fmt.Sprintf("%s/api/v1/repos/%s/%s/issues/comments/%d",
		c.baseURL,
		url.PathEscape(owner),
		url.PathEscape(repo),
		commentID)

	payload := struct {
		Body string `json:"body"`
	}{Body: newBody}
	data, err := json.Marshal(payload)
	if err != nil {
		return fmt.Errorf("marshal edit payload: %w", err)
	}

	req, err := http.NewRequestWithContext(ctx, http.MethodPatch, reqURL, bytes.NewReader(data))
	if err != nil {
		return fmt.Errorf("create edit request: %w", err)
	}
	req.Header.Set("Authorization", "token "+c.token)
	req.Header.Set("Content-Type", "application/json")

	resp, err := c.http.Do(req)
	if err != nil {
		return fmt.Errorf("edit comment: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		body, _ := io.ReadAll(resp.Body)
		return fmt.Errorf("edit comment failed (status %d): %s", resp.StatusCode, body)
	}
	return nil
}

// GetAuthenticatedUser returns the login of the user authenticated by the token.
func (c *Client) GetAuthenticatedUser(ctx context.Context) (string, error) {
	reqURL := fmt.Sprintf("%s/api/v1/user", c.baseURL)
	body, err := c.doGet(ctx, reqURL)
	if err != nil {
		return "", fmt.Errorf("get authenticated user: %w", err)
	}
	var result struct {
		Login string `json:"login"`
	}
	if err := json.Unmarshal(body, &result); err != nil {
		return "", fmt.Errorf("parse user response: %w", err)
	}
	return result.Login, nil
}

// RequestReviewer adds the given user as a requested reviewer on a pull request.
// This is idempotent — requesting an already-requested reviewer is a no-op.
func (c *Client) RequestReviewer(ctx context.Context, owner, repo string, number int, reviewer string) error {
	reqURL := fmt.Sprintf("%s/api/v1/repos/%s/%s/pulls/%d/requested_reviewers",
		c.baseURL,
		url.PathEscape(owner),
		url.PathEscape(repo),
		number)

	payload := struct {
		Reviewers []string `json:"reviewers"`
	}{Reviewers: []string{reviewer}}
	data, err := json.Marshal(payload)
	if err != nil {
		return fmt.Errorf("marshal reviewer request: %w", err)
	}

	req, err := http.NewRequestWithContext(ctx, http.MethodPost, reqURL, bytes.NewReader(data))
	if err != nil {
		return fmt.Errorf("create reviewer request: %w", err)
	}
	req.Header.Set("Authorization", "token "+c.token)
	req.Header.Set("Content-Type", "application/json")

	resp, err := c.http.Do(req)
	if err != nil {
		return fmt.Errorf("request reviewer: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK && resp.StatusCode != http.StatusCreated && resp.StatusCode != http.StatusNoContent {
		body, _ := io.ReadAll(io.LimitReader(resp.Body, 256))
		return fmt.Errorf("request reviewer failed (status %d): %s", resp.StatusCode, body)
	}
	return nil
}

// ListReviewComments returns the inline comments attached to a specific review.
// Paginates through all pages.
func (c *Client) ListReviewComments(ctx context.Context, owner, repo string, prNumber int, reviewID int64) ([]ReviewComment, error) {
	const pageSize = 50
	var all []ReviewComment
	for page := 1; ; page++ {
		reqURL := fmt.Sprintf("%s/api/v1/repos/%s/%s/pulls/%d/reviews/%d/comments?limit=%d&page=%d",
			c.baseURL,
			url.PathEscape(owner),
			url.PathEscape(repo),
			prNumber,
			reviewID,
			pageSize,
			page)
		body, err := c.doGet(ctx, reqURL)
		if err != nil {
			return nil, fmt.Errorf("list review comments (page %d): %w", page, err)
		}
		var batch []ReviewComment
		if err := json.Unmarshal(body, &batch); err != nil {
			return nil, fmt.Errorf("parse review comments (page %d): %w", page, err)
		}
		all = append(all, batch...)
		if len(batch) < pageSize {
			break
		}
	}
	return all, nil
}

// ResolveComment marks an inline review comment as resolved.
func (c *Client) ResolveComment(ctx context.Context, owner, repo string, commentID int64) error {
	reqURL := fmt.Sprintf("%s/api/v1/repos/%s/%s/pulls/comments/%d/resolve",
		c.baseURL,
		url.PathEscape(owner),
		url.PathEscape(repo),
		commentID)

	req, err := http.NewRequestWithContext(ctx, http.MethodPost, reqURL, nil)
	if err != nil {
		return fmt.Errorf("create resolve request: %w", err)
	}
	req.Header.Set("Authorization", "token "+c.token)

	resp, err := c.http.Do(req)
	if err != nil {
		return fmt.Errorf("resolve comment: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK && resp.StatusCode != http.StatusCreated && resp.StatusCode != http.StatusNoContent {
		body, _ := io.ReadAll(io.LimitReader(resp.Body, 256))
		return fmt.Errorf("resolve comment failed (status %d): %s", resp.StatusCode, body)
	}
	return nil
}