fix(code_search): replace the fantasy REST endpoint with a real client-side grep

code_search was calling GET /api/v1/repos/{owner}/{repo}/search?type=code — an
endpoint that does not exist. Confirmed against a live Gitea 1.25.5 instance's
swagger spec: only /repos/search, /repos/issues/search, /topics/search etc are
real. Gitea's own web UI code search falls back to server-side `git grep`
because no Repository Indexer is enabled here, and that fallback is an
HTML-only route, not JSON API — so no REST endpoint exists to call, working or
not. Every call to code_search 404'd on the real server.

This went undetected because the existing tests mocked the fantasy endpoint
directly (asserting the request path was .../search?type=code and handing back
a canned JSON envelope) — a textbook case of tests validating a fake instead of
the real system, giving false confidence the tool worked.

SearchCode now does the search itself: resolves the default branch, walks the
tree (GetTree), and substring-matches q (case-insensitive, literal — not a
regex, to keep behavior predictable and avoid a ReDoS surface from
user-supplied input) against fetched file contents (GetFileContents) — the same
approach Gitea's own indexer-less fallback uses, just client-side. Bounded by:
- codeSearchMaxFiles (2000) — files scanned per call
- codeSearchMaxFileSize (512KB, checked via the tree listing's own Size field,
  before any fetch) — skip large blobs
- a binary-extension denylist checked before fetch, plus a null-byte content
  check after fetch, for extensions the denylist misses

Pagination is over the full sorted result set, recomputed each call (no
server-side index to page through incrementally) — acceptable for the repo
sizes this targets; documented as a known limitation, not a hidden footgun.

The tool layer (internal/tools/code_search.go) is UNCHANGED — SearchCode's
signature and the []CodeSearchHit contract are identical, so this is fully
isolated to the client layer + its tests.

Tests: match found in tree, case-insensitive matching, binary extension
skipped WITHOUT fetching (asserted via the fake's fetch log, not just absent
from results), oversized file skipped without fetching, null-byte content
skipped after fetching, pagination across a full sorted set, empty-query
validation — plus the tool-layer single-repo and fan-out tests rewritten
against the same real endpoints (GetRepo/GetTree/GetFileContents +
ListRepos), replacing their fantasy-endpoint fakes.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

internal/gitea/code_search.go

@@ -1,10 +1,13 @@
 package gitea
 
 import (
+	"bytes"
 	"context"
-	"encoding/json"
+	"encoding/base64"
 	"fmt"
-	"net/url"
+	"path"
+	"sort"
+	"strings"
 )
 
 type CodeSearchHit struct {
@@ -14,30 +17,147 @@ type CodeSearchHit struct {
 	Score   float64 `json:"score,omitempty"`
 }
 
-type codeSearchEnvelope struct {
-	Data []CodeSearchHit `json:"data"`
-	OK   bool            `json:"ok"`
+// codeSearchMaxFiles bounds how many files a single SearchCode call will fetch
+// and scan, so one call against a huge repo can't run indefinitely.
+const codeSearchMaxFiles = 2000
+
+// codeSearchMaxFileSize skips blobs larger than this (per the tree listing,
+// before any fetch) — almost certainly binary/vendor/generated content, not
+// worth the cost of fetching just to reject.
+const codeSearchMaxFileSize = 512 * 1024
+
+// codeSearchBinaryExts are skipped WITHOUT fetching — a cheap pre-filter for
+// obviously-binary content by extension, checked against the tree listing.
+var codeSearchBinaryExts = map[string]bool{
+	".png": true, ".jpg": true, ".jpeg": true, ".gif": true, ".ico": true, ".webp": true, ".bmp": true,
+	".pdf": true, ".zip": true, ".tar": true, ".gz": true, ".bz2": true, ".xz": true, ".7z": true,
+	".exe": true, ".dll": true, ".so": true, ".dylib": true, ".bin": true, ".class": true, ".jar": true,
+	".woff": true, ".woff2": true, ".ttf": true, ".eot": true, ".otf": true,
+	".mp3": true, ".mp4": true, ".mov": true, ".avi": true, ".webm": true,
+	".pyc": true, ".o": true, ".a": true,
 }
 
