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_test.go

@@ -2,8 +2,12 @@ package gitea_test
 
 import (
 	"context"
+	"encoding/base64"
+	"errors"
+	"fmt"
 	"net/http"
 	"net/http/httptest"
+	"strings"
 	"testing"
 
 	"git.d-ma.be/mathias/gitea-mcp/internal/gitea"
@@ -11,22 +15,65 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
-func TestSearchCode(t *testing.T) {
-	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		assert.Equal(t, "/api/v1/repos/mathias/infra/search", r.URL.Path)
-		assert.Equal(t, "SearchCode", r.URL.Query().Get("q"))
-		assert.Equal(t, "code", r.URL.Query().Get("type"))
+func b64(s string) string { return base64.StdEncoding.EncodeToString([]byte(s)) }
+
+// codeSearchFake serves GetRepo + GetTree + GetFileContents off an in-memory
+// file map — the REAL endpoints SearchCode uses now that 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 etc exist — the web
+// UI's own code search falls back to server-side `git grep`, an HTML-only
+// route, not JSON API). Records which paths were actually fetched, so tests
+// can assert a file was SKIPPED (binary ext, oversized) without ever being
+// read, not just absent from results.
+type codeSearchFake struct {
+	files   map[string]string // path -> content
+	sizes   map[string]int64  // path -> tree-entry size (defaults to len(content))
+	fetched []string
+}
+
+func (f *codeSearchFake) handler(t *testing.T, owner, repo, branch string) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
 		w.Header().Set("Content-Type", "application/json")
-		_, _ = w.Write([]byte(`{
-			"data":[{
-				"path":"internal/gitea/code_search.go",
-				"snippet":"func (c *Client) SearchCode",
-				"html_url":"http://gitea.example.com/mathias/infra/src/branch/main/internal/gitea/code_search.go",
-				"score":2.5
-			}],
-			"ok":true
-		}`))
-	}))
+		p := r.URL.Path
+		switch {
+		case r.Method == http.MethodGet && p == "/api/v1/repos/"+owner+"/"+repo:
+			_, _ = fmt.Fprintf(w, `{"name":%q,"full_name":"%s/%s","default_branch":%q}`, repo, owner, repo, branch)
+
+		case r.Method == http.MethodGet && strings.HasPrefix(p, "/api/v1/repos/"+owner+"/"+repo+"/git/trees/"):
+			var entries []string
+			for path, content := range f.files {
+				size := int64(len(content))
+				if s, ok := f.sizes[path]; ok {
+					size = s
+				}
+				entries = append(entries, fmt.Sprintf(`{"path":%q,"type":"blob","sha":"s","size":%d}`, path, size))
+			}
+			_, _ = fmt.Fprintf(w, `{"sha":"root","tree":[%s],"truncated":false}`, strings.Join(entries, ","))
+
+		case r.Method == http.MethodGet && strings.HasPrefix(p, "/api/v1/repos/"+owner+"/"+repo+"/contents/"):
+			path := strings.TrimPrefix(p, "/api/v1/repos/"+owner+"/"+repo+"/contents/")
+			f.fetched = append(f.fetched, path)
+			content, ok := f.files[path]
+			if !ok {
+				w.WriteHeader(http.StatusNotFound)
+				_, _ = w.Write([]byte(`{"message":"not found"}`))
+				return
+			}
+			_, _ = fmt.Fprintf(w, `{"path":%q,"sha":"s","size":%d,"content":%q,"encoding":"base64"}`, path, len(content), b64(content))
+
+		default:
+			t.Errorf("unexpected request: %s %s", r.Method, p)
+			w.WriteHeader(http.StatusNotFound)
+		}
+	}
+}
+
+func TestSearchCode_FindsMatchInTree(t *testing.T) {
+	f := &codeSearchFake{files: map[string]string{
+		"internal/gitea/code_search.go": "func (c *Client) SearchCode(ctx context.Context) {}\n",
+		"internal/gitea/repos.go":       "func (c *Client) ListRepos() {}\n",
+	}}
+	srv := httptest.NewServer(f.handler(t, "mathias", "infra", "main"))
 	defer srv.Close()
 
