feat(labels): add label_list + issue_label tools (#52)

Closes #52 — unblocks parallax#3 dispatch labeling, which needs to both
discover a repo's label set and attach labels to an issue by name (the
CAD pipeline doesn't track Gitea's internal numeric label IDs).

- gitea.Client: ListLabels, AddIssueLabels (additive POST, matches
  Gitea's own semantics — no delete-then-post needed); extend the
  existing Label struct with Color for label_list's output.
- tools.LabelList (read-only, allowlisted): lists a repo's labels.
- tools.IssueLabel (allowlisted): resolves label names to IDs via
  ListLabels, so callers pass names (the primary interface) instead of
  hunting for numeric IDs; also accepts label_ids for callers that
  already have them. An unknown name fails closed, naming exactly which
  label wasn't found.
- Bump TestRegisteredToolCount 39 -> 41 in the same commit (this
  project was bitten today by a locked count going stale silently).

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

internal/tools/issue_label.go

@@ -0,0 +1,87 @@
+package tools
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+
+	"git.d-ma.be/mathias/gitea-mcp/internal/allowlist"
+	"git.d-ma.be/mathias/gitea-mcp/internal/gitea"
+	"git.d-ma.be/mathias/gitea-mcp/internal/registry"
+)
+
+type IssueLabel struct {
+	c *gitea.Client
+	a *allowlist.Allowlist
+}
+
+func NewIssueLabel(c *gitea.Client, a *allowlist.Allowlist) *IssueLabel {
+	return &IssueLabel{c: c, a: a}
+}
+
+func (t *IssueLabel) Descriptor() registry.ToolDescriptor {
+	return registry.ToolDescriptor{
+		Name:        "issue_label",
+		Description: "Add labels to an issue or pull request. Resolves label names to IDs via the repo's label list. Additive — existing labels are left in place.",
+		InputSchema: json.RawMessage(`{
+			"type":"object",
+			"properties":{
+				"owner":{"type":"string"},
+				"repo":{"type":"string"},
+				"number":{"type":"integer","minimum":1},
+				"labels":{"type":"array","items":{"type":"string"}},
+				"label_ids":{"type":"array","items":{"type":"integer"}}
+			},
+			"required":["owner","repo","number","labels"]
+		}`),
+	}
+}
+
+type issueLabelArgs struct {
+	Owner    string   `json:"owner"`
+	Repo     string   `json:"repo"`
+	Number   int      `json:"number"`
+	Labels   []string `json:"labels,omitempty"`
+	LabelIDs []int64  `json:"label_ids,omitempty"`
+}
+
+func (t *IssueLabel) Call(ctx context.Context, raw json.RawMessage) (json.RawMessage, error) {
+	var args issueLabelArgs
+	if err := parseArgs(raw, &args); err != nil {
+		return nil, err
+	}
+	if err := t.a.Check(args.Owner); err != nil {
+		return nil, err
+	}
+	if args.Number < 1 {
+		return nil, fmt.Errorf("number must be >= 1: %w", gitea.ErrValidation)
+	}
+	if len(args.Labels) == 0 && len(args.LabelIDs) == 0 {
+		return nil, fmt.Errorf("labels is required: %w", gitea.ErrValidation)
+	}
+
+	ids := append([]int64{}, args.LabelIDs...)
+	if len(args.Labels) > 0 {
+		existing, err := t.c.ListLabels(ctx, args.Owner, args.Repo)
+		if err != nil {
+			return nil, err
+		}
+		byName := make(map[string]int64, len(existing))
+		for _, l := range existing {
+			byName[l.Name] = l.ID
+		}
+		for _, name := range args.Labels {
+			id, ok := byName[name]
+			if !ok {
+				return nil, fmt.Errorf("label %q not found in %s/%s: %w", name, args.Owner, args.Repo, gitea.ErrValidation)
+			}
+			ids = append(ids, id)
+		}
+	}
+
+	labels, err := t.c.AddIssueLabels(ctx, args.Owner, args.Repo, args.Number, ids)
+	if err != nil {
+		return nil, err
+	}
+	return textOK(labels)
+}

