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")
}