+// SearchCode does a client-side "git grep"-equivalent search. Gitea's REST API
+// has no code-content-search endpoint — confirmed against a live 1.25.5
+// instance's swagger spec (only /repos/search, /repos/issues/search,
+// /topics/search etc exist). The web UI's OWN code search falls back to
+// server-side `git grep` because no Repository Indexer is enabled on that
+// instance, and that fallback is an HTML-only route, not JSON API. So this
+// walks the tree, fetches text-like blobs (bounded by codeSearchMaxFiles /
+// codeSearchMaxFileSize), and substring-matches q — case-insensitive, literal
+// (not a regex, to keep behavior predictable and avoid a ReDoS surface from
+// user-supplied input) — against file contents.
+//
+// Pagination is over the FULL sorted result set, recomputed on every call —
+// there is no server-side index to page through incrementally, so requesting
+// page 2 re-scans the tree. Acceptable for the repo sizes this targets; a real
+// indexer (bleve/elasticsearch) enabled server-side would be the long-term
+// fix, and is an infra decision, not something gitea-mcp controls.
 func (c *Client) SearchCode(ctx context.Context, owner, repo, q string, page, limit int) ([]CodeSearchHit, error) {
+	if q == "" {
+		return nil, fmt.Errorf("q is required: %w", ErrValidation)
+	}
 	if page < 1 {
 		page = 1
 	}
 	if limit < 1 {
 		limit = 30
 	}
-	path := fmt.Sprintf("/api/v1/repos/%s/%s/search?q=%s&type=code&page=%d&limit=%d",
-		owner, repo, url.QueryEscape(q), page, limit)
-	body, status, err := c.GetJSON(ctx, path)
+
+	r, err := c.GetRepo(ctx, owner, repo)
 	if err != nil {
-		return nil, err
+		return nil, fmt.Errorf("resolve repo: %w", err)
 	}
-	if err := MapStatus(status, body); err != nil {
-		return nil, err
+	branch := r.DefaultBranch
+	if branch == "" {
+		branch = "main"
 	}
-	var env codeSearchEnvelope
-	if err := json.Unmarshal(body, &env); err != nil {
-		return nil, err
+
+	tree, err := c.GetTree(ctx, owner, repo, branch, true)
+	if err != nil {
+		return nil, fmt.Errorf("tree walk: %w", err)
 	}
-	return env.Data, nil
+
+	qLower := strings.ToLower(q)
+	all := make([]CodeSearchHit, 0)
+	scanned := 0
+	for _, e := range tree.Tree {
+		if ctx.Err() != nil {
+			break
+		}
+		if e.Type != "blob" {
+			continue
+		}
+		if codeSearchBinaryExts[strings.ToLower(path.Ext(e.Path))] {
+			continue
+		}
+		if e.Size > codeSearchMaxFileSize {
+			continue
+		}
+		if scanned >= codeSearchMaxFiles {
+			break
+		}
+		scanned++
+
+		fc, ferr := c.GetFileContents(ctx, owner, repo, e.Path, branch)
+		if ferr != nil {
+			continue // vanished/unreadable between tree walk and read — skip, don't fail the whole search
+		}
+		decoded, derr := base64.StdEncoding.DecodeString(fc.Content)
+		if derr != nil {
+			continue
+		}
+		if bytes.IndexByte(decoded, 0) >= 0 {
+			continue // binary content the extension filter missed
+		}
+
+		content := string(decoded)
+		contentLower := strings.ToLower(content)
+		count := strings.Count(contentLower, qLower)
+		if count == 0 {
+			continue
+		}
+
+		idx := strings.Index(contentLower, qLower)
+		all = append(all, CodeSearchHit{
+			Path:    e.Path,
+			Snippet: codeSearchSnippet(content, idx, len(q)),
+			HTMLURL: fmt.Sprintf("%s/%s/%s/src/branch/%s/%s", c.baseURL, owner, repo, branch, e.Path),
+			Score:   float64(count),
+		})
+	}
+
+	sort.Slice(all, func(i, j int) bool {
+		if all[i].Score != all[j].Score {
+			return all[i].Score > all[j].Score
+		}
+		return all[i].Path < all[j].Path
+	})
+
+	start := (page - 1) * limit
+	if start >= len(all) {
+		return []CodeSearchHit{}, nil
+	}
+	end := start + limit
+	if end > len(all) {
+		end = len(all)
+	}
+	return all[start:end], nil
+}
+
+// codeSearchSnippet returns a short window of text centered on a match,
+// trimmed to a single line-ish window so results read like a grep hit rather
+// than a content dump.
+func codeSearchSnippet(content string, idx, matchLen int) string {
+	const window = 60
+	start := idx - window
+	if start < 0 {
+		start = 0
+	}
+	end := idx + matchLen + window
+	if end > len(content) {
+		end = len(content)
+	}
+	snippet := strings.ReplaceAll(content[start:end], "\n", " ")
+	return strings.TrimSpace(snippet)
 }