internal/tools/issue_label_test.go

@@ -0,0 +1,82 @@
+package tools_test
+
+import (
+	"context"
+	"encoding/json"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"git.d-ma.be/mathias/gitea-mcp/internal/allowlist"
+	"git.d-ma.be/mathias/gitea-mcp/internal/gitea"
+	"git.d-ma.be/mathias/gitea-mcp/internal/tools"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+const labelListFixture = `[
+	{"id":1,"name":"bug","color":"ee0701"},
+	{"id":2,"name":"enhancement","color":"84b6eb"}
+]`
+
+func TestIssueLabelAppliesByName(t *testing.T) {
+	var captured []byte
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		switch {
+		case r.Method == http.MethodGet && r.URL.Path == "/api/v1/repos/o/r/labels":
+			w.Header().Set("Content-Type", "application/json")
+			_, _ = w.Write([]byte(labelListFixture))
+		case r.Method == http.MethodPost && r.URL.Path == "/api/v1/repos/o/r/issues/42/labels":
+			var err error
+			captured, err = io.ReadAll(r.Body)
+			require.NoError(t, err)
+			w.Header().Set("Content-Type", "application/json")
+			_, _ = w.Write([]byte(labelListFixture))
+		default:
+			t.Fatalf("unexpected request: %s %s", r.Method, r.URL.Path)
+		}
+	}))
+	defer srv.Close()
+
+	tool := tools.NewIssueLabel(gitea.NewClient(srv.URL, "tok"), allowlist.New([]string{"o"}))
+	out, err := tool.Call(context.Background(), json.RawMessage(`{"owner":"o","repo":"r","number":42,"labels":["bug","enhancement"]}`))
+	require.NoError(t, err)
+
+	var payload map[string]any
+	require.NoError(t, json.Unmarshal(captured, &payload))
+	ids, ok := payload["labels"].([]any)
+	require.True(t, ok)
+	assert.ElementsMatch(t, []any{float64(1), float64(2)}, ids)
+
+	assert.Contains(t, string(out), `"name":"bug"`)
+	assert.Contains(t, string(out), `"name":"enhancement"`)
+}
+
+func TestIssueLabelUnknownNameNamesTheMissingLabel(t *testing.T) {
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		_, _ = w.Write([]byte(labelListFixture))
+	}))
+	defer srv.Close()
+
+	tool := tools.NewIssueLabel(gitea.NewClient(srv.URL, "tok"), allowlist.New([]string{"o"}))
+	_, err := tool.Call(context.Background(), json.RawMessage(`{"owner":"o","repo":"r","number":42,"labels":["bug","does-not-exist"]}`))
+	require.Error(t, err)
+	assert.ErrorIs(t, err, gitea.ErrValidation)
+	assert.Contains(t, err.Error(), `"does-not-exist"`)
+	assert.Contains(t, err.Error(), "o/r")
+}
+
+func TestIssueLabelAllowlistRejects(t *testing.T) {
+	tool := tools.NewIssueLabel(gitea.NewClient("http://unused", ""), allowlist.New([]string{"allowed"}))
+	_, err := tool.Call(context.Background(), json.RawMessage(`{"owner":"evil","repo":"r","number":1,"labels":["bug"]}`))
+	require.Error(t, err)
+}
+
+func TestIssueLabelRequiresValidNumber(t *testing.T) {
+	tool := tools.NewIssueLabel(gitea.NewClient("http://unused", ""), allowlist.New([]string{"o"}))
+	_, err := tool.Call(context.Background(), json.RawMessage(`{"owner":"o","repo":"r","number":0,"labels":["bug"]}`))
+	require.Error(t, err)
+	assert.ErrorIs(t, err, gitea.ErrValidation)
+}

