feat: add classify types and token-to-domain mapper

Co-Authored-By: Virgil <virgil@lethean.io>
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

classify.go

@@ -0,0 +1,79 @@
+package i18n
+
+import (
+	"context"
+	"io"
+	"strings"
+	"time"
+
+	"forge.lthn.ai/core/go-inference"
+)
+
+// ClassifyStats reports metrics from a ClassifyCorpus run.
+type ClassifyStats struct {
+	Total         int
+	Skipped       int            // malformed or missing prompt field
+	ByDomain      map[string]int // domain_1b label -> count
+	Duration      time.Duration
+	PromptsPerSec float64
+}
+
+// ClassifyOption configures ClassifyCorpus behaviour.
+type ClassifyOption func(*classifyConfig)
+
+type classifyConfig struct {
+	batchSize      int
+	promptField    string
+	promptTemplate string
+}
+
+func defaultClassifyConfig() classifyConfig {
+	return classifyConfig{
+		batchSize:      8,
+		promptField:    "prompt",
+		promptTemplate: "Classify this text into exactly one category: technical, creative, ethical, casual.\n\nText: %s\n\nCategory:",
+	}
+}
+
+// WithBatchSize sets the number of prompts per Classify call. Default 8.
+func WithBatchSize(n int) ClassifyOption {
+	return func(c *classifyConfig) { c.batchSize = n }
+}
+
+// WithPromptField sets which JSONL field contains the text to classify. Default "prompt".
+func WithPromptField(field string) ClassifyOption {
+	return func(c *classifyConfig) { c.promptField = field }
+}
+
+// WithPromptTemplate sets the classification prompt. Use %s for the text placeholder.
+func WithPromptTemplate(tmpl string) ClassifyOption {
+	return func(c *classifyConfig) { c.promptTemplate = tmpl }
+}
+
+// mapTokenToDomain maps a model output token to a 4-way domain label.
+func mapTokenToDomain(token string) string {
+	if len(token) == 0 {
+		return "unknown"
+	}
+	lower := strings.ToLower(token)
+	switch {
+	case strings.HasPrefix(lower, "tech"):
+		return "technical"
+	case strings.HasPrefix(lower, "cre"):
+		return "creative"
+	case strings.HasPrefix(lower, "eth"):
+		return "ethical"
+	case strings.HasPrefix(lower, "cas"):
+		return "casual"
+	default:
+		return "unknown"
+	}
+}
+
+// Ensure imports are used (ClassifyCorpus will be added in Task 3).
+var (
+	_ = (*inference.Token)(nil)
+	_ context.Context
+	_ io.Reader
+	_ time.Duration
+)

classify_test.go

@@ -0,0 +1,34 @@
+package i18n
+
+import "testing"
+
+func TestMapTokenToDomain(t *testing.T) {
+	tests := []struct {
+		token string
+		want  string
+	}{
+		{"technical", "technical"},
+		{"Technical", "technical"},
+		{"tech", "technical"},
+		{"creative", "creative"},
+		{"Creative", "creative"},
+		{"cre", "creative"},
+		{"ethical", "ethical"},
+		{"Ethical", "ethical"},
+		{"eth", "ethical"},
+		{"casual", "casual"},
+		{"Casual", "casual"},
+		{"cas", "casual"},
+		{"unknown", "unknown"},
+		{"", "unknown"},
+		{"foo", "unknown"},
+	}
+	for _, tt := range tests {
+		t.Run(tt.token, func(t *testing.T) {
+			got := mapTokenToDomain(tt.token)
+			if got != tt.want {
+				t.Errorf("mapTokenToDomain(%q) = %q, want %q", tt.token, got, tt.want)
+			}
+		})
+	}
+}

go.mod

@@ -4,4 +4,6 @@ go 1.25.5
 
 require golang.org/x/text v0.33.0
 
+require forge.lthn.ai/core/go-inference v0.0.0-20260219234405-c61ec9f5c724 // indirect
+
 replace forge.lthn.ai/core/go-inference => ../go-inference