 	c := gitea.NewClient(srv.URL, "tok")
@@ -34,6 +81,92 @@ func TestSearchCode(t *testing.T) {
 	require.NoError(t, err)
 	require.Len(t, hits, 1)
 	assert.Equal(t, "internal/gitea/code_search.go", hits[0].Path)
-	assert.Equal(t, "func (c *Client) SearchCode", hits[0].Snippet)
-	assert.InDelta(t, 2.5, hits[0].Score, 0.001)
+	assert.Contains(t, hits[0].Snippet, "SearchCode")
+	assert.Contains(t, hits[0].HTMLURL, "internal/gitea/code_search.go")
+	assert.Equal(t, 1.0, hits[0].Score)
+}
+
+func TestSearchCode_CaseInsensitive(t *testing.T) {
+	f := &codeSearchFake{files: map[string]string{
+		"README.md": "# MyProject\n\nBuild instructions here.\n",
+	}}
+	srv := httptest.NewServer(f.handler(t, "mathias", "infra", "main"))
+	defer srv.Close()
+
+	c := gitea.NewClient(srv.URL, "tok")
+	hits, err := c.SearchCode(context.Background(), "mathias", "infra", "myproject", 1, 30)
+	require.NoError(t, err)
+	require.Len(t, hits, 1)
+}
+
+func TestSearchCode_SkipsBinaryExtensionWithoutFetching(t *testing.T) {
+	f := &codeSearchFake{files: map[string]string{
+		"assets/logo.png": "SearchCode", // would match if fetched — must not be
+		"main.go":         "package main\n",
+	}}
+	srv := httptest.NewServer(f.handler(t, "mathias", "infra", "main"))
+	defer srv.Close()
+
+	c := gitea.NewClient(srv.URL, "tok")
+	hits, err := c.SearchCode(context.Background(), "mathias", "infra", "SearchCode", 1, 30)
+	require.NoError(t, err)
+	assert.Empty(t, hits)
+	assert.NotContains(t, f.fetched, "assets/logo.png", "binary extension must be skipped before fetch")
+}
+
+func TestSearchCode_SkipsOversizedFileWithoutFetching(t *testing.T) {
+	f := &codeSearchFake{
+		files: map[string]string{"vendor/bundle.txt": "SearchCode"},
+		sizes: map[string]int64{"vendor/bundle.txt": 10 * 1024 * 1024}, // 10MB per the tree listing
+	}
+	srv := httptest.NewServer(f.handler(t, "mathias", "infra", "main"))
+	defer srv.Close()
+
+	c := gitea.NewClient(srv.URL, "tok")
+	hits, err := c.SearchCode(context.Background(), "mathias", "infra", "SearchCode", 1, 30)
+	require.NoError(t, err)
+	assert.Empty(t, hits)
+	assert.NotContains(t, f.fetched, "vendor/bundle.txt", "oversized file must be skipped before fetch")
+}
+
+func TestSearchCode_SkipsBinaryContentNullByte(t *testing.T) {
+	f := &codeSearchFake{files: map[string]string{
+		"data.bin": "SearchCode\x00binary-marker",
+	}}
+	srv := httptest.NewServer(f.handler(t, "mathias", "infra", "main"))
+	defer srv.Close()
+
+	c := gitea.NewClient(srv.URL, "tok")
+	hits, err := c.SearchCode(context.Background(), "mathias", "infra", "SearchCode", 1, 30)
+	require.NoError(t, err)
+	assert.Empty(t, hits, "content with a null byte must be treated as binary even past the extension filter")
+}
+
+func TestSearchCode_Pagination(t *testing.T) {
+	files := map[string]string{}
+	for i := 0; i < 5; i++ {
+		files[fmt.Sprintf("file%d.go", i)] = strings.Repeat("hit ", i+1) // increasing occurrence count => increasing score
+	}
+	f := &codeSearchFake{files: files}
+	srv := httptest.NewServer(f.handler(t, "mathias", "infra", "main"))
+	defer srv.Close()
+
+	c := gitea.NewClient(srv.URL, "tok")
+	page1, err := c.SearchCode(context.Background(), "mathias", "infra", "hit", 1, 2)
+	require.NoError(t, err)
+	require.Len(t, page1, 2)
+	page2, err := c.SearchCode(context.Background(), "mathias", "infra", "hit", 2, 2)
+	require.NoError(t, err)
+	require.Len(t, page2, 2)
+
+	assert.NotEqual(t, page1[0].Path, page2[0].Path, "pages must not overlap")
+	assert.True(t, page1[0].Score >= page1[1].Score, "page1 sorted desc by score")
+	assert.True(t, page1[1].Score >= page2[0].Score, "page1's worst must rank >= page2's best")
+}
+
+func TestSearchCode_EmptyQueryErrors(t *testing.T) {
+	c := gitea.NewClient("http://unused", "tok")
+	_, err := c.SearchCode(context.Background(), "mathias", "infra", "", 1, 30)
+	require.Error(t, err)
+	assert.True(t, errors.Is(err, gitea.ErrValidation))
 }