internal/tools/label_list.go

@@ -0,0 +1,54 @@
+package tools
+
+import (
+	"context"
+	"encoding/json"
+
+	"git.d-ma.be/mathias/gitea-mcp/internal/allowlist"
+	"git.d-ma.be/mathias/gitea-mcp/internal/gitea"
+	"git.d-ma.be/mathias/gitea-mcp/internal/registry"
+)
+
+type LabelList struct {
+	c *gitea.Client
+	a *allowlist.Allowlist
+}
+
+func NewLabelList(c *gitea.Client, a *allowlist.Allowlist) *LabelList {
+	return &LabelList{c: c, a: a}
+}
+
+func (t *LabelList) Descriptor() registry.ToolDescriptor {
+	return registry.ToolDescriptor{
+		Name:        "label_list",
+		Description: "List all labels defined on a repo. Returns id, name, and color for each label.",
+		InputSchema: json.RawMessage(`{
+			"type":"object",
+			"properties":{
+				"owner":{"type":"string"},
+				"repo":{"type":"string"}
+			},
+			"required":["owner","repo"]
+		}`),
+	}
+}
+
+type labelListArgs struct {
+	Owner string `json:"owner"`
+	Repo  string `json:"repo"`
+}
+
+func (t *LabelList) Call(ctx context.Context, raw json.RawMessage) (json.RawMessage, error) {
+	var args labelListArgs
+	if err := parseArgs(raw, &args); err != nil {
+		return nil, err
+	}
+	if err := t.a.Check(args.Owner); err != nil {
+		return nil, err
+	}
+	labels, err := t.c.ListLabels(ctx, args.Owner, args.Repo)
+	if err != nil {
+		return nil, err
+	}
+	return textOK(labels)
+}

internal/tools/label_list_test.go

@@ -0,0 +1,42 @@
+package tools_test
+
+import (
+	"context"
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"git.d-ma.be/mathias/gitea-mcp/internal/allowlist"
+	"git.d-ma.be/mathias/gitea-mcp/internal/gitea"
+	"git.d-ma.be/mathias/gitea-mcp/internal/tools"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestLabelListTool(t *testing.T) {
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		assert.Equal(t, http.MethodGet, r.Method)
+		assert.Equal(t, "/api/v1/repos/mathias/infra/labels", r.URL.Path)
+		w.Header().Set("Content-Type", "application/json")
+		_, _ = w.Write([]byte(`[
+			{"id":1,"name":"bug","color":"ee0701"},
+			{"id":2,"name":"enhancement","color":"84b6eb"}
+		]`))
+	}))
+	defer srv.Close()
+
+	tool := tools.NewLabelList(gitea.NewClient(srv.URL, "tok"), allowlist.New([]string{"mathias"}))
+	out, err := tool.Call(context.Background(), json.RawMessage(`{"owner":"mathias","repo":"infra"}`))
+	require.NoError(t, err)
+	assert.Contains(t, string(out), `"id":1`)
+	assert.Contains(t, string(out), `"name":"bug"`)
+	assert.Contains(t, string(out), `"color":"ee0701"`)
+	assert.Contains(t, string(out), `"name":"enhancement"`)
+}
+
+func TestLabelListAllowlistRejects(t *testing.T) {
+	tool := tools.NewLabelList(gitea.NewClient("http://unused", ""), allowlist.New([]string{"mathias"}))
+	_, err := tool.Call(context.Background(), json.RawMessage(`{"owner":"evil","repo":"x"}`))
+	require.Error(t, err)
+}

internal/tools/registry.go

@@ -54,6 +54,8 @@ func RegisterAll(
 	reg.Register(NewIssueListComments(c, a))
 	reg.Register(NewIssueClose(c, a))
 	reg.Register(NewIssueReopen(c, a))
+	reg.Register(NewLabelList(c, a))
+	reg.Register(NewIssueLabel(c, a))
 	reg.Register(NewWorkflowRunList(c, a))
 	reg.Register(NewReleaseCreate(c, a))
 	reg.Register(NewRepoDelete(c, a))

internal/tools/registry_test.go

@@ -54,5 +54,5 @@ func TestEveryRegisteredToolIsDispatchable(t *testing.T) {
 // Lock the tool count so an accidental drop of a registration in RegisterAll
 // (the single source main.go and this test share) fails loudly.
 func TestRegisteredToolCount(t *testing.T) {
-	assert.Len(t, buildRegistry().Tools(), 39)
+	assert.Len(t, buildRegistry().Tools(), 41)
 }