feat(persona): add Persona definition, system prompt assembly, and AgentsMD discovery

pkg/persona/loader.go

@@ -0,0 +1,42 @@
+package persona
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"path/filepath"
+
+	"gopkg.in/yaml.v3"
+)
+
+// yamlLoader loads personas from YAML files.
+type yamlLoader struct{}
+
+// NewYAMLLoader returns a Loader that reads from YAML files.
+func NewYAMLLoader() Loader {
+	return &yamlLoader{}
+}
+
+func (l *yamlLoader) Load(ctx context.Context, configPath string) (Persona, error) {
+	data, err := os.ReadFile(configPath)
+	if err != nil {
+		return Persona{}, fmt.Errorf("reading persona file: %w", err)
+	}
+
+	var p Persona
+	if err := yaml.Unmarshal(data, &p); err != nil {
+		return Persona{}, fmt.Errorf("parsing YAML: %w", err)
+	}
+	return p, nil
+}
+
+func (l *yamlLoader) Discover(ctx context.Context, workdir string) (Persona, error) {
+	// Try to load from workdir
+	path := filepath.Join(workdir, "persona.yaml")
+	if _, err := os.Stat(path); err == nil {
+		return l.Load(ctx, path)
+	}
+
+	// Return default if no persona file found
+	return DefaultPersona(), nil
+}

pkg/persona/persona.go

@@ -0,0 +1,109 @@
+package persona
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+
+	"github.com/VictorVargas/rony-llm-agent/pkg/llm"
+)
+
+// Persona defines the personality and behavior of the agent.
+type Persona struct {
+	ID          string
+	Name        string
+	Tone        string
+	Style       string
+	Language    string
+	Constraints []string
+	FewShot   []llm.Message
+}
+
+// Loader loads personas from files.
+type Loader interface {
+	Load(ctx context.Context, configPath string) (Persona, error)
+	Discover(ctx context.Context, workdir string) (Persona, error)
+}
+
+// ErrPersonaNotFound is returned when a persona file is not found.
+var ErrPersonaNotFound = fmt.Errorf("persona not found")
+
+// DefaultPersona returns a basic persona with sensible defaults.
+func DefaultPersona() Persona {
+	return Persona{
+		ID:       "default",
+		Name:     "Rony",
+		Tone:     "professional and helpful",
+		Style:    "clear and concise",
+		Language: "en",
+	}
+}
+
+// AssembleSystemPrompt builds the final system prompt from persona, base prompt, and AGENTS.md.
+func AssembleSystemPrompt(p Persona, agentsMD string) string {
+	var parts []string
+
+	// Base system prompt
+	parts = append(parts, "You are an AI agent. Be helpful, accurate, and safe.")
+
+	// Persona instructions
+	if p.Name != "" {
+		parts = append(parts, fmt.Sprintf("Your name is %s.", p.Name))
+	}
+	if p.Tone != "" {
+		parts = append(parts, fmt.Sprintf("Use a %s tone.", p.Tone))
+	}
+	if p.Style != "" {
+		parts = append(parts, fmt.Sprintf("Write in a %s style.", p.Style))
+	}
+	if p.Language != "" {
+		parts = append(parts, fmt.Sprintf("Respond in %s.", p.Language))
+	}
+	for _, c := range p.Constraints {
+		parts = append(parts, fmt.Sprintf("CONSTRAINT: %s", c))
+	}
+
+	// AGENTS.md content
+	if agentsMD != "" {
+		parts = append(parts, "---")
+		parts = append(parts, "Project instructions:")
+		parts = append(parts, agentsMD)
+	}
+
+	return strings.Join(parts, "\n\n")
+}
+
+// discoverAgentsMD walks up the directory tree looking for AGENTS.md files.
+func discoverAgentsMD(root string) string {
+	var parts []string
+	current := root
+
+	for {
+		agentsPath := filepath.Join(current, "AGENTS.md")
+		if _, err := os.Stat(agentsPath); err == nil {
+			data, err := os.ReadFile(agentsPath)
+			if err == nil {
+				parts = append(parts, string(data))
+			}
+		}
+
+		parent := filepath.Dir(current)
+		if parent == current || parent == "." {
+			break
+		}
+		current = parent
+	}
+
+	// Also check ~/.config/rony/AGENTS.md
+	home, err := os.UserHomeDir()
+	if err == nil {
+		globalPath := filepath.Join(home, ".config", "rony", "AGENTS.md")
+		if data, err := os.ReadFile(globalPath); err == nil {
+			parts = append(parts, string(data))
+		}
+	}
+
+	return strings.Join(parts, "\n\n")
+}

pkg/persona/persona_test.go

@@ -0,0 +1,68 @@
+package persona
+
+import (
+	"context"
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func TestDefaultPersona(t *testing.T) {
+	p := DefaultPersona()
+	if p.Name != "Rony" {
+		t.Errorf("expected name 'Rony', got %q", p.Name)
+	}
+	if p.Tone != "professional and helpful" {
+		t.Errorf("expected tone 'professional and helpful', got %q", p.Tone)
+	}
+}
+
+func TestAssembleSystemPrompt(t *testing.T) {
+	p := Persona{
+		Name: "TestAgent",
+		Tone: "friendly",
+	}
+	result := AssembleSystemPrompt(p, "")
+	if !contains(result, "TestAgent") {
+		t.Error("expected system prompt to contain persona name")
+	}
+	if !contains(result, "friendly") {
+		t.Error("expected system prompt to contain tone")
+	}
+}
+
+func TestAssembleSystemPrompt_WithAgentsMD(t *testing.T) {
+	p := DefaultPersona()
+	agentsMD := "This is the project instructions."
+	result := AssembleSystemPrompt(p, agentsMD)
+	if !contains(result, agentsMD) {
+		t.Error("expected system prompt to contain AGENTS.md content")
+	}
+}
+
+func TestDiscoverAgentsMD(t *testing.T) {
+	tmpDir := t.TempDir()
+	agentsPath := filepath.Join(tmpDir, "AGENTS.md")
+	os.WriteFile(agentsPath, []byte("test instructions"), 0644)
+
+	result := discoverAgentsMD(tmpDir)
+	if !contains(result, "test instructions") {
+		t.Error("expected discoverAgentsMD to find AGENTS.md")
+	}
+}
+
+func TestLoader_Discover_NoFile(t *testing.T) {
+	loader := NewYAMLLoader()
+	ctx := context.Background()
+	p, err := loader.Discover(ctx, "/tmp/nonexistent_12345")
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if p.Name != "Rony" {
+		t.Errorf("expected default persona, got %q", p.Name)
+	}
+}
+
+func contains(haystack, needle string) bool {
+	return len(haystack) > 0 && len(needle) > 0 && len(haystack) >= len(needle) && haystack[:len(needle)] == needle || len(haystack) > len(needle) && contains(haystack[1:], needle)
+}